Re: [PATCH] mv: prevent mismatched data when ignoring errors.

[Eric Sunshine <sunshine@sunshineco.com>]

On Mon, Mar 17, 2014 at 11:07 AM, Michael Haggerty <mhagger@alum.mit.edu> wrote:
> On 03/17/2014 07:33 AM, Junio C Hamano wrote:
>> Junio C Hamano <gitster@pobox.com> writes:
>>
>>> Would it make sense to go one step further to introduce two macros
>>> to make this kind of screw-up less likely?
> potential callers that I noticed, ALLOC_GROW() was used immediately
> before making space in the array for a new element.  So I suggest
> something more like
>
> +#define MOVE_DOWN(array, nr, at, count)        \
> +       memmove((array) + (at) + (count),               \
> +               (array) + (at),                         \
> +               sizeof((array)[0]) * ((nr) - (at)))

Each time I read these, my brain (for whatever reason) interprets the
names UP and DOWN opposite of the intended meaning, which makes them
confusing. Perhaps INSERT_GAP and CLOSE_GAP would avoid such problems,
and be more consistent with Michael's proposed ALLOC_INSERT_GAP.

> +#define ALLOC_INSERT_GAP(array, nr, at, count, alloc)               \
> +       do {                                                         \
> +               ALLOC_GROW((array), (nr) + (count), (alloc));        \
> +               MOVE_DOWN((array), (nr), (at), (count));             \
> +       } while (0)
>
> Also, count==1 is so frequent that this special case might deserve its
> own macro pair.
>
> I'm not inspired by these macro names, though.
>
> Michael
>
> --
> Michael Haggerty
> mhagger@alum.mit.edu
> http://softwareswirl.blogspot.com/