0xC0000005: Access violation writing location 0x00000004.

This topic is 4203 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

Recommended Posts

No, I am not that experienced in C++/SDL programming, but I've tried everything I can think of, but it doesn't seem to help. This is the error I get in VS .NET 2003:
Unhandled exception at 0x0040163f in Scarinum Client.exe: 0xC0000005: Access violation writing location 0x00000004.


And it occurs here:
int Sprite::Load(const char *filename)
{
// Make sure a filename was given
if (filename == NULL)
{
// No filename given, exit
return 0;
}

// Set loaded flag to false

// Make sure bitmap was loaded successfully
if (!img)
{
return 0;
} else {
}

return 1;
}


Any help is appreciated! [Edited by - storage on February 23, 2005 10:55:49 PM]

Share on other sites
First, I would check two things:

Is img an SDL_Surface *?
Is filename != NULL?

Share on other sites
Quote:
 Original post by kingnosisFirst, I would check two things:Is img an SDL_Surface *?Is filename != NULL?

Yep, img is an SDL_Surface *

Still same problem tho :(

sprite.h:
#include <SDL.h>	class Sprite{	public:		int Load(const char *filename);		int DrawSprite(SDL_Surface *img, int x, int y);		SDL_Surface *img;									bool loaded;								};

Share on other sites
Are you *sure* it occurs there?

Perhaps your sprite class isn't getting constructed correctly, or perhaps you're accessing it incorrectly.

I see nothing wrong with what you have posted. Perhaps it's elsewhere.

Share on other sites
You need to post more code I guess.
On a side note, returning 0 for failure is kinda non-standard and will confuse you when you are to use 3rd party libraries and such. Better get off that habit.

Share on other sites
Quote:
 Original post by PrototypeYou need to post more code I guess.On a side note, returning 0 for failure is kinda non-standard and will confuse you when you are to use 3rd party libraries and such. Better get off that habit.

Okay, thanks, mind telling me what to return? :)

This is all the code in my main.cpp that has something to do with the sprite class:
// Includes#include <SDL.h>#include <stdio.h>#include <sstream>#include "logging.h"#include "sprite.h"int main(int argc, char *argv[]){	Sprite *tile[4];		// ... logging, SDL initialization and such here ...	// Transparent color	alpha_r = 255;	// Red	alpha_g = 0;	// Green	alpha_b = 255;	// Blue		// Load tiles	for (int n = 0; n <= 4; n++)	{		std::stringstream temp;		temp << "data\\tiles\\" << n << ".bmp";		tile[n]->Load(temp.str().c_str());		// transparency		SDL_SetColorKey(tile[n]->img, SDL_SRCCOLORKEY, SDL_MapRGB(tile[n]->img->format, alpha_r, alpha_g, alpha_b));	}		// ... event handling and more logging etc ...}

Tell me if you need more :)

Thanks for all the help!

Share on other sites
You have:
Sprite *tile[4];

Which is an array of pointers to Sprites. You will either need to allocate new memory or use:

Sprite tile[4];...tile[n].Load(temp.str().c_str());

Once you do that, you should not be crashing anymore. Right now you are using NULL pointers, which is making your program do what it is doing.

- Drew

Share on other sites
Quote:
 Original post by Drew_BentonYou have:Sprite *tile[4];Which is an array of pointers to Sprites. You will either need to allocate new memory or use:Sprite tile[4];...tile[n].Load(temp.str().c_str());- Drew

Thanks alot! :)

Share on other sites
You create an array of 4 sprites, while you are trying to initialize 5:

Sprite *tile[4]; // only creates 4 elements [0..3]...for (int n = 0; n <= 4; n++) // tries to access tile[4]

So change n<=4 into n<4.

Share on other sites
Quote:
 Original post by PrototypeYou create an array of 4 sprites, while you are trying to initialize 5:Sprite *tile[4]; // only creates 4 elements [0..3]...for (int n = 0; n <= 4; n++) // tries to access tile[4]So change n<=4 into n<4.

Thanks :)

It works! :) Thanks everyone, for helping me and learning me about pointers and such :)

Share on other sites
Oh yeah, BTW, usually a function returns 0 for success, and any other value to denote an error (which you can conveniently put into an enum for readability).

Share on other sites
Quote:
 Original post by PrototypeOh yeah, BTW, usually a function returns 0 for success, and any other value to denote an error (which you can conveniently put into an enum for readability).

Thanks thanks :)

Share on other sites
It is perhaps worth noting the following point.

If you get an error such as: "Access violation writing location 0x00000000."
Then it usually means that you have dereferenced a NULL pointer.

However you got: "Access violation writing location 0x00000004."
When you get an error like this, with a small non-zero value, then
it often (but not always) means that your "this" pointer is NULL.

into the class Sprite as it follows a pointer (4 bytes) in the declaration.

So given the error message the first thing to do was to check the "this"
pointer in the debugger, or just read the code that called the function
and check whether the pointer could be NULL.

Martin

Share on other sites
Hi everyone, I think I have a similar problem with VS.NET 2003. I get
Unhandled exception at 0x0041821a in test.exe: 0xC0000005: Access violation writing location 0x004436ec.

message with this code:
#include <conio.h>#include <iostream>using namespace std;void revert(char *str){  char *last_ch = str;     while (*++last_ch)    //*pluspluslast_ch      ;                       --last_ch;              while (str < last_ch)    {                      		    char tmp;    tmp = *str;    *str++ = *last_ch;	//buggy line (*strplusplus)    *last_ch-- = tmp;  }	}int main(){  char *zaq = "abcdefgh";  cout<<zaq<<endl;  revert(zaq);	  cout<<endl<<zaq<<endl;    getch();  return 0;}

It comes from "Pointers on C" by Kenneth A. Reek (chapter 6, ex. 3). The function should put chars in reverse order in a given char array without using indices and local temp arrays (by using pointers only). I don't know what is wrong with this code - it comes from the spoiler at the end of the book :(

Share on other sites

char *zaq = "abcdefgh";

the fix:

char zaq[] = "abcdefgh";

zaq was pointing pointing to a memory address inside the text of your program, which cannot be changed.

Share on other sites
thx alot :) my mistake in main