[libunwind] Don't override LINKER_LANGUAGE #143533
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libunwind's GCC build fails because it tested `-nostdlib++` flag against C++ linker but then use C linker to perform final linking, while gcc doesn't support this flag but g++ does. The rationale for setting LINKER_LANGUAGE to C is to avoid pulling in C++ standard libraries. However this is already guaranteed by the combination of `-nostdlib++` and `empty CMAKE_CXX_IMPLICIT_LINK_LIBRARIES`, thus we can safely remove this override. However, in case `-nostdlib++` is unsupported, we need to use `-nodefaultlibs` and link against rtlib & libc manually.
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@llvm/pr-subscribers-libunwind Author: Jiaxun Yang (FlyGoat) Changeslibunwind's GCC build fails because it tested The rationale for setting LINKER_LANGUAGE to C is to avoid pulling in C++ standard libraries. However this is already guaranteed by the combination of However, in case Full diff: https://github.com/llvm/llvm-project/pull/143533.diff 1 Files Affected:
diff --git a/libunwind/src/CMakeLists.txt b/libunwind/src/CMakeLists.txt
index 70bd3a017cda7..e83d11363f7e4 100644
--- a/libunwind/src/CMakeLists.txt
+++ b/libunwind/src/CMakeLists.txt
@@ -74,6 +74,9 @@ set(LIBUNWIND_SOURCES
if (CXX_SUPPORTS_NOSTDLIBXX_FLAG)
add_link_flags_if_supported(-nostdlib++)
else()
+ if (C_SUPPORTS_NODEFAULTLIBS_FLAG)
+ add_link_flags_if_supported(-nodefaultlibs)
+ endif()
if (LIBUNWIND_USE_COMPILER_RT)
add_library_flags("${LIBUNWIND_BUILTINS_LIBRARY}")
else()
@@ -164,7 +167,6 @@ set_target_properties(unwind_shared
PROPERTIES
EXCLUDE_FROM_ALL "$<IF:$<BOOL:${LIBUNWIND_ENABLE_SHARED}>,FALSE,TRUE>"
LINK_FLAGS "${LIBUNWIND_LINK_FLAGS}"
- LINKER_LANGUAGE C
OUTPUT_NAME "${LIBUNWIND_SHARED_OUTPUT_NAME}"
VERSION "${LIBUNWIND_LIBRARY_VERSION}"
SOVERSION "1"
@@ -211,7 +213,6 @@ set_target_properties(unwind_static
PROPERTIES
EXCLUDE_FROM_ALL "$<IF:$<BOOL:${LIBUNWIND_ENABLE_STATIC}>,FALSE,TRUE>"
LINK_FLAGS "${LIBUNWIND_LINK_FLAGS}"
- LINKER_LANGUAGE C
OUTPUT_NAME "${LIBUNWIND_STATIC_OUTPUT_NAME}"
)
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FlyGoat
changed the title
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@MaskRay Do you mind to help me merge once I get necessary approval? I’m not a commiter yet. |
Please rebase :) |
There was a problem hiding this comment.
I don't think this is required, or even works after #143162.
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@philnik777 Sorry I wasn’t aware of that. However #143162 breaks my use case of bootstrapping libunwind with compiler-rt builtins from same runtime build. I’ll try to come up with a more comprehensive solution. |
libunwind's GCC build fails because it tested
-nostdlib++flag against C++ linker but then use C linker to perform final linking, while gcc doesn't support this flag but g++ does.The rationale for setting LINKER_LANGUAGE to C is to avoid pulling in C++ standard libraries. However this is already guaranteed by the combination of
-nostdlib++andempty CMAKE_CXX_IMPLICIT_LINK_LIBRARIES, thus we can safely remove this override.However, in case
-nostdlib++is unsupported, we need to use-nodefaultlibsand link against rtlib & libc manually.Closes #98440