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Date: Sat, 18 Apr 2020 11:37:13 +0000
From: "liheng (P)" <liheng40@...wei.com>
To: "musl@...ts.openwall.com" <musl@...ts.openwall.com>
CC: Florian Weimer <fw@...eb.enyo.de>, Rich Felker <dalias@...c.org>,
	"Xiangrui (Euler)" <rui.xiang@...wei.com>, Lizefan <lizefan@...wei.com>
Subject: RE: regex Back reference matching result not same as glibc
 and tre.

static const char pat[] = "\\(.?\\).?\\1";
str = "aba"

ok, I retest this pat with no tag.

regcomp(&rbuf, pat, 0);
regexec1(&rbuf, str, N, m, 0);

 glibc:
 # ./test
 regexec failed
 test regex failed

 musl:
 # ./test
 regexec failed
 test regex failed



-----Original Message-----
From: Szabolcs Nagy [mailto:nsz@...t70.net] 
Sent: Saturday, April 18, 2020 7:13 PM
To: liheng (P) <liheng40@...wei.com>
Cc: Florian Weimer <fw@...eb.enyo.de>; Rich Felker <dalias@...c.org>; musl@...ts.openwall.com; Xiangrui (Euler) <rui.xiang@...wei.com>; Lizefan <lizefan@...wei.com>
Subject: Re: [musl] regex Back reference matching result not same as glibc and tre.

* liheng (P) <liheng40@...wei.com> [2020-04-18 11:07:20 +0000]:
> static const char pat[] = "\\(.?\\).?\\1";
> string: "aba";

? is not special in bre

it should be \{0,1\} (i think we support \? as an extension, but unescaped ? only matches literal ?). try one of

static const char pat[] = "\\(.\\{0,1\\}\\).\\{0,1\\}\\1"; static const char pat[] = "\\(.\\?\\).\\?\\1";

> 
> I tested this pattern by my test case just now.
> 
> musl:
> # ./test
> regexec failed
> test regex failed
> 
> glibc:
> # ./test
> Invalid back reference
> test regex failed
> 
> tre:
> # ./test
> Invalid back reference
> test regex failed
> 
> -----Original Message-----
> From: Florian Weimer [mailto:fw@...eb.enyo.de]
> Sent: Saturday, April 18, 2020 6:29 PM
> To: liheng (P) <liheng40@...wei.com>
> Cc: Rich Felker <dalias@...c.org>; musl@...ts.openwall.com; Xiangrui 
> (Euler) <rui.xiang@...wei.com>; Lizefan <lizefan@...wei.com>
> Subject: Re: [musl] regex Back reference matching result not same as glibc and tre.
> 
> * liheng:
> 
> > static const char pat[] = "(.?).?\\1";
> 
> > This commit reminds me that if i want to use back reference i should 
> > not to tag REG_EXTENDED, but this test case matching still failed.
> 
> 
> Did you change the expression to this for the basic regular expression test?
> 
> static const char pat[] = "\\(.?\\).?\\1";

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