Access violation reading location???

Ze_Dude

My program keeps crashing when I try to run it >:(

When I debugged it, it gave an error, Unhandled exception at 0x1002ff69 in shooter.exe: 0xC0000005: Access violation reading location 0x00000014.

The problem seems to be with the draw_bitmap function.

Call stack is as follows:

allegro-5.0.4-monolith-md-debug.dll!1002ff69()
[Frames below may be incorrect and/or missing, no symbols loaded for allegro-5.0.4-monolith-md-debug.dll]
allegro-5.0.4-monolith-md-debug.dll!10030004()
> shooter.exe!movement::drawimage(ALLEGRO_BITMAP * drawbmp) Line 74 + 0x28 bytes C++
shooter.exe!movement::moveleft() Line 106 C++
shooter.exe!main(int argc, char * * argv) Line 90 C++
shooter.exe!__tmainCRTStartup() Line 555 + 0x19 bytes C
shooter.exe!mainCRTStartup() Line 371 C
kernel32.dll!7c817077()

code is:

#SelectExpand
   1
   2//movement.cpp
   3#include "movement.h"
   4
   5#include <stdio.h>
   6
   7
   8
   9void movement::imageloadright() {// I've entered the filenames to load in this function, but I removed the filenames themselves here to make the whole thing smaller.
  10
  11
  12checkbitmap(); // checks if bitmaps are loaded
  13}
  14
  15void movement::imageloadleft() { // consult imageloadright
  16  
  17
  18  checkbitmap();
  19}
  20  void movement::setup() {
  21
  22    
  23      
  24       imageloadright();
  25       imageloadleft();
  26    
  27       
  28       al_clear_to_color(al_map_rgb(255, 255, 255));
  29       al_flip_display();
  30         
  31
  32         x = 150;
  33         y = 320;
  34
  35
  36}
  37  
  38  int movement::getX() {
  39  return x;
  40}
  41
  42  int movement::getY() {
  43  return y;
  44}
  45
  46  void movement::drawimage(ALLEGRO_BITMAP *drawbmp) {
  47    al_draw_bitmap(drawbmp, x, y, 0);
  48    al_flip_display();
  49  }
  50
  51  void movement::eraseimage() {
  52  al_clear_to_color(al_map_rgb(255, 255, 255));
  53}
  54
  55  void movement::moveright() {
  56      i = 0;
  57
  58  while (x <= 600  ) {
  59
  60      eraseimage();
  61      drawimage(bitmap[i]);
  62      x = x + 2;
  63      i++;
  64            
  65
  66
  67    }
  68  }
  69
  70
  71  void movement::moveleft() {
  72      i = 16;
  73
  74  while (x >= 5  ) {
  75
  76
  77      eraseimage();
  78      drawimage(bitmap[i]);
  79      x = x - 2;
  80      i++;
  81            
  82
  83
  84
  85  }
  86}
  87  
  88
  89void movement::destroybitmap() {
  90for (loop = 0;loop<= 31;loop++) {
  91 al_destroy_bitmap(bitmap[loop]);
  92   }
  93}
  94
  95void movement::checkbitmap() {//if one bitmap is loaded, chances are all of them are loaded if they are in the same folder and have similiar dimensions...right?
  96if (bitmap[0] = NULL) {
  97    fprintf(stderr, "failed to load bitmaps!\n");
  98    exit(-1);
  99
 100}
 101}

And the header file:

#SelectExpand
  1//movement.h
  2#ifndef MOVEMENT_H
  3#define MOVEMENT_H
  4
  5
  6#include <allegro5/allegro.h>
  7#include <allegro5/allegro_image.h>
  8
  9
 10
 11
 12class movement {
 13public:
 14
 15  void setup();
 16  void moveright();
 17  void moveleft();
 18  int getX();
 19  int getY();
 20  void imageloadleft();
 21  void imageloadright();
 22  void eraseimage();
 23  void drawimage(ALLEGRO_BITMAP *drawbmp);
 24  void destroybitmap();
 25  void checkbitmap();
 26
 27
 28
 29private:
 30  int i;
 31  ALLEGRO_BITMAP *bitmap[31] ;
 32  
 33
 34
 35
 36  int loop;
 37
 38  int x;
 39    int y;
 40  
 41
 42
 43};
 44
 45
 46#endif

I think the main file has nothing to do with this so I left it out.

Niunio

while (x >= 5  ) {
  eraseimage();
  drawimage(bitmap[i]);
  x = x - 2;
  i++;
}

The "bitmap[i]" isn't a correct pointer (i.e. it is NULL or not valid pointer). I suspect that there are less bitmaps in "bitmap" that you spect.

Check the value for "i" and for "bitmap[i]".

Ze_Dude

Thanks. It wasn't just about that, the increment operator could cause the value of i to go over 33 which caused it to crash because bitmap[34] didn't exist.

Neil Walker

Also, this:

while (x <= 600  ) {
  59
    eraseimage();
    drawimage(bitmap[i]);
    x = x + 2;
    i++;
          
  65
  66
  }
}

You only have 31 bitmaps but are tryign to draw 600.

Also, you are writing C++, move away from arrays for your storage and use something like std::vector.

Dizzy Egg

Even though you've got an 'A-HA' avatar, I have to point out that:

Neil Walker said:

but are tryign to draw 600.

is a shame because:

A) tryign

and

B) he adds 2 to x each iteration.

And that, is all.

EDIT:

I bet Neil says something about still being out of range....Neil?

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