未解决的外部引用。

Question

未解决的外部引用。

7

我有一个未解决的外部符号错误，让我非常苦恼。简而言之，我有一个SDL_Surfaces的包装类（“DgSurface”）和一个用于加载和存储DgSurfaces的类（“DgSurfaceList”）。当尝试将DgSurfaceList文件包含在我的项目中时，链接问题就会出现。以下是我的类：

头文件“DgSurface.h”包含了DgSurface类的声明：

    #ifndef DGSURFACE_H
    #define DGSURFACE_H

    #include "SDL.h"
    #include <string>

    class DgSurface
    {
    public:

        //Constructor/destructor
        DgSurface(std::string N, SDL_Surface* I): image(I), name(N) {}
        DgSurface() {name = ""; image = NULL;}
        ~DgSurface();

        //Copy operations
        DgSurface(const DgSurface&);
        DgSurface& operator= (const DgSurface&);

        //Data members
        std::string name;       //The name of the image
        SDL_Surface* image;     //The image
    };

    #endif

Cpp文件"DgSurface.cpp"包含DgSurface的定义：

#include "DgSurface.h"
#include "SDL.h"

//--------------------------------------------------------------------------------
//        Constructor
//--------------------------------------------------------------------------------
DgSurface::DgSurface(const DgSurface& other)
{
    //Copy name
    name = other.name;

    //Create new SDL_Surface 
    image = SDL_ConvertSurface(other.image, other.image->format, 0);
}


//--------------------------------------------------------------------------------
//        Destructor
//--------------------------------------------------------------------------------
DgSurface::~DgSurface()
{
    SDL_FreeSurface(image);
}


//--------------------------------------------------------------------------------
//        Assignment operator
//--------------------------------------------------------------------------------
DgSurface& DgSurface::operator= (const DgSurface& other)
{
    // if same object
    if ( this == &other )
        return *this;

    //Copy name
    name = other.name;

    //Create new SDL_Surface 
    image = SDL_ConvertSurface(other.image, other.image->format, 0);

    return *this;
}

这个类似乎运行良好，并且表现如预期（然而，一如既往地，我愿意接受反馈 :)。

"DgSurfaceList.h" 包含 DgSurfaceList 类的声明：

#ifndef DGSURFACELIST_H
#define DGSURFACELIST_H

#include "SDL.h"
#include <list>
#include <string>
#include "DgSurface.h"


class DgSurfaceList
{
    public:
        //Constructors/destructor
        DgSurfaceList() {}
        ~DgSurfaceList() {}

        //Functions
        bool AddImage(std::string location, std::string name);

        //Return Functions
        SDL_Surface* GetImage(std::string S) const;

    private:
        //Data members
        std::list<DgSurface> imlist;    //The list of DgSurfaces

        //Functions
        SDL_Surface* LoadImage( std::string filename );
};


#endif

最后，“DgSurfaceList.cpp” 包含了 DgSurfaceList 的定义：

#include "SDL.h"
#include "SDL_image.h"
#include <list>
#include <string>
#include "DgSurface.h"
#include "DgSurfaceList.h"


//--------------------------------------------------------------------------------
//      Load an image from file
//--------------------------------------------------------------------------------
SDL_Surface* DgSurfaceList::LoadImage( std::string filename )
{
    //Loads an image from file, returns SDL_surface*
    ...

}   //End:DgSurfaceList::LoadImage()


//--------------------------------------------------------------------------------
//      Add a DgSurface to the list
//--------------------------------------------------------------------------------
bool DgSurfaceList::AddImage(std::string location, std::string name) 
{
    //Load the image
    DgSurface temp(name,LoadImage(location));

    //If there was an error in loading the image
    if( temp.image == NULL )
        return false;

    //If everything loaded fine, place a copy into imlist
    imlist.push_back(temp);

    return true;

}   //End: DgSurfaceList::AddImage();


//--------------------------------------------------------------------------------
//      Searches imlist for an image, returns a pointer to a SDL_Surface
//--------------------------------------------------------------------------------
SDL_Surface* DgSurfaceList::GetImage(std::string S) const
{
    std::list<DgSurface>::const_iterator i;

    //Search imlist for DgSurface of the same name
    for (i = imlist.begin(); i != imlist.end(); i++)
    {
        if (S.compare((*i).name) == 0)
            return (*i).image;
    }

    //Return Null if name not found
    return NULL;

}   //End:DgSurfaceList::GetImage()

现在，如果我在cpp文件中注释掉DgSurfaceList :: GetImage（）定义，则DgSurfaceList似乎可以正常工作并正确存储图像。更具体地说，仅当我在上述函数中包含for循环时才会出现链接错误。可能是什么原因？

其他信息：

错误：

unresolved external symbol __imp___CrtDbgReportW referenced in function "public: class 
DgSurface const & __thiscall std::_List_const_iterator<class std::_List_val<class 
DgSurface,class std::allocator<class DgSurface> > >::operator*(void)const "

编程环境： Visual C++ Express 2010

- Frank

1个回答

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原文链接

- jahhaj · Accepted Answer

CrtDbgReport仅在C运行时库的调试版本中定义。因此，您可能正在以调试模式进行编译，但链接到库的发布版本。另一个可能性是您正在以发布模式进行编译，但某些宏定义导致编译std::list的调试版本。