Why is this valid C

Question

I came across this code on reddit. I would have thought that type conversions would have caused this to be invalid.

int a[3] = { { {1, 2}, {3, 4}, 5, 6 }, {7         


        

Answer 1

  int a[3] = { { {1, 2}, {3, 4}, 5, 6 }, {7, 8}, {9}, 10 };

is invalid.

It is invalid for the same reasons int b[1] = {1, 2}; is invalid: because C99 says

(C99, 6.7.8p1) "No initializer shall attempt to provide a value for an object not contained within the entity being initialized."

The last element 10 in a initializers attempts to provide a value for an object not contained within the entity being initialized.