Missing extern

[jaswinder]

Hello friends

We know that we can use the extern 'C' {} to use C code in C++.

I want instead to have extern 'C++' {} so that I can use C++ code in C.

But the compiler errors.

Any ideas. THANKS.

 

[Ian Collins]

Hello friends

We know that we can use the extern 'C' {} to use C code in C++.

I want instead to have extern 'C++' {} so that I can use C++ code in C.

But the compiler errors.

There's no such construct as extern 'C++' (or extern 'C' in C++, it's
extern "C").

 

[jaswinder]

There's no such construct as extern 'C++' (or extern 'C' in C++, it's
extern "C").

???

 

[Ian Collins]

???

What part of my reply wasn't clear?

 

[osmium]

We know that we can use the extern 'C' {} to use C code in C++.

I want instead to have extern 'C++' {} so that I can use C++ code in
C.

But the compiler errors.

What do you propose the compiler do when it encounters the undeclared
identifier "class"?

 

[Anand Hariharan]

Hello friends

We know that we can use the extern 'C' {} to use C code in C++.

I want instead to have extern 'C++' {} so that I can use C++ code in C.

But the compiler errors.

Any ideas. THANKS.

This is really a C++ question.

Pay careful attention to Ian's response -- in particular, note that he
said you have to use double quotes around C, not single quote (yes,
such 'small' details are important).

extern "C" actually allows C and C++ code to mix by telling the linker
that the declarations within that block should have C linkage. If you
can convince the linker that your C++ code can have C linkage, then
you should be able to achieve what you want. Of course, this means
you cannot have features exclusive to C++ such as templates,
exceptions, classes, function overloading etc. in your C++ function
declarations within the extern "C" block.

hope this helps,
- Anand

 

[Jorgen Grahn]

You can't get there from here.

To mix C and C++, you have to define an interface in terms of C functions,
types, and variables only and then implement the interface in C++.

And there are good examples in the C++ FAQ Lite -- for example, how to
use a simple C++ class from C with not too much trouble (just a bit of
inevitable wrapping).

/Jörgen

 

[Seebs]

Hello friends

We know that we can use the extern 'C' {} to use C code in C++.
Sorta.

I want instead to have extern 'C++' {} so that I can use C++ code in C.

You can't.

But the compiler errors.

No, you do.

Any ideas. THANKS.

If you really want to mix C and C++, your option (singular) is to use
a C++ compiler and wrap the C code in extern C. Or, use a C++ compiler
for the C++ code, but declare an interface with extern C so that you
can access it from C. Probably.

Basically, though, it turns out this is a C++ question, because the C
answer is "there are no provisions for using stuff in other languages."

(More generally, "extern C" doesn't even really let you use C code
in C++, it lets you use other things that are written using the C
linkage in C++, which could be anything from C to Fortran, or even
C++ complete with aggressive use of C++-specific features.)

-s