Re: [PATCH v2 2/4] configure: Enforce gnu99 C language standard

[Leif Lindholm <leif@nuviainc.com>]

On Tue, Apr 07, 2020 at 12:41:20 +0200, Daniel Kiper wrote:
> On Tue, Apr 07, 2020 at 11:38:16AM +0200, Javier Martinez Canillas wrote:
> > On 4/3/20 2:45 PM, Daniel Kiper wrote:
> > > Commit d5a32255d (misc: Make grub_strtol() "end" pointers have safer
> > > const qualifiers) introduced "restrict" keyword into some functions
> > > definitions. This keyword was introduced in C99 standard. However, some
> > > compilers by default may use C89 or something different. This behavior
> > > leads to the breakage during builds when c89 or gnu89 is in force. So,
> > > let's enforce gnu99 C language standard for all compilers. This way
> > > a bit random build issue will be fixed and the GRUB source will be
> > > build consistently regardless of type and version of the compiler.
> > >
> > > It was decided to use gnu99 C language standard because it fixes the
> > > issue mentioned above and also provides some useful extensions which are
> > > used here and there in the GRUB source. Potentially we can use gnu11 too.
> > > However, this may reduce pool of older compilers which can be used to
> > > build the GRUB. So, let's live with gnu99 until we do not discover that
> > > we strongly require a feature from newer C standard.
> > >
> > > Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
> > > ---
> > > v2 - suggestions/fixes:
> > >    - unconditionally enforce gnu99 C language standard
> > >      (suggested by Leif Lindholm).
> > > ---
> > >  configure.ac | 4 ++++
> > >  1 file changed, 4 insertions(+)
> > >
> > > diff --git a/configure.ac b/configure.ac
> > > index b2576b013..fc74ee800 100644
> > > --- a/configure.ac
> > > +++ b/configure.ac
> > > @@ -80,6 +80,10 @@ if test "x$TARGET_CFLAGS" = x; then
> > >    TARGET_CFLAGS=-Os
> > >  fi
> > >
> >
> > I would add a comment here explaining why gnu99 is enforced.
> 
> I am not convinced that we should repeat here what is said in the commit
> message...
> 
> > > +BUILD_CFLAGS="-std=gnu99 $BUILD_CFLAGS"
> > > +HOST_CFLAGS="-std=gnu99 $HOST_CFLAGS"
> > > +TARGET_CFLAGS="-std=gnu99 $TARGET_CFLAGS"
> > > +
> >
> > Do you want to allow distros to override the -std option or do you want to
> > always force to use gnu99? If the latter then I think instead it should be:
> >
> > BUILD_CFLAGS="$BUILD_CFLAGS -std=gnu99"
> > HOST_CFLAGS="$HOST_CFLAGS -std=gnu99"
> > TARGET_CFLAGS="$TARGET_CFLAGS -std=gnu99"
> 
> I want to allow everybody to override the defaults. In general I think
> that we should not impose any artificial limits. If user wants to shoot in
> his/her foot he/she should be allowed to do that... In most cases...

If we were to prevent builders from overriding, we would also prevent
them from overriding with a *higher* version. I think that would be
undesirable.

Whereas setting it by default and letting it be overridden means if it
breaks the build, it's because the builder has requested options no
longer supported by the codebase.

/
    Leif