[Python-Dev] PEP 446: Open issues/questions (original) (raw)

Victor Stinner victor.stinner at gmail.com
Mon Jul 29 23:42:36 CEST 2013

2013/7/28 Charles-François Natali <cf.natali at gmail.com>:

2013/7/28 Antoine Pitrou <solipsis at pitrou.net>:

(C) Should we handle standard streams (0: stdin, 1: stdout, 2: stderr) differently? For example, os.dup2(fd, 0) should make the file descriptor 0 (stdin) inheritable or non-inheritable? On Windows, os.setinheritable(fd, False) fails (error 87, invalid argument) on standard streams (0, 1, 2) and copies of the standard streams (created by os.dup()).

I have been advocating for that, but I now realize that special-casing these three descriptors in a myriad of fd-creating functions isn't very attractive. (if a standard stream fd has been closed, any fd-creating function can re-create that fd: including socket.socket(), etc.)

So perhaps only the original standard streams should be left inheritable?

I plan to only change functions creating (and replacing) new file descriptors. Existing file descriptors (like 0, 1, 2) are unchanged.

Having stdin/stdout/stderr cloexec (e.g. after a dup() to redirect to a log file, a socket...) will likely break a lot of code, e.g. code using os.system(), or code calling exec manually (and I'm sure there's a bunch of it).

I propose to add just one special case os.dup2(fd, fd2): if fd2 < 3, fd2 is set to inheritable (otherwise, fd2 is set to non-inheritable). os.dup2() is commonly used to replace stdin, stdout and stderr between fork and exec. The http.server (cgi server) and pty modules use dup2() for example

http://hg.python.org/features/pep-446/rev/f8a52518be4c

Victor

More information about the Python-Dev mailing list