Messages in this thread |  | | | Date | Wed, 15 Jun 2011 10:33:08 -0500 | | From | Greg Dietsche <> | | Subject | Re: [Cocci] Re: [PATCH v2] coccinelle: if (ret) return ret; return ret; semantic patch |
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On 06/15/2011 12:58 AM, Julia Lawall wrote: > On Tue, 14 Jun 2011, Greg Dietsche wrote: > >> >> >> On 06/14/2011 04:24 PM, Greg Dietsche wrote: >>> On 06/14/2011 12:50 AM, Julia Lawall wrote: >>>> On Mon, 13 Jun 2011, Greg Dietsche wrote: >>>>> just curious... i see you usually just write "return ret;" here when >>>>> posting. >>>>> I've assumed that's because it will 1) work and 2) is close enough. >>>>> >>>>> You'll notice I've been doing: >>>>> -return ret; >>>>> +return ret; >>>>> because it seems to help coccinelle realize that it can get rid of >>>>> extra line >>>>> feeds - does this make sense - or should i just be doing a "return ret"? >>>> I wondered why you were doing that :) >>>> >>>> Is the problem that the removed if is being replaced by a blank line? If >>>> so, that is not intentional. I will look into it. If it doesn't happen >>>> always, an example where it does happen could be helpful. >>>> >>> >>> Some times it gets it right, so it's not always wrong. For example: >>> >>> diff -u -p a/arch/m68k/math-emu/fp_log.c b/arch/m68k/math-emu/fp_log.c >>> --- a/arch/m68k/math-emu/fp_log.c 2011-06-13 14:06:37.943954469 -0500 >>> +++ b/arch/m68k/math-emu/fp_log.c 2011-06-14 16:07:22.394954040 -0500 >>> @@ -105,9 +105,6 @@ fp_fetoxm1(struct fp_ext *dest, struct f >>> >>> fp_monadic_check(dest, src); >>> >>> - if (IS_ZERO(dest)) >>> - return dest; >>> - >>> return dest; >>> } >>> >>> >>> >>> Here's an example where it got it "wrong" - notice how the blank line is >>> missing the - : >>> >>> diff -u -p a/arch/frv/mm/pgalloc.c b/arch/frv/mm/pgalloc.c >>> --- a/arch/frv/mm/pgalloc.c 2011-06-13 14:06:37.855954391 -0500 >>> +++ b/arch/frv/mm/pgalloc.c 2011-06-14 16:07:16.714954008 -0500 >>> @@ -136,8 +136,6 @@ pgd_t *pgd_alloc(struct mm_struct *mm) >>> pgd_t *pgd; >>> >>> pgd = quicklist_alloc(0, GFP_KERNEL, pgd_ctor); >>> - if (!pgd) >>> - return pgd; >>> >>> return pgd; >>> } > > OK, but it is going to be hard for Coccinelle to know that, although the > programmer previously thought that return should be separated from the > rest of the function by a blank line, that is now no longer the case. > Perhaps it is due to the fact that there is now only one other line in the > body of the function, but it seems like an opinion as to how to draw the > line. >
OK - I can see how that would be hard for Coccinelle to guess what we really want in this case.
> So your - return ret; + return ret; is probably the appropriate solution. > You want to get rid of the whole pattern if (...) return ret; return ret; > and replace it with just return ret;, which will then be inserted at the > point of the beginning of the match to the pattern.
ok
> It would be nicer to put the - return ret; + return ret; inside the last > line of the ( | ). Then only those return ret's are rewritten rather than > every return ret in the program. It should improver performance and
except that 4 of the 5 ORs are cases where we want to do the -return ret; + return ret; So I suppose for performance, I should actually add the +/- to each of the 4 cases that we want cocci to generate a patch for?
thanks, Greg
> reduce the risk of changing spacing. The other ifs in the ( | ) don't > need to be followed by return ret. They are just ifs that you want to > ignore completely. > > julia
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