On 06/12/2017 11:54 PM, Sami Kerola wrote:
On 12 June 2017 at 09:40, Rüdiger Meier <sweet_f_a@xxxxxx> wrote:
On 06/11/2017 10:36 AM, Sami Kerola wrote:
On 9 June 2017 at 22:10, Rüdiger Meier <sweet_f_a@xxxxxx> wrote:
Sorry this was broken. But I've checked now all clang and gcc versions.
Looks
like for clang the warning is only enabled when using C++ (clang++). So
the
fallthrough warning appears currently only on gcc>=7 and this works to
disable
it in a compatible way:
#ifndef __has_cpp_attribute
# define __has_cpp_attribute(x) 0
#endif
#if __has_cpp_attribute(fallthrough)
# define UL_FALLTHROUGH __attribute__((fallthrough))
#else
# define UL_FALLTHROUGH /* fall through */
#endif
Thank you for review Rudi. I had a look of the c.h again and did the
change a little bit differently:
#ifdef __has_cpp_attribute
# if __has_cpp_attribute(deprecated)
Is this a typoo? s/deprecated/fallthrough
Hi Rudi,
Yes, it was a typo. Fixed in following.
https://github.com/kerolasa/lelux-utiliteetit/commit/aa1ed6ac309a2bd6f0c5371a3117618074e7634a
# define UL_FALLTHROUGH __attribute__((fallthrough))
# elif __has_cpp_attribute(clang::fallthrough)
# define UL_FALLTHROUGH [[clang::fallthrough]]
I still wonder. Have you really seen such a fallthrough warning from clang?
I've even tried with explicit -Wimplicit-fallthrough but could not get one.
As far as I understood these namespaced "clang::" attributes are for C++
only.
man clang:
Non-standard C++11 Attributes
Clang's non-standard C++11 attributes live in the clang attribute
namespace
So IMO it makes no sense to use clang::fallthrough for C code.
Removed in same commit. Strange enough I'm pretty sure that attribute
worked.
Yes, clang does not seem to complain about clang++ attributes. I guess they
don't want to introduce even more incompatibilities. Similar I've noticed
that even old gcc and clang compilers accept (ignore) the option
-Wimplicit-fallthrough" and probably any other warning option.
FYI I've set up a travis build script to test many gcc and clang versions.
The current build logs contain your and my other pull request
https://travis-ci.org/rudimeier/util-linux/builds/242109953
# endif
#endif
#ifndef UL_FALLTHROUGH
# define UL_FALLTHROUGH /* FALLTHRU */
#endif
BTW just for cosmetics. Maybe we should rename UL_FALLTHROUGH to
__ul_fallthrough
like we have already __ul_calloc_size. IMO it would look more obvious to the
reader.
I don't have strong opinion about that, changed to one you proposed.
Thanks, let's see whether Karel likes this attribute at all ;)
Also I would use it without semicolon because some compilers may complain
about
useless ";" statements.
Semicolon is removed. Whether this will fool various indent tools is something
to be seen.
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