Problem with allegro_gl_flip(); http://www.allegro.cc/forums/view/591412 Allegro.cc Forum Thread matthew@allegro.cc (Matthew Leverton) Thu, 17 May 2007 04:10:42 +0000

I just compile Allegro 4.2.1 and AllegroGL 0.4.1 with mingw32 3.4.2. I'm using MSVC8 so I built them with the "fix msvc8" command. I built a debug version as well. Instead of generating agl.lib and agld.lib, it generated agl_s.lib and agld_s.lib. (static?) Anyway, I linked to those libraries and I tried running this example provided with AllegroGL.

1#include <allegro.h>
2#include <alleggl.h>
3 
4int main() {
5 
6 /* Initialize both Allegro and AllegroGL */
7 allegro_init();
8 install_allegro_gl();
9 
10 /* Tell Allegro we want to use the keyboard */
11 install_keyboard();
12 
13 /* Suggest a good screen mode for OpenGL */
14 allegro_gl_set(AGL_Z_DEPTH, 8);
15 allegro_gl_set(AGL_COLOR_DEPTH, 16);
16 allegro_gl_set(AGL_SUGGEST, AGL_Z_DEPTH | AGL_COLOR_DEPTH);
17 
18 /* Set the graphics mode */
19 set_gfx_mode(GFX_OPENGL_WINDOWED, 640, 480, 0, 0);
20 
21 /* Clear the screen */
22 glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
23 
24 /* Set up the view frustum */
25 glMatrixMode(GL_MODELVIEW);
26 glLoadIdentity();
27 glFrustum(-1.0, 1.0, -1.0, 1.0, 1, 60.0);
28 
29 /* Draw a quad using OpenGL */
30 glBegin(GL_QUADS);
31 glColor3ub(255, 255, 255);
32 glVertex3f(-1, -1, -2);
33 glVertex3f( 1, -1, -2);
34 glVertex3f( 1, 1, -2);
35 glVertex3f(-1, 1, -2);
36 glEnd();
37 
38 /* Flip the backbuffer on screen */
39 allegro_gl_flip();
40 
41 /* Wait for the user to press a key */
42 readkey();
43 
44 /* Finished. */
45 return 0;
46}
47END_OF_MAIN()

The application crashed when calling allegro_gl_flip(); I stepped into it and it goes there

void allegro_gl_flip(void)
{
  __allegro_gl_driver->flip();
}

where __allegro_gl_driver is NULL.

Any ideas?

Thanks!

]]> no-reply@allegro.cc (Sophat Pheng) Wed, 16 May 2007 11:04:00 +0000

Check all return values of functions that can fail. One of them is failing, but you're assuming they don't.

]]> no-reply@allegro.cc (Kitty Cat) Wed, 16 May 2007 11:35:09 +0000

As you said, this call fails.
install_allegro_gl();

It actually fails right from the start. 

int install_allegro_gl(void)
{
  if (!system_driver)
    return -1;
// ...

Why is that?

]]> no-reply@allegro.cc (Sophat Pheng) Wed, 16 May 2007 21:51:56 +0000

Do you have the latest OpenGL drivers installed on your machine?

]]> no-reply@allegro.cc (Richard Phipps) Wed, 16 May 2007 21:53:28 +0000

I think I have OpenGL driver Version 6.14.10.6347 that comes with my graphic card drivers. I don't think it is the latest but it should not be that old either. Should I get the latest?

]]> no-reply@allegro.cc (Sophat Pheng) Wed, 16 May 2007 22:23:57 +0000

Can you give us some details on your graphic card? Some gfx cards have no or poor OpenGL drivers. It is normally always a good idea to update to the latest drivers to improve poor ones..

]]> no-reply@allegro.cc (Richard Phipps) Wed, 16 May 2007 22:25:41 +0000

Sophat: I'd say that allegro_init(); also failed.

]]> no-reply@allegro.cc (Milan Mimica) Thu, 17 May 2007 00:40:15 +0000

I have a All-In-Wonder Radeon 9800 128MB.

Milan : Why would you say that ?

By the way, I can run the examples built with AllegroGL.

]]> no-reply@allegro.cc (Sophat Pheng) Thu, 17 May 2007 02:32:06 +0000

Because "system_driver" is a allegro variable initialized at allegro_init().
Strange that examples work.
Have you had any older version of allegrogl installed before? Maybe something is left and there are conflicts... just guessing.

]]> no-reply@allegro.cc (Milan Mimica) Thu, 17 May 2007 02:52:36 +0000

It is the first time I've built AllegroGL myself.

Also when I stepped into allegro_init();

"system_driver" was definitely and allegro_init() returns 0.

From my watch window :
system_driver 0x100d0de0 _system_directx {id=1146626080 name=0x100eb698 "" desc=0x100eb698 "" ...} SYSTEM_DRIVER *

I am getting very confuse.

Thanks for any inputs.

]]> no-reply@allegro.cc (Sophat Pheng) Thu, 17 May 2007 03:21:39 +0000

Hm, I used to see that when symbols from DLL where not imported correctly... But I can't see anything wrong here.
You can try building AllegroGL using MSVC8 project files. It's in projects/ directory.

edit: You are using Allegro as a DLL, right?

]]> no-reply@allegro.cc (Milan Mimica) Thu, 17 May 2007 04:05:12 +0000

Solved. You were right. I remove alld.lib from the dependencies.

Thanks a lot for your help and patience :)

]]> no-reply@allegro.cc (Sophat Pheng) Thu, 17 May 2007 04:10:42 +0000