Comment by bellowsgulch
16 days ago
Compared to scripting languages with actual tagged types, C doesn't really have a type system, and that's readily apparent to anyone who has written C in the last 43 years and debugged a program written in it.
C pretends types exist with you, but once bytes hit the road, it's all real-life and segmentation faults.
C actually does have a type system and it's one of the bigger issues with the language. If it didn't, unaligned pointers and signed overflow would be totally fine.
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.
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?
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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.
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By that logic, no natively-compiled language has a type system.
Though I should note that in a way, even some ISAs have one, what with e.g. separate float vs integer registers.