C Interoperability and Type Casting

1. Avoid mixing C headers, functions, and casting use corresponding C++ equivalent. Example: use cmath not math.h, iostream not stdio.h

   • Don't

     #include <stdio.h>
     #include <math.h>
     ...
     float powerOfTwo = powf( 2.f, 5.f );
     printf( "2^5 = %f\n", powerOfTwo );

   • Do

     #include <iostream>
     #include <cmath>
     ...
     constexpr float powerOfTwo = powf( 2.f, 5.f );
     std::cout << "2^5 = " << powerOfTwo << "\n";              

2. Exceptions for using C headers/functions:

   • C++ API is deprecated or not fully supported in libraries ( e.g. MPI, CUDA_C, PETSc )
   • No POSIX equivalent in C++: e.g. unistd.h, shmem.h, sys/ipc.h
   • Language Interoperability through C

     C++ --> C --> Fortran --> C --> C++
     C++ --> C --> JNI --> Java --> JNI --> C --> C++
     

3. Avoid C-style casting: use C++11 style casting: static_cast, dynamic_cast (classes), reinterpret_cast.

   • Don't

        int foo = ( int ) bar;
        char* buffer = ( char* ) data;

   • Do

        int foo = static_cast<int>( foo );
        char* buffer = reinterpret_cast<char*>( data );