Thread: Access violation... can't figure it out...

  1. #1
    Registered User
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    Access violation... can't figure it out...

    I keep getting an access violation with my code in this function..
    Code:
    #include "stdafx.h"
    #include "CSprite.h"
    
    bool CSprite::LoadImage(const std::string &imgfile)
    {
        SDL_Surface* t_sfc = NULL;
        t_sfc = IMG_Load(imgfile.c_str());
        if ( t_sfc == NULL )
            return false;
        spriteSheet = SDL_DisplayFormat(t_sfc); //Access violation here
        SDL_FreeSurface(t_sfc);
        if ( spriteSheet == NULL )
            return false;
        return true;
    }
    this is the class definition...
    Code:
    #ifndef CSPRITE_H
    #define CSPRITE_H
    
    /* CSprite class definition */
    class CSprite
    {
    private:
        int x; int y;
        int direction;
        int xVel; int yVel;
    
        enum
        {
            UP = 0,
            DOWN = 1,
            LEFT = 2,
            RIGHT = 3
        };
        SDL_Surface* spriteSheet;
        std::vector<SDL_Rect> clips;
    public:
        CSprite();
        ~CSprite();
        
        bool LoadImage(const std::string& imgfile);
        void NewRect(int x, int y, int w, int h);
    
        void apply_surface(int x, int y, SDL_Surface* source, SDL_Surface* destination);
    };
    
    #endif
    I cant find the problem, but like always it will be something simple.
    The exact violation is
    Code:
    Unhandle exception at 0x68129410 in Varia_Engine.exe: 0xC0000005:
    Access violation reading location 0x00000013c.
    I am deeply thankful for any assistance. Hopefully I am clear enough.

  2. #2
    Officially An Architect brewbuck's Avatar
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    Apparently you are trying to invoke CSprite::LoadImage through a null pointer. Check the function which calls CSprite::LoadImage. Is it calling it through a pointer to a CSprite? Is this pointer NULL, possibly?

  3. #3
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    I tested it like this...
    Code:
    int main()
    {
      CSprite n;
      n.LoadImage("C:\\BSM.png"); //access violation.
    }
    I initialized spriteSheet to NULL in the constructor, but I thought you are suppose to NULL initialize pointers.

  4. #4
    Hurry Slowly vart's Avatar
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    Have you initialized SDL properly?
    Have you set the display flags correctly?
    All problems in computer science can be solved by another level of indirection,
    except for the problem of too many layers of indirection.
    – David J. Wheeler

  5. #5
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    yea I used SDL_Init(SDL_INIT_EVERYTHING) and it is successful. I can get the image to load into t_sfc, but it will not let me assign the optimized image to spriteSheet. In the debugger spriteSheet just stays NULL

  6. #6
    Unregistered User Yarin's Avatar
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    The file your reading is open maybe, have you tried reading in shared mode?

  7. #7
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    Are you sure that SDL_DisplayFormat(t_sfc) returns a pointer value? Maybe check to see if it's NULL?

  8. #8
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    Ah, yea SDL_DisplayFormat(t_sfc) is NULL, but why? I can't see why it would be.
    [EDIT]
    Thanks for the assistance. It was because I was initializing SDL in hardware memory, and my chipset is not valid for running that way. I had to switch to SWSURFACE. Thank again.
    [/EDIT]
    Last edited by Raigne; 10-11-2007 at 11:11 AM.

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