[RESOLVED] Slight crashing problem with my Code.

[David2010]

Ok I know this MAY not be the correct spot to put this but it has to do with C++ and I am ALMOST positive its not an allegro library error.

Everything compiles perfectly but it crashes when it loads my convertme function.

Basically this program is designed to read a text file of values created from another program that says whether a pixel is black or white and then moves to the next pixel until the image is finished.

Well this interpritation program is supposed to take those 1 and 0 numbers and print it accordingly on a bitmap surface and then copy that temp bitmap surface onto the backbuffer and then copy the backbuffer onto the surface.

After doing code-breaks in my program I noticed that it runs fine until It loads my convertme function and then it crashes.

The code compiles fine so what am I doing wrong? :-/



<CODE>

#include <allegro.h>
#include <fstream>
#include <iostream>
#include <string>

using namespace std;

BITMAP *pic = NULL;

BITMAP *buffer = NULL;

BITMAP *pic2 = NULL;

volatile long speed_counter = 0;


void increment_speed_counter()

{

speed_counter++;

}

END_OF_FUNCTION(increment_speed_counter);

void shutdown()

{

destroy_bitmap(pic);
destroy_bitmap(buffer);
destroy_bitmap(pic2);

}

void convertme(string filename, int picWidth)

{

string line;

ifstream g;

g.open(filename.c_str());

int X = 0;

int Y = 0;

while (! g.eof() )

{

getline (g,line);

if (line == "0")

{
putpixel(pic2,X,Y, makecol( 255, 255, 255));
}

if (line == "1")

{
putpixel(pic2,X,Y, makecol( 0, 0, 0));
}

if (X == picWidth)

{
Y = Y + 1;
X = 0;
}

if (X < picWidth)

{
X = X + 1;
}


}

g.close();

}

int main(int argc, char *argv[])

{

int pic_x = 0;
int pic_y = 0;

allegro_init();
install_keyboard();
install_timer();

LOCK_VARIABLE(speed_counter);
LOCK_FUNCTION(increment_speed_counter);

install_int_ex(increment_speed_counter, BPS_TO_TIMER(60));

set_color_depth(16);
set_gfx_mode(GFX_AUTODETECT_WINDOWED, 200,200,0,0);

allegro_message("Attempting to Convert Text to Image!");

convertme("Test.txt",32);

draw_sprite(pic, pic2, pic_x, pic_y);

buffer = create_bitmap(200,200);



while(!key[KEY_ESC])

{

while(speed_counter > 0)

{

if(key[KEY_RIGHT])

{
pic_x ++;
}

else if(key[KEY_LEFT])
{
pic_x --;
}

else if(key[KEY_UP])

{
pic_y --;
}

else if(key[KEY_DOWN])

{
pic_y ++;
}

speed_counter --;

}

if(pic_x > 170)

{
pic_x --;
}

if(pic_x < 0)

{
pic_x ++;
}

if(pic_y > 165)

{
pic_y --;
}

if(pic_y < 0)

{
pic_y ++;
}




draw_sprite(buffer, pic, pic_x, pic_y);

blit(buffer, screen, 0,0,0,0,200,200);

clear_bitmap(buffer);

}

shutdown();

return(0);

}

END_OF_MAIN()


</CODE>

I am sure its something stupid on my end. :-/

Also I couldn't figure out how to use a code block on here.

[Lindley]

Well, the first thing I notice is this:

while (! g.eof() )
{
    getline (g,line);

For some reason, this approach seems to be common, but in practice it will often lead to off-by-1 errors. It's a lot safer to just do

while (getline(g, line))
{

Second, I notice that you're declaring pic and pic2 as global pointers, but I *don't* see where you're pointing them at anything valid before trying to use them. Am I just missing something?

[Paul McKenzie]

Everything compiles perfectly but it crashes

I see this statement many times from posters.

It doesn't really matter if the code compiles perfectly. All that means if the code compiles is that the code is syntactically correct. Whether it is logically correct, runs correctly, and produces the results you want is a totally different story.

Regards,

Paul McKenzie

[Raislin]

Also I couldn't figure out how to use a code block on here.

Forums typically use BBCODE style tags which are surrounded by square brackets [], not pointed ones <>.

So <code></code> should be [ code][ /code] (without the spaces).

[David2010]

Well, the first thing I notice is this:

Second, I notice that you're declaring pic and pic2 as global pointers, but I *don't* see where you're pointing them at anything valid before trying to use them. Am I just missing something?

Doy. Ok I removed pic2 completely and used pic in its place. :-?

I made them global so they could be accesed from my entire program including my convertme function.

I thought I pointed them to something...

I set "pic" to the correct pixel values...

[David2010]

I see this statement many times from posters.

It doesn't really matter if the code compiles perfectly. All that means if the code compiles is that the code is syntactically correct. Whether it is logically correct, runs correctly, and produces the results you want is a totally different story.

Regards,

Paul McKenzie

Is there any decent debugger for allegro or C++ so I could tell what was going on?

I tried setting breakpoints and popup messages to find information but it crashes during the convertme function. :-/

[David2010]

Forums typically use BBCODE style tags which are surrounded by square brackets [], not pointed ones <>.

So <code></code> should be [ code][ /code] (without the spaces).

Ahh. Cool. Thanks!

[David2010]

Ok after a little bit more debugging I found that this line of code in my convertme function is what is causing it to crash. Sadly though I don't know why. :-/

putpixel(pic,X,Y, makecol( 255, 255, 255));

[Lindley]

As far as I can see, the only thing you ever set pic to is NULL. You never direct the pointer to an actual BITMAP object.

[David2010]

Thanks I fixed it!

It was crashing because, as a previous user pointed out, I didn't set it to anything. (Sorry still learning).