Makes sense to me. There's another one here: http://eel.is/c++draft/util.dynamic.safety#10

"Hence indirection through a pointer located there is undefined if the object it points to was created by global operator new and not previously declared reachable."

If the editors like this direction, I can do a more thorough pass through the standard and correct them all at once in a "big" patch. Or, I can correct them with individual patches.

I'm no editor, but I think that's a great idea, because there's also dubious stuff like (for valarray::min(), http://eel.is/c++draft/valarray.members#6):

The value returned for an array of length 0 is undefined.

This makes it sound like the undefinedness could be confined to the return value itself (so that other behavior would still be defined), but in reality, this is full-blown undefined behavior (libstd++ just gives an assertion failure). :)

Again, not an editor :)

Looking at 1.9p4 [intro.exection] we see that operations may be described as undefined, and the original wording is consistent with that form of specification. If you want to make a pass for more consistent usage of the term, I would start there - and make sure the standard remains consistent with that approach (so we don't editorially break something).

It seems like a lot of work, and I am only mildly in favor (but still in favor of you doing the work, not opposed ;))

Yeah, I see a lot of "the effect is undefined", and that seems fine. But "the value is undefined" sounds different to me.

Alisdair, you bring up a good point about 1.9p4 that kind of deflates this particular change. However, I still find the wording to be kind of obtuse, whereas "results in undefined behavior" is a bit easier to intuit for [expr.call], IMO.

I'll let the editors make the call -- if they like the new wording, great, and if they don't, feel free to close the pull request. :-)

@zygoloid: What do you think of Aaron's suggestion of a general wording review regarding how we say that the behaviour is undefined?

This change is good. If a general wording review would find more like this, that'd be nice too!