atexit() stuff in thread-local reent?

[Jeff Johnston]

On 04/27/2013 07:52 AM, Sebastian Huber wrote:
> Hello,
>
> currently the struct _reent contains some atexit() stuff:
>
> struct _reent {
>    [...]
>    /* atexit stuff */
>    struct _atexit *_atexit;
>    struct _atexit _atexit0;
>    [...]
> };
>
> on PowerPC for example this accounts for 400 of 1088 bytes of the
> structure.  From my point of view the atexit() stuff belongs to the
> global state and is not thread-specific.  I think all atexit() related
> functions (in __call_atexit.c and  __atexit.c, are there more?) use
> _GLOBAL_REENT.  This is related to the possibly unused _wrapup_reent()
> function.  Maybe we should introduce two structures.  One for the global
> state (contains thread-specific state + atexit() stuff) and one for the
> thread-specific state.  This might save 400 bytes (37% of current
> _reent) per thread.
>

Instead, I might suggest that _atexit0 be removed from struct _reent and 
we simply declare a variable in reent/impure.c which is _global_atexit0 
and add a define which is _GLOBAL_ATEXIT0.  The __atexit.c can be 
changed to use _GLOBAL_ATEXIT0 instead of _GLOBAL_REENT->_atexit0.

-- Jeff J.