Question

Currently I am working on a c framework and I want to embed a c++ package into it. However, there are lots of naming conflicts occurs. So I decided to to add a namespace to the C++ source. Now the question is should I move the #include “header.h” within namespace { } block? I just spent some time to figure out a bug which was resulted from the following codes.

Original C++ source

In a.h

#include <unistd.h>
struct File 
{
     void func(int fd);
}; 

In a.cpp

#include "a.h"
void File::func(int fd)
{
    ::close( fd );
}

And I added the namespace like this

New a.h

namespace MyAddedNameSpace 
{ 
    #include <unistd.h>
    struct File 
    {
        void func(int fd);
    }; 
}

New a.cpp

#include "a.h"
namespace MyAddedNameSpace 
{
    void File::func(int fd)
    {
        ::close( fd );
    }
}

And compiler complains that ::close() has not been declared.

The reason Why I put the #include directive inside namespace block is because the c++ package I imported also use #ifndef flag to include header files as follows. So I think the easy way is to put all codes within namespace block {}

#ifndef 
    #include <header1.h> 
    #include <header2.h>
    ...
#else 
    #include <header3.h>
    #include <header4.h>
    ...
#endif

Now I solved this problem by adding the extra line in cpp file

#include <unistd.h>  //new added line 
#include "a.h"
namespace MyNameSpace 
{
    void File::func(int fd)
    {
        ::close( fd );
    }
}

But I am not satisfied with this solution since unistd.h header has already been included in a.h, but inside the namespace MyAddedNameSpace, or should I added the prefix MyNameSpace to all the function calls where the compiler complain no such function declared ?

Thanks for the reply.

Answer 1

Usually it is enough to place the directive using namespace in the .cpp file.
Like that:

using namespace MyAddedNameSpace;

    void File::func(int fd)
    {
        close( fd );
    }

Hope it helps..