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struct A
{
	double x[2];
	double i;
};
 
struct B : virtual public A
{
	double y[2];
};
 
int main(void)
{
	B test;
	test.x[0] = 300;
	test.i    = -5;
 
	A const * const pA = &test;
	B const * const pB = &test;
	bool      const b  = reinterpret_cast<int const *>(pA)
		!= reinterpret_cast<int const *>(pB); // As expected
 
	double (B::*pmemberBBi)    = &B::i;
	double (B::*pmemberBBx)[2] = &B::x;
	double (A::*pmemberABx)[2] = &B::x;
 
	double const * const pBBi_B = &(pB->*pmemberBBi); // Valid pointer even though pointer to derived
	double const * const pBB_B  = pB->*pmemberBBx   ; // Null pointer, but why if the previous line worked?
	double const * const pAB_B  = pB->*pmemberABx   ; // Works (pointer to base)
 
	double bbi_b = pB->*pmemberBBi    ; // Works fine even though it is pointer to derived
	double bb_b  = (pB->*pmemberBBx)[0]; // Crash, but why if the previous line worked?
	double ab_b  = (pB->*pmemberABx)[0]; // Works (pointer to base)
 
	return 0;
}
 

prog.cpp: In function ‘int main()’:
prog.cpp:23:35: error: pointer to member conversion via virtual base ‘A’
  double (B::*pmemberBBi)    = &B::i;
                                   ^
prog.cpp:24:35: error: pointer to member conversion via virtual base ‘A’
  double (B::*pmemberBBx)[2] = &B::x;
                                   ^
prog.cpp:20:18: warning: unused variable ‘b’ [-Wunused-variable]
  bool      const b  = reinterpret_cast<int const *>(pA)
                  ^
prog.cpp:27:23: warning: unused variable ‘pBBi_B’ [-Wunused-variable]
  double const * const pBBi_B = &(pB->*pmemberBBi); // Valid pointer even though pointer to derived
                       ^
prog.cpp:28:23: warning: unused variable ‘pBB_B’ [-Wunused-variable]
  double const * const pBB_B  = pB->*pmemberBBx   ; // Null pointer, but why if the previous line worked?
                       ^
prog.cpp:29:23: warning: unused variable ‘pAB_B’ [-Wunused-variable]
  double const * const pAB_B  = pB->*pmemberABx   ; // Works (pointer to base)
                       ^
prog.cpp:31:9: warning: unused variable ‘bbi_b’ [-Wunused-variable]
  double bbi_b = pB->*pmemberBBi    ; // Works fine even though it is pointer to derived
         ^
prog.cpp:32:9: warning: unused variable ‘bb_b’ [-Wunused-variable]
  double bb_b  = (pB->*pmemberBBx)[0]; // Crash, but why if the previous line worked?
         ^
prog.cpp:33:9: warning: unused variable ‘ab_b’ [-Wunused-variable]
  double ab_b  = (pB->*pmemberABx)[0]; // Works (pointer to base)
         ^

Standard output is empty