使用库函数加载so库

main.c

# gcc -o main main.c -ldl

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
// Header files needed to include
#include <dlfcn.h> 

typedef int (*func_ptr_t)(int, int);
// Use absolute path
const char* so_path = "/home/ojenv_c/lib/libtongyishu.so";

// Need to specify library when compiling : -ldl
int main()
{
    // Open failed return NULL
    // RTLD_LAZ
    // RTLD_NOW
    // RTLD_GLOBAL
    // RTLD_LOCAL
    void* handle = dlopen(so_path, RTLD_NOW);
    if (handle == NULL) {
        fprintf(stderr, "[error] Open so error.
");
        return -1;
    }
    // Second parameter is function name
    func_ptr_t fptr = dlsym(handle, "tongyishu_add");
    fprintf(stdout, "%d
", fptr(1, 2));

    dlclose(handle);
    return 0;
}

a.c

# gcc  -fPIC -shared -o libtongyishu.so a.c

#include <stdlib.h>

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