After building LibreSSL with -fPIC (cf. issue #94) the build of s2n itself fails during the unit tests. I have seen two different failures after repeated build attempts.

One of them (s2n_client_extensions_test) is sporadic and mlock() related and I see a note for that in the USAGE docs so I won't consider that further here.

The other failure that I've seen is s2n_override_openssl_random_test. This fails on every invocation at test 20:

$ LD_LIBRARY_PATH=../../lib ./s2n_override_openssl_random_test
Running s2n_override_openssl_random_test.c                 ... FAILED test 20
(mock_called) == (1) is not true  (s2n_override_openssl_random_test.c line 114)
Error Message: 'no error'

Relevant lines from the test:

109     EXPECT_EQUAL(mock_called, 0);
110 
111     EXPECT_TRUE(DH_generate_key(dh_params.dh) == 1);
112 
113     /* Verify that our mock random is called and that over-riding works */
114     EXPECT_EQUAL(mock_called, 1);

from which I gather that mock_openssl_compat_rand() is not being called.

This can happen if it is actually being called but it returns early if the call to s2n_get_urandom_data() fails so this is my primary suspect for now.

 39 static int mock_openssl_compat_rand(unsigned char *buf, int num)
 40 {
 41     struct s2n_blob blob = {.data = buf, .size = num };
 42 
 43     int r = s2n_get_urandom_data(&blob);
 44     if (r < 0) {
 45         return 0;
 46     }
 47 
 48     mock_called = 1;

I'm out of time today! Will try to debug more tomorrow.