Windows: Absolute path in target of symlink directory, problem with -e and -d file tests

[hakonhagland]

I have built a debug version of perl 5.37.6 on Windows 11 using MinGW-w64 and gcc 11.3.0 from https://winlibs.com/ (using the MSVCRT runtime library). Note that this includes #20271, which fixes the readlink behavior on Windows, see #20460 for more information.

When trying to install Path::Tiny using this perl I get a test failure due to -d operator not working on a symlink directory (note: this is a directory, not a file as in #20506). Here is a minimal example:

use feature qw(say);
use strict;
use warnings;
use Cwd qw(getcwd);

my $abspath = getcwd; ## or choose any existing absolute path to a directory here
my $symlink_dir = "A";
my $target = $abspath;
if (!-e $symlink_dir) {
    symlink $target, $symlink_dir or die "Could not create symlink $symlink_dir: $!";
    say "Created symlink dir $symlink_dir with target $target";
}
else {
    die "$symlink_dir already exists..(please delete it first)";
}
if (-d $symlink_dir) {
    say "-d $symlink_dir works";
}
else {
    say "-d $symlink_dir does not work";
}
if (-l $symlink_dir) {
    say "-l $symlink_dir works";
}
else {
    say "-l $symlink_dir does not work";
}

The output is:

-d A does not work
-l A works

Expected output:

-d A works
-l A works

The same problem occurs for the -e operator. If the symlink target is a relative path (not absolute) both -e and -d works fine.

Perl configuration

> perl -V
Summary of my perl5 (revision 5 version 37 subversion 6) configuration:
  Commit id: a589f4b93cf3864d7f665d0974e2d36f028b00b6
  Platform:
    osname=MSWin32
    osvers=10.0.22000.1098
    archname=MSWin32-x64-multi-thread
    uname=''
    config_args='undef'
    hint=recommended
    useposix=true
    d_sigaction=undef
    useithreads=define
    usemultiplicity=define
    use64bitint=define
    use64bitall=undef
    uselongdouble=undef
    usemymalloc=n
    default_inc_excludes_dot=define
  Compiler:
    cc='gcc'
    ccflags =' -DWIN32 -DWIN64 -DDEBUGGING -DPERL_TEXTMODE_SCRIPTS -DMULTIPLICITY -DPERL_IMPLICIT_SYS -DUSE_PERLIO -D__USE_MINGW_ANSI_STDIO -fwrapv -fno-strict-aliasing -mms-bitfields'
    optimize='-g -O0'
    cppflags='-DWIN32'
    ccversion=''
    gccversion='11.3.0'
    gccosandvers=''
    intsize=4
    longsize=4
    ptrsize=8
    doublesize=8
    byteorder=12345678
    doublekind=3
    d_longlong=define
    longlongsize=8
    d_longdbl=define
    longdblsize=16
    longdblkind=3
    ivtype='long long'
    ivsize=8
    nvtype='double'
    nvsize=8
    Off_t='long long'
    lseeksize=8
    alignbytes=8
    prototype=define
  Linker and Libraries:
    ld='g++'
    ldflags ='-g -L"c:\perl-debug\lib\CORE" -L"C:\Winlibs64-Gcc11.3-msvcrt\mingw64\lib" -L"C:\Winlibs64-Gcc11.3-msvcrt\mingw64\x86_64-w64-mingw32\lib" -L"C:\Winlibs64-Gcc11.3-msvcrt\mingw64\lib\gcc\x86_64-w64-mingw32\11.3.0"'
    libpth=C:\Winlibs64-Gcc11.3-msvcrt\mingw64\lib C:\Winlibs64-Gcc11.3-msvcrt\mingw64\x86_64-w64-mingw32\lib C:\Winlibs64-Gcc11.3-msvcrt\mingw64\lib\gcc\x86_64-w64-mingw32\11.3.0
    libs= -lmoldname -lkernel32 -luser32 -lgdi32 -lwinspool -lcomdlg32 -ladvapi32 -lshell32 -lole32 -loleaut32 -lnetapi32 -luuid -lws2_32 -lmpr -lwinmm -lversion -lodbc32 -lodbccp32 -lcomctl32
    perllibs= -lmoldname -lkernel32 -luser32 -lgdi32 -lwinspool -lcomdlg32 -ladvapi32 -lshell32 -lole32 -loleaut32 -lnetapi32 -luuid -lws2_32 -lmpr -lwinmm -lversion -lodbc32 -lodbccp32 -lcomctl32
    libc=
    so=dll
    useshrplib=true
    libperl=libperl537.a
    gnulibc_version=''
  Dynamic Linking:
    dlsrc=dl_win32.xs
    dlext=dll
    d_dlsymun=undef
    ccdlflags=' '
    cccdlflags=' '
    lddlflags='-shared -g -L"c:\perl-debug\lib\CORE" -L"C:\Winlibs64-Gcc11.3-msvcrt\mingw64\lib" -L"C:\Winlibs64-Gcc11.3-msvcrt\mingw64\x86_64-w64-mingw32\lib" -L"C:\Winlibs64-Gcc11.3-msvcrt\mingw64\lib\gcc\x86_64-w64-mingw32\11.3.0"'


Characteristics of this binary (from libperl):
  Compile-time options:
    DEBUGGING
    HAS_TIMES
    HAVE_INTERP_INTERN
    MULTIPLICITY
    PERLIO_LAYERS
    PERL_COPY_ON_WRITE
    PERL_DONT_CREATE_GVSV
    PERL_HASH_FUNC_SIPHASH13
    PERL_HASH_USE_SBOX32
    PERL_IMPLICIT_SYS
    PERL_MALLOC_WRAP
    PERL_OP_PARENT
    PERL_PRESERVE_IVUV
    PERL_TRACK_MEMPOOL
    PERL_USE_SAFE_PUTENV
    USE_64_BIT_INT
    USE_ITHREADS
    USE_LARGE_FILES
    USE_LOCALE
    USE_LOCALE_COLLATE
    USE_LOCALE_CTYPE
    USE_LOCALE_NUMERIC
    USE_LOCALE_TIME
    USE_PERLIO
    USE_PERL_ATOF
  Built under MSWin32
  Compiled at Nov  2 2022 00:00:55
  @INC:
    C:/perl-debug/site/lib
    C:/perl-debug/lib

[hakonhagland]

-d A does not work

Seems like CreateFileA() returns INVALID_HANDLE at line 1812 in win32.c for any absolute path if path is a symlink directory. It does not matter if path uses forward or backward slashes. The result is that execution continues to line 1822, and S_follow_symlinks_to() which is called at this line, is able to read the target of the symlink dir for the first call to win32_readlink() at line 1715, but the while loop (line 1715) continues and tries to read the target as a symlink (but the target of the original symlink is not a symlink itself), and then the second call to win32_readlink() fails, and execution continues to line 1776 and CreateFileA() fails to open the target as a reparse point (since the target is not a reparse point) and execution continues to line 1794 which sets errno to EINVAL, and then INVALID_HANDLE is returned at line 1797 and then -1 is returned at line 1825.

[tonycoz]

It looks like the wrong type of symlink is being created.

[hakonhagland]

It looks like the wrong type of symlink is being created.

@tonycoz Yes that could be the problem! Let me know if I should do any more testing