Update to 5.4.2

2024-11-22 05:04:35 +00:00 · 2021-03-10 20:46:07 +00:00 · 2021-03-10 20:46:07 +00:00 · 95f31eafc0
commit 95f31eafc0
parent 619231f297
79 changed files with 1081 additions and 838 deletions
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@ -1,5 +1,5 @@
 cmake_minimum_required(VERSION 3.1)
-project(lua LANGUAGES C VERSION 5.4.0)
+project(lua LANGUAGES C VERSION 5.4.2)

 option(LUA_SUPPORT_DL "Support dynamic loading of compiled modules" OFF)

@ -18,4 +18,4 @@ else()
 endif()


-add_subdirectory(lua-5.4.0)
+add_subdirectory(lua-5.4.2)
--- a/lua-5.4.2/CMakeLists.txt
+++ b/lua-5.4.2/CMakeLists.txt
@ -43,7 +43,7 @@ if(UNIX)
        find_library(LIBM m)
        #TODO: Redo this with find_package
        if(NOT LIBM)
-            message(FATAL_ERROR "libm not found and requred by lua")
+            message(FATAL_ERROR "libm not found and is required by lua")
        endif()
        target_link_libraries(lua_static INTERFACE ${LIBM})

--- a/lua-5.4.2/Makefile
+++ b/lua-5.4.2/Makefile
@ -46,7 +46,7 @@ TO_MAN= lua.1 luac.1

 # Lua version and release.
 V= 5.4
-R= $V.0
+R= $V.2

 # Targets start here.
 all:	$(PLAT)
--- a/lua-5.4.2/README
+++ b/lua-5.4.2/README
@ -1,5 +1,5 @@

-This is Lua 5.4.0, released on 18 Jun 2020.
+This is Lua 5.4.2, released on 13 Nov 2020.

 For installation instructions, license details, and
 further information about Lua, see doc/readme.html.
--- a/lua-5.4.2/doc/contents.html
+++ b/lua-5.4.2/doc/contents.html
@ -95,6 +95,7 @@ Freely available under the terms of the
 <UL>
 <LI><A HREF="manual.html#4.1.1">4.1.1 &ndash; Stack Size</A>
 <LI><A HREF="manual.html#4.1.2">4.1.2 &ndash; Valid and Acceptable Indices</A>
+<LI><A HREF="manual.html#4.1.3">4.1.3 &ndash; Pointers to strings</A>
 </UL>
 <LI><A HREF="manual.html#4.2">4.2 &ndash; C Closures</A>
 <LI><A HREF="manual.html#4.3">4.3 &ndash; Registry</A>
@ -197,7 +198,6 @@ Freely available under the terms of the
 <A HREF="manual.html#pdf-debug.getregistry">debug.getregistry</A><BR>
 <A HREF="manual.html#pdf-debug.getupvalue">debug.getupvalue</A><BR>
 <A HREF="manual.html#pdf-debug.getuservalue">debug.getuservalue</A><BR>
-<A HREF="manual.html#pdf-debug.setcstacklimit">debug.setcstacklimit</A><BR>
 <A HREF="manual.html#pdf-debug.sethook">debug.sethook</A><BR>
 <A HREF="manual.html#pdf-debug.setlocal">debug.setlocal</A><BR>
 <A HREF="manual.html#pdf-debug.setmetatable">debug.setmetatable</A><BR>
@ -475,7 +475,6 @@ Freely available under the terms of the
 <A HREF="manual.html#lua_resume">lua_resume</A><BR>
 <A HREF="manual.html#lua_rotate">lua_rotate</A><BR>
 <A HREF="manual.html#lua_setallocf">lua_setallocf</A><BR>
-<A HREF="manual.html#lua_setcstacklimit">lua_setcstacklimit</A><BR>
 <A HREF="manual.html#lua_setfield">lua_setfield</A><BR>
 <A HREF="manual.html#lua_setglobal">lua_setglobal</A><BR>
 <A HREF="manual.html#lua_sethook">lua_sethook</A><BR>
@ -664,10 +663,10 @@ Freely available under the terms of the

 <P CLASS="footer">
 Last update:
-Sat May 30 08:22:18 -03 2020
+Tue Nov 10 20:58:52 UTC 2020
 </P>
 <!--
-Last change: revised for Lua 5.4.0 (final)
+Last change: revised for Lua 5.4.2
 -->

 </BODY>
--- a/lua-5.4.2/doc/index.css
+++ b/lua-5.4.2/doc/index.css
--- a/lua-5.4.2/doc/logo.gif
+++ b/lua-5.4.2/doc/logo.gif
--- a/lua-5.4.2/doc/lua.1
+++ b/lua-5.4.2/doc/lua.1
--- a/lua-5.4.2/doc/lua.css
+++ b/lua-5.4.2/doc/lua.css
--- a/lua-5.4.2/doc/luac.1
+++ b/lua-5.4.2/doc/luac.1
--- a/lua-5.4.2/doc/manual.css
+++ b/lua-5.4.2/doc/manual.css
--- a/lua-5.4.2/doc/manual.html
+++ b/lua-5.4.2/doc/manual.html
@ -2966,26 +2966,31 @@ When you interact with the Lua API,
 you are responsible for ensuring consistency.
 In particular,
 <em>you are responsible for controlling stack overflow</em>.
-You can use the function <a href="#lua_checkstack"><code>lua_checkstack</code></a>
-to ensure that the stack has enough space for pushing new elements.
+When you call any API function,
+you must ensure the stack has enough room to accommodate the results.
+
+
+<p>
+There is one exception to the above rule:
+When you call a Lua function
+without a fixed number of results (see <a href="#lua_call"><code>lua_call</code></a>),
+Lua ensures that the stack has enough space for all results.
+However, it does not ensure any extra space.
+So, before pushing anything on the stack after such a call
+you should use <a href="#lua_checkstack"><code>lua_checkstack</code></a>.


 <p>
 Whenever Lua calls C,
 it ensures that the stack has space for
-at least <a name="pdf-LUA_MINSTACK"><code>LUA_MINSTACK</code></a> extra slots.
+at least <a name="pdf-LUA_MINSTACK"><code>LUA_MINSTACK</code></a> extra elements;
+that is, you can safely push up to <code>LUA_MINSTACK</code> values into it.
 <code>LUA_MINSTACK</code> is defined as 20,
 so that usually you do not have to worry about stack space
 unless your code has loops pushing elements onto the stack.
-
-
-<p>
-When you call a Lua function
-without a fixed number of results (see <a href="#lua_call"><code>lua_call</code></a>),
-Lua ensures that the stack has enough space for all results,
-but it does not ensure any extra space.
-So, before pushing anything in the stack after such a call
-you should use <a href="#lua_checkstack"><code>lua_checkstack</code></a>.
+Whenever necessary,
+you can use the function <a href="#lua_checkstack"><code>lua_checkstack</code></a>
+to ensure that the stack has enough space for pushing new elements.



@ -3044,6 +3049,49 @@ which behaves like a nil value.



+<h3>4.1.3 &ndash; <a name="4.1.3">Pointers to strings</a></h3>
+
+<p>
+Several functions in the API return pointers (<code>const char*</code>)
+to Lua strings in the stack.
+(See <a href="#lua_pushfstring"><code>lua_pushfstring</code></a>, <a href="#lua_pushlstring"><code>lua_pushlstring</code></a>,
+<a href="#lua_pushstring"><code>lua_pushstring</code></a>, and <a href="#lua_tolstring"><code>lua_tolstring</code></a>.
+See also <a href="#luaL_checklstring"><code>luaL_checklstring</code></a>, <a href="#luaL_checkstring"><code>luaL_checkstring</code></a>,
+and <a href="#luaL_tolstring"><code>luaL_tolstring</code></a> in the auxiliary library.)
+
+
+<p>
+In general,
+Lua's garbage collection can free or move internal memory
+and then invalidate pointers to internal strings.
+To allow a safe use of these pointers,
+The API guarantees that any pointer to a string in a stack index
+is valid while the string value at that index is not removed from the stack.
+(It can be moved to another index, though.)
+When the index is a pseudo-index (referring to an upvalue),
+the pointer is valid while the corresponding call is active and
+the corresponding upvalue is not modified.
+
+
+<p>
+Some functions in the debug interface
+also return pointers to strings,
+namely <a href="#lua_getlocal"><code>lua_getlocal</code></a>, <a href="#lua_getupvalue"><code>lua_getupvalue</code></a>,
+<a href="#lua_setlocal"><code>lua_setlocal</code></a>, and <a href="#lua_setupvalue"><code>lua_setupvalue</code></a>.
+For these functions, the pointer is guaranteed to
+be valid while the caller function is active and
+the given closure (if one was given) is in the stack.
+
+
+<p>
+Except for these guarantees,
+the garbage collector is free to invalidate
+any pointer to internal strings.
+
+
+
+
+


 <h2>4.2 &ndash; <a name="4.2">C Closures</a></h2>
@ -3239,7 +3287,7 @@ Therefore, if a C&nbsp;function <code>foo</code> calls an API function
 and this API function yields
 (directly or indirectly by calling another function that yields),
 Lua cannot return to <code>foo</code> any more,
-because the <code>longjmp</code> removes its frame from the C stack.
+because the <code>longjmp</code> removes its frame from the C&nbsp;stack.


 <p>
@ -3269,7 +3317,7 @@ After the thread resumes,
 it eventually will finish running the callee function.
 However,
 the callee function cannot return to the original function,
-because its frame in the C stack was destroyed by the yield.
+because its frame in the C&nbsp;stack was destroyed by the yield.
 Instead, Lua calls a <em>continuation function</em>,
 which was given as an argument to the callee function.
 As the name implies,
@ -3389,7 +3437,7 @@ depending on the situation;
 an interrogation mark '<code>?</code>' means that
 we cannot know how many elements the function pops/pushes
 by looking only at its arguments.
-(For instance, they may depend on what is on the stack.)
+(For instance, they may depend on what is in the stack.)
 The third field, <code>x</code>,
 tells whether the function may raise errors:
 '<code>-</code>' means the function never raises any error;
@ -3408,7 +3456,7 @@ and therefore may raise any errors.
 <p>
 Converts the acceptable index <code>idx</code>
 into an equivalent absolute index
-(that is, one that does not depend on the stack top).
+(that is, one that does not depend on the stack size).



@ -3678,7 +3726,7 @@ of numeric arguments and returns their average and their sum:
 <pre>int lua_checkstack (lua_State *L, int n);</pre>

 <p>
-Ensures that the stack has space for at least <code>n</code> extra slots,
+Ensures that the stack has space for at least <code>n</code> extra elements,
 that is, that you can safely push up to <code>n</code> values into it.
 It returns false if it cannot fulfill the request,
 either because it would cause the stack
@ -3686,7 +3734,7 @@ to be greater than a fixed maximum size
 (typically at least several thousand elements) or
 because it cannot allocate memory for the extra space.
 This function never shrinks the stack;
-if the stack already has space for the extra slots,
+if the stack already has space for the extra elements,
 it is left unchanged.


@ -4443,6 +4491,10 @@ plus an associated block of raw memory with <code>size</code> bytes.

 <p>
 The function returns the address of the block of memory.
+Lua ensures that this address is valid as long as
+the corresponding userdata is alive (see <a href="#2.5">&sect;2.5</a>).
+Moreover, if the userdata is marked for finalization (see <a href="#2.5.3">&sect;2.5.3</a>),
+its address is valid at least until the call to its finalizer.



@ -4600,13 +4652,18 @@ except that it allows the called function to yield (see <a href="#4.5">&sect;4.5


 <hr><h3><a name="lua_pop"><code>lua_pop</code></a></h3><p>
-<span class="apii">[-n, +0, &ndash;]</span>
+<span class="apii">[-n, +0, <em>e</em>]</span>
 <pre>void lua_pop (lua_State *L, int n);</pre>

 <p>
 Pops <code>n</code> elements from the stack.


+<p>
+This function can run arbitrary code when removing an index
+marked as to-be-closed from the stack.
+
+



@ -4688,7 +4745,7 @@ This function is equivalent to <a href="#lua_pushcclosure"><code>lua_pushcclosur

 <p>
 Pushes onto the stack a formatted string
-and returns a pointer to this string.
+and returns a pointer to this string (see <a href="#4.1.3">&sect;4.1.3</a>).
 It is similar to the ISO&nbsp;C function <code>sprintf</code>,
 but has two important differences.
 First,
@ -4788,7 +4845,7 @@ including embedded zeros.


 <p>
-Returns a pointer to the internal copy of the string.
+Returns a pointer to the internal copy of the string (see <a href="#4.1.3">&sect;4.1.3</a>).



@ -4829,7 +4886,7 @@ the function returns.


 <p>
-Returns a pointer to the internal copy of the string.
+Returns a pointer to the internal copy of the string (see <a href="#4.1.3">&sect;4.1.3</a>).


 <p>
@ -5273,7 +5330,7 @@ for the "newindex" event (see <a href="#2.4">&sect;2.4</a>).


 <hr><h3><a name="lua_settop"><code>lua_settop</code></a></h3><p>
-<span class="apii">[-?, +?, &ndash;]</span>
+<span class="apii">[-?, +?, <em>e</em>]</span>
 <pre>void lua_settop (lua_State *L, int index);</pre>

 <p>
@ -5284,6 +5341,11 @@ then the new elements are filled with <b>nil</b>.
 If <code>index</code> is&nbsp;0, then all stack elements are removed.


+<p>
+This function can run arbitrary code when removing an index
+marked as to-be-closed from the stack.
+
+



@ -5399,7 +5461,7 @@ otherwise, returns <code>NULL</code>.


 <hr><h3><a name="lua_toclose"><code>lua_toclose</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
+<span class="apii">[-0, +0, <em>m</em>]</span>
 <pre>void lua_toclose (lua_State *L, int index);</pre>

 <p>
@ -5423,11 +5485,19 @@ that is equal to or below an active to-be-closed index.


 <p>
-This function can raise an out-of-memory error.
-In that case, the value in the given index is immediately closed,
+In the case of an out-of-memory error,
+the value in the given index is immediately closed,
 as if it was already marked.


+<p>
+Note that, both in case of errors and of a regular return,
+by the time the <code>__close</code> metamethod runs,
+the C&nbsp;stack was already unwound,
+so that any automatic C&nbsp;variable declared in the calling function
+will be out of scope.
+
+



@ -5482,18 +5552,12 @@ when <code>lua_tolstring</code> is applied to keys during a table traversal.)

 <p>
 <code>lua_tolstring</code> returns a pointer
-to a string inside the Lua state.
+to a string inside the Lua state (see <a href="#4.1.3">&sect;4.1.3</a>).
 This string always has a zero ('<code>\0</code>')
 after its last character (as in&nbsp;C),
 but can contain other zeros in its body.


-<p>
-Because Lua has garbage collection,
-there is no guarantee that the pointer returned by <code>lua_tolstring</code>
-will be valid after the corresponding Lua value is removed from the stack.
-
-



@ -5944,7 +6008,7 @@ true if the function is a vararg function
 </li>

 <li><b><code>ftransfer</code>: </b>
-the index on the stack of the first value being "transferred",
+the index in the stack of the first value being "transferred",
 that is, parameters in a call or return values in a return.
 (The other values are in consecutive indices.)
 Using this index, you can access and modify these values
@ -6141,7 +6205,7 @@ an identification of the <em>activation record</em>
 of the function executing at a given level.
 Level&nbsp;0 is the current running function,
 whereas level <em>n+1</em> is the function that has called level <em>n</em>
-(except for tail calls, which do not count on the stack).
+(except for tail calls, which do not count in the stack).
 When called with a level greater than the stack depth,
 <a href="#lua_getstack"><code>lua_getstack</code></a> returns 0;
 otherwise it returns 1.
@ -6218,24 +6282,6 @@ calling <a href="#lua_yield"><code>lua_yield</code></a> with <code>nresults</cod



-<hr><h3><a name="lua_setcstacklimit"><code>lua_setcstacklimit</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int (lua_setcstacklimit) (lua_State *L, unsigned int limit);</pre>
-
-<p>
-Sets a new limit for the C stack.
-This limit controls how deeply nested calls can go in Lua,
-with the intent of avoiding a stack overflow.
-Returns the old limit in case of success,
-or zero in case of error.
-For more details about this function,
-see <a href="#pdf-debug.setcstacklimit"><code>debug.setcstacklimit</code></a>,
-its equivalent in the standard library.
-
-
-
-
-
 <hr><h3><a name="lua_sethook"><code>lua_sethook</code></a></h3><p>
 <span class="apii">[-0, +0, &ndash;]</span>
 <pre>void lua_sethook (lua_State *L, lua_Hook f, int mask, int count);</pre>
@ -6259,8 +6305,7 @@ For each event, the hook is called as explained below:
 <ul>

 <li><b>The call hook: </b> is called when the interpreter calls a function.
-The hook is called just after Lua enters the new function,
-before the function gets its arguments.
+The hook is called just after Lua enters the new function.
 </li>

 <li><b>The return hook: </b> is called when the interpreter returns from a function.
@ -7573,7 +7618,7 @@ it returns <code>NULL</code> instead of raising an error.
 Converts any Lua value at the given index to a C&nbsp;string
 in a reasonable format.
 The resulting string is pushed onto the stack and also
-returned by the function.
+returned by the function (see <a href="#4.1.3">&sect;4.1.3</a>).
 If <code>len</code> is not <code>NULL</code>,
 the function also sets <code>*len</code> with the string length.

@ -8001,9 +8046,11 @@ The default is "<code>bt</code>".


 <p>
-Lua does not check the consistency of binary chunks.
-Maliciously crafted binary chunks can crash
-the interpreter.
+It is safe to load malformed binary chunks;
+<code>load</code> signals an appropriate error.
+However,
+Lua does not check the consistency of the code inside binary chunks;
+running maliciously crafted bytecode can crash the interpreter.



@ -8665,6 +8712,18 @@ As such, it is only available on some platforms
 plus other Unix systems that support the <code>dlfcn</code> standard).


+<p>
+This function is inherently insecure,
+as it allows Lua to call any function in any readable dynamic
+library in the system.
+(Lua calls any function assuming the function
+has a proper prototype and respects a proper protocol
+(see <a href="#lua_CFunction"><code>lua_CFunction</code></a>).
+Therefore,
+calling an arbitrary function in an arbitrary dynamic library
+more often than not results in an access violation.)
+
+


 <p>
@ -11084,7 +11143,7 @@ which means the function running at level <code>f</code> of the call stack
 of the given thread:
 level&nbsp;0 is the current function (<code>getinfo</code> itself);
 level&nbsp;1 is the function that called <code>getinfo</code>
-(except for tail calls, which do not count on the stack);
+(except for tail calls, which do not count in the stack);
 and so on.
 If <code>f</code> is a number greater than the number of active functions,
 then <code>getinfo</code> returns <b>fail</b>.
@ -11218,43 +11277,6 @@ to the userdata <code>u</code> plus a boolean,



-<p>
-<hr><h3><a name="pdf-debug.setcstacklimit"><code>debug.setcstacklimit (limit)</code></a></h3>
-
-
-<p>
-Sets a new limit for the C stack.
-This limit controls how deeply nested calls can go in Lua,
-with the intent of avoiding a stack overflow.
-A limit too small restricts recursive calls pointlessly;
-a limit too large exposes the interpreter to stack-overflow crashes.
-Unfortunately, there is no way to know a priori
-the maximum safe limit for a platform.
-
-
-<p>
-Each call made from Lua code counts one unit.
-Other operations (e.g., calls made from C to Lua or resuming a coroutine)
-may have a higher cost.
-
-
-<p>
-This function has the following restrictions:
-
-<ul>
-<li>It can only be called from the main coroutine (thread);</li>
-<li>It cannot be called while handling a stack-overflow error;</li>
-<li><code>limit</code> must be less than 40000;</li>
-<li><code>limit</code> cannot be less than the amount of C stack in use.</li>
-</ul><p>
-If a call does not respect some restriction,
-it returns a false value.
-Otherwise,
-the call returns the old limit.
-
-
-
-
 <p>
 <hr><h3><a name="pdf-debug.sethook"><code>debug.sethook ([thread,] hook, mask [, count])</code></a></h3>

@ -11886,10 +11908,10 @@ and LiteralString, see <a href="#3.1">&sect;3.1</a>.)

 <P CLASS="footer">
 Last update:
-Thu Jun 18 16:10:16 UTC 2020
+Fri Nov 13 15:35:22 UTC 2020
 </P>
 <!--
-Last change: revised for Lua 5.4.0 (final)
+Last change: revised for Lua 5.4.2
 -->

 </body></html>
--- a/lua-5.4.2/doc/osi-certified-72x60.png
+++ b/lua-5.4.2/doc/osi-certified-72x60.png
--- a/lua-5.4.2/doc/readme.html
+++ b/lua-5.4.2/doc/readme.html
@ -110,7 +110,7 @@ Here are the details.
 <OL>
 <LI>
 Open a terminal window and move to
-the top-level directory, which is named <TT>lua-5.4.0</TT>.
+the top-level directory, which is named <TT>lua-5.4.2</TT>.
 The <TT>Makefile</TT> there controls both the build process and the installation process.
 <P>
 <LI>
@ -330,10 +330,10 @@ THE SOFTWARE.

 <P CLASS="footer">
 Last update:
-Fri May  1 19:33:31 UTC 2020
+Tue Nov 10 20:55:28 UTC 2020
 </P>
 <!--
-Last change: revised for Lua 5.4.0 (final)
+Last change: revised for Lua 5.4.2
 -->

 </BODY>
--- a/lua-5.4.2/include/lauxlib.h
+++ b/lua-5.4.2/include/lauxlib.h
--- a/lua-5.4.2/include/lua.h
+++ b/lua-5.4.2/include/lua.h
@ -18,7 +18,7 @@

 #define LUA_VERSION_MAJOR	"5"
 #define LUA_VERSION_MINOR	"4"
-#define LUA_VERSION_RELEASE	"0"
+#define LUA_VERSION_RELEASE	"2"

 #define LUA_VERSION_NUM			504
 #define LUA_VERSION_RELEASE_NUM		(LUA_VERSION_NUM * 100 + 0)
--- a/lua-5.4.2/include/luaconf.h
+++ b/lua-5.4.2/include/luaconf.h
@ -36,21 +36,6 @@
 ** =====================================================================
 */

-/*
-@@ LUAI_MAXCSTACK defines the maximum depth for nested calls and
-** also limits the maximum depth of other recursive algorithms in
-** the implementation, such as syntactic analysis. A value too
-** large may allow the interpreter to crash (C-stack overflow).
-** The default value seems ok for regular machines, but may be
-** too high for restricted hardware.
-** The test file 'cstack.lua' may help finding a good limit.
-** (It will crash with a limit too high.)
-*/
-#if !defined(LUAI_MAXCSTACK)
-#define LUAI_MAXCSTACK		2000
-#endif
-
-
 /*
@@ LUA_USE_C89 controls the use of non-ISO-C89 features.
 ** Define it if you want Lua to avoid the use of a few C99 features
--- a/lua-5.4.2/include/lualib.h
+++ b/lua-5.4.2/include/lualib.h
--- a/lua-5.4.2/src/Makefile
+++ b/lua-5.4.2/src/Makefile
@ -26,7 +26,7 @@ MYLIBS=
 MYOBJS=

 # Special flags for compiler modules; -Os reduces code size.
-CMCFLAGS= -Os
+CMCFLAGS= 

 # == END OF USER SETTINGS -- NO NEED TO CHANGE ANYTHING BELOW THIS LINE =======

--- a/lua-5.4.2/src/lapi.c
+++ b/lua-5.4.2/src/lapi.c
@ -97,8 +97,9 @@ static StkId index2stack (lua_State *L, int idx) {

 LUA_API int lua_checkstack (lua_State *L, int n) {
  int res;
-  CallInfo *ci = L->ci;
+  CallInfo *ci;
  lua_lock(L);
+  ci = L->ci;
  api_check(L, n >= 0, "negative 'n'");
  if (L->stack_last - L->top > n)  /* stack large enough? */
    res = 1;  /* yes; check is OK */
@ -170,10 +171,12 @@ LUA_API int lua_gettop (lua_State *L) {


 LUA_API void lua_settop (lua_State *L, int idx) {
-  CallInfo *ci = L->ci;
-  StkId func = ci->func;
+  CallInfo *ci;
+  StkId func;
  ptrdiff_t diff;  /* difference for new top */
  lua_lock(L);
+  ci = L->ci;
+  func = ci->func;
  if (idx >= 0) {
    api_check(L, idx <= ci->top - (func + 1), "new top too large");
    diff = ((func + 1) + idx) - L->top;
@ -376,20 +379,22 @@ LUA_API int lua_toboolean (lua_State *L, int idx) {


 LUA_API const char *lua_tolstring (lua_State *L, int idx, size_t *len) {
-  TValue *o = index2value(L, idx);
+  TValue *o;
+  lua_lock(L);
+  o = index2value(L, idx);
  if (!ttisstring(o)) {
    if (!cvt2str(o)) {  /* not convertible? */
      if (len != NULL) *len = 0;
+      lua_unlock(L);
      return NULL;
    }
-    lua_lock(L);  /* 'luaO_tostring' may create a new string */
    luaO_tostring(L, o);
    luaC_checkGC(L);
    o = index2value(L, idx);  /* previous call may reallocate the stack */
-    lua_unlock(L);
  }
  if (len != NULL)
    *len = vslen(o);
+  lua_unlock(L);
  return svalue(o);
 }

@ -563,6 +568,7 @@ LUA_API void lua_pushcclosure (lua_State *L, lua_CFunction fn, int n) {
    while (n--) {
      setobj2n(L, &cl->upvalue[n], s2v(L->top + n));
      /* does not need barrier because closure is white */
+      lua_assert(iswhite(cl));
    }
    setclCvalue(L, s2v(L->top), cl);
    api_incr_top(L);
@ -624,8 +630,9 @@ static int auxgetstr (lua_State *L, const TValue *t, const char *k) {


 LUA_API int lua_getglobal (lua_State *L, const char *name) {
-  Table *reg = hvalue(&G(L)->l_registry);
+  Table *reg;
  lua_lock(L);
+  reg = hvalue(&G(L)->l_registry);
  return auxgetstr(L, luaH_getint(reg, LUA_RIDX_GLOBALS), name);
 }

@ -804,8 +811,9 @@ static void auxsetstr (lua_State *L, const TValue *t, const char *k) {


 LUA_API void lua_setglobal (lua_State *L, const char *name) {
-  Table *reg = hvalue(&G(L)->l_registry);
+  Table *reg;
  lua_lock(L);  /* unlock done in 'auxsetstr' */
+  reg = hvalue(&G(L)->l_registry);
  auxsetstr(L, luaH_getint(reg, LUA_RIDX_GLOBALS), name);
 }

@ -1093,8 +1101,9 @@ LUA_API int lua_status (lua_State *L) {
 LUA_API int lua_gc (lua_State *L, int what, ...) {
  va_list argp;
  int res = 0;
-  global_State *g = G(L);
+  global_State *g;
  lua_lock(L);
+  g = G(L);
  va_start(argp, what);
  switch (what) {
    case LUA_GCSTOP: {
@ -1194,9 +1203,15 @@ LUA_API int lua_gc (lua_State *L, int what, ...) {


 LUA_API int lua_error (lua_State *L) {
+  TValue *errobj;
  lua_lock(L);
+  errobj = s2v(L->top - 1);
  api_checknelems(L, 1);
-  luaG_errormsg(L);
+  /* error object is the memory error message? */
+  if (ttisshrstring(errobj) && eqshrstr(tsvalue(errobj), G(L)->memerrmsg))
+    luaM_error(L);  /* raise a memory error */
+  else
+    luaG_errormsg(L);  /* raise a regular error */
  /* code unreachable; will unlock when control actually leaves the kernel */
  return 0;  /* to avoid warnings */
 }
@ -1238,14 +1253,12 @@ LUA_API void lua_toclose (lua_State *L, int idx) {
 LUA_API void lua_concat (lua_State *L, int n) {
  lua_lock(L);
  api_checknelems(L, n);
-  if (n >= 2) {
+  if (n > 0)
    luaV_concat(L, n);
-  }
-  else if (n == 0) {  /* push empty string */
-    setsvalue2s(L, L->top, luaS_newlstr(L, "", 0));
+  else {  /* nothing to concatenate */
+    setsvalue2s(L, L->top, luaS_newlstr(L, "", 0));  /* push empty string */
    api_incr_top(L);
  }
-  /* else n == 1; nothing to do */
  luaC_checkGC(L);
  lua_unlock(L);
 }
@ -1370,13 +1383,16 @@ LUA_API const char *lua_setupvalue (lua_State *L, int funcindex, int n) {


 static UpVal **getupvalref (lua_State *L, int fidx, int n, LClosure **pf) {
+  static const UpVal *const nullup = NULL;
  LClosure *f;
  TValue *fi = index2value(L, fidx);
  api_check(L, ttisLclosure(fi), "Lua function expected");
  f = clLvalue(fi);
-  api_check(L, (1 <= n && n <= f->p->sizeupvalues), "invalid upvalue index");
  if (pf) *pf = f;
+  if (1 <= n && n <= f->p->sizeupvalues)
    return &f->upvals[n - 1];  /* get its upvalue pointer */
+  else
+    return (UpVal**)&nullup;
 }


@ -1388,11 +1404,14 @@ LUA_API void *lua_upvalueid (lua_State *L, int fidx, int n) {
    }
    case LUA_VCCL: {  /* C closure */
      CClosure *f = clCvalue(fi);
-      api_check(L, 1 <= n && n <= f->nupvalues, "invalid upvalue index");
+      if (1 <= n && n <= f->nupvalues)
        return &f->upvalue[n - 1];
-    }
+      /* else */
+    }  /* FALLTHROUGH */
+    case LUA_VLCF:
+      return NULL;  /* light C functions have no upvalues */
    default: {
-      api_check(L, 0, "closure expected");
+      api_check(L, 0, "function expected");
      return NULL;
    }
  }
@ -1404,6 +1423,7 @@ LUA_API void lua_upvaluejoin (lua_State *L, int fidx1, int n1,
  LClosure *f1;
  UpVal **up1 = getupvalref(L, fidx1, n1, &f1);
  UpVal **up2 = getupvalref(L, fidx2, n2, NULL);
+  api_check(L, *up1 != NULL && *up2 != NULL, "invalid upvalue index");
  *up1 = *up2;
  luaC_objbarrier(L, f1, *up1);
 }
--- a/lua-5.4.2/src/lapi.h
+++ b/lua-5.4.2/src/lapi.h
--- a/lua-5.4.2/src/lauxlib.c
+++ b/lua-5.4.2/src/lauxlib.c
@ -283,10 +283,10 @@ LUALIB_API int luaL_fileresult (lua_State *L, int stat, const char *fname) {


 LUALIB_API int luaL_execresult (lua_State *L, int stat) {
-  const char *what = "exit";  /* type of termination */
  if (stat != 0 && errno != 0)  /* error with an 'errno'? */
    return luaL_fileresult(L, 0, NULL);
  else {
+    const char *what = "exit";  /* type of termination */
    l_inspectstat(stat, what);  /* interpret result */
    if (*what == 'e' && stat == 0)  /* successful termination? */
      lua_pushboolean(L, 1);
@ -475,8 +475,10 @@ static void *resizebox (lua_State *L, int idx, size_t newsize) {
  lua_Alloc allocf = lua_getallocf(L, &ud);
  UBox *box = (UBox *)lua_touserdata(L, idx);
  void *temp = allocf(ud, box->box, box->bsize, newsize);
-  if (temp == NULL && newsize > 0)  /* allocation error? */
-    luaL_error(L, "not enough memory");
+  if (temp == NULL && newsize > 0) {  /* allocation error? */
+    lua_pushliteral(L, "not enough memory");
+    lua_error(L);  /* raise a memory error */
+  }
  box->box = temp;
  box->bsize = newsize;
  return temp;
@ -1004,43 +1006,67 @@ static int panic (lua_State *L) {


 /*
-** Emit a warning. '*warnstate' means:
-** 0 - warning system is off;
-** 1 - ready to start a new message;
-** 2 - previous message is to be continued.
+** Warning functions:
+** warnfoff: warning system is off
+** warnfon: ready to start a new message
+** warnfcont: previous message is to be continued
 */
-static void warnf (void *ud, const char *message, int tocont) {
-  int *warnstate = (int *)ud;
-  if (*warnstate != 2 && !tocont && *message == '@') {  /* control message? */
-    if (strcmp(message, "@off") == 0)
-      *warnstate = 0;
-    else if (strcmp(message, "@on") == 0)
-      *warnstate = 1;
-    return;
+static void warnfoff (void *ud, const char *message, int tocont);
+static void warnfon (void *ud, const char *message, int tocont);
+static void warnfcont (void *ud, const char *message, int tocont);
+
+
+/*
+** Check whether message is a control message. If so, execute the
+** control or ignore it if unknown.
+*/
+static int checkcontrol (lua_State *L, const char *message, int tocont) {
+  if (tocont || *(message++) != '@')  /* not a control message? */
+    return 0;
+  else {
+    if (strcmp(message, "off") == 0)
+      lua_setwarnf(L, warnfoff, L);  /* turn warnings off */
+    else if (strcmp(message, "on") == 0)
+      lua_setwarnf(L, warnfon, L);   /* turn warnings on */
+    return 1;  /* it was a control message */
  }
-  else if (*warnstate == 0)  /* warnings off? */
-    return;
-  if (*warnstate == 1)  /* previous message was the last? */
-    lua_writestringerror("%s", "Lua warning: ");  /* start a new warning */
+}
+
+
+static void warnfoff (void *ud, const char *message, int tocont) {
+  checkcontrol((lua_State *)ud, message, tocont);
+}
+
+
+/*
+** Writes the message and handle 'tocont', finishing the message
+** if needed and setting the next warn function.
+*/
+static void warnfcont (void *ud, const char *message, int tocont) {
+  lua_State *L = (lua_State *)ud;
  lua_writestringerror("%s", message);  /* write message */
  if (tocont)  /* not the last part? */
-    *warnstate = 2;  /* to be continued */
+    lua_setwarnf(L, warnfcont, L);  /* to be continued */
  else {  /* last part */
    lua_writestringerror("%s", "\n");  /* finish message with end-of-line */
-    *warnstate = 1;  /* ready to start a new message */
+    lua_setwarnf(L, warnfon, L);  /* next call is a new message */
  }
 }


+static void warnfon (void *ud, const char *message, int tocont) {
+  if (checkcontrol((lua_State *)ud, message, tocont))  /* control message? */
+    return;  /* nothing else to be done */
+  lua_writestringerror("%s", "Lua warning: ");  /* start a new warning */
+  warnfcont(ud, message, tocont);  /* finish processing */
+}
+
+
 LUALIB_API lua_State *luaL_newstate (void) {
  lua_State *L = lua_newstate(l_alloc, NULL);
  if (L) {
-    int *warnstate;  /* space for warning state */
    lua_atpanic(L, &panic);
-    warnstate = (int *)lua_newuserdatauv(L, sizeof(int), 0);
-    luaL_ref(L, LUA_REGISTRYINDEX);  /* make sure it won't be collected */
-    *warnstate = 0;  /* default is warnings off */
-    lua_setwarnf(L, warnf, warnstate);
+    lua_setwarnf(L, warnfoff, L);  /* default is warnings off */
  }
  return L;
 }
--- a/lua-5.4.2/src/lbaselib.c
+++ b/lua-5.4.2/src/lbaselib.c
--- a/lua-5.4.2/src/lcode.c
+++ b/lua-5.4.2/src/lcode.c
@ -753,7 +753,7 @@ void luaK_setoneret (FuncState *fs, expdesc *e) {


 /*
-** Ensure that expression 'e' is not a variable (nor a constant).
+** Ensure that expression 'e' is not a variable (nor a <const>).
 ** (Expression still may have jump lists.)
 */
 void luaK_dischargevars (FuncState *fs, expdesc *e) {
@ -805,8 +805,8 @@ void luaK_dischargevars (FuncState *fs, expdesc *e) {


 /*
-** Ensures expression value is in register 'reg' (and therefore
-** 'e' will become a non-relocatable expression).
+** Ensure expression value is in register 'reg', making 'e' a
+** non-relocatable expression.
 ** (Expression still may have jump lists.)
 */
 static void discharge2reg (FuncState *fs, expdesc *e, int reg) {
@ -860,7 +860,8 @@ static void discharge2reg (FuncState *fs, expdesc *e, int reg) {


 /*
-** Ensures expression value is in any register.
+** Ensure expression value is in a register, making 'e' a
+** non-relocatable expression.
 ** (Expression still may have jump lists.)
 */
 static void discharge2anyreg (FuncState *fs, expdesc *e) {
@ -946,8 +947,11 @@ int luaK_exp2anyreg (FuncState *fs, expdesc *e) {
      exp2reg(fs, e, e->u.info);  /* put final result in it */
      return e->u.info;
    }
+    /* else expression has jumps and cannot change its register
+       to hold the jump values, because it is a local variable.
+       Go through to the default case. */
  }
-  luaK_exp2nextreg(fs, e);  /* otherwise, use next available register */
+  luaK_exp2nextreg(fs, e);  /* default: use next available register */
  return e->u.info;
 }

--- a/lua-5.4.2/src/lcode.h
+++ b/lua-5.4.2/src/lcode.h
--- a/lua-5.4.2/src/lcorolib.c
+++ b/lua-5.4.2/src/lcorolib.c
@ -73,11 +73,12 @@ static int luaB_coresume (lua_State *L) {
 static int luaB_auxwrap (lua_State *L) {
  lua_State *co = lua_tothread(L, lua_upvalueindex(1));
  int r = auxresume(L, co, lua_gettop(L));
-  if (r < 0) {
+  if (r < 0) {  /* error? */
    int stat = lua_status(co);
-    if (stat != LUA_OK && stat != LUA_YIELD)
-      lua_resetthread(co);  /* close variables in case of errors */
-    if (lua_type(L, -1) == LUA_TSTRING) {  /* error object is a string? */
+    if (stat != LUA_OK && stat != LUA_YIELD)  /* error in the coroutine? */
+      lua_resetthread(co);  /* close its tbc variables */
+    if (stat != LUA_ERRMEM &&  /* not a memory error and ... */
+        lua_type(L, -1) == LUA_TSTRING) {  /* ... error object is a string? */
      luaL_where(L, 1);  /* add extra info, if available */
      lua_insert(L, -2);
      lua_concat(L, 2);
--- a/lua-5.4.2/src/lctype.c
+++ b/lua-5.4.2/src/lctype.c
--- a/lua-5.4.2/src/lctype.h
+++ b/lua-5.4.2/src/lctype.h
@ -13,7 +13,7 @@
 /*
 ** WARNING: the functions defined here do not necessarily correspond
 ** to the similar functions in the standard C ctype.h. They are
-** optimized for the specific needs of Lua
+** optimized for the specific needs of Lua.
 */

 #if !defined(LUA_USE_CTYPE)
@ -61,13 +61,19 @@
 #define lisprint(c)	testprop(c, MASK(PRINTBIT))
 #define lisxdigit(c)	testprop(c, MASK(XDIGITBIT))

+
 /*
-** this 'ltolower' only works for alphabetic characters
+** In ASCII, this 'ltolower' is correct for alphabetic characters and
+** for '.'. That is enough for Lua needs. ('check_exp' ensures that
+** the character either is an upper-case letter or is unchanged by
+** the transformation, which holds for lower-case letters and '.'.)
 */
-#define ltolower(c)	((c) | ('A' ^ 'a'))
+#define ltolower(c)  \
+  check_exp(('A' <= (c) && (c) <= 'Z') || (c) == ((c) | ('A' ^ 'a')),  \
+            (c) | ('A' ^ 'a'))


-/* two more entries for 0 and -1 (EOZ) */
+/* one entry for each character and for -1 (EOZ) */
 LUAI_DDEC(const lu_byte luai_ctype_[UCHAR_MAX + 2];)


--- a/lua-5.4.2/src/ldblib.c
+++ b/lua-5.4.2/src/ldblib.c
@ -281,25 +281,33 @@ static int db_setupvalue (lua_State *L) {
 ** Check whether a given upvalue from a given closure exists and
 ** returns its index
 */
-static int checkupval (lua_State *L, int argf, int argnup) {
+static void *checkupval (lua_State *L, int argf, int argnup, int *pnup) {
+  void *id;
  int nup = (int)luaL_checkinteger(L, argnup);  /* upvalue index */
  luaL_checktype(L, argf, LUA_TFUNCTION);  /* closure */
-  luaL_argcheck(L, (lua_getupvalue(L, argf, nup) != NULL), argnup,
-                   "invalid upvalue index");
-  return nup;
+  id = lua_upvalueid(L, argf, nup);
+  if (pnup) {
+    luaL_argcheck(L, id != NULL, argnup, "invalid upvalue index");
+    *pnup = nup;
+  }
+  return id;
 }


 static int db_upvalueid (lua_State *L) {
-  int n = checkupval(L, 1, 2);
-  lua_pushlightuserdata(L, lua_upvalueid(L, 1, n));
+  void *id = checkupval(L, 1, 2, NULL);
+  if (id != NULL)
+    lua_pushlightuserdata(L, id);
+  else
+    luaL_pushfail(L);
  return 1;
 }


 static int db_upvaluejoin (lua_State *L) {
-  int n1 = checkupval(L, 1, 2);
-  int n2 = checkupval(L, 3, 4);
+  int n1, n2;
+  checkupval(L, 1, 2, &n1);
+  checkupval(L, 3, 4, &n2);
  luaL_argcheck(L, !lua_iscfunction(L, 1), 1, "Lua function expected");
  luaL_argcheck(L, !lua_iscfunction(L, 3), 3, "Lua function expected");
  lua_upvaluejoin(L, 1, n1, 3, n2);
@ -440,9 +448,6 @@ static int db_traceback (lua_State *L) {
 static int db_setcstacklimit (lua_State *L) {
  int limit = (int)luaL_checkinteger(L, 1);
  int res = lua_setcstacklimit(L, limit);
-  if (res == 0)
-    lua_pushboolean(L, 0);
-  else
  lua_pushinteger(L, res);
  return 1;
 }
--- a/lua-5.4.2/src/ldebug.c
+++ b/lua-5.4.2/src/ldebug.c
@ -33,10 +33,8 @@

 #define noLuaClosure(f)		((f) == NULL || (f)->c.tt == LUA_VCCL)

-
-/* Active Lua function (given call info) */
-#define ci_func(ci)		(clLvalue(s2v((ci)->func)))
-
+/* inverse of 'pcRel' */
+#define invpcRel(pc, p)		((p)->code + (pc) + 1)

 static const char *funcnamefromcode (lua_State *L, CallInfo *ci,
                                    const char **name);
@ -127,20 +125,18 @@ static void settraps (CallInfo *ci) {
 /*
 ** This function can be called during a signal, under "reasonable"
 ** assumptions.
-** Fields 'oldpc', 'basehookcount', and 'hookcount' (set by
-** 'resethookcount') are for debug only, and it is no problem if they
-** get arbitrary values (causes at most one wrong hook call). 'hookmask'
-** is an atomic value. We assume that pointers are atomic too (e.g., gcc
-** ensures that for all platforms where it runs). Moreover, 'hook' is
-** always checked before being called (see 'luaD_hook').
+** Fields 'basehookcount' and 'hookcount' (set by 'resethookcount')
+** are for debug only, and it is no problem if they get arbitrary
+** values (causes at most one wrong hook call). 'hookmask' is an atomic
+** value. We assume that pointers are atomic too (e.g., gcc ensures that
+** for all platforms where it runs). Moreover, 'hook' is always checked
+** before being called (see 'luaD_hook').
 */
 LUA_API void lua_sethook (lua_State *L, lua_Hook func, int mask, int count) {
  if (func == NULL || mask == 0) {  /* turn off hooks? */
    mask = 0;
    func = NULL;
  }
-  if (isLua(L->ci))
-    L->oldpc = L->ci->u.l.savedpc;
  L->hook = func;
  L->basehookcount = count;
  resethookcount(L);
@ -192,8 +188,8 @@ static const char *upvalname (const Proto *p, int uv) {
 static const char *findvararg (CallInfo *ci, int n, StkId *pos) {
  if (clLvalue(s2v(ci->func))->p->is_vararg) {
    int nextra = ci->u.l.nextraargs;
-    if (n <= nextra) {
-      *pos = ci->func - nextra + (n - 1);
+    if (n >= -nextra) {  /* 'n' is negative */
+      *pos = ci->func - nextra - (n + 1);
      return "(vararg)";  /* generic name for any vararg */
    }
  }
@ -206,7 +202,7 @@ const char *luaG_findlocal (lua_State *L, CallInfo *ci, int n, StkId *pos) {
  const char *name = NULL;
  if (isLua(ci)) {
    if (n < 0)  /* access to vararg values? */
-      return findvararg(ci, -n, pos);
+      return findvararg(ci, n, pos);
    else
      name = luaF_getlocalname(ci_func(ci)->p, n, currentpc(ci));
  }
@ -787,18 +783,34 @@ l_noret luaG_runerror (lua_State *L, const char *fmt, ...) {
 ** previous instruction 'oldpc'.
 */
 static int changedline (const Proto *p, int oldpc, int newpc) {
+  if (p->lineinfo == NULL)  /* no debug information? */
+    return 0;
  while (oldpc++ < newpc) {
    if (p->lineinfo[oldpc] != 0)
      return (luaG_getfuncline(p, oldpc - 1) != luaG_getfuncline(p, newpc));
  }
-  return 0;  /* no line changes in the way */
+  return 0;  /* no line changes between positions */
 }


+/*
+** Traces the execution of a Lua function. Called before the execution
+** of each opcode, when debug is on. 'L->oldpc' stores the last
+** instruction traced, to detect line changes. When entering a new
+** function, 'npci' will be zero and will test as a new line without
+** the need for 'oldpc'; so, 'oldpc' does not need to be initialized
+** before. Some exceptional conditions may return to a function without
+** updating 'oldpc'. In that case, 'oldpc' may be invalid; if so, it is
+** reset to zero.  (A wrong but valid 'oldpc' at most causes an extra
+** call to a line hook.)
+*/
 int luaG_traceexec (lua_State *L, const Instruction *pc) {
  CallInfo *ci = L->ci;
  lu_byte mask = L->hookmask;
+  const Proto *p = ci_func(ci)->p;
  int counthook;
+  /* 'L->oldpc' may be invalid; reset it in this case */
+  int oldpc = (L->oldpc < p->sizecode) ? L->oldpc : 0;
  if (!(mask & (LUA_MASKLINE | LUA_MASKCOUNT))) {  /* no hooks? */
    ci->u.l.trap = 0;  /* don't need to stop again */
    return 0;  /* turn off 'trap' */
@ -819,15 +831,14 @@ int luaG_traceexec (lua_State *L, const Instruction *pc) {
  if (counthook)
    luaD_hook(L, LUA_HOOKCOUNT, -1, 0, 0);  /* call count hook */
  if (mask & LUA_MASKLINE) {
-    const Proto *p = ci_func(ci)->p;
    int npci = pcRel(pc, p);
    if (npci == 0 ||  /* call linehook when enter a new function, */
-        pc <= L->oldpc ||  /* when jump back (loop), or when */
-        changedline(p, pcRel(L->oldpc, p), npci)) {  /* enter new line */
+        pc <= invpcRel(oldpc, p) ||  /* when jump back (loop), or when */
+        changedline(p, oldpc, npci)) {  /* enter new line */
      int newline = luaG_getfuncline(p, npci);
      luaD_hook(L, LUA_HOOKLINE, newline, 0, 0);  /* call line hook */
    }
-    L->oldpc = pc;  /* 'pc' of last call to line hook */
+    L->oldpc = npci;  /* 'pc' of last call to line hook */
  }
  if (L->status == LUA_YIELD) {  /* did hook yield? */
    if (counthook)
--- a/lua-5.4.2/src/ldebug.h
+++ b/lua-5.4.2/src/ldebug.h
@ -13,6 +13,11 @@

 #define pcRel(pc, p)	(cast_int((pc) - (p)->code) - 1)

+
+/* Active Lua function (given call info) */
+#define ci_func(ci)		(clLvalue(s2v((ci)->func)))
+
+
 #define resethookcount(L)	(L->hookcount = L->basehookcount)

 /*
--- a/lua-5.4.2/src/ldo.c
+++ b/lua-5.4.2/src/ldo.c
@ -139,8 +139,7 @@ l_noret luaD_throw (lua_State *L, int errcode) {


 int luaD_rawrunprotected (lua_State *L, Pfunc f, void *ud) {
-  global_State *g = G(L);
-  l_uint32 oldnCcalls = g->Cstacklimit - (L->nCcalls + L->nci);
+  l_uint32 oldnCcalls = L->nCcalls;
  struct lua_longjmp lj;
  lj.status = LUA_OK;
  lj.previous = L->errorJmp;  /* chain new error handler */
@ -149,7 +148,7 @@ int luaD_rawrunprotected (lua_State *L, Pfunc f, void *ud) {
    (*f)(L, ud);
  );
  L->errorJmp = lj.previous;  /* restore old error handler */
-  L->nCcalls = g->Cstacklimit - oldnCcalls - L->nci;
+  L->nCcalls = oldnCcalls;
  return lj.status;
 }

@ -183,21 +182,20 @@ static void correctstack (lua_State *L, StkId oldstack, StkId newstack) {


 int luaD_reallocstack (lua_State *L, int newsize, int raiseerror) {
-  int lim = L->stacksize;
-  StkId newstack = luaM_reallocvector(L, L->stack, lim, newsize, StackValue);
+  int lim = stacksize(L);
+  StkId newstack = luaM_reallocvector(L, L->stack,
+                      lim + EXTRA_STACK, newsize + EXTRA_STACK, StackValue);
  lua_assert(newsize <= LUAI_MAXSTACK || newsize == ERRORSTACKSIZE);
-  lua_assert(L->stack_last - L->stack == L->stacksize - EXTRA_STACK);
  if (unlikely(newstack == NULL)) {  /* reallocation failed? */
    if (raiseerror)
      luaM_error(L);
    else return 0;  /* do not raise an error */
  }
  for (; lim < newsize; lim++)
-    setnilvalue(s2v(newstack + lim)); /* erase new segment */
+    setnilvalue(s2v(newstack + lim + EXTRA_STACK)); /* erase new segment */
  correctstack(L, L->stack, newstack);
  L->stack = newstack;
-  L->stacksize = newsize;
-  L->stack_last = L->stack + newsize - EXTRA_STACK;
+  L->stack_last = L->stack + newsize;
  return 1;
 }

@ -207,52 +205,73 @@ int luaD_reallocstack (lua_State *L, int newsize, int raiseerror) {
 ** is true, raises any error; otherwise, return 0 in case of errors.
 */
 int luaD_growstack (lua_State *L, int n, int raiseerror) {
-  int size = L->stacksize;
-  int newsize = 2 * size;  /* tentative new size */
-  if (unlikely(size > LUAI_MAXSTACK)) {  /* need more space after extra size? */
+  int size = stacksize(L);
+  if (unlikely(size > LUAI_MAXSTACK)) {
+    /* if stack is larger than maximum, thread is already using the
+       extra space reserved for errors, that is, thread is handling
+       a stack error; cannot grow further than that. */
+    lua_assert(stacksize(L) == ERRORSTACKSIZE);
    if (raiseerror)
      luaD_throw(L, LUA_ERRERR);  /* error inside message handler */
-    else return 0;
+    return 0;  /* if not 'raiseerror', just signal it */
  }
  else {
-    int needed = cast_int(L->top - L->stack) + n + EXTRA_STACK;
+    int newsize = 2 * size;  /* tentative new size */
+    int needed = cast_int(L->top - L->stack) + n;
    if (newsize > LUAI_MAXSTACK)  /* cannot cross the limit */
      newsize = LUAI_MAXSTACK;
    if (newsize < needed)  /* but must respect what was asked for */
      newsize = needed;
-    if (unlikely(newsize > LUAI_MAXSTACK)) {  /* stack overflow? */
+    if (likely(newsize <= LUAI_MAXSTACK))
+      return luaD_reallocstack(L, newsize, raiseerror);
+    else {  /* stack overflow */
      /* add extra size to be able to handle the error message */
      luaD_reallocstack(L, ERRORSTACKSIZE, raiseerror);
      if (raiseerror)
        luaG_runerror(L, "stack overflow");
-      else return 0;
+      return 0;
+    }
  }
-  }  /* else no errors */
-  return luaD_reallocstack(L, newsize, raiseerror);
 }


 static int stackinuse (lua_State *L) {
  CallInfo *ci;
+  int res;
  StkId lim = L->top;
  for (ci = L->ci; ci != NULL; ci = ci->previous) {
    if (lim < ci->top) lim = ci->top;
  }
  lua_assert(lim <= L->stack_last);
-  return cast_int(lim - L->stack) + 1;  /* part of stack in use */
+  res = cast_int(lim - L->stack) + 1;  /* part of stack in use */
+  if (res < LUA_MINSTACK)
+    res = LUA_MINSTACK;  /* ensure a minimum size */
+  return res;
 }


+/*
+** If stack size is more than 3 times the current use, reduce that size
+** to twice the current use. (So, the final stack size is at most 2/3 the
+** previous size, and half of its entries are empty.)
+** As a particular case, if stack was handling a stack overflow and now
+** it is not, 'max' (limited by LUAI_MAXSTACK) will be smaller than
+** stacksize (equal to ERRORSTACKSIZE in this case), and so the stack
+** will be reduced to a "regular" size.
+*/
 void luaD_shrinkstack (lua_State *L) {
  int inuse = stackinuse(L);
-  int goodsize = inuse + (inuse / 8) + 2*EXTRA_STACK;
-  if (goodsize > LUAI_MAXSTACK)
-    goodsize = LUAI_MAXSTACK;  /* respect stack limit */
+  int nsize = inuse * 2;  /* proposed new size */
+  int max = inuse * 3;  /* maximum "reasonable" size */
+  if (max > LUAI_MAXSTACK) {
+    max = LUAI_MAXSTACK;  /* respect stack limit */
+    if (nsize > LUAI_MAXSTACK)
+      nsize = LUAI_MAXSTACK;
+  }
  /* if thread is currently not handling a stack overflow and its
-     good size is smaller than current size, shrink its stack */
-  if (inuse <= (LUAI_MAXSTACK - EXTRA_STACK) &&
-      goodsize < L->stacksize)
-    luaD_reallocstack(L, goodsize, 0);  /* ok if that fails */
+     size is larger than maximum "reasonable" size, shrink it */
+  if (inuse <= LUAI_MAXSTACK && stacksize(L) > max)
+    luaD_reallocstack(L, nsize, 0);  /* ok if that fails */
  else  /* don't change stack */
    condmovestack(L,{},{});  /* (change only for debugging) */
  luaE_shrinkCI(L);  /* shrink CI list */
@ -328,7 +347,7 @@ static StkId rethook (lua_State *L, CallInfo *ci, StkId firstres, int nres) {
  ptrdiff_t oldtop = savestack(L, L->top);  /* hook may change top */
  int delta = 0;
  if (isLuacode(ci)) {
-    Proto *p = clLvalue(s2v(ci->func))->p;
+    Proto *p = ci_func(ci)->p;
    if (p->is_vararg)
      delta = ci->u.l.nextraargs + p->numparams + 1;
    if (L->top < ci->top)
@ -341,15 +360,15 @@ static StkId rethook (lua_State *L, CallInfo *ci, StkId firstres, int nres) {
    luaD_hook(L, LUA_HOOKRET, -1, ftransfer, nres);  /* call it */
    ci->func -= delta;
  }
-  if (isLua(ci->previous))
-    L->oldpc = ci->previous->u.l.savedpc;  /* update 'oldpc' */
+  if (isLua(ci = ci->previous))
+    L->oldpc = pcRel(ci->u.l.savedpc, ci_func(ci)->p);  /* update 'oldpc' */
  return restorestack(L, oldtop);
 }


 /*
 ** Check whether 'func' has a '__call' metafield. If so, put it in the
-** stack, below original 'func', so that 'luaD_call' can call it. Raise
+** stack, below original 'func', so that 'luaD_precall' can call it. Raise
 ** an error if there is no '__call' metafield.
 */
 void luaD_tryfuncTM (lua_State *L, StkId func) {
@ -450,12 +469,14 @@ void luaD_pretailcall (lua_State *L, CallInfo *ci, StkId func, int narg1) {


 /*
-** Call a function (C or Lua). The function to be called is at *func.
-** The arguments are on the stack, right after the function.
-** When returns, all the results are on the stack, starting at the original
-** function position.
+** Prepares the call to a function (C or Lua). For C functions, also do
+** the call. The function to be called is at '*func'.  The arguments
+** are on the stack, right after the function.  Returns the CallInfo
+** to be executed, if it was a Lua function. Otherwise (a C function)
+** returns NULL, with all the results on the stack, starting at the
+** original function position.
 */
-void luaD_call (lua_State *L, StkId func, int nresults) {
+CallInfo *luaD_precall (lua_State *L, StkId func, int nresults) {
  lua_CFunction f;
 retry:
  switch (ttypetag(s2v(func))) {
@ -466,13 +487,13 @@ void luaD_call (lua_State *L, StkId func, int nresults) {
      f = fvalue(s2v(func));
     Cfunc: {
      int n;  /* number of returns */
-      CallInfo *ci = next_ci(L);
-      checkstackp(L, LUA_MINSTACK, func);  /* ensure minimum stack size */
+      CallInfo *ci;
+      checkstackGCp(L, LUA_MINSTACK, func);  /* ensure minimum stack size */
+      L->ci = ci = next_ci(L);
      ci->nresults = nresults;
      ci->callstatus = CIST_C;
      ci->top = L->top + LUA_MINSTACK;
      ci->func = func;
-      L->ci = ci;
      lua_assert(ci->top <= L->stack_last);
      if (L->hookmask & LUA_MASKCALL) {
        int narg = cast_int(L->top - func) - 1;
@ -483,29 +504,28 @@ void luaD_call (lua_State *L, StkId func, int nresults) {
      lua_lock(L);
      api_checknelems(L, n);
      luaD_poscall(L, ci, n);
-      break;
+      return NULL;
    }
    case LUA_VLCL: {  /* Lua function */
-      CallInfo *ci = next_ci(L);
+      CallInfo *ci;
      Proto *p = clLvalue(s2v(func))->p;
      int narg = cast_int(L->top - func) - 1;  /* number of real arguments */
      int nfixparams = p->numparams;
      int fsize = p->maxstacksize;  /* frame size */
-      checkstackp(L, fsize, func);
+      checkstackGCp(L, fsize, func);
+      L->ci = ci = next_ci(L);
      ci->nresults = nresults;
      ci->u.l.savedpc = p->code;  /* starting point */
-      ci->callstatus = 0;
      ci->top = func + 1 + fsize;
      ci->func = func;
      L->ci = ci;
      for (; narg < nfixparams; narg++)
        setnilvalue(s2v(L->top++));  /* complete missing arguments */
      lua_assert(ci->top <= L->stack_last);
-      luaV_execute(L, ci);  /* run the function */
-      break;
+      return ci;
    }
    default: {  /* not a function */
-      checkstackp(L, 1, func);  /* space for metamethod */
+      checkstackGCp(L, 1, func);  /* space for metamethod */
      luaD_tryfuncTM(L, func);  /* try to get '__call' metamethod */
      goto retry;  /* try again with metamethod */
    }
@ -513,18 +533,37 @@ void luaD_call (lua_State *L, StkId func, int nresults) {
 }


+/*
+** Call a function (C or Lua) through C. 'inc' can be 1 (increment
+** number of recursive invocations in the C stack) or nyci (the same
+** plus increment number of non-yieldable calls).
+*/
+static void ccall (lua_State *L, StkId func, int nResults, int inc) {
+  CallInfo *ci;
+  L->nCcalls += inc;
+  if (unlikely(getCcalls(L) >= LUAI_MAXCCALLS))
+    luaE_checkcstack(L);
+  if ((ci = luaD_precall(L, func, nResults)) != NULL) {  /* Lua function? */
+    ci->callstatus = CIST_FRESH;  /* mark that it is a "fresh" execute */
+    luaV_execute(L, ci);  /* call it */
+  }
+  L->nCcalls -= inc;
+}
+
+
+/*
+** External interface for 'ccall'
+*/
+void luaD_call (lua_State *L, StkId func, int nResults) {
+  ccall(L, func, nResults, 1);
+}
+
+
 /*
 ** Similar to 'luaD_call', but does not allow yields during the call.
-** If there is a stack overflow, freeing all CI structures will
-** force the subsequent call to invoke 'luaE_extendCI', which then
-** will raise any errors.
 */
 void luaD_callnoyield (lua_State *L, StkId func, int nResults) {
-  incXCcalls(L);
-  if (getCcalls(L) <= CSTACKERR)  /* possible stack overflow? */
-    luaE_freeCI(L);
-  luaD_call(L, func, nResults);
-  decXCcalls(L);
+  ccall(L, func, nResults, nyci);
 }


@ -602,12 +641,12 @@ static int recover (lua_State *L, int status) {
  if (ci == NULL) return 0;  /* no recovery point */
  /* "finish" luaD_pcall */
  oldtop = restorestack(L, ci->u2.funcidx);
-  luaF_close(L, oldtop, status);  /* may change the stack */
-  oldtop = restorestack(L, ci->u2.funcidx);
-  luaD_seterrorobj(L, status, oldtop);
  L->ci = ci;
  L->allowhook = getoah(ci->callstatus);  /* restore original 'allowhook' */
-  luaD_shrinkstack(L);
+  status = luaF_close(L, oldtop, status);  /* may change the stack */
+  oldtop = restorestack(L, ci->u2.funcidx);
+  luaD_seterrorobj(L, status, oldtop);
+  luaD_shrinkstack(L);   /* restore stack size in case of overflow */
  L->errfunc = ci->u.c.old_errfunc;
  return 1;  /* continue running the coroutine */
 }
@ -638,12 +677,12 @@ static void resume (lua_State *L, void *ud) {
  int n = *(cast(int*, ud));  /* number of arguments */
  StkId firstArg = L->top - n;  /* first argument */
  CallInfo *ci = L->ci;
-  if (L->status == LUA_OK) {  /* starting a coroutine? */
-    luaD_call(L, firstArg - 1, LUA_MULTRET);
-  }
+  if (L->status == LUA_OK)  /* starting a coroutine? */
+    ccall(L, firstArg - 1, LUA_MULTRET, 1);  /* just call its body */
  else {  /* resuming from previous yield */
    lua_assert(L->status == LUA_YIELD);
    L->status = LUA_OK;  /* mark that it is running (again) */
+    luaE_incCstack(L);  /* control the C stack */
    if (isLua(ci))  /* yielded inside a hook? */
      luaV_execute(L, ci);  /* just continue running Lua code */
    else {  /* 'common' yield */
@ -671,12 +710,7 @@ LUA_API int lua_resume (lua_State *L, lua_State *from, int nargs,
  }
  else if (L->status != LUA_YIELD)  /* ended with errors? */
    return resume_error(L, "cannot resume dead coroutine", nargs);
-  if (from == NULL)
-    L->nCcalls = CSTACKTHREAD;
-  else  /* correct 'nCcalls' for this thread */
-    L->nCcalls = getCcalls(from) + from->nci - L->nci - CSTACKCF;
-  if (L->nCcalls <= CSTACKERR)
-    return resume_error(L, "C stack overflow", nargs);
+  L->nCcalls = (from) ? getCcalls(from) : 0;
  luai_userstateresume(L, nargs);
  api_checknelems(L, (L->status == LUA_OK) ? nargs + 1 : nargs);
  status = luaD_rawrunprotected(L, resume, &nargs);
@ -706,9 +740,10 @@ LUA_API int lua_isyieldable (lua_State *L) {

 LUA_API int lua_yieldk (lua_State *L, int nresults, lua_KContext ctx,
                        lua_KFunction k) {
-  CallInfo *ci = L->ci;
+  CallInfo *ci;
  luai_userstateyield(L, nresults);
  lua_lock(L);
+  ci = L->ci;
  api_checknelems(L, nresults);
  if (unlikely(!yieldable(L))) {
    if (L != G(L)->mainthread)
@ -754,7 +789,7 @@ int luaD_pcall (lua_State *L, Pfunc func, void *u,
    status = luaF_close(L, oldtop, status);
    oldtop = restorestack(L, old_top);  /* previous call may change stack */
    luaD_seterrorobj(L, status, oldtop);
-    luaD_shrinkstack(L);
+    luaD_shrinkstack(L);   /* restore stack size in case of overflow */
  }
  L->errfunc = old_errfunc;
  return status;
--- a/lua-5.4.2/src/ldo.h
+++ b/lua-5.4.2/src/ldo.h
@ -17,6 +17,8 @@
 ** Macro to check stack size and grow stack if needed.  Parameters
 ** 'pre'/'pos' allow the macro to preserve a pointer into the
 ** stack across reallocations, doing the work only when needed.
+** It also allows the running of one GC step when the stack is
+** reallocated.
 ** 'condmovestack' is used in heavy tests to force a stack reallocation
 ** at every check.
 */
@ -35,7 +37,7 @@


 /* macro to check stack size, preserving 'p' */
-#define checkstackp(L,n,p)  \
+#define checkstackGCp(L,n,p)  \
  luaD_checkstackaux(L, n, \
    ptrdiff_t t__ = savestack(L, p);  /* save 'p' */ \
    luaC_checkGC(L),  /* stack grow uses memory */ \
@ -44,7 +46,7 @@

 /* macro to check stack size and GC */
 #define checkstackGC(L,fsize)  \
-	luaD_checkstackaux(L, (fsize), (void)0, luaC_checkGC(L))
+	luaD_checkstackaux(L, (fsize), luaC_checkGC(L), (void)0)


 /* type of protected functions, to be ran by 'runprotected' */
@ -57,6 +59,7 @@ LUAI_FUNC void luaD_hook (lua_State *L, int event, int line,
                                        int fTransfer, int nTransfer);
 LUAI_FUNC void luaD_hookcall (lua_State *L, CallInfo *ci);
 LUAI_FUNC void luaD_pretailcall (lua_State *L, CallInfo *ci, StkId func, int n);
+LUAI_FUNC CallInfo *luaD_precall (lua_State *L, StkId func, int nResults);
 LUAI_FUNC void luaD_call (lua_State *L, StkId func, int nResults);
 LUAI_FUNC void luaD_callnoyield (lua_State *L, StkId func, int nResults);
 LUAI_FUNC void luaD_tryfuncTM (lua_State *L, StkId func);
--- a/lua-5.4.2/src/ldump.c
+++ b/lua-5.4.2/src/ldump.c
--- a/lua-5.4.2/src/lfunc.c
+++ b/lua-5.4.2/src/lfunc.c
@ -53,7 +53,7 @@ void luaF_initupvals (lua_State *L, LClosure *cl) {
    uv->v = &uv->u.value;  /* make it closed */
    setnilvalue(uv->v);
    cl->upvals[i] = uv;
-    luaC_objbarrier(L, cl, o);
+    luaC_objbarrier(L, cl, uv);
  }
 }

@ -234,10 +234,11 @@ int luaF_close (lua_State *L, StkId level, int status) {
    luaF_unlinkupval(uv);
    setobj(L, slot, uv->v);  /* move value to upvalue slot */
    uv->v = slot;  /* now current value lives here */
-    if (!iswhite(uv))
-      gray2black(uv);  /* closed upvalues cannot be gray */
+    if (!iswhite(uv)) {  /* neither white nor dead? */
+      nw2black(uv);  /* closed upvalues cannot be gray */
      luaC_barrier(L, uv, slot);
    }
+  }
  return status;
 }

--- a/lua-5.4.2/src/lfunc.h
+++ b/lua-5.4.2/src/lfunc.h
--- a/lua-5.4.2/src/lgc.c
+++ b/lua-5.4.2/src/lgc.c
@ -60,16 +60,24 @@
 #define PAUSEADJ		100


-/* mask to erase all color bits (plus gen. related stuff) */
-#define maskcolors	(~(bitmask(BLACKBIT) | WHITEBITS | AGEBITS))
+/* mask with all color bits */
+#define maskcolors	(bitmask(BLACKBIT) | WHITEBITS)
+
+/* mask with all GC bits */
+#define maskgcbits      (maskcolors | AGEBITS)


-/* macro to erase all color bits then sets only the current white bit */
+/* macro to erase all color bits then set only the current white bit */
 #define makewhite(g,x)	\
- (x->marked = cast_byte((x->marked & maskcolors) | luaC_white(g)))
+  (x->marked = cast_byte((x->marked & ~maskcolors) | luaC_white(g)))

-#define white2gray(x)	resetbits(x->marked, WHITEBITS)
-#define black2gray(x)	resetbit(x->marked, BLACKBIT)
+/* make an object gray (neither white nor black) */
+#define set2gray(x)	resetbits(x->marked, maskcolors)
+
+
+/* make an object black (coming from any color) */
+#define set2black(x)  \
+  (x->marked = cast_byte((x->marked & ~WHITEBITS) | bitmask(BLACKBIT)))


 #define valiswhite(x)   (iscollectable(x) && iswhite(gcvalue(x)))
@ -77,16 +85,13 @@
 #define keyiswhite(n)   (keyiscollectable(n) && iswhite(gckey(n)))


-#define checkconsistency(obj)  \
-  lua_longassert(!iscollectable(obj) || righttt(obj))
-
 /*
 ** Protected access to objects in values
 */
 #define gcvalueN(o)     (iscollectable(o) ? gcvalue(o) : NULL)


-#define markvalue(g,o) { checkconsistency(o); \
+#define markvalue(g,o) { checkliveness(g->mainthread,o); \
  if (valiswhite(o)) reallymarkobject(g,gcvalue(o)); }

 #define markkey(g, n)	{ if keyiswhite(n) reallymarkobject(g,gckey(n)); }
@ -135,31 +140,38 @@ static GCObject **getgclist (GCObject *o) {


 /*
-** Link a collectable object 'o' with a known type into list pointed by 'p'.
+** Link a collectable object 'o' with a known type into the list 'p'.
+** (Must be a macro to access the 'gclist' field in different types.)
 */
-#define linkgclist(o,p)	((o)->gclist = (p), (p) = obj2gco(o))
+#define linkgclist(o,p)	linkgclist_(obj2gco(o), &(o)->gclist, &(p))
+
+static void linkgclist_ (GCObject *o, GCObject **pnext, GCObject **list) {
+  lua_assert(!isgray(o));  /* cannot be in a gray list */
+  *pnext = *list;
+  *list = o;
+  set2gray(o);  /* now it is */
+}


 /*
-** Link a generic collectable object 'o' into list pointed by 'p'.
+** Link a generic collectable object 'o' into the list 'p'.
 */
-#define linkobjgclist(o,p) (*getgclist(o) = (p), (p) = obj2gco(o))
+#define linkobjgclist(o,p) linkgclist_(obj2gco(o), getgclist(o), &(p))



 /*
-** Clear keys for empty entries in tables. If entry is empty
-** and its key is not marked, mark its entry as dead. This allows the
-** collection of the key, but keeps its entry in the table (its removal
-** could break a chain). The main feature of a dead key is that it must
-** be different from any other value, to do not disturb searches.
-** Other places never manipulate dead keys, because its associated empty
-** value is enough to signal that the entry is logically empty.
+** Clear keys for empty entries in tables. If entry is empty, mark its
+** entry as dead. This allows the collection of the key, but keeps its
+** entry in the table: its removal could break a chain and could break
+** a table traversal.  Other places never manipulate dead keys, because
+** its associated empty value is enough to signal that the entry is
+** logically empty.
 */
 static void clearkey (Node *n) {
  lua_assert(isempty(gval(n)));
-  if (keyiswhite(n))
-    setdeadkey(n);  /* unused and unmarked key; remove it */
+  if (keyiscollectable(n))
+    setdeadkey(n);  /* unused key; remove it */
 }


@ -181,14 +193,17 @@ static int iscleared (global_State *g, const GCObject *o) {


 /*
-** barrier that moves collector forward, that is, mark the white object
-** 'v' being pointed by the black object 'o'. (If in sweep phase, clear
-** the black object to white [sweep it] to avoid other barrier calls for
-** this same object.) In the generational mode, 'v' must also become
-** old, if 'o' is old; however, it cannot be changed directly to OLD,
-** because it may still point to non-old objects. So, it is marked as
-** OLD0. In the next cycle it will become OLD1, and in the next it
-** will finally become OLD (regular old).
+** Barrier that moves collector forward, that is, marks the white object
+** 'v' being pointed by the black object 'o'.  In the generational
+** mode, 'v' must also become old, if 'o' is old; however, it cannot
+** be changed directly to OLD, because it may still point to non-old
+** objects. So, it is marked as OLD0. In the next cycle it will become
+** OLD1, and in the next it will finally become OLD (regular old). By
+** then, any object it points to will also be old.  If called in the
+** incremental sweep phase, it clears the black object to white (sweep
+** it) to avoid other barrier calls for this same object. (That cannot
+** be done is generational mode, as its sweep does not distinguish
+** whites from deads.)
 */
 void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v) {
  global_State *g = G(L);
@ -202,7 +217,8 @@ void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v) {
  }
  else {  /* sweep phase */
    lua_assert(issweepphase(g));
-    makewhite(g, o);  /* mark main obj. as white to avoid other barriers */
+    if (g->gckind == KGC_INC)  /* incremental mode? */
+      makewhite(g, o);  /* mark 'o' as white to avoid other barriers */
  }
 }

@ -214,10 +230,12 @@ void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v) {
 void luaC_barrierback_ (lua_State *L, GCObject *o) {
  global_State *g = G(L);
  lua_assert(isblack(o) && !isdead(g, o));
-  lua_assert(g->gckind != KGC_GEN || (isold(o) && getage(o) != G_TOUCHED1));
-  if (getage(o) != G_TOUCHED2)  /* not already in gray list? */
-    linkobjgclist(o, g->grayagain);  /* link it in 'grayagain' */
-  black2gray(o);  /* make object gray (again) */
+  lua_assert((g->gckind == KGC_GEN) == (isold(o) && getage(o) != G_TOUCHED1));
+  if (getage(o) == G_TOUCHED2)  /* already in gray list? */
+    set2gray(o);  /* make it gray to become touched1 */
+  else  /* link it in 'grayagain' and paint it gray */
+    linkobjgclist(o, g->grayagain);
+  if (isold(o))  /* generational mode? */
    setage(o, G_TOUCHED1);  /* touched in current cycle */
 }

@ -225,7 +243,7 @@ void luaC_barrierback_ (lua_State *L, GCObject *o) {
 void luaC_fix (lua_State *L, GCObject *o) {
  global_State *g = G(L);
  lua_assert(g->allgc == o);  /* object must be 1st in 'allgc' list! */
-  white2gray(o);  /* they will be gray forever */
+  set2gray(o);  /* they will be gray forever */
  setage(o, G_OLD);  /* and old forever */
  g->allgc = o->next;  /* remove object from 'allgc' list */
  o->next = g->fixedgc;  /* link it to 'fixedgc' list */
@ -259,24 +277,30 @@ GCObject *luaC_newobj (lua_State *L, int tt, size_t sz) {


 /*
-** Mark an object. Userdata, strings, and closed upvalues are visited
-** and turned black here. Other objects are marked gray and added
-** to appropriate list to be visited (and turned black) later. (Open
-** upvalues are already linked in 'headuv' list. They are kept gray
-** to avoid barriers, as their values will be revisited by the thread.)
+** Mark an object.  Userdata with no user values, strings, and closed
+** upvalues are visited and turned black here.  Open upvalues are
+** already indirectly linked through their respective threads in the
+** 'twups' list, so they don't go to the gray list; nevertheless, they
+** are kept gray to avoid barriers, as their values will be revisited
+** by the thread or by 'remarkupvals'.  Other objects are added to the
+** gray list to be visited (and turned black) later.  Both userdata and
+** upvalues can call this function recursively, but this recursion goes
+** for at most two levels: An upvalue cannot refer to another upvalue
+** (only closures can), and a userdata's metatable must be a table.
 */
 static void reallymarkobject (global_State *g, GCObject *o) {
-  white2gray(o);
  switch (o->tt) {
    case LUA_VSHRSTR:
    case LUA_VLNGSTR: {
-      gray2black(o);
+      set2black(o);  /* nothing to visit */
      break;
    }
    case LUA_VUPVAL: {
      UpVal *uv = gco2upv(o);
-      if (!upisopen(uv))  /* open upvalues are kept gray */
-        gray2black(o);
+      if (upisopen(uv))
+        set2gray(uv);  /* open upvalues are kept gray */
+      else
+        set2black(uv);  /* closed upvalues are visited here */
      markvalue(g, uv->v);  /* mark its content */
      break;
    }
@ -284,14 +308,14 @@ static void reallymarkobject (global_State *g, GCObject *o) {
      Udata *u = gco2u(o);
      if (u->nuvalue == 0) {  /* no user values? */
        markobjectN(g, u->metatable);  /* mark its metatable */
-        gray2black(o);  /* nothing else to mark */
+        set2black(u);  /* nothing else to mark */
        break;
      }
      /* else... */
    }  /* FALLTHROUGH */
    case LUA_VLCL: case LUA_VCCL: case LUA_VTABLE:
    case LUA_VTHREAD: case LUA_VPROTO: {
-      linkobjgclist(o, g->gray);
+      linkobjgclist(o, g->gray);  /* to be visited later */
      break;
    }
    default: lua_assert(0); break;
@ -324,41 +348,54 @@ static lu_mem markbeingfnz (global_State *g) {


 /*
-** Mark all values stored in marked open upvalues from non-marked threads.
-** (Values from marked threads were already marked when traversing the
-** thread.) Remove from the list threads that no longer have upvalues and
-** not-marked threads.
+** For each non-marked thread, simulates a barrier between each open
+** upvalue and its value. (If the thread is collected, the value will be
+** assigned to the upvalue, but then it can be too late for the barrier
+** to act. The "barrier" does not need to check colors: A non-marked
+** thread must be young; upvalues cannot be older than their threads; so
+** any visited upvalue must be young too.) Also removes the thread from
+** the list, as it was already visited. Removes also threads with no
+** upvalues, as they have nothing to be checked. (If the thread gets an
+** upvalue later, it will be linked in the list again.)
 */
 static int remarkupvals (global_State *g) {
  lua_State *thread;
  lua_State **p = &g->twups;
-  int work = 0;
+  int work = 0;  /* estimate of how much work was done here */
  while ((thread = *p) != NULL) {
    work++;
-    lua_assert(!isblack(thread));  /* threads are never black */
-    if (isgray(thread) && thread->openupval != NULL)
+    if (!iswhite(thread) && thread->openupval != NULL)
      p = &thread->twups;  /* keep marked thread with upvalues in the list */
    else {  /* thread is not marked or without upvalues */
      UpVal *uv;
+      lua_assert(!isold(thread) || thread->openupval == NULL);
      *p = thread->twups;  /* remove thread from the list */
      thread->twups = thread;  /* mark that it is out of list */
      for (uv = thread->openupval; uv != NULL; uv = uv->u.open.next) {
+        lua_assert(getage(uv) <= getage(thread));
        work++;
-        if (!iswhite(uv))  /* upvalue already visited? */
+        if (!iswhite(uv)) {  /* upvalue already visited? */
+          lua_assert(upisopen(uv) && isgray(uv));
          markvalue(g, uv->v);  /* mark its value */
        }
      }
    }
+  }
  return work;
 }


+static void cleargraylists (global_State *g) {
+  g->gray = g->grayagain = NULL;
+  g->weak = g->allweak = g->ephemeron = NULL;
+}
+
+
 /*
 ** mark root set and reset all gray lists, to start a new collection
 */
 static void restartcollection (global_State *g) {
-  g->gray = g->grayagain = NULL;
-  g->weak = g->allweak = g->ephemeron = NULL;
+  cleargraylists(g);
  markobject(g, g->mainthread);
  markvalue(g, &g->l_registry);
  markmt(g);
@ -374,6 +411,26 @@ static void restartcollection (global_State *g) {
 ** =======================================================
 */

+
+/*
+** Check whether object 'o' should be kept in the 'grayagain' list for
+** post-processing by 'correctgraylist'. (It could put all old objects
+** in the list and leave all the work to 'correctgraylist', but it is
+** more efficient to avoid adding elements that will be removed.) Only
+** TOUCHED1 objects need to be in the list. TOUCHED2 doesn't need to go
+** back to a gray list, but then it must become OLD. (That is what
+** 'correctgraylist' does when it finds a TOUCHED2 object.)
+*/
+static void genlink (global_State *g, GCObject *o) {
+  lua_assert(isblack(o));
+  if (getage(o) == G_TOUCHED1) {  /* touched in this cycle? */
+    linkobjgclist(o, g->grayagain);  /* link it back in 'grayagain' */
+  }  /* everything else do not need to be linked back */
+  else if (getage(o) == G_TOUCHED2)
+    changeage(o, G_TOUCHED2, G_OLD);  /* advance age */
+}
+
+
 /*
 ** Traverse a table with weak values and link it to proper list. During
 ** propagate phase, keep it in 'grayagain' list, to be revisited in the
@ -410,8 +467,9 @@ static void traverseweakvalue (global_State *g, Table *h) {
 ** the atomic phase, if table has any white->white entry, it has to
 ** be revisited during ephemeron convergence (as that key may turn
 ** black). Otherwise, if it has any white key, table has to be cleared
-** (in the atomic phase). In generational mode, it (like all visited
-** tables) must be kept in some gray list for post-processing.
+** (in the atomic phase). In generational mode, some tables
+** must be kept in some gray list for post-processing; this is done
+** by 'genlink'.
 */
 static int traverseephemeron (global_State *g, Table *h, int inv) {
  int marked = 0;  /* true if an object is marked in this traversal */
@ -450,10 +508,8 @@ static int traverseephemeron (global_State *g, Table *h, int inv) {
    linkgclist(h, g->ephemeron);  /* have to propagate again */
  else if (hasclears)  /* table has white keys? */
    linkgclist(h, g->allweak);  /* may have to clean white keys */
-  else if (g->gckind == KGC_GEN)
-    linkgclist(h, g->grayagain);  /* keep it in some list */
  else
-    gray2black(h);
+    genlink(g, obj2gco(h));  /* check whether collector still needs to see it */
  return marked;
 }

@ -473,10 +529,7 @@ static void traversestrongtable (global_State *g, Table *h) {
      markvalue(g, gval(n));
    }
  }
-  if (g->gckind == KGC_GEN) {
-    linkgclist(h, g->grayagain);  /* keep it in some gray list */
-    black2gray(h);
-  }
+  genlink(g, obj2gco(h));
 }


@ -488,7 +541,6 @@ static lu_mem traversetable (global_State *g, Table *h) {
      (cast_void(weakkey = strchr(svalue(mode), 'k')),
       cast_void(weakvalue = strchr(svalue(mode), 'v')),
       (weakkey || weakvalue))) {  /* is really weak? */
-    black2gray(h);  /* keep table gray */
    if (!weakkey)  /* strong keys? */
      traverseweakvalue(g, h);
    else if (!weakvalue)  /* strong values? */
@ -507,10 +559,7 @@ static int traverseudata (global_State *g, Udata *u) {
  markobjectN(g, u->metatable);  /* mark its metatable */
  for (i = 0; i < u->nuvalue; i++)
    markvalue(g, &u->uv[i].uv);
-  if (g->gckind == KGC_GEN) {
-    linkgclist(u, g->grayagain);  /* keep it in some gray list */
-    black2gray(u);
-  }
+  genlink(g, obj2gco(u));
  return 1 + u->nuvalue;
 }

@ -559,12 +608,21 @@ static int traverseLclosure (global_State *g, LClosure *cl) {

 /*
 ** Traverse a thread, marking the elements in the stack up to its top
-** and cleaning the rest of the stack in the final traversal.
-** That ensures that the entire stack have valid (non-dead) objects.
+** and cleaning the rest of the stack in the final traversal. That
+** ensures that the entire stack have valid (non-dead) objects.
+** Threads have no barriers. In gen. mode, old threads must be visited
+** at every cycle, because they might point to young objects.  In inc.
+** mode, the thread can still be modified before the end of the cycle,
+** and therefore it must be visited again in the atomic phase. To ensure
+** these visits, threads must return to a gray list if they are not new
+** (which can only happen in generational mode) or if the traverse is in
+** the propagate phase (which can only happen in incremental mode).
 */
 static int traversethread (global_State *g, lua_State *th) {
  UpVal *uv;
  StkId o = th->stack;
+  if (isold(th) || g->gcstate == GCSpropagate)
+    linkgclist(th, g->grayagain);  /* insert into 'grayagain' list */
  if (o == NULL)
    return 1;  /* stack not completely built yet */
  lua_assert(g->gcstate == GCSatomic ||
@ -574,9 +632,8 @@ static int traversethread (global_State *g, lua_State *th) {
  for (uv = th->openupval; uv != NULL; uv = uv->u.open.next)
    markobject(g, uv);  /* open upvalues cannot be collected */
  if (g->gcstate == GCSatomic) {  /* final traversal? */
-    StkId lim = th->stack + th->stacksize;  /* real end of stack */
-    for (; o < lim; o++)  /* clear not-marked stack slice */
-      setnilvalue(s2v(o));
+    for (; o < th->stack_last + EXTRA_STACK; o++)
+      setnilvalue(s2v(o));  /* clear dead stack slice */
    /* 'remarkupvals' may have removed thread from 'twups' list */
    if (!isintwups(th) && th->openupval != NULL) {
      th->twups = g->twups;  /* link it back to the list */
@ -585,17 +642,16 @@ static int traversethread (global_State *g, lua_State *th) {
  }
  else if (!g->gcemergency)
    luaD_shrinkstack(th); /* do not change stack in emergency cycle */
-  return 1 + th->stacksize;
+  return 1 + stacksize(th);
 }


 /*
-** traverse one gray object, turning it to black (except for threads,
-** which are always gray).
+** traverse one gray object, turning it to black.
 */
 static lu_mem propagatemark (global_State *g) {
  GCObject *o = g->gray;
-  gray2black(o);
+  nw2black(o);
  g->gray = *getgclist(o);  /* remove from 'gray' list */
  switch (o->tt) {
    case LUA_VTABLE: return traversetable(g, gco2t(o));
@ -603,12 +659,7 @@ static lu_mem propagatemark (global_State *g) {
    case LUA_VLCL: return traverseLclosure(g, gco2lcl(o));
    case LUA_VCCL: return traverseCclosure(g, gco2ccl(o));
    case LUA_VPROTO: return traverseproto(g, gco2p(o));
-    case LUA_VTHREAD: {
-      lua_State *th = gco2th(o);
-      linkgclist(th, g->grayagain);  /* insert into 'grayagain' list */
-      black2gray(o);
-      return traversethread(g, th);
-    }
+    case LUA_VTHREAD: return traversethread(g, gco2th(o));
    default: lua_assert(0); return 0;
  }
 }
@ -638,8 +689,10 @@ static void convergeephemerons (global_State *g) {
    g->ephemeron = NULL;  /* tables may return to this list when traversed */
    changed = 0;
    while ((w = next) != NULL) {  /* for each ephemeron table */
-      next = gco2t(w)->gclist;  /* list is rebuilt during loop */
-      if (traverseephemeron(g, gco2t(w), dir)) {  /* marked some value? */
+      Table *h = gco2t(w);
+      next = h->gclist;  /* list is rebuilt during loop */
+      nw2black(h);  /* out of the list (for now) */
+      if (traverseephemeron(g, h, dir)) {  /* marked some value? */
        propagateall(g);  /* propagate changes */
        changed = 1;  /* will have to revisit all ephemeron tables */
      }
@ -716,12 +769,16 @@ static void freeobj (lua_State *L, GCObject *o) {
    case LUA_VUPVAL:
      freeupval(L, gco2upv(o));
      break;
-    case LUA_VLCL:
-      luaM_freemem(L, o, sizeLclosure(gco2lcl(o)->nupvalues));
+    case LUA_VLCL: {
+      LClosure *cl = gco2lcl(o);
+      luaM_freemem(L, cl, sizeLclosure(cl->nupvalues));
      break;
-    case LUA_VCCL:
-      luaM_freemem(L, o, sizeCclosure(gco2ccl(o)->nupvalues));
+    }
+    case LUA_VCCL: {
+      CClosure *cl = gco2ccl(o);
+      luaM_freemem(L, cl, sizeCclosure(cl->nupvalues));
      break;
+    }
    case LUA_VTABLE:
      luaH_free(L, gco2t(o));
      break;
@ -733,13 +790,17 @@ static void freeobj (lua_State *L, GCObject *o) {
      luaM_freemem(L, o, sizeudata(u->nuvalue, u->len));
      break;
    }
-    case LUA_VSHRSTR:
-      luaS_remove(L, gco2ts(o));  /* remove it from hash table */
-      luaM_freemem(L, o, sizelstring(gco2ts(o)->shrlen));
+    case LUA_VSHRSTR: {
+      TString *ts = gco2ts(o);
+      luaS_remove(L, ts);  /* remove it from hash table */
+      luaM_freemem(L, ts, sizelstring(ts->shrlen));
      break;
-    case LUA_VLNGSTR:
-      luaM_freemem(L, o, sizelstring(gco2ts(o)->u.lnglen));
+    }
+    case LUA_VLNGSTR: {
+      TString *ts = gco2ts(o);
+      luaM_freemem(L, ts, sizelstring(ts->u.lnglen));
      break;
+    }
    default: lua_assert(0);
  }
 }
@ -766,7 +827,7 @@ static GCObject **sweeplist (lua_State *L, GCObject **p, int countin,
      freeobj(L, curr);  /* erase 'curr' */
    }
    else {  /* change mark to 'white' */
-      curr->marked = cast_byte((marked & maskcolors) | white);
+      curr->marked = cast_byte((marked & ~maskgcbits) | white);
      p = &curr->next;  /* go to next element */
    }
  }
@ -823,6 +884,8 @@ static GCObject *udata2finalize (global_State *g) {
  resetbit(o->marked, FINALIZEDBIT);  /* object is "normal" again */
  if (issweepphase(g))
    makewhite(g, o);  /* "sweep" object */
+  else if (getage(o) == G_OLD1)
+    g->firstold1 = o;  /* it is the first OLD1 object in the list */
  return o;
 }

@ -896,15 +959,15 @@ static GCObject **findlast (GCObject **p) {
 /*
 ** Move all unreachable objects (or 'all' objects) that need
 ** finalization from list 'finobj' to list 'tobefnz' (to be finalized).
-** (Note that objects after 'finobjold' cannot be white, so they
-** don't need to be traversed. In incremental mode, 'finobjold' is NULL,
+** (Note that objects after 'finobjold1' cannot be white, so they
+** don't need to be traversed. In incremental mode, 'finobjold1' is NULL,
 ** so the whole list is traversed.)
 */
 static void separatetobefnz (global_State *g, int all) {
  GCObject *curr;
  GCObject **p = &g->finobj;
  GCObject **lastnext = findlast(&g->tobefnz);
-  while ((curr = *p) != g->finobjold) {  /* traverse all finalizable objects */
+  while ((curr = *p) != g->finobjold1) {  /* traverse all finalizable objects */
    lua_assert(tofinalize(curr));
    if (!(iswhite(curr) || all))  /* not being collected? */
      p = &curr->next;  /* don't bother with it */
@ -920,6 +983,27 @@ static void separatetobefnz (global_State *g, int all) {
 }


+/*
+** If pointer 'p' points to 'o', move it to the next element.
+*/
+static void checkpointer (GCObject **p, GCObject *o) {
+  if (o == *p)
+    *p = o->next;
+}
+
+
+/*
+** Correct pointers to objects inside 'allgc' list when
+** object 'o' is being removed from the list.
+*/
+static void correctpointers (global_State *g, GCObject *o) {
+  checkpointer(&g->survival, o);
+  checkpointer(&g->old1, o);
+  checkpointer(&g->reallyold, o);
+  checkpointer(&g->firstold1, o);
+}
+
+
 /*
 ** if object 'o' has a finalizer, remove it from 'allgc' list (must
 ** search the list to find it) and link it in 'finobj' list.
@ -936,14 +1020,8 @@ void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt) {
      if (g->sweepgc == &o->next)  /* should not remove 'sweepgc' object */
        g->sweepgc = sweeptolive(L, g->sweepgc);  /* change 'sweepgc' */
    }
-    else {  /* correct pointers into 'allgc' list, if needed */
-      if (o == g->survival)
-        g->survival = o->next;
-      if (o == g->old)
-        g->old = o->next;
-      if (o == g->reallyold)
-        g->reallyold = o->next;
-    }
+    else
+      correctpointers(g, o);
    /* search for pointer pointing to 'o' */
    for (p = &g->allgc; *p != o; p = &(*p)->next) { /* empty */ }
    *p = o->next;  /* remove 'o' from 'allgc' list */
@ -965,24 +1043,31 @@ void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt) {
 static void setpause (global_State *g);


-/* mask to erase all color bits, not changing gen-related stuff */
-#define maskgencolors	(~(bitmask(BLACKBIT) | WHITEBITS))
-
-
 /*
-** Sweep a list of objects, deleting dead ones and turning
-** the non dead to old (without changing their colors).
+** Sweep a list of objects to enter generational mode.  Deletes dead
+** objects and turns the non dead to old. All non-dead threads---which
+** are now old---must be in a gray list. Everything else is not in a
+** gray list. Open upvalues are also kept gray.
 */
 static void sweep2old (lua_State *L, GCObject **p) {
  GCObject *curr;
+  global_State *g = G(L);
  while ((curr = *p) != NULL) {
    if (iswhite(curr)) {  /* is 'curr' dead? */
-      lua_assert(isdead(G(L), curr));
+      lua_assert(isdead(g, curr));
      *p = curr->next;  /* remove 'curr' from list */
      freeobj(L, curr);  /* erase 'curr' */
    }
    else {  /* all surviving objects become old */
      setage(curr, G_OLD);
+      if (curr->tt == LUA_VTHREAD) {  /* threads must be watched */
+        lua_State *th = gco2th(curr);
+        linkgclist(th, g->grayagain);  /* insert into 'grayagain' list */
+      }
+      else if (curr->tt == LUA_VUPVAL && upisopen(gco2upv(curr)))
+        set2gray(curr);  /* open upvalues are always gray */
+      else  /* everything else is black */
+        nw2black(curr);
      p = &curr->next;  /* go to next element */
    }
  }
@ -995,9 +1080,13 @@ static void sweep2old (lua_State *L, GCObject **p) {
 ** during the sweep. So, any white object must be dead.) For
 ** non-dead objects, advance their ages and clear the color of
 ** new objects. (Old objects keep their colors.)
+** The ages of G_TOUCHED1 and G_TOUCHED2 objects cannot be advanced
+** here, because these old-generation objects are usually not swept
+** here.  They will all be advanced in 'correctgraylist'. That function
+** will also remove objects turned white here from any gray list.
 */
 static GCObject **sweepgen (lua_State *L, global_State *g, GCObject **p,
-                            GCObject *limit) {
+                            GCObject *limit, GCObject **pfirstold1) {
  static const lu_byte nextage[] = {
    G_SURVIVAL,  /* from G_NEW */
    G_OLD1,      /* from G_SURVIVAL */
@ -1016,9 +1105,15 @@ static GCObject **sweepgen (lua_State *L, global_State *g, GCObject **p,
      freeobj(L, curr);  /* erase 'curr' */
    }
    else {  /* correct mark and age */
-      if (getage(curr) == G_NEW)
-        curr->marked = cast_byte((curr->marked & maskgencolors) | white);
+      if (getage(curr) == G_NEW) {  /* new objects go back to white */
+        int marked = curr->marked & ~maskgcbits;  /* erase GC bits */
+        curr->marked = cast_byte(marked | G_SURVIVAL | white);
+      }
+      else {  /* all other objects will be old, and so keep their color */
        setage(curr, nextage[getage(curr)]);
+        if (getage(curr) == G_OLD1 && *pfirstold1 == NULL)
+          *pfirstold1 = curr;  /* first OLD1 object in the list */
+      }
      p = &curr->next;  /* go to next element */
    }
  }
@ -1028,58 +1123,50 @@ static GCObject **sweepgen (lua_State *L, global_State *g, GCObject **p,

 /*
 ** Traverse a list making all its elements white and clearing their
-** age.
+** age. In incremental mode, all objects are 'new' all the time,
+** except for fixed strings (which are always old).
 */
 static void whitelist (global_State *g, GCObject *p) {
  int white = luaC_white(g);
  for (; p != NULL; p = p->next)
-    p->marked = cast_byte((p->marked & maskcolors) | white);
+    p->marked = cast_byte((p->marked & ~maskgcbits) | white);
 }


 /*
-** Correct a list of gray objects.
+** Correct a list of gray objects. Return pointer to where rest of the
+** list should be linked.
 ** Because this correction is done after sweeping, young objects might
 ** be turned white and still be in the list. They are only removed.
-** For tables and userdata, advance 'touched1' to 'touched2'; 'touched2'
-** objects become regular old and are removed from the list.
-** For threads, just remove white ones from the list.
+** 'TOUCHED1' objects are advanced to 'TOUCHED2' and remain on the list;
+** Non-white threads also remain on the list; 'TOUCHED2' objects become
+** regular old; they and anything else are removed from the list.
 */
 static GCObject **correctgraylist (GCObject **p) {
  GCObject *curr;
  while ((curr = *p) != NULL) {
-    switch (curr->tt) {
-      case LUA_VTABLE: case LUA_VUSERDATA: {
    GCObject **next = getgclist(curr);
-        if (getage(curr) == G_TOUCHED1) {  /* touched in this cycle? */
+    if (iswhite(curr))
+      goto remove;  /* remove all white objects */
+    else if (getage(curr) == G_TOUCHED1) {  /* touched in this cycle? */
      lua_assert(isgray(curr));
-          gray2black(curr);  /* make it black, for next barrier */
+      nw2black(curr);  /* make it black, for next barrier */
      changeage(curr, G_TOUCHED1, G_TOUCHED2);
-          p = next;  /* go to next element */
+      goto remain;  /* keep it in the list and go to next element */
    }
-        else {  /* not touched in this cycle */
-          if (!iswhite(curr)) {  /* not white? */
-            lua_assert(isold(curr));
-            if (getage(curr) == G_TOUCHED2)  /* advance from G_TOUCHED2... */
-              changeage(curr, G_TOUCHED2, G_OLD);  /* ... to G_OLD */
-            gray2black(curr);  /* make it black */
+    else if (curr->tt == LUA_VTHREAD) {
+      lua_assert(isgray(curr));
+      goto remain;  /* keep non-white threads on the list */
    }
-          /* else, object is white: just remove it from this list */
-          *p = *next;  /* remove 'curr' from gray list */
-        }
-        break;
-      }
-      case LUA_VTHREAD: {
-        lua_State *th = gco2th(curr);
-        lua_assert(!isblack(th));
-        if (iswhite(th))  /* new object? */
-          *p = th->gclist;  /* remove from gray list */
-        else  /* old threads remain gray */
-          p = &th->gclist;  /* go to next element */
-        break;
-      }
-      default: lua_assert(0);  /* nothing more could be gray here */
+    else {  /* everything else is removed */
+      lua_assert(isold(curr));  /* young objects should be white here */
+      if (getage(curr) == G_TOUCHED2)  /* advance from TOUCHED2... */
+        changeage(curr, G_TOUCHED2, G_OLD);  /* ... to OLD */
+      nw2black(curr);  /* make object black (to be removed) */
+      goto remove;
    }
+    remove: *p = *next; continue;
+    remain: p = next; continue;
  }
  return p;
 }
@ -1100,7 +1187,7 @@ static void correctgraylists (global_State *g) {


 /*
-** Mark 'OLD1' objects when starting a new young collection.
+** Mark black 'OLD1' objects when starting a new young collection.
 ** Gray objects are already in some gray list, and so will be visited
 ** in the atomic step.
 */
@ -1109,13 +1196,12 @@ static void markold (global_State *g, GCObject *from, GCObject *to) {
  for (p = from; p != to; p = p->next) {
    if (getage(p) == G_OLD1) {
      lua_assert(!iswhite(p));
-      if (isblack(p)) {
-        black2gray(p);  /* should be '2white', but gray works too */
+      changeage(p, G_OLD1, G_OLD);  /* now they are old */
+      if (isblack(p))
        reallymarkobject(g, p);
    }
  }
 }
-}


 /*
@ -1131,50 +1217,63 @@ static void finishgencycle (lua_State *L, global_State *g) {


 /*
-** Does a young collection. First, mark 'OLD1' objects.  (Only survival
-** and "recent old" lists can contain 'OLD1' objects. New lists cannot
-** contain 'OLD1' objects, at most 'OLD0' objects that were already
-** visited when marked old.) Then does the atomic step. Then,
-** sweep all lists and advance pointers. Finally, finish the collection.
+** Does a young collection. First, mark 'OLD1' objects. Then does the
+** atomic step. Then, sweep all lists and advance pointers. Finally,
+** finish the collection.
 */
 static void youngcollection (lua_State *L, global_State *g) {
  GCObject **psurvival;  /* to point to first non-dead survival object */
+  GCObject *dummy;  /* dummy out parameter to 'sweepgen' */
  lua_assert(g->gcstate == GCSpropagate);
-  markold(g, g->survival, g->reallyold);
+  if (g->firstold1) {  /* are there regular OLD1 objects? */
+    markold(g, g->firstold1, g->reallyold);  /* mark them */
+    g->firstold1 = NULL;  /* no more OLD1 objects (for now) */
+  }
  markold(g, g->finobj, g->finobjrold);
+  markold(g, g->tobefnz, NULL);
  atomic(L);

  /* sweep nursery and get a pointer to its last live element */
-  psurvival = sweepgen(L, g, &g->allgc, g->survival);
-  /* sweep 'survival' and 'old' */
-  sweepgen(L, g, psurvival, g->reallyold);
-  g->reallyold = g->old;
-  g->old = *psurvival;  /* 'survival' survivals are old now */
+  g->gcstate = GCSswpallgc;
+  psurvival = sweepgen(L, g, &g->allgc, g->survival, &g->firstold1);
+  /* sweep 'survival' */
+  sweepgen(L, g, psurvival, g->old1, &g->firstold1);
+  g->reallyold = g->old1;
+  g->old1 = *psurvival;  /* 'survival' survivals are old now */
  g->survival = g->allgc;  /* all news are survivals */

  /* repeat for 'finobj' lists */
-  psurvival = sweepgen(L, g, &g->finobj, g->finobjsur);
-  /* sweep 'survival' and 'old' */
-  sweepgen(L, g, psurvival, g->finobjrold);
-  g->finobjrold = g->finobjold;
-  g->finobjold = *psurvival;  /* 'survival' survivals are old now */
+  dummy = NULL;  /* no 'firstold1' optimization for 'finobj' lists */
+  psurvival = sweepgen(L, g, &g->finobj, g->finobjsur, &dummy);
+  /* sweep 'survival' */
+  sweepgen(L, g, psurvival, g->finobjold1, &dummy);
+  g->finobjrold = g->finobjold1;
+  g->finobjold1 = *psurvival;  /* 'survival' survivals are old now */
  g->finobjsur = g->finobj;  /* all news are survivals */

-  sweepgen(L, g, &g->tobefnz, NULL);
-
+  sweepgen(L, g, &g->tobefnz, NULL, &dummy);
  finishgencycle(L, g);
 }


+/*
+** Clears all gray lists, sweeps objects, and prepare sublists to enter
+** generational mode. The sweeps remove dead objects and turn all
+** surviving objects to old. Threads go back to 'grayagain'; everything
+** else is turned black (not in any gray list).
+*/
 static void atomic2gen (lua_State *L, global_State *g) {
+  cleargraylists(g);
  /* sweep all elements making them old */
+  g->gcstate = GCSswpallgc;
  sweep2old(L, &g->allgc);
  /* everything alive now is old */
-  g->reallyold = g->old = g->survival = g->allgc;
+  g->reallyold = g->old1 = g->survival = g->allgc;
+  g->firstold1 = NULL;  /* there are no OLD1 objects anywhere */

  /* repeat for 'finobj' lists */
  sweep2old(L, &g->finobj);
-  g->finobjrold = g->finobjold = g->finobjsur = g->finobj;
+  g->finobjrold = g->finobjold1 = g->finobjsur = g->finobj;

  sweep2old(L, &g->tobefnz);

@ -1187,8 +1286,9 @@ static void atomic2gen (lua_State *L, global_State *g) {

 /*
 ** Enter generational mode. Must go until the end of an atomic cycle
-** to ensure that all threads and weak tables are in the gray lists.
-** Then, turn all objects into old and finishes the collection.
+** to ensure that all objects are correctly marked and weak tables
+** are cleared. Then, turn all objects into old and finishes the
+** collection.
 */
 static lu_mem entergen (lua_State *L, global_State *g) {
  lu_mem numobjs;
@ -1207,10 +1307,10 @@ static lu_mem entergen (lua_State *L, global_State *g) {
 */
 static void enterinc (global_State *g) {
  whitelist(g, g->allgc);
-  g->reallyold = g->old = g->survival = NULL;
+  g->reallyold = g->old1 = g->survival = NULL;
  whitelist(g, g->finobj);
  whitelist(g, g->tobefnz);
-  g->finobjrold = g->finobjold = g->finobjsur = NULL;
+  g->finobjrold = g->finobjold1 = g->finobjsur = NULL;
  g->gcstate = GCSpause;
  g->gckind = KGC_INC;
  g->lastatomic = 0;
--- a/lua-5.4.2/src/lgc.h
+++ b/lua-5.4.2/src/lgc.h
@ -12,16 +12,16 @@
 #include "lstate.h"

 /*
-** Collectable objects may have one of three colors: white, which
-** means the object is not marked; gray, which means the
-** object is marked, but its references may be not marked; and
-** black, which means that the object and all its references are marked.
-** The main invariant of the garbage collector, while marking objects,
-** is that a black object can never point to a white one. Moreover,
-** any gray object must be in a "gray list" (gray, grayagain, weak,
-** allweak, ephemeron) so that it can be visited again before finishing
-** the collection cycle. These lists have no meaning when the invariant
-** is not being enforced (e.g., sweep phase).
+** Collectable objects may have one of three colors: white, which means
+** the object is not marked; gray, which means the object is marked, but
+** its references may be not marked; and black, which means that the
+** object and all its references are marked.  The main invariant of the
+** garbage collector, while marking objects, is that a black object can
+** never point to a white one. Moreover, any gray object must be in a
+** "gray list" (gray, grayagain, weak, allweak, ephemeron) so that it
+** can be visited again before finishing the collection cycle. (Open
+** upvalues are an exception to this rule.)  These lists have no meaning
+** when the invariant is not being enforced (e.g., sweep phase).
 */


@ -69,14 +69,16 @@

 /*
 ** Layout for bit use in 'marked' field. First three bits are
-** used for object "age" in generational mode. Last bit is free
-** to be used by respective objects.
+** used for object "age" in generational mode. Last bit is used
+** by tests.
 */
 #define WHITE0BIT	3  /* object is white (type 0) */
 #define WHITE1BIT	4  /* object is white (type 1) */
 #define BLACKBIT	5  /* object is black */
 #define FINALIZEDBIT	6  /* object has been marked for finalization */

+#define TESTBIT		7
+


 #define WHITEBITS	bit2mask(WHITE0BIT, WHITE1BIT)
@ -94,7 +96,8 @@
 #define isdead(g,v)	isdeadm(otherwhite(g), (v)->marked)

 #define changewhite(x)	((x)->marked ^= WHITEBITS)
-#define gray2black(x)	l_setbit((x)->marked, BLACKBIT)
+#define nw2black(x)  \
+	check_exp(!iswhite(x), l_setbit((x)->marked, BLACKBIT))

 #define luaC_white(g)	cast_byte((g)->currentwhite & WHITEBITS)

--- a/lua-5.4.2/src/linit.c
+++ b/lua-5.4.2/src/linit.c
--- a/lua-5.4.2/src/liolib.c
+++ b/lua-5.4.2/src/liolib.c
@ -52,6 +52,12 @@ static int l_checkmode (const char *mode) {
 ** =======================================================
 */

+#if !defined(l_checkmodep)
+/* By default, Lua accepts only "r" or "w" as mode */
+#define l_checkmodep(m)	((m[0] == 'r' || m[0] == 'w') && m[1] == '\0')
+#endif
+
+
 #if !defined(l_popen)		/* { */

 #if defined(LUA_USE_POSIX)	/* { */
@ -279,6 +285,7 @@ static int io_popen (lua_State *L) {
  const char *filename = luaL_checkstring(L, 1);
  const char *mode = luaL_optstring(L, 2, "r");
  LStream *p = newprefile(L);
+  luaL_argcheck(L, l_checkmodep(mode), 2, "invalid mode");
  p->f = l_popen(L, filename, mode);
  p->closef = &io_pclose;
  return (p->f == NULL) ? luaL_fileresult(L, 0, filename) : 1;
--- a/lua-5.4.2/src/ljumptab.h
+++ b/lua-5.4.2/src/ljumptab.h
--- a/lua-5.4.2/src/llex.c
+++ b/lua-5.4.2/src/llex.c
@ -81,7 +81,6 @@ void luaX_init (lua_State *L) {

 const char *luaX_token2str (LexState *ls, int token) {
  if (token < FIRST_RESERVED) {  /* single-byte symbols? */
-    lua_assert(token == cast_uchar(token));
    if (lisprint(token))
      return luaO_pushfstring(ls->L, "'%c'", token);
    else  /* control character */
@ -255,9 +254,10 @@ static int read_numeral (LexState *ls, SemInfo *seminfo) {


 /*
-** reads a sequence '[=*[' or ']=*]', leaving the last bracket.
-** If sequence is well formed, return its number of '='s + 2; otherwise,
-** return 1 if there is no '='s or 0 otherwise (an unfinished '[==...').
+** read a sequence '[=*[' or ']=*]', leaving the last bracket. If
+** sequence is well formed, return its number of '='s + 2; otherwise,
+** return 1 if it is a single bracket (no '='s and no 2nd bracket);
+** otherwise (an unfinished '[==...') return 0.
 */
 static size_t skip_sep (LexState *ls) {
  size_t count = 0;
@ -482,34 +482,34 @@ static int llex (LexState *ls, SemInfo *seminfo) {
      }
      case '=': {
        next(ls);
-        if (check_next1(ls, '=')) return TK_EQ;
+        if (check_next1(ls, '=')) return TK_EQ;  /* '==' */
        else return '=';
      }
      case '<': {
        next(ls);
-        if (check_next1(ls, '=')) return TK_LE;
-        else if (check_next1(ls, '<')) return TK_SHL;
+        if (check_next1(ls, '=')) return TK_LE;  /* '<=' */
+        else if (check_next1(ls, '<')) return TK_SHL;  /* '<<' */
        else return '<';
      }
      case '>': {
        next(ls);
-        if (check_next1(ls, '=')) return TK_GE;
-        else if (check_next1(ls, '>')) return TK_SHR;
+        if (check_next1(ls, '=')) return TK_GE;  /* '>=' */
+        else if (check_next1(ls, '>')) return TK_SHR;  /* '>>' */
        else return '>';
      }
      case '/': {
        next(ls);
-        if (check_next1(ls, '/')) return TK_IDIV;
+        if (check_next1(ls, '/')) return TK_IDIV;  /* '//' */
        else return '/';
      }
      case '~': {
        next(ls);
-        if (check_next1(ls, '=')) return TK_NE;
+        if (check_next1(ls, '=')) return TK_NE;  /* '~=' */
        else return '~';
      }
      case ':': {
        next(ls);
-        if (check_next1(ls, ':')) return TK_DBCOLON;
+        if (check_next1(ls, ':')) return TK_DBCOLON;  /* '::' */
        else return ':';
      }
      case '"': case '\'': {  /* short literal strings */
@ -548,7 +548,7 @@ static int llex (LexState *ls, SemInfo *seminfo) {
            return TK_NAME;
          }
        }
-        else {  /* single-char tokens (+ - / ...) */
+        else {  /* single-char tokens ('+', '*', '%', '{', '}', ...) */
          int c = ls->current;
          next(ls);
          return c;
--- a/lua-5.4.2/src/llex.h
+++ b/lua-5.4.2/src/llex.h
@ -7,11 +7,17 @@
 #ifndef llex_h
 #define llex_h

+#include <limits.h>
+
 #include "lobject.h"
 #include "lzio.h"


-#define FIRST_RESERVED	257
+/*
+** Single-char tokens (terminal symbols) are represented by their own
+** numeric code. Other tokens start at the following value.
+*/
+#define FIRST_RESERVED	(UCHAR_MAX + 1)


 #if !defined(LUA_ENV)
--- a/lua-5.4.2/src/llimits.h
+++ b/lua-5.4.2/src/llimits.h
@ -84,7 +84,15 @@ typedef LUAI_UACNUMBER l_uacNumber;
 typedef LUAI_UACINT l_uacInt;


-/* internal assertions for in-house debugging */
+/*
+** Internal assertions for in-house debugging
+*/
+#if defined LUAI_ASSERT
+#undef NDEBUG
+#include <assert.h>
+#define lua_assert(c)           assert(c)
+#endif
+
 #if defined(lua_assert)
 #define check_exp(c,e)		(lua_assert(c), (e))
 /* to avoid problems with conditions too long */
@ -226,6 +234,17 @@ typedef l_uint32 Instruction;
 #endif


+/*
+** Maximum depth for nested C calls, syntactical nested non-terminals,
+** and other features implemented through recursion in C. (Value must
+** fit in a 16-bit unsigned integer. It must also be compatible with
+** the size of the C stack.)
+*/
+#if !defined(LUAI_MAXCCALLS)
+#define LUAI_MAXCCALLS		200
+#endif
+
+
 /*
 ** macros that are executed whenever program enters the Lua core
 ** ('lua_lock') and leaves the core ('lua_unlock')
@ -307,7 +326,8 @@ typedef l_uint32 Instruction;

 /* exponentiation */
 #if !defined(luai_numpow)
-#define luai_numpow(L,a,b)      ((void)L, l_mathop(pow)(a,b))
+#define luai_numpow(L,a,b)  \
+  ((void)L, (b == 2) ? (a)*(a) : l_mathop(pow)(a,b))
 #endif

 /* the others are quite standard operations */
@ -336,7 +356,7 @@ typedef l_uint32 Instruction;
 #else
 /* realloc stack keeping its size */
 #define condmovestack(L,pre,pos)  \
-  { int sz_ = (L)->stacksize; pre; luaD_reallocstack((L), sz_, 0); pos; }
+  { int sz_ = stacksize(L); pre; luaD_reallocstack((L), sz_, 0); pos; }
 #endif

 #if !defined(HARDMEMTESTS)
--- a/lua-5.4.2/src/lmathlib.c
+++ b/lua-5.4.2/src/lmathlib.c
--- a/lua-5.4.2/src/lmem.c
+++ b/lua-5.4.2/src/lmem.c
@ -22,7 +22,7 @@
 #include "lstate.h"


-#if defined(HARDMEMTESTS)
+#if defined(EMERGENCYGCTESTS)
 /*
 ** First allocation will fail whenever not building initial state
 ** and not shrinking a block. (This fail will trigger 'tryagain' and
--- a/lua-5.4.2/src/lmem.h
+++ b/lua-5.4.2/src/lmem.h
--- a/lua-5.4.2/src/loadlib.c
+++ b/lua-5.4.2/src/loadlib.c
--- a/lua-5.4.2/src/lobject.c
+++ b/lua-5.4.2/src/lobject.c
@ -215,37 +215,42 @@ static lua_Number lua_strx2number (const char *s, char **endptr) {
 /* }====================================================== */


-/* maximum length of a numeral */
+/* maximum length of a numeral to be converted to a number */
 #if !defined (L_MAXLENNUM)
 #define L_MAXLENNUM	200
 #endif

+/*
+** Convert string 's' to a Lua number (put in 'result'). Return NULL on
+** fail or the address of the ending '\0' on success. ('mode' == 'x')
+** means a hexadecimal numeral.
+*/
 static const char *l_str2dloc (const char *s, lua_Number *result, int mode) {
  char *endptr;
  *result = (mode == 'x') ? lua_strx2number(s, &endptr)  /* try to convert */
                          : lua_str2number(s, &endptr);
  if (endptr == s) return NULL;  /* nothing recognized? */
  while (lisspace(cast_uchar(*endptr))) endptr++;  /* skip trailing spaces */
-  return (*endptr == '\0') ? endptr : NULL;  /* OK if no trailing characters */
+  return (*endptr == '\0') ? endptr : NULL;  /* OK iff no trailing chars */
 }


 /*
-** Convert string 's' to a Lua number (put in 'result'). Return NULL
-** on fail or the address of the ending '\0' on success.
-** 'pmode' points to (and 'mode' contains) special things in the string:
-** - 'x'/'X' means a hexadecimal numeral
-** - 'n'/'N' means 'inf' or 'nan' (which should be rejected)
-** - '.' just optimizes the search for the common case (nothing special)
+** Convert string 's' to a Lua number (put in 'result') handling the
+** current locale.
 ** This function accepts both the current locale or a dot as the radix
 ** mark. If the conversion fails, it may mean number has a dot but
 ** locale accepts something else. In that case, the code copies 's'
 ** to a buffer (because 's' is read-only), changes the dot to the
 ** current locale radix mark, and tries to convert again.
+** The variable 'mode' checks for special characters in the string:
+** - 'n' means 'inf' or 'nan' (which should be rejected)
+** - 'x' means a hexadecimal numeral
+** - '.' just optimizes the search for the common case (no special chars)
 */
 static const char *l_str2d (const char *s, lua_Number *result) {
  const char *endptr;
-  const char *pmode = strpbrk(s, ".xXnN");
+  const char *pmode = strpbrk(s, ".xXnN");  /* look for special chars */
  int mode = pmode ? ltolower(cast_uchar(*pmode)) : 0;
  if (mode == 'n')  /* reject 'inf' and 'nan' */
    return NULL;
@ -253,7 +258,7 @@ static const char *l_str2d (const char *s, lua_Number *result) {
  if (endptr == NULL) {  /* failed? may be a different locale */
    char buff[L_MAXLENNUM + 1];
    const char *pdot = strchr(s, '.');
-    if (strlen(s) > L_MAXLENNUM || pdot == NULL)
+    if (pdot == NULL || strlen(s) > L_MAXLENNUM)
      return NULL;  /* string too long or no dot; fail */
    strcpy(buff, s);  /* copy string to buffer */
    buff[pdot - s] = lua_getlocaledecpoint();  /* correct decimal point */
@ -333,8 +338,15 @@ int luaO_utf8esc (char *buff, unsigned long x) {
 }


-/* maximum length of the conversion of a number to a string */
-#define MAXNUMBER2STR	50
+/*
+** Maximum length of the conversion of a number to a string. Must be
+** enough to accommodate both LUA_INTEGER_FMT and LUA_NUMBER_FMT.
+** (For a long long int, this is 19 digits plus a sign and a final '\0',
+** adding to 21. For a long double, it can go to a sign, 33 digits,
+** the dot, an exponent letter, an exponent sign, 5 exponent digits,
+** and a final '\0', adding to 43.)
+*/
+#define MAXNUMBER2STR	44


 /*
@ -375,7 +387,7 @@ void luaO_tostring (lua_State *L, TValue *obj) {
 */

 /* size for buffer space used by 'luaO_pushvfstring' */
-#define BUFVFS		400
+#define BUFVFS		200

 /* buffer used by 'luaO_pushvfstring' */
 typedef struct BuffFS {
@ -387,19 +399,17 @@ typedef struct BuffFS {


 /*
-** Push given string to the stack, as part of the buffer. If the stack
-** is almost full, join all partial strings in the stack into one.
+** Push given string to the stack, as part of the buffer, and
+** join the partial strings in the stack into one.
 */
 static void pushstr (BuffFS *buff, const char *str, size_t l) {
  lua_State *L = buff->L;
  setsvalue2s(L, L->top, luaS_newlstr(L, str, l));
  L->top++;  /* may use one extra slot */
  buff->pushed++;
-  if (buff->pushed > 1 && L->top + 1 >= L->stack_last) {
-    luaV_concat(L, buff->pushed);  /* join all partial results into one */
+  luaV_concat(L, buff->pushed);  /* join partial results into one */
  buff->pushed = 1;
 }
-}


 /*
@ -521,8 +531,7 @@ const char *luaO_pushvfstring (lua_State *L, const char *fmt, va_list argp) {
  }
  addstr2buff(&buff, fmt, strlen(fmt));  /* rest of 'fmt' */
  clearbuff(&buff);  /* empty buffer into the stack */
-  if (buff.pushed > 1)
-    luaV_concat(L, buff.pushed);  /* join all partial results */
+  lua_assert(buff.pushed == 1);
  return svalue(s2v(L->top - 1));
 }

--- a/lua-5.4.2/src/lobject.h
+++ b/lua-5.4.2/src/lobject.h
@ -21,10 +21,12 @@
 */
 #define LUA_TUPVAL	LUA_NUMTYPES  /* upvalues */
 #define LUA_TPROTO	(LUA_NUMTYPES+1)  /* function prototypes */
+#define LUA_TDEADKEY	(LUA_NUMTYPES+2)  /* removed keys in tables */
+


 /*
-** number of all possible types (including LUA_TNONE)
+** number of all possible types (including LUA_TNONE but excluding DEADKEY)
 */
 #define LUA_TOTALTYPES		(LUA_TPROTO + 2)

@ -96,7 +98,8 @@ typedef struct TValue {
 /*
 ** Any value being manipulated by the program either is non
 ** collectable, or the collectable object has the right tag
-** and it is not dead.
+** and it is not dead. The option 'L == NULL' allows other
+** macros using this one to be used where L is not available.
 */
 #define checkliveness(L,obj) \
 	((void)L, lua_longassert(!iscollectable(obj) || \
@ -554,7 +557,7 @@ typedef struct Proto {

 /*
 ** {==================================================================
-** Closures
+** Functions
 ** ===================================================================
 */

@ -703,9 +706,9 @@ typedef union Node {
 */

 #define BITRAS		(1 << 7)
-#define isrealasize(t)		(!((t)->marked & BITRAS))
-#define setrealasize(t)		((t)->marked &= cast_byte(~BITRAS))
-#define setnorealasize(t)	((t)->marked |= BITRAS)
+#define isrealasize(t)		(!((t)->flags & BITRAS))
+#define setrealasize(t)		((t)->flags &= cast_byte(~BITRAS))
+#define setnorealasize(t)	((t)->flags |= BITRAS)


 typedef struct Table {
@ -742,13 +745,13 @@ typedef struct Table {


 /*
-** Use a "nil table" to mark dead keys in a table. Those keys serve
-** to keep space for removed entries, which may still be part of
-** chains. Note that the 'keytt' does not have the BIT_ISCOLLECTABLE
-** set, so these values are considered not collectable and are different
-** from any valid value.
+** Dead keys in tables have the tag DEADKEY but keep their original
+** gcvalue. This distinguishes them from regular keys but allows them to
+** be found when searched in a special way. ('next' needs that to find
+** keys removed from a table during a traversal.)
 */
-#define setdeadkey(n)	(keytt(n) = LUA_TTABLE, gckey(n) = NULL)
+#define setdeadkey(node)	(keytt(node) = LUA_TDEADKEY)
+#define keyisdead(node)		(keytt(node) == LUA_TDEADKEY)

 /* }================================================================== */

--- a/lua-5.4.2/src/lopcodes.c
+++ b/lua-5.4.2/src/lopcodes.c
--- a/lua-5.4.2/src/lopcodes.h
+++ b/lua-5.4.2/src/lopcodes.h
@ -261,7 +261,7 @@ OP_MMBINK,/*	A B C k		call C metamethod over R[A] and K[B]	*/
 OP_UNM,/*	A B	R[A] := -R[B]					*/
 OP_BNOT,/*	A B	R[A] := ~R[B]					*/
 OP_NOT,/*	A B	R[A] := not R[B]				*/
-OP_LEN,/*	A B	R[A] := length of R[B]				*/
+OP_LEN,/*	A B	R[A] := #R[B] (length operator)			*/

 OP_CONCAT,/*	A B	R[A] := R[A].. ... ..R[A + B - 1]		*/

@ -297,7 +297,7 @@ OP_TFORPREP,/*	A Bx	create upvalue for R[A + 3]; pc+=Bx		*/
 OP_TFORCALL,/*	A C	R[A+4], ... ,R[A+3+C] := R[A](R[A+1], R[A+2]);	*/
 OP_TFORLOOP,/*	A Bx	if R[A+2] ~= nil then { R[A]=R[A+2]; pc -= Bx }	*/

-OP_SETLIST,/*	A B C k	R[A][(C-1)*FPF+i] := R[A+i], 1 <= i <= B	*/
+OP_SETLIST,/*	A B C k	R[A][C+i] := R[A+i], 1 <= i <= B		*/

 OP_CLOSURE,/*	A Bx	R[A] := closure(KPROTO[Bx])			*/

--- a/lua-5.4.2/src/lopnames.h
+++ b/lua-5.4.2/src/lopnames.h
--- a/lua-5.4.2/src/loslib.c
+++ b/lua-5.4.2/src/loslib.c
--- a/lua-5.4.2/src/lparser.c
+++ b/lua-5.4.2/src/lparser.c
@ -489,12 +489,10 @@ static void adjust_assign (LexState *ls, int nvars, int nexps, expdesc *e) {
 }


-/*
-** Macros to limit the maximum recursion depth while parsing
-*/
-#define enterlevel(ls)	luaE_enterCcall((ls)->L)
+#define enterlevel(ls)	luaE_incCstack(ls->L)

-#define leavelevel(ls)	luaE_exitCcall((ls)->L)
+
+#define leavelevel(ls) ((ls)->L->nCcalls--)


 /*
@ -947,7 +945,7 @@ static void setvararg (FuncState *fs, int nparams) {


 static void parlist (LexState *ls) {
-  /* parlist -> [ param { ',' param } ] */
+  /* parlist -> [ {NAME ','} (NAME | '...') ] */
  FuncState *fs = ls->fs;
  Proto *f = fs->f;
  int nparams = 0;
@ -955,12 +953,12 @@ static void parlist (LexState *ls) {
  if (ls->t.token != ')') {  /* is 'parlist' not empty? */
    do {
      switch (ls->t.token) {
-        case TK_NAME: {  /* param -> NAME */
+        case TK_NAME: {
          new_localvar(ls, str_checkname(ls));
          nparams++;
          break;
        }
-        case TK_DOTS: {  /* param -> '...' */
+        case TK_DOTS: {
          luaX_next(ls);
          isvararg = 1;
          break;
@ -1625,59 +1623,21 @@ static void forstat (LexState *ls, int line) {
 }


-/*
-** Check whether next instruction is a single jump (a 'break', a 'goto'
-** to a forward label, or a 'goto' to a backward label with no variable
-** to close). If so, set the name of the 'label' it is jumping to
-** ("break" for a 'break') or to where it is jumping to ('target') and
-** return true. If not a single jump, leave input unchanged, to be
-** handled as a regular statement.
-*/
-static int issinglejump (LexState *ls, TString **label, int *target) {
-  if (testnext(ls, TK_BREAK)) {  /* a break? */
-    *label = luaS_newliteral(ls->L, "break");
-    return 1;
-  }
-  else if (ls->t.token != TK_GOTO || luaX_lookahead(ls) != TK_NAME)
-    return 0;  /* not a valid goto */
-  else {
-    TString *lname = ls->lookahead.seminfo.ts;  /* label's id */
-    Labeldesc *lb = findlabel(ls, lname);
-    if (lb) {  /* a backward jump? */
-      /* does it need to close variables? */
-      if (luaY_nvarstack(ls->fs) > stacklevel(ls->fs, lb->nactvar))
-        return 0;  /* not a single jump; cannot optimize */
-      *target = lb->pc;
-    }
-    else  /* jump forward */
-      *label = lname;
-    luaX_next(ls);  /* skip goto */
-    luaX_next(ls);  /* skip name */
-    return 1;
-  }
-}
-
-
 static void test_then_block (LexState *ls, int *escapelist) {
  /* test_then_block -> [IF | ELSEIF] cond THEN block */
  BlockCnt bl;
-  int line;
  FuncState *fs = ls->fs;
-  TString *jlb = NULL;
-  int target = NO_JUMP;
  expdesc v;
  int jf;  /* instruction to skip 'then' code (if condition is false) */
  luaX_next(ls);  /* skip IF or ELSEIF */
  expr(ls, &v);  /* read condition */
  checknext(ls, TK_THEN);
-  line = ls->linenumber;
-  if (issinglejump(ls, &jlb, &target)) {  /* 'if x then goto' ? */
-    luaK_goiffalse(ls->fs, &v);  /* will jump to label if condition is true */
+  if (ls->t.token == TK_BREAK) {  /* 'if x then break' ? */
+    int line = ls->linenumber;
+    luaK_goiffalse(ls->fs, &v);  /* will jump if condition is true */
+    luaX_next(ls);  /* skip 'break' */
    enterblock(fs, &bl, 0);  /* must enter block before 'goto' */
-    if (jlb != NULL)  /* forward jump? */
-      newgotoentry(ls, jlb, line, v.t);  /* will be resolved later */
-    else  /* backward jump */
-      luaK_patchlist(fs, v.t, target);  /* jump directly to 'target' */
+    newgotoentry(ls, luaS_newliteral(ls->L, "break"), line, v.t);
    while (testnext(ls, ';')) {}  /* skip semicolons */
    if (block_follow(ls, 0)) {  /* jump is the entire block? */
      leaveblock(fs);
@ -1686,7 +1646,7 @@ static void test_then_block (LexState *ls, int *escapelist) {
    else  /* must skip over 'then' part if condition is false */
      jf = luaK_jump(fs);
  }
-  else {  /* regular case (not a jump) */
+  else {  /* regular case (not a break) */
    luaK_goiftrue(ls->fs, &v);  /* skip over block if condition is false */
    enterblock(fs, &bl, 0);
    jf = v.f;
@ -1754,7 +1714,7 @@ static void checktoclose (LexState *ls, int level) {


 static void localstat (LexState *ls) {
-  /* stat -> LOCAL ATTRIB NAME {',' ATTRIB NAME} ['=' explist] */
+  /* stat -> LOCAL NAME ATTRIB { ',' NAME ATTRIB } ['=' explist] */
  FuncState *fs = ls->fs;
  int toclose = -1;  /* index of to-be-closed variable (if any) */
  Vardesc *var;  /* last variable */
--- a/lua-5.4.2/src/lparser.h
+++ b/lua-5.4.2/src/lparser.h
@ -23,7 +23,7 @@

 /* kinds of variables/expressions */
 typedef enum {
-  VVOID,  /* when 'expdesc' describes the last expression a list,
+  VVOID,  /* when 'expdesc' describes the last expression of a list,
             this kind means an empty list (so, no expression) */
  VNIL,  /* constant nil */
  VTRUE,  /* constant true */
@ -38,7 +38,8 @@ typedef enum {
  VLOCAL,  /* local variable; var.sidx = stack index (local register);
              var.vidx = relative index in 'actvar.arr'  */
  VUPVAL,  /* upvalue variable; info = index of upvalue in 'upvalues' */
-  VCONST,  /* compile-time constant; info = absolute index in 'actvar.arr'  */
+  VCONST,  /* compile-time <const> variable;
+              info = absolute index in 'actvar.arr'  */
  VINDEXED,  /* indexed variable;
                ind.t = table register;
                ind.idx = key's R index */
--- a/lua-5.4.2/src/lprefix.h
+++ b/lua-5.4.2/src/lprefix.h
--- a/lua-5.4.2/src/lstate.c
+++ b/lua-5.4.2/src/lstate.c
@ -76,7 +76,7 @@ static unsigned int luai_makeseed (lua_State *L) {
  addbuff(buff, p, &h);  /* local variable */
  addbuff(buff, p, &lua_newstate);  /* public function */
  lua_assert(p == sizeof(buff));
-  return luaS_hash(buff, p, h, 1);
+  return luaS_hash(buff, p, h);
 }

 #endif
@ -97,66 +97,14 @@ void luaE_setdebt (global_State *g, l_mem debt) {


 LUA_API int lua_setcstacklimit (lua_State *L, unsigned int limit) {
-  global_State *g = G(L);
-  int ccalls;
-  luaE_freeCI(L);  /* release unused CIs */
-  ccalls = getCcalls(L);
-  if (limit >= 40000)
-    return 0;  /* out of bounds */
-  limit += CSTACKERR;
-  if (L != g-> mainthread)
-    return 0;  /* only main thread can change the C stack */
-  else if (ccalls <= CSTACKERR)
-    return 0;  /* handling overflow */
-  else {
-    int diff = limit - g->Cstacklimit;
-    if (ccalls + diff <= CSTACKERR)
-      return 0;  /* new limit would cause an overflow */
-    g->Cstacklimit = limit;  /* set new limit */
-    L->nCcalls += diff;  /* correct 'nCcalls' */
-    return limit - diff - CSTACKERR;  /* success; return previous limit */
-  }
-}
-
-
-/*
-** Decrement count of "C calls" and check for overflows. In case of
-** a stack overflow, check appropriate error ("regular" overflow or
-** overflow while handling stack overflow).  If 'nCcalls' is smaller
-** than CSTACKERR but larger than CSTACKMARK, it means it has just
-** entered the "overflow zone", so the function raises an overflow
-** error.  If 'nCcalls' is smaller than CSTACKMARK (which means it is
-** already handling an overflow) but larger than CSTACKERRMARK, does
-** not report an error (to allow message handling to work). Otherwise,
-** report a stack overflow while handling a stack overflow (probably
-** caused by a repeating error in the message handling function).
-*/
-
-void luaE_enterCcall (lua_State *L) {
-  int ncalls = getCcalls(L);
-  L->nCcalls--;
-  if (ncalls <= CSTACKERR) {  /* possible overflow? */
-    luaE_freeCI(L);  /* release unused CIs */
-    ncalls = getCcalls(L);  /* update call count */
-    if (ncalls <= CSTACKERR) {  /* still overflow? */
-      if (ncalls <= CSTACKERRMARK)  /* below error-handling zone? */
-        luaD_throw(L, LUA_ERRERR);  /* error while handling stack error */
-      else if (ncalls >= CSTACKMARK) {
-        /* not in error-handling zone; raise the error now */
-        L->nCcalls = (CSTACKMARK - 1);  /* enter error-handling zone */
-        luaG_runerror(L, "C stack overflow");
-      }
-      /* else stack is in the error-handling zone;
-         allow message handler to work */
-    }
-  }
+  UNUSED(L); UNUSED(limit);
+  return LUAI_MAXCCALLS;  /* warning?? */
 }


 CallInfo *luaE_extendCI (lua_State *L) {
  CallInfo *ci;
  lua_assert(L->ci->next == NULL);
-  luaE_enterCcall(L);
  ci = luaM_new(L, CallInfo);
  lua_assert(L->ci->next == NULL);
  L->ci->next = ci;
@ -175,13 +123,11 @@ void luaE_freeCI (lua_State *L) {
  CallInfo *ci = L->ci;
  CallInfo *next = ci->next;
  ci->next = NULL;
-  L->nCcalls += L->nci;  /* add removed elements back to 'nCcalls' */
  while ((ci = next) != NULL) {
    next = ci->next;
    luaM_free(L, ci);
    L->nci--;
  }
-  L->nCcalls -= L->nci;  /* adjust result */
 }


@ -194,7 +140,6 @@ void luaE_shrinkCI (lua_State *L) {
  CallInfo *next;
  if (ci == NULL)
    return;  /* no extra elements */
-  L->nCcalls += L->nci;  /* add removed elements back to 'nCcalls' */
  while ((next = ci->next) != NULL) {  /* two extra elements? */
    CallInfo *next2 = next->next;  /* next's next */
    ci->next = next2;  /* remove next from the list */
@ -207,19 +152,39 @@ void luaE_shrinkCI (lua_State *L) {
      ci = next2;  /* continue */
    }
  }
-  L->nCcalls -= L->nci;  /* adjust result */
+}
+
+
+/*
+** Called when 'getCcalls(L)' larger or equal to LUAI_MAXCCALLS.
+** If equal, raises an overflow error. If value is larger than
+** LUAI_MAXCCALLS (which means it is handling an overflow) but
+** not much larger, does not report an error (to allow overflow
+** handling to work).
+*/
+void luaE_checkcstack (lua_State *L) {
+  if (getCcalls(L) == LUAI_MAXCCALLS)
+    luaG_runerror(L, "C stack overflow");
+  else if (getCcalls(L) >= (LUAI_MAXCCALLS / 10 * 11))
+    luaD_throw(L, LUA_ERRERR);  /* error while handing stack error */
+}
+
+
+LUAI_FUNC void luaE_incCstack (lua_State *L) {
+  L->nCcalls++;
+  if (unlikely(getCcalls(L) >= LUAI_MAXCCALLS))
+    luaE_checkcstack(L);
 }


 static void stack_init (lua_State *L1, lua_State *L) {
  int i; CallInfo *ci;
  /* initialize stack array */
-  L1->stack = luaM_newvector(L, BASIC_STACK_SIZE, StackValue);
-  L1->stacksize = BASIC_STACK_SIZE;
-  for (i = 0; i < BASIC_STACK_SIZE; i++)
+  L1->stack = luaM_newvector(L, BASIC_STACK_SIZE + EXTRA_STACK, StackValue);
+  for (i = 0; i < BASIC_STACK_SIZE + EXTRA_STACK; i++)
    setnilvalue(s2v(L1->stack + i));  /* erase new stack */
  L1->top = L1->stack;
-  L1->stack_last = L1->stack + L1->stacksize - EXTRA_STACK;
+  L1->stack_last = L1->stack + BASIC_STACK_SIZE;
  /* initialize first ci */
  ci = &L1->base_ci;
  ci->next = ci->previous = NULL;
@ -240,7 +205,7 @@ static void freestack (lua_State *L) {
  L->ci = &L->base_ci;  /* free the entire 'ci' list */
  luaE_freeCI(L);
  lua_assert(L->nci == 0);
-  luaM_freearray(L, L->stack, L->stacksize);  /* free stack array */
+  luaM_freearray(L, L->stack, stacksize(L) + EXTRA_STACK);  /* free stack */
 }


@ -290,7 +255,6 @@ static void preinit_thread (lua_State *L, global_State *g) {
  L->stack = NULL;
  L->ci = NULL;
  L->nci = 0;
-  L->stacksize = 0;
  L->twups = L;  /* thread has no upvalues */
  L->errorJmp = NULL;
  L->hook = NULL;
@ -301,6 +265,7 @@ static void preinit_thread (lua_State *L, global_State *g) {
  L->openupval = NULL;
  L->status = LUA_OK;
  L->errfunc = 0;
+  L->oldpc = 0;
 }


@ -318,9 +283,10 @@ static void close_state (lua_State *L) {


 LUA_API lua_State *lua_newthread (lua_State *L) {
-  global_State *g = G(L);
+  global_State *g;
  lua_State *L1;
  lua_lock(L);
+  g = G(L);
  luaC_checkGC(L);
  /* create new thread */
  L1 = &cast(LX *, luaM_newobject(L, LUA_TTHREAD, sizeof(LX)))->l;
@ -333,7 +299,7 @@ LUA_API lua_State *lua_newthread (lua_State *L) {
  setthvalue2s(L, L->top, L1);
  api_incr_top(L);
  preinit_thread(L1, g);
-  L1->nCcalls = getCcalls(L);
+  L1->nCcalls = 0;
  L1->hookmask = L->hookmask;
  L1->basehookcount = L->basehookcount;
  L1->hook = L->hook;
@ -394,7 +360,8 @@ LUA_API lua_State *lua_newstate (lua_Alloc f, void *ud) {
  preinit_thread(L, g);
  g->allgc = obj2gco(L);  /* by now, only object is the main thread */
  L->next = NULL;
-  g->Cstacklimit = L->nCcalls = LUAI_MAXCSTACK + CSTACKERR;
+  L->nCcalls = 0;
+  incnny(L);  /* main thread is always non yieldable */
  g->frealloc = f;
  g->ud = ud;
  g->warnf = NULL;
@ -410,8 +377,8 @@ LUA_API lua_State *lua_newstate (lua_Alloc f, void *ud) {
  g->gckind = KGC_INC;
  g->gcemergency = 0;
  g->finobj = g->tobefnz = g->fixedgc = NULL;
-  g->survival = g->old = g->reallyold = NULL;
-  g->finobjsur = g->finobjold = g->finobjrold = NULL;
+  g->firstold1 = g->survival = g->old1 = g->reallyold = NULL;
+  g->finobjsur = g->finobjold1 = g->finobjrold = NULL;
  g->sweepgc = NULL;
  g->gray = g->grayagain = NULL;
  g->weak = g->ephemeron = g->allweak = NULL;
@ -436,8 +403,8 @@ LUA_API lua_State *lua_newstate (lua_Alloc f, void *ud) {


 LUA_API void lua_close (lua_State *L) {
-  L = G(L)->mainthread;  /* only the main thread can be closed */
  lua_lock(L);
+  L = G(L)->mainthread;  /* only the main thread can be closed */
  close_state(L);
 }

--- a/lua-5.4.2/src/lstate.h
+++ b/lua-5.4.2/src/lstate.h
@ -32,13 +32,29 @@
 **
 ** 'allgc' -> 'survival': new objects;
 ** 'survival' -> 'old': objects that survived one collection;
-** 'old' -> 'reallyold': objects that became old in last collection;
+** 'old1' -> 'reallyold': objects that became old in last collection;
 ** 'reallyold' -> NULL: objects old for more than one cycle.
 **
 ** 'finobj' -> 'finobjsur': new objects marked for finalization;
-** 'finobjsur' -> 'finobjold': survived   """";
-** 'finobjold' -> 'finobjrold': just old  """";
+** 'finobjsur' -> 'finobjold1': survived   """";
+** 'finobjold1' -> 'finobjrold': just old  """";
 ** 'finobjrold' -> NULL: really old       """".
+**
+** All lists can contain elements older than their main ages, due
+** to 'luaC_checkfinalizer' and 'udata2finalize', which move
+** objects between the normal lists and the "marked for finalization"
+** lists. Moreover, barriers can age young objects in young lists as
+** OLD0, which then become OLD1. However, a list never contains
+** elements younger than their main ages.
+**
+** The generational collector also uses a pointer 'firstold1', which
+** points to the first OLD1 object in the list. It is used to optimize
+** 'markold'. (Potentially OLD1 objects can be anywhere between 'allgc'
+** and 'reallyold', but often the list has no OLD1 objects or they are
+** after 'old1'.) Note the difference between it and 'old1':
+** 'firstold1': no OLD1 objects before this point; there can be all
+**   ages after it.
+** 'old1': no objects younger than OLD1 after this point.
 */

 /*
@ -47,7 +63,7 @@
 ** can become gray have such a field. The field is not the same
 ** in all objects, but it always has this name.)  Any gray object
 ** must belong to one of these lists, and all objects in these lists
-** must be gray:
+** must be gray (with two exceptions explained below):
 **
 ** 'gray': regular gray objects, still waiting to be visited.
 ** 'grayagain': objects that must be revisited at the atomic phase.
@ -58,54 +74,26 @@
 ** 'weak': tables with weak values to be cleared;
 ** 'ephemeron': ephemeron tables with white->white entries;
 ** 'allweak': tables with weak keys and/or weak values to be cleared.
+**
+** The exceptions to that "gray rule" are:
+** - TOUCHED2 objects in generational mode stay in a gray list (because
+** they must be visited again at the end of the cycle), but they are
+** marked black because assignments to them must activate barriers (to
+** move them back to TOUCHED1).
+** - Open upvales are kept gray to avoid barriers, but they stay out
+** of gray lists. (They don't even have a 'gclist' field.)
 */



 /*
-** About 'nCcalls': each thread in Lua (a lua_State) keeps a count of
-** how many "C calls" it still can do in the C stack, to avoid C-stack
-** overflow.  This count is very rough approximation; it considers only
-** recursive functions inside the interpreter, as non-recursive calls
-** can be considered using a fixed (although unknown) amount of stack
-** space.
-**
-** The count has two parts: the lower part is the count itself; the
-** higher part counts the number of non-yieldable calls in the stack.
-** (They are together so that we can change both with one instruction.)
-**
-** Because calls to external C functions can use an unknown amount
-** of space (e.g., functions using an auxiliary buffer), calls
-** to these functions add more than one to the count (see CSTACKCF).
-**
-** The proper count excludes the number of CallInfo structures allocated
-** by Lua, as a kind of "potential" calls. So, when Lua calls a function
-** (and "consumes" one CallInfo), it needs neither to decrement nor to
-** check 'nCcalls', as its use of C stack is already accounted for.
+** About 'nCcalls':  This count has two parts: the lower 16 bits counts
+** the number of recursive invocations in the C stack; the higher
+** 16 bits counts the number of non-yieldable calls in the stack.
+** (They are together so that we can change and save both with one
+** instruction.)
 */

-/* number of "C stack slots" used by an external C function */
-#define CSTACKCF	10
-
-
-/*
-** The C-stack size is sliced in the following zones:
-** - larger than CSTACKERR: normal stack;
-** - [CSTACKMARK, CSTACKERR]: buffer zone to signal a stack overflow;
-** - [CSTACKCF, CSTACKERRMARK]: error-handling zone;
-** - below CSTACKERRMARK: buffer zone to signal overflow during overflow;
-** (Because the counter can be decremented CSTACKCF at once, we need
-** the so called "buffer zones", with at least that size, to properly
-** detect a change from one zone to the next.)
-*/
-#define CSTACKERR	(8 * CSTACKCF)
-#define CSTACKMARK	(CSTACKERR - (CSTACKCF + 2))
-#define CSTACKERRMARK	(CSTACKCF + 2)
-
-
-/* initial limit for the C-stack of threads */
-#define CSTACKTHREAD	(2 * CSTACKERR)
-

 /* true if this thread does not have non-yieldable calls in the stack */
 #define yieldable(L)		(((L)->nCcalls & 0xffff0000) == 0)
@ -120,13 +108,8 @@
 /* Decrement the number of non-yieldable calls */
 #define decnny(L)	((L)->nCcalls -= 0x10000)

-/* Increment the number of non-yieldable calls and decrement nCcalls */
-#define incXCcalls(L)	((L)->nCcalls += 0x10000 - CSTACKCF)
-
-/* Decrement the number of non-yieldable calls and increment nCcalls */
-#define decXCcalls(L)	((L)->nCcalls -= 0x10000 - CSTACKCF)
-
-
+/* Non-yieldable call increment */
+#define nyci	(0x10000 | 1)



@ -144,12 +127,20 @@ struct lua_longjmp;  /* defined in ldo.c */
 #endif


-/* extra stack space to handle TM calls and some other extras */
+/*
+** Extra stack space to handle TM calls and some other extras. This
+** space is not included in 'stack_last'. It is used only to avoid stack
+** checks, either because the element will be promptly popped or because
+** there will be a stack check soon after the push. Function frames
+** never use this extra space, so it does not need to be kept clean.
+*/
 #define EXTRA_STACK   5


 #define BASIC_STACK_SIZE        (2*LUA_MINSTACK)

+#define stacksize(th)	cast_int((th)->stack_last - (th)->stack)
+

 /* kinds of Garbage Collection */
 #define KGC_INC		0	/* incremental gc */
@ -200,14 +191,15 @@ typedef struct CallInfo {
 */
 #define CIST_OAH	(1<<0)	/* original value of 'allowhook' */
 #define CIST_C		(1<<1)	/* call is running a C function */
-#define CIST_HOOKED	(1<<2)	/* call is running a debug hook */
-#define CIST_YPCALL	(1<<3)	/* call is a yieldable protected call */
-#define CIST_TAIL	(1<<4)	/* call was tail called */
-#define CIST_HOOKYIELD	(1<<5)	/* last hook called yielded */
-#define CIST_FIN	(1<<6)  /* call is running a finalizer */
-#define CIST_TRAN	(1<<7)	/* 'ci' has transfer information */
+#define CIST_FRESH	(1<<2)  /* call is on a fresh "luaV_execute" frame */
+#define CIST_HOOKED	(1<<3)	/* call is running a debug hook */
+#define CIST_YPCALL	(1<<4)	/* call is a yieldable protected call */
+#define CIST_TAIL	(1<<5)	/* call was tail called */
+#define CIST_HOOKYIELD	(1<<6)	/* last hook called yielded */
+#define CIST_FIN	(1<<7)  /* call is running a finalizer */
+#define CIST_TRAN	(1<<8)	/* 'ci' has transfer information */
 #if defined(LUA_COMPAT_LT_LE)
-#define CIST_LEQ	(1<<8)  /* using __lt for __le */
+#define CIST_LEQ	(1<<9)  /* using __lt for __le */
 #endif

 /* active function is a Lua function */
@ -257,10 +249,11 @@ typedef struct global_State {
  GCObject *fixedgc;  /* list of objects not to be collected */
  /* fields for generational collector */
  GCObject *survival;  /* start of objects that survived one GC cycle */
-  GCObject *old;  /* start of old objects */
-  GCObject *reallyold;  /* old objects with more than one cycle */
+  GCObject *old1;  /* start of old1 objects */
+  GCObject *reallyold;  /* objects more than one cycle old ("really old") */
+  GCObject *firstold1;  /* first OLD1 object in the list (if any) */
  GCObject *finobjsur;  /* list of survival objects with finalizers */
-  GCObject *finobjold;  /* list of old objects with finalizers */
+  GCObject *finobjold1;  /* list of old1 objects with finalizers */
  GCObject *finobjrold;  /* list of really old objects with finalizers */
  struct lua_State *twups;  /* list of threads with open upvalues */
  lua_CFunction panic;  /* to be called in unprotected errors */
@ -271,7 +264,6 @@ typedef struct global_State {
  TString *strcache[STRCACHE_N][STRCACHE_M];  /* cache for strings in API */
  lua_WarnFunction warnf;  /* warning function */
  void *ud_warn;         /* auxiliary data to 'warnf' */
-  unsigned int Cstacklimit;  /* current limit for the C stack */
 } global_State;


@ -286,8 +278,7 @@ struct lua_State {
  StkId top;  /* first free slot in the stack */
  global_State *l_G;
  CallInfo *ci;  /* call info for current function */
-  const Instruction *oldpc;  /* last pc traced */
-  StkId stack_last;  /* last free slot in the stack */
+  StkId stack_last;  /* end of stack (last element + 1) */
  StkId stack;  /* stack base */
  UpVal *openupval;  /* list of open upvalues in this stack */
  GCObject *gclist;
@ -296,8 +287,8 @@ struct lua_State {
  CallInfo base_ci;  /* CallInfo for first level (C calling Lua) */
  volatile lua_Hook hook;
  ptrdiff_t errfunc;  /* current error handling function (stack index) */
-  l_uint32 nCcalls;  /* number of allowed nested C calls - 'nci' */
-  int stacksize;
+  l_uint32 nCcalls;  /* number of nested (non-yieldable | C)  calls */
+  int oldpc;  /* last pc traced */
  int basehookcount;
  int hookcount;
  volatile l_signalT hookmask;
@ -309,6 +300,12 @@ struct lua_State {

 /*
 ** Union of all collectable objects (only for conversions)
+** ISO C99, 6.5.2.3 p.5:
+** "if a union contains several structures that share a common initial
+** sequence [...], and if the union object currently contains one
+** of these structures, it is permitted to inspect the common initial
+** part of any of them anywhere that a declaration of the complete type
+** of the union is visible."
 */
 union GCUnion {
  GCObject gc;  /* common header */
@ -322,6 +319,11 @@ union GCUnion {
 };


+/*
+** ISO C99, 6.7.2.1 p.14:
+** "A pointer to a union object, suitably converted, points to each of
+** its members [...], and vice versa."
+*/
 #define cast_u(o)	cast(union GCUnion *, (o))

 /* macros to convert a GCObject into a specific value */
@ -353,12 +355,11 @@ LUAI_FUNC void luaE_freethread (lua_State *L, lua_State *L1);
 LUAI_FUNC CallInfo *luaE_extendCI (lua_State *L);
 LUAI_FUNC void luaE_freeCI (lua_State *L);
 LUAI_FUNC void luaE_shrinkCI (lua_State *L);
-LUAI_FUNC void luaE_enterCcall (lua_State *L);
+LUAI_FUNC void luaE_checkcstack (lua_State *L);
+LUAI_FUNC void luaE_incCstack (lua_State *L);
 LUAI_FUNC void luaE_warning (lua_State *L, const char *msg, int tocont);
 LUAI_FUNC void luaE_warnerror (lua_State *L, const char *where);


-#define luaE_exitCcall(L)	((L)->nCcalls++)
-
 #endif

--- a/lua-5.4.2/src/lstring.c
+++ b/lua-5.4.2/src/lstring.c
@ -22,16 +22,6 @@
 #include "lstring.h"


-/*
-** Lua will use at most ~(2^LUAI_HASHLIMIT) bytes from a long string to
-** compute its hash
-*/
-#if !defined(LUAI_HASHLIMIT)
-#define LUAI_HASHLIMIT		5
-#endif
-
-
-
 /*
 ** Maximum size for string table.
 */
@ -50,10 +40,9 @@ int luaS_eqlngstr (TString *a, TString *b) {
 }


-unsigned int luaS_hash (const char *str, size_t l, unsigned int seed,
-                        size_t step) {
+unsigned int luaS_hash (const char *str, size_t l, unsigned int seed) {
  unsigned int h = seed ^ cast_uint(l);
-  for (; l >= step; l -= step)
+  for (; l > 0; l--)
    h ^= ((h<<5) + (h>>2) + cast_byte(str[l - 1]));
  return h;
 }
@ -63,8 +52,7 @@ unsigned int luaS_hashlongstr (TString *ts) {
  lua_assert(ts->tt == LUA_VLNGSTR);
  if (ts->extra == 0) {  /* no hash? */
    size_t len = ts->u.lnglen;
-    size_t step = (len >> LUAI_HASHLIMIT) + 1;
-    ts->hash = luaS_hash(getstr(ts), len, ts->hash, step);
+    ts->hash = luaS_hash(getstr(ts), len, ts->hash);
    ts->extra = 1;  /* now it has its hash */
  }
  return ts->hash;
@ -201,7 +189,7 @@ static TString *internshrstr (lua_State *L, const char *str, size_t l) {
  TString *ts;
  global_State *g = G(L);
  stringtable *tb = &g->strt;
-  unsigned int h = luaS_hash(str, l, g->seed, 1);
+  unsigned int h = luaS_hash(str, l, g->seed);
  TString **list = &tb->hash[lmod(h, tb->size)];
  lua_assert(str != NULL);  /* otherwise 'memcmp'/'memcpy' are undefined */
  for (ts = *list; ts != NULL; ts = ts->u.hnext) {
--- a/lua-5.4.2/src/lstring.h
+++ b/lua-5.4.2/src/lstring.h
@ -41,8 +41,7 @@
 #define eqshrstr(a,b)	check_exp((a)->tt == LUA_VSHRSTR, (a) == (b))


-LUAI_FUNC unsigned int luaS_hash (const char *str, size_t l,
-                                  unsigned int seed, size_t step);
+LUAI_FUNC unsigned int luaS_hash (const char *str, size_t l, unsigned int seed);
 LUAI_FUNC unsigned int luaS_hashlongstr (TString *ts);
 LUAI_FUNC int luaS_eqlngstr (TString *a, TString *b);
 LUAI_FUNC void luaS_resize (lua_State *L, int newsize);
--- a/lua-5.4.2/src/lstrlib.c
+++ b/lua-5.4.2/src/lstrlib.c
@ -1365,7 +1365,6 @@ typedef union Ftypes {
  float f;
  double d;
  lua_Number n;
-  char buff[5 * sizeof(lua_Number)];  /* enough for any float type */
 } Ftypes;


@ -1535,12 +1534,10 @@ static void packint (luaL_Buffer *b, lua_Unsigned n,
 ** Copy 'size' bytes from 'src' to 'dest', correcting endianness if
 ** given 'islittle' is different from native endianness.
 */
-static void copywithendian (volatile char *dest, volatile const char *src,
+static void copywithendian (char *dest, const char *src,
                            int size, int islittle) {
-  if (islittle == nativeendian.little) {
-    while (size-- != 0)
-      *(dest++) = *(src++);
-  }
+  if (islittle == nativeendian.little)
+    memcpy(dest, src, size);
  else {
    dest += size - 1;
    while (size-- != 0)
@ -1584,14 +1581,14 @@ static int str_pack (lua_State *L) {
        break;
      }
      case Kfloat: {  /* floating-point options */
-        volatile Ftypes u;
+        Ftypes u;
        char *buff = luaL_prepbuffsize(&b, size);
        lua_Number n = luaL_checknumber(L, arg);  /* get argument */
        if (size == sizeof(u.f)) u.f = (float)n;  /* copy it into 'u' */
        else if (size == sizeof(u.d)) u.d = (double)n;
        else u.n = n;
        /* move 'u' to final result, correcting endianness if needed */
-        copywithendian(buff, u.buff, size, h.islittle);
+        copywithendian(buff, (char *)&u, size, h.islittle);
        luaL_addsize(&b, size);
        break;
      }
@ -1717,9 +1714,9 @@ static int str_unpack (lua_State *L) {
        break;
      }
      case Kfloat: {
-        volatile Ftypes u;
+        Ftypes u;
        lua_Number num;
-        copywithendian(u.buff, data + pos, size, h.islittle);
+        copywithendian((char *)&u, data + pos, size, h.islittle);
        if (size == sizeof(u.f)) num = (lua_Number)u.f;
        else if (size == sizeof(u.d)) num = (lua_Number)u.d;
        else num = u.n;
@ -1738,7 +1735,7 @@ static int str_unpack (lua_State *L) {
        break;
      }
      case Kzstr: {
-        size_t len = (int)strlen(data + pos);
+        size_t len = strlen(data + pos);
        luaL_argcheck(L, pos + len < ld, 2,
                         "unfinished string for format 'z'");
        lua_pushlstring(L, data + pos, len);
--- a/lua-5.4.2/src/ltable.c
+++ b/lua-5.4.2/src/ltable.c
@ -166,17 +166,30 @@ static Node *mainpositionTV (const Table *t, const TValue *key) {


 /*
-** Check whether key 'k1' is equal to the key in node 'n2'.
-** This equality is raw, so there are no metamethods. Floats
-** with integer values have been normalized, so integers cannot
-** be equal to floats. It is assumed that 'eqshrstr' is simply
-** pointer equality, so that short strings are handled in the
-** default case.
+** Check whether key 'k1' is equal to the key in node 'n2'. This
+** equality is raw, so there are no metamethods. Floats with integer
+** values have been normalized, so integers cannot be equal to
+** floats. It is assumed that 'eqshrstr' is simply pointer equality, so
+** that short strings are handled in the default case.
+** A true 'deadok' means to accept dead keys as equal to their original
+** values. All dead keys are compared in the default case, by pointer
+** identity. (Only collectable objects can produce dead keys.) Note that
+** dead long strings are also compared by identity.
+** Once a key is dead, its corresponding value may be collected, and
+** then another value can be created with the same address. If this
+** other value is given to 'next', 'equalkey' will signal a false
+** positive. In a regular traversal, this situation should never happen,
+** as all keys given to 'next' came from the table itself, and therefore
+** could not have been collected. Outside a regular traversal, we
+** have garbage in, garbage out. What is relevant is that this false
+** positive does not break anything.  (In particular, 'next' will return
+** some other valid item on the table or nil.)
 */
-static int equalkey (const TValue *k1, const Node *n2) {
-  if (rawtt(k1) != keytt(n2))  /* not the same variants? */
+static int equalkey (const TValue *k1, const Node *n2, int deadok) {
+  if ((rawtt(k1) != keytt(n2)) &&  /* not the same variants? */
+       !(deadok && keyisdead(n2) && iscollectable(k1)))
   return 0;  /* cannot be same key */
-  switch (ttypetag(k1)) {
+  switch (keytt(n2)) {
    case LUA_VNIL: case LUA_VFALSE: case LUA_VTRUE:
      return 1;
    case LUA_VNUMINT:
@ -187,7 +200,7 @@ static int equalkey (const TValue *k1, const Node *n2) {
      return pvalue(k1) == pvalueraw(keyval(n2));
    case LUA_VLCF:
      return fvalue(k1) == fvalueraw(keyval(n2));
-    case LUA_VLNGSTR:
+    case ctb(LUA_VLNGSTR):
      return luaS_eqlngstr(tsvalue(k1), keystrval(n2));
    default:
      return gcvalue(k1) == gcvalueraw(keyval(n2));
@ -251,11 +264,12 @@ static unsigned int setlimittosize (Table *t) {
 /*
 ** "Generic" get version. (Not that generic: not valid for integers,
 ** which may be in array part, nor for floats with integral values.)
+** See explanation about 'deadok' in function 'equalkey'.
 */
-static const TValue *getgeneric (Table *t, const TValue *key) {
+static const TValue *getgeneric (Table *t, const TValue *key, int deadok) {
  Node *n = mainpositionTV(t, key);
  for (;;) {  /* check whether 'key' is somewhere in the chain */
-    if (equalkey(key, n))
+    if (equalkey(key, n, deadok))
      return gval(n);  /* that's it */
    else {
      int nx = gnext(n);
@ -292,7 +306,7 @@ static unsigned int findindex (lua_State *L, Table *t, TValue *key,
  if (i - 1u < asize)  /* is 'key' inside array part? */
    return i;  /* yes; that's the index */
  else {
-    const TValue *n = getgeneric(t, key);
+    const TValue *n = getgeneric(t, key, 1);
    if (unlikely(isabstkey(n)))
      luaG_runerror(L, "invalid key to 'next'");  /* key not found */
    i = cast_int(nodefromval(n) - gnode(t, 0));  /* key index in hash table */
@ -583,7 +597,7 @@ Table *luaH_new (lua_State *L) {
  GCObject *o = luaC_newobj(L, LUA_VTABLE, sizeof(Table));
  Table *t = gco2t(o);
  t->metatable = NULL;
-  t->flags = cast_byte(~0);
+  t->flags = cast_byte(maskflags);  /* table has no metamethod fields */
  t->array = NULL;
  t->alimit = 0;
  setnodevector(L, t, 0);
@ -730,7 +744,7 @@ const TValue *luaH_getstr (Table *t, TString *key) {
  else {  /* for long strings, use generic case */
    TValue ko;
    setsvalue(cast(lua_State *, NULL), &ko, key);
-    return getgeneric(t, &ko);
+    return getgeneric(t, &ko, 0);
  }
 }

@ -750,7 +764,7 @@ const TValue *luaH_get (Table *t, const TValue *key) {
      /* else... */
    }  /* FALLTHROUGH */
    default:
-      return getgeneric(t, key);
+      return getgeneric(t, key, 0);
  }
 }

--- a/lua-5.4.2/src/ltable.h
+++ b/lua-5.4.2/src/ltable.h
@ -15,7 +15,12 @@
 #define gnext(n)	((n)->u.next)


-#define invalidateTMcache(t)	((t)->flags = 0)
+/*
+** Clear all bits of fast-access metamethods, which means that the table
+** may have any of these metamethods. (First access that fails after the
+** clearing will set the bit again.)
+*/
+#define invalidateTMcache(t)	((t)->flags &= ~maskflags)


 /* true when 't' is using 'dummynode' as its hash part */
--- a/lua-5.4.2/src/ltablib.c
+++ b/lua-5.4.2/src/ltablib.c
--- a/lua-5.4.2/src/ltm.c
+++ b/lua-5.4.2/src/ltm.c
@ -240,7 +240,7 @@ void luaT_adjustvarargs (lua_State *L, int nfixparams, CallInfo *ci,
  int actual = cast_int(L->top - ci->func) - 1;  /* number of arguments */
  int nextra = actual - nfixparams;  /* number of extra arguments */
  ci->u.l.nextraargs = nextra;
-  checkstackGC(L, p->maxstacksize + 1);
+  luaD_checkstack(L, p->maxstacksize + 1);
  /* copy function to the top of the stack */
  setobjs2s(L, L->top++, ci->func);
  /* move fixed parameters to the top of the stack */
@ -259,7 +259,7 @@ void luaT_getvarargs (lua_State *L, CallInfo *ci, StkId where, int wanted) {
  int nextra = ci->u.l.nextraargs;
  if (wanted < 0) {
    wanted = nextra;  /* get all extra arguments available */
-    checkstackp(L, nextra, where);  /* ensure stack space */
+    checkstackGCp(L, nextra, where);  /* ensure stack space */
    L->top = where + nextra;  /* next instruction will need top */
  }
  for (i = 0; i < wanted && i < nextra; i++)
--- a/lua-5.4.2/src/ltm.h
+++ b/lua-5.4.2/src/ltm.h
@ -45,6 +45,15 @@ typedef enum {
 } TMS;


+/*
+** Mask with 1 in all fast-access methods. A 1 in any of these bits
+** in the flag of a (meta)table means the metatable does not have the
+** corresponding metamethod field. (Bit 7 of the flag is used for
+** 'isrealasize'.)
+*/
+#define maskflags	(~(~0u << (TM_EQ + 1)))
+
+
 /*
 ** Test whether there is no tagmethod.
 ** (Because tagmethods use raw accesses, the result may be an "empty" nil.)
--- a/lua-5.4.2/src/lua.c
+++ b/lua-5.4.2/src/lua.c
@ -416,15 +416,19 @@ static int handle_luainit (lua_State *L) {


 /*
-** Returns the string to be used as a prompt by the interpreter.
+** Return the string to be used as a prompt by the interpreter. Leave
+** the string (or nil, if using the default value) on the stack, to keep
+** it anchored.
 */
 static const char *get_prompt (lua_State *L, int firstline) {
-  const char *p;
-  lua_getglobal(L, firstline ? "_PROMPT" : "_PROMPT2");
-  p = lua_tostring(L, -1);
-  if (p == NULL) p = (firstline ? LUA_PROMPT : LUA_PROMPT2);
+  if (lua_getglobal(L, firstline ? "_PROMPT" : "_PROMPT2") == LUA_TNIL)
+    return (firstline ? LUA_PROMPT : LUA_PROMPT2);  /* use the default */
+  else {  /* apply 'tostring' over the value */
+    const char *p = luaL_tolstring(L, -1, NULL);
+    lua_remove(L, -2);  /* remove original value */
    return p;
  }
+}

 /* mark in error messages for incomplete statements */
 #define EOFMARK		"<eof>"
--- a/lua-5.4.2/src/lua.hpp
+++ b/lua-5.4.2/src/lua.hpp
--- a/lua-5.4.2/src/luac.c
+++ b/lua-5.4.2/src/luac.c
--- a/lua-5.4.2/src/lundump.c
+++ b/lua-5.4.2/src/lundump.c
@ -120,7 +120,10 @@ static TString *loadStringN (LoadState *S, Proto *p) {
  }
  else {  /* long string */
    ts = luaS_createlngstrobj(L, size);  /* create string */
+    setsvalue2s(L, L->top, ts);  /* anchor it ('loadVector' can GC) */
+    luaD_inctop(L);
    loadVector(S, getstr(ts), size);  /* load directly in final place */
+    L->top--;  /* pop string */
  }
  luaC_objbarrier(L, p, ts);
  return ts;
@ -200,13 +203,20 @@ static void loadProtos (LoadState *S, Proto *f) {
 }


+/*
+** Load the upvalues for a function. The names must be filled first,
+** because the filling of the other fields can raise read errors and
+** the creation of the error message can call an emergency collection;
+** in that case all prototypes must be consistent for the GC.
+*/
 static void loadUpvalues (LoadState *S, Proto *f) {
  int i, n;
  n = loadInt(S);
  f->upvalues = luaM_newvectorchecked(S->L, n, Upvaldesc);
  f->sizeupvalues = n;
-  for (i = 0; i < n; i++) {
+  for (i = 0; i < n; i++)  /* make array valid for GC */
    f->upvalues[i].name = NULL;
+  for (i = 0; i < n; i++) {  /* following calls can raise errors */
    f->upvalues[i].instack = loadByte(S);
    f->upvalues[i].idx = loadByte(S);
    f->upvalues[i].kind = loadByte(S);
--- a/lua-5.4.2/src/lundump.h
+++ b/lua-5.4.2/src/lundump.h
--- a/lua-5.4.2/src/lutf8lib.c
+++ b/lua-5.4.2/src/lutf8lib.c
--- a/lua-5.4.2/src/lvm.c
+++ b/lua-5.4.2/src/lvm.c
@ -229,7 +229,7 @@ static int forprep (lua_State *L, StkId ra) {
        count /= l_castS2U(-(step + 1)) + 1u;
      }
      /* store the counter in place of the limit (which won't be
-         needed anymore */
+         needed anymore) */
      setivalue(plimit, l_castU2S(count));
    }
  }
@ -634,7 +634,8 @@ static void copy2buff (StkId top, int n, char *buff) {
 ** from 'L->top - total' up to 'L->top - 1'.
 */
 void luaV_concat (lua_State *L, int total) {
-  lua_assert(total >= 2);
+  if (total == 1)
+    return;  /* "all" values already concatenated */
  do {
    StkId top = L->top;
    int n = 2;  /* number of elements handled in this pass (at least 2) */
@ -840,10 +841,8 @@ void luaV_finishOp (lua_State *L) {
      int a = GETARG_A(inst);      /* first element to concatenate */
      int total = cast_int(top - 1 - (base + a));  /* yet to concatenate */
      setobjs2s(L, top - 2, top);  /* put TM result in proper position */
-      if (total > 1) {  /* are there elements to concat? */
      L->top = top - 1;  /* top is one after last element (at top-2) */
      luaV_concat(L, total);  /* concat them (may yield again) */
-      }
      break;
    }
    default: {
@ -1093,18 +1092,14 @@ void luaV_finishOp (lua_State *L) {
 #define ProtectNT(exp)  (savepc(L), (exp), updatetrap(ci))

 /*
-** Protect code that will finish the loop (returns) or can only raise
-** errors. (That is, it will not return to the interpreter main loop
-** after changing the stack or hooks.)
+** Protect code that can only raise errors. (That is, it cannnot change
+** the stack or hooks.)
 */
 #define halfProtect(exp)  (savestate(L,ci), (exp))

-/* idem, but without changing the stack */
-#define halfProtectNT(exp)  (savepc(L), (exp))
-
-
+/* 'c' is the limit of live values in the stack */
 #define checkGC(L,c)  \
-	{ luaC_condGC(L, L->top = (c),  /* limit of live values */ \
+	{ luaC_condGC(L, (savepc(L), L->top = (c)), \
                         updatetrap(ci)); \
           luai_threadyield(L); }

@ -1133,17 +1128,20 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
 #if LUA_USE_JUMPTABLE
 #include "ljumptab.h"
 #endif
- tailcall:
+ startfunc:
  trap = L->hookmask;
+ returning:  /* trap already set */
  cl = clLvalue(s2v(ci->func));
  k = cl->p->k;
  pc = ci->u.l.savedpc;
  if (trap) {
+    if (pc == cl->p->code) {  /* first instruction (not resuming)? */
      if (cl->p->is_vararg)
        trap = 0;  /* hooks will start after VARARGPREP instruction */
-    else if (pc == cl->p->code)  /* first instruction (not resuming)? */
+      else  /* check 'call' hook */
        luaD_hookcall(L, ci);
-    ci->u.l.trap = 1;  /* there may be other hooks */
+    }
+    ci->u.l.trap = 1;  /* assume trap is on, for now */
  }
  base = ci->func + 1;
  /* main loop of interpreter */
@ -1152,7 +1150,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
    StkId ra;  /* instruction's A register */
    vmfetch();
    lua_assert(base == ci->func + 1);
-    lua_assert(base <= L->top && L->top < L->stack + L->stacksize);
+    lua_assert(base <= L->top && L->top < L->stack_last);
    /* invalidate top for instructions not expecting it */
    lua_assert(isIT(i) || (cast_void(L->top = base), 1));
    vmdispatch (GET_OPCODE(i)) {
@ -1607,24 +1605,32 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
        vmbreak;
      }
      vmcase(OP_CALL) {
+        CallInfo *newci;
        int b = GETARG_B(i);
        int nresults = GETARG_C(i) - 1;
        if (b != 0)  /* fixed number of arguments? */
          L->top = ra + b;  /* top signals number of arguments */
        /* else previous instruction set top */
-        ProtectNT(luaD_call(L, ra, nresults));
+        savepc(L);  /* in case of errors */
+        if ((newci = luaD_precall(L, ra, nresults)) == NULL)
+          updatetrap(ci);  /* C call; nothing else to be done */
+        else {  /* Lua call: run function in this same C frame */
+          ci = newci;
+          ci->callstatus = 0;  /* call re-uses 'luaV_execute' */
+          goto startfunc;
+        }
        vmbreak;
      }
      vmcase(OP_TAILCALL) {
        int b = GETARG_B(i);  /* number of arguments + 1 (function) */
        int nparams1 = GETARG_C(i);
-        /* delat is virtual 'func' - real 'func' (vararg functions) */
+        /* delta is virtual 'func' - real 'func' (vararg functions) */
        int delta = (nparams1) ? ci->u.l.nextraargs + nparams1 : 0;
        if (b != 0)
          L->top = ra + b;
        else  /* previous instruction set top */
          b = cast_int(L->top - ra);
-        savepc(ci);  /* some calls here can raise errors */
+        savepc(ci);  /* several calls here can raise errors */
        if (TESTARG_k(i)) {
          /* close upvalues from current call; the compiler ensures
             that there are no to-be-closed variables here, so this
@ -1635,19 +1641,20 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
        while (!ttisfunction(s2v(ra))) {  /* not a function? */
          luaD_tryfuncTM(L, ra);  /* try '__call' metamethod */
          b++;  /* there is now one extra argument */
-          checkstackp(L, 1, ra);
+          checkstackGCp(L, 1, ra);
        }
        if (!ttisLclosure(s2v(ra))) {  /* C function? */
-          luaD_call(L, ra, LUA_MULTRET);  /* call it */
+          luaD_precall(L, ra, LUA_MULTRET);  /* call it */
          updatetrap(ci);
          updatestack(ci);  /* stack may have been relocated */
-          ci->func -= delta;
-          luaD_poscall(L, ci, cast_int(L->top - ra));
-          return;
+          ci->func -= delta;  /* restore 'func' (if vararg) */
+          luaD_poscall(L, ci, cast_int(L->top - ra));  /* finish caller */
+          updatetrap(ci);  /* 'luaD_poscall' can change hooks */
+          goto ret;  /* caller returns after the tail call */
        }
-        ci->func -= delta;
+        ci->func -= delta;  /* restore 'func' (if vararg) */
        luaD_pretailcall(L, ci, ra, b);  /* prepare call frame */
-        goto tailcall;
+        goto startfunc;  /* execute the callee */
      }
      vmcase(OP_RETURN) {
        int n = GETARG_B(i) - 1;  /* number of results */
@ -1666,12 +1673,15 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
          ci->func -= ci->u.l.nextraargs + nparams1;
        L->top = ra + n;  /* set call for 'luaD_poscall' */
        luaD_poscall(L, ci, n);
-        return;
+        updatetrap(ci);  /* 'luaD_poscall' can change hooks */
+        goto ret;
      }
      vmcase(OP_RETURN0) {
        if (L->hookmask) {
          L->top = ra;
-          halfProtectNT(luaD_poscall(L, ci, 0));  /* no hurry... */
+          savepc(ci);
+          luaD_poscall(L, ci, 0);  /* no hurry... */
+          trap = 1;
        }
        else {  /* do the 'poscall' here */
          int nres = ci->nresults;
@ -1680,12 +1690,14 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
          while (nres-- > 0)
            setnilvalue(s2v(L->top++));  /* all results are nil */
        }
-        return;
+        goto ret;
      }
      vmcase(OP_RETURN1) {
        if (L->hookmask) {
          L->top = ra + 1;
-          halfProtectNT(luaD_poscall(L, ci, 1));  /* no hurry... */
+          savepc(ci);
+          luaD_poscall(L, ci, 1);  /* no hurry... */
+          trap = 1;
        }
        else {  /* do the 'poscall' here */
          int nres = ci->nresults;
@ -1699,7 +1711,13 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
              setnilvalue(s2v(L->top++));
          }
        }
-        return;
+       ret:  /* return from a Lua function */
+        if (ci->callstatus & CIST_FRESH)
+          return;  /* end this frame */
+        else {
+          ci = ci->previous;
+          goto returning;  /* continue running caller in this frame */
+        }
      }
      vmcase(OP_FORLOOP) {
        if (ttisinteger(s2v(ra + 2))) {  /* integer loop? */
@ -1792,11 +1810,10 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
        vmbreak;
      }
      vmcase(OP_VARARGPREP) {
-        luaT_adjustvarargs(L, GETARG_A(i), ci, cl->p);
-        updatetrap(ci);
+        ProtectNT(luaT_adjustvarargs(L, GETARG_A(i), ci, cl->p));
        if (trap) {
          luaD_hookcall(L, ci);
-          L->oldpc = pc + 1;  /* next opcode will be seen as a "new" line */
+          L->oldpc = 1;  /* next opcode will be seen as a "new" line */
        }
        updatebase(ci);  /* function has new base after adjustment */
        vmbreak;
--- a/lua-5.4.2/src/lvm.h
+++ b/lua-5.4.2/src/lvm.h
--- a/lua-5.4.2/src/lzio.c
+++ b/lua-5.4.2/src/lzio.c
--- a/lua-5.4.2/src/lzio.h
+++ b/lua-5.4.2/src/lzio.h
--- a/orig_sources/lua-5.4.0.tar.gz
+++ b/orig_sources/lua-5.4.0.tar.gz
--- a/orig_sources/lua-5.4.2.tar.gz
+++ b/orig_sources/lua-5.4.2.tar.gz