From 902ed2524a19d41a6a06b2bd3e38ad6c66b339fd Mon Sep 17 00:00:00 2001
From: "Jan (janneke) Nieuwenhuizen" <janneke@gnu.org>
Date: Sat, 6 Jun 2020 22:37:30 +0200
Subject: [PATCH] mescc: Mes C Library: memcmp: bugfix.

* lib/string/memcmp.c (memcmp): Bugfix.
* lib/tests/string/50-memcmp.c: Test it.
* build-aux/check-mescc.sh (TESTS): Add it.
---
 build-aux/check-mescc.sh     |  1 +
 lib/string/memcmp.c          |  3 ++-
 lib/tests/string/50-memcmp.c | 46 ++++++++++++++++++++++++++++++++++++
 3 files changed, 49 insertions(+), 1 deletion(-)
 create mode 100644 lib/tests/string/50-memcmp.c

diff --git a/build-aux/check-mescc.sh b/build-aux/check-mescc.sh
index 15e92451..16895ee2 100755
--- a/build-aux/check-mescc.sh
+++ b/build-aux/check-mescc.sh
@@ -105,6 +105,7 @@ lib/tests/assert/50-assert.c
 lib/tests/mes/50-itoa.c
 lib/tests/posix/50-getenv.c
 lib/tests/stdlib/50-malloc.c
+lib/tests/string/50-memcmp.c
 lib/tests/string/50-strcmp.c
 lib/tests/string/50-strcmp-itoa.c
 lib/tests/string/50-strcpy.c
diff --git a/lib/string/memcmp.c b/lib/string/memcmp.c
index 4f33e1c3..ca72f638 100644
--- a/lib/string/memcmp.c
+++ b/lib/string/memcmp.c
@@ -29,11 +29,12 @@ memcmp (void const *s1, void const *s2, size_t size)
   char const *a = s1;
   char const *b = s2;
 
-  while (a[0] == b[0] && size > 0)
+  while (a[0] == b[0] && size > 1)
     {
       size = size - 1;
       a = a + 1;
       b = b + 1;
     }
+
   return a[0] - b[0];
 }
diff --git a/lib/tests/string/50-memcmp.c b/lib/tests/string/50-memcmp.c
new file mode 100644
index 00000000..8aa2bde6
--- /dev/null
+++ b/lib/tests/string/50-memcmp.c
@@ -0,0 +1,46 @@
+/* -*-comment-start: "//";comment-end:""-*-
+ * GNU Mes --- Maxwell Equations of Software
+ * Copyright © 2019 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ *
+ * This file is part of GNU Mes.
+ *
+ * GNU Mes is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or (at
+ * your option) any later version.
+ *
+ * GNU Mes is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <mes/lib.h>
+
+#include <string.h>
+
+int
+main ()
+{
+  char *p = "mes";
+
+  if (!memcmp (p, "foo", 3))
+    return 1;
+
+  if (memcmp (p, "mes", 3))
+    return 2;
+
+  if (memcmp (p, "mes", 4))
+    return 3;
+
+  if (!memcmp (p, "mesx", 4))
+    return 4;
+
+  if (memcmp (p, "mesx", 3))
+    return 5;
+
+  return 0;
+}