[PATCH v6 1/8] selftests: Add printf attribute to kselftest prints

[Maciej Wieczor-Retman]

Kselftest header defines multiple variadic functions that use printf
along with other logic.

There is no format checking for the variadic functions that use
printing inside kselftest.h. Because of this the compiler won't
be able to catch instances of mismatched printf formats and debugging
tests might be more difficult.

Add the common __printf() attribute macro to kselftest.h.

Add __printf() attribute to every function using formatted printing
with variadic arguments.

Adding the attribute and compiling all selftests exposes a number of
-Wformat warnings which were previously unnoticed due to a lack of
format specifiers checking by the compiler.

Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@xxxxxxxxx>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
Reviewed-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
---
Changelog v6:
- Add a paragraph at the end of the patch message explaining the
  methodology and consequences for the rest of the series. (Shuah)

Changelog v4:
- Fix typo in patch subject. (Reinette)
- Add Reinette's reviewed-by tag.

 tools/testing/selftests/kselftest.h | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/kselftest.h b/tools/testing/selftests/kselftest.h
index af9f1202d423..5696199c16f9 100644
--- a/tools/testing/selftests/kselftest.h
+++ b/tools/testing/selftests/kselftest.h
@@ -78,6 +78,8 @@
 #define KSFT_XPASS 3
 #define KSFT_SKIP  4
 
+#define __printf(a, b)   __attribute__((format(printf, a, b)))
+
 /* counters */
 struct ksft_count {
 	unsigned int ksft_pass;
@@ -144,7 +146,7 @@ static inline void ksft_print_cnts(void)
 		ksft_cnt.ksft_xskip, ksft_cnt.ksft_error);
 }
 
-static inline void ksft_print_msg(const char *msg, ...)
+static inline __printf(1, 2) void ksft_print_msg(const char *msg, ...)
 {
 	int saved_errno = errno;
 	va_list args;
@@ -169,7 +171,7 @@ static inline void ksft_perror(const char *msg)
 #endif
 }
 
-static inline void ksft_test_result_pass(const char *msg, ...)
+static inline __printf(1, 2) void ksft_test_result_pass(const char *msg, ...)
 {
 	int saved_errno = errno;
 	va_list args;
@@ -183,7 +185,7 @@ static inline void ksft_test_result_pass(const char *msg, ...)
 	va_end(args);
 }
 
-static inline void ksft_test_result_fail(const char *msg, ...)
+static inline __printf(1, 2) void ksft_test_result_fail(const char *msg, ...)
 {
 	int saved_errno = errno;
 	va_list args;
@@ -209,7 +211,7 @@ static inline void ksft_test_result_fail(const char *msg, ...)
 		ksft_test_result_fail(fmt, ##__VA_ARGS__);\
 	} while (0)
 
-static inline void ksft_test_result_xfail(const char *msg, ...)
+static inline __printf(1, 2) void ksft_test_result_xfail(const char *msg, ...)
 {
 	int saved_errno = errno;
 	va_list args;
@@ -223,7 +225,7 @@ static inline void ksft_test_result_xfail(const char *msg, ...)
 	va_end(args);
 }
 
-static inline void ksft_test_result_skip(const char *msg, ...)
+static inline __printf(1, 2) void ksft_test_result_skip(const char *msg, ...)
 {
 	int saved_errno = errno;
 	va_list args;
@@ -238,7 +240,7 @@ static inline void ksft_test_result_skip(const char *msg, ...)
 }
 
 /* TODO: how does "error" differ from "fail" or "skip"? */
-static inline void ksft_test_result_error(const char *msg, ...)
+static inline __printf(1, 2) void ksft_test_result_error(const char *msg, ...)
 {
 	int saved_errno = errno;
 	va_list args;
@@ -285,7 +287,7 @@ static inline int ksft_exit_fail(void)
 		  ksft_cnt.ksft_xfail +	\
 		  ksft_cnt.ksft_xskip)
 
-static inline int ksft_exit_fail_msg(const char *msg, ...)
+static inline __printf(1, 2) int ksft_exit_fail_msg(const char *msg, ...)
 {
 	int saved_errno = errno;
 	va_list args;
@@ -312,7 +314,7 @@ static inline int ksft_exit_xpass(void)
 	exit(KSFT_XPASS);
 }
 
-static inline int ksft_exit_skip(const char *msg, ...)
+static inline __printf(1, 2) int ksft_exit_skip(const char *msg, ...)
 {
 	int saved_errno = errno;
 	va_list args;
-- 
2.42.0