Check atomic

CMakeLists.txt

@@ -38,6 +38,7 @@ include(CheckLibraryExists)
 include(CMakePackageConfigHelpers)
 include(Dart)
 include(FindFilesystem)
+include(FindAtomic)
 include(GenerateExportHeader)
 
 set(CXX_EXTENSIONS OFF)
@@ -200,7 +201,7 @@ if(CIFPP_RECREATE_SYMOP_DATA)
 
 	add_executable(symop-map-generator "${CMAKE_SOURCE_DIR}/tools/symop-map-generator.cpp")
 
-	target_link_libraries(symop-map-generator Threads::Threads ${Boost_LIBRARIES} std::filesystem ${ZLIB_LIBRARIES})
+	target_link_libraries(symop-map-generator Threads::Threads ${Boost_LIBRARIES} std::filesystem std::atomic ${ZLIB_LIBRARIES})
 	if(Boost_INCLUDE_DIR)
 		target_include_directories(symop-map-generator PUBLIC ${Boost_INCLUDE_DIR})
 	endif()
@@ -271,7 +272,7 @@ target_include_directories(cifpp
 	${CMAKE_BINARY_DIR}
 )
 
-target_link_libraries(cifpp Threads::Threads ${Boost_LIBRARIES} std::filesystem ${ZLIB_LIBRARIES})
+target_link_libraries(cifpp Threads::Threads ${Boost_LIBRARIES} std::filesystem std::atomic ${ZLIB_LIBRARIES})
 
 if (CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang")
     target_link_options(cifpp PRIVATE -undefined dynamic_lookup)
@@ -428,7 +429,7 @@ if(CIFPP_BUILD_TESTS)
 			${CMAKE_CURRENT_BINARY_DIR}  # for config.h
 		)
 
-		target_link_libraries(${CIFPP_TEST} PRIVATE Threads::Threads cifpp ${Boost_LIBRARIES} std::filesystem ${ZLIB_LIBRARIES})
+		target_link_libraries(${CIFPP_TEST} PRIVATE Threads::Threads cifpp ${Boost_LIBRARIES} std::filesystem std::atomic ${ZLIB_LIBRARIES})
 
 		if(CIFPP_USE_RSRC)
 			mrc_target_resources(${CIFPP_TEST} ${CMAKE_SOURCE_DIR}/rsrc/mmcif_pdbx_v50.dic)

cmake/FindAtomic.cmake

+# Simplistic
+
+if(TARGET std::atomic)
+	return()
+endif()
+
+cmake_minimum_required(VERSION 3.10)
+
+include(CMakePushCheckState)
+include(CheckIncludeFileCXX)
+include(CheckCXXSourceCompiles)
+
+cmake_push_check_state()
+
+set(CMAKE_CXX_STANDARD 17)
+
+check_include_file_cxx("atomic" _CXX_ATOMIC_HAVE_HEADER)
+mark_as_advanced(_CXX_ATOMIC_HAVE_HEADER)
+
+set(code [[
+#include <atomic>
+int main(int argc, char** argv) {
+  struct Test { int val; };
+  std::atomic<Test> s;
+  return static_cast<int>(s.is_lock_free());
+}
+]])
+
+CHECK_CXX_SOURCE_COMPILES("${code}" _CXX_ATOMIC_BUILTIN)
+
+if(_CXX_ATOMIC_BUILTIN)
+	set(_found 1)
+else()
+  list(APPEND CMAKE_REQUIRED_LIBRARIES atomic)
+  list(APPEND FOLLY_LINK_LIBRARIES atomic)
+
+  CHECK_CXX_SOURCE_COMPILES("${code}" _CXX_ATOMIC_LIB_NEEDED)
+  if (NOT _CXX_ATOMIC_LIB_NEEDED)
+    message(FATAL_ERROR "unable to link C++ std::atomic code: you may need \
+      to install GNU libatomic")
+  else()
+	set(_found 1)
+  endif()
+endif()
+
+if(_found)
+	add_library(std::atomic INTERFACE IMPORTED)
+	set_property(TARGET std::atomic APPEND PROPERTY INTERFACE_COMPILE_FEATURES cxx_std_14)
+
+	if(_CXX_ATOMIC_BUILTIN)
+		# Nothing to add...
+	elseif(_CXX_ATOMIC_LIB_NEEDED)
+		set_target_properties(std::atomic PROPERTIES IMPORTED_LIBNAME atomic)
+	endif()
+endif()
+
+cmake_pop_check_state()
+
+set(Atomic_FOUND ${_found} CACHE BOOL "TRUE if we can run a program using std::atomic" FORCE)
+
+if(Atomic_FIND_REQUIRED AND NOT Atomic_FOUND)
+    message(FATAL_ERROR "Cannot run simple program using std::atomic")
+endif()