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