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Date: Thu, 2 May 2024 15:41:00 -0700
From: Kees Cook <keescook@chromium.org>
To: Sean Christopherson <seanjc@google.com>
Cc: Mark Brown <broonie@kernel.org>, Edward Liaw <edliaw@google.com>,
	shuah@kernel.org, Jaroslav Kysela <perex@perex.cz>,
	Takashi Iwai <tiwai@suse.com>, Jiri Kosina <jikos@kernel.org>,
	Benjamin Tissoires <bentiss@kernel.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Bongsu Jeon <bongsu.jeon@samsung.com>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
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	Jarkko Sakkinen <jarkko@kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Muhammad Usama Anjum <usama.anjum@collabora.com>,
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Subject: Re: [PATCH v1 00/10] Define _GNU_SOURCE for sources using
Message-ID: <202405021540.3FF73DF47@keescook>
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 <ZjJClMYEIyGEo37e@google.com>
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On Wed, May 01, 2024 at 06:24:36AM -0700, Sean Christopherson wrote:
> On Wed, May 01, 2024, Mark Brown wrote:
> > On Tue, Apr 30, 2024 at 11:50:09PM +0000, Edward Liaw wrote:
> > > 809216233555 ("selftests/harness: remove use of LINE_MAX") introduced
> > > asprintf into kselftest_harness.h, which is a GNU extension and needs
> > > _GNU_SOURCE to either be defined prior to including headers or with the
> > > -D_GNU_SOURCE flag passed to the compiler.
> > 
> > This seems like something that should be handled centrally rather than
> > having to go round and audit the users every time some update is made.
> 
> +1.
> 
> And if for some reason unilaterally defining _GNU_SOURCE in
> tools/testing/selftests/lib.mk isn't an option, we should at least have
> kselftest_harness.h assert instead of making a futile attempt to provide its own
> definition, e.g.
> 
> diff --git a/tools/testing/selftests/kselftest_harness.h b/tools/testing/selftests/kselftest_harness.h
> index 4fd735e48ee7..6741b4f20f25 100644
> --- a/tools/testing/selftests/kselftest_harness.h
> +++ b/tools/testing/selftests/kselftest_harness.h
> @@ -51,7 +51,7 @@
>  #define __KSELFTEST_HARNESS_H
>  
>  #ifndef _GNU_SOURCE
> -#define _GNU_SOURCE
> +static_assert(0, "Using the kselftests harness requires building with _GNU_SOURCE");
>  #endif
>  #include <asm/types.h>
>  #include <ctype.h>

Yeah, let's fix centrally. I like this approach.

-- 
Kees Cook