DX is fully backward compatible. So if you have the DX9 package then DX9 and below will function properly. For Allegro 4 all you need is DX7 though. I don't believe having the latest DX installed affects the functioning or performance of libraries compiled with lower versions.

Thank you both for your replies. I don't remember where I got that d3d9.h file, at this point it's not in my includes folder. The make command is building Allegro so I suppose we'll see if it fails. That Allegro link I cited has downloads for the relevant SDK files for DX7 and DX8, but not DX9. I didn't spend a lot of time looking, but it seemed like those files would be buried inside some Windows development suite or something. What's the easiest way to get those DX9 files if they're actually needed?

Edit: It built Allegro just fine with the DX8 SDK files from the link.

It's not bloated if you use our version.

http://alleg.sourceforge.net/files/dx9mgw.zip

Thank you for the DX9 package, Edgar. But if it's not believed that it will make any difference in performance for Allegro 4 I don't know if I'll worry about it. That zip is about 9 times as large as the DX8 package.

One thing that I've noticed has been happening reliably today after building Allegro from scratch three times: When I get to the part where I call cmake, it stops itself and indicates there were errors, but if I issue the command again, it completes without complaint. Do I need to be suspicious of this or will it work fine?

Edit: I was wondering, the Allegro 4.x branch doesn't have any changelog content newer than 4.4.2. Were there any changes to that branch beyond that?

1. I'm not developing a game. It's an rhythm game chart editor so there much less incentive to port it to A5 since it doesn't demand for hardware acceleration.
2. I already said I don't have the time to do it right now, but it is planned for some future date.

I haven't encountered anything so problematic, Allegro 4 is more than stable enough for me for the immediate time being. And even one of the main things that bugged me (glitched ALT+Tab to bring program into foreground) was reportedly fixed in 4.4.2. Even on 4.4.1.1 I was able to program around issues like that.

I found the git change log and the changes between 4.4 and 4.9.0 don't seem too severe, is it worth trying to gradually update my application by testing compatibility with Allegro 4.9.0 first? Is it simple enough to have both Allegros built on my computer at once and switch them out (ie. changing header inclusions in my program) or should I count on having to remove Allegro 4.4 from my MinGW installation first?

As far as upgrading to 4.4.2, do I just build it from source and make-install it on top of my MinGW when it already has 4.4.1, or do I have to follow some process to remove the existing Allegro headers/binaries?

Those zips are nothing compared to the full DXSDK.

You can get build conflicts building allegro when it is already installed on your mingw, or at least I've seen it happen with Allegro 5 for some reason. It's a good idea to not install to your mingw directory, but perhaps a LIBS sub directory, that you link to with -Imingw\LIBS\include and -Lmingw\LIBS\bin.