Why we use extern "C"

We often see the symbol extern "C"  in C++ source files.

Why use this?

Because C++ has overload function property like:

 

f(int i)      //defines f__Fi

f(int i ,char* j) //defines f__FiPc

 

When we link in other file

extern f(int);  // refers to f__FI

extern f(int,char*)  // refers to f__FiPc

 

But the C programming language's link symbol is not like this , because C don't have overload function.

 

int C:

f(int)  // defines _f

 

So, if we want use C lib , we must tell the compiler the link symbol is C style.

extern "C"{

   int f(int i);

}