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

["Morten Brørup" <mb@smartsharesystems.com>]

> From: Tyler Retzlaff [mailto:roretzla@linux.microsoft.com]
> Sent: Thursday, 17 February 2022 08.42
> 
> 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

Just read that the Linux kernel is moving towards C11, or at minimum C99, for version 5.18:
https://lwn.net/SubscriberLink/885941/01fdc39df2ecc25f/

Let's be bold and push for the same for DPDK! :-)

-Morten