[libunwind] a4336f2 - [runtimes] Don't link against compiler-rt explicitly when we use -nostdlib++ (#75089)
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cfe-commits at lists.llvm.org
Wed Dec 13 10:57:52 PST 2023
Author: Louis Dionne
Date: 2023-12-13T13:57:48-05:00
New Revision: a4336f2ec1747ea234a07d683930683f67fbd655
URL: https://github.com/llvm/llvm-project/commit/a4336f2ec1747ea234a07d683930683f67fbd655
DIFF: https://github.com/llvm/llvm-project/commit/a4336f2ec1747ea234a07d683930683f67fbd655.diff
LOG: [runtimes] Don't link against compiler-rt explicitly when we use -nostdlib++ (#75089)
When we use the -nostdlib++ flag, we don't need to explicitly link
against compiler-rt, since the compiler already links against it by
default. This simplifies the flags that we need to use when building
with Clang and GCC, and opens the door to further simplifications since
most platforms won't need to detect whether libgcc and libgcc_s are
supported anymore.
Furthermore, on platforms where -nostdlib++ is used, this patch prevents
manually linking compiler-rt *before* other system libraries. For
example, Apple platforms have several compiler-rt symbols defined in
libSystem.dylib. If we manually link against compiler-rt, we end up
overriding the default link order preferred by the compiler and
potentially using the symbols from the clang-provided libclang_rt.a
library instead of the system provided one.
Note that we don't touch how libunwind links against compiler-rt when it
builds the .so/.a because libunwind currently doesn't use -nodefaultlibs
and we want to avoid rocking the boat too much.
rdar://119506163
Added:
Modified:
libcxx/CMakeLists.txt
libcxx/cmake/config-ix.cmake
libcxxabi/cmake/config-ix.cmake
libcxxabi/src/CMakeLists.txt
libunwind/cmake/config-ix.cmake
Removed:
################################################################################
diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
index 5970322505dde2..75cb63222da35c 100644
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -677,15 +677,17 @@ function(cxx_link_system_libraries target)
target_add_link_flags_if_supported(${target} PRIVATE "--unwindlib=none")
endif()
- if (LIBCXX_USE_COMPILER_RT)
- find_compiler_rt_library(builtins LIBCXX_BUILTINS_LIBRARY)
- if (LIBCXX_BUILTINS_LIBRARY)
- target_link_libraries(${target} PRIVATE "${LIBCXX_BUILTINS_LIBRARY}")
+ if (MSVC)
+ if (LIBCXX_USE_COMPILER_RT)
+ find_compiler_rt_library(builtins LIBCXX_BUILTINS_LIBRARY)
+ if (LIBCXX_BUILTINS_LIBRARY)
+ target_link_libraries(${target} PRIVATE "${LIBCXX_BUILTINS_LIBRARY}")
+ endif()
+ elseif (LIBCXX_HAS_GCC_LIB)
+ target_link_libraries(${target} PRIVATE gcc)
+ elseif (LIBCXX_HAS_GCC_S_LIB)
+ target_link_libraries(${target} PRIVATE gcc_s)
endif()
- elseif (LIBCXX_HAS_GCC_LIB)
- target_link_libraries(${target} PRIVATE gcc)
- elseif (LIBCXX_HAS_GCC_S_LIB)
- target_link_libraries(${target} PRIVATE gcc_s)
endif()
if (LIBCXX_HAS_ATOMIC_LIB)
diff --git a/libcxx/cmake/config-ix.cmake b/libcxx/cmake/config-ix.cmake
index a365517936e756..1e8c2f5ce46321 100644
--- a/libcxx/cmake/config-ix.cmake
+++ b/libcxx/cmake/config-ix.cmake
@@ -45,7 +45,9 @@ else()
endif()
endif()
-if (CXX_SUPPORTS_NOSTDLIBXX_FLAG OR C_SUPPORTS_NODEFAULTLIBS_FLAG)
+# 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 (LIBCXX_USE_COMPILER_RT)
include(HandleCompilerRT)
find_compiler_rt_library(builtins LIBCXX_BUILTINS_LIBRARY
@@ -73,6 +75,9 @@ if (CXX_SUPPORTS_NOSTDLIBXX_FLAG OR C_SUPPORTS_NODEFAULTLIBS_FLAG)
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 ()
diff --git a/libcxxabi/cmake/config-ix.cmake b/libcxxabi/cmake/config-ix.cmake
index 39b9284b780ebc..10f2087c68c5e7 100644
--- a/libcxxabi/cmake/config-ix.cmake
+++ b/libcxxabi/cmake/config-ix.cmake
@@ -33,7 +33,9 @@ else()
endif()
endif()
-if (CXX_SUPPORTS_NOSTDLIBXX_FLAG OR C_SUPPORTS_NODEFAULTLIBS_FLAG)
+# 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 (LIBCXXABI_HAS_C_LIB)
list(APPEND CMAKE_REQUIRED_LIBRARIES c)
endif ()
@@ -67,6 +69,9 @@ if (CXX_SUPPORTS_NOSTDLIBXX_FLAG OR C_SUPPORTS_NODEFAULTLIBS_FLAG)
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 ()
diff --git a/libcxxabi/src/CMakeLists.txt b/libcxxabi/src/CMakeLists.txt
index 02031b69fd9156..4198827203fc8b 100644
--- a/libcxxabi/src/CMakeLists.txt
+++ b/libcxxabi/src/CMakeLists.txt
@@ -166,7 +166,10 @@ if (LIBCXXABI_USE_LLVM_UNWINDER)
target_link_libraries(cxxabi_shared_objects PUBLIC unwind_shared)
endif()
endif()
-target_link_libraries(cxxabi_shared_objects PRIVATE cxx-headers ${LIBCXXABI_BUILTINS_LIBRARY} ${LIBCXXABI_LIBRARIES})
+target_link_libraries(cxxabi_shared_objects PRIVATE cxx-headers ${LIBCXXABI_LIBRARIES})
+if (NOT CXX_SUPPORTS_NOSTDLIBXX_FLAG)
+ target_link_libraries(cxxabi_shared_objects PRIVATE ${LIBCXXABI_BUILTINS_LIBRARY})
+endif()
target_link_libraries(cxxabi_shared_objects PUBLIC cxxabi-headers)
set_target_properties(cxxabi_shared_objects
PROPERTIES
diff --git a/libunwind/cmake/config-ix.cmake b/libunwind/cmake/config-ix.cmake
index 7df8974b0a9254..126c872f0d4895 100644
--- a/libunwind/cmake/config-ix.cmake
+++ b/libunwind/cmake/config-ix.cmake
@@ -45,7 +45,9 @@ else()
endif()
endif()
-if (CXX_SUPPORTS_NOSTDLIBXX_FLAG OR C_SUPPORTS_NODEFAULTLIBS_FLAG)
+# 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 ()
@@ -78,6 +80,9 @@ if (CXX_SUPPORTS_NOSTDLIBXX_FLAG OR C_SUPPORTS_NODEFAULTLIBS_FLAG)
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 ()
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