While debugging module support using -Wsystem-headers, we discovered that if
-Werror, and -Wundef or -Wmacro-redefined are specified, they can cause errors
to be generated in these builtin headers.
Differential Revision: https://reviews.llvm.org/D130800
and use fallback only for C.
It fixes the isssue with clang-cl:
```
#include <stdatomic.h>
#include <stdbool.h>
#ifdef __cplusplus
#include <atomic>
using namespace std;
#endif
int main() {
atomic_bool b = true;
}
```
```
$ clang-cl /TC main.cpp
# works
```
```
$ clang-cl /TP /std:c++20 main.cpp
stdatomic.h(70,6): error: conflicting types for 'atomic_thread_fence'
void atomic_thread_fence(memory_order);
^
atomic(166,24): note: previous definition is here
extern "C" inline void atomic_thread_fence(const memory_order _Order) noexcept {
...
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.
```
Many errors but
`<stdatomic.h>` has many macros to built-in functions.
```
#define atomic_thread_fence(order) __c11_atomic_thread_fence(order)
```
and MSVC `<atomic>` has real functions.
and the built-in functions are redefined.
Reviewed By: #libc, aaron.ballman, Mordante
Differential Revision: https://reviews.llvm.org/D130419
C++20 deprecated ATOMIC_FLAG_INIT thinking it was deprecated in C when it
wasn't. It is expected to be undeprecated in C++23 as part of LWG3659
(https://wg21.link/LWG3659), which is currently Tentatively Ready.
This handles the case where the user includes <stdatomic.h> in C++ code in a
freestanding compile mode. The corollary libc++ changes are in
1544d1f9fd.
C17 deprecated ATOMIC_VAR_INIT with the resolution of DR 485. C++
followed suit when adopting P0883R2 for C++20, but additionally chose
to deprecate ATOMIC_FLAG_INIT at the same time despite the macro still
being required in C. This patch marks both macros as deprecated when
appropriate to do so.
The 14.31.30818 toolset has the following in the `stdatomic.h`:
~~~
#ifndef __cplusplus
#error <stdatomic.h> is not yet supported when compiling as C, but this is planned for a future release.
#endif
~~~
This results in clang failing to build existing code which relied on
`stdatomic.h` in C mode on Windows. Simply fallback to the clang header
until that header is available as a complete implementation.
Summary:
These all had somewhat custom file headers with different text from the
ones I searched for previously, and so I missed them. Thanks to Hal and
Kristina and others who prompted me to fix this, and sorry it took so
long.
Reviewers: hfinkel
Subscribers: mcrosier, javed.absar, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D60406
llvm-svn: 357941
It reverts r331378 as it caused test failures
ThreadSanitizer-x86_64 :: Darwin/gcd-groups-destructor.mm
ThreadSanitizer-x86_64 :: Darwin/libcxx-shared-ptr-stress.mm
ThreadSanitizer-x86_64 :: Darwin/xpc-race.mm
Only clang part of the change is reverted, libc++ part remains as is because it
emits error less aggressively.
llvm-svn: 331392
Atomics in C and C++ are incompatible at the moment and mixing the
headers can result in confusing error messages.
Emit an error explicitly telling about the incompatibility. Introduce
the macro `__ALLOW_STDC_ATOMICS_IN_CXX__` that allows to choose in C++
between C atomics and C++ atomics.
rdar://problem/27435938
Reviewers: rsmith, EricWF, mclow.lists
Reviewed By: mclow.lists
Subscribers: jkorous-apple, christof, bumblebritches57, JonChesterfield, smeenai, cfe-commits
Differential Revision: https://reviews.llvm.org/D45470
llvm-svn: 331378
Summary: This patch makes the header `stdatomic.h` work when `-fms-compatibility` is specified.
Reviewers: rsmith
Reviewed By: rsmith
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D32322
llvm-svn: 300919
Adds a Clang-specific implementation of C11's stdatomic.h header. On systems,
such as FreeBSD, where a stdatomic.h header is already provided, we defer to
that header instead (using our __has_include_next technology). Otherwise, we
provide an implementation in terms of our __c11_atomic_* intrinsics (that were
created for this purpose).
C11 7.1.4p1 requires function declarations for atomic_thread_fence,
atomic_signal_fence, atomic_flag_test_and_set,
atomic_flag_test_and_set_explicit, and atomic_flag_clear, and requires that
they have external linkage. Accordingly, we provide these declarations, but if
a user elides the shadowing macros and uses them, then they must have a libc
(or similar) that actually provides definitions.
atomic_flag is implemented using _Bool as the underlying type. This is
consistent with the implementation provided by FreeBSD and also GCC 4.9 (at
least when __GCC_ATOMIC_TEST_AND_SET_TRUEVAL == 1).
Patch by Richard Smith (rebased and slightly edited by me -- Richard said I
should drive at this point).
llvm-svn: 218957
Dominic Chen