[Bug regex/25814] New: Consecutive + operators accepted but have no effect except consuming more memory

["dpmendenhall at gmail dot com" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=25814

            Bug ID: 25814
           Summary: Consecutive + operators accepted but have no effect
                    except consuming more memory
           Product: glibc
           Version: 2.27
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: regex
          Assignee: unassigned at sourceware dot org
          Reporter: dpmendenhall at gmail dot com
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---

Created attachment 12452
  --> https://sourceware.org/bugzilla/attachment.cgi?id=12452&action=edit
test program

The attached test program just takes a regex pattern and a string at the
command line.

$ gcc -o regex regex.c
$ ./regex 0+ 0
pattern: 0+
string: 0

regex matched
$ ./regex 0++ 0
pattern: 0++
string: 0

regex matched
$ ./regex 0++++++++++++++++++++++++++++++++++ 0
pattern: 0++++++++++++++++++++++++++++++++++
string: 0
<hangs consuming all system memory>

I'm not even sure what consecutive + operators is supposed to mean, so I don't
know why "0++" accepts "0".

I tested this against the bionic/NetBSD regex implementation and compilation of
"0++" fails with REG_BADRPT, which makes more sense.

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