I am the author of the open-source Dynace. This is an OO extension to C. It has been in production use for around 20 years. It has been used on DOS, all Windows, Linux, macOS/Intel, VMS, PLAN9, COSMIC, SUNOS, etc. all without a problem. However it does not run on Apple M1, M2 machines. I traced the problem to variadic function calls. I am creating a va_list in a ... function. I then pass the va_list to a second function. I wrote something to copy the the va_list (via va_copy) to see what I am getting. The first function works okay. But the second function does not. (I know you can't re-use a va_list.) I have spend a couple of days on this and can't find a problem with my code. I tried creating a simple example but it worked. Apparently the problem is situational. Anyway, I have no idea what is wrong or what to do next. I'd sure appreciate any help! Thanks!