尝试使用CMake编译项目时出错，其中SFML库由mingw提供

当我想用CMake和最新版本的SFML库一起编译项目时，我发现了很多奇怪的错误(c++)。

C生成代码：

cmake_minimum_required(VERSION 3.0)

project(MLproject)

SET(CMAKE_SYSTEM_NAME    Windows)
SET(CMAKE_SYSTEM_VERSION 1)
SET(CMAKE_C_COMPILER     "i686-w64-mingw32-gcc")
SET(CMAKE_CXX_COMPILER   "i686-w64-mingw32-g++")
SET(CMAKE_RC_COMPILER    "i686-w64-mingw32-windres")
SET(CMAKE_RANLIB         "i686-w64-mingw32-ranlib")
set(CMAKE_CXX_STANDARD 17)

SET(CMAKE_FIND_ROOT_PATH "/usr/i686-w64-mingw32")
SET(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
SET(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
SET(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)

set(SOURCE_EXE src/main.cpp)

set(SOURCE_GAME
  src/Boss/Boss.cpp
  *...*
  src/Game/Game.cpp)

set(SOURCE_UI
  src/UI/ScrollBar/ScrollBar.cpp)

add_library(UI SHARED ${SOURCE_UI})
add_library(Game SHARED ${SOURCE_GAME})

add_executable(main ${SOURCE_EXE})

target_link_libraries(main Game UI
  sfml-graphics sfml-system sfml-windos sfml-audio)

错误：

CMakeFiles/UI.dir/src/UI/ScrollBar/ScrollBar.cpp.o:ScrollBar.cpp:(.text+0x6d): undefined reference to `_imp___ZN2sf14RectangleShapeC1ERKNS_7Vector2IfEE'
CMakeFiles/UI.dir/src/UI/ScrollBar/ScrollBar.cpp.o:ScrollBar.cpp:(.text+0x399): undefined reference to `_imp___ZN2sf12RenderStates7DefaultE.....

我如何才能修复它？我会因为C++版本太旧而出错吗？(一切都针对Linux成功编译，但我想做跨平台)

---

解决方案

错误：

CMakeFiles/UI.dir/src/UI/ScrollBar/ScrollBar.cpp.o:ScrollBar.cpp:(.text+0x6d): undefined reference to `_imp___ZN2sf14RectangleShapeC1ERKNS_7Vector2IfEE'

表示UI库使用了一些SFML组件。但是，您只将SFML库链接到main可执行文件，因此该库不知道这些SFML引用是在哪里定义的。因此，您必须将任何相关的SFML库链接到UI目标：

target_link_libraries(UI PUBLIC sfml-graphics sfml-system sfml-windos sfml-audio)

在这里使用PUBLIC将SFML库传播给UI目标的使用者，例如您的main可执行文件。这样就不需要显式地将它们链接到main。以下是您进行以下更改的完整C Make：

cmake_minimum_required(VERSION 3.0)

project(MLproject)

# As commented, consider moving these calls to your toolchain file.
SET(CMAKE_SYSTEM_NAME    Windows)
SET(CMAKE_SYSTEM_VERSION 1)
SET(CMAKE_C_COMPILER     "i686-w64-mingw32-gcc")
SET(CMAKE_CXX_COMPILER   "i686-w64-mingw32-g++")
SET(CMAKE_RC_COMPILER    "i686-w64-mingw32-windres")
SET(CMAKE_RANLIB         "i686-w64-mingw32-ranlib")

SET(CMAKE_FIND_ROOT_PATH "/usr/i686-w64-mingw32")
SET(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
SET(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
SET(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)

set(CMAKE_CXX_STANDARD 17)

set(SOURCE_EXE src/main.cpp)

set(SOURCE_GAME
  src/Boss/Boss.cpp
  *...*
  src/Game/Game.cpp)

set(SOURCE_UI
  src/UI/ScrollBar/ScrollBar.cpp)

add_library(UI SHARED ${SOURCE_UI})
# Link SFML libraries to UI.
target_link_libraries(UI PUBLIC sfml-graphics sfml-system sfml-windos sfml-audio)

add_library(Game SHARED ${SOURCE_GAME})

add_executable(main ${SOURCE_EXE})

# Link Game and UI to the executable, which propagates the SFML libraries from UI also.
target_link_libraries(main PRIVATE Game UI)

注意，CMake顶部的许多调用都属于工具链文件(如注释所示)，通常用于cross-compiling。我鼓励您通读文档以确定您是否需要它，并了解如何设置它。