+ errno = 0;
+#if UINTMAX_MAX == 0xffffffffffffffffLL
+ /* testing "even" overflow, i.e. base is power of two */
+ TESTCASE( strtoumax( "18446744073709551615", NULL, 0 ) == UINTMAX_MAX );
+ TESTCASE( errno == 0 );
+ TESTCASE( strtoumax( "18446744073709551616", NULL, 0 ) == UINTMAX_MAX );
+ TESTCASE( errno == ERANGE );
+ /* TODO: test "odd" overflow, i.e. base is not power of two */
+#elif UINTMAX_MAX == 0xffffffffffffffffffffffffffffffffLL
+ /* testing "even" overflow, i.e. base is power of two */
+ TESTCASE( strtoumax( "340282366920938463463374607431768211455", NULL, 0 ) == UINTMAX_MAX );
+ TESTCASE( errno == 0 );
+ TESTCASE( strtoumax( "340282366920938463463374607431768211456", NULL, 0 ) == UINTMAX_MAX );
+ TESTCASE( errno == ERANGE );
+ /* TODO: test "odd" overflow, i.e. base is not power of two */
+#else
+#error Unsupported width of 'uintmax_t' (neither 64 nor 128 bit).
+#endif