动态链接库DLL的加载：隐式加载(载入时加载)和显式加载(运行时加载)

#include<stdio.h>
extern int add(int, int);  // 也可以是 _declspec(dllimport) int add(int, int);
extern int sub(int, int);  // 也可以是 _declspec(dllimport) int sub(int, int);
int main(){
    int a=10, b=5;
    printf("a+b=%d\n", add(a, b));
    printf("a-b=%d\n", sub(a, b));
    return 0;
}

#include<stdio.h>
#pragma comment(lib, "dllDemo.lib")
_declspec(dllimport) int add(int, int);
_declspec(dllimport) int sub(int, int);
int main(){
    int a=10, b=5;
    printf("a+b=%d\n", add(a, b));
    printf("a-b=%d\n", sub(a, b));
    return 0;
}

#ifndef _DLLDEMO_H
#define _DLLDEMO_H
#pragma comment(lib, "dllDemo.lib")
_declspec(dllexport) int add(int, int);
_declspec(dllexport) int sub(int, int);
#endif

#include<stdio.h>
#include "dllDemo.h"
int main(){
    int a=10, b=5;
    printf("a+b=%d\n", add(a, b));
    printf("a-b=%d\n", sub(a, b));
    return 0;
}

#include<stdio.h>
#include<stdlib.h>
#include<windows.h>  // 必须包含 windows.h
typedef int (*FUNADDR)();  // 指向函数的指针
int main(){
    int a=10, b=5;
   
    HINSTANCE dllDemo = LoadLibrary("dllDemo.dll");
    FUNADDR add, sub;
    if(dllDemo){
        add = (FUNADDR)GetProcAddress(dllDemo, "add");
        sub = (FUNADDR)GetProcAddress(dllDemo, "sub");
    }else{
        printf("Fail to load DLL!\n");
        system("pause");
        exit(1);
    }
    printf("a+b=%d\n", add(a, b));
    printf("a-b=%d\n", sub(a, b));
    system("pause");
    return 0;
}