iconvctl(3): remove superfluous NULL pointer tests

convname and dst are guaranteed to be non-NULL by iconv_open(3).
src is an array. Remove these tests for NULL pointers.
While I'm here, eliminate a strlcpy with a correct but suspicious-looking
calculation for the third parameter (i.e. not a simple sizeof).
Compare the strings in-place instead of copying.

Found by:	bdrewery
Found by:	Coverity
CID:		1130050, 1130056
MFC after:	3 days
Sponsored by:	Dell Inc.
Differential Revision:	 https://reviews.freebsd.org/D6338

etc/mtree/BSD.tests.dist

@@ -261,6 +261,8 @@
                 data
                 ..
             ..
+            iconv
+            ..
             inet
             ..
             locale

lib/libc/iconv/bsd_iconv.c

@@ -267,8 +267,9 @@ __bsd_iconvctl(iconv_t cd, int request, void *argument)
 	struct _citrus_iconv *cv;
 	struct iconv_hooks *hooks;
 	const char *convname;
-	char src[PATH_MAX], *dst;
+	char *dst;
 	int *i;
+	size_t srclen;
 
 	cv = (struct _citrus_iconv *)(void *)cd;
 	hooks = (struct iconv_hooks *)argument;
@@ -283,12 +284,9 @@ __bsd_iconvctl(iconv_t cd, int request, void *argument)
 	case ICONV_TRIVIALP:
 		convname = cv->cv_shared->ci_convname;
 		dst = strchr(convname, '/');
-
-		strlcpy(src, convname, dst - convname + 1);
+		srclen = dst - convname;
 		dst++;
-		if ((convname == NULL) || (src == NULL) || (dst == NULL))
-			return (-1);
-		*i = strcmp(src, dst) == 0 ? 1 : 0;
+		*i = (srclen == strlen(dst)) && !memcmp(convname, dst, srclen);
 		return (0);
 	case ICONV_GET_TRANSLITERATE:
 		*i = 1;

lib/libc/tests/Makefile

@@ -8,6 +8,7 @@ TESTS_SUBDIRS=	c063
 TESTS_SUBDIRS+=	db
 TESTS_SUBDIRS+=	gen
 TESTS_SUBDIRS+=	hash
+TESTS_SUBDIRS+=	iconv
 TESTS_SUBDIRS+=	inet
 TESTS_SUBDIRS+=	net
 TESTS_SUBDIRS+=	nss

lib/libc/tests/iconv/Makefile

@@ -0,0 +1,9 @@
+# $FreeBSD$
+
+PACKAGE=	tests
+
+TESTSDIR=	${TESTSBASE}/lib/libc/iconv
+
+ATF_TESTS_C+=	iconvctl_test
+
+.include <bsd.test.mk>

lib/libc/tests/iconv/iconvctl_test.c

@@ -0,0 +1,69 @@
+/*-
+ * Copyright (c) 2016 Eric van Gyzen
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <iconv.h>
+
+#include <atf-c.h>
+
+void
+test_trivialp(const char *src, const char *dst, int expected)
+{
+	iconv_t ic;
+	int actual, status;
+
+	ic = iconv_open(dst, src);
+	ATF_REQUIRE(ic != (iconv_t)-1);
+
+	status = iconvctl(ic, ICONV_TRIVIALP, &actual);
+	ATF_REQUIRE(status == 0);
+
+	ATF_REQUIRE(actual == expected);
+
+	status = iconv_close(ic);
+	ATF_REQUIRE(status == 0);
+}
+
+ATF_TC_WITHOUT_HEAD(iconvctl_trivialp_test);
+ATF_TC_BODY(iconvctl_trivialp_test, tc)
+{
+
+	test_trivialp("ISO-8859-1",  "ISO-8859-1",  1);
+	test_trivialp("ISO-8859-1",  "ISO-8859-15", 0);
+	test_trivialp("ISO-8859-15", "ISO-8859-1",  0);
+	test_trivialp("ISO-8859-15", "UTF-8",       0);
+	test_trivialp("UTF-8",       "ASCII",       0);
+}
+
+ATF_TP_ADD_TCS(tp)
+{
+
+	ATF_TP_ADD_TC(tp, iconvctl_trivialp_test);
+
+	return (atf_no_error());
+}