Re: [RFC PATCH 0/1] Specify C-standard requirement for DPDK builds

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

On Wed, Feb 22, 2023 at 10:53:44AM -0800, Tyler Retzlaff wrote:
> On Thu, Jan 12, 2023 at 11:35:55AM +0000, Bruce Richardson wrote:
> > Traditionally, DPDK has never specified a minimum C standard used either
> > in DPDK builds or for applications using DPDK. Following discussion
> > on-list about C standards, this RFC attempts to start the process of
> > codifying what our standards expectations are. No code changes are made
> > by this RFC, instead only the build parameters are changed to explicitly
> > specify:
> > 
> > * C99 standard is used to build DPDK itself. This is supported by all
> >   supported compiler versions of GCC and Clang.
> > * The headers are checked for compatibility with gcc89 standard, which
> >   was the default standard used by the oldest supported version of GCC.
> >   DPDK headers do not build with the official C89 standard, and, to the
> >   best of my knowledge, have never done so.
> 
> subject to the technical board meeting 2023/02/22 in relation to atomics
> and adoption of C11 starting in 23.11 does anything stop us from
> conditionally enabling/defaulting -std=C11 for all platforms immediately
> except for RHEL/CentOS 7?
> 
> so long as we don't actually start using C11 features we should be able
> to do this? or would we be worried that C11 feature use would creep in?
> 
> just curious.
> 
Actually, if we don't do anything, the versions of gcc (and clang AFAIK)
already default to C11 or later from GCC 5 onwards. If we were to specify a
version, I think it would have to be gnu11 as we may still be using some
GCC extensions. However, feel free to do up a patch for c11 if it works.
The change to the header checks probably don't need to be included, only a
change to the default options in the top-level meson.build file.

Incidentally, even though it is missing support for the c11 atomics, gcc
4.8.5 on RHEL 7 does have the -std=c11 flag that can be used, so adding
that shouldn't break anything.

/Bruce