Notably, the C standard does have an undefined behavior annex, Annex J.2, since C99. It's not mentioned in the post, and this omission in tandem with repeated usage of "C and C++" at various points might suggest otherwise to some people.
And C has a UB study group and we are working on a technical rapport that in great detail describes how UB works in C, and a comprehensive list of sample code for all known UB.
Thw C standard has a list of all known UBs. We don't know if the list is complete, because the C standard makes anything not defined by omission UB, so its possible to discover new UB. The language is however pretty thoroughly explored.
No. It would require listing not just every place the standard states undefined behavior is the result, but also every corner case not covered by the spec, or that is under-specified. It’s possible to document known instances, but never to document all possible sources of undefined or unspecified behavior.
