[libunwind] [libunwind] Use -nostdlib++ when linking libunwind (PR #75646)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libunwind

Author: Louis Dionne (ldionne)

<details>
<summary>Changes</summary>

We shouldn't need to link against libc++ or libc++abi when building libunwind, since that would otherwise be a circular dependency.

---
Full diff: https://github.com/llvm/llvm-project/pull/75646.diff


1 Files Affected:

- (modified) libunwind/src/CMakeLists.txt (+10-9) 


``````````diff
diff --git a/libunwind/src/CMakeLists.txt b/libunwind/src/CMakeLists.txt
index abb019b88ebabd..c0e60f29a3db25 100644
--- a/libunwind/src/CMakeLists.txt
+++ b/libunwind/src/CMakeLists.txt
@@ -66,20 +66,21 @@ set(LIBUNWIND_SOURCES
     ${LIBUNWIND_ASM_SOURCES})
 
 # Generate library list.
-if (LIBUNWIND_USE_COMPILER_RT)
-  add_library_flags("${LIBUNWIND_BUILTINS_LIBRARY}")
+if (CXX_SUPPORTS_NOSTDLIBXX_FLAG)
+  add_link_flags_if_supported(-nostdlib++)
 else()
-  add_library_flags_if(LIBUNWIND_HAS_GCC_S_LIB gcc_s)
-  add_library_flags_if(LIBUNWIND_HAS_GCC_LIB gcc)
-endif()
-if (NOT APPLE) # On Apple platforms, we don't need to link explicitly against system libraries
+  if (LIBUNWIND_USE_COMPILER_RT)
+    add_library_flags("${LIBUNWIND_BUILTINS_LIBRARY}")
+  else()
+    add_library_flags_if(LIBUNWIND_HAS_GCC_S_LIB gcc_s)
+    add_library_flags_if(LIBUNWIND_HAS_GCC_LIB gcc)
+  endif()
   add_library_flags_if(LIBUNWIND_HAS_C_LIB c)
   add_library_flags_if(LIBUNWIND_HAS_DL_LIB dl)
+endif()
 
-  if (LIBUNWIND_ENABLE_THREADS)
+if (LIBUNWIND_ENABLE_THREADS AND NOT APPLE)
     add_library_flags_if(LIBUNWIND_HAS_PTHREAD_LIB pthread)
-    add_compile_flags_if(LIBUNWIND_WEAK_PTHREAD_LIB -DLIBUNWIND_USE_WEAK_PTHREAD=1)
-  endif()
 endif()
 
 if (LIBUNWIND_ENABLE_THREADS)

``````````

</details>


https://github.com/llvm/llvm-project/pull/75646