Re: [PATCH 2/2] replace-object.c: remove the_repository from prepare_replace_object

[Junio C Hamano <gitster@pobox.com>]

Stefan Beller <sbeller@google.com> writes:

> This was missed in 5982da9d2ce (replace-object: allow
> prepare_replace_object to handle arbitrary repositories, 2018-04-11)
>
> Technically the code works correctly as the replace_map is the same
> size in different repositories, however it is hard to read. So convert
> the code to the familiar pattern of dereferencing the pointer that we
> assign in the sizeof itself.

;-)

We say

	ptr = xmalloc(sizeof(*ptr))

is better because 

	ptr = xmalloc(sizeof(typeof(*ptr)))

is easy to go stale unless we actually use typeof and instead say a
concrete type like "struct oidmap".

This one was doing

	ptr = xmalloc(sizeof(*another_ptr))

and it was OK because ptr and another_ptr happened to be of the same
type.  I wonder if we are making it safer, or making it more obscure
to seasoned C programmers, if we introduced a pair of helper macros,
perhaps like these:

	#define ALLOCATE(ptr) (ptr) = xmalloc(sizeof(*(ptr)))
	#define CALLOCATE(ptr,cnt) (ptr) = xcalloc((cnt), sizeof(*(ptr)))

The change looks obviously good.  Will queue.

Thanks.