fetch_and_$op_$type ptr val atomically runs *( *$type )ptr $op val, stores the result at ptr, and returns the original value at ptr.

fetch_and_$op_$type ptr val atomically runs *( *$type )ptr $op val, stores the result at ptr, and returns the original value at ptr.

fetch_and_$op_$type ptr ~pos val atomically runs *( *$type )((ptr + pos) $op val, stores the result at ptr + pos, and returns the original value at ptr + pos.