atexit() stuff in thread-local reent?

[Sebastian Huber]

On 04/29/2013 11:26 PM, Jeff Johnston wrote:
> 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.

This is a good solution.  I will provide a patch for this in the next couple of 
days.

-- 
Sebastian Huber, embedded brains GmbH

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