Question

I have three structs, one of which inherits from the other two:

typedef struct _abc
{
    int A;
    int B; 
    int C;
} ABC;

typedef struct _def
{
    int D;
    int E;
    int F;
} DEF;

typedef struct _abcdef : ABC, DEF { } ABCDEF;

(I want the third struct to contain all the members of the first two. Is there a better way to do it?)

Now, I have fully populated instances of ABC and DEF, and I want to make a new ABCDEF instance:

int main()
{
    ABC abc;
    abc.B = 2;
    abc.C = 1;
    abc.A = 10;

    DEF def;
    def.D = 32;
    def.E = 31;
    def.F = 90;

    // make a new ABCDEF with all the values of abc and def
}

What is the best way to create the ABCDEF? I could do this, but it kinda sucks:

ABCDEF abcdef;
abcdef.A = abc.A;
abcdef.B = abc.B;
abcdef.C = abc.C;
abcdef.D = def.D;
abcdef.E = def.E;
abcdef.F = def.F;

The above is coupled to the members of the structs, and is messy if many members are added.

Answer 1

This is C++. Those typedefs aren’t needed. And you have constructors:

struct abc {
    int A;
    int B; 
    int C;
    abc(int a, int b, int c) : A(a), B(b), C(c) {}
};

struct def {
    int D;
    int E;
    int F;
    def(int d, int e, int f) : D(d), E(e), F(f) {}
};

struct abcdef : abc, def {
  abcdef(const abc& a, const def& d) : abc(a), def(d) {}
};

int main()
{
   abc a(2,1,10);
   def d(32,31,90);
   abcdef ad(a,d);

   return 0;
}