Re: Regression (last snapshot)

[Corinna Vinschen <corinna-cygwin@cygwin.com>]

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On Jul 22 17:20, Corinna Vinschen wrote:
> On Jul 22 13:44, Ken Brown wrote:
> > On 7/22/2019 8:23 AM, Ken Brown wrote:
> > > On 7/20/2019 6:55 PM, Houder wrote:
> > >> 64-@@ uname -a
> > >> CYGWIN_NT-6.1 Seven 3.1.0s(0.339/5/3) 2019-07-12 15:28 x86_64 Cygwin
> > >>
> > >> 64-@@ ls -lL <(grep bash .bashrc)
> > >> ls: /dev/fd/63: No such file or directory
> > >> pr-------- 1 Henri None 0 Jul 21 00:41 /dev/fd/63
> > > 
> > > Thanks for the report.  This is probably caused by my new FIFO code.  I'm
> > > looking into it.
> > 
> > Actually, a bisection shows that the regression is due to the following commit:
> > 
> > commit 2607639992f6600135532831c8357c10cb248821
> > Author: Erik M. Bray <erik.m.bray@gmail.com>
> > Date:   Wed Apr 10 17:05:22 2019 +0200
> > 
> >      Improve error handling in /proc/[pid]/ virtual files.
> > 
> >      * Changes error handling to allow /proc/[pid]/ virtual files to be
> >        empty in some cases (in this case the file's formatter should return
> >        -1 upon error, not 0).
> > 
> >      * Better error handling of /proc/[pid]/stat for zombie processes:
> >        previously trying to open this file on zombie processes resulted
> >        in an EINVAL being returned by open().  Now the file can be read,
> >        and fields that can no longer be read are just zeroed.
> > 
> >      * Similarly for /proc/[pid]/statm for zombie processes.
> > 
> >      * Similarly for /proc/[pid]/maps for zombie processes (in this case the
> >        file can be read but is zero-length, which is consistent with observed
> >        behavior on Linux.
> > 
> > 
> > Erik, can you take a look?
> 
> I have a hunch.  It's this change:
> 
> @@ -355,7 +355,7 @@ fhandler_process::fill_filebuf ()
>         }
>        else
>         filesize = process_tab[fileid].format_func (p, filebuf);
> -      return !filesize ? false : true;
> +      return filesize < 0 ? false : true;
>      }
>    return false;
>  }
> 
> The formatter for /proc/PID/fd, format_process_fd, returns *valid*
> negative values.  But the above patch treats all negative values as
> error now.
> 
> The fact that format_process_fd returns negative values has historical
> reasons.  Negative values of type virtual_ftype_t are files, positive
> values are directories.
> 
> One way to fix this is to change this to all positive values.  At a
> first glance I don't see any check for an explicit negative
> virtual_ftype_t value, especially not in the only consumer
> path_conv::check in path.cc, and the simple numbers have long been
> replaced with enum values.

A second glance shows a few problems in the code...


Corinna

-- 
Corinna Vinschen
Cygwin Maintainer

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