[Python-Dev] ia64 debian buildbot

["Martin v. Löwis"]

Thomas Heller wrote:
> Why does the ia64 debian buildbot now complain about unaligned accesses,
> and how can we find out where they occur?

I don't know why they started show up suddenly; on Debian-Itanium, it
is a configuration option (even per process, through prctl(1)) whether
they just produce a log message, or a signal, or nothing; if they
produce a log message, this also goes to the process' terminal.

These unaligned access must have been there for some time now;
perhaps something on the machine has changed. Matthias?

Finding where they originate from is really hard. You need to
set the process into the "signal unaligned access" mode, and
then run it under a debugger, so you know where it crashes.
This requires shell access to the machine.

I have tried to reproduce it on my Itanium machine, and found that
that they come from the AST compiler's arena (I /knew/ it was
wrong to implement your own memory management algorithms :-): it
was returning memory blocks that were only 4-aligned, so the
the pointers in the ASDL sequences were all unaligned; hence the
errors.

I changed that to always guarantee 8-alignment for all blocks
returned from the arena; that seems to help.

Regards,
Martin