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On 05/02/2013 09:36 PM, Jeff Johnston wrote:
I would like to change this.

I don't like having a macro that takes a ptr argument and ignores it.  I also
would prefer consistency with the impure ptr struct declarations. The atexit0
storage is supposed to be statically guaranteed which is currently accomplished
by being part of the static global reent struct.

The problem is that with the current struct _reent you have per-reent atexit support. I don't know if this is used in code outside of Newlib by some system. You can for example add your own my_thread_atexit() which registers atexit() handlers in the thread-local reent which are called during thread delete via my_thread_delete_call_atexit(). The patch will be simpler if we accept to break such systems.

My preference is that you declare a static atexit0_data struct inside impure.c
along-side the impure_data declaration (being controlled by your new

If we place it in impure.c, then we need this space even if nobody calls atexit().

Then, you have two macros:

_GLOBAL_ATEXIT  (which is either _GLOBAL_REENT->_atexit or _impure_atexit
(whatever you call it), which is also declared in impure.c based on the


_GLOBAL_ATEXIT0 (which is either &(_GLOBAL_REENT->_atexit0) or the address of
_impure_atexit0_data or whatever you put in impure.c for atexit0).

It becomes relatively straightforward after that to change the existing code.

In _reclaim_reent() we have "&ptr->_atexit0". Changing this to "&(_GLOBAL_REENT->_atexit0" alters the behaviour.

I probably would not have bothered moving the _atexit pointer out of the struct
myself since it is such a minor gain compared to the atexit0 savings but whatever.

Yes, it saves only some bytes, but this enforces that the atexit() support is no longer potentially thread-local.

Sebastian Huber, embedded brains GmbH

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