[PATCH] selftests/harness: fix many "format string is empty" warnings

[John Hubbard <jhubbard@nvidia.com>]

In order to build with clang at all, in order to see these symptoms, one
must first apply Valentin Obst's build fix for LLVM [1]. Once that is
done, then when building with clang, via:

    make LLVM=1 -C tools/testing/selftests

...clang emits a "format string is empty" warning. (gcc also emits a
similar warning.)

Fix by passing NULL, instead of "", for the msg argument to
ksft_test_result_code(). This removes dozens of warnings and a few
errors (some tests have -Werror set).

[1] https://lore.kernel.org/all/20240329-selftests-libmk-llvm-rfc-v1-1-2f9ed7d1c49f@valentinobst.de/

Cc: Valentin Obst <kernel@valentinobst.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Bill Wendling <morbo@google.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 tools/testing/selftests/kselftest_harness.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/kselftest_harness.h b/tools/testing/selftests/kselftest_harness.h
index d98702b6955d..456b8694e678 100644
--- a/tools/testing/selftests/kselftest_harness.h
+++ b/tools/testing/selftests/kselftest_harness.h
@@ -1207,8 +1207,10 @@ void __run_test(struct __fixture_metadata *f,
 	else
 		diagnostic = "unknown";
 
-	ksft_test_result_code(t->exit_code, test_name,
-			      diagnostic ? "%s" : NULL, diagnostic);
+	if (diagnostic)
+		ksft_test_result_code(t->exit_code, test_name, "%s", diagnostic);
+	else
+		ksft_test_result_code(t->exit_code, test_name, NULL);
 	free(test_name);
 }
 

base-commit: 18daea77cca626f590fb140fc11e3a43c5d41354
prerequisite-patch-id: b901ece2a5b78503e2fb5480f20e304d36a0ea27
-- 
2.45.0