Re: [dpdk-dev] [PATCH 01/10] mk: adjust gcc flags for new gcc 7 warnings

[Thomas Monjalon <thomas@monjalon.net>]

In this series, there are some fixes for fall-through comments,
missing break and missing initializers.
I think there is no discussion about accepting them in 17.05.
The last item to discuss it the new snprintf warning:

05/05/2017 11:42, Bruce Richardson:
> On Thu, May 04, 2017 at 09:38:08AM -0700, Stephen Hemminger wrote:
> > On Thu,  4 May 2017 16:38:13 +0100
> > Bruce Richardson <bruce.richardson@intel.com> wrote:
> > > 2. GCC also warns about an snprintf where there may be truncation and the
> > > return value is not checked. Given that we often use snprintf in DPDK in
> > > place of strncpy, and in many cases where truncation is not a problem, we
> > > can just disable this particular warning.
[...]
> > > --- a/mk/toolchain/gcc/rte.vars.mk
> > > +++ b/mk/toolchain/gcc/rte.vars.mk
> > > +# Ignore errors for snprintf truncation
> > > +WERROR_FLAGS += -Wno-format-truncation
[...]
> 2. for the format truncation warning, ideally, yes we should fix the
> code, except that I don't believe this is feasible in the short term,
> and I also don't believe it is desirable. We extensively use snprintf
> because it has sane/safe truncation, and in many cases we don't care if
> it is being truncated. Therefore disabling the warning seems the best
> approach to me. Furthermore, if we want 17.05 to compile with GCC 7,
> this is the best option within that timeframe.

We could imagine an explicit ignore of the return code.
However, do we really want this new coding rule for every snprintf?
It is a common call in DPDK:
	git grep '\<snprintf\>' | wc -l
	774
And probably almost never checked:
	git grep '^[[:space:]]*\<snprintf\>' | wc -l
	660

I suggest to disable this new warning in GCC 7.
Any opinions?