Use gnutls-openssl instead of gnutls to fix build with CMake.

[ghost]

Hi again! [#562]

When I try compile Zoneminder with GnuTLS in Debian 7 I allways get this error:

libzm.a(zm_rtsp_auth.cpp.o): In function `Authenticator::computeDigestResponse(std::string&, std::string&)':
zm_rtsp_auth.cpp:(.text+0x24e6): undefined reference to `MD5'
zm_rtsp_auth.cpp:(.text+0x2594): undefined reference to `MD5'
zm_rtsp_auth.cpp:(.text+0x26d8): undefined reference to `MD5'
libzm.a(zm_user.cpp.o): In function `zmLoadAuthUser(char const*, bool)':
zm_user.cpp:(.text+0x1115): undefined reference to `MD5'
collect2: error: ld returned 1 exit status

I have libgnutls-openssl27 and of course, libgnutls-dev packages installed in my build machine. Also, I can build a ZoneMinder package with autotools without any issue.

It seems that CMake integration don't use '-lgnutls-openssl' on the C++ linker, only '-lgnutls'.

If we know that gnutls-openssl, as a wrapper, depends on gnutls...

root@debian:~/zm# ldd /usr/lib/i386-linux-gnu/libgnutls-openssl.so
    linux-gate.so.1 =>  (0xb76fb000)
    libtasn1.so.3 => /usr/lib/i386-linux-gnu/libtasn1.so.3 (0xb76d3000)
    libp11-kit.so.0 => /usr/lib/i386-linux-gnu/libp11-kit.so.0 (0xb76c1000)
    libgnutls.so.26 => /usr/lib/i386-linux-gnu/libgnutls.so.26 (0xb75f7000)
    libc.so.6 => /lib/i386-linux-gnu/i686/cmov/libc.so.6 (0xb7492000)
    libdl.so.2 => /lib/i386-linux-gnu/i686/cmov/libdl.so.2 (0xb748e000)
    libpthread.so.0 => /lib/i386-linux-gnu/i686/cmov/libpthread.so.0 (0xb7475000)
    libgcrypt.so.11 => /lib/i386-linux-gnu/libgcrypt.so.11 (0xb73f0000)
    libz.so.1 => /lib/i386-linux-gnu/libz.so.1 (0xb73d6000)
    /lib/ld-linux.so.2 (0xb76fc000)
    libgpg-error.so.0 => /lib/i386-linux-gnu/libgpg-error.so.0 (0xb73d2000)

I think that this commit is just enough to fix the problem.

I tested in my build machine and works.

[knight-of-ni]

Nice work. However, can you test the following change for me?

find_library(GNUTLS_LIBRARIES NAMES gnutls gnutls-openssl)

RPM based distros package things differently and do not have a gnutls-openssl package. Fortunately, cmake lets us easily search for multiple package names. This is why I really like cmake over autotools.

Don't know if you know this, but you can push changes against your open pull request and they will automatically show up. e.g. you don't have to close this and open a new pull request.

[ghost]

That change doesn't work at least for me. Compilation throws the same error.

[knight-of-ni]

okay, we'll get this. I wonder if cmake stops searching after it finds the first match, in which case, it might be worth changing the order:

find_library(GNUTLS_LIBRARIES NAMES gnutls-openssl gnutls)

Try that, and in the meantime I'll come up with a "Plan B".

[knight-of-ni]

That last suggestion doesn't work either. Here is plan B:

find_library(GNUTLS_LIBRARIES gnutls-openssl)
if(NOT GNUTLS_LIBRARIES)
    find_library(GNUTLS_LIBRARIES gnutls)
endif(NOT GNUTLS_LIBRARIES)

This works on CentOS. Let me know if Debian agrees.

[ghost]

Works without any problem.

Thanks for all!