> I guess that the regular long type is not sufficient on all systems
> supported by Hatari if I need a 64 bit data type?
No it isnt. plain "long" on Windows e.g. is 32 bit, even on 64-bit systems. There might also other be 32-bit targets (Arm maybe? not sure).. Another thing to note is that "long long" is not supported by older MSVC versions (just in case somebody uses it).
Btw. if you need a type that is *exactly* 64bit, you should consider using stdint.h and int64_t/uint64_t instead,