Hi, I would like add a new flag to open() mode to close the file on exec: "e". This feature exists using different APIs depending on the OS and OS version: O_CLOEXEC, FD_CLOEXEC and O_NOINHERIT. Do you consider that such flag would be interesting?
On Linux (glibc), the feature is available as the "e" flag for fopen() (O_CLOEXEC or FD_CLOEXEC depending on the kernel version). With Visual Studio, it's the "N" flag (O_NOINHERIT). I would like to modify open() to be able to benefit of O_CLOEXEC atomicity. The FD_CLOEXEC method has a race condition if another thread does fork() between open() and fcntl() (two calls to fcntl() are required). I created a patch available on the following issue: http://bugs.python.org/issue16850 Drawbacks of my idea/patch: - my patch raises NotImplementedError if the platform doesn't support close-and-exec flag. I tested Linux, OpenBSD, FreeBSD, OpenIndiana (Solaris) and Mac OS X: my patch works on all these platforms (except OpenBSD 4.9 because of an OS bug fixed in OpenBSD 5.2). I don't know platform without this flag. - my patch raises an error if opener argument of open() is used: opener and the "e" mode are exclusive (see the issue for details) --- I first proposed to only expose the atomic close-and-exec option, but only a few platforms (Linux 2.6.23+, FreeBSD 8.3+, Windows, QNX) support it. It's more convinient to have the best-effort method (only atomic if available). This article of Ulrich Drepper explain which kind of problem are solved by O_CLOEXEC: http://udrepper.livejournal.com/20407.html Victor _______________________________________________ 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
