link libssh with static library (libssh.a)


link libssh with static library (libssh.a)



I was trying to link my program with libssh static library.



Following is my simple code copied from libssh tutorial:


//sshtest.c
#define LIBSSH_STATIC 1
#include <libssh/libssh.h>
#include <stdlib.h>

int main()
{
ssh_session my_ssh_session;
my_ssh_session = ssh_new();
if (my_ssh_session == NULL)
exit(-1);

ssh_free(my_ssh_session);
}



I put library file libssh.a into the subdirectory libs/


libssh.a


libs/



Then compile it with command gcc sshtest.c -Llibs -lssh -o sshtest


gcc sshtest.c -Llibs -lssh -o sshtest



The output is bunch of undefined reference errors like:


libs/libssh.a(wrapper.c.o): In function `crypto_free':
/home/gg/libssh/src/wrapper.c:156: undefined reference to `BN_clear_free'
/home/gg/libssh/src/wrapper.c:157: undefined reference to `BN_clear_free'
libs/libssh.a(libcrypto.c.o): In function `ssh_reseed':
/home/gg/libssh/src/libcrypto.c:77: undefined reference to `RAND_add'
libs/libssh.a(libcrypto.c.o): In function `sha1_init':
/home/gg/libssh/src/libcrypto.c:84: undefined reference to `EVP_MD_CTX_new'



The problem can be fixed by copying dynamic library files (libssh.so, libssh.so.4, libssh.so.4.5.0) into the libs/ folder, but I guess the compiler will link with dynamic library in this case.


libssh.so, libssh.so.4, libssh.so.4.5.0


libs/



Can somebody tell me the proper way to link libssh static library? Thank you !!



Something extra (optional):



Actually, I was trying to build an ssh server application using includeOS, I try to link dynamic library with it by adding target_link_libraries into the cmakelist.txt, and I got an error usr/bin/ld unrecognized option "-Wl,-rpath,path_to_my_sshlib"when I make it. I guess may be unikernel can not support dynamic linking, because includeOS only has one static libray path variable in cmakelist


target_link_libraries


cmakelist.txt


usr/bin/ld unrecognized option "-Wl,-rpath,path_to_my_sshlib"


make



----------------------Edit--------------------------------



One of the error message:


`/home/gavin/libssh/src/wrapper.c:156: undefined reference to `BN_clear_free'`



wrapper.c, line 156:


bignum_free(crypto->e);



it was defined in libssh/libcrypto.h which included by wrapper.h


libssh/libcrypto.h


wrapper.h



libcrypto.h line 70:


#define bignum_free(num) BN_clear_free(num)



And I notice that void BN_clear_free(BIGNUM *a); is a function defined in openssl library


void BN_clear_free(BIGNUM *a);



Could introducing another library cause the problem?
if so, how could I fix it?
why dynamic linking dose not have this issue?





Try gcc sshtest.c -Llibs -lssh -static -o sshtest, Or gcc sshtest.c libs/libssh.a -o sshtest.
– Joy Allen
Jun 28 at 7:08


gcc sshtest.c -Llibs -lssh -static -o sshtest


gcc sshtest.c libs/libssh.a -o sshtest





@joyallen , both of them result to the same error, do you have any idea why the error generated at the path of my cloned repository? thank you
– NoobieG
Jun 28 at 16:01










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