Can I include a headerfile in a namespace?

Question

I am using the <conio.h> header file, and somewhere else in my source code I define a function with the name getch and it has to have that name. Since there already is a getch in <conio.h>, and this header file declares all of its functions in the global namespace, I get a name collision.

I found that using the following syntax would avoid the collision:

namespace some_namespace
{
    #include <conio.h>
}

Then I can use some_namespace::getch when I want to access the function in <conio.h> and getch when I want to access my own function.

Is this valid syntax? I know <conio.h> is only for windows, but is this kind of syntax going to behave the same across all the compilers? What other ways do you suggest to get around this problem?

Edit:

I use GCC and MSVC 2019 on Windows and it compiles fine on both of them.

I can access the functions in <conio.h> as well, getch in particular as I showed above (even though I should use the name _getch instead of getch in MSVC).

Why not put your own code (including your `getch`) in your own namespace? — StoryTeller - Unslander Monica, May 08 '21 at 15:17
Don't forget to `extern "C"` as well, `` is a C header file. — mediocrevegetable1, May 08 '21 at 15:18
@S.M. I tried it with both gcc and MSVC 2019 and it works on both of them. — Amirreza A., May 08 '21 at 15:26
The standard headers were written with the intention that they be used in the global namespace. If this kind of hackery happens to work it's only by accident, and it could well fail with a different compiler (including a future version of the compiler you're using now). — Pete Becker, May 08 '21 at 16:06

Jon Reeves · Accepted Answer · 2021-05-08T16:53:31.367

System header files like <conio.h> which are intended to be used in both C and C++ will enclose their declarations in an extern C scope, forcing C linkage for all that is contained in them, regardless of whatever additional C++ namespaces you add. That’s why your code compiles in this case.

See also this, which is almost a duplicate of this question, but not exactly.

In short, yes it’s valid, but I would strongly encourage against it. There are many other ways to solve this problem, like creating wrapper modules for the functions you want to have alternate symbols for.

As a side note: try putting your own getch in an extern C block. My guess is you’ll get a linker error.

Can I include a headerfile in a namespace?

Edit:

1 Answers1