https://github.com/philnik777 created
https://github.com/llvm/llvm-project/pull/143162
libunwind uses a C linker, so it's never even trying to link against any C++
libraries. This removes the code which tries to drop C++ libraries, which makes
the CMake configuration simpler and allows for upgrading GCC.
>From 653f4e85efdc7f413e18cf66c018773c53be07cd Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklau...@berlin.de>
Date: Fri, 6 Jun 2025 17:31:23 +0200
Subject: [PATCH] [libunwind] Remove checks for -nostdlib++
---
libunwind/cmake/config-ix.cmake | 65 ---------------------------------
libunwind/src/CMakeLists.txt | 12 ------
2 files changed, 77 deletions(-)
diff --git a/libunwind/cmake/config-ix.cmake b/libunwind/cmake/config-ix.cmake
index 126c872f0d489..47967a7d36c57 100644
--- a/libunwind/cmake/config-ix.cmake
+++ b/libunwind/cmake/config-ix.cmake
@@ -26,71 +26,6 @@ if (NOT LIBUNWIND_USE_COMPILER_RT)
endif ()
endif()
-# libunwind is using -nostdlib++ at the link step when available,
-# otherwise -nodefaultlibs is used. We want all our checks to also
-# use one of these options, otherwise we may end up with an inconsistency
between
-# the flags we think we require during configuration (if the checks are
-# performed without one of those options) and the flags that are actually
-# required during compilation (which has the -nostdlib++ or -nodefaultlibs).
libc is
-# required for the link to go through. We remove sanitizers from the
-# configuration checks to avoid spurious link errors.
-
-llvm_check_compiler_linker_flag(CXX "-nostdlib++" CXX_SUPPORTS_NOSTDLIBXX_FLAG)
-if (CXX_SUPPORTS_NOSTDLIBXX_FLAG)
- set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nostdlib++")
-else()
- llvm_check_compiler_linker_flag(C "-nodefaultlibs"
C_SUPPORTS_NODEFAULTLIBS_FLAG)
- if (C_SUPPORTS_NODEFAULTLIBS_FLAG)
- set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nodefaultlibs")
- endif()
-endif()
-
-# Only link against compiler-rt manually if we use -nodefaultlibs, since
-# otherwise the compiler will do the right thing on its own.
-if (NOT CXX_SUPPORTS_NOSTDLIBXX_FLAG AND C_SUPPORTS_NODEFAULTLIBS_FLAG)
- if (LIBUNWIND_HAS_C_LIB)
- list(APPEND CMAKE_REQUIRED_LIBRARIES c)
- endif ()
- if (LIBUNWIND_HAS_ROOT_LIB)
- list(APPEND CMAKE_REQUIRED_LIBRARIES root)
- endif ()
- if (LIBUNWIND_USE_COMPILER_RT)
- include(HandleCompilerRT)
- find_compiler_rt_library(builtins LIBUNWIND_BUILTINS_LIBRARY
- FLAGS ${LIBUNWIND_COMPILE_FLAGS})
- list(APPEND CMAKE_REQUIRED_LIBRARIES "${LIBUNWIND_BUILTINS_LIBRARY}")
- else ()
- if (LIBUNWIND_HAS_GCC_S_LIB)
- list(APPEND CMAKE_REQUIRED_LIBRARIES gcc_s)
- endif ()
- if (LIBUNWIND_HAS_GCC_LIB)
- list(APPEND CMAKE_REQUIRED_LIBRARIES gcc)
- endif ()
- endif ()
- if (MINGW)
- # Mingw64 requires quite a few "C" runtime libraries in order for basic
- # programs to link successfully with -nodefaultlibs.
- if (LIBUNWIND_USE_COMPILER_RT)
- set(MINGW_RUNTIME ${LIBUNWIND_BUILTINS_LIBRARY})
- else ()
- set(MINGW_RUNTIME gcc_s gcc)
- endif()
- set(MINGW_LIBRARIES mingw32 ${MINGW_RUNTIME} moldname mingwex msvcrt
advapi32
- shell32 user32 kernel32 mingw32 ${MINGW_RUNTIME}
- moldname mingwex msvcrt)
- list(APPEND CMAKE_REQUIRED_LIBRARIES ${MINGW_LIBRARIES})
- endif()
-endif()
-
-if (CXX_SUPPORTS_NOSTDLIBXX_FLAG OR C_SUPPORTS_NODEFAULTLIBS_FLAG)
- if (CMAKE_C_FLAGS MATCHES -fsanitize OR CMAKE_CXX_FLAGS MATCHES -fsanitize)
- set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fno-sanitize=all")
- endif ()
- if (CMAKE_C_FLAGS MATCHES -fsanitize-coverage OR CMAKE_CXX_FLAGS MATCHES
-fsanitize-coverage)
- set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fsanitize-coverage=0")
- endif ()
-endif ()
-
# Check compiler pragmas
if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
cmake_push_check_state()
diff --git a/libunwind/src/CMakeLists.txt b/libunwind/src/CMakeLists.txt
index 70bd3a017cda7..03818b1bb2512 100644
--- a/libunwind/src/CMakeLists.txt
+++ b/libunwind/src/CMakeLists.txt
@@ -71,18 +71,6 @@ set(LIBUNWIND_SOURCES
${LIBUNWIND_ASM_SOURCES})
# Generate library list.
-if (CXX_SUPPORTS_NOSTDLIBXX_FLAG)
- add_link_flags_if_supported(-nostdlib++)
-else()
- if (LIBUNWIND_USE_COMPILER_RT)
- add_library_flags("${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)
-endif()
-
if (NOT APPLE)
add_library_flags_if(LIBUNWIND_HAS_DL_LIB dl)
endif()
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