Infinite loop language lawyering

Compilers just apply rules that make assumptions and the assumptions they're allowed to make as per the standard are that signed integers won't overflow, dereferenced pointers are valid, empty loops don't count as a side effect, etc.

You *could* warn every time such an assumption is made. But this would mean a[i]++ emits at least five warnings (pointer validity (and it's many subtypes), alignment validity (and it's subtypes), index validity, overflow of each part in base+(index*stride), overflow of increment).

For a practical example, consider alignment. Many architectures require special or multiple, slower instructions to load unaligned values. By being able to assume all dereferenced pointers are sufficiently aligned, compilers can unconditionally emit the faster instructions instead. Since it is almost impossible to guarantee what the alignment will be (at minimum once you start calling out to foreign code like libc), this would mean warning on every pointer dereference in the entire program.

There is pretty much only one way to solve this, which is to make it impossible to get invalid pointers from valid ones and require some special operation or blessing to turn unknown pointers into valid ones. Which is why most languages seeking to avoid this situation have ended up with that.