| Message ID | 20201028041819.2169003-10-kuhn.chenqun@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | silence the compiler warnings | expand |
On 10/28/20 5:18 AM, Chen Qun wrote: > When using -Wimplicit-fallthrough in our CFLAGS, the compiler showed warning: > ../hw/timer/renesas_tmr.c: In function ‘tmr_read’: > ../hw/timer/renesas_tmr.c:221:19: warning: this statement may fall through [-Wimplicit-fallthrough=] > 221 | } else if (ch == 0) {i > | ^ > ../hw/timer/renesas_tmr.c:224:5: note: here > 224 | case A_TCORB: > | ^~~~ > > Add the corresponding "fall through" comment to fix it. > > Reported-by: Euler Robot <euler.robot@huawei.com> > Signed-off-by: Chen Qun <kuhn.chenqun@huawei.com> > --- > Cc: Yoshinori Sato <ysato@users.sourceforge.jp> > Cc: Magnus Damm <magnus.damm@gmail.com> > --- > hw/timer/renesas_tmr.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/hw/timer/renesas_tmr.c b/hw/timer/renesas_tmr.c > index 446f2eacdd..e03a8155b2 100644 > --- a/hw/timer/renesas_tmr.c > +++ b/hw/timer/renesas_tmr.c > @@ -221,6 +221,7 @@ static uint64_t tmr_read(void *opaque, hwaddr addr, unsigned size) > } else if (ch == 0) { > return concat_reg(tmr->tcora); > } > + /* fall through */ > case A_TCORB: > if (size == 1) { > return tmr->tcorb[ch]; > You fixed A_TCORA but not A_TCORB... How the Euler Robot works? Like Coverity?
On 28/10/2020 10.59, Philippe Mathieu-Daudé wrote: > On 10/28/20 5:18 AM, Chen Qun wrote: >> When using -Wimplicit-fallthrough in our CFLAGS, the compiler showed warning: >> ../hw/timer/renesas_tmr.c: In function ‘tmr_read’: >> ../hw/timer/renesas_tmr.c:221:19: warning: this statement may fall through [-Wimplicit-fallthrough=] >> 221 | } else if (ch == 0) {i >> | ^ >> ../hw/timer/renesas_tmr.c:224:5: note: here >> 224 | case A_TCORB: >> | ^~~~ >> >> Add the corresponding "fall through" comment to fix it. >> >> Reported-by: Euler Robot <euler.robot@huawei.com> >> Signed-off-by: Chen Qun <kuhn.chenqun@huawei.com> >> --- >> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> >> Cc: Magnus Damm <magnus.damm@gmail.com> >> --- >> hw/timer/renesas_tmr.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/hw/timer/renesas_tmr.c b/hw/timer/renesas_tmr.c >> index 446f2eacdd..e03a8155b2 100644 >> --- a/hw/timer/renesas_tmr.c >> +++ b/hw/timer/renesas_tmr.c >> @@ -221,6 +221,7 @@ static uint64_t tmr_read(void *opaque, hwaddr addr, unsigned size) >> } else if (ch == 0) { >> return concat_reg(tmr->tcora); >> } >> + /* fall through */ >> case A_TCORB: >> if (size == 1) { >> return tmr->tcorb[ch]; >> > > You fixed A_TCORA but not A_TCORB... A_TCORB cannot fall through, since it always does a "return" in both branches of the if-statement. However, it also looks really odd that A_TCORA falls through to A_TCORB here and return that register value instead. Is this really intended? Yoshinori, could you please double-check whether this is a bug here, or intended? Thanks, Thomas
On Wed, 28 Oct 2020 at 15:07, Thomas Huth <thuth@redhat.com> wrote: > > On 28/10/2020 10.59, Philippe Mathieu-Daudé wrote: > > On 10/28/20 5:18 AM, Chen Qun wrote: > >> When using -Wimplicit-fallthrough in our CFLAGS, the compiler showed warning: > >> ../hw/timer/renesas_tmr.c: In function ‘tmr_read’: > >> ../hw/timer/renesas_tmr.c:221:19: warning: this statement may fall through [-Wimplicit-fallthrough=] > >> 221 | } else if (ch == 0) {i > >> | ^ > >> ../hw/timer/renesas_tmr.c:224:5: note: here > >> 224 | case A_TCORB: > >> | ^~~~ > >> > >> Add the corresponding "fall through" comment to fix it. > >> > >> Reported-by: Euler Robot <euler.robot@huawei.com> > >> Signed-off-by: Chen Qun <kuhn.chenqun@huawei.com> > >> --- > >> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> > >> Cc: Magnus Damm <magnus.damm@gmail.com> > >> --- > >> hw/timer/renesas_tmr.c | 1 + > >> 1 file changed, 1 insertion(+) > >> > >> diff --git a/hw/timer/renesas_tmr.c b/hw/timer/renesas_tmr.c > >> index 446f2eacdd..e03a8155b2 100644 > >> --- a/hw/timer/renesas_tmr.c > >> +++ b/hw/timer/renesas_tmr.c > >> @@ -221,6 +221,7 @@ static uint64_t tmr_read(void *opaque, hwaddr addr, unsigned size) > >> } else if (ch == 0) { > >> return concat_reg(tmr->tcora); > >> } > >> + /* fall through */ > >> case A_TCORB: > >> if (size == 1) { > >> return tmr->tcorb[ch]; > >> > > > > You fixed A_TCORA but not A_TCORB... > > A_TCORB cannot fall through, since it always does a "return" in both > branches of the if-statement. > > However, it also looks really odd that A_TCORA falls through to A_TCORB here > and return that register value instead. Is this really intended? Yoshinori, > could you please double-check whether this is a bug here, or intended? See the discussion in this thread: https://lore.kernel.org/qemu-devel/CAFEAcA8c2dywr=Zxz1ExAV-48JwFU5vbBDDfA=_KE98XamnXiA@mail.gmail.com/ from when Coverity spotting the fall-through. I think this cleanup patch from Yoshinori deals with the fall-through stuff by cleaning up that area of the timer device: https://lore.kernel.org/qemu-devel/20200711154242.41222-1-ysato@users.sourceforge.jp/ It just needs somebody to code-review it :-) thanks -- PMM
> -----Original Message----- > From: Philippe Mathieu-Daudé [mailto:philippe.mathieu.daude@gmail.com] > On Behalf Of Philippe Mathieu-Daudé > Sent: Wednesday, October 28, 2020 6:00 PM > To: Chenqun (kuhn) <kuhn.chenqun@huawei.com>; qemu-devel@nongnu.org; > qemu-trivial@nongnu.org > Cc: Zhanghailiang <zhang.zhanghailiang@huawei.com>; Yoshinori Sato > <ysato@users.sourceforge.jp>; Magnus Damm <magnus.damm@gmail.com>; > ganqixin <ganqixin@huawei.com>; Euler Robot <euler.robot@huawei.com> > Subject: Re: [PATCH 9/9] hw/timer/renesas_tmr: silence the compiler warnings > > On 10/28/20 5:18 AM, Chen Qun wrote: > > When using -Wimplicit-fallthrough in our CFLAGS, the compiler showed > warning: > > ../hw/timer/renesas_tmr.c: In function ‘tmr_read’: > > ../hw/timer/renesas_tmr.c:221:19: warning: this statement may fall through > [-Wimplicit-fallthrough=] > > 221 | } else if (ch == 0) {i > > | ^ > > ../hw/timer/renesas_tmr.c:224:5: note: here > > 224 | case A_TCORB: > > | ^~~~ > > > > Add the corresponding "fall through" comment to fix it. > > > > Reported-by: Euler Robot <euler.robot@huawei.com> > > Signed-off-by: Chen Qun <kuhn.chenqun@huawei.com> > > --- > > Cc: Yoshinori Sato <ysato@users.sourceforge.jp> > > Cc: Magnus Damm <magnus.damm@gmail.com> > > --- > > hw/timer/renesas_tmr.c | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/hw/timer/renesas_tmr.c b/hw/timer/renesas_tmr.c index > > 446f2eacdd..e03a8155b2 100644 > > --- a/hw/timer/renesas_tmr.c > > +++ b/hw/timer/renesas_tmr.c > > @@ -221,6 +221,7 @@ static uint64_t tmr_read(void *opaque, hwaddr addr, > unsigned size) > > } else if (ch == 0) { > > return concat_reg(tmr->tcora); > > } > > + /* fall through */ > > case A_TCORB: > > if (size == 1) { > > return tmr->tcorb[ch]; > > > > You fixed A_TCORA but not A_TCORB... > Hi Philippe, My first feeling is the same as you when this warning found. But, the number of branches for A_TCORA and A_TCORB is different. In A_TCORA case："} else if (ch == 0) {" In A_TCORB case："} else {" Obviously, A_TCOB have all return values. But A_TCOA is not, it need to fall through or break. > How the Euler Robot works? Like Coverity? No, unlike Coverity, Coverity is essentially a good discovery bug tool. But EulerRobot is a virtualization software quality automation project that integrates some tools and test suites such as gcc/clang make test, qemu ut, qtest, coccinelle scripts and avocado-vt. Thanks, Chen Qun
> -----Original Message----- > From: Peter Maydell [mailto:peter.maydell@linaro.org] > Sent: Thursday, October 29, 2020 4:15 AM > To: Thomas Huth <thuth@redhat.com> > Cc: Philippe Mathieu-Daudé <f4bug@amsat.org>; Chenqun (kuhn) > <kuhn.chenqun@huawei.com>; QEMU Developers <qemu-devel@nongnu.org>; > QEMU Trivial <qemu-trivial@nongnu.org>; Yoshinori Sato > <ysato@users.sourceforge.jp>; Magnus Damm <magnus.damm@gmail.com>; > Zhanghailiang <zhang.zhanghailiang@huawei.com>; ganqixin > <ganqixin@huawei.com>; Euler Robot <euler.robot@huawei.com> > Subject: Re: [PATCH 9/9] hw/timer/renesas_tmr: silence the compiler warnings > > On Wed, 28 Oct 2020 at 15:07, Thomas Huth <thuth@redhat.com> wrote: > > > > On 28/10/2020 10.59, Philippe Mathieu-Daudé wrote: > > > On 10/28/20 5:18 AM, Chen Qun wrote: > > >> When using -Wimplicit-fallthrough in our CFLAGS, the compiler showed > warning: > > >> ../hw/timer/renesas_tmr.c: In function ‘tmr_read’: > > >> ../hw/timer/renesas_tmr.c:221:19: warning: this statement may fall > through [-Wimplicit-fallthrough=] > > >> 221 | } else if (ch == 0) {i > > >> | ^ > > >> ../hw/timer/renesas_tmr.c:224:5: note: here > > >> 224 | case A_TCORB: > > >> | ^~~~ > > >> > > >> Add the corresponding "fall through" comment to fix it. > > >> > > >> Reported-by: Euler Robot <euler.robot@huawei.com> > > >> Signed-off-by: Chen Qun <kuhn.chenqun@huawei.com> > > >> --- > > >> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> > > >> Cc: Magnus Damm <magnus.damm@gmail.com> > > >> --- > > >> hw/timer/renesas_tmr.c | 1 + > > >> 1 file changed, 1 insertion(+) > > >> > > >> diff --git a/hw/timer/renesas_tmr.c b/hw/timer/renesas_tmr.c index > > >> 446f2eacdd..e03a8155b2 100644 > > >> --- a/hw/timer/renesas_tmr.c > > >> +++ b/hw/timer/renesas_tmr.c > > >> @@ -221,6 +221,7 @@ static uint64_t tmr_read(void *opaque, hwaddr > addr, unsigned size) > > >> } else if (ch == 0) { > > >> return concat_reg(tmr->tcora); > > >> } > > >> + /* fall through */ > > >> case A_TCORB: > > >> if (size == 1) { > > >> return tmr->tcorb[ch]; > > >> > > > > > > You fixed A_TCORA but not A_TCORB... > > > > A_TCORB cannot fall through, since it always does a "return" in both > > branches of the if-statement. > > > > However, it also looks really odd that A_TCORA falls through to > > A_TCORB here and return that register value instead. Is this really > > intended? Yoshinori, could you please double-check whether this is a bug here, > or intended? > > See the discussion in this thread: > https://lore.kernel.org/qemu-devel/CAFEAcA8c2dywr=Zxz1ExAV-48JwFU5vbBD > DfA=_KE98XamnXiA@mail.gmail.com/ > from when Coverity spotting the fall-through. > > I think this cleanup patch from Yoshinori deals with the fall-through stuff by > cleaning up that area of the timer device: > https://lore.kernel.org/qemu-devel/20200711154242.41222-1-ysato@users.so > urceforge.jp/ > It just needs somebody to code-review it :-) This cleanup patch has been modified more thoroughly, so let's wait for it merge :-) Thanks, Chen Qun
diff --git a/hw/timer/renesas_tmr.c b/hw/timer/renesas_tmr.c index 446f2eacdd..e03a8155b2 100644 --- a/hw/timer/renesas_tmr.c +++ b/hw/timer/renesas_tmr.c @@ -221,6 +221,7 @@ static uint64_t tmr_read(void *opaque, hwaddr addr, unsigned size) } else if (ch == 0) { return concat_reg(tmr->tcora); } + /* fall through */ case A_TCORB: if (size == 1) { return tmr->tcorb[ch];
When using -Wimplicit-fallthrough in our CFLAGS, the compiler showed warning: ../hw/timer/renesas_tmr.c: In function ‘tmr_read’: ../hw/timer/renesas_tmr.c:221:19: warning: this statement may fall through [-Wimplicit-fallthrough=] 221 | } else if (ch == 0) {i | ^ ../hw/timer/renesas_tmr.c:224:5: note: here 224 | case A_TCORB: | ^~~~ Add the corresponding "fall through" comment to fix it. Reported-by: Euler Robot <euler.robot@huawei.com> Signed-off-by: Chen Qun <kuhn.chenqun@huawei.com> --- Cc: Yoshinori Sato <ysato@users.sourceforge.jp> Cc: Magnus Damm <magnus.damm@gmail.com> --- hw/timer/renesas_tmr.c | 1 + 1 file changed, 1 insertion(+)