I'm afraid that the macro does not compile under MSVC: warning C4067: unexpected tokens following preprocessor directive - expected a newline (compiling source file ..\..\source\tools\acpiexec\aetests.c)
It looks like "__has_attribute" is not supported. -----Original Message----- From: Joe Perches <[email protected]> Sent: Monday, July 27, 2020 7:22 PM To: Gustavo A. R. Silva <[email protected]>; Moore, Robert <[email protected]>; Rafael J. Wysocki <[email protected]>; Gustavo A. R. Silva <[email protected]> Cc: Kaneda, Erik <[email protected]>; Wysocki, Rafael J <[email protected]>; Len Brown <[email protected]>; ACPI Devel Maling List <[email protected]>; open list:ACPI COMPONENT ARCHITECTURE (ACPICA) <[email protected]>; Linux Kernel Mailing List <[email protected]> Subject: Re: [PATCH][next] ACPICA: Use fallthrough pseudo-keyword On Mon, 2020-07-27 at 17:23 -0500, Gustavo A. R. Silva wrote: > Hi, > > > This is a macro pseudo-keyword, which expands to /* fallthrough */ for > compilers that don't support the attribute __fallthrough__. See: Not really. It expands to do {} while (0) for compilers that do not support the __fallthrough__ attribute. The /* fallthrough */ after that is for the human reader and is stripped before compilation. > include/linux/compiler_attributes.h:213: > 213 #if __has_attribute(__fallthrough__) > 214 # define fallthrough __attribute__((__fallthrough__)) > 215 #else > 216 # define fallthrough do {} while (0) /* fallthrough */ > 217 #endif > > So, any compiler (older or new) will be fine with it. But old compilers should not emit warnings for these uses.
