How do I properly link libssh?

问题:

I'm trying to include a lib into my code (libssh) but nothing works... At this point I'm unsure what to do as no results are popping up in search engines for the errors i'm recieving.

I downloaded libssh here: https://github.com/substack/libssh

I installed these:

yum install cmake zlib-devel libpng-devel openssl-devel -y;

Created a "build" directory as parent of libssh, moved there, typed this:

cmake -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_BUILD_TYPE=Debug ..
make


[root@ build]# cmake -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_BUILD_TYPE=Debug LD_DEBUG=all ..
-- Could NOT find NaCl (missing:  NACL_LIBRARIES NACL_INCLUDE_DIRS)
-- ********************************************
-- ********** libssh build options : **********
-- zlib support: ON
-- libgcrypt support: OFF
-- libnacl support: OFF
-- SSH-1 support: OFF
-- SFTP support: ON
-- Server support : ON
-- GSSAPI support : ON
-- Pcap debugging support : ON
-- With static library: OFF
-- Unit testing: OFF
-- Client code Unit testing: OFF
-- Public API documentation generation
-- Benchmarks: OFF
-- ********************************************
-- Configuring done
-- Generating done
-- Build files have been written to: /root/libssh/build

And then it fails...

Scanning dependencies of target exec
[  2%] Building C object examples/CMakeFiles/exec.dir/exec.c.o
[  5%] Building C object examples/CMakeFiles/exec.dir/authentication.c.o
[  8%] Building C object examples/CMakeFiles/exec.dir/knownhosts.c.o
[ 11%] Building C object examples/CMakeFiles/exec.dir/connect_ssh.c.o
Linking C executable exec
/usr/bin/ld: cannot find -lssh_shared
collect2: ld a retourné 1 code d'état d'exécution
make[2]: *** [examples/exec] Erreur 1
make[1]: *** [examples/CMakeFiles/exec.dir/all] Erreur 2
make: *** [all] Erreur 2

Anyone know what the problem is? "cannot find -lssh_shared" showed me nothing related on google.

回答1:

The error message is resulted from the linker /usr/bin/ld is failed to link to the library ssh_shared.so while compiling.

I checked the file libssh/build/src/CMakeFiles/ssh_shared.dir/build.make, there's some linking messages inside:

ssh_shared_EXTERNAL_OBJECTS =
src/libssh.so.4.2.0: /usr/lib/x86_64-linux-gnu/libz.so
src/libssh.so.4.2.0: /usr/lib/x86_64-linux-gnu/libssl.so
src/libssh.so.4.2.0: /usr/lib/x86_64-linux-gnu/libcrypto.so

... (snippet here) ...
src/libssh.so.4.2.0: src/CMakeFiles/ssh_shared.dir/bind.c.o
src/libssh.so.4.2.0: /usr/lib/x86_64-linux-gnu/libz.so
src/libssh.so.4.2.0: /usr/lib/x86_64-linux-gnu/libssl.so
src/libssh.so.4.2.0: /usr/lib/x86_64-linux-gnu/libcrypto.so
src/libssh.so.4.2.0: src/CMakeFiles/ssh_shared.dir/build.make
src/libssh.so.4.2.0: src/CMakeFiles/ssh_shared.dir/link.txt

@$(CMAKE_COMMAND) -E cmake_echo_color --switch=$(COLOR) --red --bold "Linking C shared library libssh.so"

You can notice that during the build process, cmake would try to link some libraries under my system path /usr/lib/x86_64-linux-gnu/. And go to check yours.