test/secmemtest.c: clarify limitations for huge secure memory arena test.

     *

     * CRYPTO_secure_malloc_init((size_t)1<<34, (size_t)1<<4);

     *

     * Which really only works on 64-bit systems, and even then the

     * code attempts to allocate 16 GB secure memory arena. Linux

     * can deal with this better than other Unixy OS's (e.g. MacOS)

     * but we don't want to push the system too hard during a unit

     * test. In addition, trying to allocate 16GB will cause the

     * mlock() call to fail, so that was at least changed to no

     * longer be an assert. If the reader of this comment really

     * wants to make sure that infinite loop is fixed, they can

     * enable the code below.

     * Which really only works on 64-bit systems, since it took 16 GB

     * secure memory arena to trigger the problem. It naturally takes

     * corresponding amount of available virtual and physical memory

     * for test to be feasible/representative. Since we can't assume

     * that every system is equipped with that much memory, the test

     * remains disabled. If the reader of this comment really wants

     * to make sure that infinite loop is fixed, they can enable the

     * code below.

     */

# if 0

    /* This test should only be run under Linux... runner beware */

    /*-

     * On Linux and BSD this test has a chance to complete in minimal

     * time and with minimum side effects, because mlock is likely to

     * fail because of RLIMIT_MEMLOCK, which is customarily [much]

     * smaller than 16GB. In other words Linux and BSD users can be

     * limited by virtual space alone...

     */

    if (sizeof(size_t) > 4) {

        TEST_info("Possible infinite loop: 1<<31 limit");

        if (TEST_true(CRYPTO_secure_malloc_init((size_t)1<<34, (size_t)1<<4) != 0))