[Python-Dev] Multiple Inclusion of Header Files

[David Abrahams]

Neal Norwitz <neal@metaslash.com> writes:

> On Fri, Oct 11, 2002 at 07:48:52AM -0400, Guido van Rossum wrote:
> > > > is there any reason why these files:
> > > >     graminit.h
> > > >     patchlevel.h 
> > > >     pyconfig.h (aka pyconfig.h.in)
> > > > 
> > > > don't protect against being included multiple times?
> > > 
> > > I think they cannot possibly be included multiple times in a correct
> > > application, since a correct application does not directly include
> > > them, anyway.
> > 
> > But that's true of any .h file that's included by Python.h, isn't it?
> > And there's only a handful of .h files that Python.h doesn't include...
> 
> I don't really think there is much to be gained by adding protection.
> It's unlikely the files would be included directly by an application.
> Even if the files are included multiple times, the worst that should
> happen is a redefined warning.

Ahem. Don't forget that C++ applications may need to read these
files. The rules about redefinition are different in C++ IIRC.

So, if these files /really/ don't need to be #included directy by an
application, that's fine...

However, I note that Boost.Python has to #include <patchlevel.h> because
we have to apply workarounds before #including <Python.h> for certain
versions of Python, so I wouldn't say that it's very unrealistic to think
applications might need these files separately.

-- 
           David Abrahams * Boost Consulting
dave@boost-consulting.com * http://www.boost-consulting.com