I wonder whether
double (*smallarr_ptr)[10] = &bigarr[297]; is defined behavior because there is no array of 10 elements there. There are (ideally) 10 elements, but that's a different matter. Syntactically it would also need a cast in C++ (C is probably more lenient, but it should produce a warning with a sufficiently high warning level): double (*smallarr_ptr)[10] = (double (*)[10])&bigarr[297];.
