Execution of "make test" for Python 2.6.1 halts with a segmentation 
fault on line 2198 of Python-2.6.1/Lib/test/test_datetime.py; also 
occurs using the attached script, narrowing it down to the %z sequence 
in the format argument to datetime.time.strftime(), but only when the 
time object has a non-None tzinfo.  The segfault disappears when I 
comment out line 1133 of Python-2.6.1/Modules/datetimemodule.c:

PyOS_snprintf(buf, buflen, "%c%02d%s%02d", sign, hours, sep, minutes);

Compiled with GCC 3.4.3 with Smashing Stack Protector on LFS 5.1.1 
(Linux 2.6.11.12 and glibc 2.3.5 with ssp patches).  Using BASECFLAGS=-
fno-stack-protector has no effect on the segfault.  All other Python 
tests pass.  HAVE_SNPRINTF has been defined to 1 in pyconfig.h by the 
config script.

I have not yet compiled gdb, but I can if requested.

Update: Undefining HAVE_SNPRINTF does not correct the problem.

Can you debug this problem any further?  What is the C call stack?  Does
the problem occur if you build in debug mode (./configure
--with-pydebug)?  Does the problem occur with a different compiler (if
you have access to another one on the same box)?

I can reproduce this problem with Gentoo Hardened and 
gcc version 3.4.6 (Gentoo Hardened 3.4.6-r2 p1.6, ssp-3.4.6-1.0, pie-8.7.10)

when gdb-ing through the datetimemodule.c, and displaying the "tuple"
variable in time_strftime, I can see that the pointer gets modified by
the wrap_strftime call, resulting in Py_DECREF causing the segfault:
before wrap_strftime:
(gdb) x tuple
0xa8938f2c:	0x00000001
after wrap_strftime:
(gdb) x tuple
0x938f2c:	Cannot access memory at address 0x938f2c
thus executing
Py_DECREF(tuple)
results in the segfault.

@belopolsky: unittest exists, 
/usr/lib/python2.6/test/test_datetime.py
as mentioned by the OP, this unittest reproduces
the issue.

Philipp,

Why do you think you see the same problem as Eric?

Can you set a trace on &tuple and see when it gets modified?

Do you see the crash with zone_failure.py, test_datetime.py or both?

Unfortunately, I'm no longer able to reproduce this issue as I upgraded to gcc 4.3 sometime within the last nine months...
With 4.3, I don't see this segfault any longer.

Since this does not seem to be reproducible anymore, I am going to close this soon.

Reproduced again in version 2.7rc2; I had thought that it went away, but it turns out that --with-pydebug hides the problem.

Compiling GDB now.

Since no one is able to reproduce this crash, I am going to close this issue.