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Date: Tue, 23 Jul 2019 14:18:34 +0100
From: Bruce Richardson <bruce.richardson@intel.com>
To: Krzysztof Kanas <kkanas@marvell.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>, Thomas Monjalon <thomas@monjalon.net>,
"reshma.pattan@intel.com" <reshma.pattan@intel.com>
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Subject: Re: [dpdk-dev] [EXT] Re: [PATCH] mk: disable flag for no packet
member warning
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On Tue, Jul 23, 2019 at 09:05:50AM +0000, Krzysztof Kanas wrote:
> On 19-07-22 14:44, Bruce Richardson wrote:
> > External Email
> >
> > ----------------------------------------------------------------------
> > On Mon, Jul 22, 2019 at 02:39:59PM +0200, kkanas@marvell.com wrote:
> > > From: Krzysztof Kanas <kkanas@marvell.com>
> > >
> > > gcc prior 9 don't will add additional warning for unrecognized command
> > > line option, but only when there is some other warning in the code, e.g
> > > unused variable.
> > >
> > I don't think this behaviour has changed in gcc 9. I just did a test
> > compile with gcc 9.1, and no warning was printed for flag
> > "-Wno-random-warnings". The online docs also make no mention of this
> > behaviour being conditional on GCC version [1].
> GCC changelog show that from 9.0 -Waddress-of-packed-member was added
> [1].
>
> Test shows me that GCC prior to 9.0 won't complain about this flag, but
> in case of other warnings in file GCC will complain, e.g.,
>
> cat > a.c
> int main(int argc, char **argv)
> {
> int a;
> return 0;
> }
>
> # gcc -Wall -Wno-address-of-packed-member a.c
>
> a.c: In function ‘main’:
> a.c:3:6: warning: unused variable ‘a’ [-Wunused-variable]
> int a;
> ^
> a.c: At top level:
> cc1: warning: unrecognized command line option ‘-Wno-address-of-packed-member’
>
> But when line `int a;' is removed then no warning is issued.
>
> Also I detected this, due to difference with meson build. Meson checks
> if compiler supports this flag and will not issue
> -Wno-address-of-packed-member to compiler.
>
Yes, all that is correct, but there is no behaviour change in GCC 9. This
does not require a fix IMHO.
/Bruce