Re: [boost] [utility/swap] MSVC 10 test failure, unsigned long to std::bitset conversion invalid?

Subject: Re: [boost] [utility/swap] MSVC 10 test failure, unsigned long to std::bitset conversion invalid?
From: Niels Dekker - address until 2010-10-10 (niels_address_until_2010-10-10_at_[hidden])
Date: 2010-03-07 05:01:37

On 2010-03-07 01:05, Richard Webb wrote:
> The change from unsigned long to unsigned long long is a c++0x change (c++98
> says the constructor takes an unsigned long, and c++0x changes that to
> unsigned long long), and i think it was changed just to allow larger values.

Okay, but of course, the bitset(unsigned long long) constructor should 
still support passing an unsigned long as argument.

Note that C++0x also adds the bitset(const char*) constructor. As 
proposed by LWG issue #778, by Thorsten Ottosen:
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3019.html#778

> The int constructor looks like an MS special that was added in the release
> candidate. I was wondering if it was added to help out with this other bug:
> https://connect.microsoft.com/VisualStudio/feedback/details/500122/bitset-5-bits-0-fails-with-conflict-between-longlong-and-char

Thanks! I added comment to this Microsoft report (ID 500122), as well as 
to yours (ID 532897). And I voted for yours: 
https://connect.microsoft.com/VisualStudio/feedback/details/532897/problems-constructing-a-bitset-from-an-unsigned-long-in-the-vc-rc

Now back to utility/swap/test/std_bitset.cpp. Juergen Hunold has just 
informed us that the following works well on msvc-10.0, msvc-9.0 and 
gcc-4.4:

   typedef std::bitset<8> bitset_type;
   const bitset_type initial_value1 = 1;
   const bitset_type initial_value2 = 2;

Does that look fine to you as well?

What if some other std library implementation provides two overloads, 
bitset(unsigned long) and bitset(unsigned long long), without providing 
the non-standard bitset(int)? Then we'd have another ambiguity!

Maybe I shouldn't worry, and just commit the workaround to 
utility/swap/test/std_bitset.cpp, right?

Kind regards,

   Niels

-- 
Niels Dekker
http://www.xs4all.nl/~nd/dekkerware
Scientific programmer at LKEB, Leiden University Medical Center