a newbie's question about namespace

[ZF Tang]

As you know,if I include "cstdio, cstdlib,...", instead "stdio.h,
stdlib.h,...",
their content will be declared in the std namespace.

But the following code is compiled successfully even though "using namespace
std" is commented out, why?

#include <cstdio>
using namespace std;
void main()
{
printf("Hello, world!\n");
}

 

[Rolf Magnus]

As you know,if I include "cstdio, cstdlib,...", instead "stdio.h,
stdlib.h,...",
their content will be declared in the std namespace.

But the following code is compiled successfully even though "using
namespace std" is commented out, why?

Probably for the same reason it accepts void as return type of main. It is
faulty.

 

[Alf P. Steinbach]

* Rolf Magnus:

Probably for the same reason it accepts void as return type of main. It is
faulty.

Well, no.

It's just impractical for a compiler vendor to make the C header files
include the C++ header files and put everything also in the global
namespace: then separate C and C++ version of the same header files
would have to be maintained (impractical), or some heavy trickery used.

Instead what's done is to let the C++ header files include the C ones
and place the global namespace declarations also in namespace 'std';
when the standard specifies 99.999% impractical things, compiler vendors
simply do not comply -- the case here, and the case for 'export'.