Add -fobjc-exceptions flag to ObjectiveC sources if supported (bug #2657)

modules/highgui/CMakeLists.txt

@@ -230,6 +230,24 @@ ocv_module_include_directories()
 
 ocv_create_module(${GRFMT_LIBS} ${HIGHGUI_LIBRARIES})
 
+if(APPLE)
+  ocv_check_flag_support(OBJCXX "-fobjc-exceptions" HAVE_OBJC_EXCEPTIONS)
+  if(HAVE_OBJC_EXCEPTIONS)
+    foreach(source ${OPENCV_MODULE_${the_module}_SOURCES})
+      if("${source}" MATCHES "\\.mm$")
+        get_source_file_property(flags "${source}" COMPILE_FLAGS)
+        if(flags)
+          set(flags "${_flags} -fobjc-exceptions")
+        else()
+          set(flags "-fobjc-exceptions")
+        endif()
+
+        set_source_files_properties("${source}" PROPERTIES COMPILE_FLAGS "${flags}")
+      endif()
+    endforeach()
+  endif()
+endif()
+
 if(BUILD_SHARED_LIBS)
   add_definitions(-DHIGHGUI_EXPORTS)
 endif()