[PATCH v4 next 04/23] selftests/nolibc: check vsnprintf() output buffer before the length

[david . laight . linux]

From: David Laight <david.laight.linux@xxxxxxxxx>

Check the string matches before checking the returned length.
Only print the string once when it matches.

Makes it a lot easier to diagnose any incorrect output.

Signed-off-by: David Laight <david.laight.linux@xxxxxxxxx>
---

v4: split out from patch 3

 tools/testing/selftests/nolibc/nolibc-test.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index 9787e493523c..f4813764d56e 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -1668,25 +1668,27 @@ static int expect_vfprintf(int llen, int c, const char *expected, const char *fm
 	char buf[100];
 	va_list args;
 	ssize_t w;
-	int ret;
-
 
 	va_start(args, fmt);
 	/* Only allow writing 21 bytes, to test truncation */
 	w = vsnprintf(buf, 21, fmt, args);
 	va_end(args);
 
+	llen += printf(" \"%s\"", buf);
+	if (strncmp(expected, buf, c)) {
+		llen += printf(" should be \"%s\"", expected);
+		result(llen, FAIL);
+		return 1;
+	}
+
 	if (w != c) {
 		llen += printf(" written(%d) != %d", (int)w, c);
 		result(llen, FAIL);
 		return 1;
 	}
 
-	llen += printf(" \"%s\" = \"%s\"", expected, buf);
-	ret = strncmp(expected, buf, c) != 0;
-
-	result(llen, ret ? FAIL : OK);
-	return ret;
+	result(llen, OK);
+	return 0;
 }
 
 static int test_scanf(void)
-- 
2.39.5