Question

I was reading a project's read me file and came across a sentence saying "The source code is 64-bit clean". What exactly do they mean by this?

Answer 1

Before the age of 64-bit hardware architecture people writing programs would assume things like "the length of a pointer is always equal or smaller than an int" and so they'd cast pointers to ints when they needed to pointer arithmetic etc. On 64-bit machines this is however not true, which can lead to a whole bunch of problems unless addressed properly (no pun intended). As result a few best practices or "rules" were established to make sure code is 64-bit clean.

Apple for example provides a guide in their dev-center to guide people towards safe 64-bit coding: https://developer.apple.com/library/mac/documentation/Darwin/Conceptual/64bitPorting/MakingCode64-BitClean/MakingCode64-BitClean.html