linux-kernel - [PATCH v2 3/4] tools/nolibc: add missing memchr() to string.h

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Message-Id: <20251102104611.24454-4-w@1wt.eu>
Date: Sun,  2 Nov 2025 11:46:10 +0100
From: Willy Tarreau <w@....eu>
To: linux@...ssschuh.net
Cc: shuah@...nel.org, linux-kernel@...r.kernel.org, Willy Tarreau <w@....eu>
Subject: [PATCH v2 3/4] tools/nolibc: add missing memchr() to string.h

Surprisingly we forgot to add this common one. It was added with a
per-arch guard allowing to later implement it in arch-specific asm
code like was done for a few other ones.

The test verifies that we don't search past the indicated length.

Signed-off-by: Willy Tarreau <w@....eu>
---
 tools/include/nolibc/string.h                | 15 +++++++++++++++
 tools/testing/selftests/nolibc/nolibc-test.c |  2 ++
 2 files changed, 17 insertions(+)

diff --git a/tools/include/nolibc/string.h b/tools/include/nolibc/string.h
index 163a17e7dd38..4000926f44ac 100644
--- a/tools/include/nolibc/string.h
+++ b/tools/include/nolibc/string.h
@@ -93,6 +93,21 @@ void *memset(void *dst, int b, size_t len)
 }
 #endif /* #ifndef NOLIBC_ARCH_HAS_MEMSET */
 
+#ifndef NOLIBC_ARCH_HAS_MEMCHR
+static __attribute__((unused))
+void *memchr(const void *s, int c, size_t len)
+{
+	char *p = (char *)s;
+
+	while (len--) {
+		if (*p == (char)c)
+			return p;
+		p++;
+	}
+	return NULL;
+}
+#endif /* #ifndef NOLIBC_ARCH_HAS_MEMCHR */
+
 static __attribute__((unused))
 char *strchr(const char *s, int c)
 {
diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index 2b1fcfaaa60e..7fc937e9a4df 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -1558,6 +1558,8 @@ int run_stdlib(int min, int max)
 		CASE_TEST(abs_noop);                EXPECT_EQ(1, abs(10), 10); break;
 		CASE_TEST(difftime);                EXPECT_ZR(1, test_difftime()); break;
 		CASE_TEST(test_timespec);           EXPECT_ZR(1, test_timespec()); break;
+		CASE_TEST(memchr_foobar6_o);        EXPECT_STREQ(1, memchr("foobar", 'o', 6), "oobar"); break;
+		CASE_TEST(memchr_foobar3_b);        EXPECT_STRZR(1, memchr("foobar", 'b', 3)); break;
 
 		case __LINE__:
 			return ret; /* must be last */
-- 
2.17.5