Branch: refs/heads/blead
Home: https://github.com/Perl/perl5
Commit: 08223ba8c819f556b4b6787bcdead768f200b00b
https://github.com/Perl/perl5/commit/08223ba8c819f556b4b6787bcdead768f200b00b
Author: Richard Leach <richardle...@users.noreply.github.com>
Date: 2024-11-12 (Tue, 12 Nov 2024)
Changed paths:
M pp.c
Log Message:
-----------
pp_reverse: don't COW buffer just to then un-COW it
When it has a single argument, scalar-mode `pp_reverse` copies the
source PV buffer to the destination PV buffer via the `sv_setsv()`
macro. This expands to:
sv_setsv_flags(dsv, ssv, SV_GMAGIC|SV_DO_COW_SVSETSV)
The `SV_DO_COW_SVSETSV` flag means that Perl_sv_setsv_flags will
try to achieve the "copy" via these mechanisms:
* Swipe the source buffer (if possible)
* COW the buffer (if possible)
* Copy the buffer
However, using COW makes no sense because pp_reverse is going to
then modify the buffer. Almost immediately after the `sv_setsv`
call, any COWing will be reversed by the call to `SvPV_force` and
a full copy of the buffer taken. So this commit expands the
`sv_setsv` call and drops the COW flag.
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