Fix strlcpy

libc/str/strlcpy.c

@@ -34,7 +34,7 @@ size_t strlcpy(char *d, const char *s, size_t n) {
   size_t slen, actual;
   slen = strlen(s);
   if (n) {
-    actual = MIN(n, slen);
+    actual = MIN(n - 1, slen);
     memcpy(d, s, actual);
     d[actual] = '\0';
   }

test/libc/str/strlcpy_test.c

@@ -0,0 +1,37 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ This program 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; version 2 of the License.                      │
+│                                                                              │
+│ This program 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 this program; if not, write to the Free Software                  │
+│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA                │
+│ 02110-1301 USA                                                               │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/str/str.h"
+#include "libc/testlib/testlib.h"
+
+TEST(strlcpy, testEmptyBuffer_doesNothing) {
+  EXPECT_EQ(5, strlcpy(NULL, "hello", 0));
+}
+
+TEST(strlcpy, testShortBuffer_nulTerminates) {
+  char buf[1] = {1};
+  EXPECT_EQ(5, strlcpy(buf, "hello", 1));
+  EXPECT_STREQ("", buf);
+}
+
+TEST(strlcpy, testShortBuffer_copies) {
+  char buf[2] = {1, 1};
+  EXPECT_EQ(5, strlcpy(buf, "hello", 2));
+  EXPECT_STREQ("h", buf);
+}