To summarise, I'd like to see the following program output the following=20
on all platforms:

 "Program is absent of Undefined Behaviour. YIPPIE!"


(I wonder if anyone can find a platform where it wouldn't? I doubt it.)


#include <iostream>
#include <cstdlib>

bool has_printed_UB =3D false;

void PerformUndefinedBehaviour()
{
    std::cout << "Undefined Behaviour!\n";

    has_printed_UB =3D true;
}

struct Monkey {
    union {
        double array[5];

        struct { double a, b, c, d, e; };

        struct { int f; int g; };
    };

    char h;

    double i;

    double j;
};

int main()
{
    Monkey obj;

    /* First demonstrate that the struct elements correspond
       to the array elements */

    obj.a =3D 1;
    obj.b =3D 2;
    obj.c =3D 3;
    obj.d =3D 4;
    obj.e =3D 5;

    if ( *obj.array !=3D 1 ||
         obj.array[1] !=3D 2 ||
         obj.array[2] !=3D 3 ||
         obj.array[3] !=3D 4 ||
         obj.array[4] !=3D 5 ) PerformUndefinedBehaviour();


    /* Now demonstrate that the first member of a POD union or POD struct
       has the same address as the actual union/struct. (Yes I realise
       that the Standard already guarantees this.) */


    int * p =3D reinterpret_cast<int*>(&obj);

    *p =3D 67;

    *++p =3D 54;

    if ( !( 67 =3D=3D obj.f && 54 =3D=3D obj.g ) ) PerformUndefinedBehavi=
our();


    /* Now show that i and j are contiguous: */

    if ( sizeof(double) !=3D
        reinterpret_cast<const char*>(&obj.j)
          - reinterpret_cast<const char*>(&obj.i)
       ) PerformUndefinedBehaviour();


    if (!has_printed_UB)
        std::cout << "Program is absent of Undefined Behaviour. YIPPIE!
\n";

    std::system("PAUSE");
}


-Tom=E1s

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