Description:

The code in the struct module assumes that sizeof(long)
== sizeof(int)
which is wrong on (most) 64-bit architectures (linux on
amd64 with a 32-bit userland is an exception). 


How To Repeat:

on a 32-bit platform struct.pack behaves as expected:

$  uname -m  -r  -s
FreeBSD 4.10-STABLE i386
$ python -c "import struct; print repr(struct.pack('I',
4294967296))"
Traceback (most recent call last):
  File "<string>", line 1, in ?
OverflowError: long int too large to convert

on a 64-bit platform it treats integers as longs 
(it does not check for over/underflows and returns the
lower 4 byte): 

$ uname -m  -r  -s
FreeBSD 5.2-CURRENT sparc64
$ python -c "import struct; print repr(struct.pack('I',
4294967296))" 
'\x00\x00\x00\x00'


Fix:

in python/python/dist/src/Modules/structmodule.c:
np_uint() and np_int() have to check for 
over/underflows using MAX_UINT, MAX_INT, MIN_INT  as
np_ushort() and np_short() already do for MAX_USHORT, ...

the attached patch does this
(diff was generated using diff -rNu and  Revision 2.62
of python/python/dist/src/Modules/structmodule.c)