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S_invlist_trim - don't SvPV_renew if SvLEN(invlist) is < PTRSIZE larger #23111

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S_invlist_trim - don't SvPV_renew if SvLEN(invlist) is < PTRSIZE larger #23111

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17 changes: 15 additions & 2 deletions regcomp_invlist.c
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Original file line number Diff line number Diff line change
Expand Up @@ -247,13 +247,26 @@ S_invlist_trim(SV* invlist)

/* But don't free up the space needed for the 0 UV that is always at the
* beginning of the list, nor the trailing NUL */
const UV min_size = TO_INTERNAL_SIZE(1) + 1;
const STRLEN want_size = MAX(
TO_INTERNAL_SIZE(1) + 1, /* minimum length needed */
SvCUR(invlist) + 1 /* SvCUR(invlist) can be 0,
* often is TO_INTERNAL_SIZE(1) or larger */
);

PERL_ARGS_ASSERT_INVLIST_TRIM;

assert(is_invlist(invlist));

SvPV_renew(invlist, MAX(min_size, SvCUR(invlist) + 1));
/* It's very common for SvLEN(invlist) to be equal to:
* TO_INTERNAL_SIZE(1) + 1
* SvCUR(invlist) + 2
* SvCUR(invlist) + "a few"
* In such cases there's zero or negligible benefit to
* calling SvPV_renew and thereby safesysrealloc().
* So check if that really seems warranted. */
if ( SvLEN(invlist) < want_size || SvLEN(invlist) > want_size + PTRSIZE ) {
SvPV_renew(invlist, want_size);
}
}

PERL_STATIC_INLINE void
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