MISRA.GENFU.ASSOC

Generic function is declared in an associated namespace.

MISRA-C++ Rule 14-5-1 (required): A non-member generic function shall only be declared in a namespace that is not an associated namespace.

Rationale

Argument-dependent lookup(ADL) adds additional associated namespaces to the set of scopes searched when lookup is performed for the names of called functions. A generic function found in one of these additional namespaces would be added to the overload set and chosen by overload resolution, which is inconsistent with developer expectation.

Example

template <typename T>
class B
{
public:
   B operator+ ( long & rhs );

   void f ( )
   {
      *this + 10;   // calls NS::operator+ and not
                    // B<NS::A>::operator+ when B is
                    // instantiated with NS::A
   }
};

namespace NS
{
   class A {
   public:
   };
   template <typename T>
   bool operator+ ( T, int32_t );   // Non-compliant — within associated
                                    // namespace
}
template class B<NS::A>;

ADL considers the namespace 'NS' to be an associated namespace. There are three functions in the overload set:

• The built-in 'operator+'

T operator+ ( T, T );

• The member 'operator+'

B<NS::A> B<NS::A>::operator+ ( long );

• The specializedgeneric function

bool NS::operator+< B<NS::A> > ( B<NS::A>, int32_t )

The conversion from the literal 10 to 'int32_t' is a better match than that to 'long', and therefore 'NS::operator+' is chosen rather than the member 'operator+', which may be inconsistent with developer expectations.