动态库的生成 _0303

#Makefile

all:
    gcc -shared -fPIC sub.c add.c -o libmath.so
    gcc main.c -o main -ldl
clean:
    rm main libmath.so
.PHONY:clean all

//add.c

int add(int a, int b)
{
    return a + b;
}

//sub.c

int sub(int a, int b)
{
    return a - b;
}

//main.c

#include <stdio.h>
#include "math.h"
#include <dlfcn.h>
#include <stdlib.h>

typedef int (*funcp_t)(int, int);

int main(void)
{
    void *handle;
    funcp_t fun;

    handle = dlopen("libmath.so", RTLD_NOW);
    fun = dlsym(handle, "sub");

    if(handle == NULL || fun == NULL)
    {
        printf("not find libmath.so\n");
        exit(EXIT_FAILURE);
    }

    printf("sub: %d\n", fun(3, 5));

    dlclose(handle);

    return 0;

}