Re: [Boost-users] Boost.Unordered throws 64-bit portability warnings

On Thu, May 21, 2009 at 2:36 PM, Daniel James wrote:

2009/5/21 Dominique Devienne :

...

FWIW, I'm getting these as well when using boost::hash_combine(hash_value(this->member_)); to implement hashes for my classes. We also use VS2005 with the compiler switch that raises these warnings. My work around below is not pretty... --DD

#if ACME_SIZEOF_SIZE_T == 4        // Avoid warning C4267: 'argument' :        // conversion from 'size_t' to 'unsigned int', possible loss of data        boost::hash_combine(            seed, static_cast<unsigned int>(hash_value(member_))        ); #else        boost::hash_combine(seed, hash_value(member_)); #endif

Doesn't 'boost::hash_combine(seed, member_)' work?

Never meant to imply it doesn't work, sorry. It's just to avoid the warning, while not "breaking" the 64-bit compiles by doing the narrowing-on-64-bit cast unconditionally. Could have snuffed the VS2005 warning too. But it's an annoying warning.

I'll have a look at the warning when I get the chance, but AFAICT they're wrong since when compiling for 64-bit a different overload or template resolution would be chosen.

No argument from me there ;-) --DD