[libgda/LIBGDA_5.2] gda-pstmt: using GWeakRef to handle its weak references

[Daniel Espinosa Ortiz <despinosa src gnome org>]

commit e960ed35e6d59a7a0e095c903c152a762da30d85
Author: Daniel Espinosa <esodan gmail com>
Date:   Wed Sep 26 18:32:42 2018 -0500

    gda-pstmt: using GWeakRef to handle its weak references

 libgda/providers-support/gda-pstmt.c | 88 +++++++++++++++++++++++++++---------
 1 file changed, 67 insertions(+), 21 deletions(-)
---
diff --git a/libgda/providers-support/gda-pstmt.c b/libgda/providers-support/gda-pstmt.c
index 0c43c3b14..356c5cb53 100644
--- a/libgda/providers-support/gda-pstmt.c
+++ b/libgda/providers-support/gda-pstmt.c
@@ -1,7 +1,8 @@
 /*
- * Copyright (C) 2008 - 2011 Vivien Malerba <malerba gnome-db org>
+ * Copyright (C) 2008 - 2015 Vivien Malerba <malerba gnome-db org>
  * Copyright (C) 2010 David King <davidk openismus com>
  * Copyright (C) 2010 Jonh Wendell <jwendell gnome org>
+ * Copyright (C) 2018 Daniel Espinosa <esodan gmail com>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -32,7 +33,8 @@ static void gda_pstmt_finalize   (GObject *object);
 static GObjectClass *parent_class = NULL;
 
 struct _GdaPStmtPrivate {
-       GdaStatement *gda_stmt; /* GdaPStmt object holds a weak reference on this stmt object, may be NULL */
+       GRecMutex mutex;
+       GWeakRef gda_stmt_ref; /* holds a weak reference to #GdaStatement, or %NULL */
 };
 
 /**
@@ -84,7 +86,8 @@ gda_pstmt_init (GdaPStmt *pstmt, G_GNUC_UNUSED GdaPStmtClass *klass)
 {
        g_return_if_fail (GDA_IS_PSTMT (pstmt));
        pstmt->priv = g_new0 (GdaPStmtPrivate, 1);
-       pstmt->priv->gda_stmt = NULL;
+       g_rec_mutex_init (& pstmt->priv->mutex);
+       g_weak_ref_init (&pstmt->priv->gda_stmt_ref, NULL);
        pstmt->sql = NULL;
        pstmt->param_ids = NULL;
        pstmt->ncols = -1;
@@ -92,13 +95,30 @@ gda_pstmt_init (GdaPStmt *pstmt, G_GNUC_UNUSED GdaPStmtClass *klass)
        pstmt->tmpl_columns = NULL;
 }
 
+/*
+ * @stmt may be %NULL
+ */
 static void
 gda_stmt_reset_cb (GdaStatement *stmt, GdaPStmt *pstmt)
 {
-       g_signal_handlers_disconnect_by_func (G_OBJECT (stmt), 
-                                             G_CALLBACK (gda_stmt_reset_cb), pstmt);
-       g_object_remove_weak_pointer ((GObject*) pstmt->priv->gda_stmt, (gpointer*) &(pstmt->priv->gda_stmt));
-       pstmt->priv->gda_stmt = NULL;
+       g_rec_mutex_lock (& pstmt->priv->mutex);
+       if (stmt) {
+               g_object_ref (stmt);
+               g_signal_handlers_disconnect_by_func (G_OBJECT (stmt),
+                                                     G_CALLBACK (gda_stmt_reset_cb), pstmt);
+               g_object_unref (stmt);
+       }
+       else {
+               GdaStatement *stm = g_weak_ref_get (& pstmt->priv->gda_stmt_ref);
+               if (stm) {
+                       g_signal_handlers_disconnect_by_func (G_OBJECT (stm),
+                                                             G_CALLBACK (gda_stmt_reset_cb), pstmt);
+                       g_object_unref (stm);
+               }
+       }
+
+       g_weak_ref_set (& pstmt->priv->gda_stmt_ref, NULL);
+       g_rec_mutex_unlock (& pstmt->priv->mutex);
 }
 
 static void
@@ -106,8 +126,7 @@ gda_pstmt_dispose (GObject *object)
 {
        GdaPStmt *pstmt = (GdaPStmt *) object;
 
-       if (pstmt->priv->gda_stmt) 
-               gda_stmt_reset_cb (pstmt->priv->gda_stmt, pstmt);
+       gda_stmt_reset_cb (NULL, pstmt);
 
        /* chain to parent class */
        parent_class->dispose (object);
@@ -119,6 +138,8 @@ gda_pstmt_finalize (GObject *object)
        GdaPStmt *pstmt = (GdaPStmt *) object;
 
        /* free memory */
+       g_rec_mutex_clear (& pstmt->priv->mutex);
+       g_weak_ref_clear (&pstmt->priv->gda_stmt_ref);
        g_free (pstmt->priv);
 
        if (pstmt->sql) {
@@ -146,7 +167,7 @@ gda_pstmt_finalize (GObject *object)
 /**
  * gda_pstmt_set_gda_statement:
  * @pstmt: a #GdaPStmt object
- * @stmt: a #GdaStatement object
+ * @stmt: (allow-none): a #GdaStatement object, or %NULL
  *
  * Informs @pstmt that it corresponds to the preparation of the @stmt statement
  */
@@ -156,16 +177,24 @@ gda_pstmt_set_gda_statement (GdaPStmt *pstmt, GdaStatement *stmt)
        g_return_if_fail (GDA_IS_PSTMT (pstmt));
        g_return_if_fail (!stmt || GDA_IS_STATEMENT (stmt));
 
-       if (pstmt->priv->gda_stmt == stmt)
-               return;
-       if (pstmt->priv->gda_stmt) 
-               gda_stmt_reset_cb (pstmt->priv->gda_stmt, pstmt);
+       g_rec_mutex_lock (& pstmt->priv->mutex);
+       g_object_ref (stmt);
 
-       pstmt->priv->gda_stmt = stmt;
-       if (stmt) {
-               g_object_add_weak_pointer ((GObject*) stmt, (gpointer*) &(pstmt->priv->gda_stmt));
-               g_signal_connect (G_OBJECT (stmt), "reset", G_CALLBACK (gda_stmt_reset_cb), pstmt);
+       GdaStatement *estmt;
+       estmt = g_weak_ref_get (& pstmt->priv->gda_stmt_ref);
+       if (estmt == stmt) {
+               if (estmt)
+                       g_object_unref (estmt);
+               g_rec_mutex_unlock (& pstmt->priv->mutex);
+               return;
        }
+
+       gda_stmt_reset_cb (NULL, pstmt);
+
+       g_weak_ref_set (& pstmt->priv->gda_stmt_ref, stmt);
+       g_signal_connect (G_OBJECT (stmt), "reset", G_CALLBACK (gda_stmt_reset_cb), pstmt);
+       g_object_unref (stmt);
+       g_rec_mutex_unlock (& pstmt->priv->mutex);
 }
 
 /**
@@ -182,6 +211,9 @@ gda_pstmt_copy_contents (GdaPStmt *src, GdaPStmt *dest)
        g_return_if_fail (GDA_IS_PSTMT (src));
        g_return_if_fail (GDA_IS_PSTMT (dest));
 
+       g_rec_mutex_lock (& src->priv->mutex);
+       g_rec_mutex_lock (& dest->priv->mutex);
+
        g_free (dest->sql);
        dest->sql = NULL;
        if (src->sql)
@@ -207,8 +239,16 @@ gda_pstmt_copy_contents (GdaPStmt *src, GdaPStmt *dest)
                        dest->tmpl_columns = g_slist_append (dest->tmpl_columns, 
                                                             gda_column_copy (GDA_COLUMN (list->data)));
        }
-       if (src->priv->gda_stmt)
-               gda_pstmt_set_gda_statement (dest, src->priv->gda_stmt);
+       GdaStatement *stmt;
+       stmt = g_weak_ref_get (& src->priv->gda_stmt_ref);
+       if (stmt) {
+               gda_pstmt_set_gda_statement (dest, stmt);
+               g_object_unref (stmt);
+       }
+
+       g_rec_mutex_unlock (& src->priv->mutex);
+       g_rec_mutex_unlock (& dest->priv->mutex);
+
 }
 
 /**
@@ -226,5 +266,11 @@ GdaStatement *
 gda_pstmt_get_gda_statement (GdaPStmt *pstmt)
 {
        g_return_val_if_fail (GDA_IS_PSTMT (pstmt), NULL);
-       return pstmt->priv->gda_stmt;
+       g_rec_mutex_lock (& pstmt->priv->mutex);
+       GdaStatement *stmt;
+       stmt = g_weak_ref_get (& pstmt->priv->gda_stmt_ref);
+       if (stmt)
+               g_object_unref (stmt);
+       g_rec_mutex_unlock (& pstmt->priv->mutex);
+       return stmt;
 }