Memory reclaim errors

Memory reclaim errors

[Nick French]

We currently have a problem that when we tidy up a task that exists we
get memory problems due to the fact that we clear memory that is
within newlibs global file handles. The build of newlib that we do is
nano.

We have tracked down an error to what I believe is the following function.

/*
 * Find a free FILE for fopen et al.
 */

FILE *
__sfp (struct _reent *d)
{
  FILE *fp;
  int n;
  struct _glue *g;

  _newlib_sfp_lock_start ();

  if (!_GLOBAL_REENT->__sdidinit)
    __sinit (_GLOBAL_REENT);
  for (g = &_GLOBAL_REENT->__sglue;; g = g->_next)
    {
      for (fp = g->_iobs, n = g->_niobs; --n >= 0; fp++)
        if (fp->_flags == 0)
          goto found;
      if (g->_next == NULL &&
          (g->_next = __sfmoreglue ( d, NDYNAMIC)) == NULL)
        break;
    }
  _newlib_sfp_lock_exit ();

The line below causes us to free the memory as it is assigned to the
current thread

(g->_next = __sfmoreglue ( d, NDYNAMIC)) == NULL)

changing the local thread to global as below fixes it and the file
handle get reused

(g->_next = __sfmoreglue (_GLOBAL_REENT, NDYNAMIC)) == NULL)

Any comments on our assumptions are appreciated.

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Re: Memory reclaim errors

[Sebastian Huber]

Hello Nick,

On 01.05.23 00:52, Nick French wrote:
> The line below causes us to free the memory as it is assigned to the
> current thread
> 
> (g->_next = __sfmoreglue ( d, NDYNAMIC)) == NULL)
> 
> changing the local thread to global as below fixes it and the file
> handle get reused
> 
> (g->_next = __sfmoreglue (_GLOBAL_REENT, NDYNAMIC)) == NULL)
> 
> Any comments on our assumptions are appreciated.

does this mean the memory allocator used for

static struct _glue *
sfmoreglue (struct _reent *d, int n)
{
   struct glue_with_file *g;

   g = (struct glue_with_file *)
     _malloc_r (d, sizeof (*g) + (n - 1) * sizeof (FILE));
   if (g == NULL)
     return NULL;
   g->glue._next = NULL;
   g->glue._niobs = n;
   g->glue._iobs = &g->file;
   memset (&g->file, 0, n * sizeof (FILE));
   return &g->glue;
}

somehow supports thread-specific memory which is automatically freed 
when the associated thread is terminated?

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