* [Cocci] continue statement of death?
@ 2019-09-12 1:51 David Young
2019-09-12 8:27 ` Julia Lawall
2019-09-12 13:37 ` Markus Elfring
0 siblings, 2 replies; 5+ messages in thread
From: David Young @ 2019-09-12 1:51 UTC (permalink / raw)
To: cocci
Today I built and installed Coccinelle 1.0.7 on NetBSD.
I am processing this fragment of NetBSD kernel code, `tbr_timeout.c`,
| /*
| * tbr_timeout goes through the interface list, and kicks the drivers
| * if necessary.
| */
| static void
| tbr_timeout(void *arg)
| {
| struct ifnet *ifp;
| int active, s;
|
| active = 0;
| s = splnet();
| for (ifp = TAILQ_FIRST(&ifnet); ifp; ifp = TAILQ_NEXT(ifp, if_list)) {
| if (!TBR_IS_ENABLED(&ifp->if_snd))
| #if 1
| continue;
| #endif
| active++;
| if (!IFQ_IS_EMPTY(&ifp->if_snd) && ifp->if_start != NULL)
| (*ifp->if_start)(ifp);
| }
| splx(s);
| if (active > 0)
| CALLOUT_RESET(&tbr_callout, 1, tbr_timeout, NULL);
| else
| tbr_timer = 0; /* don't need tbr_timer anymore */
| }
|
using this semantic patch, `tailq.spatch`,
| @@
| identifier I, N;
| expression H;
| statement S;
| iterator name TAILQ_FOREACH;
| @@
|
| - for (I = TAILQ_FIRST(H); I != NULL; I = TAILQ_NEXT(I, N)) S
| + TAILQ_FOREACH(I, H, N) S
I find that if the condition in the `#if` directive is 1, then `spatch
--sp-file tailq.spatch -o tbr_timeout.spatch tbr_timeout.c` runs for
a few minutes before running out of memory. `spatch` prints this
mysterious message when it starts:
(ONCE) already tagged but only removed, so safe
If I turn the condition to 0, however, spatch instantaneously prints the
result with the `for (...)` clause turned to `TAILQ_FOREACH(...)`, as
expected. I don't see the mysterious `(ONCE) ...` message.
Any ideas why `continue;` is troublesome to spatch?
Dave
--
David Young
dyoung@pobox.com Urbana, IL (217) 721-9981
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^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [Cocci] continue statement of death?
2019-09-12 1:51 [Cocci] continue statement of death? David Young
@ 2019-09-12 8:27 ` Julia Lawall
2019-09-12 13:37 ` Markus Elfring
1 sibling, 0 replies; 5+ messages in thread
From: Julia Lawall @ 2019-09-12 8:27 UTC (permalink / raw)
To: David Young; +Cc: cocci
On Wed, 11 Sep 2019, David Young wrote:
> Today I built and installed Coccinelle 1.0.7 on NetBSD.
>
> I am processing this fragment of NetBSD kernel code, `tbr_timeout.c`,
>
> | /*
> | * tbr_timeout goes through the interface list, and kicks the drivers
> | * if necessary.
> | */
> | static void
> | tbr_timeout(void *arg)
> | {
> | struct ifnet *ifp;
> | int active, s;
> |
> | active = 0;
> | s = splnet();
> | for (ifp = TAILQ_FIRST(&ifnet); ifp; ifp = TAILQ_NEXT(ifp, if_list)) {
> | if (!TBR_IS_ENABLED(&ifp->if_snd))
> | #if 1
> | continue;
> | #endif
> | active++;
> | if (!IFQ_IS_EMPTY(&ifp->if_snd) && ifp->if_start != NULL)
> | (*ifp->if_start)(ifp);
> | }
> | splx(s);
> | if (active > 0)
> | CALLOUT_RESET(&tbr_callout, 1, tbr_timeout, NULL);
> | else
> | tbr_timer = 0; /* don't need tbr_timer anymore */
> | }
> |
>
> using this semantic patch, `tailq.spatch`,
>
> | @@
> | identifier I, N;
> | expression H;
> | statement S;
> | iterator name TAILQ_FOREACH;
> | @@
> |
> | - for (I = TAILQ_FIRST(H); I != NULL; I = TAILQ_NEXT(I, N)) S
> | + TAILQ_FOREACH(I, H, N) S
>
> I find that if the condition in the `#if` directive is 1, then `spatch
> --sp-file tailq.spatch -o tbr_timeout.spatch tbr_timeout.c` runs for
> a few minutes before running out of memory. `spatch` prints this
> mysterious message when it starts:
>
> (ONCE) already tagged but only removed, so safe
>
> If I turn the condition to 0, however, spatch instantaneously prints the
> result with the `for (...)` clause turned to `TAILQ_FOREACH(...)`, as
> expected. I don't see the mysterious `(ONCE) ...` message.
>
> Any ideas why `continue;` is troublesome to spatch?
I'm looking into it. It seems to be a pretty printing problem.
julia
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^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [Cocci] continue statement of death?
2019-09-12 1:51 [Cocci] continue statement of death? David Young
2019-09-12 8:27 ` Julia Lawall
@ 2019-09-12 13:37 ` Markus Elfring
2019-09-12 14:49 ` David Young
2019-09-12 14:51 ` Julia Lawall
1 sibling, 2 replies; 5+ messages in thread
From: Markus Elfring @ 2019-09-12 13:37 UTC (permalink / raw)
To: cocci, David Young
> - for (I = TAILQ_FIRST(H); I != NULL; I = TAILQ_NEXT(I, N)) S
> + TAILQ_FOREACH(I, H, N) S
Can it make sense to avoid touching the (compound) statement at the end
so that only the loop header would be replaced?
-for (I = TAILQ_FIRST(H); I != NULL; I = TAILQ_NEXT(I, N))
+TAILQ_FOREACH(I, H, N)
S
Regards,
Markus
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Cocci] continue statement of death?
2019-09-12 13:37 ` Markus Elfring
@ 2019-09-12 14:49 ` David Young
2019-09-12 14:51 ` Julia Lawall
1 sibling, 0 replies; 5+ messages in thread
From: David Young @ 2019-09-12 14:49 UTC (permalink / raw)
To: cocci
On Thu, Sep 12, 2019 at 03:37:42PM +0200, Markus Elfring wrote:
> > - for (I = TAILQ_FIRST(H); I != NULL; I = TAILQ_NEXT(I, N)) S
> > + TAILQ_FOREACH(I, H, N) S
>
> Can it make sense to avoid touching the (compound) statement at the end
> so that only the loop header would be replaced?
>
> -for (I = TAILQ_FIRST(H); I != NULL; I = TAILQ_NEXT(I, N))
> +TAILQ_FOREACH(I, H, N)
> S
Sure, that's a reasonable way to refactor the semantic patch. That
works around the bug, too.
Dave
--
David Young
dyoung@pobox.com Urbana, IL (217) 721-9981
_______________________________________________
Cocci mailing list
Cocci@systeme.lip6.fr
https://systeme.lip6.fr/mailman/listinfo/cocci
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Cocci] continue statement of death?
2019-09-12 13:37 ` Markus Elfring
2019-09-12 14:49 ` David Young
@ 2019-09-12 14:51 ` Julia Lawall
1 sibling, 0 replies; 5+ messages in thread
From: Julia Lawall @ 2019-09-12 14:51 UTC (permalink / raw)
To: Markus Elfring; +Cc: cocci
On Thu, 12 Sep 2019, Markus Elfring wrote:
> > - for (I = TAILQ_FIRST(H); I != NULL; I = TAILQ_NEXT(I, N)) S
> > + TAILQ_FOREACH(I, H, N) S
>
> Can it make sense to avoid touching the (compound) statement at the end
> so that only the loop header would be replaced?
>
> -for (I = TAILQ_FIRST(H); I != NULL; I = TAILQ_NEXT(I, N))
> +TAILQ_FOREACH(I, H, N)
> S
This does indeed seem to avoid the problem. Nevertheless, it is useful to
have the problem reported in the first place.
julia
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^ permalink raw reply [flat|nested] 5+ messages in thread
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2019-09-12 1:51 [Cocci] continue statement of death? David Young
2019-09-12 8:27 ` Julia Lawall
2019-09-12 13:37 ` Markus Elfring
2019-09-12 14:49 ` David Young
2019-09-12 14:51 ` Julia Lawall
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