But when you are programming in C, you are programming against the C abstract machine, not against an architecture or operating system. It's this machine that you are breaking when you invoke ub.
Passive voice! You expect C code to go beyond the territory of the abstract machine. The authors of the standard, quite clearly, do not.
I can see both of these arguments. I think there is a place in the world for a C that is machine-specific. But it's clearly not what the standard authors have in mind, there are clearly people who find the genericness of C useful (cf. "portable assembler"), and piecemeal solutions like skipping individual bad optimizations won't solve the underlying problem that there's no way in C to say "Dude, I'm writing for a reasonable UNIX on a reasonable modern machine with a single flat address space for code and data and non-exception-raising two's-complement arithmetic and the ability to do nonaligned reads/writes and other normal things, please stop thinking I might also be writing for a PDP-11 bootloader."
I think you should go to the standards committee with a single proposal, which is that C should stop trying to be portable to weird / old architectures (and people who need them can use weird / old compilers, anyway). Among other things, you can now enable certain types of optimizations if the compiler is permitted to assume that arithmetic is two's-complement and nonaligned reads/writes work and so forth.
One of the most popular architectures for "a reasonable UNIX on a reasonable modern machine with a single flat address space for code and data" is the x86, and on it, some nonaligned reads/writes do trap. Certain optimizations can be done only if the compiler is permitted to assume that the data is aligned.
That is 100% wrong.
>Strictly conforming programs are intended to be maximally portable among conforming implementations. Conforming programs may depend upon nonportable features of a conforming implementation.
The whole concept of "undefined behavior" is to cope with the reality that C programs routinely go beyond the bounds of the abstract machine.