Re: [Twisted-Python] [andrea@cpushare.com: Re: error after launching cpushare client]

Aug. 4, 2005


      On Thu, Aug 04, 2005 at 08:47:39AM +0300, Tommi Virtanen wrote:
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Andrea Arcangeli wrote:
...
Ok but then do you have an idea where the 139 comes from? I'd like to
understand what's going on, to me that 139 number comes out of the blue.
139 == 128 + 11.
One way to set up the numbering is that exit codes are 0..127, signals
etc. have hight bit set.
Naturally, all real access should go through the macros WIFEXITED etc,
but that's how the number ranges are classically set up.
Ah, I think I got why he gets 139, that's because the core dumping was
enabled.
...
...
...
Actual .status values are unportable, thus transferring them raw over
the network is not a good idea.
status should be the same that waitpid returns, from the docs:
"return a tuple containing its pid and exit status indication: a 16-bit
number, whose low byte is the signal number that killed the process, and
whose high byte is the exit status (if the signal number is zero); the
high bit of the low byte is set if a core file was produced.
Availability: Unix."
I think you are reading about os.wait and twisted is using
os.waitpid. Otherwise, the document is lying to you. The status _may_ be
Yes, the status is the same in wait and waitpid, and it's the same as
well in C (I doubt that python does any mangling of the C value).
...
laid out like that on _some_ platform, but unless python does some
readjustment, the only portable way to access it is WIFEXITED and
friends.
It's not like I've an huge portability, because seccomp currently
only available on linux, but I'll follow your suggestion and I'll try to
make it more portable.
...
cat >crash.c <<EOF
int main(void) {
  /* comment out the next line if you want a normal exit */
  *(char*)0 = 42;
  return 34;
}
EOF
cat >run.py <<EOF
#!/usr/bin/python
import os
pid = os.fork()
if pid:
    # parent
    pid, status = os.waitpid(pid, 0)
    print pid, status
    if os.WIFEXITED(status):
        print 'exited', os.WEXITSTATUS(status)
    elif os.WIFSIGNALED(status):
        print 'signaled', os.WTERMSIG(status)
        print 'coredump', os.WCOREDUMP(status)
    elif os.WIFSTOPPED(status):
        print 'stopped', os.WSTOPSIG(status)
    elif os.WIFCONTINUED(status):
        print 'continued'
    else:
        print 'unknown'
else:
    # child
    os.execv('./a.out', ['a.out'])
    raise RuntimeError, "exec failed"
EOF
chmod a+x run.py
gcc -Wall crash.c
./run.py
Ok thanks a lot for the example.
...
Exactly. If a process exits due to a signal, there is no exit code in
the sense of calling _exit(2).
Ok, same as with C.