diff -r 72e5432f6b42 -r c9b02747cfc5 tests/test_szmul.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/test_szmul.c	Sat Nov 02 13:38:51 2024 +0100
@@ -0,0 +1,162 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
+ *
+ * Copyright 2023 Mike Becker, Olaf Wintermann 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 COPYRIGHT HOLDERS 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 COPYRIGHT HOLDER 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 "cx/test.h"
+
+CX_TEST(test_szmul) {
+    size_t r;
+    int e;
+
+    CX_TEST_DO {
+        e = cx_szmul(5, 7, &r);
+        CX_TEST_ASSERT(e == 0);
+        CX_TEST_ASSERT(r == 35);
+
+        size_t s = SIZE_MAX & ~3;
+
+        e = cx_szmul(s / 4, 2, &r);
+        CX_TEST_ASSERT(e == 0);
+        CX_TEST_ASSERT(r == s / 2);
+
+        e = cx_szmul(2, s / 4, &r);
+        CX_TEST_ASSERT(e == 0);
+        CX_TEST_ASSERT(r == s / 2);
+
+        e = cx_szmul(s / 4, 4, &r);
+        CX_TEST_ASSERT(e == 0);
+        CX_TEST_ASSERT(r == s);
+
+        e = cx_szmul(4, s / 4, &r);
+        CX_TEST_ASSERT(e == 0);
+        CX_TEST_ASSERT(r == s);
+
+        e = cx_szmul(s / 4, 5, &r);
+        CX_TEST_ASSERT(e != 0);
+
+        e = cx_szmul(5, s / 4, &r);
+        CX_TEST_ASSERT(e != 0);
+
+        e = cx_szmul(SIZE_MAX - 4, 0, &r);
+        CX_TEST_ASSERT(e == 0);
+        CX_TEST_ASSERT(r == 0);
+
+        e = cx_szmul(0, SIZE_MAX - 1, &r);
+        CX_TEST_ASSERT(e == 0);
+        CX_TEST_ASSERT(r == 0);
+
+        e = cx_szmul(SIZE_MAX, 0, &r);
+        CX_TEST_ASSERT(e == 0);
+        CX_TEST_ASSERT(r == 0);
+
+        e = cx_szmul(0, SIZE_MAX, &r);
+        CX_TEST_ASSERT(e == 0);
+        CX_TEST_ASSERT(r == 0);
+
+        e = cx_szmul(0, 0, &r);
+        CX_TEST_ASSERT(e == 0);
+        CX_TEST_ASSERT(r == 0);
+    }
+}
+
+#ifdef CX_SZMUL_BUILTIN
+
+// also test the custom implementation
+#undef CX_SZMUL_BUILTIN
+
+#include "../src/szmul.c"
+
+#define CX_SZMUL_BUILTIN
+
+CX_TEST(test_szmul_impl) {
+    size_t r;
+    int e;
+
+    CX_TEST_DO {
+        e = cx_szmul_impl(5, 7, &r);
+        CX_TEST_ASSERT(e == 0);
+        CX_TEST_ASSERT(r == 35);
+
+        size_t s = SIZE_MAX & ~3;
+
+        e = cx_szmul_impl(s / 4, 2, &r);
+        CX_TEST_ASSERT(e == 0);
+        CX_TEST_ASSERT(r == s / 2);
+
+        e = cx_szmul_impl(2, s / 4, &r);
+        CX_TEST_ASSERT(e == 0);
+        CX_TEST_ASSERT(r == s / 2);
+
+        e = cx_szmul_impl(s / 4, 4, &r);
+        CX_TEST_ASSERT(e == 0);
+        CX_TEST_ASSERT(r == s);
+
+        e = cx_szmul_impl(4, s / 4, &r);
+        CX_TEST_ASSERT(e == 0);
+        CX_TEST_ASSERT(r == s);
+
+        e = cx_szmul_impl(s / 4, 5, &r);
+        CX_TEST_ASSERT(e != 0);
+
+        e = cx_szmul_impl(5, s / 4, &r);
+        CX_TEST_ASSERT(e != 0);
+
+        e = cx_szmul_impl(SIZE_MAX - 4, 0, &r);
+        CX_TEST_ASSERT(e == 0);
+        CX_TEST_ASSERT(r == 0);
+
+        e = cx_szmul_impl(0, SIZE_MAX - 1, &r);
+        CX_TEST_ASSERT(e == 0);
+        CX_TEST_ASSERT(r == 0);
+
+        e = cx_szmul_impl(SIZE_MAX, 0, &r);
+        CX_TEST_ASSERT(e == 0);
+        CX_TEST_ASSERT(r == 0);
+
+        e = cx_szmul_impl(0, SIZE_MAX, &r);
+        CX_TEST_ASSERT(e == 0);
+        CX_TEST_ASSERT(r == 0);
+
+        e = cx_szmul_impl(0, 0, &r);
+        CX_TEST_ASSERT(e == 0);
+        CX_TEST_ASSERT(r == 0);
+    }
+}
+
+#endif // CX_SZMUL_BUILTIN
+
+
+CxTestSuite *cx_test_suite_szmul(void) {
+    CxTestSuite *suite = cx_test_suite_new("szmul");
+
+    cx_test_register(suite, test_szmul);
+#ifdef CX_SZMUL_BUILTIN
+    cx_test_register(suite, test_szmul_impl);
+#endif
+
+    return suite;
+}