From @briandfoy

Created by brian@mac-pro.local

I found a case where B​::Deparse does the wrong thing. In this foreach-when,
the 1 == 1 is always true and that block always runs. This is the
documented behavior, and there is an output line for every input number​:

  use 5.010;
 
  my $a = 1;
  foreach( 1 .. 10 )
  {
  when( 1 == 1 ) {
  print "Always true. \$_ is $_\n";
  }
  }

This is the result of deparsing on both 5.10.1 through 5.13.1. The 1 == 1 comes
back as just 1, so now a smart match takes place. Only the first input
number triggers the when()​:

  sub BEGIN {
  require 5.01;
  }
  BEGIN {
  $^H{'feature_say'} = q(1);
  $^H{'feature_state'} = q(1);
  $^H{'feature_switch'} = q(1);
  }
  my $a = 1;
  foreach $_ (1 .. 10) {
  when (1) {
  print "Always true. \$_ is $_\n";
  }
  }

Flags:
    category=library
    severity=low
    module=B::Deparse

Site configuration information for perl 5.10.1:

Configured by brian at Sat Dec  5 14:57:53 CST 2009.

Summary of my perl5 (revision 5 version 10 subversion 1) configuration:

  Platform:
    osname=darwin, osvers=10.2.0, archname=darwin-2level
    uname='darwin mac-pro.local 10.2.0 darwin kernel version 10.2.0:
tue nov 3 23:08:29 pst 2009; root:xnu-1486.2.11~3release_i386 i386
i386 '
    config_args='-des -Dprefix=/usr/local/perls/perl-5.10.1'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=undef, usemultiplicity=undef
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-fno-common -DPERL_DARWIN -no-cpp-precomp
-fno-strict-aliasing -pipe -fstack-protector',
    optimize='-O3',
    cppflags='-no-cpp-precomp -fno-common -DPERL_DARWIN
-no-cpp-precomp -fno-strict-aliasing -pipe -fstack-protector'
    ccversion='', gccversion='4.2.1 (Apple Inc. build 5646)', 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='env MACOSX_DEPLOYMENT_TARGET=10.3 cc', ldflags =' -fstack-protector'
    libpth=/usr/lib
    libs=-ldbm -ldl -lm -lutil -lc
    perllibs=-ldl -lm -lutil -lc
    libc=/usr/lib/libc.dylib, 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
-fstack-protector'

Locally applied patches:



@INC for perl 5.10.1:
    /usr/local/perls/perl-5.10.1/lib/5.10.1/darwin-2level
    /usr/local/perls/perl-5.10.1/lib/5.10.1
    /usr/local/perls/perl-5.10.1/lib/site_perl/5.10.1/darwin-2level
    /usr/local/perls/perl-5.10.1/lib/site_perl/5.10.1
    .


Environment for perl 5.10.1:
    DYLD_LIBRARY_PATH (unset)
    HOME=/Users/brian
    LANG=en_US
    LANGUAGE (unset)
    LC_ALL=C
    LC_COLLATE=en_US.utf-8
    LC_CTYPE=en_US.utf-8
    LC_MESSAGES=en_US.utf-8
    LC_MONETARY=en_US.utf-8
    LC_NUMERIC=en_US.utf-8
    LC_TIME=en_US.utf-8
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/Users/brian/bin:/usr/local/bin:/opt/local/bin:/Users/brian/TPR/scripts:/bin:/usr/bin:/sbin:/usr/sbin:/usr/local/mysql/bin:/usr/X11R6/bin:/usr/local/teTeX/bin/powerpc-apple-darwin-current:/usr/local/pgsql/bin:/usr/local/gcj/bin:/Library/Frameworks/Python.framework/Versions/Current/bin
    PERL_BADLANG (unset)
    SHELL=/bin/bash

From @rgarcia

On 23 May 2010 09​:04, brian d foy <perlbug-followup@​perl.org> wrote​:

I found a case where B​::Deparse does the wrong thing. In this foreach-when,
the 1 == 1 is always true and that block always runs. This is the
documented behavior, and there is an output line for every input number​:

       use 5.010;

       my $a = 1;
       foreach( 1 .. 10 )
               {
               when( 1 == 1 ) {
                       print "Always true. \$_ is $_\n";
                       }
               }

This is the result of deparsing on both 5.10.1 through 5.13.1. The 1 == 1 comes
back as just 1, so now a smart match takes place. Only the first input
number triggers the when()​:

       sub BEGIN {
               require 5.01;
       }
       BEGIN {
               $^H{'feature_say'} = q(1);
               $^H{'feature_state'} = q(1);
               $^H{'feature_switch'} = q(1);
       }
       my $a = 1;
       foreach $_ (1 .. 10) {
               when (1) {
                       print "Always true. \$_ is $_\n";
               }
       }

The easiest way to fix that (and also the correct one, given what
B​::Deparse is intended to do) is maybe to always explicitly deparse
the smart match : that is, when ($_~~1) instead of when(1); and for
other cases for non-smartmatch-triggerring syntaxes.

The RT System itself - Status changed from 'new' to 'open'

From zefram@fysh.org

Rafael Garcia-Suarez wrote​:

The easiest way to fix that (and also the correct one, given what
B​::Deparse is intended to do) is maybe to always explicitly deparse
the smart match

That's exactly what *won't* help here. In this case there is no
smartmatch, and the difficulty is to deparse in a way that won't
incorrectly imply a smartmatch.

-zefram

From @rgarcia

On 25 May 2010 12​:02, Zefram <zefram@​fysh.org> wrote​:

Rafael Garcia-Suarez wrote​:

The easiest way to fix that (and also the correct one, given what
B​::Deparse is intended to do) is maybe to always explicitly deparse
the smart match

That's exactly what *won't* help here.  In this case there is no
smartmatch, and the difficulty is to deparse in a way that won't
incorrectly imply a smartmatch.

Yes, it appears that the second half of my sentence was not deparseable either :

and for other cases for non-smartmatch-triggerring syntaxes.

I meant "for other cases" (that is, when there is no ~~ in the op
tree) *output* non-smartmatch-trigerring syntaxes. (which should be
easy, since technically only constant-foldable expressions will cause
a problem)