Question

Is it possible to call a C++ function from a C source code?

Please advice.

Many thanks.

Answer 1

You will want to look into the extern C construct.

From the link:

 // This is C++ code

 // Declare f(int,char,float) using extern "C":
 extern "C" void f(int i, char c, float x);

 ...

 // Define f(int,char,float) in some C++ module:
 void f(int i, char c, float x)
 {
   ...
 }

You can also declare/define multiple functions using the extern C construct are like so:

Declaring and d multiple functions using extern C

extern "C"
{
   void func1();
   void func2();
}

extern "C"
{
   void func1()
   {
      /// do something
   }

   void func2()
   {
      // do something else
   }
}

You can even wrap #include declarations with extern "C" like so:

   extern "C"
   {
      #include "myHeader.h"
   }

The above will cause everything in fictional header myHeader.h to have C linkage, but can cause problems with nested includes – basically, do not use this construct if you can directly modify the header file yourself. It is a last resort technique.

Caveats

As Jack Kelly (thanks Jack Kelly!) mentions, be sure that if your C++ code involves exceptions, that they are handled in your function and are not allowed to propagate to C.

Functions defined with extern "C" linkage cannot be overloaded, as C does not allow multiple functions with the same name.

Your C and C++ code have to be compiled with similar compilers, as they need to agree on types, calling conventions, etc.

References, because I can’t do this alone

Thanks to the commenters.

• http://developers.sun.com/solaris/articles/mixing.html
• http://developers.sun.com/solaris/articles/external_linkage.html
• http://msdn.microsoft.com/en-us/library/0603949d(VS.80).aspx
• http://www.parashift.com/c++-faq-lite/mixing-c-and-cpp.html#faq-32.6