One might think that by merging the equivalence classes (eqclasses) of
`Sym1` and `Sym2` symbols we would end up with a `State` in which the
eqclass of `Sym1` and `Sym2` should now be the same. Surprisingly, it's
not //always// true.
Such an example triggered the assertion enforcing this _unjustified_
invariant in https://github.com/llvm/llvm-project/issues/58677.
```lang=C++
unsigned a, b;
#define assert(cond) if (!(cond)) return
void f(unsigned c) {
/*(1)*/ assert(c == b);
/*(2)*/ assert((c | a) != a);
/*(3)*/ assert(a);
// a = 0 => c | 0 != 0 => c != 0 => b != 0
}
```
I believe, that this assertion hold for reasonable cases - where both
`MemberSym` and `SimplifiedMemberSym` refer to live symbols.
It can only fail if `SimplifiedMemberSym` refers to an already dead
symbol. See the reasoning at the very end.
In this context, I don't know any way of determining if a symbol is
alive/dead, so I cannot refine the assertion in that way.
So, I'm proposing to drop this unjustified assertion.
---
Let me elaborate on why I think the assertion is wrong in its current
shape.
Here is a quick reminder about equivalence classes in CSA.
We have 4 mappings:
1) `ClassMap`: map, associating `Symbols` with an `EquivalenceClass`.
2) `ClassMembers`: map, associating `EquivalenceClasses` with its
members - basically an enumeration of the `Symbols` which are known
to be equal.
3) `ConstraintRange`: map, associating `EquivalenceClasses` with the
range constraint which should hold for all the members of the
eqclass.
4) `DisequalityMap`: I'm omitting this, as it's irrelevant for our
purposes now.
Whenever we encounter/assume that two `SymbolRefs` are equal, we update
the `ClassMap` so that now both `SymbolRefs` are referring to the same
eqclass. This operation is known as `merge` or `union`.
Each eqclass is uniquely identified by the `representative` symbol, but
it could have been just a unique number or anything else - the point
is that an eqclass is identified by something unique.
Initially, all Symbols form - by itself - a trivial eqclass, as there
are no other Symbols to which it is assumed to be equal. A trivial
eqclass has //notionally// exactly one member, the representative symbol.
I'm emphasizing that //notionally// because for such cases we don't store
an entry in the `ClassMap` nor in the `ClassMembers` map, because it
could be deduced.
By `merging` two eqclasses, we essentially do what you would think it
does. An important thing to highlight is that the representative symbol
of the resulting eqclass will be the same as one of the two eqclasses.
This operation should be commutative, so that `merge(eq1,eq2)` and
`merge(eq2,eq1)` should result in the same eqclass - except for the
representative symbol, which is just a unique identifier of the class,
a name if you will. Using the representative symbol of `eq1` or `eq2`
should have no visible effect on the analysis overall.
When merging `eq1` into `eq2`, we take each of the `ClassMembers` of
`eq1` and add them to the `ClassMembers` of `eq2` while we also redirect
all the `Symbol` members of `eq1` to map to the `eq2` eqclass in the
`ClassMap`. This way all members of `eq1` will refer to the correct
eqclass. After these, `eq1` key is unreachable in the `ClassMembers`,
hence we can drop it.
---
Let's get back to the example.
Note that when I refer to symbols `a`, `b`, `c`, I'm referring to the
`SymbolRegionValue{VarRegion{.}}` - the value of that variable.
After `(1)`, we will have a constraint `c == b : [1,1]` and an eqclass
`c,b` with the `c` representative symbol.
After `(2)`, we will have an additional constraint `c|b != a : [1,1]`
with the same eqclass. We will also have disequality info about that
`c|a` is disequal to `a` - and the other way around.
However, after the full-expression, `c` will become dead. This kicks in
the garbage collection, which transforms the state into this:
- We no longer have any constraints, because only `a` is alive, for
which we don't have any constraints.
- We have a single (non-trivial) eqclass with a single element `b` and
representative symbol `c`. (Dead symbols can be representative
symbols.)
- We have the same disequality info as before.
At `(3)` within the false branch, `a` get perfectly constrained to zero.
This kicks in the simplification, so we try to substitute (simplify) the
variable in each SymExpr-tree. In our case, it means that the
`c|a != a : [1,1]` constraint gets re-evaluated as `c|0 != 0 : [1,1]`,
which is `c != 0 : [1,1]`.
Under the hood, it means that we will call `merge(c|a, c)`. where `c` is
the result of `simplifyToSVal(State, MemberSym).getAsSymbol()` inside
`EquivalenceClass::simplify()`.
Note that the result of `simplifyToSVal()` was a dead symbol. We
shouldn't have acquired an already dead symbol. AFAIK, this is the only
way we can get one at this point.
Since `c` is dead, we no longer have a mapping in `ClassMap` for it;
hence when we try to `find()` the eqclass of `c`, it will report that
it's a trivial eqclass with the representative symbol `c`.
After `merge(c|a, c)`, we will have a single (non-trivial) eqclass of
`b, c|a` with the representative symbol `c|a` - because we merged the
eqclass of `c` into the eqclass of `c|a`.
This means that `find(c|a)` will result in the eqclass with the
representative symbol `c|a`. So, we ended up having different eqclasses
for `find(c|a)` and `find(c)` after `merge(c|a, c)`, firing the
assertion.
I believe, that this assertion hold for reasonable cases - where both
`MemberSym` and `SimplifiedMemberSym` refer to live symbols.
`MemberSym` should be live in all cases here, because it is from
`ClassMembers` which is pruned in `removeDeadBindings()` so these must
be alive. In this context, I don't know any way of determining if a
symbol is alive/dead, so I cannot refine the assertion in that way.
So, I'm proposing to drop this unjustified assertion.
I'd like to thank @martong for helping me to conclude the investigation.
It was really difficult to track down.
PS: I mentioned that `merge(eq1, eq2)` should be commutative. We
actually exploit this for merging the smaller eqclass into the bigger
one within `EquivalenceClass::merge()`.
Yea, for some reason, if you swap the operands, 3 tests break (only
failures, no crashes) aside from the test which checks the state dumps.
But I believe, that is a different bug and orthogonal to this one. I
just wanted to mention that.
- `Analysis/solver-sym-simplification-adjustment.c`
- `Analysis/symbol-simplification-fixpoint-iteration-unreachable-code.cpp`
- `Analysis/symbol-simplification-reassume.cpp`
Fixes#58677
Reviewed By: vabridgers
Differential Revision: https://reviews.llvm.org/D138037
This patch fixes certain cases where solver was not able to infer
disequality due to overlapping of values in rangeset. This case was
casting from lower signed type to bigger unsigned type.
Reviewed By: steakhal
Differential Revision: https://reviews.llvm.org/D140086
This commit relands the patches for implementing P0960R3 and P1975R0,
which describe initializing aggregates via a parenthesized list.
The relanded commits are:
* 40c52159d3ee - P0960R3 and P1975R0: Allow initializing aggregates from
a parenthesized list of values
* c77a91bb7ba7 - Remove overly restrictive aggregate paren init logic
* 32d7aae04fdb - Fix a clang crash on invalid code in C++20 mode
This patch also fixes a crash in the original implementation.
Previously, if the input tried to call an implicitly deleted copy or
move constructor of a union, we would then try to initialize the union
by initializing it's first element with a reference to a union. This
behavior is incorrect (we should fail to initialize) and if the type of
the first element has a constructor with a single template typename
parameter, then Clang will explode. This patch fixes that issue by
checking that constructor overload resolution did not result in a
deleted function before attempting parenthesized aggregate
initialization.
Additionally, this patch also includes D140159, which contains some
minor fixes made in response to code review comments in the original
implementation that were made after that patch was submitted.
Co-authored-by: Sheng <ox59616e@gmail.com>
Fixes#54040, Fixes#59675
Reviewed By: ilya-biryukov
Differential Revision: https://reviews.llvm.org/D141546
When the engine processes a store to a variable, it will eventually call
`ExprEngine::processPointerEscapedOnBind()`. This function is supposed to
invalidate (put the given locations to an escape list) the locations
which we cannot reason about.
Unfortunately, local static variables are also put into this list.
This patch relaxes the guard condition, so that beyond stack variables,
static local variables are also ignored.
Differential Revision: https://reviews.llvm.org/D139534
This feature causes clang to crash when compiling Chrome - see
https://crbug.com/1405031 and
https://github.com/llvm/llvm-project/issues/59675
Revert "[clang] Fix a clang crash on invalid code in C++20 mode."
This reverts commit 32d7aae04fdb58e65a952f281ff2f2c3f396d98f.
Revert "[clang] Remove overly restrictive aggregate paren init logic"
This reverts commit c77a91bb7ba793ec3a6a5da3743ed55056291658.
Revert "[clang][C++20] P0960R3 and P1975R0: Allow initializing aggregates from a parenthesized list of values"
This reverts commit 40c52159d3ee337dbed14e4c73b5616ea354c337.
This avoids recomputing string length that is already known at compile time.
It has a slight impact on preprocessing / compile time, see
https://llvm-compile-time-tracker.com/compare.php?from=3f36d2d579d8b0e8824d9dd99bfa79f456858f88&to=e49640c507ddc6615b5e503144301c8e41f8f434&stat=instructions:u
This a recommit of e953ae5bbc313fd0cc980ce021d487e5b5199ea4 and the subsequent fixes caa713559bd38f337d7d35de35686775e8fb5175 and 06b90e2e9c991e211fecc97948e533320a825470.
The above patchset caused some version of GCC to take eons to compile clang/lib/Basic/Targets/AArch64.cpp, as spotted in aa171833ab0017d9732e82b8682c9848ab25ff9e.
The fix is to make BuiltinInfo tables a compilation unit static variable, instead of a private static variable.
Differential Revision: https://reviews.llvm.org/D139881
Revert "Fix lldb option handling since e953ae5bbc313fd0cc980ce021d487e5b5199ea4 (part 2)"
Revert "Fix lldb option handling since e953ae5bbc313fd0cc980ce021d487e5b5199ea4"
GCC build hangs on this bot https://lab.llvm.org/buildbot/#/builders/37/builds/19104
compiling CMakeFiles/obj.clangBasic.dir/Targets/AArch64.cpp.d
The bot uses GNU 11.3.0, but I can reproduce locally with gcc (Debian 12.2.0-3) 12.2.0.
This reverts commit caa713559bd38f337d7d35de35686775e8fb5175.
This reverts commit 06b90e2e9c991e211fecc97948e533320a825470.
This reverts commit e953ae5bbc313fd0cc980ce021d487e5b5199ea4.
This avoids the continuous API churn when upgrading things to use
std::optional and makes trivial string replace upgrades possible.
I tested this with GCC 7.5, the oldest supported GCC I had around.
Differential Revision: https://reviews.llvm.org/D140332
std::optional::value() has undesired exception checking semantics and is
unavailable in older Xcode (see _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS). The
call sites block std::optional migration.
This makes `ninja clang` work in the absence of llvm::Optional::value.
value() has undesired exception checking semantics and calls
__throw_bad_optional_access in libc++. Moreover, the API is unavailable without
_LIBCPP_NO_EXCEPTIONS on older Mach-O platforms (see
_LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS).
This fixes clang.
This patch implements P0960R3, which allows initialization of aggregates
via parentheses.
As an example:
```
struct S { int i, j; };
S s1(1, 1);
int arr1[2](1, 2);
```
This patch also implements P1975R0, which fixes the wording of P0960R3
for single-argument parenthesized lists so that statements like the
following are allowed:
```
S s2(1);
S s3 = static_cast<S>(1);
S s4 = (S)1;
int (&&arr2)[] = static_cast<int[]>(1);
int (&&arr3)[2] = static_cast<int[2]>(1);
```
This patch was originally authored by @0x59616e and completed by
@ayzhao.
Fixes#54040, Fixes#54041
Co-authored-by: Sheng <ox59616e@gmail.com>
Full write up : https://discourse.llvm.org/t/c-20-rfc-suggestion-desired-regarding-the-implementation-of-p0960r3/63744
Reviewed By: ilya-biryukov
Differential Revision: https://reviews.llvm.org/D129531
With this patch, the solver can infer results for not equal (!=) operator
over Ranges as well. This also fixes the issue of comparison between
different types, by first converting the RangeSets to the resulting type,
which then can be used for comparisons.
Patch by Manas.
Reviewed By: steakhal
Differential Revision: https://reviews.llvm.org/D112621
This patch mechanically replaces None with std::nullopt where the
compiler would warn if None were deprecated. The intent is to reduce
the amount of manual work required in migrating from Optional to
std::optional.
This is part of an effort to migrate from llvm::Optional to
std::optional:
https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716
By default, clang assumes that all trailing array objects could be a
FAM. So, an array of undefined size, size 0, size 1, or even size 42 is
considered as FAMs for optimizations at least.
One needs to override the default behavior by supplying the
`-fstrict-flex-arrays=<N>` flag, with `N > 0` value to reduce the set of
FAM candidates. Value `3` is the most restrictive and `0` is the most
permissive on this scale.
0: all trailing arrays are FAMs
1: only incomplete, zero and one-element arrays are FAMs
2: only incomplete, zero-element arrays are FAMs
3: only incomplete arrays are FAMs
If the user is happy with consdering single-element arrays as FAMs, they
just need to remove the
`consider-single-element-arrays-as-flexible-array-members` from the
command line.
Otherwise, if they don't want to recognize such cases as FAMs, they
should specify `-fstrict-flex-arrays` anyway, which will be picked up by
CSA.
Any use of the deprecated analyzer-config value will trigger a warning
explaining what to use instead.
The `-analyzer-config-help` is updated accordingly.
Depends on D138657
Reviewed By: xazax.hun
Differential Revision: https://reviews.llvm.org/D138659
Casting a pointer to a suitably large integral type by reinterpret-cast
should result in the same value as by using the `__builtin_bit_cast()`.
The compiler exploits this: https://godbolt.org/z/zMP3sG683
However, the analyzer does not bind the same symbolic value to these
expressions, resulting in weird situations, such as failing equality
checks and even results in crashes: https://godbolt.org/z/oeMP7cj8q
Previously, in the `RegionStoreManager::getBinding()` even if `T` was
non-null, we replaced it with `TVR->getValueType()` in case the `MR` was
`TypedValueRegion`.
It doesn't make much sense to auto-detect the type if the type is
already given. By not doing the auto-detection, we would just do the
right thing and perform the load by that type.
This means that we will cast the value to that type.
So, in this patch, I'm proposing to do auto-detection only if the type
was null.
Here is a snippet of code, annotated by the previous and new dump values.
`LocAsInteger` should wrap the `SymRegion`, since we want to load the
address as if it was an integer.
In none of the following cases should type auto-detection be triggered,
hence we should eventually reach an `evalCast()` to lazily cast the loaded
value into that type.
```lang=C++
void LValueToRValueBitCast_dumps(void *p, char (*array)[8]) {
clang_analyzer_dump(p); // remained: &SymRegion{reg_$0<void * p>}
clang_analyzer_dump(array); // remained: {{&SymRegion{reg_$1<char (*)[8] array>}
clang_analyzer_dump((unsigned long)p);
// remained: {{&SymRegion{reg_$0<void * p>} [as 64 bit integer]}}
clang_analyzer_dump(__builtin_bit_cast(unsigned long, p)); <--------- change #1
// previously: {{&SymRegion{reg_$0<void * p>}}}
// now: {{&SymRegion{reg_$0<void * p>} [as 64 bit integer]}}
clang_analyzer_dump((unsigned long)array); // remained: {{&SymRegion{reg_$1<char (*)[8] array>} [as 64 bit integer]}}
clang_analyzer_dump(__builtin_bit_cast(unsigned long, array)); <--------- change #2
// previously: {{&SymRegion{reg_$1<char (*)[8] array>}}}
// now: {{&SymRegion{reg_$1<char (*)[8] array>} [as 64 bit integer]}}
}
```
Reviewed By: xazax.hun
Differential Revision: https://reviews.llvm.org/D136603
Refactor StaticAnalyzer to use clang::SarifDocumentWriter for
serializing sarif diagnostics.
Uses clang::SarifDocumentWriter to generate SARIF output in the
StaticAnalyzer.
Various bugfixes are also made to clang::SarifDocumentWriter.
Summary of changes:
clang/lib/Basic/Sarif.cpp:
* Fix bug in adjustColumnPos introduced from prev move, it now uses
FullSourceLoc::getDecomposedExpansionLoc which provides the correct
location (in the presence of macros) instead of
FullSourceLoc::getDecomposedLoc.
* Fix createTextRegion so that it handles caret ranges correctly,
this should bring it to parity with the previous implementation.
clang/test/Analysis/diagnostics/Inputs/expected-sarif:
* Update the schema URL to the offical website
* Add the emitted defaultConfiguration sections to all rules
* Annotate results with the "level" property
clang/lib/StaticAnalyzer/Core/SarifDiagnostics.cpp:
* Update SarifDiagnostics class to hold a clang::SarifDocumentWriter
that it uses to convert diagnostics to SARIF.
We now skip the destruction of array elements for `delete[] p`,
if the value of `p` is UnknownVal and does not have corresponding region.
This eliminate the crash in `getDynamicElementCount` on that
region and matches the behavior for deleting the array of
non-constant range.
Reviewed By: isuckatcs
Differential Revision: https://reviews.llvm.org/D136671
This revision fixes typos where there are 2 consecutive words which are
duplicated. There should be no code changes in this revision (only
changes to comments and docs). Do let me know if there are any
undesirable changes in this revision. Thanks.
This was done as a test for D137302 and it makes sense to push these changes
Reviewed By: shafik
Differential Revision: https://reviews.llvm.org/D137491
The -fstrict-flex-arrays=3 is the most restrictive type of flex arrays.
No number, including 0, is allowed in the FAM. In the cases where a "0"
is used, the resulting size is the same as if a zero-sized object were
substituted.
This is needed for proper _FORTIFY_SOURCE coverage in the Linux kernel,
among other reasons. So while the only reason for specifying a
zero-length array at the end of a structure is for specify a FAM,
treating it as such will cause _FORTIFY_SOURCE not to work correctly;
__builtin_object_size will report -1 instead of 0 for a destination
buffer size to keep any kernel internals from using the deprecated
members as fake FAMs.
For example:
struct broken {
int foo;
int fake_fam[0];
struct something oops;
};
There have been bugs where the above struct was created because "oops"
was added after "fake_fam" by someone not realizing. Under
__FORTIFY_SOURCE, doing:
memcpy(p->fake_fam, src, len);
raises no warnings when __builtin_object_size(p->fake_fam, 1) returns -1
and may stomp on "oops."
Omitting a warning when using the (invalid) zero-length array is how GCC
treats -fstrict-flex-arrays=3. A warning in that situation is likely an
irritant, because requesting this option level is explicitly requesting
this behavior.
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836
Differential Revision: https://reviews.llvm.org/D134902
Discourse mail:
https://discourse.llvm.org/t/analyzer-why-do-we-suck-at-modeling-c-dynamic-memory/65667
malloc() returns a piece of uninitialized dynamic memory. We were (almost)
always able to model this behaviour. Its C++ counterpart, operator new is a
lot more complex, because it allows for initialization, the most complicated of which is the usage of constructors.
We gradually became better in modeling constructors, but for some reason, most
likely for reasons lost in history, we never actually modeled the case when the
memory returned by operator new was just simply uninitialized. This patch
(attempts) to fix this tiny little error.
Differential Revision: https://reviews.llvm.org/D135375
It turns out we can reach the `Init.castAs<nonlock::CompoundVal>()`
expression with other kinds of SVals. Such as by `nonloc::ConcreteInt`
in this example: https://godbolt.org/z/s4fdxrcs9
```lang=C++
int buffer[10];
void b();
void top() {
b(&buffer);
}
void b(int *c) {
*c = 42; // would crash
}
```
In this example, we try to store `42` to the `Elem{buffer, 0}`.
This situation can appear if the CallExpr refers to a function
declaration without prototype. In such cases, the engine will pick the
redecl of the referred function decl which has function body, hence has
a function prototype.
This weird situation will have an interesting effect to the AST, such as
the argument at the callsite will miss a cast, which would cast the
`int (*)[10]` expression into `int *`, which means that when we evaluate
the `*c = 42` expression, we want to bind `42` to an array, causing the
crash.
Look at the AST of the callsite with and without the function prototype:
https://godbolt.org/z/Gncebcbdb
The only difference is that without the proper function prototype, we
will not have the `ImplicitCastExpr` `BitCasting` from `int (*)[10]`
to `int *` to match the expected type of the parameter declaration.
In this patch, I'm proposing to emit a cast in the mentioned edge-case,
to bind the argument value of the expected type to the parameter.
I'm only proposing this if the runtime definition has exactly the same
number of parameters as the callsite feeds it by arguments.
If that's not the case, I believe, we are better off by binding `Unknown`
to those parameters.
Reviewed By: martong
Differential Revision: https://reviews.llvm.org/D136162
Previously, `LazyCompoundVal` bindings to subregions referred by
`LazyCopoundVals`, were not marked as //lazily copied//.
This change returns `LazyCompoundVals` from `getInterestingValues()`,
so their regions can be marked as //lazily copied// in `RemoveDeadBindingsWorker::VisitBinding()`.
Depends on D134947
Authored by: Tomasz Kamiński <tomasz.kamiński@sonarsource.com>
Reviewed By: martong
Differential Revision: https://reviews.llvm.org/D135136
