Some comments: - we have proposal for provenance rules (N2676), which would clarify the rules and make sure that pointer-integer roundtrips work (now broken on some compilers due to an "interesting" interpretation of provenance) Pointer-to-integer round trips could then be used to work around provenance-based optimizations if you need to (and fix existing code with those casts).
- for signed overflow, you can get run-time traps with the right compiler flags and this is IMHO far better than defined wrap-around for unsigned.
- C23 will get checked integer functions based on the GCC builtins
- you can get (relatively cheap) run-time bounds checking by using VLAs (some people think VLAs are generally bad, but pointers to VLAs are a bounded pointer type!)
There is of course much left to be done. But I like to stress that UB gives the compilers room to do what it wants. But this does not have to be optimization. If programmers do not like what they get, they need to complain to their vendors! The standard has to follow existing practice, so this has to be driven by the compiler vendors based on the feedback of their customers. So please, if you want to see changes, tell this to your compiler vendor and do not accept "we do this because the standard allows this" as an answer.