add a test for file descriptors

verify new loader behaviour with minimise

libvips/conversion/sequential.c

@@ -195,6 +195,11 @@ vips_sequential_build( VipsObject *object )
 	if( vips_linecache( sequential->in, &t, 
 		"tile_height", sequential->tile_height,
 		"access", VIPS_ACCESS_SEQUENTIAL,
+		/* We need seq caches to persist across minimise, in case
+		 * someone is trying to read an image with a series of crop
+		 * operations.
+		 */
+		"persistent", TRUE,
 		NULL ) )
 		return( -1 );
 

libvips/foreign/jpeg2vips.c

@@ -134,9 +134,9 @@
  */
 
 /*
+ */
 #define DEBUG_VERBOSE
 #define DEBUG
- */
 
 #ifdef HAVE_CONFIG_H
 #include <config.h>
@@ -472,7 +472,8 @@ attach_blob( VipsImage *im, const char *field, void *data, size_t data_length )
 	}
 
 #ifdef DEBUG
-	printf( "attach_blob: attaching %d bytes of %s\n", data_length, field );
+	printf( "attach_blob: attaching %zd bytes of %s\n", 
+		data_length, field );
 #endif /*DEBUG*/
 
 	vips_image_set_blob_copy( im, field, data, data_length );

test/test_descriptors.c

@@ -0,0 +1,91 @@
+/* Read an image and check that file handles are being closed on minimise.
+ *
+ * This will only work on linux: we signal success and do nothing if /dev/proc
+ * does not exist.
+ */
+
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <vips/vips.h>
+
+/* Count the number of files in a directory, -1 for directory not found etc.
+ */
+static int
+count_files( const char *dirname )
+{
+	GDir *dir;
+	int n;
+
+	if( !(dir = g_dir_open( dirname, 0, NULL )) )
+		return( -1 );
+
+	for( n = 0; g_dir_read_name( dir ); n++ )
+		;
+
+	g_dir_close( dir );
+
+	return( n );
+}
+
+int
+main( int argc, char **argv )
+{
+	VipsImage *image, *x;
+	char fd_dir[256];
+	int n_files;
+	double average;
+
+        if( VIPS_INIT( argv[0] ) )
+                vips_error_exit( "unable to start" ); 
+
+	vips_snprintf( fd_dir, 256, "/proc/%d/fd", getpid() );
+	n_files = count_files( fd_dir );
+	if( n_files == -1 )
+		/* Probably not linux, silent success.
+		 */
+		return( 0 );
+
+	/* This is usually 4. stdout / stdin / stderr plus one more made for
+	 * us by glib, I think, doing what I don't know.
+	 */
+
+	/* Opening an image should read the header, then close the fd.
+	 */
+	if( !(image = vips_image_new_from_file( argv[1], 
+		"access", VIPS_ACCESS_SEQUENTIAL,
+		NULL )) )
+		vips_error_exit( NULL );
+	if( count_files( fd_dir ) != n_files )
+		vips_error_exit( "fd not closed after header read" );
+
+	/* We should be able to read a chunk near the top, then have the fd
+	 * closed again.
+	 */
+	if( vips_crop( image, &x, 0, 0, image->Xsize, 10, NULL ) ||
+		vips_avg( x, &average, NULL ) )
+		vips_error_exit( NULL );
+	g_object_unref( x );
+	if( count_files( fd_dir ) != n_files )
+		vips_error_exit( "fd not closed after first read" );
+
+	/* We should be able to read again, a little further down, and have
+	 * the input restarted and closed again.
+	 */
+	if( vips_crop( image, &x, 0, 20, image->Xsize, 10, NULL ) ||
+		vips_avg( x, &average, NULL ) )
+		vips_error_exit( NULL );
+	g_object_unref( x );
+	if( count_files( fd_dir ) != n_files )
+		vips_error_exit( "fd not closed after second read" );
+
+	/* Clean up, and we should still just have three open.
+	 */
+	g_object_unref( x );
+	vips_shutdown();
+
+	if( count_files( fd_dir ) != n_files )
+		vips_error_exit( "fd not closed after shutdown" );
+
+	return( 0 );
+}