From 89c6d290799428717256d663d9e5fc25eb192a9e Mon Sep 17 00:00:00 2001
From: John Cupitt <jcupitt@gmail.com>
Date: Mon, 5 Nov 2018 10:38:15 +0000
Subject: [PATCH] add comments re. temp file open bug

---
 libvips/iofuncs/image.c |  8 ++++----
 libvips/iofuncs/vips.c  | 13 ++++++++-----
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/libvips/iofuncs/image.c b/libvips/iofuncs/image.c
index e4489778..99893a11 100644
--- a/libvips/iofuncs/image.c
+++ b/libvips/iofuncs/image.c
@@ -3077,13 +3077,13 @@ vips_image_rewind_output( VipsImage *image )
 	/* Now we've finished writing and reopened as read, we can
 	 * delete-on-close. 
 	 *
-	 * On *nix-like systems, this will unlink the file
-	 * from the filesystem and when we exit, for whatever reason, the file
+	 * On *nix-like systems, this will unlink the file from the 
+	 * filesystem and when we exit, for whatever reason, the file
 	 * we be reclaimed. 
 	 *
 	 * On Windows this will fail because the file is open and you can't
-	 * delete open files. However, on Windows we set O_TEMP, so the file
-	 * will be deleted when the fd is finally closed.
+	 * delete open files. However, on Windows we set _O_TEMPORARY, so the 
+	 * file will be deleted when the fd is finally closed.
 	 */
 	vips_image_delete( image );
 
diff --git a/libvips/iofuncs/vips.c b/libvips/iofuncs/vips.c
index 2c59f807..e7d71378 100644
--- a/libvips/iofuncs/vips.c
+++ b/libvips/iofuncs/vips.c
@@ -137,7 +137,6 @@
  *
  * We use O_RDWR not O_WRONLY since after writing we may want to rewind the 
  * image and read from it.
- *
  */
 #define MODE_WRITE BINARYIZE (O_RDWR | O_CREAT | O_TRUNC)
 
@@ -187,12 +186,15 @@ vips__open_image_write( const char *filename, gboolean temp )
 	int flags;
 	int fd;
 
-	flags = MODE_WRITE;
 	fd = -1;
 
 #ifdef O_TMPFILE
 	/* Linux-only extension creates an unlinked file. CREAT and TRUNC must
 	 * be clear. The filename arg to open() must name a directory.
+	 *
+	 * This can fail since not all filesystems support it. In this case,
+	 * we open as a regular file and rely on the delete-on-close
+	 * mechanism, see vips_image_delete(). 
 	 */
 	if( temp ) {
 		char *dirname;
@@ -203,10 +205,11 @@ vips__open_image_write( const char *filename, gboolean temp )
 	}
 #endif /*O_TMPFILE*/
 
+	flags = MODE_WRITE;
+
 #ifdef _O_TEMPORARY
-	/* On Windows, setting _O_TEMPORARY gets the file automatically
-	 * deleted on process exit, even if the processes crashes. See
-	 * vips_image_rewind() for what we do to help on *nix.
+	/* On Windows, setting _O_TEMPORARY will delete the file automatically
+	 * on process exit, even if the processes crashes. 
 	 */
 	if( temp )
 		flags |= _O_TEMPORARY;