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In-Reply-To: <76a478c7-fabe-b8e9-581e-9ffcc08f53ed@cornell.edu>
Date: Tue, 8 Sep 2020 20:48:28 -0700
Message-ID: <CAJtSMgvAyB6PgJFsjzUX9fmYX7Tqm17OJgUOy+kFb5TSSt05rQ@mail.gmail.com>
Subject: Re: ag 2 <(echo 2) gets assertion "p >= path" failed: ..
 /cygwin-3.1.7 ... /cygwin/path.cc", line 3065,
 function: int symlink_info::check
To: Ken Brown <kbrown@cornell.edu>
From: David Dyck via Cygwin <cygwin@cygwin.com>
Reply-To: David Dyck <david.dyck@gmail.com>
Cc: cygwin@cygwin.com
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Thank you Ken, Corinna, and list members


On Tue, Sep 8, 2020 at 12:32 PM Ken Brown <kbrown@cornell.edu> wrote:

> On 9/8/2020 3:26 PM, Ken Brown via Cygwin wrote:
> > On 9/7/2020 4:35 PM, Ken Brown via Cygwin wrote:
> >> On 9/6/2020 4:28 PM, Ken Brown via Cygwin wrote:
> >>> On 9/6/2020 3:47 PM, Ken Brown via Cygwin wrote:
> >>>> On 9/6/2020 2:43 PM, David Dyck via Cygwin wrote:
> >>>>> This command triggers an assertion failure
> >>>>>    "ag" is from the_silver_searcher
> >>>>>
> >>>>> $ ag 2 <(echo 2)
> >>>>> assertion "p >= path" failed: file
> >>>>>
> "/home/corinna/src/cygwin/cygwin-3.1.7/cygwin-3.1.7-1.x86_64/src/newlib-cygwin/winsup/cygwin/path.cc",
>
> >>>>>
> >>>>> line 3065, function: int symlink_info::check(char*, const
> >>>>> suffix_info*, fs_info&, path_conv_handle&)
> >>>>> Aborted (core dumped)
> >>>>>
> >>>>>   3473k 2020/08/22 C:\cygwin64\bin\cygwin1.dll
> >>>>>      Cygwin DLL version info:
> >>>>>          DLL version: 3.1.7
> >>>>> bash
> 4.4.12-3                        OK
> >>>>> the_silver_searcher
> 2.2.0-1                         OK
> >>>> [...]
> >>>>> assertion "p >= path" failed: file
> >>>>>
> "/home/corinna/src/cygwin/cygwin-3.1.7/cygwin-3.1.7-1.x86_64/src/newlib-cygwin/winsup/cygwin/path.cc",
>
> >>>>>
> >>>>> line 3065, function: int symlink_info::check(char*, const
> >>>>> suffix_info*, fs_info&, path_conv_handle&)
> >>>>> Aborted (core dumped)
> >>>> [...]
> >>>>> I've reported this on github as an "ag" bug, but I think it is a bug
> in cygwin
> >>>>
> >>>> An assertion failure in Cygwin code is a Cygwin bug.  I'll take a
> look.
> >>>
> >>> Running
> >>>
> >>>    bash -c '/usr/bin/ag 2 <(echo 2)'
> >>>
> >>> under strace yields the following:
> >>>
> >>>    242  191767 [main] ag 33659 open: open(/dev/fd/63/.ignore, 0x0)
> >>> [...]
> >>>     30  192584 [main] ag 33659 mount_info::conv_to_win32_path:
> src_path
> >>> /proc/self/fd/63/.ignore, dst /proc/self/fd/63/.ignore, flags 0x0, rc 0
> >>> [...]
> >>>     31  193366 [main] ag 33659 mount_info::conv_to_win32_path:
> >>> conv_to_win32_path (pipe:[4295036184]/.ignore)
> >>> [...]
> >>>     31  193550 [main] ag 33659 mount_info::conv_to_win32_path:
> >>> conv_to_win32_path (pipe:[4295036184])
> >>> [...]
> >>>     34  193615 [main] ag 33659 symlink_info::check: 0xC0000034 =
> NtCreateFile
> >>> (\??\C:pipe:[4295036184])
> >>>
> >>> The assertion fails because the path 'C:pipe:[4295036184]' doesn't
> contain a
> >>> backslash.  But probably we should never have allowed ourselves to get
> to the
> >>> point of considering that path.
> >>
> >> I've made some progress but haven't figured out the fix yet.  First,
> for
> >> easier debugging, here's a simpler way to reproduce the problem:
> >>
> >> $ cat proc_bug.c
> >> #include <unistd.h>
> >> #include <stdio.h>
> >> #include <stdlib.h>
> >> #include <fcntl.h>
> >>
> >> int
> >> main ()
> >> {
> >>    int fd[2];
> >>    char fname[100];
> >>
> >>    if (pipe (fd) < 0)
> >>      {
> >>        perror ("pipe");
> >>        exit (1);
> >>      }
> >>    sprintf (fname, "/dev/fd/%d/foo", fd[0]);
> >>    if (open (fname, O_RDONLY) < 0)
> >>      {
> >>        perror ("open");
> >>        exit (1);
> >>      }
> >> }
> >>
> >> $ gcc -o proc_bug proc_bug.c
> >>
> >> $ ./proc_bug.exe
> >> assertion "p >= path" failed: file
> >> "../../../../newlib-cygwin/winsup/cygwin/path.cc", line 3065, function:
> int
> >> symlink_info::check(char*, const suffix_info*, fs_info&,
> path_conv_handle&)
> >> Aborted (core dumped)
> >>
> >> Here's what happens.  The program is trying to open /dev/fd/3/foo,
> where file
> >> descriptor 3 is the read end of a pipe.  path_conv check resolves this
> to
> >> /proc/<pid>/fd/3/foo, creates an fhandler_process for this path, and
> calls (at
> >> path.cc:782) fhandler_process::exists.  The latter fills the filebuf
> with
> >> "pipe:[xxxxxxxxxx]/foo" and returns virt_fsdir.  We're now at
> path.cc:808, and
> >> everything is set up for the assertion failure.
> >
> > This is now fixed.  David, you can test it as soon as Corinna has a
> chance to
> > make a new Cygwin snapshot.
>
> That's now done:
>
>    https://cygwin.com/snapshots/
>
> Ken
>

Thank you!

My first time through
  https://cygwin.com/snapshots/
and
  https://cygwin.com/faq.html#faq.setup.snapshots

Installed the dll alone (
https://cygwin.com/snapshots/x86_64/cygwin1-20200908.dll.xz )

and the tests I performed were successful

$ ack 2 <(echo 2)
2
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