Re: [PATCH] regex: fix match with possessive quantifier

[Paul Eggert]

On 6/6/21 2:45 PM, Dmitry V. Levin wrote:
> I've applied it now, and the following follow-up patch:

These recently-installed patches fail for me, which indicates that the 
patches aren't correct. Could you please fix this? The test failure is 
causing 'make check' to fail for GNU grep.

I tested on Ubuntu 21.04 x86-64 (with its packaged GCC 10.3.0-1ubuntu1), 
as follows:

./gnulib-tool --create-testdir --dir foo regex
cd foo
./configure CFLAGS='-g3 -O2 -fsanitize=undefined'
make check

foo/gltests/test-regex.log contains:

regex_internal.c:1317:7: runtime error: execution reached an unreachable 
program point
FAIL test-regex (exit status: 1)

The failing line is here:

      DEBUG_ASSERT (set->elems[idx - 1] < elem);

I got a similar failure when I configured this way instead:

./configure CFLAGS='-g3 -O2 -DDEBUG'

the only difference being a different diagnostic in test-regex.log:

test-regex: regex_internal.c:1317: re_node_set_insert: Assertion 
`set->elems[idx - 1] < elem' failed.
FAIL test-regex (exit status: 134)

The problem is not limited to Ubuntu, as I got a similar failure on 
Fedora 34 with its packaged GCC 11.1.1 20210531 (Red Hat 11.1.1-3).