[phobos] Suggestions for std.process

[Sean Kelly]

Right.  Upon reflection the best approach is probably just to launch a thread to block on wait().  It won't consume any CPU cycles waiting anyway.

On Mar 8, 2010, at 1:08 PM, Andrei Alexandrescu wrote:

> Like Sean, I don't think going with SIGCHILD is a good idea. It's not only about thread safety, but mostly about reentrancy of system functions.
> 
> Andrei
> 
> Lars Tandle Kyllingstad wrote:
>> I didn't even think of that, but you're right, of course.  The parent gets a SIGCHLD when the child terminates.  I wonder if it's possible to restrict the callback so that it's safe to call it from a signal handler?  It would have to be nothrow, that's for sure, but that's probably not enough.  It is all too easy to make thread-unsafe code with signal handlers.  Is it possible to mark functions or delegates with 'shared', so they only operate on shared data?
>> -Lars
>> Sean Kelly wrote:
>>> In *nix you can set a signal handler to be notified when a child process completes.  But the restrictions on what can be done inside a signal handler are such that maybe executing a callback from inside one isn't a good idea anyway.
>>> 
>>> On Mar 8, 2010, at 12:22 AM, Lars Tandle Kyllingstad wrote:
>>> 
>>>> I don't know any way of doing this besides spawning a separate thread that a) starts the process, b) waits for it to complete, and c) calls the callback function/delegate.
>>>> 
>>>> Is this what you had in mind?
>>>> 
>>>> -Lars
>>>> 
>>>> 
>>>> Sean Kelly wrote:
>>>>> I'm not sure if this is supported in Windows, but if so, it might be nice if I could set a callback that would be executed when the process completes.
>>>>> On Mar 3, 2010, at 9:44 AM, Lars Tandle Kyllingstad wrote:
>>>>>> Hi,
>>>>>> 
>>>>>> Recently, I found myself in need of the functionality that is (or should have been) in std.process, but unfortunately I found it lacking in many respects.  Assuming that improving it currently isn't at the top of the to-do list for Phobos, I decided not to wait, and rather to write my own version.  If you want you can check it out here:
>>>>>> 
>>>>>> Code:   http://github.com/kyllingstad/ltk/blob/master/ltk/process.d
>>>>>> Docs:   http://kyllingen.net/code/ltk/doc/process.html
>>>>>> 
>>>>>> I don't know if any of it is usable for Phobos, but if it is, I'd be happy to contribute.
>>>>>> 
>>>>>> I've tried to write it in the style of std.concurrency, with a function spawnProcess() that returns a Pid struct.  Currently it is for POSIX only, since I have no experience at all with the Windows API.
>>>>>> 
>>>>>> -Lars
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>>>> -- 
>>>> Lars Tandle Kyllingstad
>>>> @: lars at kyllingen.net
>>>> #: 40233221
>>>> w: http://www.kyllingen.net
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