[PPL-devel] PPL 0.10 testsuite failures on powerpc-linux

[Roberto Bagnara]

Janis Johnson wrote:
> I'm trying to build the Parma Polyhedra Library on powerpc-linux so I
> can use it for Graphite support in GCC.  I've tried a lot of things
> and my builds normally succeed but I get lots of testsuite failures:
> 
>   in Box, 60 tests with -DBOX_INSTANCES=db_r_oc
>   in Octagonal_Shape, 58 tests with -DOCTAGONAL_SHAPE_INSTANCE=double
>   in BD_Shape, 59 tests with -DBD_SHAPE_INSTANCE=double

Hi Janis,

we investigated your report and found the culprit.  The immediate cause
is a bad interaction between Autoconf's AC_C_BIGENDIAN and
AX_PREFIX_CONFIG_H.  We reported this problem a few days ago, but did
not get any reply:

     http://www.cs.unipr.it/pipermail/ppl-devel/2009-January/013958.html

Perhaps AX_PREFIX_CONFIG_H is no longer maintained and we decided to
drop it starting from PPL 0.11.

Now, what happens is that AX_PREFIX_CONFIG_H fails to rename
WORDS_BIGENDIAN as PPL_WORDS_BIGENDIAN.  The PPL, however,
expects (only in three places, in src/Float.defs.hh) the
symbol PPL_WORDS_BIGENDIAN to be defined on big-endian machines
such as PowerPC.

A workaround is to configure the PPL for big-endian
architectures specifying

     CPPFLAGS="-UWORDS_BIGENDIAN -DPPL_WORDS_BIGENDIAN=1"

at the end of the configure command.  Can you please check
that that works?  If it does we will immediately publish
a notice on the PPL web site.

Taking into account that GCC 4.4 (via CLooG) does not use
any PPL feature depending on that miscompilation, I wonder
what is best.  Do you think we should prepare a PPL 0.10.1 release
with that fix?

Concerning how such a thing could have happened, the problem
is that we have access to only one PowerPC machine.  That machine
has memory problems so that a make of the PPL terminates with
a segmentation fault in GCC 90% of the times.  So, basically,
we currently have no sensible way to test on PowerPCs.  It is
a pity that this caused PPL 0.10 to be shipped with such a bug.
Thanks again for the problem report,

    Roberto

-- 
Prof. Roberto Bagnara
Computer Science Group
Department of Mathematics, University of Parma, Italy
http://www.cs.unipr.it/~bagnara/
mailto:bagnara at cs.unipr.it