On Thu, Nov 12, 2020 at 1:48 PM Moore, Robert <robert.mo...@intel.com> wrote: > > > > -----Original Message----- > From: Nick Desaulniers <ndesaulni...@google.com> > Sent: Thursday, November 12, 2020 11:31 AM > To: Moore, Robert <robert.mo...@intel.com> > Cc: Kaneda, Erik <erik.kan...@intel.com>; Wysocki, Rafael J > <rafael.j.wyso...@intel.com>; Gustavo A . R . Silva <gustavo...@kernel.org>; > clang-built-li...@googlegroups.com; Len Brown <l...@kernel.org>; > linux-a...@vger.kernel.org; de...@acpica.org; linux-kernel@vger.kernel.org > Subject: Re: [PATCH] ACPICA: fix -Wfallthrough > > On Thu, Nov 12, 2020 at 7:13 AM Moore, Robert <robert.mo...@intel.com> wrote: > > > > > > > > -----Original Message----- > > From: Nick Desaulniers <ndesaulni...@google.com> > > Sent: Wednesday, November 11, 2020 10:48 AM > > To: Moore, Robert <robert.mo...@intel.com> > > Cc: Kaneda, Erik <erik.kan...@intel.com>; Wysocki, Rafael J > > <rafael.j.wyso...@intel.com>; Gustavo A . R . Silva > > <gustavo...@kernel.org>; clang-built-li...@googlegroups.com; Len Brown > > <l...@kernel.org>; linux-a...@vger.kernel.org; de...@acpica.org; > > linux-kernel@vger.kernel.org > > Subject: Re: [PATCH] ACPICA: fix -Wfallthrough > > > > On Wed, Nov 11, 2020 at 7:15 AM Moore, Robert <robert.mo...@intel.com> > > wrote: > > > > > > Yes, but: isn't the "fallthrough" keyword compiler-specific? That is the > > > problem for us. > > > > It's not a keyword. > > > > It's a preprocessor macro that expands to > > __attribute__((__fallthrough__)) for compilers that support it. For > > compilers that do not, it expands to nothing. Both GCC 7+ and Clang > > support this attribute. Which other compilers that support > > -Wimplicit-fallthrough do you care to support? > > > > We need to support MSVC 2017 -- which apparently does not support this. > > In which case, the macro is not expanded to a compiler attribute the compiler > doesn't support. Please see also its definition in > include/linux/compiler_attributes.h. > > From what I can tell, MSVC does not warn on implicit fallthrough, so there's > no corresponding attribute (or comment) to disable the warning in MSVC. > > That doesn't mean this code is not portable to MSVC; a macro that expands to > nothing should not be a problem. > > Based on > https://docs.microsoft.com/en-us/cpp/code-quality/c26819?view=msvc-160 > https://developercommunity.visualstudio.com/idea/423975/issue-compiler-warning-when-using-implicit-fallthr.html > it sounds like MSVC 2019 will be able to warn, for C++ mode, which will rely > on the C++ style attribute to annotate intentional fallthrough. > > Can you confirm how this does not work for MSVC 2017? > > 1>c:\acpica\source\components\utilities\utdelete.c(270): warning C4013: > '__attribute__' undefined; assuming extern returning int > 1>c:\acpica\source\components\utilities\utdelete.c(270): error C2065: > '__fallthrough__': undeclared identifier > 1>c:\acpica\source\components\utilities\utdelete.c(272): error C2143: syntax > error: missing ';' before 'case'
Thank you for the explicit diagnostics observed. Something fishy is going on though, https://godbolt.org/z/Gbxbxa is how I expect MSVC to handle include/linux/compiler_attributes.h. The C preprocessor should make it such that MSVC never sees `__attribute__` or `__fallthrough__`; that it does begs the question. That would seem to imply that `#if __has_attribute(__fallthrough__)` somehow evaluates to true on MSVC, but my godbolt link shows it does not. Could the upstream ACPICA project be #define'ing something that could be altering this? (Or not #define'ing something?) Worst case, we could do as Joe Perches suggested and disable -Wfallthrough for drivers/acpi/acpica/. > > > > Bob > > > > > > > > > -----Original Message----- > > > From: ndesaulniers via sendgmr > > > <ndesaulni...@ndesaulniers1.mtv.corp.google.com> On Behalf Of Nick > > > Desaulniers > > > Sent: Tuesday, November 10, 2020 6:12 PM > > > To: Moore, Robert <robert.mo...@intel.com>; Kaneda, Erik > > > <erik.kan...@intel.com>; Wysocki, Rafael J > > > <rafael.j.wyso...@intel.com>; Gustavo A . R . Silva > > > <gustavo...@kernel.org> > > > Cc: clang-built-li...@googlegroups.com; Nick Desaulniers > > > <ndesaulni...@google.com>; Len Brown <l...@kernel.org>; > > > linux-a...@vger.kernel.org; de...@acpica.org; > > > linux-kernel@vger.kernel.org > > > Subject: [PATCH] ACPICA: fix -Wfallthrough > > > > > > The "fallthrough" pseudo-keyword was added as a portable way to denote > > > intentional fallthrough. This code seemed to be using a mix of > > > fallthrough comments that GCC recognizes, and some kind of lint marker. > > > I'm guessing that linter hasn't been run in a while from the mixed use of > > > the marker vs comments. > > > > > > Signed-off-by: Nick Desaulniers <ndesaulni...@google.com> > > > --- > > > drivers/acpi/acpica/dscontrol.c | 3 +-- > > > drivers/acpi/acpica/dswexec.c | 4 +--- > > > drivers/acpi/acpica/dswload.c | 3 +-- > > > drivers/acpi/acpica/dswload2.c | 3 +-- > > > drivers/acpi/acpica/exfldio.c | 3 +-- > > > drivers/acpi/acpica/exresop.c | 5 ++--- > > > drivers/acpi/acpica/exstore.c | 6 ++---- > > > drivers/acpi/acpica/hwgpe.c | 3 +-- > > > drivers/acpi/acpica/utdelete.c | 3 +-- > > > drivers/acpi/acpica/utprint.c | 2 +- > > > 10 files changed, 12 insertions(+), 23 deletions(-) > > > > > > diff --git a/drivers/acpi/acpica/dscontrol.c > > > b/drivers/acpi/acpica/dscontrol.c index 4b5b6e859f62..1e75e5fbfd19 > > > 100644 > > > --- a/drivers/acpi/acpica/dscontrol.c > > > +++ b/drivers/acpi/acpica/dscontrol.c > > > @@ -61,8 +61,7 @@ acpi_ds_exec_begin_control_op(struct acpi_walk_state > > > *walk_state, > > > break; > > > } > > > } > > > - > > > - /*lint -fallthrough */ > > > + fallthrough; > > > > > > case AML_IF_OP: > > > /* > > > diff --git a/drivers/acpi/acpica/dswexec.c > > > b/drivers/acpi/acpica/dswexec.c index 1d4f8c81028c..e8c32d4fe55f > > > 100644 > > > --- a/drivers/acpi/acpica/dswexec.c > > > +++ b/drivers/acpi/acpica/dswexec.c > > > @@ -597,9 +597,7 @@ acpi_status acpi_ds_exec_end_op(struct > > > acpi_walk_state *walk_state) > > > if (ACPI_FAILURE(status)) { > > > break; > > > } > > > - > > > - /* Fall through */ > > > - /*lint -fallthrough */ > > > + fallthrough; > > > > > > case AML_INT_EVAL_SUBTREE_OP: > > > > > > diff --git a/drivers/acpi/acpica/dswload.c > > > b/drivers/acpi/acpica/dswload.c index 27069325b6de..afc663c3742d > > > 100644 > > > --- a/drivers/acpi/acpica/dswload.c > > > +++ b/drivers/acpi/acpica/dswload.c > > > @@ -223,8 +223,7 @@ acpi_ds_load1_begin_op(struct acpi_walk_state > > > *walk_state, > > > parse_flags & ACPI_PARSE_MODULE_LEVEL)) { > > > break; > > > } > > > - > > > - /*lint -fallthrough */ > > > + fallthrough; > > > > > > default: > > > > > > diff --git a/drivers/acpi/acpica/dswload2.c > > > b/drivers/acpi/acpica/dswload2.c index edadbe146506..1b794b6ba072 > > > 100644 > > > --- a/drivers/acpi/acpica/dswload2.c > > > +++ b/drivers/acpi/acpica/dswload2.c > > > @@ -213,8 +213,7 @@ acpi_ds_load2_begin_op(struct acpi_walk_state > > > *walk_state, > > > parse_flags & ACPI_PARSE_MODULE_LEVEL)) { > > > break; > > > } > > > - > > > - /*lint -fallthrough */ > > > + fallthrough; > > > > > > default: > > > > > > diff --git a/drivers/acpi/acpica/exfldio.c > > > b/drivers/acpi/acpica/exfldio.c index ade35ff1c7ba..9d1cabe0fed9 > > > 100644 > > > --- a/drivers/acpi/acpica/exfldio.c > > > +++ b/drivers/acpi/acpica/exfldio.c > > > @@ -433,8 +433,7 @@ acpi_ex_field_datum_io(union acpi_operand_object > > > *obj_desc, > > > * Now that the Bank has been selected, fall through to > > > the > > > * region_field case and write the datum to the Operation > > > Region > > > */ > > > - > > > - /*lint -fallthrough */ > > > + fallthrough; > > > > > > case ACPI_TYPE_LOCAL_REGION_FIELD: > > > /* > > > diff --git a/drivers/acpi/acpica/exresop.c > > > b/drivers/acpi/acpica/exresop.c index 4d1b22971d58..df48faa9a551 > > > 100644 > > > --- a/drivers/acpi/acpica/exresop.c > > > +++ b/drivers/acpi/acpica/exresop.c > > > @@ -197,8 +197,7 @@ acpi_ex_resolve_operands(u16 opcode, > > > case ACPI_REFCLASS_DEBUG: > > > > > > target_op = AML_DEBUG_OP; > > > - > > > - /*lint -fallthrough */ > > > + fallthrough; > > > > > > case ACPI_REFCLASS_ARG: > > > case ACPI_REFCLASS_LOCAL: > > > @@ -264,7 +263,7 @@ acpi_ex_resolve_operands(u16 opcode, > > > * Else not a string - fall through to the normal > > > Reference > > > * case below > > > */ > > > - /*lint -fallthrough */ > > > + fallthrough; > > > > > > case ARGI_REFERENCE: /* References: */ > > > case ARGI_INTEGER_REF: > > > diff --git a/drivers/acpi/acpica/exstore.c > > > b/drivers/acpi/acpica/exstore.c index 3adc0a29d890..2067baa7c120 > > > 100644 > > > --- a/drivers/acpi/acpica/exstore.c > > > +++ b/drivers/acpi/acpica/exstore.c > > > @@ -95,8 +95,7 @@ acpi_ex_store(union acpi_operand_object *source_desc, > > > if (dest_desc->common.flags & AOPOBJ_AML_CONSTANT) { > > > return_ACPI_STATUS(AE_OK); > > > } > > > - > > > - /*lint -fallthrough */ > > > + fallthrough; > > > > > > default: > > > > > > @@ -421,8 +420,7 @@ acpi_ex_store_object_to_node(union > > > acpi_operand_object *source_desc, > > > } > > > break; > > > } > > > - > > > - /* Fallthrough */ > > > + fallthrough; > > > > > > case ACPI_TYPE_DEVICE: > > > case ACPI_TYPE_EVENT: > > > diff --git a/drivers/acpi/acpica/hwgpe.c > > > b/drivers/acpi/acpica/hwgpe.c index b13a4ed5bc63..fbfad80c8a53 > > > 100644 > > > --- a/drivers/acpi/acpica/hwgpe.c > > > +++ b/drivers/acpi/acpica/hwgpe.c > > > @@ -166,8 +166,7 @@ acpi_hw_low_set_gpe(struct acpi_gpe_event_info > > > *gpe_event_info, u32 action) > > > if (!(register_bit & gpe_register_info->enable_mask)) { > > > return (AE_BAD_PARAMETER); > > > } > > > - > > > - /*lint -fallthrough */ > > > + fallthrough; > > > > > > case ACPI_GPE_ENABLE: > > > > > > diff --git a/drivers/acpi/acpica/utdelete.c > > > b/drivers/acpi/acpica/utdelete.c index 4c0d4e434196..8076e7947585 > > > 100644 > > > --- a/drivers/acpi/acpica/utdelete.c > > > +++ b/drivers/acpi/acpica/utdelete.c > > > @@ -111,8 +111,7 @@ static void acpi_ut_delete_internal_obj(union > > > acpi_operand_object *object) > > > (void)acpi_ev_delete_gpe_block(object->device. > > > gpe_block); > > > } > > > - > > > - /*lint -fallthrough */ > > > + fallthrough; > > > > > > case ACPI_TYPE_PROCESSOR: > > > case ACPI_TYPE_THERMAL: > > > diff --git a/drivers/acpi/acpica/utprint.c > > > b/drivers/acpi/acpica/utprint.c index 681c11f4af4e..f7e43baf5ff2 > > > 100644 > > > --- a/drivers/acpi/acpica/utprint.c > > > +++ b/drivers/acpi/acpica/utprint.c > > > @@ -475,7 +475,7 @@ int vsnprintf(char *string, acpi_size size, const > > > char *format, va_list args) > > > case 'X': > > > > > > type |= ACPI_FORMAT_UPPER; > > > - /* FALLTHROUGH */ > > > + fallthrough; > > > > > > case 'x': > > > > > > -- > > > 2.29.2.222.g5d2a92d10f8-goog > > > > > > > > > -- > > Thanks, > > ~Nick Desaulniers > > > > -- > Thanks, > ~Nick Desaulniers -- Thanks, ~Nick Desaulniers
