On 06Jul2013 14:43, Victor Stinner <victor.stin...@gmail.com> wrote: | 2013/7/6 Cameron Simpson <c...@zip.com.au>: | > Yes. Please forget I mentioned fork(); it is only relevant if you | > were offering some facility to undo the addition of cloexec to a | > Popen passed file descriptor. Which you are not. | | Oh... gotcha. I now understood your concern. | | There is a little "trick" here: at fork, file descriptors are | duplicated in the child process and almost all properties (open state, | flags, offset, etc.) are shared. There is one little exception: file | attributes are not shared, and there is only one file attribute: | O_CLOEXEC. Setting O_CLOEXEC in a child process does not affect the | flag in the parent process ;-) I will add a unit test to check this.
That's news to me. Interesting. I can't find UNIX doco to support this, though I haven't finished looking. None of the POSIX, Linux or MacOSX fork() manual pages seem to describe this. Can you point me at doco for this? I thought file descriptors were a direct index into a per-process table of file handle structures, and did not think the latter got part copies, part shared over a fork. Also, is O_CLOEXEC really the only file attribute? So O_NONBLOCK is a flag and not an attribute (guessing the terminology distinguishes these)? Now you mention it, ISTR noticing that there were distinct ioctls to adjust flags and something else. | I modified the PEP to explain that, and I also mentioned the name of | the close-on-exec and blocking flags: | http://hg.python.org/peps/rev/425f831fddf7 Thanks. Your change says: On Windows, the close-on-exec flag is ``HANDLE_FLAG_INHERIT``. I feel it would be clearer to say: On Windows, the close-on-exec flag is the inverse of ``HANDLE_FLAG_INHERIT``. or On Windows, the close-on-exec flag implemented using ``HANDLE_FLAG_INHERIT``. (This latter is fine because the rest of the paragraph explains the meaning of HANDLE_FLAG_INHERIT.) The bare "is" in your current wording suggests to me that the truthiness (ick!) of close-on-exec is the same as for HANDLE_FLAG_INHERIT, which it isn't. -- Cameron Simpson <c...@zip.com.au> I've always been a big Greenaway fan - I've seen and enjoyed "The Falls" for crying out loud. - Peter Alexander Merel <p...@extro.ucc.su.oz.au> _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
