If memory serves me right you wanted to use -Wall at the beginning but Windows.h was holding you back with a gratuitous amount of warnings. Now that the main game code is separated from the platform layer it seems like its plausible you could use it now. I added -Wall to the first two, had to suppress two warning types (wd4514 -wd4820), but it seems to have caught mostly signed/unsigned mismatch warnings.

The two supressed warnings in question can be found here. There were a few instances in the c standard library that set these off.

Warning output

Warning output without the two supressed warnings.