On Wednesday, 14 August 2019 14:15:25 CEST Philippe Mathieu-Daudé wrote:
> The libssh packaged by a distribution can predate version 0.8,
> but still provides the newer API introduced after version 0.7.
> 
> Using the deprecated API leads to build failure, as on Ubuntu 18.04:
> 
>     CC      block/ssh.o
>   block/ssh.c: In function 'check_host_key_hash':
>   block/ssh.c:444:5: error: 'ssh_get_publickey' is deprecated [-Werror=deprecated-declarations]
>        r = ssh_get_publickey(s->session, &pubkey);
>        ^
>   In file included from block/ssh.c:27:0:
>   /usr/include/libssh/libssh.h:489:31: note: declared here
>    SSH_DEPRECATED LIBSSH_API int ssh_get_publickey(ssh_session session, ssh_key *key);
>                                  ^~~~~~~~~~~~~~~~~
>   rules.mak:69: recipe for target 'block/ssh.o' failed
>   make: *** [block/ssh.o] Error 1
> 
> Fix by using the newer API if available.
> 
> Suggested-by: Andrea Bolognani <abologna@redhat.com>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>  block/ssh.c | 2 +-
>  configure   | 7 +++++++
>  2 files changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/block/ssh.c b/block/ssh.c
> index 501933b855..f5fea921c6 100644
> --- a/block/ssh.c
> +++ b/block/ssh.c
> @@ -438,7 +438,7 @@ check_host_key_hash(BDRVSSHState *s, const char *hash,
>      unsigned char *server_hash;
>      size_t server_hash_len;
>  
> -#ifdef HAVE_LIBSSH_0_8
> +#ifdef HAVE_SSH_GET_SERVER_PUBLICKEY
>      r = ssh_get_server_publickey(s->session, &pubkey);
>  #else
>      r = ssh_get_publickey(s->session, &pubkey);
> diff --git a/configure b/configure
> index 1d5c07de1f..fe3fef9309 100755
> --- a/configure
> +++ b/configure
> @@ -3949,11 +3949,18 @@ fi
>  if test "$libssh" = "yes"; then
>    cat > $TMPC <<EOF
>  #include <libssh/libssh.h>
> +#ifdef HAVE_SSH_GET_SERVER_PUBLICKEY
>  int main(void) { return ssh_get_server_publickey(NULL, NULL); }
> +#else
> +int main(void) { return ssh_get_publickey(NULL, NULL); }
> +#endif
>  EOF
>    if compile_object "$libssh_cflags"; then
>      libssh_cflags="-DHAVE_LIBSSH_0_8 $libssh_cflags"
>    fi
> +  if compile_object "$libssh_cflags -DHAVE_SSH_GET_SERVER_PUBLICKEY"; then
> +    libssh_cflags="-DHAVE_SSH_GET_SERVER_PUBLICKEY $libssh_cflags"
> +  fi

Why try to compile it twice? If the check for ssh_get_server_publickey
works, then it is available...

Just add an additional HAVE_SSH_GET_SERVER_PUBLICKEY define when this
test succeeds, and change the usage of ssh_get_server_publickey based
on this.

-- 
Pino Toscano