[perl #108288] stat and -T do not set errno consistently

# New Ticket Created by  Father Chrysostomos 
# Please include the string:  [perl #108288]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org:443/rt3/Ticket/Display.html?id=108288 >


stat and most filetest ops, like -r, leave errno alone when called with an unopened filehandle:

$ ./perl -Ilib -le '$! = 7; print $!; stat foo; print $!'
Argument list too long
Argument list too long
$ ./perl -Ilib -le '$! = 7; print $!; -r foo; print $!'
Argument list too long
Argument list too long

But -T sets errno:

$ ./perl -Ilib -le '$! = 7; print $!; -T foo; print $!'
Argument list too long
Bad file descriptor

What should be the correct behaviour?

close() sets errno:

$ ./perl -Ilib -le '$! = 7; print $!; close foo; print $!'
Argument list too long
Bad file descriptor

Is it stat and -r that should change?

Currently, $! cannot be relied upon when a filetest op returns undef.  And, apart from trapping the ‘unopened’ warning or fiddling with B.pm, there is no way to tell whether an IO thingy actually has an fp.  So $! is useless.
---
Flags:
    category=core
    severity=low
---
Site configuration information for perl 5.15.6:

Configured by sprout at Sat Dec 31 10:12:16 PST 2011.

Summary of my perl5 (revision 5 version 15 subversion 6) configuration:
  Local Commit: b2635083831c8935c437465bbeb03aec8b599c01
  Ancestor: 407287f90891c4292ac8268e6566164f3992e28e
  Platform:
    osname=darwin, osvers=10.5.0, archname=darwin-thread-multi-2level
    uname='darwin pint.local 10.5.0 darwin kernel version 10.5.0: fri nov 5 23:20:39 pdt 2010; root:xnu-1504.9.17~1release_i386 i386 '
    config_args='-de -Dusedevel -Duseithreads -DDEBUGGING -Dmad'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=undef, use64bitall=undef, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-fno-common -DPERL_DARWIN -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include',
    optimize='-O3 -g',
    cppflags='-fno-common -DPERL_DARWIN -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include'
    ccversion='', gccversion='4.2.1 (Apple Inc. build 5664)', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='env MACOSX_DEPLOYMENT_TARGET=10.3 cc', ldflags =' -fstack-protector -L/usr/local/lib'
    libpth=/usr/local/lib /usr/lib
    libs=-ldbm -ldl -lm -lutil -lc
    perllibs=-ldl -lm -lutil -lc
    libc=, so=dylib, useshrplib=false, libperl=libperl.a
    gnulibc_version=''
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=bundle, d_dlsymun=undef, ccdlflags=' '
    cccdlflags=' ', lddlflags=' -bundle -undefined dynamic_lookup -L/usr/local/lib -fstack-protector'

Locally applied patches:
    

---
@INC for perl 5.15.6:
    /usr/local/lib/perl5/site_perl/5.15.6/darwin-thread-multi-2level
    /usr/local/lib/perl5/site_perl/5.15.6
    /usr/local/lib/perl5/5.15.6/darwin-thread-multi-2level
    /usr/local/lib/perl5/5.15.6
    /usr/local/lib/perl5/site_perl
    .

---
Environment for perl 5.15.6:
    DYLD_LIBRARY_PATH (unset)
    HOME=/Users/sprout
    LANG=en_US.UTF-8
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/X11/bin:/usr/local/bin
    PERL_BADLANG (unset)
    SHELL=/bin/bash

• [perl #108288] stat and -T do not set errno consistently by Father Chrysostomos