From: Mark Dilger <mark.dilger@enterprisedb.com>
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Subject: Assert triggered during RE_compile_and_cache
Message-Id: <0203588E-E609-43AF-9F4F-902854231EE7@enterprisedb.com>
Date: Thu, 5 Aug 2021 13:38:58 -0700
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
To: Tom Lane <tgl@sss.pgh.pa.us>
Archived-At: 
 <https://www.postgresql.org/message-id/0203588E-E609-43AF-9F4F-902854231EE7%40enterprisedb.com>
Precedence: bulk

Tom,

while testing your patch in [1], I stumbled upon the following assert in =
master, without your patch applied:

+select 'vyrlvyrlwvqko' ~ '(?:(?:((.))))((\2)\1.){0,0}?';
+server closed the connection unexpectedly
+   This probably means the server terminated abnormally
+   before or while processing the request.
+connection to server was lost


The assert itself dates back to a commit of yours from 2003.  I don't =
think you did anything wrong here, but I wonder if you might understand =
the code better than anyone else?

The relevant bit of the stack trace is:

    frame #3: 0x00000001020eff7d =
postgres`ExceptionalCondition(conditionName=3D<unavailable>, =
errorType=3D<unavailable>, fileName=3D<unavailable>, =
lineNumber=3D<unavailable>) at assert.c:69:2 [opt]
    frame #4: 0x0000000101e2c682 postgres`delsub(nfa=3D0x00007fc7e8407360,=
 lp=3D0x00007fc7e8831010, rp=3D0x00007fc7e8827328) at regc_nfa.c:1265:2 =
[opt]
    frame #5: 0x0000000101e28dd8 postgres`parsebranch [inlined] =
parseqatom(v=3D<unavailable>, stopper=3D101, type=3D112, =
lp=3D<unavailable>, rp=3D0x00007fc7e8827328, top=3D<unavailable>) at =
regcomp.c:1084:3 [opt]
    frame #6: 0x0000000101e27de9 =
postgres`parsebranch(v=3D0x00007ffeee0a80b8, stopper=3D101, =
type=3D<unavailable>, left=3D<unavailable>, right=3D<unavailable>, =
partial=3D<unavailable>) at regcomp.c:759 [opt]
    frame #7: 0x0000000101e29719 postgres`parsebranch [inlined] =
parseqatom(v=3D<unavailable>, stopper=3D101, type=3D112, =
lp=3D<unavailable>, rp=3D0x00007fc7e8827328, top=3D<unavailable>) at =
regcomp.c:1282:23 [opt]
    frame #8: 0x0000000101e29639 =
postgres`parsebranch(v=3D0x00007ffeee0a80b8, stopper=3D101, =
type=3D<unavailable>, left=3D<unavailable>, right=3D<unavailable>, =
partial=3D<unavailable>) at regcomp.c:759 [opt]
    frame #9: 0x0000000101e2457b postgres`parse(v=3D0x00007ffeee0a80b8, =
stopper=3D101, type=3D112, init=3D0x00007fc7e8827280, =
final=3D0x00007fc7e88272b8) at regcomp.c:691:12 [opt]
    frame #10: 0x0000000101e234d2 =
postgres`pg_regcomp(re=3D0x00007ffeee0a8208, string=3D<unavailable>, =
len=3D<unavailable>, flags=3D<unavailable>, collation=3D<unavailable>) =
at regcomp.c:418:12 [opt]
    frame #11: 0x0000000101f75790 =
postgres`RE_compile_and_cache(text_re=3D<unavailable>, =
cflags=3D<unavailable>, collation=3D100) at regexp.c:186:19 [opt]
    frame #12: 0x0000000101f75b90 postgres`textregexeq [inlined] =
RE_compile_and_execute(text_re=3D<unavailable>, dat=3D<unavailable>, =
dat_len=3D13, cflags=3D3, collation=3D<unavailable>, nmatch=3D0, =
pmatch=3D<unavailable>) at regexp.c:351:7 [opt]

[1] =
https://www.postgresql.org/message-id/2219936.1628115334%40sss.pgh.pa.us

=E2=80=94
Mark Dilger
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company