:stdio + any other layer hangs

[p5pRT]

Migrated from rt.perl.org#113424 (status was 'new')

Searchable as RT113424$

[p5pRT]

From @Leont

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

[Leont]

This is a duplicate of #6924