On Fri, Feb 6, 2026 at 9:47 AM Tomasz Kaminski <[email protected]> wrote:
> > > On Thu, Feb 5, 2026 at 4:46 PM Jonathan Wakely <[email protected]> wrote: > >> 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. >> > Backported to gcc-15, after testing it on cfarm for x86_64-linux and > inspecting all emitted warnings. > Backported to gcc-14. Rebuilding and testing the patch on gcc-13.
