CMake 不会链接我的库，make 文件会

Question

背景

我最近为 c 和 c++ 下载了一个名为“RayLib”的库。我将 mingw 包含和库添加到我的项目中，现在我想链接它们。

问题

由于某种原因，cmake 没有链接静态库。当我尝试运行该项目时，它告诉我仍然存在对“InitWindow”和“SetTargetFPS”的未定义引用：

====================[ Build | Engine | Debug ]==================================
C:\Users\Lars\AppData\Local\JetBrains\Toolbox\apps\CLion\ch-0\203.7148.70\bin\cmake\win\bin\cmake.exe --build C:\Users\Lars\CLionProjects\Engine\cmake-build-debug --target Engine -- -j 9
C:\Users\Lars\AppData\Local\JetBrains\Toolbox\apps\CLion\ch-0\203.7148.70\bin\cmake\win\bin\cmake.exe -SC:\Users\Lars\CLionProjects\Engine -BC:\Users\Lars\CLionProjects\Engine\cmake-build-debug --check-build-system CMakeFiles\Makefile.cmake 0
C:/Users/Lars/Desktop/Development/MinGW/bin/mingw32-make.exe  -f CMakeFiles\Makefile2 Engine
mingw32-make.exe[1]: Entering directory 'C:/Users/Lars/CLionProjects/Engine/cmake-build-debug'
C:\Users\Lars\AppData\Local\JetBrains\Toolbox\apps\CLion\ch-0\203.7148.70\bin\cmake\win\bin\cmake.exe -SC:\Users\Lars\CLionProjects\Engine -BC:\Users\Lars\CLionProjects\Engine\cmake-build-debug --check-build-system CMakeFiles\Makefile.cmake 0
C:\Users\Lars\AppData\Local\JetBrains\Toolbox\apps\CLion\ch-0\203.7148.70\bin\cmake\win\bin\cmake.exe -E cmake_progress_start C:\Users\Lars\CLionProjects\Engine\cmake-build-debug\CMakeFiles 2
C:/Users/Lars/Desktop/Development/MinGW/bin/mingw32-make.exe  -f CMakeFiles\Makefile2 CMakeFiles/Engine.dir/all
mingw32-make.exe[2]: Entering directory 'C:/Users/Lars/CLionProjects/Engine/cmake-build-debug'
C:/Users/Lars/Desktop/Development/MinGW/bin/mingw32-make.exe  -f CMakeFiles\Engine.dir\build.make CMakeFiles/Engine.dir/depend
mingw32-make.exe[3]: Entering directory 'C:/Users/Lars/CLionProjects/Engine/cmake-build-debug'
C:\Users\Lars\AppData\Local\JetBrains\Toolbox\apps\CLion\ch-0\203.7148.70\bin\cmake\win\bin\cmake.exe -E cmake_depends "MinGW Makefiles" C:\Users\Lars\CLionProjects\Engine C:\Users\Lars\CLionProjects\Engine C:\Users\Lars\CLionProjects\Engine\cmake-build-debug C:\Users\Lars\CLionProjects\Engine\cmake-build-debug C:\Users\Lars\CLionProjects\Engine\cmake-build-debug\CMakeFiles\Engine.dir\DependInfo.cmake --color=
mingw32-make.exe[3]: Leaving directory 'C:/Users/Lars/CLionProjects/Engine/cmake-build-debug'
C:/Users/Lars/Desktop/Development/MinGW/bin/mingw32-make.exe  -f CMakeFiles\Engine.dir\build.make CMakeFiles/Engine.dir/build
mingw32-make.exe[3]: Entering directory 'C:/Users/Lars/CLionProjects/Engine/cmake-build-debug'
[ 50%] Linking CXX executable Engine.exe
C:\Users\Lars\AppData\Local\JetBrains\Toolbox\apps\CLion\ch-0\203.7148.70\bin\cmake\win\bin\cmake.exe -E cmake_link_script CMakeFiles\Engine.dir\link.txt --verbose=1
C:\Users\Lars\AppData\Local\JetBrains\Toolbox\apps\CLion\ch-0\203.7148.70\bin\cmake\win\bin\cmake.exe -E rm -f CMakeFiles\Engine.dir/objects.a
C:\Users\Lars\Desktop\Development\MinGW\bin\ar.exe cr CMakeFiles\Engine.dir/objects.a @CMakeFiles\Engine.dir\objects1.rsp
C:\Users\Lars\Desktop\Development\MinGW\bin\g++.exe  -Wall -std=c++17 -g   -Wl,--whole-archive CMakeFiles\Engine.dir/objects.a -Wl,--no-whole-archive  -o Engine.exe -Wl,--out-implib,libEngine.dll.a -Wl,--major-image-version,0,--minor-image-version,0 @CMakeFiles\Engine.dir\linklibs.rsp
c:/users/lars/desktop/development/mingw/bin/../lib/gcc/mingw32/9.2.0/../../../../mingw32/bin/ld.exe: CMakeFiles\Engine.dir/objects.a(main.cpp.obj): in function `main':
C:/Users/Lars/CLionProjects/Engine/main.cpp:22: undefined reference to `InitWindow'
c:/users/lars/desktop/development/mingw/bin/../lib/gcc/mingw32/9.2.0/../../../../mingw32/bin/ld.exe: C:/Users/Lars/CLionProjects/Engine/main.cpp:24: undefined reference to `SetTargetFPS'
c:/users/lars/desktop/development/mingw/bin/../lib/gcc/mingw32/9.2.0/../../../../mingw32/bin/ld.exe: C:/Users/Lars/CLionProjects/Engine/main.cpp:28: undefined reference to `WindowShouldClose'
c:/users/lars/desktop/development/mingw/bin/../lib/gcc/mingw32/9.2.0/../../../../mingw32/bin/ld.exe: C:/Users/Lars/CLionProjects/Engine/main.cpp:37: undefined reference to `BeginDrawing'
c:/users/lars/desktop/development/mingw/bin/../lib/gcc/mingw32/9.2.0/../../../../mingw32/bin/ld.exe: C:/Users/Lars/CLionProjects/Engine/main.cpp:39: undefined reference to `ClearBackground'
c:/users/lars/desktop/development/mingw/bin/../lib/gcc/mingw32/9.2.0/../../../../mingw32/bin/ld.exe: C:/Users/Lars/CLionProjects/Engine/main.cpp:41: undefined reference to `DrawText'
c:/users/lars/desktop/development/mingw/bin/../lib/gcc/mingw32/9.2.0/../../../../mingw32/bin/ld.exe: C:/Users/Lars/CLionProjects/Engine/main.cpp:43: undefined reference to `EndDrawing'
c:/users/lars/desktop/development/mingw/bin/../lib/gcc/mingw32/9.2.0/../../../../mingw32/bin/ld.exe: C:/Users/Lars/CLionProjects/Engine/main.cpp:49: undefined reference to `CloseWindow'
collect2.exe: error: ld returned 1 exit status
mingw32-make.exe[3]: *** [Engine.exe] Error 1
mingw32-make.exe[2]: *** [CMakeFiles/Engine.dir/all] Error 2
mingw32-make.exe[1]: *** [CMakeFiles/Engine.dir/rule] Error 2
mingw32-make.exe: *** [Engine] Error 2
CMakeFiles\Engine.dir\build.make:108: recipe for target 'Engine.exe' failed
mingw32-make.exe[3]: Leaving directory 'C:/Users/Lars/CLionProjects/Engine/cmake-build-debug'
CMakeFiles\Makefile2:97: recipe for target 'CMakeFiles/Engine.dir/all' failed
mingw32-make.exe[2]: Leaving directory 'C:/Users/Lars/CLionProjects/Engine/cmake-build-debug'
CMakeFiles\Makefile2:104: recipe for target 'CMakeFiles/Engine.dir/rule' failed
mingw32-make.exe[1]: Leaving directory 'C:/Users/Lars/CLionProjects/Engine/cmake-build-debug'
Makefile:140: recipe for target 'Engine' failed

我的 cmake 文件看起来像这样...

cmake_minimum_required(VERSION 3.17)
project(Engine)

set(CMAKE_CXX_STANDARD 14)
set(CMAKE_VERBOSE_MAKEFILE ON)

include_directories(include)
include_directories(libs)
link_directories(libs)

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -std=c++17")
add_executable(Engine main.cpp)
target_link_libraries(Engine raylib)

我自己写的make文件，位于根目录下，只需添加一个-I include，-L libs和-lraylib就可以编译这个项目了。

main: main.o
   g++ -I include ... -o main main.o -L libs -lraylib
main.o: main.cpp
   g++ -I include ... -c main.cpp -L libs -lraylib

问题

为什么 target_link_libraries 不工作？为什么它不链接我位于 libs/ 的 .a 文件？我在这里做错了什么？为什么Cmake不能链接我的项目，而我自己的makefile却可以呢？

欢迎任何帮助！

Answer 1

来自关于命令link_directories()的文档：

这个命令很少需要，应该避免在有其他选择的情况下使用。尽可能将完整的绝对路径传递给库，因为这样可以确保始终链接正确的库。 find_library() 命令提供完整路径，一般可以直接在调用 target_link_libraries() 时使用。

find_library() 本身就足够了。