fix a ref leak in the C++ API

see https://github.com/jcupitt/libvips/issues/290

thanks huskier

added a write-to-buffer example as well

ChangeLog

@@ -1,3 +1,7 @@
+4/5/15 started 8.0.2
+- fix a refcount error in C++ wrapper, thanks huskier
+- reomve a couple of stray header decls, thanks benjamin
+
 25/4/15 started 8.0.1
 - fix some compiler warnings 
 - work around a glib bug that can cause segv under load

cplusplus/VImage.cpp

@@ -442,8 +442,9 @@ VOption::get_operation( VipsOperation *operation )
 					(*((*i)->vvector))[j] = array[j];
 			}
 			else if( type == VIPS_TYPE_BLOB ) {
+				// our caller gets a reference
 				*((*i)->vblob) = 
-					(VipsBlob *) g_value_get_boxed( value );
+					(VipsBlob *) g_value_dup_boxed( value );
 			}
 		}
 }
@@ -504,7 +505,7 @@ VImage::call_option_string( const char *operation_name,
 }
 
 void 
-	VImage::call( const char *operation_name, VOption *options ) 
+VImage::call( const char *operation_name, VOption *options ) 
 	throw( VError )
 {
 	call_option_string( operation_name, NULL, options ); 

cplusplus/examples/buffer.cpp

@@ -0,0 +1,61 @@
+/* 
+ * compile with:
+ *
+ *      g++ -g -Wall buffer.cpp `pkg-config vips-cpp --cflags --libs`
+ *
+ */
+
+#define DEBUG
+
+#include <vips/vips8>
+
+using namespace vips;
+
+int
+main( int argc, char **argv )
+{
+	GOptionContext *context;
+	GOptionGroup *main_group;
+	GError *error = NULL;
+
+	if( VIPS_INIT( argv[0] ) )
+		vips_error_exit( NULL ); 
+
+	context = g_option_context_new( "" ); 
+
+	main_group = g_option_group_new( NULL, NULL, NULL, NULL, NULL );
+	g_option_context_set_main_group( context, main_group );
+	g_option_context_add_group( context, vips_get_option_group() );
+
+	if( !g_option_context_parse( context, &argc, &argv, &error ) ) {
+		if( error ) {
+			fprintf( stderr, "%s\n", error->message );
+			g_error_free( error );
+		}
+
+		vips_error_exit( NULL );
+	}
+
+	// load an image from a file
+	VImage im = VImage::new_from_file( argv[1], 
+		VImage::option()->set( "access", "sequential-unbuffered" ) ); 
+	printf( "loaded %d x %d pixel image from %s\n", 
+		im.width(), im.height(), argv[1] ); 
+
+	// write to a formatted memory buffer
+	size_t size;
+	void *buf;
+	im.write_to_buffer( ".png", &buf, &size );
+	printf( "written to memory %p in png format, %zd bytes\n", buf, size );
+
+	// load from the formatted memory area
+	im = VImage::new_from_buffer( buf, size, "" );
+	printf( "loaded from memory, %d x %d pixel image\n", 
+		im.width(), im.height() ); 
+
+	// write back to a file
+	im.write_to_file( argv[2] );
+	printf( "written back to  %s\n", argv[2] ); 
+
+        return( 0 );
+}