[libcxx-commits] [libcxx] 9a90aa0 - [libc++][modules] Add using_if_exists attribute (#77559) (#78909)

[via libcxx-commits]

Author: Gareth Williamson
Date: 2024-01-22T18:11:45+01:00
New Revision: 9a90aa01edfc5a56d975658a0cbbfa980a0ef7ed

URL: https://github.com/llvm/llvm-project/commit/9a90aa01edfc5a56d975658a0cbbfa980a0ef7ed
DIFF: https://github.com/llvm/llvm-project/commit/9a90aa01edfc5a56d975658a0cbbfa980a0ef7ed.diff

LOG: [libc++][modules] Add using_if_exists attribute (#77559) (#78909)

libc on macOS does not provide at_quick_exit or quick_exit. This allows
modules to build on macOS and defer any errors to usage site of these
symbols.

Fixes: https://github.com/llvm/llvm-project/issues/77559

Added: 
    

Modified: 
    libcxx/modules/std.compat/cstdlib.inc

Removed: 
    


################################################################################
diff  --git a/libcxx/modules/std.compat/cstdlib.inc b/libcxx/modules/std.compat/cstdlib.inc
index 9333d848707103d..a45a0a1caf8ba9a 100644
--- a/libcxx/modules/std.compat/cstdlib.inc
+++ b/libcxx/modules/std.compat/cstdlib.inc
@@ -16,10 +16,10 @@ export {
   // [support.start.term], start and termination
   using ::_Exit;
   using ::abort;
-  using ::at_quick_exit;
+  using ::at_quick_exit _LIBCPP_USING_IF_EXISTS;
   using ::atexit;
   using ::exit;
-  using ::quick_exit;
+  using ::quick_exit _LIBCPP_USING_IF_EXISTS;
 
   using ::getenv;
   using ::system;