On Tuesday, 29 October 2013 at 19:29:12 UTC, Andrei Alexandrescu
wrote:
On 10/29/13 11:34 AM, Vladimir Panteleev wrote:
On Tuesday, 29 October 2013 at 03:44:37 UTC, Andrei In
addition to what Lars said, I'd like to add that replacing the
current process is a rather platform-dependent trick. While
process
creation in POSIX is done by forking then replacing the forked
process
with a new one, on Windows it's the other way around - created
processes
are always isolated from the current one, and Windows
implementations of
this function simply emulate the behavior by creating a new
process,
then terminating the current one.
[...]
That argument doesn't seem to hold water. So if Windows does it
less efficiently than Linux, we should... remove the option
altogether so we level the field?
It's not just that it does it less efficiently. What's worse is
that it does it *differently*. While I don't have a Windows
machine available to test this, I've done some research, and it
seems the effect of calling _exec*() on Windows is *exactly* as
if a new process was created and the parent process exited. In
other words, the child process starts in the "background" (with a
new PID), and the parent process returns control to the program
which called it (such as cmd.exe).
Furthermore, Windows' exec*() functions do not handle program
names with spaces well.
Apparently, Python has included support for the exec*()
functionality on all platforms, which has led to several bug
reports:
http://bugs.python.org/issue9148
http://bugs.python.org/issue19066
http://bugs.python.org/issue19124
These were only the ones that came up in my first Google search.
The answer from the Python team to all of them seems to be "don't
use exec on Windows". StackOverflow users agree:
http://stackoverflow.com/q/7004687
http://stackoverflow.com/q/7264571
I suspect that these functions were only included in Windows to
satisfy POSIX requirements (which they fail to do).
We should discourage their use on Windows, and one way to do this
is to *not* have a nice cross-platform interface to them in
Phobos.
Lars
