Re: [v2.35.0 regression] some PCRE hangs under UTF-8 locale (was: [PATCH 1/2] grep/pcre2: use PCRE2_UTF even with ASCII patterns)

Am 29.01.22 um 18:25 schrieb SZEDER Gábor:

On Sat, Dec 18, 2021 at 08:50:02PM +0100, René Scharfe wrote:

quoted

compile_pcre2_pattern() currently uses the option PCRE2_UTF only for
patterns with non-ASCII characters.  Patterns with ASCII wildcards can
match non-ASCII strings, though.  Without that option PCRE2 mishandles
UTF-8 input, though -- it matches parts of multi-byte characters.  Fix
that by using PCRE2_UTF even for ASCII-only patterns.

This is a remake of the reverted ae39ba431a (grep/pcre2: fix an edge
case concerning ascii patterns and UTF-8 data, 2021-10-15).  The change
to the condition and the test are simplified and more targeted.

Original-patch-by: Hamza Mahfooz [off-list ref]
Signed-off-by: René Scharfe <redacted>
---
 grep.c                          | 2 +-
 t/t7812-grep-icase-non-ascii.sh | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/grep.c b/grep.c
index fe847a0111..5badb6d851 100644
--- a/grep.c
+++ b/grep.c

@@ -382,7 +382,7 @@ static void compile_pcre2_pattern(struct grep_pat *p, const struct grep_opt *opt
 		}
 		options |= PCRE2_CASELESS;
 	}
-	if (!opt->ignore_locale && is_utf8_locale() && has_non_ascii(p->pattern) &&
+	if (!opt->ignore_locale && is_utf8_locale() &&
 	    !(!opt->ignore_case && (p->fixed || p->is_fixed)))
 		options |= (PCRE2_UTF | PCRE2_MATCH_INVALID_UTF);

I tried to use 'git grep -P' for the first time ever, and it hung
right away, spinning all CPUs at 100%.  I could narrow it down, both
the complexity of the pattern and the size of the input, see the test
below, and it bisects to this patch.


  ---   >8   ---

#!/bin/sh

test_description='test'

. ./test-lib.sh

test_expect_success PCRE 'test' '
	# LC_ALL=C works
	LC_ALL=en_US.UTF-8 &&
	cat >ascii <<-\EOF &&
	foo
	 bar
	 baz
	EOF
	cat >utf8 <<-\EOF &&
	foo
	 bar
	 báz
	EOF
	git add ascii utf8 &&

	# These all work as expected:
	git grep --threads=1 -P " " ascii &&
	git grep --threads=1 -P "^ " ascii &&
	git grep --threads=1 -P "\s" ascii &&
	git grep --threads=1 -P "^\s" ascii &&
	git grep --threads=1 -P " " utf8 &&
	git grep --threads=1 -P "^ " utf8 &&
	git grep --threads=1 -P "\s" utf8 &&

	# This hangs (but it does work with basic and extended regexp):
	git grep --threads=1 -P "^\s" utf8
'

test_done

I get the following result and no hang with PCRE2 10.39:

   utf8: bar
   utf8: báz

e0c6029 (Fix inifinite loop when a single byte newline is searched in
JIT., 2020-05-29) [1] sounds like it might have fixed it.  It's part of
version 10.36.

Do you still get the error when you disable JIT, i.e. when you use the
pattern "(*NO_JIT)^\s" instead?

René


[1] https://github.com/PhilipHazel/pcre2/commit/e0c6029a62db9c2161941ecdf459205382d4d379