linux-kernel - Re: [PATCH v2 03/34] compiler-capability-analysis: Add test stub

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Message-ID: <CANpmjNMYoRTj3F1L9UCp2gHVbVZw0ieNnk0xPZ8Q--BhFCy7Ww@mail.gmail.com>
Date: Wed, 5 Mar 2025 01:03:51 +0100
From: Marco Elver <elver@...gle.com>
To: Bart Van Assche <bvanassche@....org>
Cc: "David S. Miller" <davem@...emloft.net>, Luc Van Oostenryck <luc.vanoostenryck@...il.com>, 
	"Paul E. McKenney" <paulmck@...nel.org>, Alexander Potapenko <glider@...gle.com>, Arnd Bergmann <arnd@...db.de>, 
	Bill Wendling <morbo@...gle.com>, Boqun Feng <boqun.feng@...il.com>, 
	Dmitry Vyukov <dvyukov@...gle.com>, Eric Dumazet <edumazet@...gle.com>, 
	Frederic Weisbecker <frederic@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Herbert Xu <herbert@...dor.apana.org.au>, Ingo Molnar <mingo@...nel.org>, 
	Jann Horn <jannh@...gle.com>, Jiri Slaby <jirislaby@...nel.org>, 
	Joel Fernandes <joel@...lfernandes.org>, Jonathan Corbet <corbet@....net>, 
	Josh Triplett <josh@...htriplett.org>, Justin Stitt <justinstitt@...gle.com>, 
	Kees Cook <kees@...nel.org>, Kentaro Takeda <takedakn@...data.co.jp>, 
	Mark Rutland <mark.rutland@....com>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, 
	Miguel Ojeda <ojeda@...nel.org>, Nathan Chancellor <nathan@...nel.org>, 
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
	Steven Rostedt <rostedt@...dmis.org>, Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>, 
	Thomas Gleixner <tglx@...utronix.de>, Uladzislau Rezki <urezki@...il.com>, Waiman Long <longman@...hat.com>, 
	Will Deacon <will@...nel.org>, kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org, 
	llvm@...ts.linux.dev, rcu@...r.kernel.org, linux-crypto@...r.kernel.org, 
	linux-serial@...r.kernel.org
Subject: Re: [PATCH v2 03/34] compiler-capability-analysis: Add test stub

On Wed, 5 Mar 2025 at 00:52, Bart Van Assche <bvanassche@....org> wrote:
>
> On 3/4/25 1:21 AM, Marco Elver wrote:
> > +#include <linux/build_bug.h>
> > +
> > +/*
> > + * Test that helper macros work as expected.
> > + */
> > +static void __used test_common_helpers(void)
> > +{
> > +     BUILD_BUG_ON(capability_unsafe(3) != 3); /* plain expression */
> > +     BUILD_BUG_ON(capability_unsafe((void)2; 3;) != 3); /* does not swallow semi-colon */
> > +     BUILD_BUG_ON(capability_unsafe((void)2, 3) != 3); /* does not swallow commas */
> > +     capability_unsafe(do { } while (0)); /* works with void statements */
> > +}
>
> Is it guaranteed that <linux/build_bug.h> includes the header file that
> defines capability_unsafe() or should that header file perhaps be
> included explicitly?

It doesn't come in via build_bug.h, but via:

  scripts/Makefile.lib -> "-include
$(srctree)/include/linux/compiler_types.h" (all TUs) ->
compiler-capability-analysis.h.

The things pulled in via compiler_types.h are treated a bit like
builtins available everywhere implicitly.