postgres.git / summary / log / commit / refs
commit 244dd79923a16afcf5f9a8dea53fc3af2ac0f7db
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date: Tue Aug 24 20:37:27 2021 +0000
Fix regexp misbehavior with capturing parens inside "{0}".
Regexps like "(.){0}...\1" drew an "invalid backreference number".
That's not unreasonable on its face, since the capture group will
never be matched if it's iterated zero times. However, other engines
such as Perl's don't complain about this, nor do we throw an error for
related cases such as "(.)|\1", even though that backref can never
succeed either. Also, if the zero-iterations case happens at runtime
rather than compile time --- say, "(x)*...\1" when there's no "x" to
be found --- that's not an error, we just deem the backref to not
match. Making this even less defensible, no error was thrown for
nested cases such as "((.)){0}...\2"; and to add insult to injury,
those cases could result in assertion failures instead. (It seems
that nothing especially bad happened in non-assert builds, though.)
Let's just fix it so that no error is thrown and instead the backref
is deemed to never match, so that compile-time detection of no
iterations behaves the same as run-time detection.
Per report from Mark Dilger. This appears to be an aboriginal error
in Spencer's library, so back-patch to all supported versions.
Pre-v14, it turns out to also be necessary to back-patch one aspect of
commits cb76fbd7e/00116dee5, namely to create capture-node subREs with
the begin/end states of their subexpressions, not the current lp/rp
of the outer parseqatom invocation. Otherwise delsub complains that
we're trying to disconnect a state from itself. This is a bit scary
but code examination shows that it's safe: in the pre-v14 code, if we
want to wrap iteration around the subexpression, the first thing we do
is overwrite the atom's begin/end fields with new states. So the
bogus values didn't survive long enough to be used for anything, except
if no iteration is required, in which case it doesn't matter.
Discussion: https://postgr.es/m/A099E4A8-4377-4C64-A98C-3DEDDC075502@enterprisedb.com
src/backend/regex/regcomp.c | 22 +++++++++++++++++-----
.../modules/test_regex/expected/test_regex.out | 22 ++++++++++++++++++++++
src/test/modules/test_regex/sql/test_regex.sql | 6 ++++++
src/test/regress/expected/regex.out | 19 +++++++++++++++++++
src/test/regress/sql/regex.sql | 5 +++++
5 files changed, 69 insertions(+), 5 deletions(-)
diff --git a/src/backend/regex/regcomp.c b/src/backend/regex/regcomp.c
index 60a220c57ab..bfe12eb08b3 100644
--- a/src/backend/regex/regcomp.c
+++ b/src/backend/regex/regcomp.c
@@ -1086,11 +1086,23 @@ parseqatom(struct vars *v,
/* annoying special case: {0} or {0,0} cancels everything */
if (m == 0 && n == 0)
{
- if (atom != NULL)
- freesubre(v, atom);
- if (atomtype == '(')
- v->subs[subno] = NULL;
- delsub(v->nfa, lp, rp);
+ /*
+ * If we had capturing subexpression(s) within the atom, we don't want
+ * to destroy them, because it's legal (if useless) to back-ref them
+ * later. Hence, just unlink the atom from lp/rp and then ignore it.
+ */
+ if (atom != NULL && (atom->flags & CAP))
+ {
+ delsub(v->nfa, lp, atom->begin);
+ delsub(v->nfa, atom->end, rp);
+ }
+ else
+ {
+ /* Otherwise, we can clean up any subre infrastructure we made */
+ if (atom != NULL)
+ freesubre(v, atom);
+ delsub(v->nfa, lp, rp);
+ }
EMPTYARC(lp, rp);
return top;
}
diff --git a/src/test/modules/test_regex/expected/test_regex.out b/src/test/modules/test_regex/expected/test_regex.out
index 83fb9a8b9ca..06f8881cfaf 100644
--- a/src/test/modules/test_regex/expected/test_regex.out
+++ b/src/test/modules/test_regex/expected/test_regex.out
@@ -3490,6 +3490,28 @@ select * from test_regex('((.))(\2){0}', 'xy', 'RPQ');
{x,x,x,NULL}
(2 rows)
+-- expectNomatch 21.39 PQR {(.){0}(\1)} xxx
+select * from test_regex('(.){0}(\1)', 'xxx', 'PQR');
+ test_regex
+--------------------------------------------
+ {2,REG_UBACKREF,REG_UBOUNDS,REG_UNONPOSIX}
+(1 row)
+
+-- expectNomatch 21.40 PQR {((.)){0}(\2)} xxx
+select * from test_regex('((.)){0}(\2)', 'xxx', 'PQR');
+ test_regex
+--------------------------------------------
+ {3,REG_UBACKREF,REG_UBOUNDS,REG_UNONPOSIX}
+(1 row)
+
+-- expectMatch 21.41 NPQR {((.)){0}(\2){0}} xyz {} {} {} {}
+select * from test_regex('((.)){0}(\2){0}', 'xyz', 'NPQR');
+ test_regex
+------------------------------------------------------------
+ {3,REG_UBACKREF,REG_UBOUNDS,REG_UNONPOSIX,REG_UEMPTYMATCH}
+ {"",NULL,NULL,NULL}
+(2 rows)
+
-- doing 22 "multicharacter collating elements"
-- # again ugh
-- MCCEs are not implemented in Postgres, so we skip all these tests
diff --git a/src/test/modules/test_regex/sql/test_regex.sql b/src/test/modules/test_regex/sql/test_regex.sql
index 991f804cb67..bdc090103b1 100644
--- a/src/test/modules/test_regex/sql/test_regex.sql
+++ b/src/test/modules/test_regex/sql/test_regex.sql
@@ -1015,6 +1015,12 @@ select * from test_regex('(a*)*', 'bc', 'N');
select * from test_regex(' TO (([a-z0-9._]+|"([^"]+|"")+")+)', 'asd TO foo', 'M');
-- expectMatch 21.36 RPQ ((.))(\2){0} xy x x x {}
select * from test_regex('((.))(\2){0}', 'xy', 'RPQ');
+-- expectNomatch 21.39 PQR {(.){0}(\1)} xxx
+select * from test_regex('(.){0}(\1)', 'xxx', 'PQR');
+-- expectNomatch 21.40 PQR {((.)){0}(\2)} xxx
+select * from test_regex('((.)){0}(\2)', 'xxx', 'PQR');
+-- expectMatch 21.41 NPQR {((.)){0}(\2){0}} xyz {} {} {} {}
+select * from test_regex('((.)){0}(\2){0}', 'xyz', 'NPQR');
-- doing 22 "multicharacter collating elements"
-- # again ugh
diff --git a/src/test/regress/expected/regex.out b/src/test/regress/expected/regex.out
index cbe2cfc3ea1..ae0de7307db 100644
--- a/src/test/regress/expected/regex.out
+++ b/src/test/regress/expected/regex.out
@@ -567,6 +567,25 @@ select 'a' ~ '()+\1';
t
(1 row)
+-- Test incorrect removal of capture groups within {0}
+select 'xxx' ~ '(.){0}(\1)' as f;
+ f
+---
+ f
+(1 row)
+
+select 'xxx' ~ '((.)){0}(\2)' as f;
+ f
+---
+ f
+(1 row)
+
+select 'xyz' ~ '((.)){0}(\2){0}' as t;
+ t
+---
+ t
+(1 row)
+
-- Test ancient oversight in when to apply zaptreesubs
select 'abcdef' ~ '^(.)\1|\1.' as f;
f
diff --git a/src/test/regress/sql/regex.sql b/src/test/regress/sql/regex.sql
index c6974a43d11..56217104ce6 100644
--- a/src/test/regress/sql/regex.sql
+++ b/src/test/regress/sql/regex.sql
@@ -135,6 +135,11 @@ select 'a' ~ '.. ()|\1';
select 'a' ~ '()*\1';
select 'a' ~ '()+\1';
+-- Test incorrect removal of capture groups within {0}
+select 'xxx' ~ '(.){0}(\1)' as f;
+select 'xxx' ~ '((.)){0}(\2)' as f;
+select 'xyz' ~ '((.)){0}(\2){0}' as t;
+
-- Test ancient oversight in when to apply zaptreesubs
select 'abcdef' ~ '^(.)\1|\1.' as f;
select 'abadef' ~ '^((.)\2|..)\2' as f;
[parent: 5cfcd46e9d29]