c++ - CMake - 尝试构建项目时遇到 undefined reference

Question

我目前正在尝试在 Windows 上使用 CMake 来构建一个包含 2 个库(GLEW 和 SDL2)的 C++ 项目，但是在这样做时我收到一个 undefined reference 错误，如下所示:-

PS D:\Projects\C++Projects\game_engine\build>> cmg ..
-- The C compiler identification is GNU 7.1.0
-- The CXX compiler identification is GNU 7.1.0
-- Check for working C compiler: C:/Program Files/MinGW-w64/mingw64/bin/gcc.exe
-- Check for working C compiler: C:/Program Files/MinGW-w64/mingw64/bin/gcc.exe -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: C:/Program Files/MinGW-w64/mingw64/bin/g++.exe
-- Check for working CXX compiler: C:/Program Files/MinGW-w64/mingw64/bin/g++.exe -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done
-- Generating done
-- Build files have been written to: D:/Projects/C++Projects/game_engine/build
Scanning dependencies of target game_engine
[ 25%] Building CXX object CMakeFiles/game_engine.dir/src/MainGame.cpp.obj
[ 50%] Building CXX object CMakeFiles/game_engine.dir/src/Sprite.cpp.obj
[ 75%] Building CXX object CMakeFiles/game_engine.dir/src/main.cpp.obj
[100%] Linking CXX executable game_engine.exe
CMakeFiles\game_engine.dir/objects.a(MainGame.cpp.obj):MainGame.cpp:(.text+0x4b): undefined reference to `SDL_Quit'
CMakeFiles\game_engine.dir/objects.a(MainGame.cpp.obj):MainGame.cpp:(.text+0x141): undefined reference to `SDL_Init'
CMakeFiles\game_engine.dir/objects.a(MainGame.cpp.obj):MainGame.cpp:(.text+0x175): undefined reference to `SDL_CreateWindow'
CMakeFiles\game_engine.dir/objects.a(MainGame.cpp.obj):MainGame.cpp:(.text+0x1e4): undefined reference to `SDL_GL_CreateContext'
CMakeFiles\game_engine.dir/objects.a(MainGame.cpp.obj):MainGame.cpp:(.text+0x240): undefined reference to `__imp_glewInit'
CMakeFiles\game_engine.dir/objects.a(MainGame.cpp.obj):MainGame.cpp:(.text+0x2a4): undefined reference to `SDL_GL_SetAttribute'
CMakeFiles\game_engine.dir/objects.a(MainGame.cpp.obj):MainGame.cpp:(.text+0x2c1): undefined reference to `glClearColor'
CMakeFiles\game_engine.dir/objects.a(MainGame.cpp.obj):MainGame.cpp:(.text+0x39e): undefined reference to `SDL_PollEvent'
CMakeFiles\game_engine.dir/objects.a(MainGame.cpp.obj):MainGame.cpp:(.text+0x438): undefined reference to `glClearDepth'
CMakeFiles\game_engine.dir/objects.a(MainGame.cpp.obj):MainGame.cpp:(.text+0x442): undefined reference to `glClear'
CMakeFiles\game_engine.dir/objects.a(MainGame.cpp.obj):MainGame.cpp:(.text+0x461): undefined reference to `SDL_GL_SwapWindow'
CMakeFiles\game_engine.dir/objects.a(Sprite.cpp.obj):Sprite.cpp:(.text+0x30): undefined reference to `__imp___glewDeleteBuffers'
CMakeFiles\game_engine.dir/objects.a(Sprite.cpp.obj):Sprite.cpp:(.text+0xae): undefined reference to `__imp___glewGenBuffers'
CMakeFiles\game_engine.dir/objects.a(Sprite.cpp.obj):Sprite.cpp:(.text+0x15d): undefined reference to `__imp___glewBindBuffer'
CMakeFiles\game_engine.dir/objects.a(Sprite.cpp.obj):Sprite.cpp:(.text+0x175): undefined reference to `__imp___glewBufferData'
CMakeFiles\game_engine.dir/objects.a(Sprite.cpp.obj):Sprite.cpp:(.text+0x198): undefined reference to `__imp___glewBindBuffer'
CMakeFiles\game_engine.dir/objects.a(Sprite.cpp.obj):Sprite.cpp:(.text+0x1c1): undefined reference to `__imp___glewBindBuffer'
CMakeFiles\game_engine.dir/objects.a(Sprite.cpp.obj):Sprite.cpp:(.text+0x1d9): undefined reference to `__imp___glewEnableVertexAttribArray' CMakeFiles\game_engine.dir/objects.a(Sprite.cpp.obj):Sprite.cpp:(.text+0x1ea): undefined reference to `__imp___glewVertexAttribPointer'
CMakeFiles\game_engine.dir/objects.a(Sprite.cpp.obj):Sprite.cpp:(.text+0x22b): undefined reference to `glDrawArrays'
CMakeFiles\game_engine.dir/objects.a(Sprite.cpp.obj):Sprite.cpp:(.text+0x232): undefined reference to `__imp___glewDisableVertexAttribArray'

CMakeFiles\game_engine.dir/objects.a(Sprite.cpp.obj):Sprite.cpp:(.text+0x243): undefined reference to `__imp___glewBindBuffer'
C:/PROGRA~1/MINGW-~1/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/7.1.0/../../../../x86_64-w64-mingw32/lib/../lib/libmingw32.a(lib64_libmingw32_a-crt0_c.o):crt0_c.c:(.text.startup+0x2e): undefined reference to `WinMain'
collect2.exe: error: ld returned 1 exit status
make[2]: *** [CMakeFiles\game_engine.dir\build.make:118: game_engine.exe] Error 1
make[1]: *** [CMakeFiles\Makefile2:67: CMakeFiles/game_engine.dir/all] Error 2
make: *** [Makefile:83: all] Error 2

项目树是:-

Root
|-build
|-include
   |-GL
   |-SDL2
   |-MainGame.h
   \-Sprite.h
|-lib
   |-glew32.lib
   |-glew32s.lib
   |-SDL2.lib
   |-SDL2main.lib
   \-SDL2test.lib
\-src
   |-main.cpp
   |-MainGame.cpp
   \-Sprite.cpp

我的 CMakeLists.txt 文件如下所示:-

cmake_minimum_required(VERSION 3.11.4)

project (game_engine)

# Bring header files into scope
include_directories(include)
include_directories(include/SDL2)
include_directories(include/GL)

# Retrieve all source files
file(GLOB SOURCES "src/*.cpp")

add_executable(game_engine ${SOURCES})
target_link_libraries(game_engine -L./lib)

目前，我认为 undefined reference 是编译器未在 SDL 和 GLEW 库中找到相应的 .cpp 文件的结果。

这让我相信 CMakeLists.txt 文件中的最后一行没有成功链接两个库的 .lib 文件。

任何帮助都将不胜感激，如果上述错误是由于项目结构不佳造成的(我怀疑这是这里的主要问题)，我将很乐意对其进行更改。

谢谢。

编辑(1):

我想添加一些我刚刚注意到的内容，即 cmake 实际上生成了一个 makefile，但紧接着运行 make 是产生 undefined reference 错误的原因。检查 makefile，我发现根本没有链接库，这再次证实 target_link_libraries() 无法链接 SDL 和 GLEW。

这是更新后的 CMakeLists.txt 文件:

cmake_minimum_required(VERSION 3.11.4)       

# Project Name                               
project (game_engine)                        

# Retrieve all source files                  
set(SOURCES                                  
        ${CMAKE_SOURCE_DIR}/src/main.cpp     
        ${CMAKE_SOURCE_DIR}/src/MainGame.cpp 
        ${CMAKE_SOURCE_DIR}/src/Sprite.cpp)  

add_executable(game_engine ${SOURCES})       

target_include_directories(game_engine PUBLIC
        include                              
        include/SDL2                         
        include/GL)                          

target_link_libraries(game_engine            
        ${CMAKE_SOURCE_DIR}/lib/glew32.lib   
        ${CMAKE_SOURCE_DIR}/lib/glew32s.lib  
        ${CMAKE_SOURCE_DIR}/lib/SDL2.lib     
        ${CMAKE_SOURCE_DIR}/lib/SDL2main.lib 
        ${CMAKE_SOURCE_DIR}/lib/SDL2test.lib)

和生成的 makefile:

# CMAKE generated file: DO NOT EDIT!
# Generated by "MinGW Makefiles" Generator, CMake Version 3.11

# Default target executed when no arguments are given to make.
default_target: all

.PHONY : default_target

# Allow only one "make -f Makefile2" at a time, but pass parallelism.
.NOTPARALLEL:


#=============================================================================
# Special targets provided by cmake.

# Disable implicit rules so canonical targets will work.
.SUFFIXES:


# Remove some rules from gmake that .SUFFIXES does not remove.
SUFFIXES =

.SUFFIXES: .hpux_make_needs_suffix_list


# Suppress display of executed commands.
$(VERBOSE).SILENT:


# A target that is always out of date.
cmake_force:

.PHONY : cmake_force

#=============================================================================
# Set environment variables for the build.

SHELL = cmd.exe

# The CMake executable.
CMAKE_COMMAND = D:\CMake\bin\cmake.exe

# The command to remove a file.
RM = D:\CMake\bin\cmake.exe -E remove -f

# Escaping for special characters.
EQUALS = =

# The top-level source directory on which CMake was run.
CMAKE_SOURCE_DIR = D:\Projects\C++Projects\game_engine

# The top-level build directory on which CMake was run.
CMAKE_BINARY_DIR = D:\Projects\C++Projects\game_engine\build

#=============================================================================
# Targets provided globally by CMake.

# Special rule for the target edit_cache
edit_cache:
        @$(CMAKE_COMMAND) -E cmake_echo_color --switch=$(COLOR) --cyan "Running CMake cache editor..."
        D:\CMake\bin\cmake-gui.exe -H$(CMAKE_SOURCE_DIR) -B$(CMAKE_BINARY_DIR)
.PHONY : edit_cache

# Special rule for the target edit_cache
edit_cache/fast: edit_cache

.PHONY : edit_cache/fast

# Special rule for the target rebuild_cache
rebuild_cache:
        @$(CMAKE_COMMAND) -E cmake_echo_color --switch=$(COLOR) --cyan "Running CMake to regenerate build system..."
        D:\CMake\bin\cmake.exe -H$(CMAKE_SOURCE_DIR) -B$(CMAKE_BINARY_DIR)
.PHONY : rebuild_cache

# Special rule for the target rebuild_cache
rebuild_cache/fast: rebuild_cache

.PHONY : rebuild_cache/fast

# The main all target
all: cmake_check_build_system
        $(CMAKE_COMMAND) -E cmake_progress_start D:\Projects\C++Projects\game_engine\build\CMakeFiles D:\Projects\C++Projects\game_engine\build\CMakeFiles\progress.marks
        $(MAKE) -f CMakeFiles\Makefile2 all
        $(CMAKE_COMMAND) -E cmake_progress_start D:\Projects\C++Projects\game_engine\build\CMakeFiles 0
.PHONY : all

# The main clean target
clean:
        $(MAKE) -f CMakeFiles\Makefile2 clean
.PHONY : clean

# The main clean target
clean/fast: clean

.PHONY : clean/fast

# Prepare targets for installation.
preinstall: all
        $(MAKE) -f CMakeFiles\Makefile2 preinstall
.PHONY : preinstall

# Prepare targets for installation.
preinstall/fast:
        $(MAKE) -f CMakeFiles\Makefile2 preinstall
.PHONY : preinstall/fast

# clear depends
depend:
        $(CMAKE_COMMAND) -H$(CMAKE_SOURCE_DIR) -B$(CMAKE_BINARY_DIR) --check-build-system CMakeFiles\Makefile.cmake 1
.PHONY : depend

#=============================================================================
# Target rules for targets named game_engine

# Build rule for target.
game_engine: cmake_check_build_system
        $(MAKE) -f CMakeFiles\Makefile2 game_engine
.PHONY : game_engine

# fast build rule for target.
game_engine/fast:
        $(MAKE) -f CMakeFiles\game_engine.dir\build.make CMakeFiles/game_engine.dir/build
.PHONY : game_engine/fast

src/MainGame.obj: src/MainGame.cpp.obj

.PHONY : src/MainGame.obj

# target to build an object file
src/MainGame.cpp.obj:
        $(MAKE) -f CMakeFiles\game_engine.dir\build.make CMakeFiles/game_engine.dir/src/MainGame.cpp.obj
.PHONY : src/MainGame.cpp.obj

src/MainGame.i: src/MainGame.cpp.i

.PHONY : src/MainGame.i

# target to preprocess a source file
src/MainGame.cpp.i:
        $(MAKE) -f CMakeFiles\game_engine.dir\build.make CMakeFiles/game_engine.dir/src/MainGame.cpp.i
.PHONY : src/MainGame.cpp.i

src/MainGame.s: src/MainGame.cpp.s

.PHONY : src/MainGame.s

# target to generate assembly for a file
src/MainGame.cpp.s:
        $(MAKE) -f CMakeFiles\game_engine.dir\build.make CMakeFiles/game_engine.dir/src/MainGame.cpp.s
.PHONY : src/MainGame.cpp.s

src/Sprite.obj: src/Sprite.cpp.obj

.PHONY : src/Sprite.obj

# target to build an object file
src/Sprite.cpp.obj:
        $(MAKE) -f CMakeFiles\game_engine.dir\build.make CMakeFiles/game_engine.dir/src/Sprite.cpp.obj
.PHONY : src/Sprite.cpp.obj

src/Sprite.i: src/Sprite.cpp.i

.PHONY : src/Sprite.i

# target to preprocess a source file
src/Sprite.cpp.i:
        $(MAKE) -f CMakeFiles\game_engine.dir\build.make CMakeFiles/game_engine.dir/src/Sprite.cpp.i
.PHONY : src/Sprite.cpp.i

src/Sprite.s: src/Sprite.cpp.s

.PHONY : src/Sprite.s

# target to generate assembly for a file
src/Sprite.cpp.s:
        $(MAKE) -f CMakeFiles\game_engine.dir\build.make CMakeFiles/game_engine.dir/src/Sprite.cpp.s
.PHONY : src/Sprite.cpp.s

src/main.obj: src/main.cpp.obj

.PHONY : src/main.obj

# target to build an object file
src/main.cpp.obj:
        $(MAKE) -f CMakeFiles\game_engine.dir\build.make CMakeFiles/game_engine.dir/src/main.cpp.obj
.PHONY : src/main.cpp.obj

src/main.i: src/main.cpp.i

.PHONY : src/main.i

# target to preprocess a source file
src/main.cpp.i:
        $(MAKE) -f CMakeFiles\game_engine.dir\build.make CMakeFiles/game_engine.dir/src/main.cpp.i .PHONY : src/main.cpp.i

src/main.s: src/main.cpp.s

.PHONY : src/main.s

# target to generate assembly for a file
src/main.cpp.s:
        $(MAKE) -f CMakeFiles\game_engine.dir\build.make CMakeFiles/game_engine.dir/src/main.cpp.s .PHONY : src/main.cpp.s

# Help Target
help:
        @echo The following are some of the valid targets for this Makefile:
        @echo ... all (the default if no target is provided)
        @echo ... clean
        @echo ... depend
        @echo ... game_engine
        @echo ... edit_cache
        @echo ... rebuild_cache
        @echo ... src/MainGame.obj
        @echo ... src/MainGame.i
        @echo ... src/MainGame.s
        @echo ... src/Sprite.obj
        @echo ... src/Sprite.i
        @echo ... src/Sprite.s
        @echo ... src/main.obj
        @echo ... src/main.i
        @echo ... src/main.s
.PHONY : help



#=============================================================================
# Special targets to cleanup operation of make.

# Special rule to run CMake to check the build system integrity.
# No rule that depends on this can have commands that come from listfiles
# because they might be regenerated.
cmake_check_build_system:
        $(CMAKE_COMMAND) -H$(CMAKE_SOURCE_DIR) -B$(CMAKE_BINARY_DIR) --check-build-system CMakeFiles\Makefile.cmake 0
.PHONY : cmake_check_build_system

编辑(2):已解决

在确定 .lib 文件没有正确链接后，我决定通过它们的源包重新下载 GLEW 和 SDL2 库。它们都带有 cmake 作为构建选项，因此我能够访问静态库 (.a) + 导入库 (.dll.a)。

我用这些库替换了 lib 的内容并更新了我的 CMakeLists.txt 文件以包含它们以及 OpenGL 库:

cmake_minimum_required(VERSION 3.11.4)

# Project Name
project (game_engine)

# Retrieve all source files
set(SOURCES
        "${CMAKE_SOURCE_DIR}/src/main.cpp"
        "${CMAKE_SOURCE_DIR}/src/MainGame.cpp"
        "${CMAKE_SOURCE_DIR}/src/Sprite.cpp")

add_executable(game_engine ${SOURCES})

find_package(OpenGL REQUIRED)

target_include_directories(game_engine PUBLIC
        include
        include/SDL2
        include/GL
        ${OPENGL_INCLUDE_DIRS})

target_link_libraries(game_engine
        "${CMAKE_SOURCE_DIR}/lib/glew32.dll"
        "${CMAKE_SOURCE_DIR}/lib/libglew32.a"
        "${CMAKE_SOURCE_DIR}/lib/libglew32.dll.a"
        "${CMAKE_SOURCE_DIR}/lib/libSDL2.dll"
        "${CMAKE_SOURCE_DIR}/lib/libSDL2.dll.a"
        "${CMAKE_SOURCE_DIR}/lib/libSDL2main.a"
        "${CMAKE_SOURCE_DIR}/lib/libSDL2-static.a"
        "${OPENGL_LIBRARIES}")

add_custom_command(TARGET game_engine POST_BUILD
        COMMAND ${CMAKE_COMMAND} -E copy_if_different
        "${CMAKE_SOURCE_DIR}/lib/glew32.dll"
        "${CMAKE_BINARY_DIR}")

add_custom_command(TARGET game_engine POST_BUILD
        COMMAND ${CMAKE_COMMAND} -E copy_if_different
        "${CMAKE_SOURCE_DIR}/lib/libSDL2.dll"
        "${CMAKE_BINARY_DIR}")

这解决了 undefined reference 的主要问题，但还剩下一个问题，即对 WinMain 的 undefined reference 。为了解决这个问题，我在包含“SDL.h”之前将 #define SDL_MAIN_HANDLED 添加到我的 main.cpp 文件中。

Answer 1

target_link_libraries需要 CMake 目标或库路径。

尝试改变

target_link_libraries(game_engine -L./lib)

与

target_link_libraries(game_engine
    ${CMAKE_SOURCE_DIR}/lib/libglew32.lib
    ${CMAKE_SOURCE_DIR}/lib/glew32s.lib
    ${CMAKE_SOURCE_DIR}/lib/SDL2.lib
    ${CMAKE_SOURCE_DIR}/lib/SDL2main.lib
    ${CMAKE_SOURCE_DIR}/lib/SDL2test.lib
    )

其他一些建议:

• (1) 更喜欢显式列出源而不是使用 GLOB。参见 file(GLOB...)合理的文档
• (2) 而不是 include_directories 更喜欢使用 target_include_directories
• (3) 不推荐在您的版本控制系统中包含二进制文件。相反，您可以使用 CMake 直接下载它们。我可以提供有关可能方法的更多详细信息
• (4) 理想情况下使用调用 find_package(SDL2 REQUIRED) , find_package(Glew REQUIRED)并链接到导入的目标(或使用像 GLEW_LIBRARIES 这样的变量)会更健壮。