[Gibbon1]

Problems with unaligned pointers are basically a hardware defect. Signed overflow is an issue because academics are unhappy computers only can do finite math.

Issue with types and C is while the compiler knows about them the standards committees don't want you to be able to. If C had first class types more people would abandon C++ and that can't be allowed to happen.

[imtringued]

The concept of alignment isn't a hardware defect, maybe limitation, but the reason why alignment is a thing has to do with the fact that in chip interconnects transfer blocks. You cannot perform misaligned memory accesses against RAM.

A similar limitation exists when peforming accesses against the cache, but at a much finer granularity.

For bytes, the alignment restriction obviously exists in the 8 bit level. You have one output byte and 64 multiplexer inputs.

If you scale this up to 8 bytes, you will need a lot of 64 Input multiplexers.

But even if you can take the silicon area hit, there is the problem of crossing cache lines and pages.

In the end, you cannot divide memory into blocks and allow primitives to cross those blocks without requesting both blocks at the same time. That's an inefficient waste of resources so why support the wasteful usecase in the first place?

[Gibbon1]

With modern CPU's unaligned accesses only matter when it straddles a cache line address not a register address.

[AlotOfReading]

Unaligned pointers are undefined behavior even when the hardware fully supports unaligned access, because you're violating the type's rules.

To be honest, I've never seen much indication that the C and C++ committees are particularly fond of each other. They sometimes coordinate, but they're mostly content letting each other evolve in different directions. C is the way it is only after a long process of evolution away from the bits and bytes of BCPL into the strictly typed language we got from ASNI.

[Gibbon1]

Undefined behavior according to WG14 but perfectly fine on most architectures. Even on architectures that don't support it (what the fuck ARM cortex) the compilers do support it.

[AlotOfReading]

Yes, that's exactly the point I've been making. It's undefined today because C has a type system and that type system has this arbitrary rule, not because there are implementation constraints necessitating it (where it could just be implementation defined instead).