[phobos] Suggestions for std.process

[Andrei Alexandrescu]

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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