Re: [PATCH BlueZ] build: Use AC_USE_SYSTEM_EXTENSIONS for POSIX/C extensions

[Marcel Holtmann <marcel@holtmann.org>]

Hi Lucas,

> > On Thu, Aug 30, 2012 at 11:08 AM, Marcel Holtmann <marcel@holtmann.org> wrote:
> >> Hi Anderson,
> >>
> >>> Using this macro in configure.ac enables certain extensions that BlueZ
> >>> currently depends on. The macro is recommended instead of defining
> >>> _GNU_SOURCE on each C file.
> >>
> >> what is the advantage of this. I am actually fine with using _GNU_SOURCE
> >> in the C files. It is according to the man pages.
> >
> > The only advantage I see is that we don't have to worry about
> > reviewing these defines as the symbols get incorporated in newer
> > standards. For instance, this patch was brought up because O_CLOEXEC
> > does not exist on POSIX.1-2001, but was incorporated POSIX.1-2008, so
> > for newer systems _GNU_SOURCE is not necessary for it anymore, but for
> > some (still maintained) distros it is.
> >
> > Sometimes we remove code that used these extensions, and simply forget
> > the _GNU_SOURCE there as well.
> 
> And also forget to add it. Then 3 months later comes a patch to fix it
> by adding the definition.
> 
> Using the autofoo macro we stop the build-fix patches for things like this.
> 
> 
> That is: it removes code, it's more future-proof and it has no
> downsides. So, what's the point of not using it?

unless that autoconf thing breaks and we don't get what we want. Or we
are dealing with an outdated autoconf.

I am against this. I rather get build fixes and have them recorded in
git compared to hoping that this magically fixes everything.

> Some months ago I sent a patch to also remove a lot of dumb "#include
> config.h". It has the same reasoning behind it: remove code and be
> more future-proof. It was for connman, but if you are interested I can
> send it to bluez/ofono/etc too -
> http://permalink.gmane.org/gmane.linux.network.connman/7310

Same thing. I believe that boilerplate is better being explicit than
magically having it done.

Regards

Marcel