Cwd: different return values between pure perl and XS variants

[p5pRT]

Migrated from rt.perl.org#132648 (status was 'resolved')

Searchable as RT132648$

[p5pRT]

From @eserte

This is a bug report for perl from slaven@​rezic.de,
generated with the help of perlbug 1.40 running under perl 5.26.1.

---

The functions getcwd and abs_path return different values for the
XS and pure perl variants if a directory is non-existent. The XS
variant returns undef, while the PP variant returns an empty string.

A test program​:

#!/usr/bin/perl

use strict;
use warnings;
use Test​::More 'no_plan';
use File​::Temp 'tempdir';
use Cwd 'getcwd', 'abs_path';

my $tmp = tempdir(CLEANUP => 1);
mkdir "$tmp/testdir" or die $!;
chdir "$tmp/testdir" or die $!;
rmdir "$tmp/testdir" or die $!;
is getcwd, undef, 'XS getcwd on non-existent directory';
is abs_path("."), undef, 'XS abs_path on non-existent directory';
{
  no warnings 'redefine';
  # force pure perl variants
  local *Cwd​::abs_path = \&Cwd​::_perl_abs_path;
  local *Cwd​::getcwd = \&Cwd​::_perl_getcwd;
  is Cwd​::getcwd, undef, 'PP getcwd on non-existent directory';
  is Cwd​::abs_path("."), undef, 'PP abs_path on non-existent directory';
}
chdir "/";

__END__

Output​:

ok 1 - XS getcwd on non-existent directory
ok 2 - XS abs_path on non-existent directory
readdir(./..)​: No such file or directory at /tmp/cwd.pl line 20.
not ok 3 - PP getcwd on non-existent directory
# Failed test 'PP getcwd on non-existent directory'
# at /tmp/cwd.pl line 20.
# got​: ''
# expected​: undef
readdir(./..)​: No such file or directory at /tmp/cwd.pl line 21.
not ok 4 - PP abs_path on non-existent directory
# Failed test 'PP abs_path on non-existent directory'
# at /tmp/cwd.pl line 21.
# got​: ''
# expected​: undef
1..4
# Looks like you failed 2 tests of 4.

Additionally, the PP variants are quite loud while the XS variant is
silent in this situation. But this might be acceptable.

Probably the fix is to change all "return ''" statements in _perl_abs_path
to "return undef".

Regards,
  Slaven

---

---

Flags​:
  category=library
  severity=low
  module=Cwd

---

Site configuration information for perl 5.26.1​:

Configured by eserte at Sat Sep 23 09​:36​:11 CEST 2017.

Summary of my perl5 (revision 5 version 26 subversion 1) configuration​:
 
  Platform​:
  osname=linux
  osvers=3.16.0-4-amd64
  archname=x86_64-linux
  uname='linux cabulja 3.16.0-4-amd64 #1 smp debian 3.16.39-1+deb8u2 (2017-03-07) x86_64 gnulinux '
  config_args='-ds -e -Dprefix=/opt/perl-5.26.1 -Dcf_email=srezic@​cpan.org'
  hint=recommended
  useposix=true
  d_sigaction=define
  useithreads=undef
  usemultiplicity=undef
  use64bitint=define
  use64bitall=define
  uselongdouble=undef
  usemymalloc=n
  default_inc_excludes_dot=define
  bincompat5005=undef
  Compiler​:
  cc='cc'
  ccflags ='-fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=2'
  optimize='-O2'
  cppflags='-fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include'
  ccversion=''
  gccversion='4.9.2'
  gccosandvers=''
  intsize=4
  longsize=8
  ptrsize=8
  doublesize=8
  byteorder=12345678
  doublekind=3
  d_longlong=define
  longlongsize=8
  d_longdbl=define
  longdblsize=16
  longdblkind=3
  ivtype='long'
  ivsize=8
  nvtype='double'
  nvsize=8
  Off_t='off_t'
  lseeksize=8
  alignbytes=8
  prototype=define
  Linker and Libraries​:
  ld='cc'
  ldflags =' -fstack-protector-strong -L/usr/local/lib'
  libpth=/usr/local/lib /usr/lib/gcc/x86_64-linux-gnu/4.9/include-fixed /usr/include/x86_64-linux-gnu /usr/lib /lib/x86_64-linux-gnu /lib/../lib /usr/lib/x86_64-linux-gnu /usr/lib/../lib /lib
  libs=-lpthread -lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc -lgdbm_compat
  perllibs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
  libc=libc-2.19.so
  so=so
  useshrplib=false
  libperl=libperl.a
  gnulibc_version='2.19'
  Dynamic Linking​:
  dlsrc=dl_dlopen.xs
  dlext=so
  d_dlsymun=undef
  ccdlflags='-Wl,-E'
  cccdlflags='-fPIC'
  lddlflags='-shared -O2 -L/usr/local/lib -fstack-protector-strong'

---

@​INC for perl 5.26.1​:
  /opt/perl-5.26.1/lib/site_perl/5.26.1/x86_64-linux
  /opt/perl-5.26.1/lib/site_perl/5.26.1
  /opt/perl-5.26.1/lib/5.26.1/x86_64-linux
  /opt/perl-5.26.1/lib/5.26.1

---

Environment for perl 5.26.1​:
  HOME=/home/eserte
  LANG=en_US.UTF-8
  LANGUAGE (unset)
  LD_LIBRARY_PATH (unset)
  LOGDIR (unset)
  PATH=/usr/local/bin​:/usr/bin​:/bin​:/usr/local/sbin​:/usr/sbin​:/sbin​:/home/eserte/bin/linux-gnu​:/home/eserte/bin/sh​:/home/eserte/bin​:/home/eserte/bin/pistachio-perl/bin​:/usr/games​:/home/eserte/devel
  PERLDOC=-MPod​::Perldoc​::ToTextOverstrike
  PERL_BADLANG (unset)
  SHELL=/bin/zsh

[p5pRT]

From zefram@fysh.org

Fixed in commit d2e38af.

-zefram

[p5pRT]

The RT System itself - Status changed from 'new' to 'open'

[p5pRT]

From @jkeenan

On Sun, 24 Dec 2017 11​:16​:06 GMT, zefram@​fysh.org wrote​:

Fixed in commit d2e38af.

-zefram

This does appear to be fixed on FreeBSD, but we've got a smoke test report from Cygwin explicitly FAILing on dist/PathTools/t/cwd_enoent.t. Please see​:

http​://perl.develop-help.com/raw/?id=204663

Thank you very much.
--
James E Keenan (jkeenan@​cpan.org)

[p5pRT]

From @jkeenan

On Tue, 26 Dec 2017 16​:59​:16 GMT, jkeenan wrote​:

On Sun, 24 Dec 2017 11​:16​:06 GMT, zefram@​fysh.org wrote​:

Fixed in commit d2e38af.

-zefram

This does appear to be fixed on FreeBSD, but we've got a smoke test
report from Cygwin explicitly FAILing on
dist/PathTools/t/cwd_enoent.t. Please see​:

http​://perl.develop-help.com/raw/?id=204663

Thank you very much.

Please ignore the above. Wrong ticket.

--
James E Keenan (jkeenan@​cpan.org)

[p5pRT]

@iabyn - Status changed from 'open' to 'pending release'

[p5pRT]

From @tonycoz

On Sun, Dec 24, 2017 at 11​:15​:47AM +0000, Zefram wrote​:

Fixed in commit d2e38af.

This new test has been failing on cygwin since it was introduced.

tony@​saturn ~/dev/perl/git/perl/t
$ ./perl harness -v ../dist/PathTools/t/cwd_enoent.t
../dist/PathTools/t/cwd_enoent.t ..
1..8
not ok 1 - regular getcwd result on non-existent directory
# Failed test 'regular getcwd result on non-existent directory'
# at t/cwd_enoent.t line 30.
# got​: '/tmp/4WuHD3C4IY/testdir'
# expected​: undef
not ok 2 - regular getcwd errno on non-existent directory
# Failed test 'regular getcwd errno on non-existent directory'
# at t/cwd_enoent.t line 31.
# got​: '0'
# expected​: '2'
.​: No such file or directory at t/cwd_enoent.t line 33.
# Looks like your test exited with 2 just after 2.
.​: No such file or directory at ../../lib/File/Temp.pm line 777.
END failed--call queue aborted.
Dubious, test returned 2 (wstat 512, 0x200)
Failed 8/8 subtests

Test Summary Report

---

../dist/PathTools/t/cwd_enoent.t (Wstat​: 512 Tests​: 2 Failed​: 2)
  Failed tests​: 1-2
  Non-zero exit status​: 2
  Parse errors​: Bad plan. You planned 8 tests but ran 2.
Files=1, Tests=2, 0 wallclock secs ( 0.00 usr 0.00 sys + 0.09 cusr 0.00 csys = 0.09 CPU)
Result​: FAIL

tony@​saturn ~/dev/perl/git/perl/t
$ git describe
v5.27.7-132-g22803c6a19

Tony

[p5pRT]

From @eserte

Dana Sun, 14 Jan 2018 18​:32​:28 -0800, tonyc reče​:

On Sun, Dec 24, 2017 at 11​:15​:47AM +0000, Zefram wrote​:

Fixed in commit d2e38af.

This new test has been failing on cygwin since it was introduced.

tony@​saturn ~/dev/perl/git/perl/t
$ ./perl harness -v ../dist/PathTools/t/cwd_enoent.t
../dist/PathTools/t/cwd_enoent.t ..
1..8
not ok 1 - regular getcwd result on non-existent directory
# Failed test 'regular getcwd result on non-existent directory'
# at t/cwd_enoent.t line 30.
# got​: '/tmp/4WuHD3C4IY/testdir'
# expected​: undef
not ok 2 - regular getcwd errno on non-existent directory
# Failed test 'regular getcwd errno on non-existent directory'
# at t/cwd_enoent.t line 31.
# got​: '0'
# expected​: '2'
.​: No such file or directory at t/cwd_enoent.t line 33.
# Looks like your test exited with 2 just after 2.
.​: No such file or directory at ../../lib/File/Temp.pm line 777.
END failed--call queue aborted.
Dubious, test returned 2 (wstat 512, 0x200)
Failed 8/8 subtests

Test Summary Report
-------------------
../dist/PathTools/t/cwd_enoent.t (Wstat​: 512 Tests​: 2 Failed​: 2)
Failed tests​: 1-2
Non-zero exit status​: 2
Parse errors​: Bad plan. You planned 8 tests but ran 2.
Files=1, Tests=2, 0 wallclock secs ( 0.00 usr 0.00 sys + 0.09 cusr
0.00 csys = 0.09 CPU)
Result​: FAIL

tony@​saturn ~/dev/perl/git/perl/t
$ git describe
v5.27.7-132-g22803c6a19

I guess that's because Cygwin's getcwd() is implemented with _backtick_pwd(), and Cygwin's pwd command behaves differently than on Unix --- in this situation it returns the non-existent directory.

Regards,
  Slaven

[p5pRT]

From zefram@fysh.org

Tony Cook wrote​:

# Failed test 'regular getcwd result on non-existent directory'
# at t/cwd_enoent.t line 30.
# got​: '/tmp/4WuHD3C4IY/testdir'
# expected​: undef

For getcwd() to yield a non-error return for a non-existent directory
seems like a bug. Cygwin seems to prefer _backtick_pwd() as its
implementation of getcwd(), so maybe this is a bug in Cygwin's pwd(1).
Would someone on Cygwin please check, firstly, whether pwd(1) actually
exhibits this behaviour for a removed directory, and secondly, whether
the removed directory can actually be addressed by this name. (If it
can be addressed by name, that would seem to be a bug in rmdir().)

.​: No such file or directory at t/cwd_enoent.t line 33.
# Looks like your test exited with 2 just after 2.

This is another problem. That's abs_path() dying, which it shouldn't​:
it's documented to return errors as undef+$!. Cygwin actually uses
fast_abs_path() as its abs_path(), and fast_abs_path() is coded to die
rather than yield undef+$!, so that's a clear bug in fast_abs_path().

-zefram

[p5pRT]

From zefram@fysh.org

I wrote​:

fast_abs_path() as its abs_path(), and fast_abs_path() is coded to die
rather than yield undef+$!, so that's a clear bug in fast_abs_path().

This bit fixed in commit a97021b.

-zefram

[p5pRT]

From @tonycoz

On Mon, Jan 15, 2018 at 11​:28​:06PM +0000, Zefram wrote​:

Tony Cook wrote​:

# Failed test 'regular getcwd result on non-existent directory'
# at t/cwd_enoent.t line 30.
# got​: '/tmp/4WuHD3C4IY/testdir'
# expected​: undef

For getcwd() to yield a non-error return for a non-existent directory
seems like a bug. Cygwin seems to prefer _backtick_pwd() as its
implementation of getcwd(), so maybe this is a bug in Cygwin's pwd(1).
Would someone on Cygwin please check, firstly, whether pwd(1) actually
exhibits this behaviour for a removed directory, and secondly, whether
the removed directory can actually be addressed by this name. (If it
can be addressed by name, that would seem to be a bug in rmdir().)

I tested with​:

tony@​saturn ~/dev/perl/git
$ cat 132648.c
#include <stdio.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>

int main(void) {
  char buf[1000]; /* keeping this simple */
  if (mkdir("foo", 0700) < 0) {
  perror("mkdir");
  return 1;
  }
  if (chdir("foo") < 0) {
  perror("chdir");
  return 1;
  }
  if (rmdir("../foo") < 0) {
  perror("rmdir");
  return 1;
  }

  if (!getcwd(buf, sizeof(buf))) {
  perror("getcwd");
  return 1;
  }
  puts(buf);

  return 0;
}

tony@​saturn ~/dev/perl/git
$ cc -o132648.exe 132648.c

tony@​saturn ~/dev/perl/git
$ ./132648
/home/tony/dev/perl/git/foo

I've asked about it on the cygwin mailing list.

I suspect this will be WONTFIX at the cygwin level.

Tony

[p5pRT]

From zefram@fysh.org

Tony Cook wrote​:

I suspect this will be WONTFIX at the cygwin level.

I'd still like to know which bug it is that they won't fix.

-zefram

[p5pRT]

From @tonycoz

On Tue, Jan 16, 2018 at 05​:50​:47AM +0000, Zefram wrote​:

Tony Cook wrote​:

I suspect this will be WONTFIX at the cygwin level.

I'd still like to know which bug it is that they won't fix.

Well, remembering cygwin is built on top of Win32, and if I'm reading
the code correctly, rather than calling the RemoveDirectory() API,
which fails on "open" directories, cygwin calls NtSetInformationFile()
to mark the directory to be deleted once it's closed.

Having to record that the directory (or file) is marked deleted and
not make it available to getcwd(), open(), opendir(), unlink() etc
might be considered too much work for too little return.

Tony

[p5pRT]

From zefram@fysh.org

Tony Cook wrote​:

Having to record that the directory (or file) is marked deleted and
not make it available to getcwd(), open(), opendir(), unlink() etc

That's not what I'm proposing, and would be totally unworkable.

If rmdir(2) doesn't actually succeed in removing the directory
(immediately), then I'll add a check for that in cwd_enoent.t, skipping
the tests if the directory didn't go away. If rmdir() does remove the
directory and pwd(1) emits a name that can't be used, then I'll add a
check for that in _backtick_pwd(), to prevent it returning an unusable
name.

-zefram

[p5pRT]

From @tonycoz

On Tue, Jan 16, 2018 at 08​:23​:58AM +0000, Zefram wrote​:

Tony Cook wrote​:

Having to record that the directory (or file) is marked deleted and
not make it available to getcwd(), open(), opendir(), unlink() etc

That's not what I'm proposing, and would be totally unworkable.

If rmdir(2) doesn't actually succeed in removing the directory
(immediately), then I'll add a check for that in cwd_enoent.t, skipping
the tests if the directory didn't go away. If rmdir() does remove the
directory and pwd(1) emits a name that can't be used, then I'll add a
check for that in _backtick_pwd(), to prevent it returning an unusable
name.

If this what you need?

tony@​saturn ~/dev/perl/git
$ perl 132648.pl
/home/tony/dev/perl/git/foo

tony@​saturn ~/dev/perl/git
$ cat 132648.pl
#!perl
use Cwd;

mkdir "foo", 0700
  or die "mkdir $!";
chdir "foo"
  or die "chdir $!";
rmdir "../foo"
  or die "rmdir $!";
my $cwd = getcwd
  or die "getcwd $!";
print "$cwd\n";
print "$cwd is a dir\n" if -d $cwd;

Tony