Comment by flohofwoe
8 hours ago
> if two addresses are different ...
Eh, if the compiler knows that two addresses are different at compile time, it also knows how big the difference is.
8 hours ago
> if two addresses are different ...
Eh, if the compiler knows that two addresses are different at compile time, it also knows how big the difference is.
Usually this is not the case.
Indeed one of the fun LLVM bugs is that it can arrive at a situation in which it believes pointer A and pointer B are definitely not equal (weird given what's about to happen but OK that's potentially fine...) then we ask for their addresses† as integers X and Y, LLVM insists those integers aren't equal either because the pointers weren't (which as we're about to see is wrong) and then we subtract X - Y or Y - X and the answer either way is zero. Awkward. The integers were definitely equal.
† Although on a real modern CPU the pointer "is" just an address, notionally it has three components, the address, an address space (modern machines typically only have one) and a "provenance".