ffi:size

(ffi:size type)

Answers the size in bytes of a foreign type. The C integer names are their LP64 widths (:long is 8), and a (:struct member...) designator is laid out with the C padding rule, so its size includes the tail padding.

(:struct :int :double) is 16 rather than 12: the double is aligned to 8, and the struct's size is a multiple of its alignment.