Actually, the question that I was unsure about and I could not find a ready answer in the standard is whether one can use ((double *)(&cam_xyz[0][0]))[j] to address the whole multidimensional array.
No, that's undefined. The relevant text is in section 6.5.6, paragraph 8 of the C11 standard and summarized in Annex J.2, Undefined Behavior with a clarifying example like so: An array subscript is out of range, even if an object is apparently accessible with the given subscript (as in the lvalue expression a[1][7] given the declaration int a[4][5]) (6.5.6). > This also > raises the question of whether is valid to initialize a > multidimensional array with memset as memset(&cam_xyz[0][0], 0, > sizeof(cam_xyz)). Using memset, memcpy, and memove on any object, including an array, is valid because all objects may be accessed via lvalues of unsigned char and that's just what the memxxx functions are specified to do. Martin
