Add COPY_ARRAY, a safe and convenient helper for copying arrays,
complementing ALLOC_ARRAY and REALLOC_ARRAY. Users just specify source,
destination and the number of elements; the size of an element is
inferred automatically.
It checks if the multiplication of size and element count overflows.
The inferred size is passed first to st_mult, which allows the division
there to be done at compilation time.
As a basic type safety check it makes sure the sizes of source and
destination elements are the same. That's evaluated at compilation time
as well.
COPY_ARRAY is safe to use with NULL as source pointer iff 0 elements are
to be copied. That convention is used in some cases for initializing
arrays. Raw memcpy(3) does not support it -- compilers are allowed to
assume that only valid pointers are passed to it and can optimize away
NULL checks after such a call.
Signed-off-by: Rene Scharfe <l.s.r@web.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>