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[perl #119799] %{"_<..."} acts on @DB::dbline

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From:
Father Chrysostomos
Date:
September 15, 2013 19:02
Subject:
[perl #119799] %{"_<..."} acts on @DB::dbline
Message ID:
rt-3.6.HEAD-1873-1379271718-649.119799-75-0@perl.org
# New Ticket Created by  Father Chrysostomos 
# Please include the string:  [perl #119799]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org:443/rt3/Ticket/Display.html?id=119799 >


perldebguts says:

       o   Each hash "%{"_<$filename"}" contains breakpoints and actions keyed
           by line number.  Individual entries (as opposed to the whole hash)
           are settable.

This implies that breakpoints set on %{"_<..."} apply to the named file.  That is not actually true, as every %{"_<..."} hash sets breakpoints on lines in @DB::dbline, regardless of which file it refers to.  The assumption is that debuggers will alias *DB::dbline to *{"_<..."} before setting any breakpoints.

Hence, all %{"_<..."} hashes are the same.

Is this a case where the documentation should be expanded to match the implementation?  Or should we change the implementation to make each %{"_<..."} hash work on its corresponding @{"_<..."} array?  The latter seems more useful to me.

Demonstration:

Run this with the -d switch and with PERL5DB set to 1:

#!perl
sub DB::DB { $DB::single = 0, return if $DB::single; print "ok\n"; exit }
${"_<".__FILE__}{5}=1; # set a breakpoint
sub foo {
    die; # line 5
}
foo();

$ PERL5DB=1 ./perl -Ilib -d foo
Died at foo line 5.

If I change the script to alias @DB::dbline to @{"_<".__FILE__} first, it works:

#!perl
sub DB::DB { $DB::single = 0, return if $DB::single; print "ok\n"; exit }
*DB::dbline = \@{"_<".__FILE__}; ${"_<".__FILE__}{5}=1; # set a breakpoint
sub foo {
    die; # line 5
}
foo();

$ PERL5DB=1 ./perl -Ilib -d foo
ok

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

Configured by sprout at Sun Sep  8 12:35:32 PDT 2013.

Summary of my perl5 (revision 5 version 19 subversion 4) configuration:
  Local Commit: 8bdbe216be2163dc1120e62568cc53721b15c224
  Ancestor: 343e71676c47b84ed9e6abecc09a5b212f1ea224
  Platform:
    osname=darwin, osvers=12.2.0, archname=darwin-thread-multi-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 -Accflags=-DPERL_NO_COW -Dmad -Aoptimize=-O0 -DDEBUGGING -Duseithreads -Dusedevel -Dcc=g++ -Duse64bitint'
    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='g++', ccflags ='-fno-common -DPERL_DARWIN -no-cpp-precomp -DPERL_NO_COW -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include',
    optimize='-O3 -O0 -g',
    cppflags='-no-cpp-precomp -fno-common -DPERL_DARWIN -no-cpp-precomp -DPERL_NO_COW -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'

Locally applied patches:
    1261f9a2686d59ceb218285daddc7eca8bf73d2d
    c2ee494e1da60993b35ebeaf0e52fd39b41cb0b7
    21c314caff13031fb9d1ddfb68fcb1b0b993eb06
    7a7c28da32078097a24a89e3a16f77488f0b7d08
    0d72ebc094dbd2953d6ada2a0faa3ddac9f3dd52
    8bdbe216be2163dc1120e62568cc53721b15c224

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