| Message ID | 20181021171414.22674-3-miguel.ojeda.sandonis@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Compiler Attributes: __fallthrough | expand |
On Sun, 2018-10-21 at 19:14 +0200, Miguel Ojeda wrote: > Let gcc know these cases are meant to fall through to the next label > by annotating them with the new __fallthrough statement attribute; > and remove the comment since it conveys the same information > (which was also parsed by gcc to suppress the warning). Instead of many individual conversion patches, perhaps a script to do all the conversions at once. Maybe: pattern='(?:\/\*\s*fall(?:\s*|\s*\-\s*)thr(?:u|ough)\s*\*\/|\/\/\s*fall\s*thr(?:u|ough)\s*$)' git grep -P -i --name-only "$pattern" -- '*.[ch]' | xargs perl -p -i -e "s/$pattern/__fallthrough;/gi"
On Sun, Oct 21, 2018 at 8:11 PM Joe Perches <joe@perches.com> wrote: > > On Sun, 2018-10-21 at 19:14 +0200, Miguel Ojeda wrote: > > Let gcc know these cases are meant to fall through to the next label > > by annotating them with the new __fallthrough statement attribute; > > and remove the comment since it conveys the same information > > (which was also parsed by gcc to suppress the warning). > > Instead of many individual conversion patches, > perhaps a script to do all the conversions at once. Note that this was only an example of the attribute (some people asked for an example when introducing another one, so I preemptively did it for this one). Doing the conversion (and how :-) I left it for afterwards, if people agree with the attribute. > > Maybe: > > pattern='(?:\/\*\s*fall(?:\s*|\s*\-\s*)thr(?:u|ough)\s*\*\/|\/\/\s*fall\s*thr(?:u|ough)\s*$)' > git grep -P -i --name-only "$pattern" -- '*.[ch]' | > xargs perl -p -i -e "s/$pattern/__fallthrough;/gi" By the way, I checked first if coccinelle could match input comments, but it doesn't, according to Julia. I am also thinking whether a compiler plugin could easily do this, but I don't have my hopes high given these are comments... Also, regardless of how it is done, the patches need to be sent individually to maintainers, no? I have a vague memory that big & automated conversions were a bit frozen upon in the kernel. Greg...? Cheers, Miguel
On Sun, Oct 21, 2018 at 10:14 AM, Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> wrote: > Let gcc know these cases are meant to fall through to the next label > by annotating them with the new __fallthrough statement attribute; > and remove the comment since it conveys the same information > (which was also parsed by gcc to suppress the warning). > > Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> > --- > drivers/auxdisplay/panel.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/auxdisplay/panel.c b/drivers/auxdisplay/panel.c > index 21b9b2f2470a..0755034e49ba 100644 > --- a/drivers/auxdisplay/panel.c > +++ b/drivers/auxdisplay/panel.c > @@ -1367,7 +1367,7 @@ static void panel_process_inputs(void) > break; > input->rise_timer = 0; > input->state = INPUT_ST_RISING; > - /* fall through */ > + __fallthrough; > case INPUT_ST_RISING: > if ((phys_curr & input->mask) != input->value) { > input->state = INPUT_ST_LOW; > @@ -1380,11 +1380,11 @@ static void panel_process_inputs(void) > } > input->high_timer = 0; > input->state = INPUT_ST_HIGH; > - /* fall through */ > + __fallthrough; > case INPUT_ST_HIGH: > if (input_state_high(input)) > break; > - /* fall through */ > + __fallthrough; > case INPUT_ST_FALLING: > input_state_falling(input); > } > -- > 2.17.1 > I would prefer we continue to use the comment style until we've got confirmed support for (at least) Clang, Coverity, CPPcheck, smatch, and eclipse. -Kees
On Mon, 2018-10-22 at 11:51 +0200, Miguel Ojeda wrote: > On Sun, Oct 21, 2018 at 8:11 PM Joe Perches <joe@perches.com> wrote: > > On Sun, 2018-10-21 at 19:14 +0200, Miguel Ojeda wrote: > > > Let gcc know these cases are meant to fall through to the next label > > > by annotating them with the new __fallthrough statement attribute; > > > and remove the comment since it conveys the same information > > > (which was also parsed by gcc to suppress the warning). > > > > Instead of many individual conversion patches, > > perhaps a script to do all the conversions at once. > > Note that this was only an example of the attribute (some people asked > for an example when introducing another one, so I preemptively did it > for this one). > > Doing the conversion (and how :-) I left it for afterwards, if people > agree with the attribute. > > > Maybe: > > > > pattern='(?:\/\*\s*fall(?:\s*|\s*\-\s*)thr(?:u|ough)\s*\*\/|\/\/\s*fall\s*thr(?:u|ough)\s*$)' > > git grep -P -i --name-only "$pattern" -- '*.[ch]' | > > xargs perl -p -i -e "s/$pattern/__fallthrough;/gi" > > By the way, I checked first if coccinelle could match input comments, > but it doesn't, according to Julia. I am also thinking whether a > compiler plugin could easily do this, but I don't have my hopes high > given these are comments... > > Also, regardless of how it is done, the patches need to be sent > individually to maintainers, no? Not really no. For instance the spdx license treewide change. commit b24413180f5600bcb3bb70fbed5cf186b60864bd > I have a vague memory that big & > automated conversions were a bit frozen upon in the kernel. Greg...? There really needs to be some method to do treewide conversions without involving multiple maintainers. It'd be a good topic for a maintainer summit one day.
Hi Dan, On Tue, Oct 23, 2018 at 7:37 AM Dan Carpenter <dan.carpenter@oracle.com> wrote: > > On Mon, Oct 22, 2018 at 07:10:02AM -0700, Kees Cook wrote: > > I would prefer we continue to use the comment style until we've got > > confirmed support for (at least) Clang, Coverity, CPPcheck, smatch, > > and eclipse. > > Clang and Smatch don't support fall throught comments. Coverity > supports both. CPPcheck is unknown. > > Eclipse doesn't support attributes. So it's just Eclipse and maybe > CPP check. Thanks for checking! Let's wait then a few months and see if we can get cppcheck/Eclipse to support it. Cheers, Miguel
On Fri, Nov 2, 2018 at 11:49 AM Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> wrote: > > Thanks for checking! Let's wait then a few months and see if we can > get cppcheck/Eclipse to support it. In the meantime, saved here too: https://github.com/ojeda/linux/tree/compiler-attributes-fallthrough rebased on top of e468f5c06b5e ("Merge tag 'compiler-attributes-for-linus-4.20-rc1' of https://github.com/ojeda/linux"). Cheers, Miguel
diff --git a/drivers/auxdisplay/panel.c b/drivers/auxdisplay/panel.c index 21b9b2f2470a..0755034e49ba 100644 --- a/drivers/auxdisplay/panel.c +++ b/drivers/auxdisplay/panel.c @@ -1367,7 +1367,7 @@ static void panel_process_inputs(void) break; input->rise_timer = 0; input->state = INPUT_ST_RISING; - /* fall through */ + __fallthrough; case INPUT_ST_RISING: if ((phys_curr & input->mask) != input->value) { input->state = INPUT_ST_LOW; @@ -1380,11 +1380,11 @@ static void panel_process_inputs(void) } input->high_timer = 0; input->state = INPUT_ST_HIGH; - /* fall through */ + __fallthrough; case INPUT_ST_HIGH: if (input_state_high(input)) break; - /* fall through */ + __fallthrough; case INPUT_ST_FALLING: input_state_falling(input); }
Let gcc know these cases are meant to fall through to the next label by annotating them with the new __fallthrough statement attribute; and remove the comment since it conveys the same information (which was also parsed by gcc to suppress the warning). Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> --- drivers/auxdisplay/panel.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)