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SvPV_shrink_to_cur: include space for COW #23290

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SvPV_shrink_to_cur: include space for COW #23290

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5e2b259
SvPV_shrink_to_cur: don't be unrealistic, do include space for COW
richardleach May 15, 2025
5234f32
Simplify SvPV_shrink_to_cur() usage in toke.c
richardleach May 21, 2025
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16 changes: 13 additions & 3 deletions sv.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1590,9 +1590,19 @@ L</C<SV_CHECK_THINKFIRST_COW_DROP>> before calling this.
=cut
*/

#define SvPV_shrink_to_cur(sv) STMT_START { \
const STRLEN _lEnGtH = SvCUR(sv) + 1; \
SvPV_renew(sv, _lEnGtH); \
/* Notes: Ensure the buffer is big enough to be COWed in the future, so
+ 1 for the trailing null byte + 1 for the COW count.
* Don't try to shrink if the saving is too small to be realistic (given
* the realities of allocators) or noticeable.
* Don't try to shrink smaller than PERL_STRLEN_NEW_MIN, as that is
* unlikely to result in a smaller allocation.
*/

#define SvPV_shrink_to_cur(sv) STMT_START { \
const STRLEN _lEnGtH = SvCUR(sv) + 2; \
if ((SvLEN(sv) > _lEnGtH + PTRSIZE) && \
( _lEnGtH >= PERL_STRLEN_NEW_MIN) ) \
SvPV_renew(sv, _lEnGtH); \
} STMT_END

/*
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13 changes: 3 additions & 10 deletions toke.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4422,9 +4422,7 @@ S_scan_const(pTHX_ char *start)
}

/* shrink the sv if we allocated more than we used */
if (SvCUR(sv) + 5 < SvLEN(sv)) {
SvPV_shrink_to_cur(sv);
}
SvPV_shrink_to_cur(sv);

/* return the substring (via pl_yylval) only if we parsed anything */
if (s > start) {
Expand Down Expand Up @@ -11348,9 +11346,7 @@ S_scan_heredoc(pTHX_ char *s)
SvREFCNT_dec_NN(newstr);
}

if (SvCUR(tmpstr) + 5 < SvLEN(tmpstr)) {
SvPV_shrink_to_cur(tmpstr);
}
SvPV_shrink_to_cur(tmpstr);

if (!IN_BYTES) {
if (UTF && is_utf8_string((U8*)SvPVX_const(tmpstr), SvCUR(tmpstr)))
Expand Down Expand Up @@ -11877,10 +11873,7 @@ Perl_scan_str(pTHX_ char *start, int keep_bracketed_quoted, int keep_delims, int
PL_parser->herelines = herelines;

/* if we allocated too much space, give some back */
if (SvCUR(sv) + 5 < SvLEN(sv)) {
SvLEN_set(sv, SvCUR(sv) + 1);
SvPV_shrink_to_cur(sv);
}
SvPV_shrink_to_cur(sv);

/* decide whether this is the first or second quoted string we've read
for this op
Expand Down
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