cmake: add RE_LIBS config and add atomic check

CMakeLists.txt

@@ -607,50 +607,6 @@ if(USE_REM)
 endif()
 
 
-##############################################################################
-#
-# Linking LIBS
-#
-
-set(LINKLIBS Threads::Threads ${RESOLV_LIBRARY})
-
-if(BACKTRACE_FOUND)
-  list(APPEND LINKLIBS ${Backtrace_LIBRARIES})
-endif()
-
-if(ZLIB_FOUND)
-  list(APPEND LINKLIBS ZLIB::ZLIB)
-endif()
-
-if(USE_OPENSSL)
-  list(APPEND LINKLIBS OpenSSL::SSL OpenSSL::Crypto)
-endif()
-
-if(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
-  list(APPEND LINKLIBS
-    "-framework SystemConfiguration" "-framework CoreFoundation"
-  )
-endif()
-
-if(WIN32)
-  list(APPEND LINKLIBS
-    qwave
-    iphlpapi
-    wsock32
-    ws2_32
-    dbghelp
-  )
-else()
-  list(APPEND LINKLIBS m)
-endif()
-
-if(UNIX)
-  list(APPEND LINKLIBS
-    ${CMAKE_DL_LIBS}
-  )
-endif()
-
-
 ##############################################################################
 #
 # Main target object
@@ -675,7 +631,7 @@ target_include_directories(re-objs PRIVATE
 if(LIBRE_BUILD_SHARED)
   list(APPEND RE_INSTALL_TARGETS re-shared)
   add_library(re-shared SHARED $<TARGET_OBJECTS:re-objs>)
-  target_link_libraries(re-shared PRIVATE ${LINKLIBS})
+  target_link_libraries(re-shared PRIVATE ${RE_LIBS})
   set_target_properties(re-shared PROPERTIES VERSION
     ${PROJECT_SOVERSION}.${PROJECT_VERSION_MINOR}.${PROJECT_VERSION_PATCH})
   set_target_properties(re-shared PROPERTIES SOVERSION ${PROJECT_SOVERSION})
@@ -692,7 +648,7 @@ endif()
 if(LIBRE_BUILD_STATIC)
   list(APPEND RE_INSTALL_TARGETS re)
   add_library(re STATIC $<TARGET_OBJECTS:re-objs>)
-  target_link_libraries(re PUBLIC ${LINKLIBS})
+  target_link_libraries(re PUBLIC ${RE_LIBS})
   target_include_directories(re PUBLIC
     $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
   )

cmake/re-config.cmake

@@ -2,6 +2,7 @@ include(CheckIncludeFile)
 include(CheckFunctionExists)
 include(CheckSymbolExists)
 include(CheckTypeSize)
+include(CheckCSourceCompiles)
 
 option(USE_MBEDTLS "Enable MbedTLS" OFF)
 
@@ -214,3 +215,75 @@ if(NOT ${CMAKE_BUILD_TYPE} MATCHES "[Rr]el")
     set(CMAKE_ENABLE_EXPORTS ON)
   endif()
 endif()
+
+
+##############################################################################
+#
+# Linking LIBS
+#
+
+set(RE_LIBS Threads::Threads ${RESOLV_LIBRARY})
+
+if(BACKTRACE_FOUND)
+  list(APPEND RE_LIBS ${Backtrace_LIBRARIES})
+endif()
+
+if(ZLIB_FOUND)
+  list(APPEND RE_LIBS ZLIB::ZLIB)
+endif()
+
+if(USE_OPENSSL)
+  list(APPEND RE_LIBS OpenSSL::SSL OpenSSL::Crypto)
+endif()
+
+if(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
+  list(APPEND RE_LIBS
+    "-framework SystemConfiguration" "-framework CoreFoundation"
+  )
+endif()
+
+if(WIN32)
+  list(APPEND RE_LIBS
+    qwave
+    iphlpapi
+    wsock32
+    ws2_32
+    dbghelp
+  )
+else()
+  list(APPEND RE_LIBS m)
+endif()
+
+if(UNIX)
+  list(APPEND RE_LIBS
+    ${CMAKE_DL_LIBS}
+  )
+endif()
+
+
+##############################################################################
+#
+# Testing Atomic
+#
+
+set(ATOMIC_TEST_CODE "
+    #include <stdatomic.h>
+    #include <stdint.h>
+    int main() {
+        atomic_int_least64_t x;
+        atomic_store(&x, 1);
+        x--;
+        return atomic_load(&x);
+    }")
+
+check_c_source_compiles("${ATOMIC_TEST_CODE}" atomic_test)
+
+if(NOT atomic_test)
+  set(CMAKE_REQUIRED_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES} atomic)
+  check_c_source_compiles("${ATOMIC_TEST_CODE}" atomic_test_lib)
+  if(NOT atomic_test_lib)
+    message(FATAL_ERROR "No builtin or libatomic support")
+  else()
+    list(APPEND RE_LIBS atomic)
+  endif()
+endif()