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Commitf4ceb7a

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Fix regex match failures for backrefs combined with non-greedy quantifiers.
An ancient logic error in cfindloop() could cause the regex engine to failto find matches that begin later than the start of the string. Thisfunction is only used when the regex pattern contains a back reference,and so far as we can tell the error is only reachable if the pattern isnon-greedy (i.e. its first quantifier uses the ? modifier). Furthermore,the actual match must begin after some potential match that satisfies theDFA but then fails the back-reference's match test.Reported and fixed by Jeevan Chalke, with cosmetic adjustments by me.
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‎src/backend/regex/regexec.c

Lines changed: 11 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -467,19 +467,21 @@ cfindloop(struct vars * v,
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*coldp=cold;
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returner;
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}
470-
if ((shorter) ?end==estop :end==begin)
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{
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/* no point in trying again */
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*coldp=cold;
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returnREG_NOMATCH;
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}
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/* go around and try again */
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/* try next shorter/longer match with same begin point */
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if (shorter)
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{
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if (end==estop)
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break;/* NOTE BREAK OUT */
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estart=end+1;
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}
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else
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{
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if (end==begin)
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break;/* NOTE BREAK OUT */
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estop=end-1;
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}
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}
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}
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}/* end loop over endpoint positions */
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}/* end loop over beginning positions */
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}while (close<v->stop);
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*coldp=cold;

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