On 29 August 2012 13:54, Roland Mainz <roland.ma...@nrubsig.org> wrote:
> [Forwarding since AT&T's spam filter is on drugs... ;-(( ]
> ---------- Forwarded message ----------
> From: ольга крыжановская <olga.kryzhanov...@gmail.com>
> Date: Wed, Aug 29, 2012 at 1:20 PM
> Subject: Re: [ast-developers] Fwd: Per thread open(), stat(), rename()
> and so on, and *at() API
> To: Lionel Cons <lionelcons1...@googlemail.com>
> Cc: Roland Mainz <roland.ma...@nrubsig.org>, ast-developers@research.att.com
>
>
> Lionel, there are 2 purposes:
>
> 1. Allow that ksh93/libshell can be embedded in other applications
> (Roland calls this 'back end usage', i.e. the user is not aware that
> he is interacting with a shell, and neither do any other apis know
> that, or at least should not have to know about that), with out
> interfering the calling application by changing the current working
> directory.
> 2. Allow that ksh93/libshell and the libast api can have a per thread
> current working directory.
>
> There are 2 proposals how to accomplish that:
> a) Add wrapper functions for open(), stat(), lstat(), chdir(),
> fchdir(), access(), eaccess(), rename() and so on, and redirect them
> to their *at() counterparts, with dirfd set to the current threads cwd
> fd.
>
> or
>
> b) Add wrapper cpp macros which redirect open(), stat(), lstat(),
> chdir(), fchdir(), access(), eaccess(), rename() and so on to their
> *at() counterparts, but define an extra macro which is AT_FDCWD for
> non threaded applications, and calls a function to obtain the current
> threads working directory fd for the current thread, but allows to
> override this macro on a per source file basis, so that applications
> like libshell, who maintain their own cwd directory fd, can use that.
>
> David and Glenn seems to prefer {a}, while I and Roland prefer {b},
> because {b} will allow an application to work as back end api without
> interfering with the global cwd or any other, may be libast based apis
> cwd. This includes nested usage of libshell, like for system() or
> wordexp().
I'd prefer option {b}, too. Strongly (sorry David and Glenn :)).
It sounds like the more sane and flexible way to do this. The big road
block is that you have to find a solution for old platforms which do
not have openat() and friends, or EOS (end-of-support) them (I'd
support that if no platform younger than four years lacks openat() and
friends).
Ced
--
Cedric Blancher <cedric.blanc...@googlemail.com>
Institute Pasteur
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