Re: [PATCH 4/5] diff: use SWAP macro

From: René Scharfe <l.s.r@web.de>
Date: Jan 30, 2017, 17:26 UTC
Message-ID: <3058e7e1-c779-0183-9394-e9cd5e05cc3c@web.de>
In-Reply-To: <alpine.DEB.2.20.1701301704110.3469@virtualbox>

Am 30.01.2017 um 17:04 schrieb Johannes Schindelin:

Show 17 quoted lines

> Hi René,
>
> On Sat, 28 Jan 2017, René Scharfe wrote:
>
>> Use the macro SWAP to exchange the value of pairs of variables instead
>> of swapping them manually with the help of a temporary variable.  The
>> resulting code is shorter and easier to read.
>>
>> The two cases were not transformed by the semantic patch swap.cocci
>> because it's extra careful and handles only cases where the types of all
>> variables are the same -- and here we swap two ints and use an unsigned
>> temporary variable for that.  Nevertheless the conversion is safe, as
>> the value range is preserved with and without the patch.
>
> One way to make this more obvious would be to change the type to signed
> first, and then transform (which then would catch these cases too,
> right?).

I'm not sure it would be more obvious, but it would certainly make the type change more explicit. In diff-index.c we might even want to change the type of the swapped values from int to unsigned, which is more fitting for file modes. In diff.c we'd need to add a separate variable, as tmp is shared with other (unsigned) swaps.

René