Message277036
I am cross compiling Python 3.5.2 for use on a 32-bit ARM processor with Linux. I use socket.CAN_EFF_FLAG and noticed that it is negative on the target despite being positive on my host (64-bit Intel Linux).
Host:
altendky@tp:~$ uname -a
Linux tp 4.4.0-31-generic #50-Ubuntu SMP Wed Jul 13 00:07:12 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
altendky@tp:~$ python3 --version
Python 3.5.2
altendky@tp:~$ python3 -c 'import socket; print(socket.CAN_EFF_FLAG)'
2147483648
^^ Is expected
Target:
root@rosi ~$ uname -a
Linux rosi 3.0.101-rt130-opusa3-2.1.0-2 #1 PREEMPT Tue Apr 12 13:49:26 CEST 2016 armv6l GNU/Linux
root@rosi ~$ /opt/epc/bin/python3 --version
Python 3.5.2
root@rosi ~$ /opt/epc/bin/python3 -c 'import socket; print(socket.CAN_EFF_FLAG)'
-2147483648
^^ Is not expected to be negative
Only CAN_EFF_FLAG reference in my source used to cross build Python:
Modules/socketmodule.c: PyModule_AddIntMacro(m, CAN_EFF_FLAG);
Definition in cross compiler include:
altendky@tp:/opt/freescale/usr/local/gcc-4.6.2-glibc-2.13-linaro-multilib-2011.12/fsl-linaro-toolchain/arm-fsl-linux-gnueabi/multi-libs/default/usr/include$ grep -r CAN_EFF_FLAG
linux/can.h:#define CAN_EFF_FLAG 0x80000000U /* EFF/SFF is set in the MSB */
For reference, here it is on the host system (looks the same to me):
altendky@tp:/usr/include$ grep -r CAN_EFF_FLAG
linux/can.h:#define CAN_EFF_FLAG 0x80000000U /* EFF/SFF is set in the MSB */
But perhaps this `long` type for the value is the issue? If signed and only 4-bytes as is the case on my target then this will misinterpret the 0x80000000U literal resulting in the above observed -2147483648.
PyModule_AddIntConstant(PyObject *m, const char *name, long value)
On my target system, printf("%d", sizeof(long)) yields 4.
For now I just work around it in my application by reassigning it to be it's absolute value.
socket.CAN_EFF_FLAG = abs(socket.CAN_EFF_FLAG) |
|
Date |
User |
Action |
Args |
2016-09-20 15:28:39 | altendky | set | recipients:
+ altendky |
2016-09-20 15:28:39 | altendky | set | messageid: <1474385319.74.0.546349288583.issue28215@psf.upfronthosting.co.za> |
2016-09-20 15:28:39 | altendky | link | issue28215 messages |
2016-09-20 15:28:39 | altendky | create | |
|