[PATCH] Cygwin: Map ERROR_NO_SUCH_DEVICE and ERROR_MEDIA_CHANGED to ENODEV

[Christian Franke]

Experiments with damaged USB flash drives and ddrescue revealed that the 
current mapping of these Win32 errors to the fallback EACCES could be 
improved.

BTW: I wonder why EACCES was selected as the fallback. Source code 
control forensics suggest that this was decided in the last millennium. 
A related comment from CGF added August 2000 persists until today :-)
/* FIXME: what's so special about EACCESS? */

-- 
Regards,
Christian

-------------- next part --------------
From 8aa19c7fd13dc3790dc271dede8954539bffcd4d Mon Sep 17 00:00:00 2001
From: Christian Franke <christian.franke@t-online.de>
Date: Fri, 23 Feb 2024 19:01:09 +0100
Subject: [PATCH] Cygwin: Map ERROR_NO_SUCH_DEVICE and ERROR_MEDIA_CHANGED to
 ENODEV

If a removable (USB) device is disconnected after opening its raw
device, R/W attempts fail with ERROR_NO_SUCH_DEVICE(433).  If the
raw device of a partition is used, ERROR_MEDIA_CHANGED(1110) is
returned instead.  Both are mapped to ENODEV(19) because <errno.h>
does not offer a value which better matches ERROR_MEDIA_CHANGED.

Signed-off-by: Christian Franke <christian.franke@t-online.de>
---
 winsup/cygwin/local_includes/errmap.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/winsup/cygwin/local_includes/errmap.h b/winsup/cygwin/local_includes/errmap.h
index 326b35b6c..a0b3ff400 100644
--- a/winsup/cygwin/local_includes/errmap.h
+++ b/winsup/cygwin/local_includes/errmap.h
@@ -438,7 +438,7 @@ static const int errmap[] =
   0,			/* 430 */
   0,			/* 431 */
   0,			/* 432 */
-  0,			/* 433 */
+  ENODEV,		/* ERROR_NO_SUCH_DEVICE */
   0,			/* 434 */
   0,			/* 435 */
   0,			/* 436 */
@@ -1115,7 +1115,7 @@ static const int errmap[] =
   0,			/* ERROR_DEVICE_NOT_PARTITIONED */
   0,			/* ERROR_UNABLE_TO_LOCK_MEDIA */
   0,			/* ERROR_UNABLE_TO_UNLOAD_MEDIA */
-  0,			/* ERROR_MEDIA_CHANGED */
+  ENODEV,		/* ERROR_MEDIA_CHANGED */
   EIO,			/* ERROR_BUS_RESET */
   ENOMEDIUM,		/* ERROR_NO_MEDIA_IN_DRIVE */
   0,			/* ERROR_NO_UNICODE_TRANSLATION */
-- 
2.43.0