From 9aa8a4afd4e6407a4d4521c325855c4467a88b73 Mon Sep 17 00:00:00 2001 From: David Laight Date: Mon, 2 Mar 2026 10:17:56 +0000 Subject: selftests/nolibc: check vsnprintf() output buffer before the length MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Acked-by: Willy Tarreau Link: https://patch.msgid.link/20260302101815.3043-5-david.laight.linux@gmail.com Signed-off-by: Thomas Weißschuh --- tools/testing/selftests/nolibc/nolibc-test.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) (limited to 'tools/testing') diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c index 7588212df124..bfe793caa963 100644 --- a/tools/testing/selftests/nolibc/nolibc-test.c +++ b/tools/testing/selftests/nolibc/nolibc-test.c @@ -1676,25 +1676,27 @@ 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) -- cgit v1.2.3