Re: How to destroy _reent structure

[Sebastian Huber <sebastian dot huber at embedded-brains dot de>]

On 24/04/13 13:10, Sebastian Huber wrote:
> Hello Corinna,
>
> On 04/24/2013 12:26 PM, Corinna Vinschen wrote:
> > On Apr 24 10:04, Sebastian Huber wrote:
> > > Hello,
> > >
> > > there is _REENT_INIT_PTR() for initialization, but how can I destroy
> > > a _reent structure.  Is this _wrapup_reent()?
> >
> > Try _reclaim_reent.  But it's not the same as _REENT_INIT_PTR since
> > _REENT_INIT_PTR does not allocate any memory.
> >
> >
> > Corinna
>
> so for initialization we can use:
>
> struct _reent *p = malloc(sizeof(*p));
> if (p != NULL) {
>   _REENT_INIT_PTR(p);
> }
>
> For destruction we can use:
>
> _reclaim_reent(p);
> free(p);

If I use this sequence in RTEMS, then I have the following problem. 
RTEMS opens (via open()) the file descriptors 0, 1 and 2 during system 
initialization.  In RTEMS the file descriptors are a global resource.  A 
thread will do the initialization steps above during creation time.  Now 
suppose a thread calls fopen().  This will check that _REENT is 
initialized.  This will execute the following code for stdin, stdout and 
stderr FILE streams (newlib/libc/stdio/findfp.c):

[...]
static _VOID
_DEFUN(std, (ptr, flags, file, data),
            FILE *ptr _AND
            int flags _AND
            int file  _AND
            struct _reent *data)
{
[...]
  ptr->_file = file;
[...]
  ptr->_close = __sclose;
[...]
}
[...]

It simply assumes that file descriptors 0, 1 and 2 are available and 
registers the __sclose() function (which will call close()).  During 
_reclaim_reent() the stdin, stdout and stderr FILE streams are closed.  
Since we have no open() call for these file descriptors this will close 
the global file descriptors 0, 1 and 2.  I think at least for RTEMS we 
should set ptr->_close to NULL.

> What is the purpose of _wrapup_reent()?  Its not called from within 
> Newlib and I don't find a function that can register an atexit handler 
> in a non-global _reent structure.  There is also no public header file 
> for this function.

I think we should move the _wrapup_reent() into a separate file.

--
Sebastian Huber, embedded brains GmbH

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