What is uintptr_t data type

Question

What is uintptr_t and what can it be used for?

Answer 1

Running the risk of getting another Necromancer badge, I would like to add one very good use for uintptr_t (or even intptr_t) and that is writing testable embedded code. I write mostly embedded code targeted at various arm and currently tensilica processors. These have various native bus width and the tensilica is actually a Harvard architecture with separate code and data buses that can be different widths. I use a test driven development style for much of my code which means I do unit tests for all the code units I write. Unit testing on actual target hardware is a hassle so I typically write everything on an Intel based PC either in Windows or Linux using Ceedling and GCC. That being said, a lot of embedded code involves bit twiddling and address manipulations. Most of my Intel machines are 64 bit. So if you are going to test address manipulation code you need a generalized object to do math on. Thus the uintptr_t give you a machine independent way of debugging your code before you try deploying to target hardware. Another issue is for the some machines or even memory models on some compilers, function pointers and data pointers are different widths. On those machines the compiler may not even allow casting between the two classes, but uintptr_t should be able to hold either. -- Edit -- Was pointed out by @chux, this is not part of the standard and functions are not objects in C. However it usually works and since many people don't even know about these types I usually leave a comment explaining the trickery. Other searches in SO on uintptr_t will provide further explanation. Also we do things in unit testing that we would never do in production because breaking things is good.