[tor-bugs] #14982 [Tor]: fails to establish connections due to gcc 5.0 bug/feature with -O3

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#14982: fails to establish connections due to gcc 5.0 bug/feature with -O3
--------------------+------------------------------------
 Reporter:  Safari  |          Owner:
     Type:  defect  |         Status:  new
 Priority:  major   |      Milestone:  Tor: 0.2.6.x-final
Component:  Tor     |        Version:  Tor: 0.2.6.3-alpha
 Keywords:          |  Actual Points:
Parent ID:          |         Points:
--------------------+------------------------------------
 gcc 5.0 with -O3 seems to compile curve25519-donna-c64.c so that
 curve25519_donna writes all-zeros to mypublic.
 This is caught by "make test", but not when starting tor, I hope this
 check is added to tor on startup.

 When one just starts tor, debug logs point nowhere, because they assume
 curve25519 works OK.

 ntor_handshake:
   FAIL src/test/test.c:238: assert(0 OP_EQ
 onion_skin_ntor_server_handshake(c_buf, s_keymap, NULL, node_id, s_buf,
 s_keys, 400)): 0 vs -1
   [ntor_handshake FAILED]
 crypto/curve25519_impl:
   FAIL src/test/test_crypto.c:1018: assert(e1 == mem_op_hex_tmp):
 0300000000000000000000000000000000000000000000000000000000000000 vs
 BC7112CDE03F97EF7008CAD1BDC56BE3C6A1037D74CCEB3712E9206871DCF654
   [curve25519_impl FAILED]
 crypto/curve25519_impl_hibit:
   FAIL src/test/test_crypto.c:1018: assert(e1 == mem_op_hex_tmp):
 0300000000000000000000000000000000000000000000000000000000000000 vs
 BC7112CDE03F97EF7008CAD1BDC56BE3C6A1037D74CCEB3712E9206871DCF654
   [curve25519_impl_hibit FAILED]
 crypto/curve25519_wrappers:
   FAIL src/test/test_crypto.c:1041:
 assert(curve25519_public_key_is_ok(&pubkey1))
   [curve25519_wrappers FAILED]
 crypto/ed25519_convert: [err] tor_assertion_failed_(): Bug:
 src/common/crypto_ed25519.c:214: ed25519_keypair_from_curve25519_keypair:
 Assertion fast_memeq(pubkey_check.pubkey, out->pubkey.pubkey, 32) failed;
 aborting.
 [err] Bug: Assertion fast_memeq(pubkey_check.pubkey, out->pubkey.pubkey,
 32) failed in ed25519_keypair_from_curve25519_keypair at
 src/common/crypto_ed25519.c:214. Stack trace:

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/14982>
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