c and c++ mixed

Question

I need to call cpp method from c file. I have written this interface for that..

cpp file

extern "C" void C_Test(int p){
      Class::CPP_Test(p);
}

c file

extern void C_Test(int p);


void C_Function(){
   C_Test(10); //error
}

I get error in c file "undefined reference to C_Test(int)"

any idea whats wrong?

You need to show information about how this is compiled and linked. — unwind, Aug 22 '12 at 11:54
I am using C++ compiler for both types of files. Without "C" it works!! Also without extern "c" it works! — Meloun, Aug 22 '12 at 12:55
@Meloun, because your mangling the same. Your extern "C" needs to be in the .hpp where the function is declared and in the .cpp file. — Josh Petitt, Aug 22 '12 at 13:25

score 1 · Answer 1 · answered Aug 22 '12 at 12:43

You must declare extern only for function prototype, and ensure to link correctly. In addiction to this, CPP_Test(p) must be a static member of Class, otherwise your code does not work. At last, extern "C" must enclose in brackets its content, more like

extern "C"
{
  void C_Test(int p)
  {
    Class::CPP_Test(p);
  }
}

Tell us if this works.

score 1 · Answer 2 · answered Aug 22 '12 at 13:17

1

Are you compiling both with a C++ compiler? C++ compilers may compile a C-source file as C++, in which case it will perform name mangling, so you need to be sure to compile the C source file with a C compiler.

answered Aug 22 '12 at 13:17

chmeee

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I've seen them mangle and add prefix (I think Visual Studio possibly from memory, or maybe Borland), so even if you extern "C" your function may be _C_Test(int). Look at your settings. Also check your map file to see what symbols are being exported. – Josh Petitt Aug 22 '12 at 13:27

score 0 · Accepted Answer · answered Aug 30 '12 at 14:10

0

I am using C++ compiler for both types of files. Without "C" it works!! Also without extern "c" it works!

answered Aug 30 '12 at 14:10

Meloun

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That's just confusing. You said in your question that you need to call a C++ function from C file, i.e. you are using C and C++ compilers. Now you are saying that you only use C++ compiler. What does that mean? – AnT stands with Russia Aug 30 '12 at 14:22

c and c++ mixed

3 Answers3