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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/111129] std::regex incorrectly matches quantifiers
 with plus appended
Date: Thu, 24 Aug 2023 15:16:12 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111129

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |timshen at gcc dot gnu.org

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
This changed with r0-127716-g053eb1f31ede72

            * include/bits/regex_compiler.h (_Comipler<>::_M_quantifier()):
            Fix parse error of multiple consecutive quantifiers like "a**".
            * include/bits/regex_compiler.tcc (_Comipler<>::_M_quantifier()=
):
            Likewise.
            * testsuite/28_regex/basic_regex/multiple_quantifiers.cc: New.

That added the following tests:

  regex re1("a++");
  regex re2("(a+)+");

The second one is fine, but the first is invalid. The "a**" case mentioned =
in
the commit message is invalid too.

I don't know why Tim wanted to accept the first one. ECMAscript and POSIX d=
on't
accept it. My GNU grep does, but I think that's just a bug in glibc's regco=
mp:
https://sourceware.org/bugzilla/show_bug.cgi?id=3D20095=