再次调用SDL"IMG_Load"会产生"EXC_BAD_ACCESS(code = EXC_I386_GPFLT)"

Question

我使用Xcode 8.3.3在MacOS 10.12上运行它,并通过Homebrew作为Dylibs安装SDL2.

下面是一些来自lazy foo的略微修改的示例代码.

我刚刚添加了第二个纹理gTexture2和功能loadMedia2,以便能够重现该问题.第二次IMG_Load执行它崩溃时出现以下消息:

EXC_BAD_ACCESS (code=EXC_I386_GPFLT)

搜索如何解决"一般保护错误"问题也没有让我更进一步,崩溃似乎发生在SDL内部.我可能真的误解了导致这个问题的事情,并且非常欢迎任何帮助.

真正令人困惑的是,它不会一直崩溃,只有3次中的2次.

崩溃似乎发生在里面SDL_AllocFormat_REAL ():

这是代码示例.

/*This source code copyrighted by Lazy Foo' Productions (2004-2015)
 and may not be redistributed without written permission.*/

//Using SDL, SDL_image, standard IO, and strings
#include <SDL.h>
#include <SDL_image.h>
#include <stdio.h>
#include <string>

//Screen dimension constants
const int SCREEN_WIDTH = 640;
const int SCREEN_HEIGHT = 480;

//Starts up SDL and creates window
bool init();

//Loads media
bool loadMedia();

//Frees media and shuts down SDL
void close();

//Loads individual image as texture
SDL_Texture* loadTexture( std::string path );

//The window we'll be rendering to
SDL_Window* gWindow = NULL;

//The window renderer
SDL_Renderer* gRenderer = NULL;

//Current displayed texture
SDL_Texture* gTexture = NULL;
SDL_Texture* gTexture2 = NULL;


bool init()
{
    //Initialization flag
    bool success = true;

    //Initialize SDL
    if( SDL_Init( SDL_INIT_VIDEO ) < 0 )
    {
        printf( "SDL could not initialize! SDL Error: %s\n", SDL_GetError() );
        success = false;
    }
    else
    {
        //Set texture filtering to linear
        if( !SDL_SetHint( SDL_HINT_RENDER_SCALE_QUALITY, "1" ) )
        {
            printf( "Warning: Linear texture filtering not enabled!" );
        }

        //Create window
        gWindow = SDL_CreateWindow( "SDL Tutorial", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN );
        if( gWindow == NULL )
        {
            printf( "Window could not be created! SDL Error: %s\n", SDL_GetError() );
            success = false;
        }
        else
        {
            //Create renderer for window
            gRenderer = SDL_CreateRenderer( gWindow, -1, SDL_RENDERER_ACCELERATED );
            if( gRenderer == NULL )
            {
                printf( "Renderer could not be created! SDL Error: %s\n", SDL_GetError() );
                success = false;
            }
            else
            {
                //Initialize renderer color
                SDL_SetRenderDrawColor( gRenderer, 0xFF, 0xFF, 0xFF, 0xFF );

                //Initialize PNG loading
                int imgFlags = IMG_INIT_PNG;
                if( !( IMG_Init( imgFlags ) & imgFlags ) )
                {
                    printf( "SDL_image could not initialize! SDL_image Error: %s\n", IMG_GetError() );
                    success = false;
                }
            }
        }
    }

    return success;
}

bool loadMedia()
{
    //Loading success flag
    bool success = true;

    //Load PNG texture
    gTexture = loadTexture( "../assets/player.png" );
    if( gTexture == NULL )
    {
        printf( "Failed to load texture image!\n" );
        success = false;
    }

    return success;
}

bool loadMedia2()
{
    //Loading success flag
    bool success = true;

    //Load PNG texture
    gTexture2 = loadTexture( "../assets/scene_main/background.png" );
    if( gTexture == NULL )
    {
        printf( "Failed to load texture image!\n" );
        success = false;
    }

    return success;
}

void close()
{
    //Free loaded image
    SDL_DestroyTexture( gTexture );
    SDL_DestroyTexture( gTexture2 );
    gTexture = NULL;
    gTexture2 = NULL;        

    //Destroy window
    SDL_DestroyRenderer( gRenderer );
    SDL_DestroyWindow( gWindow );
    gWindow = NULL;
    gRenderer = NULL;

    //Quit SDL subsystems
    IMG_Quit();
    SDL_Quit();
}

SDL_Texture* loadTexture( std::string path )
{
    //The final texture
    SDL_Texture* newTexture = NULL;

    //Load image at specified path
    SDL_Surface* loadedSurface = IMG_Load( path.c_str() );
    if( loadedSurface == NULL )
    {
        printf( "Unable to load image %s! SDL_image Error: %s\n", path.c_str(), IMG_GetError() );
    }
    else
    {
        //Create texture from surface pixels
        newTexture = SDL_CreateTextureFromSurface( gRenderer, loadedSurface );
        if( newTexture == NULL )
        {
            printf( "Unable to create texture from %s! SDL Error: %s\n", path.c_str(), SDL_GetError() );
        }

        //Get rid of old loaded surface
        SDL_FreeSurface( loadedSurface );
    }

    return newTexture;
}

int main( int argc, char* args[] )
{
    //Start up SDL and create window
    if( !init() )
    {
        printf( "Failed to initialize!\n" );
    }
    else
    {
        //Load media
        if( !loadMedia() || !loadMedia2() )
        {
            printf( "Failed to load media!\n" );
        }
        else
        {   
            //Main loop flag
            bool quit = false;

            //Event handler
            SDL_Event e;

            //While application is running
            while( !quit )
            {
                //Handle events on queue
                while( SDL_PollEvent( &e ) != 0 )
                {
                    //User requests quit
                    if( e.type == SDL_QUIT )
                    {
                        quit = true;
                    }
                }

                //Clear screen
                SDL_RenderClear( gRenderer );

                //Render texture to screen
                SDL_RenderCopy( gRenderer, gTexture, NULL, NULL );

                //Update screen
                SDL_RenderPresent( gRenderer );
            }
        }
    }

    //Free resources and close SDL
    close();

    return 0;
}   

小更新:

• 我在Windows上试过它,它运行得很好.所以我猜这个问题与MacOs有关.

• 我已经尝试重新安装所有库.

• 我正在使用C++ 14.

---

解决方案

那么它只有一半的解决方案更多的是解决方法.

感谢@Sahib Yar,他指出要尝试将图像放在同一目录中.这解决了这个问题.

但我认为这很奇怪,你应该能够从不同的目录或至少子目录加载资源.

最后一个问题

现在我真的很想解释为什么我们无法在MacOS上使用SDL从多个目录加载图像.这只是一个错误,已知的事情还是我犯了大错？

Answer 1

看来你没有破坏不需要的texture2.

SDL_DestroyTexture( gTexture );
SDL_DestroyTexture( gTexture2 );

gTexture = NULL;
gTexture2 = NULL;

在这个lazyfoo教程中,提到了

在我们的清理功能中,我们必须记住使用释放纹理SDL_DestroyTexture.

编辑1:

尝试将所有图像放在同一目录中.

编辑2:

这是不相关的目录中的MacOS从本教程中,这似乎是编译器做一些优化与std::string path为std::string是mutable.尝试清除std::string path函数末尾的对象以清除其对象保留的所有内存.

添加此行.

std::string().swap(path);

你的问题是一个悬垂的指针.EXC_BAD_ACCESS是你在解决访问权限范围之外的不存在的内存或内存的CPU呻吟.原因是缺乏对象的重新安置,导致早期释放,然后被覆盖.在那个时候(可能被延迟),指针将指向垃圾,其解除引用EXC_BAD_ACCESS将被抛出.

编辑3:

它与SDL2无关.在谷歌搜索之后,我发现在Xcode中,所有内容最终都被打包到一个目录中.我发现了很多关于此的问题.它可能与文件夹引用和组相关.我猜它可能是与蓝色文件夹有关的东西.如果是这种情况,您可以查阅此答案并相应地用于SDL.