Importing C enum into C++ namespace

Question

I am writing a C++ wrapper for a C library. In the C library, I have a

typedef enum {bar1,bar2} Foo; /* this is defined in the C library */

that I'd like to "bring" into a C++ namespace. I am using

namespace X{
    using ::Foo;
}

to achieve this. However, to qualify the enum members, I always have to refer to them as

X::Foo::bar1

and so on. Is there any way whatsoever of "importing" the C enum into a C++ namespace but refer directly to the values of the enum as

X::bar1

and so on? Or, in other words, can I import directly the values of the enum into the namespace?

EDIT

I do not think the question is a dupe, please see my answer as I realized there is a solution.

Possible duplicate of using declaration with enum?

Alan Birtles
– Alan Birtles

2019-02-28 17:18:05 +00:00
Commented Feb 28, 2019 at 17:18 — Alan Birtles
– Alan Birtles, Commented Feb 28, 2019 at 17:18

AnT stands with Russia · Accepted Answer · 2019-02-28 17:28:44Z

4

That's just how using declaration works. Global Foo and bar1 are two different names. Your using declaration brings name Foo into namespace X, but does not bring any other names from global namespace (like names of the enum members). For that you'd need

namespace X {
  using ::Foo;
  using ::Foo::bar1;
  using ::Foo::bar2;
}

edited Feb 28, 2019 at 17:28

answered Feb 28, 2019 at 17:18

AnT stands with Russia

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1 Comment

vsoftco Over a year ago

I realized I can also do namespace X{ extern "C" {include <C_library>} } which will do it for me. For some reason I though I cannot have C linkage inside namespaces...

vsoftco · Accepted Answer · 2019-03-01 21:54:04Z

1

A solution that works for me is to do

namespace X{
    extern "C"{
        #include <C_library.h>
    }
}

Before trying it I had the impression that I cannot put C-linkage functions inside a namespace, but it turns out I was wrong. Then I can simply do

X::bar1

to access the C enum member bar1 from typedef enum {bar1, bar2} Foo;.

See e.g. extern "C" linkage inside C++ namespace?

edited Mar 1, 2019 at 21:54

answered Feb 28, 2019 at 18:20

vsoftco

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