Re: [PATCH 2/6] Open a directory with the usual flags

Corinna Vinschen <[email protected]> Wed, 10 Oct 2018 13:35:49 +0200

Newsgroups	gmane.comp.lib.newlib
Message-ID	<[email protected]>

On Oct 10 13:16, Sebastian Huber wrote:
> On 10/10/2018 11:50, Corinna Vinschen wrote:
> > On Oct  8 15:38, Sebastian Huber wrote:
> > > Use O_RDONLY since you are not supposed to write to a directory.
> > > 
> > > Use O_DIRECTORY as mandated by POSIX (The Open Group Base Specifications
> > > Issue 7, 2018 edition IEEE Std 1003.1-2017):
> > > 
> > > "If the type DIR is implemented using a file descriptor, the descriptor
> > > shall be obtained as if the O_DIRECTORY flag was passed to open()."
> > > 
> > > Use O_CLOEXEC as mandated by POSIX:
> > > 
> > > "When a file descriptor is used to implement the directory stream, it
> > > behaves as if the FD_CLOEXEC had been set for the file descriptor."
> > > 
> > > Drop the fcntl() call in favour of O_CLOEXEC.
> > Yeah, that really makes sense, but what about targets not (yet)
> > implementing O_CLOEXEC???  I'm not sure how to handle this, if
> > we have to handle that at all.
> 
> In RTEMS there are no processes (fork(), exec(), etc. don't work). So, it is
> trivial to support the O_CLOEXEC. The situation in which this flag is
> relevant simply cannot happen.
> 
> Are Cygwin and Linux the only Newlib systems which supports processes?

I really don't know, but the other problem is to use a flag in a target
dependent call which might be unsupported, but tested.  This is backed
by POSIX allowing open to return EINVAL for invalid flags.

We should probably define _FNOINHERIT only on targets known to support
it (even if trivially) and to call open(O_CLOEXEC) or fcntl() depending
on that test, no?


Corinna

-- 
Corinna Vinschen
Cygwin Maintainer
Red Hat

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