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NULL call to _Workspace_Free() via _Objects_Extend_information at startup



On 03/01/2011 09:05 AM, Peter Dufault wrote:
> 
> On Mar 1, 2011, at 2:44 , Sebastian Huber wrote:
> 
>> do you experience this behavior with the debug variant of RTEMS or with the
>> normal configuration?
> Debugging enabled.
>>
>> A call to _Heap_Free(NULL) must return true.
> 
> You mean a call to _Heap_Free(heap_control, NULL) must return true.  Fine, someone must update the interface documentation to add that requirement.
> 
> Just to be a trouble-maker, what should these functions return given a NULL heap block pointer?  Currently it is unspecified.

Yes, currently it is unspecified, and in fact we return false for a very long
time.  Returning false makes no sense from my point of view.  On the other hand
we don't care much about the return value currently.  For example free() does a
NULL check itself.  The _Heap_is_block_in_heap() rejects a NULL.

You encountered a bug in _Heap_Protection_block_check_default() which should
check for NULL as a special case.

> 
> _Heap_Block_size(block), _Heap_is_free(block), _Heap_is_block_in_heap(const Heap_Control *heap, const Heap_Block *block).
> 
> Ideally the definition should be derived from a concise definition of what a NULL heap block pointer means, and those operations that are undefined should be specified as undefined.
> 
> One could argue that _Heap_Block_size(0) == 0, _Heap_is_free(0) == true, _Heap_is_block_in_heap(0, *) == true.  I'm not arguing it, though, since I'm not presenting the "concise definition" I mention above.

These are all internal heap functions.  They must work only with pointers to an
allocated area.

> 
> Peter
> -----------------
> Peter Dufault
> HD Associates, Inc.      Software and System Engineering
> 


-- 
Sebastian Huber, embedded brains GmbH

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