Segmentation Fault? Researched... Couldn't Fix It.

no-reply@allegro.cc (Durnus) — Sat, 02 Dec 2006 11:41:05 +0000

Please ignore this thread. My problem is solved. (I re-wrote the code.)

After spending a long time on my code, I got a segmentation error. My ability isn't the best... but I want this to work.

My fault occurs not while compiling, but when I run the program. There is no problem with syntax or anything, my program just crashes.

If anyone could explain how to make it work, that would be great.

Here is my code. The class "particle_array" and all its functions are in the header file and another file.

The main file:

1#include 
2#include 
3#include 
4#include 
5#include 
6#include "TWOSheader.h"
7 
8 
9using namespace std;
10 
11 
12 
13bool alternate; //used for moving sand + water back and forth
14 
15int cursorsize = 3; //size of cursor
16 
17 
18 
19int falses; //DEGUGGING
20int trues;//DEBUGGING
21 
22const bool RIGHT = true;
23const int LEFT = false;
24 
25 
26 
27BITMAP *buffer; //The buffer.
28 
29int currentelement = 1; // Selected Element
30 
31void display_elements (int current)
32{
   rectfill(buffer,600,0,800,600,makecol(50,50,50));
   if(currentelement == 1)
   {
              textout_ex( buffer, font, "Wall", 605, 10, makecol( 0, 0, 0), makecol( 255, 255, 255) );
              textout_ex( buffer, font, "Sand", 605, 20, makecol( 200, 200, 200), makecol( 0,0,0) );
              textout_ex( buffer, font, "Water", 605, 30, makecol( 200, 200, 200), makecol( 0,0,0) );
              
40 
41 
   }
   if(currentelement == 2)
   {
              textout_ex( buffer, font, "Wall", 605, 10, makecol( 200, 200, 200), makecol( 0, 0, 0) );
              textout_ex( buffer, font, "Sand", 605, 20, makecol( 0, 0, 0), makecol( 255, 255, 255) );
              textout_ex( buffer, font, "Water", 605, 30, makecol( 200, 200, 200), makecol( 0,0,0) );
              
49 
   }
   if(currentelement == 3)
   {
              textout_ex( buffer, font, "Wall", 605, 10, makecol( 200, 200, 200), makecol( 0, 0, 0) );
              textout_ex( buffer, font, "Sand", 605, 20, makecol( 200, 200, 200), makecol( 0,0,0) );
              textout_ex( buffer, font, "Water", 605, 30, makecol( 0, 0, 0), makecol( 255,255,255) );
              
57 
   }
59}
60 
61 
62void interface_mouse(int xm, int ym)
63{
   if(ym > 10 && ym < 20)
   {
         currentelement = 1;
   }
   else if(ym > 20 && ym < 30)
   {
        currentelement = 2;
   }
   else if(ym > 30 && ym < 40)
   {
        currentelement = 3;
   }
76}
77 
78 
79 
80 
81int main(){

  allegro_init();
  install_keyboard();
  install_mouse();
  
  currentelement = 0;
  
  particle_array part; //A new particle array object.
  
  alternate = true;
92 
  buffer = create_bitmap(800,600);
  
  set_color_depth(8);
  set_gfx_mode( GFX_AUTODETECT_WINDOWED, 800, 600, 0, 0);
  
  set_window_title("Sandman's Dream");
  
  display_elements(1);
  
  
  
  show_mouse(buffer);
  
  while ( !key[KEY_ESC] )
  {
  
      clear_keybuf();
      
      rectfill(buffer,0,0,600,600,makecol(0,0,0));
      
      
      
      if(mouse_b & 1 && mouse_x < 600)
      {
                 
            for(int i = 0; i < cursorsize; i++)
            {
                    for(int j = 0; j < cursorsize; j++)
                    {
                            if((mouse_x/2)-j >= 0)
                            {
                                  part.particles[(int)floor(mouse_x/2)-j][(int)floor(mouse_y/2)-i][0] = currentelement;
                            }
                    }  
                    
            }
      }
      if(mouse_b & 1 && mouse_x > 600)
      {
               interface_mouse(mouse_x,mouse_y);
      }
      
      if(mouse_b & 2 && mouse_x <600)
      {
            for(int i = 0; i < 10; i++)
            {
                    for(int j = 0; j < 10; j++)
                    {
                            part.particles[(int)floor(mouse_x/2)-i+5][(int)floor(mouse_y/2)-j+5][0] = 0;
                    }
            }
            
      }
      if(key[KEY_1])
      {
             cursorsize = 3;
      }
      else if(key[KEY_2])
      {       
              cursorsize = 6;
      }
      else if(key[KEY_3])
      {       
              cursorsize = 10;
      }
      for(int i = 0; i < 300; i++)
      {
            for(int j = 0; j < 300; j++)
            {
                    if(part.particles[j]<i>[0]==1)
                    {
                             rectfill( buffer, j*2, i*2, j*2+1, i*2+1, makecol( 100, 100, 100));
                    }
            }
      }alternate = !alternate;
      
      part.update_particles();
      part.draw_particles(buffer);
      part.refreshmoved(); 
      
      if(mouse_x > 600)
      {
                 display_elements(currentelement);
      }
      
      
      
      draw_sprite(screen, buffer, 0, 0);
      
      
      
      rest(10);
      
      
187 
  }    
  
  return 0;
  
192}   
193END_OF_MAIN();

Spacing may be wierd, but it shouldn't be all that hard.

Thanks in advance for looking at my code.

no-reply@allegro.cc (kazzmir) — Sat, 02 Dec 2006 11:44:25 +0000

Im pretty lazy right now so I'm not gonna look through the whole thing, but I would suggest doing

buffer = create_bitmap(800,600);

after the call to set_gfx_mode.

no-reply@allegro.cc (Durnus) — Sat, 02 Dec 2006 11:53:13 +0000

Thanks for the quick response, I edited my code and recompiled, but it didn't fix the problem.

I've read somewhere that the debug will tell you the position of the bug, but I'm using Dev-Cpp and it won't tell me.

no-reply@allegro.cc (Kitty Cat) — Sat, 02 Dec 2006 11:54:43 +0000

And I wouldn't use show_mouse on anything other than the screen. Use
draw_sprite(buffer, mouse_sprite, mouse_x, mouse_y);
Right before blitting the buffer to the screen. And use blit to copy the buffer to the screen, not draw_sprite (unless you want the buffer to be masked, which you usually don't.

As for the crash.. check all return values. If a function can fail, check to make sure it doesn't.

no-reply@allegro.cc (Durnus) — Sat, 02 Dec 2006 12:01:57 +0000

Sorry... I'm not that good at debugging...

Checking return values? How do you do that, and what exactly does it accomplish?

I just found that when I make a break point in the code, it doesn't even get into the main part of the code. (The main function. )

no-reply@allegro.cc (Kitty Cat) — Sat, 02 Dec 2006 12:19:46 +0000

Quote:

Checking return values? How do you do that, and what exactly does it accomplish?

When the function returns, it'll give you back a value, assuming it doesn't return void. Like create_bitmap returns a BITMAP*. If that fails, the return value will be NULL. So you'd check:

buffer = create_bitmap(800,600);
if(buffer == NULL)
{
   allegro_message("Couldn't create bitmap!");
   exit(1);
}

If buffer isn't NULL, then it's a valid bitmap. Check Allegro's manual for what the other functions return for failure.

no-reply@allegro.cc (Three Harris) — Sat, 02 Dec 2006 12:50:53 +0000

could use a switch

no-reply@allegro.cc (Kris Asick) — Sat, 02 Dec 2006 15:14:13 +0000

I don't understand why you are using a three-dimensional array for your particles, but a segmentation fault could be indicative of illegal array access. Try commenting out the particle system and see if it runs, if so, then that's where your problem is and it probably has to do with going outside the array bounds.

--- Kris Asick (Gemini)
--- http://www.pixelships.com

no-reply@allegro.cc (Durnus) — Sat, 02 Dec 2006 20:09:02 +0000

@Kitty Cat:
Okay, I tried that, but the program doesn't get far enough along to execute the code.

@Three Harris:
I assume you mean I could use a switch in the interface display function. I'll do that, I guess it is more efficient.

@Kris Asick:
I tried disabling all the particle array stuff, and it still didn't work.

Nothing I'm trying is working... maybe something is wrong with my header file?

Header:

#SelectExpand
  1#ifndef TWOSSTUFF
  2#define TWOSSTUFF
  3
  4class particle_array
  5{
  6     public:
  7
  8void draw_particles(BITMAP *buffer);
  9void update_particle(int j, int i, bool alternate);
 10
 11void refreshmoved();
 12
 13void update_particles();
 14
 15int particles[400][400][3];
 16int particleselected[400][400];
 17};
 18#endif

Other file:

#SelectExpand
   1#include 
   2#include "TWOSheader.h"
   3#include 
   4#include 
   5
   6
   7
   8
   9
  10void particle_array::draw_particles(BITMAP *buffer)
  11{
   for(int i = 0; i < 300; i++)
   {
            for(int j = 0; j < 300; j++)
            {
                    if(particles[j]<i>[0]==1)
                    {
                             rectfill( buffer, j*2, i*2, j*2+1, i*2+1, makecol( 100, 100, 100));
                    }
                    if(particles[j]<i>[0]==2)
                    {
                             rectfill( buffer, j*2, i*2, j*2+1, i*2+1, makecol( 221, 190, 66));
                    }
                    if(particles[j]<i>[0]==3)
                    {
                             rectfill( buffer, j*2, i*2, j*2+1, i*2+1, makecol( 0, 0, 240));
                    }
            }
   }
  30}
  31void particle_array::refreshmoved()
  32{
   for(int i = 300; i > 0; i--)
   {
  35
            for(int j = 0; j < 300; j++)
            {
                    particles[j]<i>[1] = 0;
                    particleselected[j]<i> = 0;
                    
            }
    }
  43}
  44
  45
  46
  47void particle_array::update_particles()
  48{
   bool goagain = true;
   bool alternate = true;
   
   while(goagain == true);
   {
   alternate = !alternate;
   goagain = false;
        
   for(int j = 0; j < 300; j++)
   {
        for(int i = 300; i > 0; i--)
        {     
             if(particleselected[j]<i> != 1)
             {     
                  srand(time(0));
                  if(rand()%7 == 1)
                  {
                       particle_array::update_particle(j,i, alternate);
                       particleselected[j]<i> = 1;
                  }
                  else
                  {
                       goagain = true;
                  }
             }
        }
   }
   
   
   } 
   
  80}  
  81
  82void particle_array::update_particle(int j, int i, bool alternate)
  83{
                if(particles[j]<i>[1] != 1) // Has it moved?
                {
                    alternate = !alternate;
                    
                    
  89
                    if(particles[j]<i>[0]==2) // If the particle is Sand
                    {
                                          
                                          
                             if(particles[j][i+1][0] == 0)
                             {
                                      particles[j][i+1][0] = 2;
                                      particles[j]<i>[0] = 0;
                                      particles[j][i+1][1] = 1;
                             }
                                                         
                             else if(particles[j-1][i+1][0] == 0 && alternate == true)
                             {
                                if(j > 0)
                                {
                                      particles[j-1][i+1][0] = 2;
                                      particles[j]<i>[0] = 0;
                                      particles[j-1][i+1][1] = 1;
                                    }
                             }
                             else if(particles[j+1][i+1][0] == 0 && alternate == false)
                             {
                                if(j < 400)
                                {
                                      particles[j+1][i+1][0] = 2;
                                      particles[j]<i>[0] = 0;
                                      particles[j+1][i+1][1] = 1;
                                }
                             }
                             
                             
 121
                             else if(particles[j][i+1][0] == 3)
                             {
                                      particles[j][i+1][0] = 2;
                                      particles[j]<i>[0] = 3;
                                      particles[j][i+1][1] = 1;
                             }
                             
                             
                             else if(particles[j+1][i+1][0] == 3 && alternate == false)
                             {
                                      particles[j+1][i+1][0] = 2;
                                      particles[j]<i>[0] = 3;
                                      particles[j+1][i+1][1] = 1;
                             }
                             else if(particles[j-1][i+1][0] == 3 && alternate == false)
                             {
                                      particles[j-1][i+1][0] = 2;
                                      particles[j]<i>[0] = 3;
                                      particles[j-1][i+1][1] = 1;
                             }
                             
                             
                    }
                    else if(particles[j]<i>[0]==3) // If the particle is Water
                    {
                                          
                                         
                             if(particles[j][i+1][0] == 0)
                             {
                                      if(i < 400)
 152{
                                      particles[j][i+1][0] = 3;
                                      particles[j]<i>[0] = 0;
                                      particles[j][i+1][1] = 1;
 156}
                             }
                             else if(particles[j+1][i+1][0] == 0)
                             {
                                      if(j < 400 && alternate == false)
 161{
                                      particles[j+1][i+1][0] = 3;
                                      particles[j]<i>[0] = 0;
                                      particles[j+1][i+1][1] = 1;
 165}
 166
                             }
                             else if(particles[j-1][i+1][0] == 0)
                             {
                                      if(j > 0)
 171{
                                      particles[j-1][i+1][0] = 3;
                                      particles[j]<i>[0] = 0;
                                      particles[j-1][i+1][1] = 1;
 175}
                             }
                            
                              else if(particles[j+1]<i>[0] == 0 && particles[j-1]<i>[0] == 0)
                              {
                              
                                if(alternate)
                                {
 183
                                  if(j < 300)
                                  {                                             
                                            
                                      particles[j+1]<i>[0] = 3;
                                      particles[j]<i>[0] = 0;
                                      particles[j+1]<i>[1] = 1;
                                  }
                                      
                                }
                                if(!alternate)
                                {
 195
                                  if(j > 0)
                                  {                                             
                                            
                                            particles[j-1]<i>[0] = 3;
                                            particles[j]<i>[0] = 0;
                                            particles[j-1]<i>[1] = 1;
                                   
                                  }
                                }  
                              }
                              else if(particles[j+1]<i>[0] == 0)
                              {
 208
                                            if(j < 300)
 210{
                                      
                                            particles[j+1]<i>[0] = 3;
                                            particles[j]<i>[0] = 0;
                                            particles[j+1]<i>[1] = 1;
 215}
                                      
                                }
                                else if(particles[j-1]<i>[0] == 0)
                                {
 220
                                            if(j > 0)
 222{                                       
                                      
                                            particles[j-1]<i>[0] = 3;
                                            particles[j]<i>[0] = 0;
                                            particles[j-1]<i>[1] = 1;
                                   
 228}
                                 }  
                           
                            
                    }
             }
 234}

Yes, I know the spacing is all wrong.
I hope there is something wrong with my header file.

(Edit: )
Now I'm thinking of just re-writing this code... it's so disorganized and horrible looking. And maybe I'd get rid of that... interesting 3-d array. (And make it a 4 dimensional array! Mehehehe! Just kidding.)

no-reply@allegro.cc (CGamesPlay) — Sat, 02 Dec 2006 20:42:46 +0000

As a tip, remove the paramter from display_elements; you don't use it.

Comment out the particle_array part line, for me... That line causes your program to allocate 2.5 megabytes on the stack, which is probably the crash.

no-reply@allegro.cc (Durnus) — Sat, 02 Dec 2006 20:55:52 +0000

I just commented out all the particle stuff, but the error still happens...

I just commented out the header file, but the error still happens.

Trying to think of when the error started happening... It happened when I split the class into multiple files. That help?

(Edit)
Oh, thanks for the tip. Didn't realise I wasn't using it.

no-reply@allegro.cc (CGamesPlay) — Sat, 02 Dec 2006 21:08:10 +0000

Quote:

while(goagain == true);

Take off the semicolon, of course.

Quote:

srand(time(0));

Do this exactly 1 time at the beginning of your program, not several thousand times each second... it's just giving you the same random number for that whole second.

I ran your code, and it hung at that while loop. Then it hung someplace else. I commented out the particle code from the main function, and it crashed in the rectfill call. No, I don't know why.

But I actually got a window created. If you are still having the crash before set_gfx_mode, then you need to make sure you are actually rebuilding the code.

no-reply@allegro.cc (Durnus) — Sat, 02 Dec 2006 21:10:47 +0000

I'm rebuilding it every time. It does not crash at the set_gfx_mode, it crashes before the first thing I put in my main function.

...since it got so much further for you, I think I should reboot my computer or something.

Rebooted, still not working. I think I'm just going to re-write it.

(EDIT)
I started re-writing my code, but immediately ran into the error again.
I have cut down the cause to this: when I make a bitmap and set it equal to create_bitmap(800,600) it gives me the segmentation fault.

Here is the code:

1#include 
2#include "allegro.h"
3//My headers
4//#include "particlegrid.h"
5//using namespace particles;
6 
7int particles[300][300];
8bool particlemoved[300][300];
9 
10 
11 
12int main()
13{
14     BITMAP* buffer = create_bitmap(800,600);
15     
16     allegro_init();
17     install_keyboard();
18     install_mouse();
19    
20     set_color_depth(8);
21     set_gfx_mode( GFX_AUTODETECT_WINDOWED, 800, 600, 0, 0);
22     
23     
24     set_window_title("Sandman's Dream");
25     
26     while(!key[KEY_ESC])
27     {
28          
29          
30          
31          
32     }
33}
34END_OF_MAIN()

no-reply@allegro.cc (Kitty Cat) — Sat, 02 Dec 2006 22:27:44 +0000

You're trying to use an Allegro function before Allegro is initialized.

no-reply@allegro.cc (Durnus) — Sat, 02 Dec 2006 22:29:08 +0000

Oh jeez... I feel so stupid.

Okay, thanks.

no-reply@allegro.cc (Kris Asick) — Sun, 03 Dec 2006 05:08:21 +0000

One final tip. When something doesn't work, comment EVERYTHING in your main loop, then run the program. It should run fine since, well, nothing's happening! If it doesn't, your global variable initialization code is doing things it shouldn't. Then, start uncommenting sections one by one, compiling each time to see if it still runs or not. When it finally fails, then you have a better idea of what's causing an error like that.

Oh, and you don't need the semicolon on END_OF_MAIN().

--- Kris Asick (Gemini)
--- http://www.pixelships.com

no-reply@allegro.cc (Neil Walker) — Mon, 04 Dec 2006 04:41:38 +0000

And use an IDE with an integrated debugger

no-reply@allegro.cc (HoHo) — Mon, 04 Dec 2006 04:53:35 +0000

... or lots of printf()'s!

no-reply@allegro.cc (Durnus) — Mon, 04 Dec 2006 23:14:19 +0000

I am using Dev-C++.

A segmentation error IS NOT A COMPILE ERROR.

It is fixed now, please leave this thread to die.

no-reply@allegro.cc (BAF) — Tue, 05 Dec 2006 06:53:03 +0000

The only thing I saw related to compile error is the ; after END_OF_MAIN. The other tips about commenting stuff out were debugging tips.

1	#include
2	#include
3	#include
4	#include
5	#include
6	#include "TWOSheader.h"
7
8
9	using namespace std;
10
11
12
13	bool alternate; //used for moving sand + water back and forth
14
15	int cursorsize = 3; //size of cursor
16
17
18
19	int falses; //DEGUGGING
20	int trues;//DEBUGGING
21
22	const bool RIGHT = true;
23	const int LEFT = false;
24
25
26
27	BITMAP *buffer; //The buffer.
28
29	int currentelement = 1; // Selected Element
30
31	void display_elements (int current)
32	{
33	rectfill(buffer,600,0,800,600,makecol(50,50,50));
34	if(currentelement == 1)
35	{
36	textout_ex( buffer, font, "Wall", 605, 10, makecol( 0, 0, 0), makecol( 255, 255, 255) );
37	textout_ex( buffer, font, "Sand", 605, 20, makecol( 200, 200, 200), makecol( 0,0,0) );
38	textout_ex( buffer, font, "Water", 605, 30, makecol( 200, 200, 200), makecol( 0,0,0) );
39
40
41
42	}
43	if(currentelement == 2)
44	{
45	textout_ex( buffer, font, "Wall", 605, 10, makecol( 200, 200, 200), makecol( 0, 0, 0) );
46	textout_ex( buffer, font, "Sand", 605, 20, makecol( 0, 0, 0), makecol( 255, 255, 255) );
47	textout_ex( buffer, font, "Water", 605, 30, makecol( 200, 200, 200), makecol( 0,0,0) );
48
49
50	}
51	if(currentelement == 3)
52	{
53	textout_ex( buffer, font, "Wall", 605, 10, makecol( 200, 200, 200), makecol( 0, 0, 0) );
54	textout_ex( buffer, font, "Sand", 605, 20, makecol( 200, 200, 200), makecol( 0,0,0) );
55	textout_ex( buffer, font, "Water", 605, 30, makecol( 0, 0, 0), makecol( 255,255,255) );
56
57
58	}
59	}
60
61
62	void interface_mouse(int xm, int ym)
63	{
64	if(ym > 10 && ym < 20)
65	{
66	currentelement = 1;
67	}
68	else if(ym > 20 && ym < 30)
69	{
70	currentelement = 2;
71	}
72	else if(ym > 30 && ym < 40)
73	{
74	currentelement = 3;
75	}
76	}
77
78
79
80
81	int main(){
82
83	allegro_init();
84	install_keyboard();
85	install_mouse();
86
87	currentelement = 0;
88
89	particle_array part; //A new particle array object.
90
91	alternate = true;
92
93	buffer = create_bitmap(800,600);
94
95	set_color_depth(8);
96	set_gfx_mode( GFX_AUTODETECT_WINDOWED, 800, 600, 0, 0);
97
98	set_window_title("Sandman's Dream");
99
100	display_elements(1);
101
102
103
104	show_mouse(buffer);
105
106	while ( !key[KEY_ESC] )
107	{
108
109	clear_keybuf();
110
111	rectfill(buffer,0,0,600,600,makecol(0,0,0));
112
113
114
115	if(mouse_b & 1 && mouse_x < 600)
116	{
117
118	for(int i = 0; i < cursorsize; i++)
119	{
120	for(int j = 0; j < cursorsize; j++)
121	{
122	if((mouse_x/2)-j >= 0)
123	{
124	part.particles[(int)floor(mouse_x/2)-j][(int)floor(mouse_y/2)-i][0] = currentelement;
125	}
126	}
127
128	}
129	}
130	if(mouse_b & 1 && mouse_x > 600)
131	{
132	interface_mouse(mouse_x,mouse_y);
133	}
134
135	if(mouse_b & 2 && mouse_x <600)
136	{
137	for(int i = 0; i < 10; i++)
138	{
139	for(int j = 0; j < 10; j++)
140	{
141	part.particles[(int)floor(mouse_x/2)-i+5][(int)floor(mouse_y/2)-j+5][0] = 0;
142	}
143	}
144
145	}
146	if(key[KEY_1])
147	{
148	cursorsize = 3;
149	}
150	else if(key[KEY_2])
151	{
152	cursorsize = 6;
153	}
154	else if(key[KEY_3])
155	{
156	cursorsize = 10;
157	}
158	for(int i = 0; i < 300; i++)
159	{
160	for(int j = 0; j < 300; j++)
161	{
162	if(part.particles[j]<i>[0]==1)
163	{
164	rectfill( buffer, j2, i2, j2+1, i2+1, makecol( 100, 100, 100));
165	}
166	}
167	}alternate = !alternate;
168
169	part.update_particles();
170	part.draw_particles(buffer);
171	part.refreshmoved();
172
173	if(mouse_x > 600)
174	{
175	display_elements(currentelement);
176	}
177
178
179
180	draw_sprite(screen, buffer, 0, 0);
181
182
183
184	rest(10);
185
186
187
188	}
189
190	return 0;
191
192	}
193	END_OF_MAIN();

1	#include
2	#include "allegro.h"
3	//My headers
4	//#include "particlegrid.h"
5	//using namespace particles;
6
7	int particles[300][300];
8	bool particlemoved[300][300];
9
10
11
12	int main()
13	{
14	BITMAP* buffer = create_bitmap(800,600);
15
16	allegro_init();
17	install_keyboard();
18	install_mouse();
19
20	set_color_depth(8);
21	set_gfx_mode( GFX_AUTODETECT_WINDOWED, 800, 600, 0, 0);
22
23
24	set_window_title("Sandman's Dream");
25
26	while(!key[KEY_ESC])
27	{
28
29
30
31
32	}
33	}
34	END_OF_MAIN()