On Wed, 28 Apr 2021 at 18:44, Hyman Rosen <hyrosen@mail.com> wrote:

"close off a class of correctness checking"

Except, of course, what happens is that when the compiler detects one of these uses of an invalidated pointer, it silently uses the undefined behavior permission to subvert the program and produce wrong results from the point of view of the programmer. That is, it opens up a new class of silent and deadly errors that would not be there without this pointer invalidation.

Another way to look at it is that by exhaustively testing your program with sanitizers enabled, you guarantee that it lacks a class of bugs and thus that it is safe and advantageous for the optimizer to transform your program accordingly.

I do have some sympathy for your point of view... but we need the optimizations.