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* [Bug c++/105584] New: libcxx needs using_if_exist attribute
@ 2022-05-12 16:49 unlvsur at live dot com
2022-05-12 16:53 ` [Bug c++/105584] " unlvsur at live dot com
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: unlvsur at live dot com @ 2022-05-12 16:49 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105584
Bug ID: 105584
Summary: libcxx needs using_if_exist attribute
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: unlvsur at live dot com
Target Milestone: ---
https://github.com/llvm/llvm-project/blob/14e83ada16b3944a4431617ed4ce7088f7f7cd9a/libcxx/include/__config#L772
#if __has_attribute(using_if_exists)
# define _LIBCPP_USING_IF_EXISTS __attribute__((using_if_exists))
#else
# define _LIBCPP_USING_IF_EXISTS
#endif
libcxx recently switches a lot of C usings with the new using_if_exists
attribute in clang, but GCC does not support it, causing compilation to fail if
these global definitions do not exist.
/home/cqwrteur/toolchains/native/x86_64-w64-mingw32/x86_64-w64-mingw32/include/c++/v1/cstdlib:139:9:
error: 'aligned_alloc' has not been declared in '::'
139 | using ::aligned_alloc _LIBCPP_USING_IF_EXISTS;
| ^~~~~~~~~~~~~
/home/cqwrteur/toolchains/native/x86_64-w64-mingw32/x86_64-w64-mingw32/include/c++/v1/ctime:75:9:
error: 'timespec_get' has not been declared in '::'
75 | using ::timespec_get _LIBCPP_USING_IF_EXISTS;
| ^~~~~~~~~~~~
I think GCC should add this attribute to support libcxx correctly.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/105584] libcxx needs using_if_exist attribute
2022-05-12 16:49 [Bug c++/105584] New: libcxx needs using_if_exist attribute unlvsur at live dot com
@ 2022-05-12 16:53 ` unlvsur at live dot com
2022-05-12 16:57 ` unlvsur at live dot com
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: unlvsur at live dot com @ 2022-05-12 16:53 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105584
--- Comment #1 from cqwrteur <unlvsur at live dot com> ---
[clang] Implement the using_if_exists attribute
https://github.com/llvm/llvm-project/commit/369c64839946d89cf5697550b6feeea031b2f270
This shows how the attribute works. Hope GCC could add it.
Also probably need __clang__::__using_if_exists__ too to avoid name collisions.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/105584] libcxx needs using_if_exist attribute
2022-05-12 16:49 [Bug c++/105584] New: libcxx needs using_if_exist attribute unlvsur at live dot com
2022-05-12 16:53 ` [Bug c++/105584] " unlvsur at live dot com
@ 2022-05-12 16:57 ` unlvsur at live dot com
2022-05-12 18:27 ` redi at gcc dot gnu.org
2022-10-20 14:08 ` vital.had at gmail dot com
3 siblings, 0 replies; 5+ messages in thread
From: unlvsur at live dot com @ 2022-05-12 16:57 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105584
--- Comment #2 from cqwrteur <unlvsur at live dot com> ---
https://lists.llvm.org/pipermail/cfe-dev/2020-June/066038.html
According to the proposal, it looks like this attribute could benefit libstdc++
too since I do see similar issues before.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/105584] libcxx needs using_if_exist attribute
2022-05-12 16:49 [Bug c++/105584] New: libcxx needs using_if_exist attribute unlvsur at live dot com
2022-05-12 16:53 ` [Bug c++/105584] " unlvsur at live dot com
2022-05-12 16:57 ` unlvsur at live dot com
@ 2022-05-12 18:27 ` redi at gcc dot gnu.org
2022-10-20 14:08 ` vital.had at gmail dot com
3 siblings, 0 replies; 5+ messages in thread
From: redi at gcc dot gnu.org @ 2022-05-12 18:27 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105584
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Severity|normal |enhancement
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
libc++ should be using __has_cpp_attribute if they still expect to build with
GCC.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/105584] libcxx needs using_if_exist attribute
2022-05-12 16:49 [Bug c++/105584] New: libcxx needs using_if_exist attribute unlvsur at live dot com
` (2 preceding siblings ...)
2022-05-12 18:27 ` redi at gcc dot gnu.org
@ 2022-10-20 14:08 ` vital.had at gmail dot com
3 siblings, 0 replies; 5+ messages in thread
From: vital.had at gmail dot com @ 2022-10-20 14:08 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105584
Sergey Fedorov <vital.had at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |vital.had at gmail dot com
--- Comment #4 from Sergey Fedorov <vital.had at gmail dot com> ---
(In reply to Jonathan Wakely from comment #3)
> libc++ should be using __has_cpp_attribute if they still expect to build
> with GCC.
Wouldn’t it benefit GCC if we add extra support?
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2022-10-20 14:08 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2022-05-12 16:49 [Bug c++/105584] New: libcxx needs using_if_exist attribute unlvsur at live dot com
2022-05-12 16:53 ` [Bug c++/105584] " unlvsur at live dot com
2022-05-12 16:57 ` unlvsur at live dot com
2022-05-12 18:27 ` redi at gcc dot gnu.org
2022-10-20 14:08 ` vital.had at gmail dot com
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