[rollcat]

An unexpected optimisation can introduce a side channel (most commonly timing). This one would be safe, but "how do you tell a compiler which ones [not] to use" is a whole topic by itself.

[Denvercoder9]

The C++ standard doesn't forbid introducing side channels, so the answer to the question is yes.

[rollcat]

With all the UB, I wonder how did we manage to write any secure or safety-critical code at all.

[konstantinua00]

this isn't UB, and any other language can do this optimization as well

even the one you cult over

[wat10000]

In C++? We pretty much did not.