usercalls in old Win32 game

Question

I am currently analyzing an old Win32 game from 1999 that was probably compiled with Visual C++ 6 and was programmed in C.

I noticed that there are almost no usercalls (i.e. calls that use registers to pass arguments) except for calls in the statically linked CRT library. Is this a reasonable assumption for a game of this age?

To identify registers used as function paramters I used an algorithm similar to the one described in this IDA blog post. The algorithm identifies PUSH/POP pairs and searches for registers usages before any assignment except in the PUSH/POP pairs.

Answer 1

Yes, this sounds perfectly normal. If the program did not use C++, you won't see thiscall with usage of ecx but just standard stdcall or cdecl which use only stack for passing arguments.