bug#57604: Bug#1019724: warning: stray \ before - causes autopkgtest failure

[Paul Eggert]

On 9/19/22 05:32, Santiago Ruano Rincón wrote:

> as you can read below, there are 4235 packages including the
> warning in their build logs. Funnily, grep is also in the list :-)

Grep is on the list because Debian indirectly requires ucf to build 
Grep, and ucf issues the warning about stray \ because ucf mistakenly 
uses a Perlism in a grep regular expression 
<https://bugs.debian.org/1019326>. This particular warning doesn't break 
anything; it merely alerts installers of a screwup that happens to work 
but relies on undefined results.

We're thinking about adding a configure-time option to Grep to disable 
warnings about egrep/fgrep, to address the original Grep bug report 
<https://bugs.gnu.org/57604>. I'm not so sure about disabling warnings 
about bad escapes, as these warnings are so often a win and so rarely a 
loss, as is the case with ucf. Of course there is a tradeoff here 
between (a) having to wade through a bunch of annoying warnings, and (b) 
fixing packages so that they don't rely on undefined results.

Since the main issue here seems to be libtool-related test failures, how 
about patching libtool and letting the affected packages use the patched 
libtool? You can find a patch here:

https://savannah.gnu.org/patch/index.php?10282
https://savannah.gnu.org/patch/download.php?file_id=53720

The libtool test failures are false alarms, so another option would be 
to ignore the failures until libtool gets fixed.


For more on this thorny topic, please see:

https://www.gnu.org/software/grep/manual/html_node/Problematic-Expressions.html

The stray \ issue is the 19th bullet.