在C++中,从可执行文件中调用动态链接库(DLL)的虚函数涉及到几个关键步骤。以下是详细的解释和示例代码。
首先,创建一个包含虚函数的DLL项目。
DLL项目(MyLibrary)
// MyLibrary.h
#pragma once
#ifdef MYLIBRARY_EXPORTS
#define MYLIBRARY_API __declspec(dllexport)
#else
#define MYLIBRARY_API __declspec(dllimport)
#endif
class MYLIBRARY_API Base {
public:
virtual void VirtualFunction() = 0;
};
class Derived : public Base {
public:
void VirtualFunction() override {
// 实现虚函数
std::cout << "Derived::VirtualFunction called!" << std::endl;
}
};
// MyLibrary.cpp
#include "MyLibrary.h"
编译生成DLL文件(MyLibrary.dll)和对应的导入库(MyLibrary.lib)。
接下来,在可执行文件中加载并使用DLL中的虚函数。
可执行文件项目(MyApp)
// MyApp.cpp
#include <windows.h>
#include <iostream>
#include "MyLibrary.h"
typedef Base* (*CreateDerivedFunc)();
int main() {
HMODULE hModule = LoadLibrary(L"MyLibrary.dll");
if (!hModule) {
std::cerr << "Failed to load DLL" << std::endl;
return 1;
}
CreateDerivedFunc CreateDerived = (CreateDerivedFunc)GetProcAddress(hModule, "?CreateDerived@@YA?AVBase@@XZ");
if (!CreateDerived) {
std::cerr << "Failed to get function address" << std::endl;
FreeLibrary(hModule);
return 1;
}
Base* derived = CreateDerived();
if (derived) {
derived->VirtualFunction(); // 调用虚函数
delete derived;
}
FreeLibrary(hModule);
return 0;
}
为了在DLL中创建派生类实例,需要导出一个工厂函数。
MyLibrary.h
extern "C" MYLIBRARY_API Base* CreateDerived();
MyLibrary.cpp
#include "MyLibrary.h"
extern "C" MYLIBRARY_API Base* CreateDerived() {
return new Derived();
}
通过以上步骤和示例代码,可以在C++项目中成功调用动态链接库中的虚函数。
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