On Thu, 5 Feb 2026 at 15:30, Tomasz Kaminski <[email protected]> wrote: > > > > On Tue, Aug 26, 2025 at 5:47 PM Jonathan Wakely <[email protected]> wrote: >> >> On Tue, 26 Aug 2025 at 16:29, Tomasz Kamiński <[email protected]> wrote: >> > >> > This patch introduces a new function, _M_fill_append, which is invoked when >> > copies of the same value are appended to the end of a vector. Unlike >> > _M_fill_insert(end(), n, v), _M_fill_append never permute elements in >> > place, >> > so it does not require: >> > * vector element type to be assignable; >> > * a copy of the inserted value, in the case where it points to an >> > element of the vector. >> > >> > vector::resize(n, v) now uses _M_fill_append, fixing the non-conformance >> > where >> > element types were required to be assignable. >> > >> > In addition, _M_fill_insert(end(), n, v) now delegates to _M_fill_append, >> > which >> > eliminates an unnecessary copy of v when the existing capacity is used. >> > >> > PR libstdc++/90192 >> > >> > libstdc++-v3/ChangeLog: >> > >> > * include/bits/stl_vector.h (vector<T>::_M_fill_append): Declare. >> > (vector<T>::fill): Use _M_fill_append instead of _M_fill_insert. >> > * include/bits/vector.tcc (vector<T>::_M_fill_append): Define >> > (vector<T>::_M_fill_insert): Delegate to _M_fill_append when >> > elements are appended. >> > * testsuite/23_containers/vector/modifiers/moveable.cc: Updated >> > copycount for inserting at the end (appending). >> > * testsuite/23_containers/vector/modifiers/resize.cc: New test. >> > * testsuite/backward/hash_set/check_construct_destroy.cc: Updated >> > copycount, the hash_set constructor uses insert to fill buckets >> > with nullptrs. >> > --- >> > v2 modifies additional test case, that I must have missed. >> > hash_set uses insert to append elements, which no longer creates copy. >> > >> > OK for trunk? >> >> OK > > This is now on trunk for 6mo, and no regression was reported, so I think it is > time to backport it, as I have fresh builds. Up to GCC 13?
OK for 15, 14 and 13. It's not a regression (checked back to 4.0.4 on Compiler Explorer) but it is a non-conformance bug with a few duplicate reports, and the fix isn't complicated. My only concern is causing new false-positive middle-end warnings about buffer overflows. Please check the test results carefully, especially on gcc-13 and gcc-14 which didn't have -fassume-sane-operator-new-delete yet.
