Python on Altix (re-cap)
jmiller at stsci.edu
Wed Oct 8 21:20:23 CEST 2003
Todd Miller wrote:
> I'm trying to set up Python on a 64-bit Linux super computer which looks
> like this:
> Linux somewhere.in.au 2.4.20-sgi221r3 #1 SMP Tue Jul 22 15:32:18 PDT
> 2003 ia64 unknown
> I configure Python like this:
> ./configure --prefix=$HOME --with-pydebug --without-threads
> But as soon as I try to run my software self-tests (for the numarray
> Numeric-like array package), I get this:
> python(11030): unaligned access to 0x60000fffffff61cc,
This message is apparently a kernel level debug message. It is not on
stdout or stderr. This message went away when I switched off
> Debug memory block at address p=0x6000000000718310:
> 88 bytes originally requested
> The 4 pad bytes at p-4 are FORBIDDENBYTE, as expected.
> The 4 pad bytes at tail=0x6000000000718368 are not all FORBIDDENBYTE
> at tail+0: 0x02 *** OUCH
> at tail+1: 0x00 *** OUCH
> at tail+2: 0x00 *** OUCH
> at tail+3: 0x00 *** OUCH
> The block was made by call #0 to debug malloc/realloc.
> Data at p: 00 00 00 00 00 00 00 00 ... 01 00 00 00 00 00 00 00
> Fatal Python error: bad trailing pad byte
> Abort (core dumped)
This message was related to a bug in the numarray setup.py. Once I
configured numarray for LP64=1, it disappeared.
Interestingly, there is no discernable difference between the
sys.platform of i386 Linux and the sys.platform of a 64-bit x86 Linux;
they are both "linux2". I worked around this by adding a branch based
on sys.maxint > 2**31-1 to distinguish between 32 and 64 bit linux.
I fixed a total of 3 other bugs in numarray, one out-and-out bug, one
64-bit self-test issue, and one C type casting portability issue.
> I've poked around with this for a few hours, but I'm not getting much
> out of GDB. Does anyone have any suggestions on how to get Python up
> and running on an Altix or how to solve this problem more generally?
Even with Skip's suggestion to use watchpoints, I still had poor luck
with GDB compared to 32-bit Linux. I did learn the *<hex_address>
syntax for specifying addresses rather than symbolic names for
breakpoints and watchpoints.
With pydebug switched on, numarray still dumps core (on exit?) like this:
python: Modules/gcmodule.c:231: visit_decref: Assertion `gc->gc.gc_refs
!= 0' failed.
With pydebug off, all is quiet and all the numarray self-tests now pass.
> Please CC me if you respond.
Thanks again for the pointers.
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