More madness.

This works:

1#include <stdio.h>
2#include <stdlib.h>
3#include <dos.h>
4#include <allegro.h>
5
6int errno;
7
8int main(){
9	int i;
10	
11	printf("Starting allegro\n");
12	i = install_allegro(SYSTEM_AUTODETECT, &errno, NULL);
13	if (i != 0){
14		printf("Error: Allegro library did not install!\n");
15		return(-1);	
16	} else {
17		printf("Ok!\n");	
18	}
19	
20	printf("Installing timer\n");
21	if (install_timer() == 0){
22		printf("Ok!\n");
23	} else {
24		printf("Error, Unable to setup Allegro system timers for input devices!\n");
25		return -1;
26	}
27	allegro_exit();
28	return 0;
29}

... but adding the install_timer() call after install_allegro() in my main() (rather than the very basic test main above) still results in the exe terminating abnormally.

It's literally the second thing I'm doing in my own main() section, the only things before it are the call to install_allegro, and a few logging statements.

There must be something else, some symbol, some global variable, or some other startup code that is present in some other part of my application which is causing install_timer to behave this way. I'm at a loss though - I'm not doing anything with timers or interrupts myself, and the only third party bits of code is Allegro itself, and the Judas audio library (which I temporary commented out and excluded from the linker).

Turning install_timer() off and then on at the start of my code: https://www.youtube.com/watch?v=fy3CDoJufqQ

Can you build the whole Allegro package with tools and examples? Surely there is one example in there using the timers.

OpenWatcom + Linux Cross-compile is not really a common platform for Allegro, I suppose... I use DJGPP on Windows XP x86, two separate setups. But neither of them are semi-modern DJGPP together with Allegro v4.
I do use Allegro 4, but only in its Windows version.

Yeah, I am coming round to the conclusion that I am going to have to start this from scratch with a complete source install of djgpp, Allegro and the rest, so that I know if anything is broken, it's down to me.

It's a shame having to install yet another cross compile toolchain for dos, as the Watcom stuff is brilliant for 16bit work.

I'll get djgpp installed and bodge the makefile around to get it to play nice with GCC/LD instead of WCC/wcl.

Ok, confirmed. Swapping out OpenWatcom with a GCC 12.x version of djgpp, and rebuilding the Allegro 4.2.3.1 library to use it (bear in mind anyone wanting to compile Allegro 4.x from source with a modern compiler - you need to add the -fgnu89-inline argument to the CFLAGS options in makefile.dj to support some of the inline code in the various Allegro header files [deprecated in C99 and later], and add two missing integer symbols in vbeaf.c for it to work - it has clearly bitrotted somewhat when it comes to compatability with modern toolchains).

No more abnormal termination when install_timer() is encountered in my code!

Sadly, it does mean moving to the use of cwsdpmi rather than the much neater (and seemingly leaner) dos32a.exe as the runtime support.

Moral of the story - don't use OpenWatcom for Allegro on DOS. You *can* use a later version of djgpp, but also be prepared to patch a few bugs when building it.

megatron-uk wrote on 2022-12-22, 22:26:

Ok, confirmed. Swapping out OpenWatcom with a GCC 12.x version of djgpp, and rebuilding the Allegro 4.2.3.1 library to use it (b […]
Show full quote

Ok, confirmed. Swapping out OpenWatcom with a GCC 12.x version of djgpp, and rebuilding the Allegro 4.2.3.1 library to use it (bear in mind anyone wanting to compile Allegro 4.x from source with a modern compiler - you need to add the -fgnu89-inline argument to the CFLAGS options in makefile.dj to support some of the inline code in the various Allegro header files [deprecated in C99 and later], and add two missing integer symbols in vbeaf.c for it to work - it has clearly bitrotted somewhat when it comes to compatability with modern toolchains).

No more abnormal termination when install_timer() is encountered in my code!

Sadly, it does mean moving to the use of cwsdpmi rather than the much neater (and seemingly leaner) dos32a.exe as the runtime support.

Moral of the story - don't use OpenWatcom for Allegro on DOS. You *can* use a later version of djgpp, but also be prepared to patch a few bugs when building it.

Good to hear that. And thanks for the tips there.

Be aware DJGPP might have timer issues with DOSBox.. it does some funky things to workaround DPMI interrupt handling limitations which aren't emulated correctly by DOSBox (segment limit checking).

One test is to run dosbox-x configured with normal core and segment limits active. It should log the segment limit events. If the segment limit checking is on cs/ds, then another option is to link against hdpmi, if possible, or test with djgpp_nearptr_enable.

Allegro and DJGPP are working nicely with each other, including interrupt timer based playback of the native Allegro midi support as well as my custom tracker music backend based on the Judas Audio library. Digital effect playback is next.

All working really well. Game isn't complete, but should have a video up shortly showing at least the loading/configuration and main story/navigation interface. Combat isn't quite done yet.