使用cmake构建库时，Objective-C++文件未链接到Cocoa

我的API中有一个文件是目标c++。该库构建良好，但当我编译使用该库的应用程序时，我的所有objective-c调用都会出现链接器错误：

Undefined symbols:
  "_objc_msgSend", referenced from:
      agui::OSXClipboard::copy(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)in libAgui.a(OSXClipboard.mm.o)
      agui::OSXClipboard::copy(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)in libAgui.a(OSXClipboard.mm.o)
      agui::OSXClipboard::copy(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)in libAgui.a(OSXClipboard.mm.o)
      agui::OSXClipboard::copy(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)in libAgui.a(OSXClipboard.mm.o)
      agui::OSXClipboard::copy(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)in libAgui.a(OSXClipboard.mm.o)
      agui::OSXClipboard::copy(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)in libAgui.a(OSXClipboard.mm.o)
      agui::OSXClipboard::paste()     in libAgui.a(OSXClipboard.mm.o)
      agui::OSXClipboard::paste()     in libAgui.a(OSXClipboard.mm.o)
      agui::OSXClipboard::paste()     in libAgui.a(OSXClipboard.mm.o)
      agui::OSXClipboard::paste()     in libAgui.a(OSXClipboard.mm.o)
     (maybe you meant: l_objc_msgSend_fixup_release, l_objc_msgSend_fixup_alloc )
  "_NSPasteboardTypeString", referenced from:
      agui::OSXClipboard::paste()     in libAgui.a(OSXClipboard.mm.o)
  "_OBJC_CLASS_$_NSArray", referenced from:
      objc-class-ref-to-NSArray in libAgui.a(OSXClipboard.mm.o)
  "_OBJC_CLASS_$_NSString", referenced from:
      objc-class-ref-to-NSString in libAgui.a(OSXClipboard.mm.o)
  "_objc_msgSend_fixup", referenced from:
      l_objc_msgSend_fixup_alloc in libAgui.a(OSXClipboard.mm.o)
      l_objc_msgSend_fixup_release in libAgui.a(OSXClipboard.mm.o)
     (maybe you meant: l_objc_msgSend_fixup_release, l_objc_msgSend_fixup_alloc )
  "_OBJC_CLASS_$_NSAutoreleasePool", referenced from:
      objc-class-ref-to-NSAutoreleasePool in libAgui.a(OSXClipboard.mm.o)
  "_NSStringPboardType", referenced from:
      agui::OSXClipboard::copy(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)in libAgui.a(OSXClipboard.mm.o)
      agui::OSXClipboard::copy(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)in libAgui.a(OSXClipboard.mm.o)
  "_OBJC_CLASS_$_NSPasteboard", referenced from:
      objc-class-ref-to-NSPasteboard in libAgui.a(OSXClipboard.mm.o)
ld: symbol(s) not found

我的目标是不必每次使用gui lib构建应用程序时都链接到可可。

这是cmake文件：

cmake_minimum_required(VERSION 2.6)
project(agui)
OPTION(WANT_SHARED "Build agui and the backend as a shared library" OFF) 
OPTION(WANT_ALLEGRO5_BACKEND "Build the Allegro 5 backend" ON) 
if(APPLE AND NOT IPHONE)
    set(MACOSX 1)
endif(APPLE AND NOT IPHONE)
if(MACOSX)
ADD_DEFINITIONS("-x objective-c++")
endif(MACOSX)
if(MACOSX)
find_library(COCOA_LIBRARY Cocoa)
endif(MACOSX)
set(CLIPBOARD_SOURCE)
if(WIN32)
set(CLIPBOARD_SOURCE src/Agui/Clipboard/WinClipboard.cpp)
endif(WIN32)
if(MACOSX)
set(CLIPBOARD_SOURCE src/Agui/Clipboard/OSXClipboard.mm)
endif(MACOSX)

set(AGUI_SOURCES
    ${CLIPBOARD_SOURCE}
    src/Agui/Clipboard/Clipboard.cpp
    src/Agui/ActionEvent.cpp
    src/Agui/ActionListener.cpp
    src/Agui/BaseTypes.cpp
    src/Agui/BlinkingEvent.cpp
    src/Agui/BorderLayout.cpp
    src/Agui/Color.cpp
    src/Agui/Dimension.cpp
    src/Agui/EmptyWidget.cpp
    src/Agui/EventArgs.cpp
    src/Agui/FlowLayout.cpp
    src/Agui/FocusListener.cpp
    src/Agui/FocusManager.cpp
    src/Agui/Font.cpp
    src/Agui/FontLoader.cpp
    src/Agui/Graphics.cpp
    src/Agui/GridLayout.cpp
    src/Agui/Gui.cpp
    src/Agui/Image.cpp
    src/Agui/ImageLoader.cpp
    src/Agui/Input.cpp
    src/Agui/KeyboardListener.cpp
    src/Agui/Layout.cpp
    src/Agui/MouseListener.cpp
    src/Agui/Point.cpp
    src/Agui/Rectangle.cpp
    src/Agui/ResizableText.cpp
    src/Agui/ResizableBorderLayout.cpp
    src/Agui/SelectionListener.cpp
    src/Agui/TopContainer.cpp
    src/Agui/Widget.cpp
    src/Agui/WidgetListener.cpp
    src/Agui/Widgets/Button/Button.cpp
    src/Agui/Widgets/Button/ButtonListener.cpp
    src/Agui/Widgets/CheckBox/CheckBox.cpp
    src/Agui/Widgets/CheckBox/CheckBoxListener.cpp
    src/Agui/Widgets/DropDown/DropDown.cpp
    src/Agui/Widgets/DropDown/DropDownListener.cpp
    src/Agui/Widgets/Frame/Frame.cpp
    src/Agui/Widgets/Frame/FrameListener.cpp
    src/Agui/Widgets/Label/Label.cpp
    src/Agui/Widgets/Label/LabelListener.cpp
    src/Agui/Widgets/ListBox/ListBox.cpp
    src/Agui/Widgets/ListBox/ListBoxListener.cpp
    src/Agui/Widgets/RadioButton/RadioButton.cpp
    src/Agui/Widgets/RadioButton/RadioButtonListener.cpp
    src/Agui/Widgets/RadioButton/RadioButtonGroup.cpp
    src/Agui/Widgets/ScrollBar/HScrollBar.cpp
    src/Agui/Widgets/ScrollBar/HScrollBarListener.cpp
    src/Agui/Widgets/ScrollBar/VScrollBar.cpp
    src/Agui/Widgets/ScrollBar/VScrollBarListener.cpp
    src/Agui/Widgets/ScrollPane/ScrollPane.cpp
    src/Agui/Widgets/Slider/Slider.cpp
    src/Agui/Widgets/Slider/SliderListener.cpp
    src/Agui/Widgets/Tab/Tab.cpp
    src/Agui/Widgets/Tab/TabbedPane.cpp
    src/Agui/Widgets/Tab/TabbedPaneListener.cpp
    src/Agui/Widgets/TextBox/TextBox.cpp
    src/Agui/Widgets/TextBox/TextBoxListener.cpp
    src/Agui/Widgets/TextBox/ExtendedTextBox.cpp
    src/Agui/Widgets/TextField/TextField.cpp
    src/Agui/Widgets/TextField/TextFieldListener.cpp
    )
set(ALLEGRO5_BACKEND_SOURCES
    src/Agui/Backends/Allegro5/Allegro5Font.cpp
    src/Agui/Backends/Allegro5/Allegro5FontLoader.cpp
    src/Agui/Backends/Allegro5/Allegro5Graphics.cpp
    src/Agui/Backends/Allegro5/Allegro5Image.cpp
    src/Agui/Backends/Allegro5/Allegro5ImageLoader.cpp
    src/Agui/Backends/Allegro5/Allegro5Input.cpp
    )
    include_directories (./include) 
if(WANT_SHARED)
  add_library(agui SHARED ${AGUI_SOURCES})
  if(MACOSX)
  target_link_libraries (agui ${COCOA_LIBRARY})
  endif(MACOSX)
  set_target_properties(agui PROPERTIES DEFINE_SYMBOL "AGUI_BUILD")
  if(WANT_ALLEGRO5_BACKEND)
    add_library(agui_allegro5 SHARED ${ALLEGRO5_BACKEND_SOURCES})
  set_target_properties(agui_allegro5 PROPERTIES DEFINE_SYMBOL "AGUI_BACKEND_BUILD")
  target_link_libraries (agui_allegro5 agui)
  endif()
else()
  add_library(agui STATIC ${AGUI_SOURCES})
  if(MACOSX)
  target_link_libraries (agui ${COCOA_LIBRARY})
  endif(MACOSX)
    if(WANT_ALLEGRO5_BACKEND)
    add_library(agui_allegro5 STATIC ${ALLEGRO5_BACKEND_SOURCES})
   set_target_properties(agui_allegro5 PROPERTIES COMPILE_DEFINITIONS "ALLEGRO_STATICLINK")
  endif()
endif()

我告诉cmake找到并链接到可可，但它似乎没有做到。

感谢