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Re: [PATCH 05/14] isdn: isdnloop: suppress a gcc-7 warning

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On Fri, Jul 14, 2017 at 12:37:05PM +0200, Arnd Bergmann wrote:
> On Fri, Jul 14, 2017 at 12:08 PM, Joe Perches <joe@perches.com> wrote:
> > On Fri, 2017-07-14 at 11:25 +0200, Arnd Bergmann wrote:
> >> We test whether a bit is set in a mask here, which is correct
> >> but gcc warns about it as it thinks it might be confusing:
> >>
> >> drivers/isdn/isdnloop/isdnloop.c:412:37: error: ?: using integer constants in boolean context, the expression will always evaluate to 'true' [-Werror=int-in-bool-context]

...

> > Perhaps this is a logic defect and should be:
> >
> >                 if (!(card->flags & ((channel) ? ISDNLOOP_FLAGS_B2ACTIVE : ISDNLOOP_FLAGS_B1ACTIVE)))
> 
> Yes, good catch. I had thought about it for a bit whether that would be
> the answer, but come to the wrong conclusion on my own.
> 
> Note that the version you suggested will still have the warning, so I think
> it needs to be

It shouldn't - the warning is for using an integer *constant* in boolean
context, but the result of & isn't a constant and should be fine.

!(flags & mask) is a very common idiom.

    - Kevin 

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[PATCH 00/14] gcc-7 warnings Arnd Bergmann <arnd@arndb.de> - 2017-07-14 11:30 +0200
  [PATCH 05/14] isdn: isdnloop: suppress a gcc-7 warning Arnd Bergmann <arnd@arndb.de> - 2017-07-14 11:30 +0200
    Re: [PATCH 05/14] isdn: isdnloop: suppress a gcc-7 warning Joe Perches <joe@perches.com> - 2017-07-14 12:10 +0200
      Re: [PATCH 05/14] isdn: isdnloop: suppress a gcc-7 warning Arnd Bergmann <arnd@arndb.de> - 2017-07-14 12:40 +0200
        Re: [PATCH 05/14] isdn: isdnloop: suppress a gcc-7 warning Kevin Easton <kevin@guarana.org> - 2017-07-15 06:30 +0200
  [PATCH 04/14] x86: math-emu: avoid -Wint-in-bool-context warning Arnd Bergmann <arnd@arndb.de> - 2017-07-14 11:30 +0200
  [PATCH 07/14] proc/kcore: hide a harmless warning Arnd Bergmann <arnd@arndb.de> - 2017-07-14 11:30 +0200
    Re: [PATCH 07/14] proc/kcore: hide a harmless warning Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2017-07-14 14:30 +0200
  [PATCH 13/14] iopoll: avoid -Wint-in-bool-context warning Arnd Bergmann <arnd@arndb.de> - 2017-07-14 11:40 +0200
    Re: [PATCH 13/14] iopoll: avoid -Wint-in-bool-context warning Joe Perches <joe@perches.com> - 2017-07-14 12:00 +0200
      Re: [PATCH 13/14] iopoll: avoid -Wint-in-bool-context warning Arnd Bergmann <arnd@arndb.de> - 2017-07-14 12:30 +0200
  [PATCH 09/14] SFI: fix tautological-compare warning Arnd Bergmann <arnd@arndb.de> - 2017-07-14 11:40 +0200
  [PATCH 11/14] IB/uverbs: fix gcc-7 type warning Arnd Bergmann <arnd@arndb.de> - 2017-07-14 11:40 +0200
    Re: [PATCH 11/14] IB/uverbs: fix gcc-7 type warning Leon Romanovsky <leon@kernel.org> - 2017-07-14 11:50 +0200
  [PATCH 10/14] staging:iio:resolver:ad2s1210 fix negative IIO_ANGL_VEL read Arnd Bergmann <arnd@arndb.de> - 2017-07-14 11:40 +0200
    Re: [PATCH 10/14] staging:iio:resolver:ad2s1210 fix negative  IIO_ANGL_VEL read Jonathan Cameron <jic23@kernel.org> - 2017-07-15 13:50 +0200
  [PATCH 12/14] drm/nouveau/clk: fix gcc-7 -Wint-in-bool-context warning Arnd Bergmann <arnd@arndb.de> - 2017-07-14 11:40 +0200
  [PATCH 06/14] acpi: thermal: fix gcc-6/ccache warning Arnd Bergmann <arnd@arndb.de> - 2017-07-14 11:40 +0200
  [PATCH 08/14] Input: adxl34x - fix gcc-7 -Wint-in-bool-context warning Arnd Bergmann <arnd@arndb.de> - 2017-07-14 11:40 +0200
    Re: [PATCH 08/14] Input: adxl34x - fix gcc-7 -Wint-in-bool-context warning Linus Torvalds <torvalds@linux-foundation.org> - 2017-07-14 21:30 +0200
      Re: [PATCH 08/14] Input: adxl34x - fix gcc-7 -Wint-in-bool-context warning Arnd Bergmann <arnd@arndb.de> - 2017-07-14 22:20 +0200
        Re: [PATCH 08/14] Input: adxl34x - fix gcc-7 -Wint-in-bool-context  warning Dmitry Torokhov <dmitry.torokhov@gmail.com> - 2017-07-14 23:50 +0200
  [PATCH 14/14] [media] fix warning on v4l2_subdev_call() result interpreted as bool Arnd Bergmann <arnd@arndb.de> - 2017-07-14 11:50 +0200
    Re: [PATCH 14/14] [media] fix warning on v4l2_subdev_call() result  interpreted as bool Dan Carpenter <dan.carpenter@oracle.com> - 2017-07-14 14:10 +0200
      Re: [PATCH 14/14] [media] fix warning on v4l2_subdev_call() result  interpreted as bool Arnd Bergmann <arnd@arndb.de> - 2017-07-14 14:30 +0200
        Re: [PATCH 14/14] [media] fix warning on v4l2_subdev_call() result  interpreted as bool Dan Carpenter <dan.carpenter@oracle.com> - 2017-07-14 15:00 +0200
          Re: [PATCH 14/14] [media] fix warning on v4l2_subdev_call() result  interpreted as bool Dan Carpenter <dan.carpenter@oracle.com> - 2017-07-14 15:20 +0200
            Re: [PATCH 14/14] [media] fix warning on v4l2_subdev_call() result  interpreted as bool Arnd Bergmann <arnd@arndb.de> - 2017-07-14 21:40 +0200
    Re: [PATCH 14/14] [media] fix warning on v4l2_subdev_call() result  interpreted as bool Dan Carpenter <dan.carpenter@oracle.com> - 2017-07-14 14:50 +0200
    Re: [PATCH 14/14] [media] fix warning on v4l2_subdev_call() result  interpreted as bool Hans Verkuil <hverkuil@xs4all.nl> - 2017-07-17 15:50 +0200
      Re: [PATCH 14/14] [media] fix warning on v4l2_subdev_call() result  interpreted as bool Arnd Bergmann <arnd@arndb.de> - 2017-07-17 16:30 +0200
        Re: [PATCH 14/14] [media] fix warning on v4l2_subdev_call() result  interpreted as bool Hans Verkuil <hverkuil@xs4all.nl> - 2017-07-17 16:40 +0200
          Re: [PATCH 14/14] [media] fix warning on v4l2_subdev_call() result  interpreted as bool Arnd Bergmann <arnd@arndb.de> - 2017-07-17 23:30 +0200
        Re: [PATCH 14/14] [media] fix warning on v4l2_subdev_call() result  interpreted as bool Dan Carpenter <dan.carpenter@oracle.com> - 2017-07-17 16:40 +0200
        Re: [PATCH 14/14] [media] fix warning on v4l2_subdev_call() result  interpreted as bool Hans Verkuil <hverkuil@xs4all.nl> - 2017-07-17 16:40 +0200
  Re: [PATCH 00/14] gcc-7 warnings Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-14 12:30 +0200

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