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fix: reject \NN backrefs with non-octal leading digit #40

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fix: reject \NN backrefs with non-octal leading digit #40

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2 changes: 2 additions & 0 deletions lib/Regexp/Parser/Handlers.pm
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Original file line number Diff line number Diff line change
Expand Up @@ -560,6 +560,8 @@ sub init {
if (!&SIZE_ONLY and !$cc and $n != 0) {
$v .= $1 while ${&Rx} =~ m{ \G (\d) }xgc;
if ($v > 9 and $v > $S->{maxpar}) {
# leading digit 8 or 9 has no valid octal fallback
$S->error($S->RPe_BGROUP) if $n > 7;
&RxPOS -= length $v;
$v = "";
}
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11 changes: 11 additions & 0 deletions t/11errors.t
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Expand Up @@ -167,6 +167,17 @@ fails_visual('(a)\\2', ($r->RPe_BGROUP)[0], '\\2 with only 1 capture group')
fails_visual('\\g{5}', ($r->RPe_BGROUP)[0], '\\g{5} with no capture groups');
fails_visual('\\g{-1}', ($r->RPe_BGROUP)[0], '\\g{-1} (relative) with no groups');

# Multi-digit backrefs starting with 8 or 9 have no valid octal fallback
# Perl rejects these as "Reference to nonexistent group"
fails_visual('(a)\\99', ($r->RPe_BGROUP)[0], '\\99 with 1 group (not valid octal)');
fails_visual('(a)\\80', ($r->RPe_BGROUP)[0], '\\80 with 1 group (not valid octal)');
fails_visual('(a)\\89', ($r->RPe_BGROUP)[0], '\\89 with 1 group (not valid octal)');
fails_visual('(a)\\98', ($r->RPe_BGROUP)[0], '\\98 with 1 group (not valid octal)');

# Multi-digit numbers with valid octal leading digit fall back to octal
parses_ok('(a)\\77', '\\77 with 1 group — valid octal fallback (chr 63)');
parses_ok('(a)\\100', '\\100 with 1 group — valid octal fallback (chr 64)');

# Valid backrefs should work
parses_ok('(a)\\1', 'valid backref \\1 with 1 group');
parses_ok('(a)(b)\\2', 'valid backref \\2 with 2 groups');
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