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Clear all variable pad slots after multi-variable foreach loop

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We need to remember to clear all the pad slots related to iteration
variables, which means some number of additional ones after the main
"itervar" when doing multi-variable iteration. This ensures we don't
retain references or large scalar values longer than necessary.
This commit is contained in:
Paul "LeoNerd" Evans 2025-12-24 14:12:33 +00:00 committed by Paul Evans
parent 47a5d1f4d9
commit 4430717932
2 changed files with 34 additions and 0 deletions
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19
inline.h
View File

@ -4152,6 +4152,25 @@ Perl_cx_poploop(pTHX_ PERL_CONTEXT *cx)
cx->blk_loop.itersave = NULL;
SvREFCNT_dec(cursv);
}
if (CxPADLOOP(cx)) {
/* for my ... might be multivariable. my_op->op_next will point at
* the OP_ITER whose op_targ contains the count of how many more
* variables
*/
OP *iterop = cx->blk_loop.my_op->op_next;
assert(iterop->op_type == OP_ITER);
PADOFFSET how_many = iterop->op_targ;
/* op_targ actually stores count - 1, so it's the count of additional
* vars after itervar itself */
for (SV **svp = cx->blk_loop.itervar_u.svp + 1; how_many; svp++, how_many--) {
/* we didn't store an itersave for these, but we know they are all
* scoped to the loop we have just left. It's therefore safe to store
* &PL_sv_undef there since they weren't live before or afterwards.
*/
SvREFCNT_dec(*svp);
*svp = &PL_sv_undef;
}
}
if (cx->cx_type & CXp_FOR_LVREF) {
SV *itervar = (SV *)(cx)->blk_loop.itervar_u.gv;
SV *origval = (cx)->blk_loop.itersave;

15
t/op/for-many.t
View File

@ -511,4 +511,19 @@ is($continue, 'xx', 'continue reached twice');
pass '2-var for does not crash on lexical sub calls';
}
# all foreach iteration vars are cleared in a timely manner
{
my @arrx;
my @arry;
for my ($x, $y) (\@arrx, \@arry) {
# list items are aliased; add 1 to account for \ ref in the following
refcount_is \@arrx, 2+1, 'arrx refcount 2 inside loop';
refcount_is \@arry, 2+1, 'arry refcount 2 inside loop';
}
refcount_is \@arrx, 1+1, 'arrx refcount 1 after loop';
refcount_is \@arry, 1+1, 'arry refcount 1 after loop';
}
done_testing();