[glib] Check that close_fn is not %NULL before calling (#578499)

[Alexander Larsson <alexl src gnome org>]

commit c20b8d4d53a4e90f0e822276f6fbd94d52ff3c85
Author: Alexander Larsson <alexl redhat com>
Date:   Wed May 20 13:37:55 2009 +0200

    Check that close_fn is not %NULL before calling (#578499)
    
    Some streams have no close function, so this caused a crash.
---
 gio/ginputstream.c  |   13 ++++++++-----
 gio/giostream.c     |   11 +++++++----
 gio/goutputstream.c |   18 +++++++++++-------
 3 files changed, 26 insertions(+), 16 deletions(-)

diff --git a/gio/ginputstream.c b/gio/ginputstream.c
index 3d95c8b..d3e2224 100644
--- a/gio/ginputstream.c
+++ b/gio/ginputstream.c
@@ -1165,13 +1165,16 @@ close_async_thread (GSimpleAsyncResult *res,
      cancellation, since we want to close things anyway, although
      possibly in a quick-n-dirty way. At least we never want to leak
      open handles */
-  
+
   class = G_INPUT_STREAM_GET_CLASS (object);
-  result = class->close_fn (G_INPUT_STREAM (object), cancellable, &error);
-  if (!result)
+  if (class->close_fn)
     {
-      g_simple_async_result_set_from_error (res, error);
-      g_error_free (error);
+      result = class->close_fn (G_INPUT_STREAM (object), cancellable, &error);
+      if (!result)
+	{
+	  g_simple_async_result_set_from_error (res, error);
+	  g_error_free (error);
+	}
     }
 }
 
diff --git a/gio/giostream.c b/gio/giostream.c
index 7669734..a79e099 100644
--- a/gio/giostream.c
+++ b/gio/giostream.c
@@ -569,11 +569,14 @@ close_async_thread (GSimpleAsyncResult *res,
      open handles */
 
   class = G_IO_STREAM_GET_CLASS (object);
-  result = class->close_fn (G_IO_STREAM (object), cancellable, &error);
-  if (!result)
+  if (class->close_fn)
     {
-      g_simple_async_result_set_from_error (res, error);
-      g_error_free (error);
+      result = class->close_fn (G_IO_STREAM (object), cancellable, &error);
+      if (!result)
+	{
+	  g_simple_async_result_set_from_error (res, error);
+	  g_error_free (error);
+	}
     }
 }
 
diff --git a/gio/goutputstream.c b/gio/goutputstream.c
index a040a51..9e2a875 100644
--- a/gio/goutputstream.c
+++ b/gio/goutputstream.c
@@ -456,13 +456,14 @@ g_output_stream_real_splice (GOutputStream             *stream,
   if (flags & G_OUTPUT_STREAM_SPLICE_CLOSE_TARGET)
     {
       /* But write errors on close are bad! */
-      if (!class->close_fn (stream, cancellable, error))
+      if (class->close_fn &&
+	  !class->close_fn (stream, cancellable, error))
 	res = FALSE;
     }
 
   if (res)
     return bytes_copied;
-  
+
   return -1;
 }
 
@@ -1307,13 +1308,16 @@ close_async_thread (GSimpleAsyncResult *res,
      cancellation, since we want to close things anyway, although
      possibly in a quick-n-dirty way. At least we never want to leak
      open handles */
-  
+
   class = G_OUTPUT_STREAM_GET_CLASS (object);
-  result = class->close_fn (G_OUTPUT_STREAM (object), cancellable, &error);
-  if (!result)
+  if (class->close_fn)
     {
-      g_simple_async_result_set_from_error (res, error);
-      g_error_free (error);
+      result = class->close_fn (G_OUTPUT_STREAM (object), cancellable, &error);
+      if (!result)
+	{
+	  g_simple_async_result_set_from_error (res, error);
+	  g_error_free (error);
+	}
     }
 }