Re: boost/type_traits/config.hpp

From: Paul Mensonides (yg-boost-users_at_[hidden])
Date: 2002-11-06 12:53:51

"H. Morishima" <yg-boost-users_at_[hidden]> wrote in message
news:aqa8hd$cue$1_at_main.gmane.org...
> My compiler issues the following warning message
> (boost v1.29.0, G++ 3.2 with warning level high):
>
>     boost_1_29_0/boost/type_traits/config.hpp:90:55: warning: "BOOST_MSVC"
> is not defined
>
>
>
> boost/type_traits/config.hpp: line 90 is:
>
> # if (........ || BOOST_MSVC > 1301 || ........)

It should work fine as is.

> Shouldn't it be as follows?
>
> # if (........ || #defined(BOOST_MSVC) && BOOST_MSVC > 1301  || ........)

If an identifier is not defined, it should expand to 0 on a #if (or #elif)
directive line.  The only reason you sometimes see what you have above
(minus the extra # before 'defined') is that sometimes the macro actually
expands to 0.

This should be fine:

#if BOOST_MSVC

Provided that either BOOST_MSVC is *not* defined, or it expands to a numeric
expression that the preprocessor can handle.

> H. Morishima

Paul Mensonides