On Thu, 2020-11-12 at 11:30 -0800, Nick Desaulniers wrote: > On Thu, Nov 12, 2020 at 7:13 AM Moore, Robert <robert.moore@xxxxxxxxx> wrote: > > -----Original Message----- > > From: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > > On Wed, Nov 11, 2020 at 7:15 AM Moore, Robert <robert.moore@xxxxxxxxx> 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. acpica is a special case as all the code is in a separate repository and converted via Lindent to resemble linux standard styles. Perhaps it'd easier to avoid modifying acpica and add something like: --- diff --git a/drivers/acpi/acpica/Makefile b/drivers/acpi/acpica/Makefile index 59700433a96e..469508a8d671 100644 --- a/drivers/acpi/acpica/Makefile +++ b/drivers/acpi/acpica/Makefile @@ -4,6 +4,7 @@ # ccflags-y := -Os -D_LINUX -DBUILDING_ACPICA +ccflags-y += -Wno-implicit-fallthrough ccflags-$(CONFIG_ACPI_DEBUG) += -DACPI_DEBUG_OUTPUT # use acpi.o to put all files here into acpi.o modparam namespace
