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[perl #24067] IO::Handle::error doesn't report errors

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From:
perlbug-followup
Date:
September 29, 2003 20:27
Subject:
[perl #24067] IO::Handle::error doesn't report errors
Message ID:
rt-24067-65403.6.72345364912829@rt.perl.org
# New Ticket Created by  peff-perlbug@peff.net 
# Please include the string:  [perl #24067]
# in the subject line of all future correspondence about this issue. 
# <URL: http://rt.perl.org/rt2/Ticket/Display.html?id=24067 >



This is a bug report for perl from peff-perlbug@peff.net,
generated with the help of perlbug 1.34 running under perl v5.8.0.


-----------------------------------------------------------------
The following perl program writes 4096 bytes to a file, checking for errors:

$ cat foo.pl
use IO::File;
my $fh = new IO::File($ARGV[0], 'w');
$fh->print('a' x 4096) || print "print failed: $!\n";
print "errors: " . ($fh->error() ? "yes ($!)" : "no") . "\n";

When running it on a regular file, it works as expected:
$ perl foo.pl foo.out
errors: no

However, when an error actually occurs, the print statement returns an error
but $fh->error does not return true:
$ perl foo.pl /dev/full
print failed: No space left on device
errors: no

IO.xs shows that IO::Handle::error just calls PerlIO_error, which typically
just calls PerlIOBase_error to check the PERLIO_F_ERROR flag. However, if I
run gdb on the perl binary, I see that:

 - PerlIO_write is called with (in my case) f=0x81a70e4
 - PerlIOBuf_flush correctly sets the flag with the same f=0x81a70e4, and
   sets the PERLIO_F_ERROR flag on f->flags
 - PerlIO_error gets called with f=0x81a70e4 (from Perl_do_print), and
   correctly returns that an error occurred
 - PerlIO_error gets called with f=0x81a70e0, whose flags don't have an
   error; this is *not* for the error message printed to stdout (I also saw
   that happen, and it has a different address).

Whatever the address of the original PerlIO handle is, the final call to
PerlIO_error always has an address 4 bytes less (the size of a pointer on my
platform).

I haven't been able to follow it past here since I'm unclear on exactly where
that pointer comes from (a backtrace shows it comes from XS_IO__Handle_error,
but I can't trace into that).
-----------------------------------------------------------------
---
Flags:
    category=core
    severity=low
---
Site configuration information for perl v5.8.0:

Configured by Debian Project at Thu Sep 11 20:57:21 EST 2003.

Summary of my perl5 (revision 5.0 version 8 subversion 0) configuration:
  Platform:
    osname=linux, osvers=2.4.21-xfs+ti1211, archname=i386-linux-thread-multi
    uname='linux kosh 2.4.21-xfs+ti1211 #1 sat jul 12 10:35:04 est 2003 i686 gnulinux '
    config_args='-Dusethreads -Duselargefiles -Dccflags=-DDEBIAN -Dcccdlflags=-fPIC -Darchname=i386-linux -Dprefix=/usr -Dprivlib=/usr/share/perl/5.8.0 -Darchlib=/usr/lib/perl/5.8.0 -Dvendorprefix=/usr -Dvendorlib=/usr/share/perl5 -Dvendorarch=/usr/lib/perl5 -Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl/5.8.0 -Dsitearch=/usr/local/lib/perl/5.8.0 -Dman1dir=/usr/share/man/man1 -Dman3dir=/usr/share/man/man3 -Dman1ext=1 -Dman3ext=3perl -Dpager=/usr/bin/sensible-pager -Uafs -Ud_csh -Uusesfio -Uusenm -Duseshrplib -Dlibperl=libperl.so.5.8.0 -Dd_dosuid -des'
    hint=recommended, useposix=true, d_sigaction=define
    usethreads=define use5005threads=undef 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 ='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fno-strict-aliasing -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-O3',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fno-strict-aliasing'
    ccversion='', gccversion='3.3.2 20030908 (Debian prerelease)', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=4, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib
    libs=-lgdbm -ldb -ldl -lm -lpthread -lc -lcrypt
    perllibs=-ldl -lm -lpthread -lc -lcrypt
    libc=/lib/libc-2.3.2.so, so=so, useshrplib=true, libperl=libperl.so.5.8.0
    gnulibc_version='2.3.2'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-rdynamic'
    cccdlflags='-fPIC', lddlflags='-shared -L/usr/local/lib'

Locally applied patches:
    

---
@INC for perl v5.8.0:
    /home/peff/local/share/perl/5.8.0
    /home/peff/local/share/perl
    /home/peff/local/lib/perl5/site_perl
    /home/peff/local/lib/perl/5.8.0
    /home/peff/local/lib/perl
    /etc/perl
    /usr/local/lib/perl/5.8.0
    /usr/local/share/perl/5.8.0
    /usr/lib/perl5
    /usr/share/perl5
    /usr/lib/perl/5.8.0
    /usr/share/perl/5.8.0
    /usr/local/lib/site_perl
    .

---
Environment for perl v5.8.0:
    HOME=/home/peff
    LANG=C
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/home/peff/local/bin:/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr/games:/sbin:/usr/sbin:/home/peff/fenris/build/bin:/home/peff/work/mmake/bin:/home/peff/work/sadm/bin
    PERL5LIB=/home/peff/local/share/perl:/home/peff/local/lib/perl5/site_perl:/home/peff/local/lib/perl
    PERL_BADLANG (unset)
    SHELL=/bin/bash


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