Linux动态链接库的建立

hello.c

  1#include "hello.h"
  2 void hello()
  3 {
  4     printf("hello\n");
  5 }

hello.h

  1 #ifndef HELLO
  2 #define HELLO

  3 #include <stdio.h>
  4 void hello();

  5 #endif

test.c

  1 #include "hello.h"
  2 int main()
  3 {
  4     hello();
  5     return 0;
  6 }

1.创建动态链接库文件并编译

gcc -shared  hello.c  -o libhello.so

$gcc test.c

/tmp/cc8LkErr.o: In function `main':
test.c:(.text+0x12): undefined reference to `hello'
collect2: ld \u8fd4\u56de 1

不能找到函数hello

3添加链接库后编译

gcc test.c -lhello -L.

4.运行a.out

$ ./a.out 
./a.out: error while loading shared libraries: libhello.so: cannot open shared object file: No such file or directory

不能找到链接库libhello.so

5检测4的错误原因

$ ldd a.out 
	linux-gate.so.1 =>  (0x00110000)
	libhello.so => not found
	libc.so.6 => /lib/libc.so.6 (0x00879000)
	/lib/ld-linux.so.2 (0x00859000)

提示libhello.so这个库文件没有找到

6.添加环境变量

$ export LD_LIBRARY_PATH=/mnt:$LD_LIBRARY_PATH
./a.out
hello

7.现在检查

$ ldd a.out 
	linux-gate.so.1 =>  (0x00110000)
	libhello.so => /mnt/libhello.so (0x00111000)
	libc.so.6 => /lib/libc.so.6 (0x00879000)
	/lib/ld-linux.so.2 (0x00859000)

一切OK了

添加环境变量的方式有很多种

比如 /etc/ld.so.conf

    ~目下的.bash_profile都可以