[Qemu-devel] [PATCH 3/4] configure: Improve checking libssh version is 0.8

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

To figure out which libssh version is installed, checking for
ssh_get_server_publickey() is not sufficient.

ssh_get_server_publickey() has been introduced in libssh
commit bbd052202 (predating 0.8) but distributions also
backported other pre-0.8 patches, such libssh commit
963c46e4f which introduce the ssh_known_hosts_e enum.

Check the enum is available to assume the version is 0.8.

This fixes build failure on Ubuntu 18.04:

    CC      block/ssh.o
  block/ssh.c: In function 'check_host_key_knownhosts':
  block/ssh.c:281:28: error: storage size of 'state' isn't known
       enum ssh_known_hosts_e state;
                              ^~~~~
  rules.mak:69: recipe for target 'block/ssh.o' failed
  make: *** [block/ssh.o] Error 1

Reported-by: 周文青 <1151451036@qq.com>
Fixes: https://bugs.launchpad.net/qemu/+bug/1838763
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 configure | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/configure b/configure
index fe3fef9309..040aa8eb6c 100755
--- a/configure
+++ b/configure
@@ -3949,18 +3949,24 @@ fi
 if test "$libssh" = "yes"; then
   cat > $TMPC <<EOF
 #include <libssh/libssh.h>
+#ifdef HAVE_LIBSSH_0_8
+static const enum ssh_known_hosts_e val = SSH_KNOWN_HOSTS_OK;
+#endif
 #ifdef HAVE_SSH_GET_SERVER_PUBLICKEY
 int main(void) { return ssh_get_server_publickey(NULL, NULL); }
 #else
 int main(void) { return ssh_get_publickey(NULL, NULL); }
 #endif
 EOF
-  if compile_object "$libssh_cflags"; then
+  if compile_object "$libssh_cflags -DHAVE_LIBSSH_0_8"; 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 $libssh_cflags"
   fi
+  if ! compile_object "$libssh_cflags"; then
+    error_exit "cannot use with libssh (is it broken?)"
+  fi
 fi
 
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-- 
2.20.1