It is impossible to write C applications without invoking UB and your theory that UB behavior had no semantics is nonsensical. It may have no semantics that compilers currently feel they need to keep stable, but code that compiles and runs has semantics.

That's not what I (or the standard, or compiler writers, or programming language researchers) mean by "semantics."

From the perspective of defining and specifying a programming language, when we say "semantics" we mean the set of rules for an abstract machine, or a similar formalism. If those rules don't specify the result of an operation, it's like the machine gets stuck- like dividing by zero in a proof, there is no correct way to proceed. The behavior is undefined.

Nobody is disputing that compilers will produce something for code with undefined behavior. They're just saying that there is absolutely no useful way to rely on it, because nobody has agreed on or even decided what it should be (and always for some specific reason!)

If that makes it impossible to use the language, that's not UB's problem. It's the design of the language, and the quality of the tools that surround it. There are ways to increase your confidence that a C application never invokes UB, and they're getting better all the time. (There are also lots of new languages that try to solve this in various ways that C can't!)

Those are the solutions we have. "Just don't have UB in C" or "just make compilers more predictable" are not very effective by comparison.