Subject: Re: [PATCH v1 00/10] Define _GNU_SOURCE for sources using

From: Sean Christopherson <[email-masked]>
Date: Wed, 1 May 2024 06:24:36 -0700

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>