c++ - 错误 LNK2019 : unresolved external symbol error

Question

我收到这些错误消息

2>main.obj : error LNK2019: unresolved external symbol "public: __thiscall CEngine::CEngine(void)" (??0CEngine@@QAE@XZ) referenced in function _WinMain@16

2>main.obj : error LNK2019: unresolved external symbol "public: void __thiscall CEngine::SetWindowSize(int,int,char const *,int)" (?SetWindowSize@CEngine@@QAEXHHPBDH@Z) referenced in function _WinMain@16

2>main.obj : error LNK2019: unresolved external symbol "public: void __thiscall CEngine::Begin(void)" (?Begin@CEngine@@QAEXXZ) referenced in function _WinMain@16

2>main.obj : error LNK2019: unresolved external symbol "public: int __thiscall CEngine::GetDisplayWidth(void)" (?GetDisplayWidth@CEngine@@QAEHXZ) referenced in function _WinMain@16

2>main.obj : error LNK2019: unresolved external symbol "public: int __thiscall CEngine::GetDisplayHeight(void)" (?GetDisplayHeight@CEngine@@QAEHXZ) referenced in function _WinMain@16

2>C:\Users\ethan\Desktop\C++ Projects\delveenginetest\Debug\delveenginetest.exe : fatal error LNK1120: 5 unresolved externals

这是我的解决方案:

Solution 'delveenginetest' (2 projects)

DelveEngine

Include

delve.h

Engine.h

SetupSDL.h

stdafx.h

引擎.cpp

main.cpp

设置SDL.cpp

这是Engine.h

的代码

#pragma once
#include "SetupSDL.h"

class CEngine
{
public:
    CEngine(void);
    ~CEngine(void);

    void SetWindowSize(int winW, int winH, const char* GameName, int windowMode);
    void Begin(void);

    int GetDisplayWidth(void);
    int GetDisplayHeight(void);
private:
    int deskW;
    int deskH;

    bool playing;
    CSetupSDL* sdl_setup;
};

Engine.cpp的代码

#include "Include/stdafx.h"
#include "Include/Engine.h"

CEngine::CEngine(void)
{
    playing = true;

    deskW = GetSystemMetrics(SM_CXSCREEN);
    deskH = GetSystemMetrics(SM_CYSCREEN);
}


CEngine::~CEngine(void)
{
}

void CEngine::SetWindowSize(int winW, int winH, const char* GameName, int windowMode)
{
    // set up SDL for use
    sdl_setup = new CSetupSDL(winW, winH, GameName, windowMode);
}

void CEngine::Begin(void)
{
    while (playing && sdl_setup->GetMainEvent()->type != SDL_QUIT)
    {
        sdl_setup->Begin();
        sdl_setup->End();
    }

    playing = false;
}

int CEngine::GetDisplayWidth(void){ return deskW; }
int CEngine::GetDisplayHeight(void){ return deskH; }

DelveEngine 项目构建成功，而 delveenginetest 项目失败。

怎么了？我找遍了一个原因，找不到适合我的。

Answer 1

尽管您没有提供所有足够的信息来正确诊断您的问题，但我会尝试分享我认为可能是链接器错误的原因:

1. 我想您提到的项目 delveenginetest 是为了为 DelveEngine 项目中的类设置单元测试。
2. 由于您的 DelveEngine 项目中有一个 Main.cpp，我猜它只是作为可执行文件构建(成功)。
3. 您的 delveenginetest 需要链接到 DelveEngine 项目提供的类，但这实际上是不可能的，因为 .exe 来自 DelveEngine 不能用于链接，您需要一个库将其导入另一个可执行文件(单元测​​试框架)。

我建议将你的类/源文件从 DelveEngine 项目中分离出来，组成一个静态或共享库，它可以从一个应用程序和测试框架中同时链接到一个单一的VS解决方案:

Solution 'DelveEngine' (3 projects)  
   DelveEngineLib (project [.lib/.dll])
      Include  
         delve.h   
         Engine.h   
         SetupSDL.h   
      Engine.cpp
      SetupSDL.cpp
   DelveEngine (project [.exe])
      Main.cpp
   delveenginetest (project [.exe])
      Main.cpp (TestFramework main definition)

因为我不是很精通它，所以我实际上不知道 VS 2013 是否支持设置消耗虚拟 资源的项目(想想实际构建环境中的源链接)，但是这可能是无需额外库即可设置应用程序和单元测试的替代方法。