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From: Simon Wunderlich <sw@simonwunderlich.de>
Date: Tue, 13 Jun 2017 10:48:57 +0200
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In-Reply-To: <20170613082600.24910-3-philipp.psurek@gmail.com>
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 <20170613082600.24910-3-philipp.psurek@gmail.com>
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Subject: Re: [B.A.T.M.A.N.] [PATCH 2/2] batctl: suppress
 implicit-fallthrough compiler warning
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To: Philipp Psurek <philipp.psurek@gmail.com>
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On Tuesday, June 13, 2017 10:26:00 AM CEST Philipp Psurek wrote:
> GCC 7.1.0 complains about an intended fallthrough.
> =E2=80=9C__attribute__ ((fallthrough))=E2=80=9D in this part of code woul=
d suppress this
> warning. Because older GCC compiler don=E2=80=99t understand this stateme=
nt
> attribute and because there is already a comment in the source containing
> =E2=80=9Cfalls?[ \t-]*thr(ough|u)=E2=80=9D we can suppress the warning wi=
th the
> =E2=80=9C-Wimplicit-fallthrough=3D2=E2=80=9D warning option. Unintended f=
allthroughs without a
> comment will trigger this warning.
>=20
> Older GCC compiler don=E2=80=99t understand this warning option and exits=
 with
> error. There has to be a compiler recognition after that only GCC =3D>7.1=
=2E0
> receives this option.
>=20
> Signed-off-by: Philipp Psurek <philipp.psurek@gmail.com>
> ---
>  Makefile | 5 +++++
>  1 file changed, 5 insertions(+)
>=20
> diff --git a/Makefile b/Makefile
> index 6bebb7d..29b7e2f 100755
> --- a/Makefile
> +++ b/Makefile
> @@ -101,6 +101,11 @@ MKDIR ?=3D mkdir -p
>  COMPILE.c =3D $(Q_CC)$(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c
>  LINK.o =3D $(Q_LD)$(CC) $(CFLAGS) $(LDFLAGS) $(TARGET_ARCH)
>=20
> +# Check for GCC >=3D7
> +ifeq ($(shell $(CC) -x c++ --std=3Dc++17 -E -P - <<< __cplusplus),201703=
L)
> +       CFLAGS +=3D -Wimplicit-fallthrough=3D2
> +endif
> +

Hmm, I don't like this one too much, since it looks cryptic and we will hav=
e=20
to add up new versions, which I'd like to avoid.

Did you try to change the wording? I've googled a bit and it seems a commen=
t=20
containing the wording "fallthrough" will avoid it. Maybe we should just=20
change "fall through" to "fallthrough"?

Thanks,
      Simon

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