c++ - Static and anonymous namespace

Possible
Duplicate:
href="https://stackoverflow.com/questions/154469/unnamed-anonymous-namespaces-vs-static-functions">Unnamed/anonymous
namespaces vs. static functions

Is
this completely redundant, or may there be a reason to do
this?

namespace {

            static void f() {
 ...


            }
}

class="post-text" itemprop="text">

class="normal">Answer

It looks
redundant to me -- either being declared static or being in an anonymous namespace means
it has internal linkage.

§3.5/3:

A name having
namespace scope (3.3.6) has internal linkage if it is the name of:
— a
variable, function or function template that is explicitly declared
static;

§3.5/4:

[...] An unnamed namespace or a namespace declared directly or indirectly
within an unnamed namespace has internal linkage. [...] A name having namespace scope
that has not
been given internal linkage above has the same linkage as the
enclosing namespace if it is the name of
— a variable; or
— a
function; or

So,
as it is right now, it has internal linkage because it's explicitly declared static. If
it wasn't explicitly declared static, it would have internal linkage because it's
declared inside an unnamed namespace. Same effect either
way.

Note that here I'm replying
specifically about a function -- there are a few obscure cases
where there's a difference when you're dealing with the name of a type (e.g.,
class/struct/union), but I don't know of any such thing that applies in the case of a
function.

As far as what internal linkage really
means, that's one of those places the standard is actually quite direct and clear. It's
probably best to quote the definitions of all three possibilities
(§3.5/2):

1. When a name has
   external linkage, the entity it denotes can be referred to by names
   from scopes of other translation units or from other scopes of the same translation
   unit.


2. When a name has internal
   linkage, the entity it denotes can be referred to by names from other scopes
   in the same translation unit.


3. When a name has
   no linkage, the entity it denotes cannot be referred to by names
   from other
   scopes.

Note
that the italics above match those in the standard, which is its way of saying that
these sentences define what those phrases mean throughout the rest of the
standard.