Re: [dpdk-dev] [EXT] Re: [PATCH] mk: disable flag for no packet member warning

[Bruce Richardson <bruce.richardson@intel.com>]

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