libguile-ssh: Bugfix: Check if smobs are already freed

* libguile-ssh/message-type.c (free_message): Bugfix: Check if the smob is
  already freed, don't try to free it once more.
* libguile-ssh/server-type.c (free_server): Likewise.
* libguile-ssh/session-type.c (free_session): Likewise.
* libguile-ssh/sftp-session-type.c (free_sftp_session): Likewise.

4 files changed, 20 insertions, 0 deletions

diff --git a/libguile-ssh/message-type.c b/libguile-ssh/message-type.c
index 83d32b1..46b91f1 100644
--- a/libguile-ssh/message-type.c
+++ b/libguile-ssh/message-type.c
@@ -41,6 +41,11 @@ mark_message (SCM message)
 size_t
 free_message (SCM message)
 {
+  if (! SCM_SMOB_PREDICATE (message_tag, message))
+    {
+      _ssh_log (SSH_LOG_FUNCTIONS, "free_message", "%s", "already freed");
+      return 0;
+    }
   struct message_data *msg_data = _scm_to_message_data (message);
   ssh_message_free (msg_data->message);
   return 0;
diff --git a/libguile-ssh/server-type.c b/libguile-ssh/server-type.c
index ed2402f..5bb5e2e 100644
--- a/libguile-ssh/server-type.c
+++ b/libguile-ssh/server-type.c
@@ -41,6 +41,11 @@ mark_server (SCM server)
 size_t
 free_server (SCM server)
 {
+  if (! SCM_SMOB_PREDICATE (server_tag, server))
+    {
+      _ssh_log (SSH_LOG_FUNCTIONS, "free_server", "%s", "already freed");
+      return 0;
+    }
   struct server_data *server_data = _scm_to_server_data (server);
   ssh_bind_free (server_data->bind);
   return 0;
diff --git a/libguile-ssh/session-type.c b/libguile-ssh/session-type.c
index f6d909f..a766329 100644
--- a/libguile-ssh/session-type.c
+++ b/libguile-ssh/session-type.c
@@ -41,6 +41,11 @@ mark_session (SCM session_smob)
 size_t
 free_session (SCM session_smob)
 {
+  if (! SCM_SMOB_PREDICATE (session_tag, session_smob))
+    {
+      _ssh_log (SSH_LOG_FUNCTIONS, "free_session", "%s", "already freed");
+      return 0;
+    }
   struct session_data *data = _scm_to_session_data (session_smob);
 
   ssh_disconnect (data->ssh_session);
diff --git a/libguile-ssh/sftp-session-type.c b/libguile-ssh/sftp-session-type.c
index c3260e3..ae59c57 100644
--- a/libguile-ssh/sftp-session-type.c
+++ b/libguile-ssh/sftp-session-type.c
@@ -42,6 +42,11 @@ mark_sftp_session (SCM sftp_session)
 static size_t
 free_sftp_session (SCM sftp_session)
 {
+  if (! SCM_SMOB_PREDICATE (sftp_session_tag, sftp_session))
+    {
+      _ssh_log (SSH_LOG_FUNCTIONS, "free_sftp_session", "%s", "already freed");
+      return 0;
+    }
   struct sftp_session_data *sftp_sd = _scm_to_sftp_session_data (sftp_session);
   sftp_free (sftp_sd->sftp_session);
   return 0;