[libc++] Only forward-declare ABI-functions in exception_ptr.h if they are meant to be used

[itrofimow]

This patch fixes the unconditional forward-declarations of ABI-functions in exception_ptr.h, and makes it dependent on the availability macro, as it should've been from the beginning.
The declarations being unconditional break the build with libcxxrt before 045c52ce821388f4ae4d119fe4fb75f1eb547b85, now they are opt-out.

• libcxx/include/__exception/exception_ptr.h
  Only forward-declare ABI-functions if they are meant to be used.

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: None (itrofimow)

Changes

This patch fixes the unconditional fodward-declarations of ABI-functions in exception_ptr.h, and makes it dependendent on the availability macro, as it should've been from the beginning.
The declarations being unconditional break the build with libcxxrt before 045c52ce821388f4ae4d119fe4fb75f1eb547b85, now the are opt-out.

• libcxx/include/__exception/exception_ptr.h
  Only forward-declare ABI-functions if they are meant to be used.

---

Full diff: https://github.com/llvm/llvm-project/pull/84707.diff

1 Files Affected:

• (modified) libcxx/include/__exception/exception_ptr.h (+6-2)

diff --git a/libcxx/include/__exception/exception_ptr.h b/libcxx/include/__exception/exception_ptr.h
index 53e2f718bc1b35..c9027de9238cdd 100644
--- a/libcxx/include/__exception/exception_ptr.h
+++ b/libcxx/include/__exception/exception_ptr.h
@@ -26,6 +26,8 @@
 
 #ifndef _LIBCPP_ABI_MICROSOFT
 
+#  if _LIBCPP_AVAILABILITY_HAS_INIT_PRIMARY_EXCEPTION
+
 namespace __cxxabiv1 {
 
 extern "C" {
@@ -37,14 +39,16 @@ _LIBCPP_OVERRIDABLE_FUNC_VIS __cxa_exception* __cxa_init_primary_exception(
     void*,
     std::type_info*,
     void(
-#  if defined(_WIN32)
+#    if defined(_WIN32)
         __thiscall
-#  endif
+#    endif
             *)(void*)) throw();
 }
 
 } // namespace __cxxabiv1
 
+#  endif
+
 #endif
 
 namespace std { // purposefully not using versioning namespace

[itrofimow]

This

• builds with libcxxrt HEAD
• fails to build with libcxxrt prior to libcxxrt/libcxxrt@045c52c
• builds with libcxxrt prior to libcxxrt/libcxxrt@045c52c with _LIBCPP_AVAILABILITY_HAS_INIT_PRIMARY_EXCEPTION set to 0

I hope having a way to remove the conflicting forward-declaration would suffice, but if this continues to cause problem I'd be ok with the thing being reverted from libcxx, and I'd shamefully pretend it never happened.

Could you @ldionne please have a look?

[itrofimow]

The build failed for generic-optimized-speed, libcxx-runners-8-set with

Unexpectedly Passed Tests (1):
  llvm-libc++-shared.cfg.in :: std/experimental/simd/simd.class/simd_ctor_conversion.pass.cpp

doesn't seem related to me.

[frederick-vs-ja]

Pre-existing, no change requested: Should we replace these throw()'s with _NOEXCEPT? (perhaps in another PR)

[itrofimow]

I think we can do it in this PR, I can't see a way for a potential need to revert just throw() -> _NOEXCEPT.
Should I?

[ldionne]

I would keep the patch as-is just to separate concerns.

[ldionne]

Thanks, LGTM. The CI failure in simd is not your patch.

[ldionne]

I would keep the patch as-is just to separate concerns.