CODEWITHSUNDEEP
c++namespaceslanguage-designunnamed-namespace
yohjp
yohjp

Reputation: 3135

C++ unnamed(anonymous) namespace definition

C++03 Standard 7.3.1.1 [namespace.unnamed] paragraph 1: (and C++11 Standard also use similar definition)

An unnamed-namespace-definition behaves as if it were replaced by

namespace unique { /* empty body */ }
using namespace unique;
namespace unique { namespace-body }

Why not is it simply following definition?

namespace unique { namespace-body }
using namespace unique;

Side question: MSDN defines by latter form. Does it violate Standard technically?

Upvotes: 8

Views: 426

Answers (1)

Johannes Schaub - litb
Johannes Schaub - litb

Reputation: 507373

You could not do this anymore

namespace { typedef int a; ::a x; }

Note that in a subsequent namespace { ... }, suddenly you could. This would be horribly inconsistent.

Also notice this case, with two different valid outcomes

namespace A { void f(long); }
using namespace A;

namespace { 
  void f(int);
  void g() {
    ::f(0);
  }
}

With ISO C++, this calls the int version of f. With your alternative definition, it calls the long version.

Upvotes: 7

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