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[perl #115158] a2p wrongly considers string literal "0" is always false

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Ralph Corderoy
October 7, 2012 01:18
[perl #115158] a2p wrongly considers string literal "0" is always false
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# New Ticket Created by  Ralph Corderoy 
# Please include the string:  [perl #115158]
# in the subject line of all future correspondence about this issue. 
# <URL: >

This is a bug report for perl from Ralph Corderoy <>,
generated with the help of perlbug 1.39 running under perl 5.10.1.

[Please describe your issue here]

Perl always considers a scalar with the string value "0" as false due to
a scalar's polymorphism.  awk does something similar, which is where
Perl picked up the idea, but only if the string came from the user, e.g.
an environment variable or read from a file.  If the string is a
constant in the source then it's true, not false.  Perl's a2p(1) doesn't
handle this subtlety.

    $ printf '%s\n' '0 f' '1 t' | awk '$1 && "0"'
    1 t
    $ printf '%s\n' '0 f' '1 t' | perl -e "$(a2p <<<'$1 && "0"')"
    $ a2p <<<'$1 && "0"' | grep print
        print $_ if $Fld[1] && '0';

Originally reported at

[Please do not change anything below this line]
Site configuration information for perl 5.10.1:

Configured by Debian Project at Fri Apr 22 19:20:15 UTC 2011.

Summary of my perl5 (revision 5 version 10 subversion 1) configuration:
    osname=linux, osvers=2.6.24-28-server, archname=x86_64-linux-gnu-thread-multi
    uname='linux allspice 2.6.24-28-server #1 smp wed aug 18 21:17:51 utc 2010 x86_64 gnulinux '
    config_args='-Dusethreads -Duselargefiles -Dccflags=-DDEBIAN -Dcccdlflags=-fPIC -Darchname=x86_64-linux-gnu -Dprefix=/usr -Dprivlib=/usr/share/perl/5.10 -Darchlib=/usr/lib/perl/5.10 -Dvendorprefix=/usr -Dvendorlib=/usr/share/perl5 -Dvendorarch=/usr/lib/perl5 -Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl/5.10.1 -Dsitearch=/usr/local/lib/perl/5.10.1 -Dman1dir=/usr/share/man/man1 -Dman3dir=/usr/share/man/man3 -Dsiteman1dir=/usr/local/man/man1 -Dsiteman3dir=/usr/local/man/man3 -Dman1ext=1 -Dman3ext=3perl -Dpager=/usr/bin/sensible-pager -Uafs -Ud_csh -Ud_ualarm -Uusesfio -Uusenm -DDEBUGGING=-g -Doptimize=-O2 -Duseshrplib -Dd_dosuid -des'
    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
    cc='cc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-O2 -g',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include'
    ccversion='', gccversion='4.4.5', 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 /usr/lib /lib64 /usr/lib64
    libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
    perllibs=-ldl -lm -lpthread -lc -lcrypt
    libc=/lib/, so=so, useshrplib=true,
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fPIC', lddlflags='-shared -O2 -g -L/usr/local/lib -fstack-protector'

Locally applied patches:
    DEBPKG:debian/arm_thread_stress_timeout - Raise the timeout of ext/threads/shared/t/stress.t to accommodate slower build hosts
    DEBPKG:debian/cpan_config_path - Set location of CPAN::Config to /etc/perl as /usr may not be writable.
    DEBPKG:debian/cpan_definstalldirs - Provide a sensible INSTALLDIRS default for modules installed from CPAN.
    DEBPKG:debian/db_file_ver - Remove overly restrictive DB_File version check.
    DEBPKG:debian/doc_info - Replace generic man(1) instructions with Debian-specific information.
    DEBPKG:debian/enc2xs_inc - Tweak enc2xs to follow symlinks and ignore missing @INC directories.
    DEBPKG:debian/errno_ver - Remove Errno version check due to upgrade problems with long-running processes.
    DEBPKG:debian/extutils_hacks - Various debian-specific ExtUtils changes
    DEBPKG:debian/fakeroot - Postpone LD_LIBRARY_PATH evaluation to the binary targets.
    DEBPKG:debian/instmodsh_doc - Debian policy doesn't install .packlist files for core or vendor.
    DEBPKG:debian/ld_run_path - Remove standard libs from LD_RUN_PATH as per Debian policy.
    DEBPKG:debian/libnet_config_path - Set location of libnet.cfg to /etc/perl/Net as /usr may not be writable.
    DEBPKG:debian/m68k_thread_stress - Disable some threads tests on m68k for now due to missing TLS.
    DEBPKG:debian/mod_paths - Tweak @INC ordering for Debian
    DEBPKG:debian/module_build_man_extensions - Adjust Module::Build manual page extensions for the Debian Perl policy
    DEBPKG:debian/perl_synopsis - Rearrange perl.pod
    DEBPKG:debian/prune_libs - Prune the list of libraries wanted to what we actually need.
    DEBPKG:debian/use_gdbm - Explicitly link against -lgdbm_compat in ODBM_File/NDBM_File. 
    DEBPKG:fixes/assorted_docs - [384f06a] Math::BigInt::CalcEmu documentation grammar fix
    DEBPKG:fixes/net_smtp_docs - [ #36038] Document the Net::SMTP 'Port' option
    DEBPKG:fixes/processPL - [ #17224] Always use PERLRUNINST when building perl modules.
    DEBPKG:debian/perlivp - Make perlivp skip include directories in /usr/local
    DEBPKG:fixes/pod2man-index-backslash - Escape backslashes in .IX entries
    DEBPKG:debian/disable-zlib-bundling - Disable zlib bundling in Compress::Raw::Zlib
    DEBPKG:fixes/kfreebsd_cppsymbols - [3b910a0] Add gcc predefined macros to $Config{cppsymbols} on GNU/kFreeBSD.
    DEBPKG:debian/cpanplus_definstalldirs - Configure CPANPLUS to use the site directories by default.
    DEBPKG:debian/cpanplus_config_path - Save local versions of CPANPLUS::Config::System into /etc/perl.
    DEBPKG:fixes/kfreebsd-filecopy-pipes - [16f708c] Fix File::Copy::copy with pipes on GNU/kFreeBSD
    DEBPKG:fixes/anon-tmpfile-dir - [perl #66452] Honor TMPDIR when open()ing an anonymous temporary file
    DEBPKG:fixes/abstract-sockets - [89904c0] Add support for Abstract namespace sockets.
    DEBPKG:fixes/hurd_cppsymbols - [eeb92b7] Add gcc predefined macros to $Config{cppsymbols} on GNU/Hurd.
    DEBPKG:fixes/autodie-flock - Allow for flock returning EAGAIN instead of EWOULDBLOCK on linux/parisc
    DEBPKG:fixes/archive-tar-instance-error - [ #48879] Separate Archive::Tar instance error strings from each other
    DEBPKG:fixes/positive-gpos - [perl #69056] [c584a96] Fix \\G crash on first match
    DEBPKG:debian/devel-ppport-ia64-optim - Work around an ICE on ia64
    DEBPKG:fixes/trie-logic-match - [perl #69973] [0abd0d7] Fix a DoS in Unicode processing [CVE-2009-3626]
    DEBPKG:fixes/hppa-thread-eagain - make the threads-shared test suite more robust, fixing failures on hppa
    DEBPKG:fixes/crash-on-undefined-destroy - [perl #71952] [1f15e67] Fix a NULL pointer dereference when looking for a DESTROY method
    DEBPKG:fixes/tainted-errno - [perl #61976] [be1cf43] fix an errno stringification bug in taint mode
    DEBPKG:patchlevel - List packaged patches for 5.10.1-12 in patchlevel.h

@INC for perl 5.10.1:

Environment for perl 5.10.1:
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PERL_BADLANG (unset)

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