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bug#34085: autoscan reports a warning

From: Danny Milosavljevic
Subject: bug#34085: autoscan reports a warning
Date: Wed, 16 Jan 2019 17:29:16 +0100


On Tue, 15 Jan 2019 10:43:49 -0500
Joshua Branson <address@hidden> wrote:

> I'm not certain if this is the right list to report this to, but I just
> installed autoscan version 2.21, and it gave me this warning:
>   autoscan
> Unescaped left brace in regex is deprecated here (and will be fatal in Perl 
> 5.30), passed through in regex; marked by <-- HERE in m/\${ <-- HERE [^\}]*}/ 
> at /home/joshua/.guix-profile/bin/autoscan line 361.
> Should I report this upstream instead?

I think so, yes.

autoscan is part of autoconf 2.21, so the bug report should go to the autoconf 

The regexp in question is


Perl is complaining because perl regexp use curly braces to specify a range of 
valid repeats.
Maybe the easiest way to understand it is that the following equivalences hold 
in regexps:

? is equivalent to {0,1}
+ is equivalent to {1,}
* is equivalent to {0,}

The above (at the end of the regexp "\${[^\}]*}") probably means a literal curly
brace--but they don't escape it - hence the warning.

It's only a warning because no valid repeat range can start with a closing curly
So perl can still figure out what you meant.

But it's obviously not recommended to use unescaped closing curly braces to
match a literal closing curly brace regardless.

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