15 replies to this topic

[storage]

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
	loaded = false;

	// Load bitmap into memory
	img = SDL_LoadBMP(filename);

	// Make sure bitmap was loaded successfully
	if (!img)
	{
		// Bitmap wasn't loaded, exit
		return 0;
	} else {
		// Bitmap was loaded, set loaded flag to true
		loaded = true;
	}

	// Bitmap was loaded successfully
	return 1;
}

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

[kingnosis]

First, I would check two things:

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

[storage]

Quote:

Original post by kingnosis First, I would check two things: Is img an SDL_Surface *? Is filename != NULL?

Thanks for your help! :)

Yep, img is an SDL_Surface *
Added filename != NULL

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;								
};

[Scyllinice]

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.

[Prototype]

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.

[storage]

Quote:

Original post by Prototype 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.

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!

[Drew_Benton]

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

[storage]

Quote:

Original post by Drew_Benton You have: Sprite *tile[4]; Which is an array of pointers to Sprites. You will either need to allocate new memory or use: [code=auto:0] Sprite tile[4]; ... tile[n].Load(temp.str().c_str()); [code=auto:0] - Drew

Thanks alot! :)

[Prototype]

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.

[storage]

Quote:

Original post by Prototype 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.

Thanks :)

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

[Prototype]

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).

[storage]

Quote:

Original post by Prototype 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).

Thanks thanks :)

[squashed_bug]

Your problem is:

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.