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Message-ID: <20221227095517.mzjmqse5wvaielev@pengutronix.de>
Date: Tue, 27 Dec 2022 10:55:17 +0100
From: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To: Julia Lawall <julia.lawall@...ia.fr>
Cc: Nicolas Palix <nicolas.palix@...g.fr>,
linux-kernel@...r.kernel.org, kernel@...gutronix.de, cocci@...ia.fr
Subject: Re: coccinelle: How to remove a return at the end of a void function?
Hello Julia,
On Mon, Dec 26, 2022 at 05:02:35PM +0100, Julia Lawall wrote:
> On Sun, 25 Dec 2022, Uwe Kleine-König wrote:
>
> > Hello Julia,
> >
> > first of all thanks for your quick answer.
> >
> > On Sat, Dec 24, 2022 at 01:28:04PM +0100, Julia Lawall wrote:
> > > On Sat, 24 Dec 2022, Uwe Kleine-König wrote:
> > > > A simplified spatch looks as follows:
> > > >
> > > > -------->8--------
> > > > virtual patch
> > > >
> > > > @p1@
> > > > identifier pdev;
> > > > @@
> > > > -int
> > > > +void
> > > > rtsx_usb_sdmmc_drv_remove(struct platform_device *pdev) {
> > > > <...
> > > > -return 0;
> > > > +return;
> > > > ...>
> > > > }
> > > > -------->8--------
> > > >
> > > > This results in:
> > > >
> > > > -------->8--------
> > > > diff -u -p a/drivers/mmc/host/rtsx_usb_sdmmc.c b/drivers/mmc/host/rtsx_usb_sdmmc.c
> > > > --- a/drivers/mmc/host/rtsx_usb_sdmmc.c
> > > > +++ b/drivers/mmc/host/rtsx_usb_sdmmc.c
> > > > @@ -1379,13 +1379,13 @@ static int rtsx_usb_sdmmc_drv_probe(stru
> > > > return 0;
> > > > }
> > > >
> > > > -static int rtsx_usb_sdmmc_drv_remove(struct platform_device *pdev)
> > > > +static void rtsx_usb_sdmmc_drv_remove(struct platform_device *pdev)
> > > > {
> > > > struct rtsx_usb_sdmmc *host = platform_get_drvdata(pdev);
> > > > struct mmc_host *mmc;
> > > >
> > > > if (!host)
> > > > - return 0;
> > > > + return;
> > > >
> > > > mmc = host->mmc;
> > > > host->host_removal = true;
> > > > @@ -1416,7 +1416,7 @@ static int rtsx_usb_sdmmc_drv_remove(str
> > > > dev_dbg(&(pdev->dev),
> > > > ": Realtek USB SD/MMC module has been removed\n");
> > > >
> > > > - return 0;
> > > > + return;
> > > > }
> > > >
> > > > #ifdef CONFIG_PM
> > > > -------->8--------
> > > >
> > > > which is as intended. Now I want to remove the useless "return;" at the
> > > > end of the function, however adding
> > > >
> > > > -------->8--------
> > > > @p2 depends on p1@
> > > > identifier pdev;
> > > > @@
> > > > void rtsx_usb_sdmmc_drv_remove(struct platform_device *pdev) {
> > > > ...
> > > > -return;
> > > > }
> > > > -------->8--------
> > > >
> > > > to the spatch doesn't (only) do the intended:
> > >
> > > The problem is that Coccinelle is following the control-flow through the
> > > function, and all of the returns are at the end of a control.flow path.
> > > The simple, hacky solution is to change the return;s into some function
> > > call Return();, then do like the above for Return(); and then change the
> > > Return();s back to return;s
> >
> > OK, I tried, but somehow coccinelle refuse to work after I introduced
> > Return(), even replacing them by return; doesn't work:
> >
> > -------->8--------
> > virtual patch
> >
> > @p1@
> > identifier pdev;
> > @@
> > -int
> > +void
> > rtsx_usb_sdmmc_drv_remove(struct platform_device *pdev) {
> > ...
> > -return 0;
> > +Return();
> > ...
> > }
> >
> > @p2@
> > identifier pdev;
> > @@
> > void rtsx_usb_sdmmc_drv_remove(struct platform_device *pdev) {
> > ...
> > -Return();
> > +return;
> > ...
> > }
>
> The problem is that a control-flow path at this point can have multiple
> calls to Return(); You pattern only matches when every control-flow path
> through the code has exactly one Return().
Ah, ok. This wasn't clear to me from reading the documentation (e.g.
https://coccinelle.gitlabpages.inria.fr/website/docs/main_grammar.html)
> You should have one rule that removes the final Return();
>
> @p2@
> identifier pdev;
> @@
> void rtsx_usb_sdmmc_drv_remove(struct platform_device *pdev) {
> ...
> -Return();
> }
>
> Then another rule to remove the others:
>
> @p2@
> identifier pdev;
> @@
> void rtsx_usb_sdmmc_drv_remove(struct platform_device *pdev) {
> <...
> -Return();
> +return;
> ...>
> }
I now have
-------->8--------
virtual patch
@p1@
identifier pdev;
@@
-int
+void
rtsx_usb_sdmmc_drv_remove(struct platform_device *pdev) {
...
-return 0;
+Return();
...
}
@p2@
identifier pdev;
@@
void rtsx_usb_sdmmc_drv_remove(struct platform_device *pdev) {
...
-Return();
}
@p3@
identifier pdev;
@@
void rtsx_usb_sdmmc_drv_remove(struct platform_device *pdev) {
<...
-Return();
+return;
...>
}
-------->8--------
But there p2 suffers from the same problem and only matches
code paths with exactly 1 Return(). So the above results in
-------->8--------
diff -u -p a/drivers/mmc/host/rtsx_usb_sdmmc.c b/drivers/mmc/host/rtsx_usb_sdmmc.c
--- a/drivers/mmc/host/rtsx_usb_sdmmc.c
+++ b/drivers/mmc/host/rtsx_usb_sdmmc.c
@@ -1379,13 +1379,13 @@ static int rtsx_usb_sdmmc_drv_probe(stru
return 0;
}
-static int rtsx_usb_sdmmc_drv_remove(struct platform_device *pdev)
+static void rtsx_usb_sdmmc_drv_remove(struct platform_device *pdev)
{
struct rtsx_usb_sdmmc *host = platform_get_drvdata(pdev);
struct mmc_host *mmc;
if (!host)
- return 0;
+ return;
mmc = host->mmc;
host->host_removal = true;
@@ -1416,7 +1416,7 @@ static int rtsx_usb_sdmmc_drv_remove(str
dev_dbg(&(pdev->dev),
": Realtek USB SD/MMC module has been removed\n");
- return 0;
+ return;
}
#ifdef CONFIG_PM
-------->8--------
and only if I remove the "if (!host) return 0;" block before patch
generation, the final return is also dropped.
I think this is good enough for me, as there are not too many cases like
the above. If there is spatch that does the desired change (i.e.
-------->8--------
diff -u -p a/drivers/mmc/host/rtsx_usb_sdmmc.c b/drivers/mmc/host/rtsx_usb_sdmmc.c
--- a/drivers/mmc/host/rtsx_usb_sdmmc.c
+++ b/drivers/mmc/host/rtsx_usb_sdmmc.c
@@ -1379,13 +1379,11 @@ static int rtsx_usb_sdmmc_drv_probe(stru
return 0;
}
-static int rtsx_usb_sdmmc_drv_remove(struct platform_device *pdev)
+static void rtsx_usb_sdmmc_drv_remove(struct platform_device *pdev)
{
struct rtsx_usb_sdmmc *host = platform_get_drvdata(pdev);
struct mmc_host *mmc;
if (!host)
- return 0;
+ return;
mmc = host->mmc;
host->host_removal = true;
@@ -1416,7 +1416,7 @@ static int rtsx_usb_sdmmc_drv_remove(str
dev_dbg(&(pdev->dev),
": Realtek USB SD/MMC module has been removed\n");
-
- return 0;
}
#ifdef CONFIG_PM
-------->8--------
) I'd be happy to hear and learn about it.
Thanks
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |
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