[boost] Re: BUG: mpl and iso646.h in vc7

From: Ken Hagan (K.Hagan_at_[hidden])
Date: 2004-05-19 02:37:55

> Ian Baxter wrote:
>> Boosters,
>>
>> Microsoft's macro hacks in the iso646.h header unfortunately kills
>> the current MPL implementation. The headers or.hpp, and.hpp are
>> substituted as ||.hpp, &&.hpp!

Eric Niebler wrote:
>
> I don't think changing the header names is the right solution. Since
> you're on VC7, you can use the push_macro and pop_macro pragmas to
> work around the issue.
>
> // file: or_.hpp
> #pragma once
> #pragma push_macro("or")
> #include <boost/mpl/or.hpp>
> #pragma pop_macro("or")

Nice workaround, but it won't help you much if you are using a library
that uses MPL. Renaming the header will upset everyone's sense of
aesthetics, but resolves the problem once and for all.

Incidentally, I assume VC7 is looking at

    #include <boost/mpl/or.hpp>

and macro expanding the "or". The standard text for preprocessing phase
4 does indeed begin "Preprocessing directives are executed and macro
invocations are expanded.", but the text for phase 3 begins "The source
file is decomposed into preprocessing tokens..." and I would have
thought
that "boost/mpl/or.hpp" (without the quotes) was a single
h-char-sequence
in this context so there is no invocation of the "or" macro here.
Clearly
at least one of "me" and "VC" must be wrong here.