Actually, to be concise, you're invoking undefined behavior. The Standard doesn't guarantee any execution order of operations in this context. The only thing which is guaranteed is, that the operation executed by erase() uses the initial value and afterwards start has been incremented (well, whatever happens if you increment an iterator after erasing the element it's pointing to).
I still disagree; start++ produces a side effect (std 1.9.7, emphasis mine):
"Accessing an object designated by a volatile lvalue (3.10), *modifying an object* [...] are all side effects, which are changes in the state of the execution environment.[...] At certain specified points in the execution sequence called sequence points, all side effects of previous evaluations shall be complete and no side effects of subsequent evaluations shall have taken place."
and as such, it must have taken place by the time the function erase is invoked (std 1.9.17):
"When calling a function (whether or not the function is inline), there is a sequence point after the evaluation of all function arguments (if any) which takes place before execution of any expressions or statements in the function body .[...]"
Ok, I'm wrong. But I remember at least one problem in the past I have had exactly because of this. But that just might have been a non-conforming compiler playing games on me. Thanks for the explanations. Regards Hartmut