suspicious piece of code in RTS(Profiling.c) code

[Simon Marlow]

We could probably remove that check.

Cheers,
Simon

On 02/06/2014 19:09, Edward Z. Yang wrote:
> Hello Ömer,
>
> That does seem pretty suspicious. My interpretation is that
> ccs should just never be EMPTY_STACK.  If we look at the calling
> codepaths, the only case that a NULL could be passed is if
> pushCostCentre is called with NULL ccs, but we only create these
> invocations in code generation and never pass a NULL in such situations.
>
> What I am not sure is if there is some special treatment for empty
> stacks that should be happening, but is not, at the moment.
>
> Edward
>
> Excerpts from Ömer Sinan Ağacan's message of 2014-06-02 08:19:21 -0700:
>> Hi all,
>>
>> I recently found a suspicious piece of code in RTS code.
>>
>> * https://github.com/ghc/ghc/blob/master/rts/Profiling.c#L622 here it's
>> checking that ccs is not EMPTY_STACK.
>> * https://github.com/ghc/ghc/blob/master/includes/rts/prof/CCS.h#L96 here
>> EMPTY_STACK is defined as NULL.
>>
>> Now weird part is that before the if-statement checks for `ccs != NULL` ccs
>> is used to reach some of it's fields(for example, line 601 and 602). As far
>> as I can see either we have a bug here or the if-statement is not necessary
>> and we can move it's body to top level.
>>
>> Am I missing anything here?
>>
>> Thanks.
>>
>> ---
>> Ömer Sinan Ağacan
>> http://osa1.net
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