fixed issues regarding unsigned comparison with 0

[lenerd]

This should deal with some of the issues from #17.

I changed the return value in the error case, such that it returns the number of bytes received. Otherwise it would convert the negative error value to a positive number and use that.

[lenerd]

Well, it detects errors now.

Testing AES circuit in Boolean sharing
socket recv error: 9
Testing AES circuit in Boolean sharing
Socket error : Bad file descriptor
113.289	0.005	22.115	135.408	11511542	353600	42
116.729	0.004	22.024	138.757	11511551	353600	42
Testing AES circuit in Yao sharing
socket recv error: 9
Socket error : Bad file descriptor
socket recv error: 9
Socket error : Bad file descriptor
make: *** [runtest] Error 141

[lenerd]

The Bad file descriptor errors are result of a data race: The main thread closes the socket while another thread is still reading from it.

Excerpt of ThreadSanitizer's output (there are some more races):

WARNING: ThreadSanitizer: data race (pid=26886)
  Write of size 8 at 0x7da000008040 by main thread:
    #0 close <null> (aes.exe+0x00000047016f)
    #1 CSocket::Close() /home/lennart/git/ABY/src/examples/lowmc/../../abycore/aby/../util/../util/socket.h:114:3 (aes.exe+0x0000005b6ad0)
    #2 ABYParty::Cleanup() /home/lennart/git/ABY/src/examples/lowmc/../../abycore/aby/abyparty.cpp:144:18 (aes.exe+0x0000005b16f1)
    #3 ABYParty::~ABYParty() /home/lennart/git/ABY/src/examples/lowmc/../../abycore/aby/abyparty.cpp:92:2 (aes.exe+0x0000005b1273)
    #4 test_aes_circuit(e_role, char*, SECURITYLEVELS, unsigned int, unsigned int, e_mt_gen_alg, e_sharing, unsigned short, bool, bool) /home/lennart/git/ABY/src/examples/aes/common/aescircuit.cpp:143:2 (aes.exe+0x0000004f9685)
    #5 main <null> (aes.exe+0x000000503885)

  Previous read of size 8 at 0x7da000008040 by thread T8:
    #0 recv <null> (aes.exe+0x00000048f951)
    #1 CSocket::Receive(void*, unsigned long, int) /home/lennart/git/ABY/src/examples/lowmc/../../abycore/aby/../util/../util/socket.h:273:10 (aes.exe+0x0000005bdac4)
    #2 RcvThread::ThreadMain() /home/lennart/git/ABY/src/examples/lowmc/../../abycore/aby/../ot/../util/rcvthread.h:124:14 (aes.exe+0x0000005bd6c4)
    #3 CThread::ThreadMainHandler(void*) /home/lennart/git/ABY/src/examples/lowmc/../../abycore/ot/../util/thread.h:192:10 (aes.exe+0x00000050d852)

  Location is file descriptor 4 created by main thread at:
    #0 connect <null> (aes.exe+0x00000046fc1d)
    #1 CSocket::Connect(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, unsigned short, long) /home/lennart/git/ABY/src/examples/lowmc/../../abycore/util/crypto/../socket.h:235:13 (aes.exe+0x0000005ccb31)
    #2 Connect(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, short, std::vector<CSocket*, std::allocator<CSocket*> >&, int) /home/lennart/git/ABY/src/examples/lowmc/../../abycore/util/connection.cpp:36:20 (aes.exe+0x0000005cba88)
    #3 ABYParty::ABYPartyConnect() /home/lennart/git/ABY/src/examples/lowmc/../../abycore/aby/abyparty.cpp:512:9 (aes.exe+0x0000005b6338)
    #4 ABYParty::EstablishConnection() /home/lennart/git/ABY/src/examples/lowmc/../../abycore/aby/abyparty.cpp:489:13 (aes.exe+0x0000005b0fd1)
    #5 ABYParty::ABYParty(e_role, char*, SECURITYLEVELS, unsigned int, unsigned int, e_mt_gen_alg, unsigned int, unsigned short) /home/lennart/git/ABY/src/examples/lowmc/../../abycore/aby/abyparty.cpp:74:7 (aes.exe+0x0000005afe39)
    #6 test_aes_circuit(e_role, char*, SECURITYLEVELS, unsigned int, unsigned int, e_mt_gen_alg, e_sharing, unsigned short, bool, bool) /home/lennart/git/ABY/src/examples/aes/common/aescircuit.cpp:24:24 (aes.exe+0x0000004f8a0b)
    #7 main <null> (aes.exe+0x000000503885)

  Thread T8 (tid=26896, finished) created by main thread at:
    #0 pthread_create <null> (aes.exe+0x00000046b886)
    #1 CThread::Start() /home/lennart/git/ABY/src/examples/lowmc/../../abycore/aby/../ot/../util/thread.h:143:17 (aes.exe+0x0000005b11de)
    #2 ABYParty::EstablishConnection() /home/lennart/git/ABY/src/examples/lowmc/../../abycore/aby/abyparty.cpp:502 (aes.exe+0x0000005b11de)
    #3 ABYParty::ABYParty(e_role, char*, SECURITYLEVELS, unsigned int, unsigned int, e_mt_gen_alg, unsigned int, unsigned short) /home/lennart/git/ABY/src/examples/lowmc/../../abycore/aby/abyparty.cpp:74:7 (aes.exe+0x0000005afe39)
    #4 test_aes_circuit(e_role, char*, SECURITYLEVELS, unsigned int, unsigned int, e_mt_gen_alg, e_sharing, unsigned short, bool, bool) /home/lennart/git/ABY/src/examples/aes/common/aescircuit.cpp:24:24 (aes.exe+0x0000004f8a0b)
    #5 main <null> (aes.exe+0x000000503885)

SUMMARY: ThreadSanitizer: data race (/home/lennart/git/ABY/bin/aes.exe+0x47016f) in close

[dd23]

Thanks for your PR.
I have manually merged your changes to ENCRYPTO_utils.
I'll look into the data races next.