| INCLUDE(CheckCXXSourceCompiles) |
| |
| # Sometimes linking against libatomic is required for atomic ops, if |
| # the platform doesn't support lock-free atomics. |
| # |
| # We could modify LLVM's CheckAtomic module and have it check for 64-bit |
| # atomics instead. However, we would like to avoid careless uses of 64-bit |
| # atomics inside LLVM over time on 32-bit platforms. |
| |
| function(check_cxx_atomics varname) |
| set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS}) |
| set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nodefaultlibs -std=c++11 -nostdinc++ -isystem ${LIBCXX_SOURCE_DIR}/include") |
| if (${LIBCXX_GCC_TOOLCHAIN}) |
| set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} --gcc-toolchain=${LIBCXX_GCC_TOOLCHAIN}") |
| endif() |
| 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} -fno-sanitize-coverage=edge,trace-cmp,indirect-calls,8bit-counters") |
| endif() |
| check_cxx_source_compiles(" |
| #include <cstdint> |
| #include <atomic> |
| std::atomic<uintptr_t> x; |
| std::atomic<uintmax_t> y; |
| int main(int, char**) { |
| return x + y; |
| } |
| " ${varname}) |
| set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS}) |
| endfunction(check_cxx_atomics) |
| |
| # Perform the check for 64bit atomics without libatomic. It may have been |
| # added to the required libraries during in the configuration of LLVM, which |
| # would cause the check for CXX atomics without libatomic to incorrectly pass. |
| set(OLD_CMAKE_REQUIRED_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES}) |
| list(REMOVE_ITEM CMAKE_REQUIRED_LIBRARIES "atomic") |
| check_cxx_atomics(LIBCXX_HAVE_CXX_ATOMICS_WITHOUT_LIB) |
| set(CMAKE_REQUIRED_LIBRARIES ${OLD_CMAKE_REQUIRED_LIBRARIES}) |
| |
| check_library_exists(atomic __atomic_fetch_add_8 "" LIBCXX_HAS_ATOMIC_LIB) |
| # If not, check if the library exists, and atomics work with it. |
| if(NOT LIBCXX_HAVE_CXX_ATOMICS_WITHOUT_LIB) |
| if(LIBCXX_HAS_ATOMIC_LIB) |
| list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic") |
| check_cxx_atomics(LIBCXX_HAVE_CXX_ATOMICS_WITH_LIB) |
| if (NOT LIBCXX_HAVE_CXX_ATOMICS_WITH_LIB) |
| message(WARNING "Host compiler must support std::atomic!") |
| endif() |
| else() |
| message(WARNING "Host compiler appears to require libatomic, but cannot find it.") |
| endif() |
| endif() |