Index: lib/libc/tests/stdlib/Makefile
===================================================================
--- lib/libc/tests/stdlib/Makefile
+++ lib/libc/tests/stdlib/Makefile
@@ -6,6 +6,7 @@
 ATF_TESTS_C+=		heapsort_test
 ATF_TESTS_C+=		mergesort_test
 ATF_TESTS_C+=		qsort_test
+ATF_TESTS_C+=		qsort_r_test
 ATF_TESTS_C+=		set_constraint_handler_s_test
 ATF_TESTS_C+=		strfmon_test
 ATF_TESTS_C+=		tsearch_test
Index: lib/libc/tests/stdlib/qsort_r_test.c
===================================================================
--- /dev/null
+++ lib/libc/tests/stdlib/qsort_r_test.c
@@ -0,0 +1,93 @@
+/*-
+ * Copyright (C) 2020 Edward Tomasz Napierala <trasz@FreeBSD.org>
+ * Copyright (C) 2004 Maxim Sobolev <sobomax@FreeBSD.org>
+ * 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.
+ */
+
+/*
+ * Test for qsort() routine.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#define	THUNK 42
+
+#include "test-sort.h"
+
+static int
+sorthelp_r(void *thunk, const void *a, const void *b)
+{
+	const int *oa, *ob;
+
+	ATF_REQUIRE_EQ(*(int *)thunk, THUNK);
+
+	oa = a;
+	ob = b;
+	/* Don't use "return *oa - *ob" since it's easy to cause overflow! */
+	if (*oa > *ob)
+		return (1);
+	if (*oa < *ob)
+		return (-1);
+	return (0);
+}
+
+ATF_TC_WITHOUT_HEAD(qsort_r_test);
+ATF_TC_BODY(qsort_r_test, tc)
+{
+	int testvector[IVEC_LEN];
+	int sresvector[IVEC_LEN];
+	int i, j;
+	int thunk = THUNK;
+
+	for (j = 2; j < IVEC_LEN; j++) {
+		/* Populate test vectors */
+		for (i = 0; i < j; i++)
+			testvector[i] = sresvector[i] = initvector[i];
+
+		/* Sort using qsort_r(3) */
+		qsort_r(testvector, j, sizeof(testvector[0]), &thunk,
+		    sorthelp_r);
+		/* Sort using reference slow sorting routine */
+		ssort(sresvector, j);
+
+		/* Compare results */
+		for (i = 0; i < j; i++)
+			ATF_CHECK_MSG(testvector[i] == sresvector[i],
+			    "item at index %d didn't match: %d != %d",
+			    i, testvector[i], sresvector[i]);
+	}
+}
+
+ATF_TP_ADD_TCS(tp)
+{
+
+	ATF_TP_ADD_TC(tp, qsort_r_test);
+
+	return (atf_no_error());
+}