[libcxx] [libcxxabi] [libunwind] [llvm] [runtimes] Probe for -nostdlib++ and -nostdinc++ with the C compiler (PR #108357)
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Thu Sep 12 03:16:22 PDT 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-libcxxabi
Author: Martin Storsjö (mstorsjo)
<details>
<summary>Changes</summary>
While these flags semantically are relevant only for C++, we do add them to CMAKE_REQUIRED_FLAGS if they are detected. All flags in that variable are used both when testing compilation of C and C++ (and for detecting libraries, which uses the C compiler driver).
Therefore, to be sure we safely can add the flags to CMAKE_REQUIRED_FLAGS, test for the option with the C language.
This should fix compilation with GCC; newer versions of GCC do support the -nostdlib++ option, but it's only supported by the C++ compiler driver, not the C driver. (However, many builds of GCC also do accept the option with the C driver, if GCC was compiled with Ada support enabled, see [1]. That's why this issue isn't noticed in all configurations with GCC.)
Clang does support these options in both C and C++ driver modes.
This should fix #<!-- -->90332.
[1] https://github.com/llvm/llvm-project/issues/90332#issuecomment-2325099254
---
Full diff: https://github.com/llvm/llvm-project/pull/108357.diff
6 Files Affected:
- (modified) libcxx/cmake/config-ix.cmake (+8-4)
- (modified) libcxxabi/cmake/config-ix.cmake (+8-4)
- (modified) libcxxabi/src/CMakeLists.txt (+2-2)
- (modified) libunwind/cmake/config-ix.cmake (+8-4)
- (modified) libunwind/src/CMakeLists.txt (+1-1)
- (modified) runtimes/CMakeLists.txt (+8-4)
``````````diff
diff --git a/libcxx/cmake/config-ix.cmake b/libcxx/cmake/config-ix.cmake
index 270d80575adcfd..192bad7a7a7fc6 100644
--- a/libcxx/cmake/config-ix.cmake
+++ b/libcxx/cmake/config-ix.cmake
@@ -38,9 +38,13 @@ check_cxx_compiler_flag(-nolibc CXX_SUPPORTS_NOLIBC_FLAG)
# 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.
+#
+# Adding flags to CMAKE_REQUIRED_FLAGS will include the flags both when testing
+# compilation of C and C++. Therefore test to make sure that the flags are
+# supported by the C compiler driver, before deciding to include them.
-check_cxx_compiler_flag(-nostdlib++ CXX_SUPPORTS_NOSTDLIBXX_FLAG)
-if (CXX_SUPPORTS_NOSTDLIBXX_FLAG)
+check_c_compiler_flag(-nostdlib++ C_SUPPORTS_NOSTDLIBXX_FLAG)
+if (C_SUPPORTS_NOSTDLIBXX_FLAG)
set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nostdlib++")
else()
check_c_compiler_flag(-nodefaultlibs C_SUPPORTS_NODEFAULTLIBS_FLAG)
@@ -51,7 +55,7 @@ endif()
# Only link against compiler-rt manually if we use -nodefaultlibs, since
# otherwise the compiler will do the right thing on its own.
-if (NOT CXX_SUPPORTS_NOSTDLIBXX_FLAG AND C_SUPPORTS_NODEFAULTLIBS_FLAG)
+if (NOT C_SUPPORTS_NOSTDLIBXX_FLAG AND C_SUPPORTS_NODEFAULTLIBS_FLAG)
if (LIBCXX_USE_COMPILER_RT)
include(HandleCompilerRT)
find_compiler_rt_library(builtins LIBCXX_BUILTINS_LIBRARY
@@ -81,7 +85,7 @@ if (NOT CXX_SUPPORTS_NOSTDLIBXX_FLAG AND C_SUPPORTS_NODEFAULTLIBS_FLAG)
endif()
endif()
-if (CXX_SUPPORTS_NOSTDLIBXX_FLAG OR C_SUPPORTS_NODEFAULTLIBS_FLAG)
+if (C_SUPPORTS_NOSTDLIBXX_FLAG OR C_SUPPORTS_NODEFAULTLIBS_FLAG)
if (CMAKE_C_FLAGS MATCHES -fsanitize OR CMAKE_CXX_FLAGS MATCHES -fsanitize)
set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fno-sanitize=all")
endif ()
diff --git a/libcxxabi/cmake/config-ix.cmake b/libcxxabi/cmake/config-ix.cmake
index 10f2087c68c5e7..ab74ad79a654af 100644
--- a/libcxxabi/cmake/config-ix.cmake
+++ b/libcxxabi/cmake/config-ix.cmake
@@ -22,9 +22,13 @@ endif ()
# required during compilation (which has the -nodefaultlibs). libc is
# required for the link to go through. We remove sanitizers from the
# configuration checks to avoid spurious link errors.
+#
+# Adding flags to CMAKE_REQUIRED_FLAGS will include the flags both when testing
+# compilation of C and C++. Therefore test to make sure that the flags are
+# supported by the C compiler driver, before deciding to include them.
-check_cxx_compiler_flag(-nostdlib++ CXX_SUPPORTS_NOSTDLIBXX_FLAG)
-if (CXX_SUPPORTS_NOSTDLIBXX_FLAG)
+check_c_compiler_flag(-nostdlib++ C_SUPPORTS_NOSTDLIBXX_FLAG)
+if (C_SUPPORTS_NOSTDLIBXX_FLAG)
set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nostdlib++")
else()
check_c_compiler_flag(-nodefaultlibs C_SUPPORTS_NODEFAULTLIBS_FLAG)
@@ -35,7 +39,7 @@ endif()
# Only link against compiler-rt manually if we use -nodefaultlibs, since
# otherwise the compiler will do the right thing on its own.
-if (NOT CXX_SUPPORTS_NOSTDLIBXX_FLAG AND C_SUPPORTS_NODEFAULTLIBS_FLAG)
+if (NOT C_SUPPORTS_NOSTDLIBXX_FLAG AND C_SUPPORTS_NODEFAULTLIBS_FLAG)
if (LIBCXXABI_HAS_C_LIB)
list(APPEND CMAKE_REQUIRED_LIBRARIES c)
endif ()
@@ -71,7 +75,7 @@ if (NOT CXX_SUPPORTS_NOSTDLIBXX_FLAG AND C_SUPPORTS_NODEFAULTLIBS_FLAG)
endif()
endif()
-if (CXX_SUPPORTS_NOSTDLIBXX_FLAG OR C_SUPPORTS_NODEFAULTLIBS_FLAG)
+if (C_SUPPORTS_NOSTDLIBXX_FLAG OR C_SUPPORTS_NODEFAULTLIBS_FLAG)
if (CMAKE_C_FLAGS MATCHES -fsanitize OR CMAKE_CXX_FLAGS MATCHES -fsanitize)
set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fno-sanitize=all")
endif ()
diff --git a/libcxxabi/src/CMakeLists.txt b/libcxxabi/src/CMakeLists.txt
index c1a7bcb14eb199..485349bdb735e6 100644
--- a/libcxxabi/src/CMakeLists.txt
+++ b/libcxxabi/src/CMakeLists.txt
@@ -91,7 +91,7 @@ if (ANDROID AND ANDROID_PLATFORM_LEVEL LESS 21)
endif()
# Setup flags.
-if (CXX_SUPPORTS_NOSTDLIBXX_FLAG)
+if (C_SUPPORTS_NOSTDLIBXX_FLAG)
add_link_flags_if_supported(-nostdlib++)
else()
add_link_flags_if_supported(-nodefaultlibs)
@@ -167,7 +167,7 @@ if (LIBCXXABI_USE_LLVM_UNWINDER)
endif()
endif()
target_link_libraries(cxxabi_shared_objects PRIVATE cxx-headers ${LIBCXXABI_LIBRARIES})
-if (NOT CXX_SUPPORTS_NOSTDLIBXX_FLAG)
+if (NOT C_SUPPORTS_NOSTDLIBXX_FLAG)
target_link_libraries(cxxabi_shared_objects PRIVATE ${LIBCXXABI_BUILTINS_LIBRARY})
endif()
target_link_libraries(cxxabi_shared_objects PUBLIC cxxabi-headers)
diff --git a/libunwind/cmake/config-ix.cmake b/libunwind/cmake/config-ix.cmake
index 126c872f0d4895..88a13b4ec0e41c 100644
--- a/libunwind/cmake/config-ix.cmake
+++ b/libunwind/cmake/config-ix.cmake
@@ -34,9 +34,13 @@ endif()
# required during compilation (which has the -nostdlib++ or -nodefaultlibs). libc is
# required for the link to go through. We remove sanitizers from the
# configuration checks to avoid spurious link errors.
+#
+# Adding flags to CMAKE_REQUIRED_FLAGS will include the flags both when testing
+# compilation of C and C++. Therefore test to make sure that the flags are
+# supported by the C compiler driver, before deciding to include them.
-llvm_check_compiler_linker_flag(CXX "-nostdlib++" CXX_SUPPORTS_NOSTDLIBXX_FLAG)
-if (CXX_SUPPORTS_NOSTDLIBXX_FLAG)
+llvm_check_compiler_linker_flag(C "-nostdlib++" C_SUPPORTS_NOSTDLIBXX_FLAG)
+if (C_SUPPORTS_NOSTDLIBXX_FLAG)
set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nostdlib++")
else()
llvm_check_compiler_linker_flag(C "-nodefaultlibs" C_SUPPORTS_NODEFAULTLIBS_FLAG)
@@ -47,7 +51,7 @@ 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 (NOT C_SUPPORTS_NOSTDLIBXX_FLAG AND C_SUPPORTS_NODEFAULTLIBS_FLAG)
if (LIBUNWIND_HAS_C_LIB)
list(APPEND CMAKE_REQUIRED_LIBRARIES c)
endif ()
@@ -82,7 +86,7 @@ if (NOT CXX_SUPPORTS_NOSTDLIBXX_FLAG AND C_SUPPORTS_NODEFAULTLIBS_FLAG)
endif()
endif()
-if (CXX_SUPPORTS_NOSTDLIBXX_FLAG OR C_SUPPORTS_NODEFAULTLIBS_FLAG)
+if (C_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/libunwind/src/CMakeLists.txt b/libunwind/src/CMakeLists.txt
index 780430ba70ba60..09d23e967493d3 100644
--- a/libunwind/src/CMakeLists.txt
+++ b/libunwind/src/CMakeLists.txt
@@ -66,7 +66,7 @@ set(LIBUNWIND_SOURCES
${LIBUNWIND_ASM_SOURCES})
# Generate library list.
-if (CXX_SUPPORTS_NOSTDLIBXX_FLAG)
+if (C_SUPPORTS_NOSTDLIBXX_FLAG)
add_link_flags_if_supported(-nostdlib++)
else()
if (LIBUNWIND_USE_COMPILER_RT)
diff --git a/runtimes/CMakeLists.txt b/runtimes/CMakeLists.txt
index 830165c799c2ab..8db2b3fb9309b1 100644
--- a/runtimes/CMakeLists.txt
+++ b/runtimes/CMakeLists.txt
@@ -143,12 +143,16 @@ endif()
# Check for -nostdlib++ first; if there's no C++ standard library yet,
# all check_cxx_compiler_flag commands will fail until we add -nostdlib++
# (or -nodefaultlibs).
-llvm_check_compiler_linker_flag(CXX "-nostdlib++" CXX_SUPPORTS_NOSTDLIBXX_FLAG)
-if (CXX_SUPPORTS_NOSTDLIBXX_FLAG)
+#
+# Adding flags to CMAKE_REQUIRED_FLAGS will include the flags both when testing
+# compilation of C and C++. Therefore test to make sure that the flags are
+# supported by the C compiler driver, before deciding to include them.
+llvm_check_compiler_linker_flag(C "-nostdlib++" C_SUPPORTS_NOSTDLIBXX_FLAG)
+if (C_SUPPORTS_NOSTDLIBXX_FLAG)
set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nostdlib++")
endif()
-check_cxx_compiler_flag(-nostdinc++ CXX_SUPPORTS_NOSTDINCXX_FLAG)
-if (CXX_SUPPORTS_NOSTDINCXX_FLAG)
+check_c_compiler_flag(-nostdinc++ C_SUPPORTS_NOSTDINCXX_FLAG)
+if (C_SUPPORTS_NOSTDINCXX_FLAG)
set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nostdinc++")
endif()
``````````
</details>
https://github.com/llvm/llvm-project/pull/108357
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