1include(CMakePushCheckState) 2include(CheckLibraryExists) 3include(CheckSymbolExists) 4include(LLVMCheckCompilerLinkerFlag) 5include(CheckCCompilerFlag) 6include(CheckCXXCompilerFlag) 7include(CheckCSourceCompiles) 8 9# The compiler driver may be implicitly trying to link against libunwind. 10# This is normally ok (libcxx relies on an unwinder), but if libunwind is 11# built in the same cmake invocation as libcxx and we've got 12# LIBCXXABI_USE_LLVM_UNWINDER set, we'd be linking against the just-built 13# libunwind (and the compiler implicit -lunwind wouldn't succeed as the newly 14# built libunwind isn't installed yet). For those cases, it'd be good to 15# link with --unwindlib=none. Check if that option works. 16llvm_check_compiler_linker_flag(C "--unwindlib=none" CXX_SUPPORTS_UNWINDLIB_EQ_NONE_FLAG) 17 18if (NOT LIBCXX_USE_COMPILER_RT) 19 if(WIN32 AND NOT MINGW) 20 set(LIBCXX_HAS_GCC_S_LIB NO) 21 else() 22 if(ANDROID) 23 check_library_exists(gcc __gcc_personality_v0 "" LIBCXX_HAS_GCC_LIB) 24 else() 25 check_library_exists(gcc_s __gcc_personality_v0 "" LIBCXX_HAS_GCC_S_LIB) 26 endif() 27 endif() 28endif() 29 30check_cxx_compiler_flag(-nostdlibinc CXX_SUPPORTS_NOSTDLIBINC_FLAG) 31check_cxx_compiler_flag(-nolibc CXX_SUPPORTS_NOLIBC_FLAG) 32 33# libc++ is using -nostdlib++ at the link step when available, 34# otherwise -nodefaultlibs is used. We want all our checks to also 35# use one of these options, otherwise we may end up with an inconsistency between 36# the flags we think we require during configuration (if the checks are 37# performed without one of those options) and the flags that are actually 38# required during compilation (which has the -nostdlib++ or -nodefaultlibs). libc is 39# required for the link to go through. We remove sanitizers from the 40# configuration checks to avoid spurious link errors. 41 42check_cxx_compiler_flag(-nostdlib++ CXX_SUPPORTS_NOSTDLIBXX_FLAG) 43if (CXX_SUPPORTS_NOSTDLIBXX_FLAG) 44 set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nostdlib++") 45else() 46 check_c_compiler_flag(-nodefaultlibs C_SUPPORTS_NODEFAULTLIBS_FLAG) 47 if (C_SUPPORTS_NODEFAULTLIBS_FLAG) 48 set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nodefaultlibs") 49 endif() 50endif() 51 52# Only link against compiler-rt manually if we use -nodefaultlibs, since 53# otherwise the compiler will do the right thing on its own. 54if (NOT CXX_SUPPORTS_NOSTDLIBXX_FLAG AND C_SUPPORTS_NODEFAULTLIBS_FLAG) 55 if (LIBCXX_USE_COMPILER_RT) 56 include(HandleCompilerRT) 57 find_compiler_rt_library(builtins LIBCXX_BUILTINS_LIBRARY 58 FLAGS ${LIBCXX_COMPILE_FLAGS}) 59 if (LIBCXX_BUILTINS_LIBRARY) 60 list(APPEND CMAKE_REQUIRED_LIBRARIES "${LIBCXX_BUILTINS_LIBRARY}") 61 else() 62 message(WARNING "Could not find builtins library from libc++") 63 endif() 64 elseif (LIBCXX_HAS_GCC_LIB) 65 list(APPEND CMAKE_REQUIRED_LIBRARIES gcc) 66 elseif (LIBCXX_HAS_GCC_S_LIB) 67 list(APPEND CMAKE_REQUIRED_LIBRARIES gcc_s) 68 endif () 69 if (MINGW) 70 # Mingw64 requires quite a few "C" runtime libraries in order for basic 71 # programs to link successfully with -nodefaultlibs. 72 if (LIBCXX_USE_COMPILER_RT) 73 set(MINGW_RUNTIME ${LIBCXX_BUILTINS_LIBRARY}) 74 else () 75 set(MINGW_RUNTIME gcc_s gcc) 76 endif() 77 set(MINGW_LIBRARIES mingw32 ${MINGW_RUNTIME} moldname mingwex msvcrt advapi32 78 shell32 user32 kernel32 mingw32 ${MINGW_RUNTIME} 79 moldname mingwex msvcrt) 80 list(APPEND CMAKE_REQUIRED_LIBRARIES ${MINGW_LIBRARIES}) 81 endif() 82endif() 83 84if (CXX_SUPPORTS_NOSTDLIBXX_FLAG OR C_SUPPORTS_NODEFAULTLIBS_FLAG) 85 if (CMAKE_C_FLAGS MATCHES -fsanitize OR CMAKE_CXX_FLAGS MATCHES -fsanitize) 86 set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fno-sanitize=all") 87 endif () 88 if (CMAKE_C_FLAGS MATCHES -fsanitize-coverage OR CMAKE_CXX_FLAGS MATCHES -fsanitize-coverage) 89 set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fsanitize-coverage=0") 90 endif () 91endif () 92 93# Check compiler pragmas 94if(CMAKE_CXX_COMPILER_ID MATCHES "Clang") 95 cmake_push_check_state() 96 set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -Werror=unknown-pragmas") 97 check_c_source_compiles(" 98#pragma comment(lib, \"c\") 99int main(void) { return 0; } 100" C_SUPPORTS_COMMENT_LIB_PRAGMA) 101 cmake_pop_check_state() 102endif() 103 104check_symbol_exists(__PICOLIBC__ "string.h" PICOLIBC) 105 106# Check libraries 107if(WIN32 AND NOT MINGW) 108 # TODO(compnerd) do we want to support an emulation layer that allows for the 109 # use of pthread-win32 or similar libraries to emulate pthreads on Windows? 110 set(LIBCXX_HAS_PTHREAD_LIB NO) 111 set(LIBCXX_HAS_RT_LIB NO) 112 set(LIBCXX_HAS_ATOMIC_LIB NO) 113elseif(APPLE) 114 set(LIBCXX_HAS_PTHREAD_LIB NO) 115 set(LIBCXX_HAS_RT_LIB NO) 116 set(LIBCXX_HAS_ATOMIC_LIB NO) 117elseif(FUCHSIA) 118 set(LIBCXX_HAS_PTHREAD_LIB NO) 119 set(LIBCXX_HAS_RT_LIB NO) 120 check_library_exists(atomic __atomic_fetch_add_8 "" LIBCXX_HAS_ATOMIC_LIB) 121elseif(ANDROID) 122 set(LIBCXX_HAS_PTHREAD_LIB NO) 123 set(LIBCXX_HAS_RT_LIB NO) 124 set(LIBCXX_HAS_ATOMIC_LIB NO) 125elseif(PICOLIBC) 126 set(LIBCXX_HAS_PTHREAD_LIB NO) 127 set(LIBCXX_HAS_RT_LIB NO) 128 set(LIBCXX_HAS_ATOMIC_LIB NO) 129else() 130 check_library_exists(pthread pthread_create "" LIBCXX_HAS_PTHREAD_LIB) 131 check_library_exists(rt clock_gettime "" LIBCXX_HAS_RT_LIB) 132 check_library_exists(atomic __atomic_fetch_add_8 "" LIBCXX_HAS_ATOMIC_LIB) 133endif() 134