Optimizing of explicit temporary storage

[Mark Mitchell]

Florian Weimer wrote:

>* Mark Mitchell:
>
>  
>
>>I don't think any compiler has ever attempted to turn:
>>
>> free (malloc (16));
>>
>>into a no-op, which would be a simpler case.
>>    
>>
>
>There are scheme compilers that turn heap allocation into stack
>allocation if they can prove that the object does not escape.
>Java code would benefit from this optimization, too.
>  
>
Yes, but that's rather a different situation due to the nature of Scheme.

In C, even given just:

  (void) malloc(16);

it would be surprising to most programmers to optimize away the call 
because malloc *does* have side-effects on real systems.  For example, 
on UNIX, it is likely to call sbrk, which result in observable changes 
in the process state.

-- 
Mark Mitchell
CodeSourcery, LLC
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mark@codesourcery.com