From: Laurence Withers <lwithers AT lwithers DOT demon DOT co DOT uk>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Allegro's draw_lit_sprite and draw_gouraud_sprite...
Date: Sun, 10 Jan 1999 17:51:22 +0000
Organization: IP
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--- Original Message ---
From: Malefactor <lslavoti AT mail DOT bcpl DOT net>
Time: Sat, 9 Jan 1999, 20:14:34

>   When I try to use draw_lit_sprite or draw_gouraud_sprite in my
>program it crashes with a page fault or general protection fault.
>RHIDE's Call Frame Traceback window refer's to either of the sprite
>drawing functions. I'm using Allegro v3.1. I made a small program
>using just the draw_lit_sprite function, and snipped it here incase I
>left something important out. If anyone has any suggestions I'd like
>to here them. Let me know if more info is needed.
[snip]

Are you checking the return values of the functions? The code you used
just assumes that everything works correctly; this may be because it's
just a condensed sample.

For instance:

int main(void)
{
    int result = 0;

    /* Attempt to initialise Allegro */
    result = allegro_init();
    if(result)
    {
        printf("Error initialising Allegro: %s\n", allegro_error);
        return result;
    }

    /* Attempt to set gfx mode */
    result = set_gfx_mode(...);
    if(result)
    {
        /* ... */
    }

    /* ... */
}

This way, the program fails with a useful error message anytime a call
to one of Allegro's functions fails. Note that you also need to check
that create_bitmap() and load_pcx() do not return NULL pointers, which
they do on failure.

HTH, and bye for now,
-- 
Laurence Withers, mailto:lwithers AT lwithers DOT demon DOT co DOT uk
Integrated Peripherals Operating System Project Leader || OPES Project
Projects' homepage is at: http://www.lwithers.demon.co.uk/       Leader