pure / const on function "return"ing an array?

[Kevin P. Fleming]

On 01/17/2011 05:56 PM, Jonathan Wakely wrote:
> On 17 January 2011 23:04, tom fogal wrote:
>> I have a function with this prototype:
>>
>>   void to_3d(hsize_t index, const hsize_t dims[3], hsize_t outdex[3]);
>>
>> The effect of the function is to store appropriate values in the
>> "outdex" array.  It does not read or write global memory.
>>
>> I would like to mark this as __attribute__((const)), but it doesn't
>> quite fit the definition, as it's a void function.  Obviously I can't
>> just change it to make `outdex' the return value, since outdex is an
>> array.
>
> Isn't outdex actually a pointer? That's another reason the function
> can't be marked const.

It's a pointer, but the pointer is caller-provided, so I would think the 
compiler could make a reasonable assumption that it "knows" the only 
memory locations the called function is going to be able to modify if it 
is marked 'const'.

-- 
Kevin P. Fleming
Digium, Inc. | Director of Software Technologies
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