Use `getElementAsAPInt(`) to read array elements and emit via
`addIntAsBlock()` which handles target endianness correctly, instead of
`getRawDataValues()` which exposes host endianness. This fixes test
failures on big-endian hosts cross-compiling for little-endian targets.
Reland of #182442 with endianness fix.
Clang does not emit a `DW_AT_const_value` in DWARF, while GCC does. This
patch fixes this issue through handling Array `APValues` and respective
handling in the backend through `ConstantDataSequential`
Fixes#165220
Discussion is a follow-up from
https://github.com/llvm/llvm-project/issues/182762#issuecomment-3965207289
(where we're discussing how LLDB could make use of this symbol for
vtable detection).
`_vtable$` is not a reserved identifier in C or C++. In order for
debuggers to reliably use this symbol without accidentally reaching into
user-identifiers, this patch renames it such that it is reserved. The
naming follows the style of the recently added `__clang_trap_msg`
debug-info symbol.
Before this change, HIP applications compiled with AMD clang would set
the `DW_AT_language` field to `DW_LANG_C_plus_plus_14`:
```
llvm-dwarfdump hello
hello: file format elf64-x86-64
.debug_info contents:
0x00000000: ...
0x0000000c: DW_TAG_compile_unit
...
------> DW_AT_language (DW_LANG_C_plus_plus_14)
DW_AT_name ("helloworld.cpp")
...
```
This change update the language tag to `DW_LANG_HIP` for these
applications:
```
llvm-dwarfdump hello
hello: file format elf64-x86-64
.debug_info contents:
0x00000000: ...
0x0000000c: DW_TAG_compile_unit
...
------> DW_AT_language (DW_LANG_HIP)
DW_AT_name ("helloworld.cpp")
...
```
Also added a test to check for the new tag
(`debug-info-language-hip.hip`).
The primary motivation for this change is that ROCgdb has to use a
workaround to detect that a program is a HIP application. This removes
the guessing and allows proper detection of the HIP language.
ROCgdb [already has support for
DW_LANG_HIP](https://github.com/ROCm/ROCgdb/commit/316e8393f2ad).
Given the test case:
struct CBase {
virtual void foo();
};
void bar(CBase *Base) {
Base->foo();
}
and using '-emit-call-site-info' with llc, the following DWARF
is produced for the indirect call 'Base->foo()':
1$: DW_TAG_structure_type "CBase"
...
2$: DW_TAG_subprogram "foo"
...
3$: DW_TAG_subprogram "bar"
...
4$: DW_TAG_call_site
...
We add DW_AT_LLVM_virtual_call_origin to existing call-site
information, linking indirect calls to the function-declaration
they correspond to.
4$: DW_TAG_call_site
...
DW_AT_LLVM_virtual_call_origin (2$ "_ZN5CBase3fooEv")
The new attribute DW_AT_LLVM_virtual_call_origin helps to
address the ambiguity to any consumer due to the usage of
DW_AT_call_origin.
The functionality is available to all supported debuggers and
it is generated only for DWARF version 5 or greater.
Introduce `OverflowBehaviorType` (OBT), a new type attribute in Clang
that provides developers with fine-grained control over the overflow
behavior of integer types. This feature allows for a more nuanced
approach to integer safety, achieving better granularity than global
compiler flags like `-fwrapv` and `-ftrapv`. Type specifiers are also
available as keywords `__ob_wrap` and `__ob_trap`.
These can be applied to integer types (both signed and unsigned) as well
as typedef declarations, where the behavior is one of the following:
* `wrap`: Guarantees that arithmetic operations on the type will wrap on
overflow, similar to `-fwrapv`. This suppresses UBSan's integer overflow
checks for the attributed type and prevents eager compiler
optimizations.
* `trap`: Enforces overflow checking for the type, even when global
flags like `-fwrapv` would otherwise suppress it.
A key aspect of this feature is its interaction with existing
mechanisms. `OverflowBehaviorType` takes precedence over global flags
and, notably, over entries in the Sanitizer Special Case List (SSCL).
This allows developers to "allowlist" critical types for overflow
instrumentation, even if they are disabled by a broad rule in an SSCL.
Signed-off-by: Justin Stitt <justinstitt@google.com>
…n in DWARF. (#167666)"
This reverts commit 418ba6e8ae2cde7924388142b8ab90c636d2c21f.
The commit caused an ICE due to hitting unreachable in
llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp:1307
Fixes#182337
Given the test case:
struct CBase {
virtual void foo();
};
void bar(CBase *Base) {
Base->foo();
}
and using '-emit-call-site-info' with llc, the following DWARF
is produced for the indirect call 'Base->foo()':
1$: DW_TAG_structure_type "CBase"
...
2$: DW_TAG_subprogram "foo"
...
3$: DW_TAG_subprogram "bar"
...
4$: DW_TAG_call_site
...
We add DW_AT_LLVM_virtual_call_origin to existing call-site
information, linking indirect calls to the function-declaration
they correspond to.
4$: DW_TAG_call_site
...
DW_AT_LLVM_virtual_call_origin (2$ "_ZN5CBase3fooEv")
The new attribute DW_AT_LLVM_virtual_call_origin helps to
address the ambiguity to any consumer due to the usage of
DW_AT_call_origin.
The functionality is available to all supported debuggers.
[Clang][DebugInfo] Add a flag to use expansion loc for macro params.
This patch adds a flag to allow users to preserve the old behaviour -
use the macro expansion location for parameters. This is useful for
wider testing of sample profile driven PGO which relies on debug
information based mapping. This flag is intended to be temporary
and should be safe to remove by EOY 2026. Filed #175249 to
track the cleanup.
---------
Assisted-by: Gemini
This reverts commit
54a4da9df6.
MSVC supports an extension allowing to delete an array of objects via
pointer whose static type doesn't match its dynamic type. This is done
via generation of special destructors - vector deleting destructors.
MSVC's virtual tables always contain a pointer to the vector deleting
destructor for classes with virtual destructors, so not having this
extension implemented causes clang to generate code that is not
compatible with the code generated by MSVC, because clang always puts a
pointer to a scalar deleting destructor to the vtable. As a bonus the
deletion of an array of polymorphic object will work just like it does
with MSVC - no memory leaks and correct destructors are called.
This patch will cause clang to emit code that is compatible with code
produced by MSVC but not compatible with code produced with clang of
older versions, so the new behavior can be disabled via passing
-fclang-abi-compat=21 (or lower).
Fixes https://github.com/llvm/llvm-project/issues/19772
The enum cases for `SuppressInlineNamespaceMode` leaked into the rest of
`PrintingPolicy`, meaning if we wanted to introduce another enum (which
I'm planning on doing in an unrelated PR), then `All`/`None`/`Redundant`
are all already taken, which are quite useful names.
This patch turns `SuppressInlineNamespaceMode` into an `enum class`,
freeing up the names for use by other future enums in `PrintingPolicy`.
Unfortunately that means we have to cast the values when assigning to
`PrintingPolicy::SuppressInlineNamespace`, because its actual type is
`unsigned`. But if we ever make the bitfields have proper enumeration
types (which AFAIU is dependent on an MSVC codegen fix), then we can get
rid of those casts.
While doing this I found three instances of assigning booleans to
`SuppressInlineNamespace`. I added a FIXME in LLDB to check what the
intended value of the enum should be.
This adds a default enabled flag to control attachment of call site
debug info. `-gno-call-site-info` can be used to disable this feature
when needed.
This should help those concerned about debug info size in
https://github.com/llvm/llvm-project/issues/168851.
Depends on:
* https://github.com/llvm/llvm-project/pull/168382
As of recent, LLVM includes the bit-size as a `DW_AT_bit_size` (and as
part of `DW_AT_name`) of `_BitInt`s in DWARF. This allows us to mark
`_BitInt`s as "reconstitutable" when compiling with
`-gsimple-template-names`. We still only omit template parameters that
are `<= 64` bit wide. So support `_BitInt`s larger than 64 bits is not
part of this patch.
MSVC supports an extension allowing to delete an array of objects via
pointer whose static type doesn't match its dynamic type. This is done
via generation of special destructors - vector deleting destructors.
MSVC's virtual tables always contain a pointer to the vector deleting
destructor for classes with virtual destructors, so not having this
extension implemented causes clang to generate code that is not
compatible with the code generated by MSVC, because clang always puts a
pointer to a scalar deleting destructor to the vtable. As a bonus the
deletion of an array of polymorphic object will work just like it does
with MSVC - no memory leaks and correct destructors are called.
This patch will cause clang to emit code that is compatible with code
produced by MSVC but not compatible with code produced with clang of
older versions, so the new behavior can be disabled via passing
-fclang-abi-compat=21 (or lower).
This is yet another attempt to land vector deleting destructors support
originally implemented by
https://github.com/llvm/llvm-project/pull/133451.
This PR contains fixes for issues reported in the original PR as well as
fixes for issues related to operator delete[] search reported in several
issues like
https://github.com/llvm/llvm-project/pull/133950#issuecomment-2787510484https://github.com/llvm/llvm-project/issues/134265
Fixes https://github.com/llvm/llvm-project/issues/19772
`DISubprogram`s are attached to call sites to support various debug info
features, including entry values and tail calls. Clang 9.0
(0f6516856670a435461f56a9faeb4aa8a35a6679) was the first version to
include this kind of call site `DISubprogram` attachment.
This earlier work appears to visit only some call site variants,
however. The call site attachment was added to a higher-level `EmitCall`
path in Clang's code gen that is only used by some call variants. In
particular, some C++ member calls use a different code gen path, which
did not include this call site attachment step, and thus the debug info
it triggers (e.g. call site entries) was not emitted for such calls.
This moves `DISubprogram` attachment to a lower-level call emission path
that is used by all call variants.
Fixes https://github.com/llvm/llvm-project/issues/161962
DW_TAG_base_type DIEs are permitted to have both byte_size and bit_size
attributes "If the value of an object of the given type does not fully
occupy the storage described by a byte size attribute"
* Add DataSizeInBits to DIBasicType (`DIBasicType(... dataSize: n ...)` in IR).
* Change Clang to add DataSizeInBits to _BitInt type metadata.
* Change LLVM to add DW_AT_bit_size to base_type DIEs that have non-zero
DataSizeInBits.
TODO: Do we need to emit DW_AT_data_bit_offset for big endian targets?
See discussion on the PR.
Fixes [#61952](https://github.com/llvm/llvm-project/issues/61952)
---------
Co-authored-by: David Stenberg <david.stenberg@ericsson.com>
In the past we used to only mark variables artificial that were
`isImplicit`. We would also omit the location information if the
variable's parent was implicit. Since
https://github.com/llvm/llvm-project/pull/100355 we made the logic to
mark variables as artificial the same as determining whether to omit its
location or not. This was to support binding variable declarations,
which we would like to have line information for (and don't want to mark
artificial as they are explicitly named in source).
However, this doesn't quite do the expected for parameters of
Objective-C synthesised property accessors. An Objective-C setter will
have an explicit parameter, which is the ivar to write to. However,
because the parent (i.e., the synthesised method) is artificial, we now
mark that parameter artificial. This is example debug-info for such an
accessor:
```
0x00000118: DW_TAG_subprogram
DW_AT_low_pc (0x0000000000000044)
DW_AT_high_pc (0x0000000000000078)
DW_AT_frame_base (DW_OP_reg29 W29)
DW_AT_object_pointer (0x00000128)
DW_AT_specification (0x00000068 "-[Foo setFooProp:]")
0x00000128: DW_TAG_formal_parameter
DW_AT_location (DW_OP_fbreg -8)
DW_AT_name ("self")
DW_AT_type (0x00000186 "Foo *")
DW_AT_artificial (true)
0x00000131: DW_TAG_formal_parameter
DW_AT_location (DW_OP_breg31 WSP+16)
DW_AT_name ("_cmd")
DW_AT_type (0x0000018b "SEL")
DW_AT_artificial (true)
0x0000013a: DW_TAG_formal_parameter
DW_AT_location (DW_OP_breg31 WSP+8)
DW_AT_name ("fooProp")
DW_AT_type (0x000000aa "id")
DW_AT_artificial (true)
```
Note how the `fooProp` parameter is marked artificial, although it
technically is an explicitly passed parameter. We want to treat the
synthesised method like any other, where explicitly passed parameters
aren't artificial. But we do want to omit the file/line info because it
doesn't exist in the source.
This patch prevents such parameters from being marked artificial. We
could probably generalise this to any kind of synthesised method, not
just Objective-C. But I'm currently not aware of such synthesised
functions, so made it Objective-C specific for now for testability.
*Motivator*
Marking such parameters artificial makes LLDB fail to parse the ObjC
method and emit an error such as:
```
error: Foo.o [0x00000000000009d7]: invalid Objective-C method DW_TAG_subprogram (DW_TAG_subprogram), please file a bug and attach the file at the start of this error message
```
rdar://163063569
Depends on:
* https://github.com/llvm/llvm-project/pull/163348
* https://github.com/llvm/llvm-project/pull/162632
With this patch Clang will start emitting `DW_AT_language_{name,
version}` for C++/C/Objective-C/Objective-C++ when using `-gdwarf-6`. We
adjust the `DISourceLanguageName` (which we pass to `DICompileUnit`) to
hold a `DW_AT_language_name_` and version code when in DWARFv6.
Otherwise we continue using the `DW_LANG_` version of
`DISourceLanguageName`.
We didn't back-port emitting
`DW_AT_language_name`/`DW_AT_language_version` to DWARFv5 (unlike GCC,
which emits both the new and old language attributes in DWARFv5) because
there wasn't a compelling reason to do so (yet).
This rename was made as part of
https://github.com/llvm/llvm-project/pull/147835 in order to ease
rebasing the PR, and give a nice window for other patches to get rebased
as well.
It has been a while already, so lets go ahead and rename it back.
This patch sets up `DICompileUnit` to support the DWARFv6
`DW_AT_language_name` and `DW_AT_language_version` attributes (which are
set to replace `DW_AT_language`). This patch changes the
`DICompileUnit::SourceLanguage` field type to a `DISourceLanguageName`
that encapsulates the notion of "versioned vs. unversioned name". A
"versioned" name is one that has an associated version stored separately
in `DISourceLanguageName::Version`.
This patch just changes all the clients of the `getSourceLanguage` API
to the expect a `DISourceLanguageName`. Currently they all just `assert`
(via `DISourceLanguageName::getUnversionedName`) that we're dealing with
"unversioned names" (i.e., the pre-DWARFv6 language codes). In follow-up
patches (e.g., draft is at
https://github.com/llvm/llvm-project/pull/162261), when we start
emitting versioned language codes, the `getUnversionedName` calls can
then be adjusted to `getName`.
**Implementation considerations**
* We could have added a new member to `DICompileUnit` alongside the
existing `SourceLanguage` field. I don't think this would have made the
transition any simpler (clients would still need to be aware of
"versioned" vs. "unversioned" language names). I felt that encapsulating
this inside a `DISourceLanguageName` was easier to reason about for
maintainers.
* Currently DISourceLanguageName is a `12` byte structure. We could
probably pack all the info inside a `uint64_t` (16-bits for the name,
32-bits for the version, 1-bit for answering the `hasVersionedName`).
Just to keep the prototype simple I used a `std::optional`. But since
the guts of the structure are hidden, we can always change the layout to
a more compact representation instead.
**How to review**
* The new `DISourceLanguageName` structure is defined in
`DebugInfoMetadata.h`. All the other changes fall out from changing the
`DICompileUnit::SourceLanguage` from `unsigned` to
`DISourceLanguageName`.
This reverts commit 99a29f640809f32d1271ed5cac9764b839daeed1.
Original change was reverted because following assertion started firing:
```
clang++: clang/include/clang/AST/LambdaCapture.h:105: ValueDecl
*clang::LambdaCapture::getCapturedVar() const: Assertion
`capturesVariable() && "No variable available for capture"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.Program arguments: ../../prebuilt/third_party/clang/custom/bin/clang++ -MD -MF host_x64/obj/third_party/android/platform/system/libbase/libbase.logging.cpp.o.d -D_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS -D_LIBCPP_REMOVE_TRANSITIVE_INCLUDES -I../.. -Ihost_x64/gen -I../../third_party/android/platform/system/libbase/include -I../../third_party/fmtlib/src/include -I../../third_party/android/platfo...com
1.<eof> parser at end of file
2.Per-file LLVM IR generation
clang++: error: clang frontend command failed with exit code 134 (use -v
to see invocation)
Fuchsia clang version 22.0.0git
(https://llvm.googlesource.com/llvm-project
8553bd2b29ad2b17a9a884f14da6c43b606ec776)
********************
```
The relanded patch just adds a `Capture.capturesVariable()` check before calling `getCapturedVar`. That's what the code did before the refactor.
This patch creates a helper to retrieve the name from a lambda capture
and only calls `createFieldType` once.
This will simplify reviewing some upcoming changes in this function.
The debug info for VTables introduced in #130255 was temporarily
disabled on COFF platforms by #151684, due to the risk of emitting
dangling relocations (see also:
https://github.com/llvm/llvm-project/issues/149639#issuecomment-3114257062
).
This patch re-enables that debug info and adds a guard to prevent
emitting dangling relocations by checking whether the VTable definition
is actually emitted.
Resolves#149639
Depends on https://github.com/llvm/llvm-project/pull/154137
This patch is motivated by
https://github.com/llvm/llvm-project/pull/149827, where we plan on using
mangled names on structor declarations to find the exact structor
definition that LLDB's expression evaluator should call.
Given a `DW_TAG_subprogram` for a function declaration, the most
convenient way for a debugger to find the corresponding definition is to
use the `DW_AT_linkage_name` (i.e., the mangled name). However, we
currently can't do that for constructors/destructors because Clang
doesn't attach linkage names to them. This is because, depending on ABI,
there can be multiple definitions for a single constructor/destructor
declaration. The way GCC works around this is by producing a `C4`/`D4`
"unified" mangling for structor declarations (see
[godbolt](https://godbolt.org/z/Wds6cja9K)). GDB uses this to locate the
relevant definitions.
This patch aligns Clang with GCC's DWARF output and allows us to
implement the same lookup scheme in LLDB.
When a typedef is declared within a templated class, clang incorrectly
assigns the typedef to the compilation unit (CU) scope rather than the
intended scope of the templated class. This issue arises because, during
the creation of the typedef, the context lookup in the RegionMap fails
to locate the templated class, despite its prior creation.
The problem stems from the way the context is stored in the RegionMap.
When handling templated types, the current implementation stores the
class specialization rather than the templated declaration itself. This
leads to a mismatch when attempting to retrieve the context for the
typedef.
To address this issue, the solution involves modifying the
CreatedLimitedType() function. Specifically, when a struct or class is a
templated type, we should store the actual templated declaration in the
RegionMap instead of the class specialization. This ensures that
subsequent lookups for context, such as those needed for typedef
declarations, correctly identify the templated class scope.
Fixes https://github.com/llvm/llvm-project/issues/91451
This is a major change on how we represent nested name qualifications in
the AST.
* The nested name specifier itself and how it's stored is changed. The
prefixes for types are handled within the type hierarchy, which makes
canonicalization for them super cheap, no memory allocation required.
Also translating a type into nested name specifier form becomes a no-op.
An identifier is stored as a DependentNameType. The nested name
specifier gains a lightweight handle class, to be used instead of
passing around pointers, which is similar to what is implemented for
TemplateName. There is still one free bit available, and this handle can
be used within a PointerUnion and PointerIntPair, which should keep
bit-packing aficionados happy.
* The ElaboratedType node is removed, all type nodes in which it could
previously apply to can now store the elaborated keyword and name
qualifier, tail allocating when present.
* TagTypes can now point to the exact declaration found when producing
these, as opposed to the previous situation of there only existing one
TagType per entity. This increases the amount of type sugar retained,
and can have several applications, for example in tracking module
ownership, and other tools which care about source file origins, such as
IWYU. These TagTypes are lazily allocated, in order to limit the
increase in AST size.
This patch offers a great performance benefit.
It greatly improves compilation time for
[stdexec](https://github.com/NVIDIA/stdexec). For one datapoint, for
`test_on2.cpp` in that project, which is the slowest compiling test,
this patch improves `-c` compilation time by about 7.2%, with the
`-fsyntax-only` improvement being at ~12%.
This has great results on compile-time-tracker as well:
This patch also further enables other optimziations in the future, and
will reduce the performance impact of template specialization resugaring
when that lands.
It has some other miscelaneous drive-by fixes.
About the review: Yes the patch is huge, sorry about that. Part of the
reason is that I started by the nested name specifier part, before the
ElaboratedType part, but that had a huge performance downside, as
ElaboratedType is a big performance hog. I didn't have the steam to go
back and change the patch after the fact.
There is also a lot of internal API changes, and it made sense to remove
ElaboratedType in one go, versus removing it from one type at a time, as
that would present much more churn to the users. Also, the nested name
specifier having a different API avoids missing changes related to how
prefixes work now, which could make existing code compile but not work.
How to review: The important changes are all in
`clang/include/clang/AST` and `clang/lib/AST`, with also important
changes in `clang/lib/Sema/TreeTransform.h`.
The rest and bulk of the changes are mostly consequences of the changes
in API.
PS: TagType::getDecl is renamed to `getOriginalDecl` in this patch, just
for easier to rebasing. I plan to rename it back after this lands.
Fixes#136624
Fixes https://github.com/llvm/llvm-project/issues/43179
Fixes https://github.com/llvm/llvm-project/issues/68670
Fixes https://github.com/llvm/llvm-project/issues/92757
On COFF platform, d1b0cbff806b50d399826e79b9a53e4726c21302 generates a
debug info linked with VTable regardless definition is present or not.
If that VTable ends up implicitly dllimported from another DLL, ld.bfd
produces a runtime pseudo relocation for it (LLD doesn't, since
d17db6066d2524856fab493dd894f8396e896bc7). If the debug section is
stripped, the runtime pseudo relocation points to memory space outside
of the module, causing an access violation.
At this moment, we simply disable VTable debug info on COFF platform to
avoid this problem.
Consider this declaration:
`int foo();`
This function is described in LLVM with `clang::FunctionNoProtoType`
class. ([See
description](https://clang.llvm.org/doxygen/classclang_1_1FunctionNoProtoType.html))
Judging by [this
comment](a1bf0d1394/clang/lib/CodeGen/CGCall.cpp (L159C11-L159C12))
all such functions are treated like functions with variadic number of
parameters.
When we want to [emit debug
info](0a8ddd3965/clang/lib/CodeGen/CGDebugInfo.cpp (L4808))
we have to know function that we calling.
In method
[getCalledFunction()](0a8ddd3965/llvm/include/llvm/IR/InstrTypes.h (L1348))
we compare two types of function:
1. Function that we deduce from calling operand, and
2. Function that we store locally
If they differ we get `nullptr` and can't emit appropriate debug info.
The only thing they differ is: lhs function is variadic, but rhs
function isn't
Reason of this difference is that under RISC-V there is no overridden
function that tells us about treating functions with no parameters.
[Default
function](0a8ddd3965/clang/lib/CodeGen/TargetInfo.cpp (L87))
always return `false`.
This patch overrides this function for RISC-V
CWD is queried in clang driver and passed to clang cc1 via flags when
needed. Respect the cc1 flags and do not repeated checking current
working directory in CodeGen.
The -gline-tables-only option emits minimal debug info for functions,
files and line numbers while omitting variables, parameters and most
type information. VTable debug symbols are emitted to facilitate a
debugger's ability to perform automatic type promotion on variables and
parameters. With variables and parameters being omitted, the VTable
symbols are unnecessary.
This patch adds a human readable trap category and message to UBSan
traps. The category and message are encoded in a fake frame in the debug
info where the function is a fake inline function where the name encodes
the trap category and message. This is the same mechanism used by
Clang’s `__builtin_verbose_trap()`.
This change allows consumers of binaries built with trapping UBSan to
more easily identify the reason for trapping. In particular LLDB already
has a frame recognizer that recognizes the fake function names emitted
in debug info by this patch. A patch testing this behavior in LLDB will
be added in a separately.
The human readable trap messages are based on the messages currently
emitted by the userspace runtime for UBSan in compiler-rt. Note the
wording is not identical because the userspace UBSan runtime has access
to dynamic information that is not available during Clang’s codegen.
Test cases for each UBSan trap kind are included.
This complements the [`-fsanitize-annotate-debug-info`
feature](https://github.com/llvm/llvm-project/pull/141997). While
`-fsanitize-annotate-debug-info` attempts to annotate all UBSan-added
instructions, this feature (`-fsanitize-debug-trap-reasons`) only
annotates the final trap instruction using SanitizerHandler information.
This work is part of a GSoc 2025 project.
The checks for the 'z' and 't' format specifiers added in the original
PR #143653 had some issues and were overly strict, causing some build
failures and were consequently reverted at
4c85bf2fe8.
In the latest commit
27c58629ec,
I relaxed the checks for the 'z' and 't' format specifiers, so warnings
are now only issued when they are used with mismatched types.
The original intent of these checks was to diagnose code that assumes
the underlying type of `size_t` is `unsigned` or `unsigned long`, for
example:
```c
printf("%zu", 1ul); // Not portable, but not an error when size_t is unsigned long
```
However, it produced a significant number of false positives. This was
partly because Clang does not treat the `typedef` `size_t` and
`__size_t` as having a common "sugar" type, and partly because a large
amount of existing code either assumes `unsigned` (or `unsigned long`)
is `size_t`, or they define the equivalent of size_t in their own way
(such as
sanitizer_internal_defs.h).2e67dcfdcd/compiler-rt/lib/sanitizer_common/sanitizer_internal_defs.h (L203)
Including the results of `sizeof`, `sizeof...`, `__datasizeof`,
`__alignof`, `_Alignof`, `alignof`, `_Countof`, `size_t` literals, and
signed `size_t` literals, the results of pointer-pointer subtraction and
checks for standard library functions (and their calls).
The goal is to enable clang and downstream tools such as clangd and
clang-tidy to provide more portable hints and diagnostics.
The previous discussion can be found at #136542.
This PR implements this feature by introducing a new subtype of `Type`
called `PredefinedSugarType`, which was considered appropriate in
discussions. I tried to keep `PredefinedSugarType` simple enough yet not
limited to `size_t` and `ptrdiff_t` so that it can be used for other
purposes. `PredefinedSugarType` wraps a canonical `Type` and provides a
name, conceptually similar to a compiler internal `TypedefType` but
without depending on a `TypedefDecl` or a source file.
Additionally, checks for the `z` and `t` format specifiers in format
strings for `scanf` and `printf` were added. It will precisely match
expressions using `typedef`s or built-in expressions.
The affected tests indicates that it works very well.
Several code require that `SizeType` is canonical, so I kept `SizeType`
to its canonical form.
The failed tests in CI are allowed to fail. See the
[comment](https://github.com/llvm/llvm-project/pull/135386#issuecomment-3049426611)
in another PR #135386.
The verifier check was in the wrong place, meaning it wasn't actually
checking many instructions.
Fixing that causes a test failure (coro-dwarf-key-instrs.cpp) because
coros turn off the feature but still annotate instructions with the
metadata (which is a supported situation, but the verifier doesn't like
it, and it's hard to teach the verifier to like it).
Fix that by avoiding emitting any key instruction metadata if the
DISubprogram has opted out of key instructions.
Some `LangOptions` duplicate their `CodeGenOptions` counterparts. My
understanding is that this was done solely because some infrastructure
(like preprocessor initialization, serialization, module compatibility
checks, etc.) were only possible/convenient for `LangOptions`. This PR
implements the missing support for `CodeGenOptions`, which makes it
possible to remove some duplicate `LangOptions` fields and simplify the
logic. Motivated by https://github.com/llvm/llvm-project/pull/146342.
