[glom] ConnectionPool: Use std::shared_ptr<> for m_instance.

[Murray Cumming <murrayc src gnome org>]

commit b1f81a53236c3056c2de13cce95d923aa3b5abab
Author: Murray Cumming <murrayc murrayc com>
Date:   Thu Feb 4 22:35:32 2016 +0100

    ConnectionPool: Use std::shared_ptr<> for m_instance.

 glom/libglom/connectionpool.cc |    9 ++++-----
 glom/libglom/connectionpool.h  |   16 ++++++++++------
 2 files changed, 14 insertions(+), 11 deletions(-)
---
diff --git a/glom/libglom/connectionpool.cc b/glom/libglom/connectionpool.cc
index 2dc2ade..f78bf28 100644
--- a/glom/libglom/connectionpool.cc
+++ b/glom/libglom/connectionpool.cc
@@ -104,7 +104,7 @@ void SharedConnection::close()
 }
 
 //init_db_details static data:
-ConnectionPool* ConnectionPool::m_instance = nullptr;
+std::shared_ptr<ConnectionPool> ConnectionPool::m_instance;
 
 ConnectionPool::ConnectionPool()
 :
@@ -127,14 +127,14 @@ ConnectionPool::~ConnectionPool()
 }
 
 //static
-ConnectionPool* ConnectionPool::get_instance()
+std::shared_ptr<ConnectionPool> ConnectionPool::get_instance()
 {
   //TODO: Synchronize this for threads?
   if(m_instance)
     return m_instance;
   else
   {
-    m_instance = new ConnectionPool();
+    m_instance = std::make_shared<ConnectionPool>();
     return m_instance;
   }
 }
@@ -199,8 +199,7 @@ void ConnectionPool::setup_from_document(const std::shared_ptr<const Document>&
 
 void ConnectionPool::delete_instance()
 {
-  delete m_instance;
-  m_instance = nullptr;
+  m_instance.reset();
 }
 
 bool ConnectionPool::get_ready_to_connect() const
diff --git a/glom/libglom/connectionpool.h b/glom/libglom/connectionpool.h
index 2c45c52..3835fc9 100644
--- a/glom/libglom/connectionpool.h
+++ b/glom/libglom/connectionpool.h
@@ -85,23 +85,27 @@ class Document;
 class ConnectionPool : public sigc::trackable
 {
 private:
+
+
+public:
+
+  //These are public for use by std::make_shared<>().
+  //TODO: Does this need to be virtual?
   ConnectionPool();
+  virtual ~ConnectionPool();
+
   ConnectionPool(const ConnectionPool& src) = delete;
   ConnectionPool(ConnectionPool&& src) = delete;
   ConnectionPool& operator=(const ConnectionPool& src) = delete;
   ConnectionPool& operator=(ConnectionPool&& src) = delete;
 
-  virtual ~ConnectionPool();
-  //ConnectionPool& operator=(const ConnectionPool& src);
-
-public:
   typedef ConnectionPoolBackends::Backend Backend;
   typedef Backend::type_vec_const_fields type_vec_const_fields;
 
   /** Get the singleton instance.
    * Use delete_instance() when the program quits.
    */
-  static ConnectionPool* get_instance();
+  static std::shared_ptr<ConnectionPool> get_instance();
   
   /** Whether the connection is ready to be used.
    */ 
@@ -348,7 +352,7 @@ private:
 
 private:
 
-  static ConnectionPool* m_instance;
+  static std::shared_ptr<ConnectionPool> m_instance;
   SlotGetDocument m_slot_get_document;
 
   type_void_slot m_epc_slot_begin, m_epc_slot_progress, m_epc_slot_done;