From 9618fb718b75920f37e5be2049ad1d0bb5c4a28c Mon Sep 17 00:00:00 2001

From: Paul Eggert <eggert@cs.ucla.edu>

Date: Tue, 26 Jan 2021 09:23:54 -0800

Subject: [PATCH] expr: fix bug with unmatched \(...\)

Problem reported by Qiuhao Li.

* doc/coreutils.texi (String expressions):

Document the correct behavior, which POSIX requires.

* src/expr.c (docolon): Treat unmatched \(...\) as empty.

* tests/misc/expr.pl: New test.

Upstream-commit: 735083ba24878075235007b4417982ad5700436d

Signed-off-by: Kamil Dudka <kdudka@redhat.com>

---

 doc/coreutils.texi | 14 ++++++++------

 src/expr.c         |  9 +++++++--

 tests/misc/expr.pl |  3 +++

 3 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/doc/coreutils.texi b/doc/coreutils.texi

index 2382a16..5b2bb2c 100644

--- a/doc/coreutils.texi

+++ b/doc/coreutils.texi

@@ -13529,12 +13529,14 @@ second is considered to be a (basic, a la GNU @code{grep}) regular

 expression, with a @code{^} implicitly prepended.  The first argument is

 then matched against this regular expression.

-If the match succeeds and @var{regex} uses @samp{\(} and @samp{\)}, the

-@code{:} expression returns the part of @var{string} that matched the

-subexpression; otherwise, it returns the number of characters matched.

-

-If the match fails, the @code{:} operator returns the null string if

-@samp{\(} and @samp{\)} are used in @var{regex}, otherwise 0.

+If @var{regex} does not use @samp{\(} and @samp{\)}, the @code{:}

+expression returns the number of characters matched, or 0 if the match

+fails.

+

+If @var{regex} uses @samp{\(} and @samp{\)}, the @code{:} expression

+returns the part of @var{string} that matched the subexpression, or

+the null string if the match failed or the subexpression did not

+contribute to the match.

 @kindex \( @r{regexp operator}

 Only the first @samp{\( @dots{} \)} pair is relevant to the return

diff --git a/src/expr.c b/src/expr.c

index e134872..0616a42 100644

--- a/src/expr.c

+++ b/src/expr.c

@@ -721,8 +721,13 @@ docolon (VALUE *sv, VALUE *pv)

       /* Were \(...\) used? */

       if (re_buffer.re_nsub > 0)

         {

-          sv->u.s[re_regs.end[1]] = '\0';

-          v = str_value (sv->u.s + re_regs.start[1]);

+          if (re_regs.end[1] < 0)

+            v = str_value ("");

+          else

+            {

+              sv->u.s[re_regs.end[1]] = '\0';

+              v = str_value (sv->u.s + re_regs.start[1]);

+            }

         }

       else

         {

diff --git a/tests/misc/expr.pl b/tests/misc/expr.pl

index e45f8e7..e57f79d 100755

--- a/tests/misc/expr.pl

+++ b/tests/misc/expr.pl

@@ -84,6 +84,9 @@ my @Tests =

      # In 5.94 and earlier, anchors incorrectly matched newlines.

      ['anchor', "'a\nb' : 'a\$'", {OUT => '0'}, {EXIT => 1}],

+     # In 8.32, \( ... \) that did not match caused memory errors.

+     ['emptysub', '"a" : "\\(b\\)*"', {OUT => ''}, {EXIT => 1}],

+

      # These tests are taken from grep/tests/bre.tests.

      ['bre1', '"abc" : "a\\(b\\)c"', {OUT => 'b'}],

      ['bre2', '"a(" : "a("', {OUT => '2'}],

-- 

2.26.2