Re: [boost] boost::mpl::for_each and value_initialized

Subject: Re: [boost] boost::mpl::for_each and value_initialized
From: Aleksey Gurtovoy (agurtovoy_at_[hidden])
Date: 2010-01-22 20:12:07

On Fri, 22 Jan 2010 04:06:40 -0600, Niels Dekker - address until  
2010-10-10 <niels_address_until_2010-10-10_at_[hidden]> wrote:

> Aleksey Gurtovoy wrote:
>> [...] I think we should revert to the approach of applying the  
>> workaround
>> conditionally for the specific compilers known to be buggy, and just
>> those -- especially if we have tests to discover these bugs should they
>> return.
>>
>> As for the specific compiler versions:
>>
>> - GCC bugs #30111 and #33916 has been fixed in 4.4 and 4.2.4
>>   correspondingly [1], [2].
>
> So GCC 4.2.4 still needs the memset, but GCC >= 4.4.0 can do without it,  
> right?

Yep.

>> - MSVC bug #100744, despite being marked as "Closed, Won't Fix" [3],
>>   has actually been fixed in VC9 [4].
>
> I'm sorry, MSVC bug #100744 is still there, even though #335987 has been  
> fixed. VC9 deals with POD types correctly, but may not do so for non-POD  
> aggregate class types.

Hmm, you are right, it doesn't.

>> - Borland bug #51854 is also reported as being fixed in build
>>   "12.0.3140.16150" [5]
>
> Looks promising. Do you know how to do a compile-time check if  
> Borland/Codegear build >= 12.0.3140.16150?

I don't, but may be somebody more familiar with C++ Builder can help us.

> Anyway, I wouldn't mind if the memset call in utility/value_init.hpp  
> would become conditional, for example as follows:
>
>   #ifdef BOOST_VALUE_INITIALIZATION_NEEDS_MEMSET
>       std::memset(&x, 0, sizeof(x));
>
>   #endif
>
> What do you think? And would it be okay to you to have such a macro,  
> BOOST_VALUE_INITIALIZATION_NEEDS_MEMSET, defined in  
> boost/config/compiler/, for those specific compiler versions?

Sounds good to me. John?

-- 
Aleksey Gurtovoy
MetaCommunications Engineering