[libcxxabi] Always link against libzircon for Fuchsia targets

[ilovepi]

When using LTO, the deplibs mechanism is insufficient to ensure that libzircon
is always brought into the link prior to LTO code generation. The general
problem is discussed in depth in
#56070

To work around this, we can just provide libzircon as a link input.

[llvmbot]

@llvm/pr-subscribers-libcxxabi

Author: Paul Kirth (ilovepi)

Changes

When using LTO, the deplibs mechanism is insufficient to ensure that libzircon
is always brought into the link prior to LTO code generation. The general
problem is discussed in depth in
#56070

To work around this, we can just provide libzircon as a link input.

---

Full diff: https://github.com/llvm/llvm-project/pull/115910.diff

1 Files Affected:

• (modified) libcxxabi/src/CMakeLists.txt (+4)

diff --git a/libcxxabi/src/CMakeLists.txt b/libcxxabi/src/CMakeLists.txt
index 84fe2784bec5ca..5a384c5345d755 100644
--- a/libcxxabi/src/CMakeLists.txt
+++ b/libcxxabi/src/CMakeLists.txt
@@ -75,6 +75,10 @@ if (NOT APPLE) # On Apple platforms, we always use -nostdlib++ so we don't need
   add_library_flags_if(LIBCXXABI_HAS_C_LIB c)
 endif()
 
+if (FUCHSIA)
+    add_library_flags(zircon)
+endif()
+
 if (NOT LIBCXXABI_USE_COMPILER_RT)
   add_library_flags_if(LIBCXXABI_HAS_GCC_LIB gcc)
 endif()

[petrhosek]

I'd leave a TODO comment to use https://cmake.org/cmake/help/latest/variable/CMAKE_LINK_LIBRARY_USING_FEATURE.html once LLVM requires CMake at least 3.24.

[ilovepi]

done.

[MaskRay]

TODO: $upper_case is more common than TODO

[ilovepi]

Good catch. Thx.

[ilovepi]

ping. Can someone for @llvm/reviewers-libcxxabi take a look at this please?

[ilovepi]

ping