BUG#20479565: STD::STRING GTID_SET::ENCODE() IS NOT SAFE ON WINDOWS

Method encode() of Gtid_set class was returning a local variable of type
std::string, although this was working OK on all Posix platforms, on
Windows memory was being corrupted what was causing method to fail.

To fix the above issue, method std::string Gtid_set::encode() was
removed.

Author: nacarvalho

plugin/replication_observers_example/replication_observers_example.cc

@@ -512,10 +512,15 @@ int validate_plugin_server_requirements(Trans_param *param)
   if (tcle->is_valid())
   {
     Gtid_set *snapshot_version= tcle->get_snapshot_version();
+    size_t snapshot_version_len= snapshot_version->get_encoded_length();
+    uchar* snapshot_version_buf= (uchar *)my_malloc(PSI_NOT_INSTRUMENTED,
+                                                    snapshot_version_len, MYF(0));
+    snapshot_version->encode(snapshot_version_buf);
     my_plugin_log_message(&plugin_info_ptr,
                           MY_INFORMATION_LEVEL,
                           "snapshot version is '%s'",
-                          snapshot_version->encode().c_str());
+                          snapshot_version_buf);
+    my_free(snapshot_version_buf);
     success++;
   }
   else

sql/rpl_gtid.h

@@ -1676,10 +1676,6 @@ class Gtid_set
     Encodes this Gtid_set as a binary string.
   */
   void encode(uchar *buf) const;
-  /**
-    Encodes this Gtid_set as a binary string using std::string.
-  */
-  std::string encode() const;
   /**
     Returns the length of this Gtid_set when encoded using the
     encode() function.

sql/rpl_gtid_set.cc

@@ -1441,21 +1441,6 @@ void Gtid_set::encode(uchar *buf) const
 }
 
 
-std::string Gtid_set::encode() const
-{
-  DBUG_ENTER("std::string Gtid_set::encode()");
-
-  size_t len= get_encoded_length();
-  uchar* buf= (uchar *)my_malloc(key_memory_Gtid_set_to_string,
-                                 len, MYF(MY_WME));
-  encode(buf);
-  std::string result(reinterpret_cast<const char*>(buf), len);
-  my_free(buf);
-
-  DBUG_RETURN(result);
-}
-
-
 enum_return_status Gtid_set::add_gtid_encoding(const uchar *encoded,
                                                size_t length,
                                                size_t *actual_length)