Re: [RFC 0/2] Eliminate zero length arrays in DPDK

[Tyler Retzlaff <roretzla@linux.microsoft.com>]

On Wed, Feb 16, 2022 at 10:10:01AM +0000, Bruce Richardson wrote:
> On Wed, Feb 16, 2022 at 11:05:09AM +0100, Morten Brørup wrote:
> > > From: Bruce Richardson [mailto:bruce.richardson@intel.com]
> > > Sent: Wednesday, 16 February 2022 10.33
> > > 
> > > On Tue, Feb 15, 2022 at 03:00:56PM -0800, Stephen Hemminger wrote:
> > > > Yet another case of applying Linux kernel best practices
> > > > to DPDK. Flexible arrays are supported by Clang, GCC and
> > > > Microsoft compilers (part of C99).
> > > >
> > > Do we need to start explicitly stating that DPDK uses C99 features, and
> > > adding -std=c99 to our build flags? Are we also requiring that
> > > applications
> > > are compiled with c99 features to use this (I would hope that they are,
> > > but
> > > I'm not sure we can mandate it).
> > 
> > No to -std=c99. It's >= C99 for applications; we should not prevent them from using a newer C standard.
> 
> Yes. For build flags, I was referring only to having it in the cflags for the
> build of DPDK itself, not for apps. We definitely need to minimise the
> build flags we expose to apps.
> 
> > 
> > Adding a note about the C standard version to the DPDK requirements
> > documentation would be very nice. It only mentions a certain compiler
> > version required. But I think that documenting the detailed build and
> > runtime requirements (and why they are that way) is another task.
> > 
> Sure, we should do that. I am just wanting to be sure that if we specify a
> minimum of C99, we won't get complaints back from those with legacy
> codebasees which only support C89/C90. I am therefore wondering if we need
> to have our public headers C90-compliant?

this seems to be the real question. what "minimum" C standard should be
documented as required to consume dpdk. we can obviously use any standard
we wish to build/provide binaries. similarly we ought to document a
minimum C++ standard for consumption.

i would advocate for C99 however before setting that in stone it is fair
to ask if there are any consumers using < C99.

we may also want to consider that the minimum required may differ
depending on the platform/port. though most differences in public interface
i would hope could be trivially abstracted though.

ty