C/C++ in Arm Cross Compiler

in Arm, C++ compiler recognizes keyword: extern "C", and the Macro __cplusplus

In C header files, add __cplusplus to make sure the header files can be recognized by C++, as following

#ifdef  __cplusplus // This statement is true in C++ but false in C

extern "C"

{

#endif

//Original Header File Contents

#ifdef __cplusplus

}

#endif

In C++, 

If you'd like to include a C header file without changing the C header, you can do like:

extern "C"{

     #include "CHeader.h"

}

If you'd like to export a function to C, you can do like:

extern "C" int OutputApi(int);

<NOTE>

A header file can only be compiled one time.

So it is needed to add a pure C type header file additionally to designate what C++ exported functions.

This C type header file is actually included in other C source files. (not in C++)

Following are the workable method to achieve the C/C++ cross compiler in ARM.

a.cpp

void aa(void){}

a.h

#ifdef  __cplusplus

#define EXTERN_C extern "C"

#else

#define EXTERN_C

#endif

EXTERN_C  void aa(void);

intermediate.h

include <a.h>

b.c

include <intermediate.h>

void call_c()

{

    aa();

}