g++/cpp problem with macros expanding to /##/

[Alexandre Oliva]

Craig Bridge <Craig.Bridge@seagatesoftware.com> writes:

> The "Just don't do it" answer doesn't cut it.

Sorry, it's the only portable solution.  You shouldn't rely on a
feature that the Standard explicitly forbids.

> Is there a simple way to get two preprocessor passes?

g++ -E - < file.cc | g++ -E - > file.ii && g++ file.ii

> I haven't figured out how to get g++ to take input from
> stdin.

The pre-processor will read from stdin; the C++ compiler won't

> Most of the comercially available compilers, Borland, Intergraph,
> Microsoft, Sun, Watcom, etc. support this feature.

> Many of their header files even use this trick to allow them to
> share include files between systems with various capabilities.

You should take a look at SGI STL (distributed with egcs); that's an
example of a portable way to enable or disable various capabilities
depending on the compiler's abilities.

-- 
Alexandre Oliva
mailto:oliva@dcc.unicamp.br mailto:aoliva@acm.org
http://www.dcc.unicamp.br/~oliva
Universidade Estadual de Campinas, SP, Brasil