Re: permission denied in cygwin

[Christian Franke]

Hi,

on Wed, 10 Jan 2024 15:47:46 +0200, Zibri wrote:
> Hello!
> I am writing you to inform you that I compiled ddrescue-1.25, 1.26 and
> 1.27 under cygwin.
>
> For some reason, 1.25 works but 1.26 and 1.27 give "Permission denied" error:
> ddrescue: /dev/sdg1: Fatal error reading the input file: Permission denied
> this does not happen in version 1.25.
> What can I change to make it work?

"Thanks" to an USB flash drive with bad blocks, I found a Windows+Cygwin 
specific behavior which could further explain the above issue.

I added a workaround (attached) and uploaded a new Cygwin package 
ddrescue-1.28-2:
https://cygwin.com/packages/summary/ddrescue.html

See the package announcement for more details about the interesting 
behavior of Windows on read errors:
https://sourceware.org/pipermail/cygwin-announce/2024-February/011568.html


This leads to the following suggestion for a ddrescue enhancement to 
handle platform/controller/driver specific values of errno after read 
errors:

- If ddrescue is aborted due to a read error, also print the errno value 
(EACCES and EPERM may result in the same message text).

- Print the "Error of last failed read" with error text and errno value 
in a high verbosity level and possibly also as a comment in the map file.

- Add options --abort-on-errno=N and --continue-on-errno=N (or 
--no-abort-on-errno=N) to allow the user to override the hard coded 
decision whether ddrescue aborts after a read error or not.

--
Regards,
Christian

0001-Cygwin-Don-t-abort-read-on-EACCES.patch
Description: Text document