From: Joshua Juran <jjuran@gmail.com>
Date: Thu, 26 Aug 2010 07:16:06 GMT
Subject: Re: setting working dir in posix_spawn() (Re: Fix 'git log' early pager startup error case)
Message-ID: <65AAB642-0AEB-40F3-8C33-81AA2C110D3E@gmail.com>
In-Reply-To: <20100826061815.GH9708@burratino>

On Aug 25, 2010, at 11:18 PM, Jonathan Nieder wrote:

> Eric Blake wrote:
>> On 08/25/2010 01:00 AM, Johannes Sixt wrote:
>
>>> Just FYI, posix_spawn() is not sufficiently capable for the  
>>> demands of
>>> start_command(): It doesn't allow to set a new CWD for the spawned  
>>> process.
>>
>> And even if posix_spawn() were capable, cygwin doesn't yet  
>> implement it.
>
> Hmm, okay.  You have access to win32api, though, right?  So it should
> be possible to reuse code from compat/mingw.c::mingw_spawnvpe.
>
> Do you think there would be any interest in a posix_spawn() variant
> that takes a dir parameter?

Another option would be a variant of vfork() where munging file  
descriptors, cwd, etc. prior to exec is well defined.  In Lamp (Lamp  
ain't Mac POSIX), vfork() does this already; in Linux you'd just use  
fork().  The problem is that currently no common interface exists  
which guarantees behavior which is both sufficient and cheap --  
vfork() promises nothing at all, and fork() is expensive (if available  
at all) on some platforms, guaranteeing much more than is often needed.

It would be useful to have something in between vfork() and fork(),  
though I'm not sure what it should be called.

Josh