MISRA.NAMESPACE.DECL

Using-declaration in header file.

MISRA-C++ Rule 7-3-6 (required): using-directives and using-declarations (excluding class scope or function scope using-declarations) shall not be used in header files.

This rule is also covered by MISRA.NAMESPACE.DIR and MISRA.NS.USING.HEADER.

Rationale

It is important to ensure that the order of inclusion of header files cannot affect the behaviour of a program.

Example

// f1.h
void foo ( char_t a );

namespace NS1
{
   void foo( int32_t a );
}
inline void bar ( )
{
   foo ( 0 );
}

// f2.h
namespace NS1
{
}

using namespace NS1;

// f1.cc
#include "f1.h"
#include "f2.h"

int32_t m1 ( )
{
   bar ( ); // bar calls foo ( char_t );
}

// f2.cc
#include "f2.h"
#include "f1.h"

void m2 ( )
{
   bar ( ); // bar calls foo ( int32_t );
}

In the above example, changing the order of the header files alters the meaning of the program.