If data structures weren’t working with MSVC, you’re probably working with non-portable code in the first place. Don’t assume an int is 32 bits long!
Oh absolutely! I was starting out during this time, and started using memcpy for a uni project, hardcoding byte sizes to what I assumed long’s size was, instead of checking or using standardized data types (because I didn’t even know they existed). The result was such a mess, exacerbated by the good ol “let’s write it all in one go and run it when we’re done”. Boy did I suffer in that class.