CMake: ELF文件加载动态库的位置

简单工程示例

1. world.c

#include<stdio.h>  
void world(void)
{  
    printf("world.\n");  
} 

2. hello.c

#include <stdio.h> 
 
void world(void);  
void hello(void) 
{  
    printf("hello\n");  
    world();  
}  

3. main.c

void main(void) 
{  
    hello();  
}  

2. 编译动态库

gcc -c -fPIC hello.c world.c  
gcc -shared -o libworld.so world.o 
gcc -shared -o libhello.so hello.o -lworld -L .

可见动态库libhello.so依赖于libworld.so

3. CMakeLists.txt

cmake_minimum_required(VERSION 3.2)
PROJECT(pro)        

SET(CMAKE_BUILD_TYPE Release)

SET(LINK_PATH .)
SET(LINK_PATH . )

INCLUDE_DIRECTORIES(${INCLUDE_PATH})
LINK_DIRECTORIES(${LINK_PATH})

ADD_EXECUTABLE(main main.c)
TARGET_LINK_LIBRARIES(main hello world)

这种方式生成的main ELF文件的默认动态库搜索路径是当前文件夹 ".";一旦当前文件夹下动态库不存在则找不到动态库，无法执行。此时可以通过设置 LD_LIBRARY_PATH 方式帮助ELF文件在相对应路径下查找动态库或者

cmake_minimum_required(VERSION 3.2)
PROJECT(pro)        

SET(CMAKE_BUILD_TYPE Release)

SET(LINK_PATH .)
SET(LINK_PATH . )

INCLUDE_DIRECTORIES(${INCLUDE_PATH})
LINK_DIRECTORIES(${LINK_PATH})

LINK_LIBRARIES(hello world -Wl,-rpath=/usr/local/lib)
ADD_EXECUTABLE(main main.c)

或者方案二

cmake_minimum_required(VERSION 3.2)
PROJECT(pro)        

SET(CMAKE_BUILD_TYPE Release)

SET(LINK_PATH .)
SET(LINK_PATH . /usr/local/lib)

INCLUDE_DIRECTORIES(${INCLUDE_PATH})
LINK_DIRECTORIES(${LINK_PATH})

ADD_EXECUTABLE(main main.c)
TARGET_LINK_LIBRARIES(main hello world)

或者方案三

cmake_minimum_required(VERSION 3.2)
PROJECT(pro)        

SET(CMAKE_BUILD_TYPE Release)

SET(LINK_PATH .)
SET(LINK_PATH . )

INCLUDE_DIRECTORIES(${INCLUDE_PATH})
LINK_DIRECTORIES(${LINK_PATH})

SET(CMAKE_EXE_LINKER_FLAGS '-Wl,-rpath=/usr/local/lib')
LINK_LIBRARIES(hello world)
ADD_EXECUTABLE(main main.c)

通过设置连接参数，将/usr/local/lib和当前文件夹路径写入到ELF文件内，则每次ELF将在/usr/local/lib路径下查找可执行文件