Messages in this thread | | | Date | Mon, 1 Aug 2016 14:03:25 +0200 (CEST) | From | Julia Lawall <> | Subject | Re: [Cocci] [PATCH v3] Coccinelle: Script to replace allocate and memset with zalloc functions |
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On Mon, 1 Aug 2016, SF Markus Elfring wrote:
> >> 1. Would it make sense to merge such SmPL rules into one > >> so that code duplication could be reduced a bit > >> in such a script? > > > > I think it would suffer in readability. > > How do you think about the following SmPL script example? > > @vz_combined > depends on patch && !context && !org && !report@ > type T; > T* pointer; > +statement S; > expression express; > @@ > pointer = > - vmalloc > + vzalloc > (...); > if (!d) > S > -memset(d, 0, sizeof( > ( > -T > | > -*(express) > ) > -));
OK, I thought you meant to make a big disjunctions for all of the before and after functions. This is a little better because it is bounded in size. But I don't understand why you have introduced the variable express. Normally one wants the cleared space to be the allocated size, which is normally the size of *pointer.
The performance issue is that disjunctions on expressions, eg (A | B), are implemented as (A | (!A & B)), ie with a negation of all the previous options &d with each option. So it is better to avoid very large disjunctions on expressions.
julia
> > > > Perhaps in performance as well. > > I admit that I am unsure about the run-time characteristics > for my suggestion. > > Regards, > Markus >
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