RE: static cross-compiling

[Jeremy Cross <JCross@xxxxxxxxxx>]

Your output indicates that you are missing symbols during the linking. The symbol names (like BN_new) are from OpenSSL, which would indicate that you are not properly including OpenSSL libraries in your linking. Depending on your configuration there may be other libraries you also need to be linking in...

-----Original Message-----
From: Thomas Käfer [mailto:kaefert@xxxxxxxxx] 
Sent: Thursday, September 21, 2017 1:25 PM
To: libssh@xxxxxxxxxx
Subject: Re: static cross-compiling

I'm sorry, I forgot to mention that I did read http://api.libssh.org/master/libssh_linking.html and tried to put "#define LIBSSH_STATIC 1" and "#define LIBSSH_STATIC" before my include libssh line but it didn't seem to make a difference..?

Ah. okey. I've found this link now:
https://stackoverflow.com/questions/21083052/cross-compiling-for-arm-while-linking-to-libssh-libssh-so-file-not-recognized

So if that's correct I need to cross-compile libssh and it's dependencies openssl and zlib for arm first, and can then using those prepared arm lib binaries compile a static build of my program. I will try to work on that next. Or have a look "embedded Linux distros like Buildroot, OpenEmbedded or Embedded Debian Project" to see if I find ready made arm binaries I can use?

2017-09-21 19:06 GMT+02:00 Thomas Käfer <kaefert@xxxxxxxxx>:
> Hello!
>
> I would like to write a program that I can cross-compile for Android 
> and OpenWRT devices, that uses libssh to first talk to ssh servers and 
> in a later development-stage to each other.
>
> Sadly, I'm not really too experienced in programming C / C++, so 
> please bear with me.
>
> I found this tutorial
> http://jensd.be/800/linux/cross-compiling-for-arm-with-ubuntu-16-04-lt
> s which with the additional install of the package "libc6-armel-cross"
> enabled me to cross-compile a program that prints "hello world" in a 
> shell on my android device.
>
> Next step: After installing the package "libssh-dev" I was able to use 
> sample code from 
> http://api.libssh.org/master/libssh_tutor_guided_tour.html
> to compile a dynamically linked program that works on my Linux laptop.
>
> Now the step I have been struggling with for the last few hours is to 
> compile this sample program that uses libssh in a static manner (and 
> once that is accomplished doing so using the "arm-linux-gnueabi-gcc"
> cross-compiler)
>
> So I tried:
> $ gcc sshtest.c -static -lssh
> /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/libssh.a(misc.c.o):
> In function `ssh_path_expand_tilde':
> (.text+0x87d): warning: Using 'getpwnam' in statically linked 
> applications requires at runtime the shared libraries from the glibc 
> version used for linking
> /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/libssh.a(misc.c.o):
> In function `ssh_get_user_home_dir':
> (.text+0x3a): warning: Using 'getpwuid_r' in statically linked 
> applications requires at runtime the shared libraries from the glibc 
> version used for linking ...
> /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/libssh.a(gssapi.c.o):
> In function `ssh_packet_userauth_gssapi_token_client':
> (.text+0x1b36): undefined reference to `gss_init_sec_context'
> /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/libssh.a(gssapi.c.o):
> In function `ssh_packet_userauth_gssapi_token_client':
> (.text+0x1c20): undefined reference to `gss_get_mic'
> collect2: error: ld returned 1 exit status
>
> Then I downloaded the libssh source package and made a static build of 
> the library using the ccmake gui to set the static parameter to true.
> With this I tried:
> $ gcc sshtest.c libssh-0.7.5/build/src/libssh.a -lssh
> libssh-0.7.5/build/src/libssh.a(curve25519.c.o): In function
> `ssh_curve25519_build_k':
> curve25519.c:(.text+0x13a): undefined reference to `BN_new'
> curve25519.c:(.text+0x1e9): undefined reference to `BN_bin2bn'
> libssh-0.7.5/build/src/libssh.a(dh.c.o): In function `ssh_get_random':
> ...
> libssh-0.7.5/build/src/libssh.a(bignum.c.o): In function `ssh_print_bignum':
> bignum.c:(.text+0x175): undefined reference to `BN_bn2hex'
> bignum.c:(.text+0x1dc): undefined reference to `CRYPTO_free'
> collect2: error: ld returned 1 exit status
>
>
> Now I'm out of ideas or in other words my googling skills are not 
> sufficient to find new ones ;) Please help..
> Kind regards,
> Thomas K.