Re: [PATCH 3/2] apply: use COPY_ARRAY and MOVE_ARRAY in update_image()

> 
> 
> On 15/07/17 21:20, René Scharfe wrote:
>> Simplify the code by using the helper macros COPY_ARRAY and MOVE_ARRAY,
>> which also makes them more robust in the case we copy or move no lines,
>> as they allow using NULL points in that case, while memcpy(3) and
>> memmove(3) don't.
>>
>> Found with Clang's UBSan.
>>
>> Signed-off-by: Rene Scharfe <l.s.r@web.de>
>> ---
>> I don't know why the rules in contrib/coccinelle/array.cocci didn't
>> match. :-?
>>
>>   apply.c | 11 ++++-------
>>   1 file changed, 4 insertions(+), 7 deletions(-)
>>
>> diff --git a/apply.c b/apply.c
>> index f2d599141d..40707ca50c 100644
>> --- a/apply.c
>> +++ b/apply.c
>> @@ -2809,13 +2809,10 @@ static void update_image(struct apply_state *state,
>>   		img->line_allocated = img->line;
>>   	}
>>   	if (preimage_limit != postimage->nr)
>> -		memmove(img->line + applied_pos + postimage->nr,
>> -			img->line + applied_pos + preimage_limit,
>> -			(img->nr - (applied_pos + preimage_limit)) *
>> -			sizeof(*img->line));
>> -	memcpy(img->line + applied_pos,
>> -	       postimage->line,
>> -	       postimage->nr * sizeof(*img->line));
>> +		MOVE_ARRAY(img->line + applied_pos + postimage->nr,
>> +			   img->line + applied_pos + preimage_limit,
>> +			   img->nr - (applied_pos + preimage_limit));
>> +	COPY_ARRAY(img->line + applied_pos, postimage->line, postimage->nr);
> 
> My patch looks like:
> 
> -       memcpy(img->line + applied_pos,
> -              postimage->line,
> -              postimage->nr * sizeof(*img->line));
> +       if (postimage->line && postimage->nr)
> +               memcpy(img->line + applied_pos,
> +                      postimage->line,
> +                      postimage->nr * sizeof(*img->line));
> 
> ... which I think I prefer (slightly).