Re: [boost] suggestion on assertion macros

Subject: Re: [boost] suggestion on assertion macros
From: Roland Bock (rbock_at_[hidden])
Date: 2010-03-12 16:59:55

Peter Dimov wrote:
> Steven Watanabe:
>
>> AMDG
>>
>> Roland Bock wrote:
>>> Stewart, Robert wrote:
>>>> C4800 seems ridiculous.  Writing code using int as a Boolean is 
>>>> common to C code. Why would VC 9 inflict useless noise when 
>>>> compiling such code?  Besides, if the variable is int, and it is 
>>>> needed in a Boolean context, what else would the developer do?  
>>>> I've seen use of the conditional operator to avoid that warning.  I 
>>>> suspect that produces worse code than what is done when "forcing 
>>>> value to bool 'true' or 'false'."
>>>>
>>> I agree. Still, I hope that static_cast is allowed to remove C4800
>>
>> Nope.
>>
>> .\scratch.cpp(20) : warning C4800: 'int' : forcing value to bool 
>> 'true' or 'false' (performance warning)
>
> C4800 is avoided with expr? true: false. In this case, sizeof( expr? 
> 0: 0 ) will also work, as we don't care about the value.
>
Oh! So the following should do the trick? That would be neat. It 
certainly works for gcc.

#include <cassert>

#ifdef NDEBUG
   #ifdef assert
      #undef assert
      #define assert(cond) static_cast<void>(sizeof(cond? 0: 0));
   #endif
#endif

int main() 
{
   int i = 0;

   assert(i);
}