C/C++使用dlopen手动加载动态so库

Posted 2022-03-03 木大白易

前言

类似于Java中System.load()和System.loadLibrary()，linux也提供了手动加载动态库的方式，就是通过dlopen打开，然后dlsym去获取函数或者变量的符号。

手动加载

C中动态加载

举个例子，在c中打开x264的一个函数：

#include <x264.h>
#include <dlfcn.h>

typedef int (*x264_encoder_encode_func)(x264_t *, x264_nal_t **pp_nal, int *pi_nal,
                                        x264_picture_t *pic_in, x264_picture_t *pic_out);

x264_encoder_encode_func x264EncoderEncodeFunc;

void dl_get_x264_addr()

    void *handle = dlopen("libx264.so", RTLD_LAZY);
    x264EncoderEncodeFunc = dlsym(handle, "x264_encoder_encode");



//下边可以直接使用x264EncoderEncodeFunc()

c++中动态加载

c++里稍微有点不一样

#include <x264.h>
#include <dlfcn.h>

int (*x264_encoder_encode_func)(x264_t *, x264_nal_t **pp_nal, int *pi_nal,
                                        x264_picture_t *pic_in, x264_picture_t *pic_out);

void dl_get_x264_addr()

    void *handle = dlopen("libx264.so", RTLD_LAZY);
    x264_encoder_encode_func = reinterpret_cast<int (*)(x264_t *, x264_nal_t **pp_nal, int *pi_nal,
                                        x264_picture_t *pic_in, x264_picture_t *pic_out)>(dlsym(handle, "x264_encoder_encode"));


//下边可以直接使用x264_encoder_encode_func()