On Mon, Aug 23, 2010 at 02:39:10AM +0200, Denys Vlasenko wrote:
> On Thursday 19 August 2010 15:50, Colin Watson wrote:
> > --- a/findutils/grep.c
> > +++ b/findutils/grep.c
> > @@ -463,13 +463,19 @@ static int grep_file(FILE *file)
> > } else while (1) {
> > unsigned end =
> > gl->matched_range.rm_eo;
> > char old = line[end];
> > - line[end] = '\0';
> > - print_line(line +
> > gl->matched_range.rm_so,
> > - end -
> > gl->matched_range.rm_so,
> > - linenum, ':');
> > - if (old == '\0')
> > - break;
> > - line[end] = old;
> > + if (gl->matched_range.rm_so ==
> > gl->matched_range.rm_eo) {
> > + end++;
>
> Why do you think end++ does not run off the end of the line?
Fair point, thanks. Updated version follows.
From: Colin Watson <[email protected]>
Date: Thu, 19 Aug 2010 14:46:48 +0100
Subject: [PATCH] grep: fix infinite loop in -o
If the supplied pattern matches the empty string at the start of a line,
then 'grep -o' would loop forever.
Originally reported as
https://bugs.launchpad.net/ubuntu/+source/busybox/+bug/619817.
Signed-off-by: Colin Watson <[email protected]>
---
findutils/grep.c | 23 ++++++++++++++++-------
testsuite/grep.tests | 4 ++++
2 files changed, 20 insertions(+), 7 deletions(-)
diff --git a/findutils/grep.c b/findutils/grep.c
index 688ea6a..1b53d83 100644
--- a/findutils/grep.c
+++ b/findutils/grep.c
@@ -463,13 +463,22 @@ static int grep_file(FILE *file)
} else while (1) {
unsigned end =
gl->matched_range.rm_eo;
char old = line[end];
- line[end] = '\0';
- print_line(line +
gl->matched_range.rm_so,
- end -
gl->matched_range.rm_so,
- linenum, ':');
- if (old == '\0')
- break;
- line[end] = old;
+ if (gl->matched_range.rm_so ==
gl->matched_range.rm_eo) {
+ /* Already at end of
line? */
+ if (line[end] == '\0')
+ break;
+ /* Otherwise make sure
we make some progress. */
+ if (line[++end] == '\0')
+ break;
+ } else {
+ line[end] = '\0';
+ print_line(line +
gl->matched_range.rm_so,
+ end -
gl->matched_range.rm_so,
+
linenum, ':');
+ if (old == '\0')
+ break;
+ line[end] = old;
+ }
#if !ENABLE_EXTRA_COMPAT
if
(regexec(&gl->compiled_regex, line + end,
1,
&gl->matched_range, REG_NOTBOL) != 0)
diff --git a/testsuite/grep.tests b/testsuite/grep.tests
index 520a184..ad99257 100755
--- a/testsuite/grep.tests
+++ b/testsuite/grep.tests
@@ -98,5 +98,9 @@ testing "grep -o does not loop forever" \
'grep -o "[^/]*$"' \
"test\n" \
"" "/var/test\n"
+testing "grep -o does not loop forever on zero-length match at ^" \
+ 'grep -o "" | head -n1' \
+ "" \
+ "" "test\n"
exit $FAILCOUNT
--
1.7.1
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