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PEP 446: enhance the Rationale to take into account Cameron Simpson's remarks 

* mention the name of the close-on-exec flag: HANDLE_FLAG_INHERIT, O_CLOEXEC
 * mention the name of the blocking flag: O_NONBLOCK
 * explain that file attributes are duplicated at fork
This commit is contained in:
Victor Stinner 2013-07-06 14:27:23 +02:00
parent eb13cfaa28
commit b4738085d0
1 changed files with 21 additions and 7 deletions
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28
pep-0446.txt
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@ -27,14 +27,25 @@ The inheritance of file descriptors in child processes can be configured
on each file descriptor using a *close-on-exec* flag. By default, the
close-on-exec flag is not set.
On Windows, file descriptors are not inherited if the
``bInheritHandles`` parameter of the ``CreateProcess()`` function is
``FALSE``, even if the close-on-exec flag is not set.
On Windows, the close-on-exec flag is ``HANDLE_FLAG_INHERIT``. File
descriptors are not inherited if the ``bInheritHandles`` parameter of
the ``CreateProcess()`` function is ``FALSE``, even if the
``HANDLE_FLAG_INHERIT`` flag is set. If ``bInheritHandles`` is ``TRUE``,
only file descriptors with ``HANDLE_FLAG_INHERIT`` flag set are
inherited, others are not.
On UNIX, the close-on-exec flag is ``O_CLOEXEC``. File descriptors with
the ``O_CLOEXEC`` flag set are closed at the execution of a new program
(ex: when calling ``execv()``).
The ``O_CLOEXEC`` flag has no effect on ``fork()``, all file descriptors
are inherited by the child process. Futhermore, most properties file
descriptors are shared between the parent and the child processes,
except file attributes which are duplicated (``O_CLOEXEC`` is the only
file attribute). Setting ``O_CLOEXEC`` flag of a file descriptor in the
child process does not change the ``O_CLOEXEC`` flag of the file
descriptor in the parent process.
On UNIX, file descriptors with the close-and-exec flag set are closed at
the execution of a new program (ex: when calling ``execv()``). The flag
has no effect on ``fork()``, all file descriptors are inherited by the
child process.
Issues of the inheritance of file descriptors
---------------------------------------------
@ -62,6 +73,9 @@ operation would block.
By default, newly created sockets are blocking. Setting the non-blocking
mode requires additional system calls.
On UNIX, the blocking flag is ``O_NONBLOCK``: a pipe and a socket are
non-blocking if the ``O_NONBLOCK`` flag is set.
Setting flags at the creation of the file descriptor
----------------------------------------------------