linux-kernel - [PATCH 2/2] selftests/nolibc: add tests for printf zero padding (0)

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Message-ID: <20260130083737.1123-2-im.lechain@gmail.com>
Date: Fri, 30 Jan 2026 16:37:36 +0800
From: "licheng.li" <im.lechain@...il.com>
To: Willy Tarreau <w@....eu>,
	David Laight <david.laight.linux@...il.com>
Cc: Thomas Weißschuh <linux@...ssschuh.net>,
	linux-kernel@...r.kernel.org,
	im.lechain@...il.com
Subject: [PATCH 2/2] selftests/nolibc: add tests for printf zero padding (0)

From: Cheng Li <im.lechain@...il.com>

This patch adds validation for the '0' flag in printf() to ensure correct
behavior for pointers, positive integers, and negative integers.

The tests specifically verify that:
 - Pointers include the '0x' prefix before padding.
 - Negative numbers include the '-' sign before padding.
 - Width and padding are correctly calculated.

Signed-off-by: Cheng Li <im.lechain@...il.com>
---
 tools/testing/selftests/nolibc/nolibc-test.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index c11fcf6c5075..77bb8796aa3d 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -1723,6 +1723,9 @@ static int run_printf(int min, int max)
 		CASE_TEST(truncation);   EXPECT_VFPRINTF(25, "01234567890123456789", "%s", "0123456789012345678901234"); break;
 		CASE_TEST(string_width); EXPECT_VFPRINTF(10, "         1", "%10s", "1"); break;
 		CASE_TEST(number_width); EXPECT_VFPRINTF(10, "         1", "%10d", 1); break;
+		CASE_TEST(zero_pad_ptr); EXPECT_VFPRINTF(5, "0x005", "%05p", (void *)5); break;
+		CASE_TEST(zero_pad_int); EXPECT_VFPRINTF(5, "00005", "%05d", 5); break;
+		CASE_TEST(zero_pad_neg); EXPECT_VFPRINTF(5, "-0005", "%05d", -5); break;
 		CASE_TEST(number_left);  EXPECT_VFPRINTF(10, "|-5      |", "|%-8d|", -5); break;
 		CASE_TEST(string_align); EXPECT_VFPRINTF(10, "|foo     |", "|%-8s|", "foo"); break;
 		CASE_TEST(width_trunc);  EXPECT_VFPRINTF(25, "                    ", "%25d", 1); break;
-- 
2.52.0