Re: [boost] BOOST_WORKAROUND and g++ -Wundef

From: Joaquín Mª López Muñoz (joaquin_at_[hidden])
Date: 2005-10-14 08:04:22

Angus Leeming ha escrito:

> Joaquín Mª López Muñoz wrote:
> > But I think it makes much more sense if BOOST_WORKAROUND itself includes
> > the patch, so that instead of its current definition
> >
> > #  define BOOST_WORKAROUND(symbol, test)                \
> >         ((symbol != 0) && (1 % (( (symbol test) ) + 1)))
> >
> > it looks like
> >
> > #  define BOOST_WORKAROUND(symbol, test)                \
> >         (defined(symbol) && (symbol != 0) && (1 % (( (symbol test) ) +
> >         1)))
> >
> > Anyone sees some problem with this?
>
> That would be much nicer. However, reverting my patch and applying yours
> (below, to confirm I got it right :)), I get this when compiling my test
> case:
>
> $ g++ -Wundef -Iboost/cvs -o trial trial.cpp
> In file included from boost/cvs/boost/random.hpp:36,
>                  from trial.cpp:1:
> boost/cvs/boost/random/linear_congruential.hpp:139:64: operator "defined"
> requires an identifier
> boost/cvs/boost/random/linear_congruential.hpp:139:64: missing '(' in
> expression
>

Oh, my bad. Seems like a problem with the replacement semantics of
the preprocessor, turns out defined() can only be used inside an #if or #elif
directive, and not inside a #define as I tried, hence the problem --and I guess
that's the reason why my proposed patch wasn't there in the first place when
BOOST_WORKAROUND was written. Probably Mr. Mensonides can
clarify this issue further.

Sorry for the noise,

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo