Listing 3

(#if defined __cplusplus /* [4] */
    /* If the functions in this header have C linkage, this 
     * will specify linkage for all C++ language compilers */ 
    extern "C" { 
#endif 

 ... /* body of header */ 

#if defined __cplusplus 
    }   /* matches the linkage specification at the beginning. */ 
#endif