错误 LNK2019 未解析的外部符号 - 在一个 DLL 中调用多个类

如何解决错误 LNK2019 未解析的外部符号 - 在一个 DLL 中调用多个类

我有一个包含封装类的 DLL，我们称其为 A 类，它运行良好。现在我想在同一个 DLL 中添加另一个类； A 类调用 B 类。这会导致链接错误（但它们在同一个 DLL 中）。如果我删除 B 类，一切正常，这些类或函数都不会从 DLL 外部调用！！！

/******** DLL ********/


 #ifndef ENGD3D12_H
#define ENGD3D12_H
class cpuOP;

class EngD3D12 : public IRenderDevice,public RendererAttributes
{
public:
    EngD3D12(HINSTANCE hDll);
    ~EngD3D12(void);

cpuOP *cpuOP;



}
#endif
///////////////////////////////////////
CPP FILE
EngD3D12::EngD3D12(HINSTANCE hDLL) 
{
    cpuOP = new cpuOP(); // err
    cpuOP->GetcpuInfo();    //err
    this->m_hDLL = hDLL;
    m4xmsaaState = false;
    m4xmsaaQuality = 0;
    mCurrentBackBuffer = 0;
    mCurrentFence = 0;
    mBackBufferFormat = dxgi_FORMAT_R8G8B8A8_UnorM;
    mDepthStencilFormat = dxgi_FORMAT_D24_UnorM_S8_UINT;
    m_hFenceEvent = CreateEventExW(nullptr,false,EVENT_ALL_ACCESS);
}

//////////////////////////////////////////////
cpuOP.H
#ifndef cpuOP_H
#define cpuOP_H


 class cpuOP
{
    
    public :
        
        typedef struct cpuINFO_Type {
            bool bSSE;
            bool bSSE2;
            bool bSSE3;
            bool bSSSE3;
            bool bSSE4_2;
            bool bSSE4_1;
            bool bAVX;
            bool bOSEnabledAVX;
            bool b3DNow;
            bool bMMX;
            char name[48];
            bool bExt;
            bool bMmxex;
            bool b3DNowEx;
            char vendor[13];
            
        }  cpuINFO;
    cpuOP();
    ~cpuOP();
    cpuINFO GetcpuInfo();
    
    bool OSSupportSSEE();
    void GetcpuName(char*,int,const char*);
};
 
#endif

///////////////////////////////////////
//cpuOP.cpp
cpuOP::cpuOP()
{

}
cpuOP::cpuINFO cpuOP::GetcpuInfo()
{}
/******** DLL ********/

> Severity  Code    Description Project File    Line    Suppression State
> Error LNK2019 unresolved external symbol "public: __thiscall
> cpuOP::cpuOP(void)" (??0cpuOP@@QAE@XZ) referenced in function "public:
> __thiscall EngD3D12::EngD3D12(struct HINSTANCE__ *)" (??0EngD3D12@@QAE@PAUHINSTANCE__@@@Z)     Error  LNK2019 unresolved
> external symbol "public: struct cpuOP::cpuINFO_Type __thiscall
> cpuOP::GetcpuInfo(void)" (?GetcpuInfo@cpuOP@@QAE?AUcpuINFO_Type@1@XZ)
> referenced in function "public: __thiscall EngD3D12::EngD3D12(struct
> HINSTANCE__ *)" (??0EngD3D12@@QAE@PAUHINSTANCE__@@@Z)