forks/pipes and std.socket

[Steven Schveighoffer]

On Tue, 07 Sep 2010 16:51:48 -0400, Nick Sabalausky <a at a.a> wrote:

> "Steven Schveighoffer" <schveiguy at yahoo.com> wrote in message
> news:op.vioibdr2eav7ka at localhost.localdomain...
>> On Tue, 07 Sep 2010 14:54:46 -0400, Nick Sabalausky <a at a.a> wrote:
>>
>>> "Kagamin" <spam at here.lot> wrote in message
>>> news:i660qi$nud$1 at digitalmars.com...
>>>> Nick Sabalausky Wrote:
>>>>
>>>>> Does anyone who's done this sort of thing in D before, on Win or Lin,
>>>>> know
>>>>> of anything else in particular to be aware of?
>>>>
>>>> There's no fork on windows. If you want a multithreaded server, it's
>>>> usually implemented with threads on windows.
>>>
>>> That was just an example. CreateProcess/spawn/system are fine for my
>>> purposes. I'm just talking about creating a child process and
>>> communicating
>>> with it via pipes.
>>
>> The upcoming std.process changes will make this easy.
>>
>
> Ah cool, looking forward to it. I was just about ready to launch into a
> bunch of std.process improvements myself ;) In the meantime, it seems  
> that
> File has an undocumented constructor that takes a file handle instead of  
> a
> filename, so that should work for me.

Beware, it takes a file *descriptor*, which is different from a *HANDLE*  
on windows.  In writing the updated std.process I had to write D code that  
mimics the internals of DMC's runtime in order to translate between file  
descriptors and handles, not a pretty sight...

The updates are being held back right now by bug 3979.

> BTW, do any of the upcoming std.process changes do anything to help work
> around Windows's exec being broken? By that I mean, exec is supposed to
> *reuse* the current process when launching the new one, but on Windows  
> (and
> I *don't* believe this is D-specific) it creates a *new* process and  
> kills
> the old one, which fucks up anything that waits on the original process  
> to
> finish (such as the command-line). spawn(OVERLAY) has the same problem.

Windows' exec is a hack.  std.process will not use it, instead, we'll use  
CreateProcess directly.

FWIW, we are not going to support fork or exec individually in  
std.process.  We will only support creating a new process via fork+exec or  
CreateProcess.  This is the common functionality among OSes.

If you want fork or exec individually, you have to use them on posix  
systems only, and call them directly.

-Steve