Welcome to the forum Zartox

And thanks for posting and answering posts.
There is a GM_PTR_SIZE_64 / 32 defined in the platform config files. This should use define _M_X64 (which I think has some portability beyond MSVC).
Whichever way, GM_PTR_SIZE_64 should be set in the platform config and should be used in the gmSystemLib.cpp instead of #if 1 / 0.
I recall the system lib being hacked to work on some 64bit platform (hence the #if 1) long before the whole project had a pass at 64bit compatibility (the GM_PTR_SIZE_64). The non-windows platform configs have not been updated in my build so they are from the time when everything was incorrectly typed as 'gmptr' which was an 'int'.
I'll try to clean some of this up soon in my build.