I've spent some time on trying to find out why AGL needs a #define ALLEGRO_NO_ASM in order to work with C-only Allegro on Windows and now I reduced the problem to Allegro itself.
| 1 | #define ALLEGRO_USE_CONSOLE |
| 2 | #include <allegro.h> |
| 3 | #include <stdio.h> |
| 4 | |
| 5 | int main() |
| 6 | { |
| 7 | BITMAP *bmp; |
| 8 | int pix; |
| 9 | |
| 10 | allegro_init(); |
| 11 | install_keyboard(); |
| 12 | install_timer(); |
| 13 | |
| 14 | set_color_depth(32); |
| 15 | set_gfx_mode(GFX_DIRECTX_WIN, 800, 600, 0, 0); |
| 16 | |
| 17 | bmp = create_bitmap(200, 200); |
| 18 | clear_to_color(bmp, makecol(255, 0, 0)); |
| 19 | pix = _getpixel32(bmp, 20, 20); |
| 20 | printf("%i\n", pix); |
| 21 | |
| 22 | pix = getpixel(bmp, 20, 20); |
| 23 | printf("%i\n", pix); |
| 24 | |
| 25 | readkey(); |
| 26 | |
| 27 | return 0; |
| 28 | } |
| 29 | END_OF_MAIN() |
This code does not work with C-only Allegro in Release mode. It crashes on _getpixel32() and I think I know why.
_getpixel32() is a inline function, defined in allegro headers, and it depends on ALLEGRO_NO_ASM being defined. End-user programs do not (don't have to and cannot know whether they have to) define ALLEGRO_NO_ASM, which makes the compiler use ASM version of _getpixel32, which does some nasty things...
The problem doesn't show in debug mode because function inlining is disabled, so this is more like a theory and I cannot prove this using a debuger.
If you place #define ALLEGRO_NO_ASM before #include <allegro.h>, it works.
It doesn't crash on getpixel() because it isn't inlined.
edit:edit: apparently, it's MSVC specific, works in mingw
edit: To be more specific, it's a matter of which definition (ASM or C) of bmp_[read|write|unread]_line() is inlined inside _[get|put]_pixel().