CMake link a library (.a/.so)

Question

我有以下项目文件结构：

libs/
  └──FreeImage/
        ├── FreeImage.dll
        ├── FreeImage.h
        ├── FreeImage.lib
        ├── license-fi.txt
        ├── license-gplv2.txt
        └── license-gplv3.txt
main.cpp
CMakeLists.txt

我的CMakeLists.txt ：

cmake_minimum_required(VERSION 2.8.4)
project(untitled)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
set(FREEIMAGE_LIBRARY_AND_HEADER_DIRECTORY libs/FreeImage)
find_path(FREEIMAGE_LIBRARY_AND_HEADER_DIRECTORY FreeImage.h)
find_library(FREEIMAGE_LIBRARY_AND_HEADER_DIRECTORY freeimage)
include_directories(${FREEIMAGE_LIBRARY_AND_HEADER_DIRECTORY})
set(SOURCE_FILES main.cpp)
add_executable(main ${SOURCE_FILES})
target_link_libraries(main freeimage)

我按照这个写了我的CMakeLists.txt，但它对我不起作用。

输出：

/home/username/main_ssd/soft/linux/portable/clion-140.569.17/bin/cmake/bin/cmake --build /home/username/.clion10/system/cmake/generated/70336599/70336599/Debug --target main -- -j 4
-- Configuring done
-- Generating done
-- Build files have been written to: /home/username/.clion10/system/cmake/generated/70336599/70336599/Debug
Scanning dependencies of target main
[100%] Building CXX object CMakeFiles/main.dir/main.cpp.o
Linking CXX executable main
/usr/bin/ld: cannot find -lfreeimage
collect2: error: ld returned 1 exit status
CMakeFiles/main.dir/build.make:85: recipe for target 'main' failed
make[3]: *** [main] Error 1
CMakeFiles/Makefile2:60: recipe for target 'CMakeFiles/main.dir/all' failed
make[2]: *** [CMakeFiles/main.dir/all] Error 2
CMakeFiles/Makefile2:72: recipe for target 'CMakeFiles/main.dir/rule' failed
make[1]: *** [CMakeFiles/main.dir/rule] Error 2
Makefile:160: recipe for target 'main' failed
make: *** [main] Error 2

Answer 1

> set(FREEIMAGE_LIBRARY_AND_HEADER_DIRRECTORY libs/FreeImage)

变量FREEIMAGE_LIBRARY_AND_HEADER_DIRRECTORY设置为 libs/FreeImage

find_path(FREEIMAGE_LIBRARY_AND_HEADER_DIRRECTORY FreeImage.h)

变量 FREEIMAGE_LIBRARY_AND_HEADER_DIRRECTORY 设置为包含命名文件FreeImage.h的目录。不存在命令的提示，因为缺少可选参数 PATH 或 HINT

find_library(FREEIMAGE_LIBRARY_AND_HEADER_DIRRECTORY freeimage)变量 FREEIMAGE_LIBRARY_AND_HEADER_DIRRECTORY 设置为库FreeImage的完整路径（如果找到）。不存在命令的提示，因为缺少可选参数 PATH 或 HINT

include_directories(${FREEIMAGE_LIBRARY_AND_HEADER_DIRRECTORY})

变量FREEIMAGE_LIBRARY_AND_HEADER_DIRRECTORY包含库FreeImage的完整路径（如果找到）。

target_link_libraries(main freeimage)

CMakeList 中不存在名称freeimage的目标.txt因此被解释为要链接-lfreeimage

问：你为什么尝试在Linux上使用"dll"？

Answer 2

我已经下载了新版本的FreeImage库（从这里）并按照以下说明编译它：

Compiling FreeImagePlus
-----------------------
FreeImagePlus is a C++ wrapper for FreeImage. 
To compile FreeImage as a C++ library, follow these steps : 
1) Enter the FreeImage directory
2) Build the distribution : 
make -f Makefile.fip
make -f Makefile.fip install
3) Clean all files produced during the build process
make -f Makefile.fip clean

所以我有以下库的文件结构：

libs/FreeImage/
├── FreeImage.h
├── FreeImagePlus.h
├── libfreeimageplus-3.16.0.so
├── libfreeimageplus.a
├── license-fi.txt
├── license-gplv2.txt
└── license-gplv3.txt

然后我修改了我的CMakeLists.txt如下所示：

cmake_minimum_required(VERSION 2.8.4)
project(untitled)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
find_path(SIFTGPU_INCLUDE_DIR FreeImage.h)
find_library(SIFTGPU_LIBRARY libfreeimageplus)
include_directories(${SIFTGPU_INCLUDE_DIR})
add_executable(main ${SOURCE_FILES})
target_link_libraries(main freeimageplus)

Answer 3

彼得为你指出了正确的方向：

target_link_libraries(main freeimage)

应替换为：

target_link_libraries(main ${freeimage})

其中${freeimage}是包含要链接到的库路径值的变量，使用 find_library 检索。

希望对您有所帮助。