RE: [boost] Ideas for logging/tracing

From: Paul Mensonides (pmenso57_at_[hidden])
Date: 2004-11-13 19:51:27

> -----Original Message-----
> From: boost-bounces_at_[hidden] 
> [mailto:boost-bounces_at_[hidden]] On Behalf Of Alexander Nasonov

> > > 1. Use of PP_SEQ interface to "parse" function name and arguments
> > > 
> > >     int X::foo(char* buf, size_t len)
> > >     {
> > >         BOOST_TRACE_MEM_FUN( (foo)(buf, len) );
> >                                      ^^^^^^^^
> > 
> > You can't do this without variadic macros (ala C99).  We 
> should have 
> > these in
> > C++ eventually, but we don't right now and the pp-lib 
> doesn't support them.
> 
> I thought I can't but BOOST_PP_POP_FRONT( (foo)(buf, len) ) 
> works on gcc and sunpro!

That might work because there is no need to ever touch (buf, len).  That is not
guaranteed, however.

> BOOST_PP_ELEM(1, (foo)(buf, len) ) of course doesn't work but 
> BOOST_PP_ELEM(0, (foo)(buf, len) ) do.

Again, this happens to work because the implementation doesn't happen to touch
(buf, len) at all.  Once again, this is not guaranteed to work.  More generally,
without both variadic macros and a sequence implementation designed to handle
arbitrary-arity elements, (foo)(buf, len) is not a sequence.  There are, of
course, alternatives, such as (foo)((buf)(len)).

Regards,
Paul Mensonides