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

[Krzysztof Kanas <kkanas@marvell.com>]

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.

> 
> /Bruce
> 
> [1] https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html

[1] https://gcc.gnu.org/gcc-9/changes.html


-- 
-
Regards,
Krzysztof(Chris) Kanas