From: Rich Felker <dalias@libc.org>
To: "liheng (P)" <liheng40@huawei.com>
Cc: Szabolcs Nagy <nsz@port70.net>,
"musl@lists.openwall.com" <musl@lists.openwall.com>,
Florian Weimer <fw@deneb.enyo.de>,
"Xiangrui (Euler)" <rui.xiang@huawei.com>,
Lizefan <lizefan@huawei.com>
Subject: Re: [musl] regex Back reference matching result not same as glibc and tre.
Date: Sun, 19 Apr 2020 21:26:35 -0400 [thread overview]
Message-ID: <20200420012635.GX11469@brightrain.aerifal.cx> (raw)
In-Reply-To: <6D612B6AC5DCDA4580AF97B1068118AD2DD415@DGGEML501-MBX.china.huawei.com>
On Sun, Apr 19, 2020 at 12:26:58PM +0000, liheng (P) wrote:
> Ok, you are right, I retest to match "aba" by pat[] =
> "\\(.\\?\\).\\?\\1" success without tags (basic regular expression
> mode I think). regcomp1(&rbuf, pat, 0);
>
> But my point is that why pat[] = "(.?).?\\1" to match "aba" in
> extended regular expression mode that success in glibc and failed in
> musl? Are musl-regex and glibc-regex different?
Having backreferences in regular expressions is inherently a bug,
because it makes them non-regular and unsafe for use where the
expression is user input and finishing in finite time is a
requirement. They're supported in BRE because it's a historical
requirement impossed by the standard, but a major *feature* of ERE is
actually being regular and not having backreferences.
Rich
prev parent reply other threads:[~2020-04-20 1:26 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-18 8:44 liheng (P)
2020-04-18 10:28 ` Florian Weimer
2020-04-18 11:07 ` liheng (P)
2020-04-18 11:13 ` Szabolcs Nagy
2020-04-18 11:37 ` liheng (P)
2020-04-18 14:07 ` Szabolcs Nagy
2020-04-19 12:26 ` liheng (P)
2020-04-19 13:10 ` Florian Weimer
2020-04-20 1:26 ` Rich Felker [this message]
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