Fix static linking on macOS

CMakeLists.txt

@@ -164,35 +164,7 @@ set(CMAKE_THREAD_PREFER_PTHREAD TRUE)
 set(THREADS_PREFER_PTHREAD_FLAG TRUE)
 find_package(Threads REQUIRED)
 
-# not supported on Solaris - system libraries are not available as archives
-# LTO is supported only for native builds
-if(STATIC_LINK_RUNTIME)
-  if (NOT SOLARIS)
-    if(NOT CMAKE_CROSSCOMPILING)
-      add_compile_options(-static -flto)
-    else()
-      add_compile_options(-static)
-    endif()
-
-    if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
-      link_libraries( -static -static-libstdc++ -pthread -flto )
-    elseif(NOT CMAKE_CROSSCOMPILING)
-      # this is messing with release builds
-      add_compile_options(-U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=0)
-      set(CMAKE_AR "gcc-ar")
-      set(CMAKE_C_ARCHIVE_CREATE "<CMAKE_AR> qcs <TARGET> <LINK_FLAGS> <OBJECTS>")
-      set(CMAKE_C_ARCHIVE_FINISH "true")
-      set(CMAKE_CXX_ARCHIVE_CREATE "<CMAKE_AR> qcs <TARGET> <LINK_FLAGS> <OBJECTS>")
-      set(CMAKE_CXX_ARCHIVE_FINISH "true")
-      link_libraries( -flto -static-libstdc++ -static-libgcc -static -Wl,--whole-archive -lpthread -Wl,--no-whole-archive )
-    else()
-      set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -static-libstdc++ -static-libgcc -static -Wl,--whole-archive -lpthread -Wl,--no-whole-archive" )
-      set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS}")
-    endif()
-  else()
-      link_libraries( -static-libstdc++ -static-libgcc )
- endif()
-endif(STATIC_LINK_RUNTIME)
+include(cmake/static_link.cmake)
 
 if(USE_NETNS)
   add_definitions(-DNETNS=1)

cmake/static_link.cmake

@@ -0,0 +1,40 @@
+if(NOT STATIC_LINK_RUNTIME)
+  return()
+endif()
+
+# not supported on Solaris - system libraries are not available as archives
+# LTO is supported only for native builds
+if(SOLARIS)
+  link_libraries( -static-libstdc++ -static-libgcc )
+  return()
+endif()
+
+if(NOT CMAKE_CROSSCOMPILING)
+  add_compile_options(-static -flto)
+else()
+  add_compile_options(-static)
+endif()
+
+if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+  if(APPLE)
+    link_libraries( -flto)
+  else()
+    link_libraries( -static -static-libstdc++ -pthread -flto )
+  endif()
+
+  return()
+endif()
+
+if(NOT CMAKE_CROSSCOMPILING)
+  # this is messing with release builds
+  add_compile_options(-U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=0)
+  set(CMAKE_AR "gcc-ar")
+  set(CMAKE_C_ARCHIVE_CREATE "<CMAKE_AR> qcs <TARGET> <LINK_FLAGS> <OBJECTS>")
+  set(CMAKE_C_ARCHIVE_FINISH "true")
+  set(CMAKE_CXX_ARCHIVE_CREATE "<CMAKE_AR> qcs <TARGET> <LINK_FLAGS> <OBJECTS>")
+  set(CMAKE_CXX_ARCHIVE_FINISH "true")
+  link_libraries( -flto -static-libstdc++ -static-libgcc -static -Wl,--whole-archive -lpthread -Wl,--no-whole-archive )
+else()
+  set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -static-libstdc++ -static-libgcc -static -Wl,--whole-archive -lpthread -Wl,--no-whole-archive" )
+  set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS}")
+endif()