On 12/15/2021 11:15 PM, Stephen Hemminger wrote:
On Wed, 15 Dec 2021 21:04:30 +0000
Ferruh Yigit <ferruh.yi...@intel.com> wrote:
On 12/15/2021 7:20 PM, Stephen Hemminger wrote:
On Wed, 15 Dec 2021 18:48:59 +0000
Ferruh Yigit <ferruh.yi...@intel.com> wrote:
Linux is using '-Wimplicit-fallthrough=5' compiler option, which doesn't
take any fall through comments into account but only uses compiler
'fallthrough' attribute to document fall through action is intended.
"falls through" comment was used in the code which is causing a build
error now, this patch converts comment to the 'fallthrough' macro
defined in the Linux.
To cover the case where Linux version doesn't have the macro, defined it
in the compatibility header too.
Signed-off-by: Ferruh Yigit <ferruh.yi...@intel.com>
Are you sure that fixes it? because the comment in the macro is typically
not visible in a macro expansion.
Since in most case Linux uses gcc why not use the gcc attribute
__attribute__ ((fallthrough))
Hi Stephen,
That is the intention already.
Patch is using the Linux kernel defined macro:
#if __has_attribute(__fallthrough__)
# define fallthrough __attribute__((__fallthrough__))
#else
# define fallthrough do {} while (0) /* fallthrough */
#endif
And it builds fine without the macro in the 'compat.h'.
I added the define in the 'compat.h' for old kernels which doesn't
define the macro. For that case I expect default '-Wimplicit-fallthrough'
option is used which accepts 'fallthrough;' as a regex hit.
Your right, on older kernels it really is just a dummy statement.
The regex can't work, you can take (or leave the comment) it has no effect
because implicit-fallthrough won't see it in a macro.
True, it has no benefit for 'Wimplicit-fallthrough', and regex doesn't hit.
But for the old kernels (<= 5.3) still need to have this define to prevent
build error, because they are missing 'fallthrough' macro.
But for those kernels, '-Wimplicit-fallthrough' compiler option is not
set, so that should be OK **.
I have tested with '4.19.221' stable kernel, this change builds fine.
**: Only v5.3 has potential problem, which defines '-Wimplicit-fallthrough' and
doesn't define the 'fallthrough' macro. When igb_uio compiled with this version
'fallthrough' is dummy statement from 'compat.h' and '-Wimplicit-fallthrough'
can cause warning.
To fix this, I will move both dummy and attribute macro definition to compat.h
