Comma operator = broken design

[Regan Heath]

On Fri, 09 Dec 2011 14:54:16 -0000, Timon Gehr <timon.gehr at gmx.ch> wrote:
>>>>>> 10)
>>>>>>
>>>>>>> return
>>>>>>> c <= 0x7F ? 1
>>>>>>> : c <= 0x7FF ? 2
>>>>>>> : c <= 0xFFFF ? 3
>>>>>>> : c <= 0x10FFFF ? 4
>>>>>>> : (assert(false), 6);
>>>>>>
>>>>>> *Much* clearer with the rewrite..
>>>>>>
>>>>>> assert(c <= 0x10FFFF);
>>>>>> return
>>>>>> c <= 0x7F ? 1
>>>>>> : c <= 0x7FF ? 2
>>>>>> : c <= 0xFFFF ? 3
>>>>>> : c <= 0x10FFFF ? 4
>>>>>> : 6;
>>>>>>
>>>>>
>>>>> This is a *much* better rewrite:
>>>>> assert(c <= 0x10FFFF);
>>>>> return
>>>>> c <= 0x7F ? 1
>>>>> : c <= 0x7FF ? 2
>>>>> : c <= 0xFFFF ? 3
>>>>> : 4;
>>>>
>>>> Again, I was missing context.. is the return value of 6 not required  
>>>> in
>>>> release mode?
>>>
>>> I was joking here. Your 'rewrite' of the original example changed its
>>> release mode semantics, therefore I did the same thing.
>>
>> My version performs the assert in all cases, throws an assert error in
>> the same/error cases, and still returns the correct/original values. The
>> only change is performing the assert in all cases, so I don't see how
>> that is a problem. Yours however is entirely broken (assuming the return
>> value of 6 is desired/required).
>>
>> R
>>
>
> What you might be missing is that assert(false) is not compiled out in  
> release mode. It emits a 'hlt' instruction which kills your program.  
> However, your assert(c <= 0x10FFFF); will be removed in release mode.

I was indeed missing that.  I couldn't find anything about it on the  
website. :)

R

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