On 23/05/2023 03.34, Andrew Tomazos via Liaison wrote:
...
> Is it correct to say that a statement of the form "The implementation may assume X", implies that if X is false, the program has undefined behavior?
>
> If so, the condition X may not contain any reference to an undefined operation, such as [intro.progress]/1 does not:
>
> "The implementation may assume that any thread will eventually [snip]"
>
> Thus it is not rendered undefined behavior via [intro.abstract]/4,
[intro.abstract] p4 is the root of the "undefined behavior" specification in C++.
I agree the phrasing "operation" is not stellar with respect to stuff such as
non-terminating loops or data races (improvement suggestions welcome), but the
intent is that it applies to all kinds of undefined behavior that are mentioned
in the rest of the standard.
I wished we had explicitly called it "undefined behavior". I don't think there is
another interpretation of that statement that makes sense, and it was certainly
my intent that it be undefined behavior, but the wording is confusing.
Hans
Jens