[PATCH v7 4/7] selftests: ksft_exit_fail_perror: support printf style arguments

[Chunyu Hu <chuhu@redhat.com>]

The ksft_exit_fail_perror function previously only accepted a single string
argument, which limited its flexibility for providing specific context to
failure messages.

This change updates ksft_exit_fail_perror to support variable arguments,
similar to ksft_exit_fail_msg.  Adding the __printf(1, 2) attribute enables
compile-time checking for format string correctness.

Signed-off-by: Chunyu Hu <chuhu@redhat.com>
---
Changes in v7:
  - new patch to convert ksft_exit_fail_perror support variable arguments
---
 tools/testing/selftests/kselftest.h | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/kselftest.h b/tools/testing/selftests/kselftest.h
index afbcf8412ae5..11cabdabb3f6 100644
--- a/tools/testing/selftests/kselftest.h
+++ b/tools/testing/selftests/kselftest.h
@@ -43,7 +43,7 @@
  * the program is aborting before finishing all tests):
  *
  *    ksft_exit_fail_msg(fmt, ...);
- *    ksft_exit_fail_perror(msg);
+ *    ksft_exit_fail_perror(fmt, ...);
  *
  */
 #ifndef __KSELFTEST_H
@@ -417,9 +417,24 @@ static inline __noreturn __printf(1, 2) void ksft_exit_fail_msg(const char *msg,
 	exit(KSFT_FAIL);
 }
 
-static inline __noreturn void ksft_exit_fail_perror(const char *msg)
+static inline __noreturn __printf(1, 2) void ksft_exit_fail_perror(const char *msg, ...)
 {
-	ksft_exit_fail_msg("%s: %s (%d)\n", msg, strerror(errno), errno);
+	va_list args;
+	char *buf = NULL;
+	int saved_errno = errno;
+
+	va_start(args, msg);
+	if (vasprintf(&buf, msg, args) == -1) {
+		va_end(args);
+		ksft_exit_fail_msg("vasprintf failed: %s (%d)\n", strerror(saved_errno),
+				saved_errno);
+	}
+	va_end(args);
+
+	errno = saved_errno;
+	ksft_exit_fail_msg("%s: %s (%d)\n", buf, strerror(errno), errno);
+
+	free(buf);
 }
 
 static inline __noreturn void ksft_exit_xfail(void)
-- 
2.53.0