Bug#931641: perl: FTBFS under qemu-user

[Niko Tyni]

Source: perl
Version: 5.30.0-2
Severity: important
Tags: upstream
User: debian-perl at lists.debian.org
Usertags: perl-5.30-transition
X-Debbugs-Cc: John Paul Adrian Glaubitz <glaubitz at physik.fu-berlin.de>

As discussed in the thread at

 https://alioth-lists.debian.net/pipermail/perl-maintainers/2019-June/006711.html

 https://alioth-lists.debian.net/pipermail/perl-maintainers/2019-July/006713.html

Perl fails to build under qemu-user with Configure -Dmksymlinks because
$0 contains an absolute path there and the build machinery can't deal
with that.

This can be reproduced under for instance qemu-armhf with

  mkdir b && cd b && ../Configure -des -Dmksymlinks

resulting in lots of 'Permission denied' errors when extracting cflags.SH
because the script mistakes the shell absolute path for its argument and
tries to write in the same directory where the shell resides.

An even simpler reproducer is

  touch config.sh && sh < cflags.SH

This is not specific to Perl 5.30, our packaging just started to use
-Dmksymlinks there and triggered the issue.

I'm not sure yet where this should be fixed. I'd like to avoid reverting
the -Dmksymlinks part introduced in 5.30.0-2 as I think enabling parallel
builds was an improvement. But we'll see.

This should possibly be considered a Perl 5.30 transition blocker as
at least some Debian ports (m68k, sh4) use qemu-user for buildds.
Adding the usertag for now.
-- 
Niko Tyni   ntyni at debian.org