wahern • yesterday at 7:54 PM

That particular syntax has far too many caveats to be safely employed, IMO. It would be better to use variably-modified types (VMTs), which currently is more-or-less[1] a pointer to a VLA:

  int foo(int (*bar)[10])

In particular, sizeof(*bar) and (in C2y) countof(*bar) will do the correct thing. But you need to dereference bar almost every to use it properly, and unfortunately sizeof(bar) instead of sizeof(*bar) will compile cleanly, though countof(bar) is guaranteed to fail.

The dilemma is C's array to pointer decaying semantics. C2y will try to roll that back somewhat (a[i] will no longer be identical to i[a] via the a[i] == a + i == i + a transitive relation), but there's only so much you can do in that regard, especially for array passing, without new syntax or silently breaking alot of valid, proper, carefully written C code. There's too much that can fall through the cracks by relying on non-standard compiler heuristics to substitute for proper typing.

[1] Strictly speaking a VLA can only be created as automatic storage objects, but a VMT can type dynamically allocated (malloc'd) memory. But the syntax looks like a pointer to a VLA because it originates from the need to pass actual VLAs as parameters.