[PATCH v2 1/5] selftests: Compile kselftest headers with -D_GNU_SOURCE

[Edward Liaw <edliaw@xxxxxxxxxx>]

Add the -D_GNU_SOURCE flag to KHDR_INCLUDES so that it is defined in a
central location.

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.

Fixes: 809216233555 ("selftests/harness: remove use of LINE_MAX")
Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-lkp/202404301040.3bea5782-oliver.sang@xxxxxxxxx
Signed-off-by: Edward Liaw <edliaw@xxxxxxxxxx>
---
 tools/testing/selftests/Makefile            | 4 ++--
 tools/testing/selftests/kselftest_harness.h | 2 +-
 tools/testing/selftests/lib.mk              | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index e1504833654d..ed012a7f0786 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -161,11 +161,11 @@ ifneq ($(KBUILD_OUTPUT),)
   # $(realpath ...) resolves symlinks
   abs_objtree := $(realpath $(abs_objtree))
   BUILD := $(abs_objtree)/kselftest
-  KHDR_INCLUDES := -isystem ${abs_objtree}/usr/include
+  KHDR_INCLUDES := -D_GNU_SOURCE -isystem ${abs_objtree}/usr/include
 else
   BUILD := $(CURDIR)
   abs_srctree := $(shell cd $(top_srcdir) && pwd)
-  KHDR_INCLUDES := -isystem ${abs_srctree}/usr/include
+  KHDR_INCLUDES := -D_GNU_SOURCE -isystem ${abs_srctree}/usr/include
   DEFAULT_INSTALL_HDR_PATH := 1
 endif
 
diff --git a/tools/testing/selftests/kselftest_harness.h b/tools/testing/selftests/kselftest_harness.h
index d98702b6955d..b2a1b6343896 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, "kselftest harness requires _GNU_SOURCE to be defined");
 #endif
 #include <asm/types.h>
 #include <ctype.h>
diff --git a/tools/testing/selftests/lib.mk b/tools/testing/selftests/lib.mk
index da2cade3bab0..2503dc732b4d 100644
--- a/tools/testing/selftests/lib.mk
+++ b/tools/testing/selftests/lib.mk
@@ -45,7 +45,7 @@ selfdir = $(realpath $(dir $(filter %/lib.mk,$(MAKEFILE_LIST))))
 top_srcdir = $(selfdir)/../../..
 
 ifeq ($(KHDR_INCLUDES),)
-KHDR_INCLUDES := -isystem $(top_srcdir)/usr/include
+KHDR_INCLUDES := -D_GNU_SOURCE -isystem $(top_srcdir)/usr/include
 endif
 
 # The following are built by lib.mk common compile rules.
-- 
2.45.0.rc1.225.g2a3ae87e7f-goog