Thanks. Unfortunately, it seems SDL_sound is not compatible with the version of SDL2 that ships with Ubuntu 18.04:

/home/runner/work/gosu/gosu/dependencies/SDL_sound/SDL_sound_vorbis.c:64:13: warning: implicit declaration of function ‘SDL_exp’; did you mean ‘SDL_Log’? [-Wimplicit-function-declaration]
19
 #define exp SDL_exp

Maybe this can be fixed manually by providing a fallback for this function.

@jlnr I removed the offending #if !(defined(HAVE_LIBC) && defined(__WATCOMC__)) /* Watcom has issues... */ block which called the #def exp SDL_exp.

Looks like I also need to update the Visual Studio project... Good thing I got Windows booted on my main machine.

Thanks! How much manual tweaking was involved? Would it be possible to automate the updating process?

Although I hope that libsdl2-sound-dev (or so) will make its way into Ubuntu 22.04 so that we can just depend on it at some point.

I only needed to:

1. fetch the repo
2. nuke the contents of the /dependencies/SDL_sound directory
3. move the contents of repo's /src into the SDL_sound folder
4. remove the midi file and library folder
5. edit SDL_sound_internal.h to change #define SOUND_SUPPORTS_MIDI 1 to #define SOUND_SUPPORTS_MIDI 0 (looks like this step could be skipped by setting this via cmake)
6. Remove the offending #ifdef block for __WATCOMC__ that uses SDL 2.0.9 SDL_exp (this could also probably be simplified by setting HAVE_LIBC to 1 or __WATCOMC__ to 0 via cmake)