Bug#663514: libsdl-perl: FTBFS on i386 Xen/KVM VMs: Failed test 'MMX_detect (MMX is same as at start)'

[Steve Langasek]

severity 663514 serious
reassign 663514 src:sdlgfx
found 663514 2.0.23-1
tags 663514 patch
user ubuntu-devel at lists.ubuntu.com
usertags 663514 ubuntu-patch quantal
thanks

Hi there,

> This package FTBFS on my Xen and KVM based VMs on i386 (but not amd64):

The problem is definitely not specific to Xen/KVM.  An i386 chroot on an
Ubuntu system shows the same build failure:

  https://bugs.launchpad.net/debian/+source/libsdl-perl/+bug/1029981

The problem is that the cpuFlags() function used for querying cpuid is
returning garbage data from the stack.  So the sdl-perl test suite passes if
the garbage returned happens to not have the MMX bit set both times, and
otherwise it fails.

I've done some analysis on the linked Ubuntu bug, showing the bug in the
disassembled binary, and uploaded a fixed package to Ubuntu which I've
confirmed detects mmx support properly and lets libsdl-perl's test suite
pass reliably.

The attached patch should be suitable for uploading to Debian as well. 
Please consider applying it at your earliest convenience, or let me know if
you would like me to NMU instead.

Since this bug in practice causes libsdl-perl to not be reliably rebuildable
(more precisely, causes its buildability to depend entirely on random
unrelated permutations of the stack, which may change over the lifetime of
wheezy), I'm marking this bug as 'serious' for the release.

Thanks,
-- 
Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
Ubuntu Developer                                    http://www.debian.org/
slangasek at ubuntu.com                                     vorlon at debian.org
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