Re: "static const" attribute in C++ (How to ?)

[Glynn Clements <glynn.clements@virgin.net>]

John Richard Moser wrote:

> |>It doesn't matter. A #include directive simply inserts the contents of
> |>the header file directly into the source code which is fed to the
> |>compiler. The compiler doesn't care which file a given piece of code
> |>comes from.
> |>
> |
> | It is a problem since a header can be included more then once, and
> 
> Umm.
> 
> #import "foo.h"
> 
> This includes only one time.  I'd only use this with Objective-C though.
> 
> For C, and in general, you should use:
> 
> #ifndef __FOO_H__
> #define __FOO_H__
> 
> ....
> 
> #endif /*__FOO_H__*/

That only prevents against the header being included multiple times
within a given compilation unit, which isn't the issue which was being
discussed. The issue was that, if an lvalue is defined (as opposed to
declared) in a header file, it will exist in every object file whose
source code included the header.

The key point is that C++ appears to treat initialised "static const"
members as compile-time constants, not as lvalues. Thus, they don't
exist in any object file, and so the problem of them existing in
multiple object files doesn't arise.

-- 
Glynn Clements <glynn.clements@virgin.net>