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 <j...@perches.com>
Sent: Monday, July 27, 2020 7:22 PM
To: Gustavo A. R. Silva <gust...@embeddedor.com>; Moore, Robert
<robert.mo...@intel.com>; Rafael J. Wysocki <raf...@kernel.org>; Gustavo A. R.
Silva <gustavo...@kernel.org>
Cc: Kaneda, Erik <erik.kan...@intel.com>; Wysocki, Rafael J
<rafael.j.wyso...@intel.com>; Len Brown <l...@kernel.org>; ACPI Devel Maling
List <linux-a...@vger.kernel.org>; open list:ACPI COMPONENT ARCHITECTURE
(ACPICA) <de...@acpica.org>; Linux Kernel Mailing List
<linux-kernel@vger.kernel.org>
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.
