Re: [PATCH v2] build: update DPDK to use C11 standard

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

On Mon, Jul 31, 2023 at 04:58:02PM +0100, Bruce Richardson wrote:
> As previously announced, DPDK 23.11 will require a C11 supporting
> compiler and will use the C11 standard in all builds.
> 
> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
> Acked-by: Morten Brørup <mb@smartsharesystems.com>
> 
> ---
> V2:
> * Resubmit now that 23.11-rc0 patch applied
> * Add _POSIX_C_SOURCE macro to eal_common_errno.c to get POSIX
>   definition of strerror_r() with c11 standard.
> ---
>  doc/guides/linux_gsg/sys_reqs.rst      |  3 ++-
>  doc/guides/rel_notes/deprecation.rst   | 18 ------------------
>  doc/guides/rel_notes/release_23_11.rst | 17 +++++++++++++++++
>  lib/eal/common/eal_common_errno.c      |  1 +
>  meson.build                            |  1 +
>  5 files changed, 21 insertions(+), 19 deletions(-)
> 
> diff --git a/doc/guides/linux_gsg/sys_reqs.rst b/doc/guides/linux_gsg/sys_reqs.rst
> index dfeaf4e1c5..13be715933 100644
> --- a/doc/guides/linux_gsg/sys_reqs.rst
> +++ b/doc/guides/linux_gsg/sys_reqs.rst
> @@ -27,7 +27,8 @@ Compilation of the DPDK
>      The setup commands and installed packages needed on various systems may be different.
>      For details on Linux distributions and the versions tested, please consult the DPDK Release Notes.
>  
> -*   General development tools including a supported C compiler such as gcc (version 4.9+) or clang (version 3.4+),
> +*   General development tools including a C compiler supporting the C11 standard,
> +    including standard atomics, for example: GCC (version 5.0+) or Clang (version 3.6+),
>      and ``pkg-config`` or ``pkgconf`` to be used when building end-user binaries against DPDK.
>  
>      * For RHEL/Fedora systems these can be installed using ``dnf groupinstall "Development Tools"``
> diff --git a/doc/guides/rel_notes/deprecation.rst b/doc/guides/rel_notes/deprecation.rst
> index 494b401cda..cc939d3c67 100644
> --- a/doc/guides/rel_notes/deprecation.rst
> +++ b/doc/guides/rel_notes/deprecation.rst
> @@ -17,24 +17,6 @@ Other API and ABI deprecation notices are to be posted below.
>  Deprecation Notices
>  -------------------
>  
> -* C Compiler: From DPDK 23.11 onwards,
> -  building DPDK will require a C compiler which supports the C11 standard,
> -  including support for C11 standard atomics.
> -
> -  More specifically, the requirements will be:
> -
> -  * Support for flag "-std=c11" (or similar)
> -  * __STDC_NO_ATOMICS__ is *not defined* when using c11 flag
> -
> -  Please note:
> -
> -  * C11, including standard atomics, is supported from GCC version 5 onwards,
> -    and is the default language version in that release
> -    (Ref: https://gcc.gnu.org/gcc-5/changes.html)
> -  * C11 is the default compilation mode in Clang from version 3.6,
> -    which also added support for standard atomics
> -    (Ref: https://releases.llvm.org/3.6.0/tools/clang/docs/ReleaseNotes.html)
> -
>  * build: Enabling deprecated libraries (``flow_classify``, ``kni``)
>    won't be possible anymore through the use of the ``disable_libs`` build option.
>    A new build option for deprecated libraries will be introduced instead.
> diff --git a/doc/guides/rel_notes/release_23_11.rst b/doc/guides/rel_notes/release_23_11.rst
> index 6b4dd21fd0..c8b9ed456c 100644
> --- a/doc/guides/rel_notes/release_23_11.rst
> +++ b/doc/guides/rel_notes/release_23_11.rst
> @@ -20,6 +20,23 @@ DPDK Release 23.11
>        ninja -C build doc
>        xdg-open build/doc/guides/html/rel_notes/release_23_11.html
>  
> +* Build Requirements: From DPDK 23.11 onwards,
> +  building DPDK will require a C compiler which supports the C11 standard,
> +  including support for C11 standard atomics.
> +
> +  More specifically, the requirements will be:
> +
> +  * Support for flag "-std=c11" (or similar)
> +  * __STDC_NO_ATOMICS__ is *not defined* when using c11 flag
> +
> +  Please note:
> +
> +  * C11, including standard atomics, is supported from GCC version 5 onwards,
> +    and is the default language version in that release
> +    (Ref: https://gcc.gnu.org/gcc-5/changes.html)
> +  * C11 is the default compilation mode in Clang from version 3.6,
> +    which also added support for standard atomics
> +    (Ref: https://releases.llvm.org/3.6.0/tools/clang/docs/ReleaseNotes.html)
>  
>  New Features
>  ------------
> diff --git a/lib/eal/common/eal_common_errno.c b/lib/eal/common/eal_common_errno.c
> index ef8f782abb..b30e2f0ad4 100644
> --- a/lib/eal/common/eal_common_errno.c
> +++ b/lib/eal/common/eal_common_errno.c
> @@ -4,6 +4,7 @@
>  
>  /* Use XSI-compliant portable version of strerror_r() */
>  #undef _GNU_SOURCE
> +#define _POSIX_C_SOURCE 200809L
>  
>  #include <stdio.h>
>  #include <string.h>
> diff --git a/meson.build b/meson.build
> index 39cb73846d..70b54f0c98 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -9,6 +9,7 @@ project('DPDK', 'c',
>          license: 'BSD',
>          default_options: [
>              'buildtype=release',
> +            'c_std=c11',
>              'default_library=static',
>              'warning_level=2',
>          ],
> -- 

oh I acked v2 (and you can maintain that ack) but one additional removal
of forced -std=gnu99 is maybe necessary?

drivers/net/failsafe/meson.build
    probably should remove cflags += '-std=gnu99'

if we remove it we inherit the -std=c11 from meson project configuration
and define a _POSIX_C_SOURCE narrowly where necessary (if it is needed).