From: Bruno Haible <bruno@clisp.org>
Date: Fri, 8 Mar 2019 19:38:22 +0000 (+0100)
Subject: unistr/u8-cmp: Fix undefined behaviour.
X-Git-Tag: v1.0~5052
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=7e7501fa24bcd2e1484fee5648d88b8d94f0bf38;p=thirdparty%2Fgnulib.git

unistr/u8-cmp: Fix undefined behaviour.

Reported by Jeffrey Walton <noloader@gmail.com>.

* lib/unistr/u8-cmp.c (u8_cmp): Don't invoke memcmp if n is zero.
---

diff --git a/ChangeLog b/ChangeLog
index 2e6126105d..074b1caca4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2019-03-08  Bruno Haible  <bruno@clisp.org>
+
+	unistr/u8-cmp: Fix undefined behaviour.
+	Reported by Jeffrey Walton <noloader@gmail.com>.
+	* lib/unistr/u8-cmp.c (u8_cmp): Don't invoke memcmp if n is zero.
+
 2019-03-08  Bruno Haible  <bruno@clisp.org>
 
 	unictype/numeric: Fix undefined behaviour.
diff --git a/lib/unistr/u8-cmp.c b/lib/unistr/u8-cmp.c
index bd2f11bea9..5349ec63d0 100644
--- a/lib/unistr/u8-cmp.c
+++ b/lib/unistr/u8-cmp.c
@@ -26,5 +26,5 @@ int
 u8_cmp (const uint8_t *s1, const uint8_t *s2, size_t n)
 {
   /* Use the fact that the UTF-8 encoding preserves lexicographic order.  */
-  return memcmp ((const char *) s1, (const char *) s2, n);
+  return n == 0 ? 0 : memcmp ((const char *) s1, (const char *) s2, n);
 }