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I started to like signed overflow rules, because it is really easy to find problems using sanitizers.

The strict aliasing rules are not violated by typical POSIX socket code as a cast to a different pointer type, i.e. `struct sockaddr` by itself is well-defined behavior. (and POSIX could of course just define something even if ISO C leaves it undefined, but I don't think this is needed here)

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> The strict aliasing rules are not violated by typical POSIX socket code as a cast to a different pointer type, i.e. `struct sockaddr` by itself is well-defined behavior.

Basically all usage of sendmsg() and recvmsg() with a static char[N] buffer is UB, is one big example I've run into. Unless you memcpy every value into and out of the buffer, which literally no one does. Also, reading sa_family from the output of accept() (or putting it into a struct sockaddr_storage and reading ss_family) is UB, unless you memcpy it out, which literally no one does.

Using a static char buffer would indeed UB but we just made the change to C2Y that this ok (and in practice it always was). Incorrect use of sockaddr_storage may lead to UB. But again, most socket code I see is actually correct.