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Re: "grep '\]'" warnings suggest a Gnulib DFA patch

From: Bruno Haible
Subject: Re: "grep '\]'" warnings suggest a Gnulib DFA patch
Date: Sat, 04 Jun 2022 05:08:39 +0200

Paul Eggert asked:
> So, what do you think of the idea of not warning for this particular 
> stray backslash? Proposed Gnulib patch attached, with the idea of 
> propagating this into GNU grep before its upcoming release. I haven't 
> installed this.

Warning about undefined behaviour is good.

But when I think about the thousands of people who use regular expressions
out there. How would they remember that in parentheses both should be
backslash-escaped in EREs
    \(   \)
but brackets and braces are asymmetric
    \[   ]
    \{   }
Even if the warning message you install in grep has 3 or 5 lines and goes
into all details, we are not serving the community if we force them to adhere
to asymmetric rules, where up to now they could use symmetric rules.


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