[libc++] Fix build failure with libdispatch backend

[ldionne]

We get an error "cannot add 'abi_tag' attribute in a redeclaration" because functions like __dispatch_apply are first declared without an ABI tag due to _LIBCPP_BEGIN_EXPLICIT_ABI_ANNOTATIONS inside the header, and then redeclared with an ABI tag in the .cpp file.

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Louis Dionne (ldionne)

Changes

We get an error "cannot add 'abi_tag' attribute in a redeclaration" because functions like __dispatch_apply are first declared without an ABI tag due to _LIBCPP_BEGIN_EXPLICIT_ABI_ANNOTATIONS inside the header, and then redeclared with an ABI tag in the .cpp file.

---

Full diff: https://github.com/llvm/llvm-project/pull/141606.diff

1 Files Affected:

• (modified) libcxx/src/pstl/libdispatch.cpp (+2)

diff --git a/libcxx/src/pstl/libdispatch.cpp b/libcxx/src/pstl/libdispatch.cpp
index 3dca702341c85..528018358eeb0 100644
--- a/libcxx/src/pstl/libdispatch.cpp
+++ b/libcxx/src/pstl/libdispatch.cpp
@@ -12,6 +12,7 @@
 #include <dispatch/dispatch.h>
 
 _LIBCPP_BEGIN_NAMESPACE_STD
+_LIBCPP_BEGIN_EXPLICIT_ABI_ANNOTATIONS
 namespace __pstl::__libdispatch {
 
 void __dispatch_apply(size_t chunk_count, void* context, void (*func)(void* context, size_t chunk)) noexcept {
@@ -29,4 +30,5 @@ __chunk_partitions __partition_chunks(ptrdiff_t element_count) noexcept {
 }
 
 } // namespace __pstl::__libdispatch
+_LIBCPP_END_EXPLICIT_ABI_ANNOTATIONS
 _LIBCPP_END_NAMESPACE_STD