https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80472
--- Comment #8 from Manuel López-Ibáñez <lopezibanez at gmail dot com> --- There is no negative n__ in user code. On Fri, 22 Mar 2019, 21:21 redi at gcc dot gnu.org, < gcc-bugzi...@gcc.gnu.org> wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80472 > > --- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> --- > A comment added to the code would make the caret diagnostic > self-explanatory: > > --- a/libstdc++-v3/include/bits/stl_iterator_base_funcs.h > +++ b/libstdc++-v3/include/bits/stl_iterator_base_funcs.h > @@ -149,7 +149,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER > // concept requirements > __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>) > __glibcxx_assert(__n >= 0); > - while (__n--) > + while (__n--) // if n is negative this has undefined behaviour > ++__i; > } > > That would make the diagnostic look like: > > /home/jwakely/gcc/9/include/c++/9.0.1/bits/stl_iterator_base_funcs.h:152:7: > warning: iteration 9223372036854775807 invokes undefined behavior > [-Waggressive-loop-optimizations] > 152 | while (__n--) // if n is negative this has undefined > behaviour > | > > > It's still a bug that there's no "In instantiation of ... required from ... > required from here" context shown though. > > -- > You are receiving this mail because: > You are on the CC list for the bug.
