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[perl #119811] Two DB::lsub oddities

From:
Father Chrysostomos
Date:
September 15, 2013 20:27
Subject:
[perl #119811] Two DB::lsub oddities
Message ID:
rt-3.6.HEAD-1873-1379276824-574.119811-75-0@perl.org
# New Ticket Created by  Father Chrysostomos 
# Please include the string:  [perl #119811]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org:443/rt3/Ticket/Display.html?id=119811 >


DB::sub has to exist for DB::lsub to be called.

#!perl -d:Peek
sub DB::DB{}
sub DB::lsub { warn "called" }
sub foo :lvalue {}
foo(); # utter silence


#!perl -d:Peek
sub DB::DB{}
sub DB::lsub { warn "called" }
sub DB::sub{} # dummy sub
sub foo :lvalue {}
foo(); # utter silence
__END__
called at - line 3.

Why this limitation?

Also, if DB::sub is defined, then DB::lsub lookup autovivifies %DB::lsub (the hash), even if &DB::lsub is not defined.  It has been this way since 1ad62f649 added support for lsub.

#!perl -d:Peek

sub DB::DB {}
sub DB::sub {}

sub foo:lvalue{}
foo();
Dump $DB::{lsub};
__END__
SV = PVGV(0x7ff003066790) at 0x7ff003029808
  REFCNT = 1
  FLAGS = (MULTI)
  NAME = "lsub"
  NAMELEN = 4
  GvSTASH = 0x7ff0030052e8	"DB"
  GP = 0x7ff002c0bcc0
    SV = 0x0
    REFCNT = 1
    IO = 0x0
    FORM = 0x0  
    AV = 0x0
    HV = 0x7ff003029820  <----- look
    CV = 0x0
    CVGEN = 0x0
    LINE = 7
    FILE = "-"
    FLAGS = 0x2
    EGV = 0x7ff003029808	"lsub"


Why on earth is that hash being vivified?  What is it for?

---
Flags:
    category=core
    severity=low
---
Site configuration information for perl 5.19.4:

Configured by sprout at Mon Sep  9 00:16:24 PDT 2013.

Summary of my perl5 (revision 5 version 19 subversion 4) configuration:
  Commit id: d47819ff6f55bfaa4b7eddc66c6db7d7dfdec11c
  Platform:
    osname=darwin, osvers=12.2.0, archname=darwin-2level
    uname='darwin pint.local 12.2.0 darwin kernel version 12.2.0: sat aug 25 00:48:52 pdt 2012; root:xnu-2050.18.24~1release_x86_64 x86_64 '
    config_args='-de -Dcc=gcc -Dusedevel -Doptimize=-ggdb3 -Aoptimize=-O0 -DDEBUGGING'
    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='gcc', ccflags ='-fno-common -DPERL_DARWIN -no-cpp-precomp -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include',
    optimize='-ggdb3 -O0',
    cppflags='-no-cpp-precomp -fno-common -DPERL_DARWIN -no-cpp-precomp -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include'
    ccversion='', gccversion='4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2336.11.00)', 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 -L/usr/local/lib'
    libpth=/usr/local/lib /usr/lib
    libs=-ldbm -ldl -lm -lutil -lc
    perllibs=-ldl -lm -lutil -lc
    libc=, 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 -L/usr/local/lib -fstack-protector'


---
@INC for perl 5.19.4:
    lib
    /usr/local/lib/perl5/site_perl/5.19.4/darwin-2level
    /usr/local/lib/perl5/site_perl/5.19.4
    /usr/local/lib/perl5/5.19.4/darwin-2level
    /usr/local/lib/perl5/5.19.4
    /usr/local/lib/perl5/site_perl
    .

---
Environment for perl 5.19.4:
    DYLD_LIBRARY_PATH (unset)
    HOME=/Users/sprout
    LANG=en_US.UTF-8
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/local/bin
    PERL_BADLANG (unset)
    SHELL=/bin/bash




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