Re: [Boost-users] Are Boost.Multi_Index and Boost.Format Planned for64-bitPortability?

From: Joaquín Mª López Muñoz (joaquin_at_[hidden])
Date: 2006-03-16 08:59:27

"Wu Yinghui, Freddie" ha escrito:

> Hi all,
>
> It's the first time I tried multi_index and format. I have to say that
> they are so powerful that I love them from the beginning!
>
> Nonetheless, when I enabled /Wp64 on my MSVC71 compiler, the headers
> gave me a lot of problems regarding possible pointer truncations (and
> sometimes default c'tor problems). The relevant warnings are something
> like the following:

[...]

> So I just wonder if both of these libraries have any plan on considering
> this issue? I really love these libraries, and I want to integrate them
> into our future product. But if the 64-bit portability issues are not
> solved, I'm afraid I'll have some problem pursuading the managers.

Hello Freddie,

As for Boost.MultiIndex, I can confirm the lib does work in 64-bit
environments (for instance, Linux PPC64, Tru64) and must also work
for Win64, although I've never had actual reports about this latter
platform (if you've got access to Win64, you might want to try and
tell back.) With respect to /Wp64 warnings, they are of two
kinds:

* C4312/C4311, conversions between differently sized types: this
is a case of /Wp64 being too dumb in its analysis of the type
boost::multi_index::detail::uintptr_type; this type is defined with
some metaprogramming machinery to be some integral type
with the same size as void*. So, it is unsigned int in Win32 and
unsigned long long in Win64. But /Wp64 sees it defined as
unsigned int, hence the warning. It is as if you had:

#ifdef _WIN64
typedef unsigned int integral_type;
#else
typedef unsigned long long integral_type;
#endif
void *p;
integral_type x=(integral_type)p;

/Wp64 is not able to see that integral_type will be
defined as unsigned long long in Win64, and emits a C4311.

* Complains about some internal node classes not being
constructable or about their automatic default constructors
being impossible to generate. I don't see what this has to do
with 64-bit portability; in any case, the compiler is right about
the analysis, but not about the consequences: these classes
are in effect never default constructed, their lifetime being
managed through an allocator interface. This is just an
overzealous warning.

So, Boost.MultiIndex must work in Win64, the best way to
check this out is to actually try.

As for Boost.Format, I cannot say cause I'm not the maintainer,
but in any case it seems to work on other 64-bit environments
as per the regression tests, and potential 64-bit problems
should be easy to tackle.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo