ag 2 <(echo 2) gets assertion "p >= path" failed: .. /cygwin-3.1.7 ... /cygwin/path.cc", line 3065, function: int symlink_info::check
Ken Brown
kbrown@cornell.edu
Tue Sep 8 19:26:22 GMT 2020
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.
Thanks for reporting the problem.
Ken
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