[perl #113424] :stdio + any other layer hangs

# New Ticket Created by  Leon Timmermans 
# Please include the string:  [perl #113424]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org:443/rt3/Ticket/Display.html?id=113424 >


This is a bug report for perl from fawaka@gmail.com,
generated with the help of perlbug 1.39 running under perl 5.16.0.

-----------------------------------------------------------------

The :stdio PerlIO layer doesn't function correctly when it's not the
topmost layer. Take this test:

 use Test::More tests => 1;

 pipe my $in, my $out;
 binmode $in,  ':encoding(utf-8)';
 syswrite $out, "...\n";
 my $line = readline $in;
 is( $line, "...\n", 'Reading utf8' );

It will work fine under normal circumstances, but if you run it with
the PERLIO environmental variable set to "stdio", it will hang. The
reason is that :encoding reads its buffer in blocks, but :stdio's read
method is implemented in terms of fread, which retries until it can
read N bytes. Our own readline is build on top of that, but can't take
its (while/getc) hack to solve this because encoding is inbetween.

I suspect fixing this will require a complete refactor of readline to
integrate it into PerlIO, and even then it looks rather tricky :-/

-----------------------------------------------------------------
---
Flags:
    category=core
    severity=medium
---
Site configuration information for perl 5.16.0:

Configured by leon at Mon May 21 12:51:40 CEST 2012.

Summary of my perl5 (revision 5 version 16 subversion 0) configuration:

  Platform:
    osname=linux, osvers=3.0.0-19-generic, archname=x86_64-linux-thread-multi
    uname='linux leon-laptop 3.0.0-19-generic #33-ubuntu smp thu apr
19 19:05:14 utc 2012 x86_64 x86_64 x86_64 gnulinux '
    config_args='-de
-Dprefix=/home/leon/perl5/perlbrew/perls/perl-5.16.0 -Dusethreads
-Dusesphplib'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing
-pipe -fstack-protector -I/usr/local/include -D_LARGEFILE_SOURCE
-D_FILE_OFFSET_BITS=64',
    optimize='-O2',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -pipe
-fstack-protector -I/usr/local/include'
    ccversion='', gccversion='4.6.1', gccosandvers=''
    intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16
    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 -L/usr/local/lib'
    libpth=/usr/local/lib /lib/x86_64-linux-gnu /lib/../lib
/usr/lib/x86_64-linux-gnu /usr/lib/../lib /lib /usr/lib
    libs=-lnsl -ldb -ldl -lm -lcrypt -lutil -lpthread -lc
    perllibs=-lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
    libc=, so=so, useshrplib=false, libperl=libperl.a
    gnulibc_version='2.13'
  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'

Locally applied patches:


---
@INC for perl 5.16.0:
    /home/leon/perl5/perlbrew/perls/perl-5.16.0/lib/site_perl/5.16.0/x86_64-linux-thread-multi
    /home/leon/perl5/perlbrew/perls/perl-5.16.0/lib/site_perl/5.16.0
    /home/leon/perl5/perlbrew/perls/perl-5.16.0/lib/5.16.0/x86_64-linux-thread-multi
    /home/leon/perl5/perlbrew/perls/perl-5.16.0/lib/5.16.0
    .

---
Environment for perl 5.16.0:
    HOME=/home/leon
    LANG=en_US.utf8
    LANGUAGE=en_US:en_GB:en
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/home/leon/perl5/perlbrew/bin:/home/leon/perl5/perlbrew/perls/perl-5.16.0/bin:/home/leon/bin:/usr/lib/lightdm/lightdm:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games
    PERLBREW_HOME=/home/leon/.perlbrew
    PERLBREW_PATH=/home/leon/perl5/perlbrew/bin:/home/leon/perl5/perlbrew/perls/perl-5.16.0/bin
    PERLBREW_PERL=perl-5.16.0
    PERLBREW_ROOT=/home/leon/perl5/perlbrew
    PERLBREW_VERSION=0.25
    PERL_BADLANG (unset)
    SHELL=/bin/bash

• [perl #113424] :stdio + any other layer hangs by Leon Timmermans