[libc++] Fix extern C for __sanitizer_annotate_contiguous_container() (for gcc)

[azat]

Summary

gcc supports it only at the beginning:

$ g++ -o /dev/null -c /tmp/test_extern.cpp
$ cat /tmp/test_extern.cpp
extern "C" __attribute__ ((__visibility__("default"))) int foo();

Otherwise:

$ g++ -o /dev/null -c /tmp/test_extern.cpp
/tmp/test_extern.cpp:1:52: error: expected unqualified-id before string constant
    1 | __attribute__ ((__visibility__("default"))) extern "C" int foo();
      |                                                    ^~~
$ cat /tmp/test_extern.cpp
__attribute__ ((__visibility__("default"))) extern "C" int foo();

[ldionne]

@azat What version of GCC are you using?

[azat]

In D93316#2456101, @ldionne wrote:

@azat What version of GCC are you using?

10.2

And it seems that gcc had been always rejecting it
Yes this can be fixed in gcc, but in the mean time this patch looks simple enough, and it will allow using libc++ with gcc sanitizers

P.S. I've just verified versions from 4.x to 10 and all of them reject it (on godbolt)

[azat]

https://buildkite.com/llvm-project/diff-checks/builds/22546#42504dd5-9909-4d24-a94b-73413ec8839c

Please make sure you have the correct access rights
and the repository exists.')
INFO    Syncing local, origin and upstream...
INFO    Backing off reset_repository(...) for 2.4s (git.exc.GitCommandError: Cmd('git') failed due to: exit code(128)
  cmdline: git push origin main
  stderr: 'ERROR: You must verify your email address.
See https://github.com/settings/emails.
 
fatal: Could not read from remote repository.

@ldionne interesting is this about my email? I've just checked and it wasn't verified indeed (it seems that this verification status had been reset during one of github vulnerabilities)

[ldionne]

In D93316#2457276, @azat wrote:

https://buildkite.com/llvm-project/diff-checks/builds/22546#42504dd5-9909-4d24-a94b-73413ec8839c

Please make sure you have the correct access rights
and the repository exists.')
INFO    Syncing local, origin and upstream...
INFO    Backing off reset_repository(...) for 2.4s (git.exc.GitCommandError: Cmd('git') failed due to: exit code(128)
  cmdline: git push origin main
  stderr: 'ERROR: You must verify your email address.
See https://github.com/settings/emails.
 
fatal: Could not read from remote repository.

@ldionne interesting is this about my email? I've just checked and it wasn't verified indeed (it seems that this verification status had been reset during one of github vulnerabilities)

TBH, I don't know. It's the first time I see this. If you give me your Author Name <email@domain>, I can commit this for you.

[azat]

In D93316#2458806, @ldionne wrote:

TBH, I don't know. It's the first time I see this. If you give me your Author Name <email@domain>, I can commit this for you.

Azat Khuzhin <[e-mail]>

Thanks!

[azat]

Update patch after github email was verified

In attempt to fix [1]:

  Please make sure you have the correct access rights
  and the repository exists.')
  INFO    Syncing local, origin and upstream...
  INFO    Backing off reset_repository(...) for 2.4s (git.exc.GitCommandError: Cmd('git') failed due to: exit code(128)
    cmdline: git push origin main
    stderr: 'ERROR: You must verify your email address.
  See https://github.com/settings/emails.
   
  fatal: Could not read from remote repository.

[1]: https://buildkite.com/llvm-project/diff-checks/builds/22546#42504dd5-9909-4d24-a94b-73413ec8839c

libcxx/include/__config

 
 #if __has_attribute(no_destroy)
 #  define _LIBCPP_NO_DESTROY __attribute__((__no_destroy__))
 #else
 #  define _LIBCPP_NO_DESTROY
 #endif
 
 #ifndef _LIBCPP_HAS_NO_ASAN
-_LIBCPP_FUNC_VIS extern "C" void __sanitizer_annotate_contiguous_container(
+extern "C" _LIBCPP_FUNC_VIS void __sanitizer_annotate_contiguous_container(
   const void *, const void *, const void *, const void *);
 #endif
 
 // Try to find out if RTTI is disabled.
 #if defined(_LIBCPP_COMPILER_CLANG) && !__has_feature(cxx_rtti)
 #  define _LIBCPP_NO_RTTI
 #elif defined(__GNUC__) && !defined(__GXX_RTTI)
 #  define _LIBCPP_NO_RTTI