diff --git a/CMakeLists.txt b/CMakeLists.txt index e91ecf613b..19ebc760d6 100644 --- a/CMakeLists.txt +++ b/CMakeLists.txt @@ -292,6 +292,8 @@ if(NOT OPTION_DEDICATED) endif() endif() +include(CheckAtomic) + if(APPLE) link_package(Iconv TARGET Iconv::Iconv) diff --git a/cmake/CheckAtomic.cmake b/cmake/CheckAtomic.cmake new file mode 100644 index 0000000000..52d93f4f5b --- /dev/null +++ b/cmake/CheckAtomic.cmake @@ -0,0 +1,87 @@ +# atomic builtins are required for threading support. + +INCLUDE(CheckCXXSourceCompiles) +INCLUDE(CheckLibraryExists) + +# Sometimes linking against libatomic is required for atomic ops, if +# the platform doesn't support lock-free atomics. + +function(check_working_cxx_atomics varname) + set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS}) + set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -std=c++17") + check_cxx_source_compiles(" +#include +std::atomic x; +std::atomic y; +std::atomic z; +int main() { + ++z; + ++y; + return ++x; +} +" ${varname}) + set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS}) +endfunction(check_working_cxx_atomics) + +function(check_working_cxx_atomics64 varname) + set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS}) + set(CMAKE_REQUIRED_FLAGS "-std=c++17 ${CMAKE_REQUIRED_FLAGS}") + check_cxx_source_compiles(" +#include +#include +std::atomic x (0); +int main() { + uint64_t i = x.load(std::memory_order_relaxed); + (void)i; + return 0; +} +" ${varname}) + set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS}) +endfunction(check_working_cxx_atomics64) + + +# Check for (non-64-bit) atomic operations. +if(MSVC) + set(HAVE_CXX_ATOMICS_WITHOUT_LIB True) +else() + # First check if atomics work without the library. + check_working_cxx_atomics(HAVE_CXX_ATOMICS_WITHOUT_LIB) + # If not, check if the library exists, and atomics work with it. + if(NOT HAVE_CXX_ATOMICS_WITHOUT_LIB) + check_library_exists(atomic __atomic_fetch_add_4 "" HAVE_LIBATOMIC) + if(HAVE_LIBATOMIC) + list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic") + check_working_cxx_atomics(HAVE_CXX_ATOMICS_WITH_LIB) + if (NOT HAVE_CXX_ATOMICS_WITH_LIB) + message(FATAL_ERROR "Host compiler must support std::atomic!") + endif() + else() + message(FATAL_ERROR "Host compiler appears to require libatomic, but cannot find it.") + endif() + endif() +endif() + +# Check for 64 bit atomic operations. +if(MSVC) + set(HAVE_CXX_ATOMICS64_WITHOUT_LIB True) +else() + # First check if atomics work without the library. + check_working_cxx_atomics64(HAVE_CXX_ATOMICS64_WITHOUT_LIB) + # If not, check if the library exists, and atomics work with it. + if(NOT HAVE_CXX_ATOMICS64_WITHOUT_LIB) + check_library_exists(atomic __atomic_load_8 "" HAVE_CXX_LIBATOMICS64) + if(HAVE_CXX_LIBATOMICS64) + list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic") + check_working_cxx_atomics64(HAVE_CXX_ATOMICS64_WITH_LIB) + if (NOT HAVE_CXX_ATOMICS64_WITH_LIB) + message(FATAL_ERROR "Host compiler must support 64-bit std::atomic!") + endif() + else() + message(FATAL_ERROR "Host compiler appears to require libatomic for 64-bit operations, but cannot find it.") + endif() + endif() +endif() + +if(HAVE_CXX_ATOMICS_WITH_LIB OR HAVE_CXX_ATOMICS64_WITH_LIB) + target_link_libraries(openttd atomic) +endif()