Horton

Re: BUG #16814: Invalid memory access on regexp_match with .* and BRE

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: exclusion@gmail.com
Cc: pgsql-bugs@lists.postgresql.org
Date: 2021-01-08T17:19:46Z
Lists: pgsql-bugs 
PG Bug reporting form <noreply@postgresql.org> writes:
> When executing the following regexp call:
> select regexp_match('abc', '.*', 'b');
> valgrind detects an error:

Hah, nice one.  It gives the wrong answer too, at least it does most of
the time for me:

# select regexp_match('abc', '.*', 'b');
 regexp_match 
--------------
 {""}
(1 row)

That's because it's acting like the pattern is '.*?' (prefer shortest
match) rather than '.*'.

This bug is well over the age of consent, btw.  Tcl's got it too,
so it surely is aboriginal in Henry Spencer's code.

Thanks for the report!

			regards, tom lane

Commits

  1. Fix ancient bug in parsing of BRE-mode regular expressions.