Re: const has file scope

From:

Jeff Schwab <jeff@schwabcenter.com>

Newsgroups:

comp.lang.c++

Date:

Sun, 03 May 2009 11:16:27 -0400

Message-ID:

<S5idnSaMjJnWKGDUnZ2dnUVZ_g9i4p2d@giganews.com>

Jeff Schwab wrote:

pauldepstein@att.net wrote:

The C++ Primer (4th edition -- Lippman, Lajoie and Moo) explains that
(non-local) const variables have file scope

namespace scope, not file scope

rather than global scope
and can therefore be defined in header files.

In this context, what is meant by a "const variable"?

A variable whose static type is const-qualified. For example:

std::string const application_name = "Widget Master 3000";

The examples
with (for example)
const int x = 2; are clear enough. But how about references to
const

That's a tricky one. I think it would technically be OK.

As Alf just pointed out, references apparently cannot have internal
linkage, unless they are explicitly so declared with the deprecated
keyword "static".

$ echo 'int const& i = 5; int main(){}' > main.cc
$ echo 'int const& i = 5;' > other.cc
$ g++ main.cc other.cc
ld: duplicate symbol _i in
/var/folders/wZ/wZOdSIG5Gt0a5FJyNyYi7E+++TM/-Tmp-//ccK6wv0P.o and
/var/folders/wZ/wZOdSIG5Gt0a5FJyNyYi7E+++TM/-Tmp-//cclpsTtN.o
collect2: ld returned 1 exit status