caller(0) returns wrong line number when called from single-stmt else{...}

[p5pRT]

Migrated from rt.perl.org#133895 (status was 'open')

Searchable as RT133895$

[p5pRT]

From @jimav

This is a bug report for perl from jim.avera@​gmail.com,
generated with the help of perlbug 1.40 running under perl 5.26.2.

---

caller(0) seems to return the wrong line number if the sub was called
from an else {...} clause and the call was the only statement in the
block; the line number of the initial "if" is returned, which might
be far away from the actual location of the call.

This messes up Carp​::confess() backtraces, making it sometimes difficult
to locate where confess was called from​:

#!/usr/bin/perl
use strict; use warnings;
sub u(_) { defined($_[0]) ? $_[0] : "undef" }
sub f { warn((join ", ", map{u} (caller(0))), "\n"); }

use Carp;
my $bad = 1;
if (0) {
#
#
# millions of lines of spagetti code
#
#
}
elsif ($bad) {
  # my $x; #un-comment and the problem goes away
  confess("HERE WE ARE"); # HERE WE ARE at /tmp/t2 line 8
}

---

---

Flags​:
  category=core
  severity=low

---

Site configuration information for perl 5.26.2​:

Configured by Ubuntu at Mon Nov 19 15​:05​:42 UTC 2018.

Summary of my perl5 (revision 5 version 26 subversion 2) configuration​:
 
  Platform​:
  osname=linux
  osvers=4.9.0
  archname=x86_64-linux-gnu-thread-multi
  uname='linux localhost 4.9.0 #1 smp debian 4.9.0 x86_64 gnulinux '
  config_args='-Dusethreads -Duselargefiles -Dcc=x86_64-linux-gnu-gcc -Dcpp=x86_64-linux-gnu-cpp -Dld=x86_64-linux-gnu-gcc -Dccflags=-DDEBIAN -Wdate-time -D_FORTIFY_SOURCE=2 -g -O2 -fdebug-prefix-map=/build/perl-6mb423/perl-5.26.2=. -fstack-protector-strong -Wformat -Werror=format-security -Dldflags= -Wl,-Bsymbolic-functions -Wl,-z,relro -Dlddlflags=-shared -Wl,-Bsymbolic-functions -Wl,-z,relro -Dcccdlflags=-fPIC -Darchname=x86_64-linux-gnu -Dprefix=/usr -Dprivlib=/usr/share/perl/5.26 -Darchlib=/usr/lib/x86_64-linux-gnu/perl/5.26 -Dvendorprefix=/usr -Dvendorlib=/usr/share/perl5 -Dvendorarch=/usr/lib/x86_64-linux-gnu/perl5/5.26 -Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl/5.26.2 -Dsitearch=/usr/local/lib/x86_64-linux-gnu/perl/5.26.2 -Dman1dir=/usr/share/man/man1 -Dman3dir=/usr/share/man/man3 -Dsiteman1dir=/usr/local/man/man1 -Dsiteman3dir=/usr/local/man/man3 -Duse64bitint
-Dman1ext=1 -Dman3ext=3perl -Dpager=/usr/bin/sensible-pager -Uafs -Ud_csh -Ud_ualarm -Uusesfio -Uusenm -Ui_libutil -Ui_xlocale -Uversiononly -DDEBUGGING=-g -Doptimize=-O2 -dEs -Duseshrplib -Dlibperl=libperl.so.5.26.2'
  hint=recommended
  useposix=true
  d_sigaction=define
  useithreads=define
  usemultiplicity=define
  use64bitint=define
  use64bitall=define
  uselongdouble=undef
  usemymalloc=n
  default_inc_excludes_dot=define
  bincompat5005=undef
  Compiler​:
  cc='x86_64-linux-gnu-gcc'
  ccflags ='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fwrapv -fno-strict-aliasing -pipe -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64'
  optimize='-O2 -g'
  cppflags='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fwrapv -fno-strict-aliasing -pipe -I/usr/local/include'
  ccversion=''
  gccversion='8.2.0'
  gccosandvers=''
  intsize=4
  longsize=8
  ptrsize=8
  doublesize=8
  byteorder=12345678
  doublekind=3
  d_longlong=define
  longlongsize=8
  d_longdbl=define
  longdblsize=16
  longdblkind=3
  ivtype='long'
  ivsize=8
  nvtype='double'
  nvsize=8
  Off_t='off_t'
  lseeksize=8
  alignbytes=8
  prototype=define
  Linker and Libraries​:
  ld='x86_64-linux-gnu-gcc'
  ldflags =' -fstack-protector-strong -L/usr/local/lib'
  libpth=/usr/local/lib /usr/lib/gcc/x86_64-linux-gnu/8/include-fixed /usr/include/x86_64-linux-gnu /usr/lib /lib/x86_64-linux-gnu /lib/../lib /usr/lib/x86_64-linux-gnu /usr/lib/../lib /lib
  libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
  perllibs=-ldl -lm -lpthread -lc -lcrypt
  libc=libc-2.28.so
  so=so
  useshrplib=true
  libperl=libperl.so.5.26
  gnulibc_version='2.28'
  Dynamic Linking​:
  dlsrc=dl_dlopen.xs
  dlext=so
  d_dlsymun=undef
  ccdlflags='-Wl,-E'
  cccdlflags='-fPIC'
  lddlflags='-shared -L/usr/local/lib -fstack-protector-strong'

Locally applied patches​:
  DEBPKG​:debian/cpan_definstalldirs - Provide a sensible INSTALLDIRS default for modules installed from CPAN.
  DEBPKG​:debian/db_file_ver - https://bugs.debian.org/340047 Remove overly restrictive DB_File version check.
  DEBPKG​:debian/doc_info - Replace generic man(1) instructions with Debian-specific information.
  DEBPKG​:debian/enc2xs_inc - https://bugs.debian.org/290336 Tweak enc2xs to follow symlinks and ignore missing @​INC directories.
  DEBPKG​:debian/errno_ver - https://bugs.debian.org/343351 Remove Errno version check due to upgrade problems with long-running processes.
  DEBPKG​:debian/libperl_embed_doc - https://bugs.debian.org/186778 Note that libperl-dev package is required for embedded linking
  DEBPKG​:fixes/respect_umask - Respect umask during installation
  DEBPKG​:debian/writable_site_dirs - Set umask approproately for site install directories
  DEBPKG​:debian/extutils_set_libperl_path - EU​:MM​: set location of libperl.a under /usr/lib
  DEBPKG​:debian/no_packlist_perllocal - Don't install .packlist or perllocal.pod for perl or vendor
  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/perlivp - https://bugs.debian.org/510895 Make perlivp skip include directories in /usr/local
  DEBPKG​:debian/deprecate-with-apt - https://bugs.debian.org/747628 Point users to Debian packages of deprecated core modules
  DEBPKG​:debian/squelch-locale-warnings - https://bugs.debian.org/508764 Squelch locale warnings in Debian package maintainer scripts
  DEBPKG​:debian/patchlevel - https://bugs.debian.org/567489 List packaged patches for 5.26.2-7ubuntu0.1 in patchlevel.h
  DEBPKG​:fixes/document_makemaker_ccflags - https://bugs.debian.org/628522 [rt.cpan.org #68613] Document that CCFLAGS should include $Config{ccflags}
  DEBPKG​:debian/find_html2text - https://bugs.debian.org/640479 Configure CPAN​::Distribution with correct name of html2text
  DEBPKG​:debian/perl5db-x-terminal-emulator.patch - https://bugs.debian.org/668490 Invoke x-terminal-emulator rather than xterm in perl5db.pl
  DEBPKG​:debian/cpan-missing-site-dirs - https://bugs.debian.org/688842 Fix CPAN​::FirstTime defaults with nonexisting site dirs if a parent is writable
  DEBPKG​:fixes/memoize_storable_nstore - [rt.cpan.org #77790] https://bugs.debian.org/587650 Memoize​::Storable​: respect 'nstore' option not respected
  DEBPKG​:debian/makemaker-pasthru - https://bugs.debian.org/758471 Pass LD settings through to subdirectories
  DEBPKG​:debian/makemaker-manext - https://bugs.debian.org/247370 Make EU​::MakeMaker honour MANnEXT settings in generated manpage headers
  DEBPKG​:debian/kfreebsd-softupdates - https://bugs.debian.org/796798 Work around Debian Bug#796798
  DEBPKG​:fixes/autodie-scope - https://bugs.debian.org/798096 Fix a scoping issue with "no autodie" and the "system" sub
  DEBPKG​:fixes/memoize-pod - [rt.cpan.org #89441] Fix POD errors in Memoize
  DEBPKG​:debian/hurd-softupdates - https://bugs.debian.org/822735 Fix t/op/stat.t failures on hurd
  DEBPKG​:fixes/math_complex_doc_great_circle - https://bugs.debian.org/697567 [rt.cpan.org #114104] Math​::Trig​: clarify definition of great_circle_midpoint
  DEBPKG​:fixes/math_complex_doc_see_also - https://bugs.debian.org/697568 [rt.cpan.org #114105] Math​::Trig​: add missing SEE ALSO
  DEBPKG​:fixes/math_complex_doc_angle_units - https://bugs.debian.org/731505 [rt.cpan.org #114106] Math​::Trig​: document angle units
  DEBPKG​:fixes/cpan_web_link - https://bugs.debian.org/367291 CPAN​: Add link to main CPAN web site
  DEBPKG​:fixes/time_piece_doc - https://bugs.debian.org/817925 Time​::Piece​: Improve documentation for add_months and add_years
  DEBPKG​:fixes/extutils_makemaker_reproducible - https​://bugs.debian.org/835815 https://bugs.debian.org/834190 Make perllocal.pod files reproducible
  DEBPKG​:fixes/file_path_hurd_errno - File-Path​: Fix test failure in Hurd due to hard-coded ENOENT
  DEBPKG​:debian/hppa_op_optimize_workaround - https://bugs.debian.org/838613 Temporarily lower the optimization of op.c on hppa due to gcc-6 problems
  DEBPKG​:debian/installman-utf8 - https://bugs.debian.org/840211 Generate man pages with UTF-8 characters
  DEBPKG​:fixes/file_path_chmod_race - https://bugs.debian.org/863870 [rt.cpan.org #121951] Prevent directory chmod race attack.
  DEBPKG​:fixes/extutils_file_path_compat - Correct the order of tests of chmod(). (#294)
  DEBPKG​:fixes/getopt-long-2 - [rt.cpan.org #120300] Withdraw part of commit 5d9947fb445327c7299d8beb009d609bc70066c0, which tries to implement more GNU getopt_long campatibility. GNU
  DEBPKG​:fixes/getopt-long-3 - provide a default value for optional arguments
  DEBPKG​:fixes/getopt-long-4 - https://bugs.debian.org/864544 [rt.cpan.org #122068] Fix issue #122068.
  DEBPKG​:fixes/test-builder-reset - https://bugs.debian.org/865894 Reset inside subtest maintains parent
  DEBPKG​:debian/hppa_opmini_optimize_workaround - https://bugs.debian.org/869122 Lower the optimization level of opmini.c on hppa
  DEBPKG​:debian/sh4_op_optimize_workaround - https://bugs.debian.org/869373 Also lower the optimization level of op.c and opmini.c on sh4
  DEBPKG​:fixes/json-pp-example - [rt.cpan.org #92793] https://bugs.debian.org/871837 fix RT-92793​: bug in SYNOPSIS
  DEBPKG​:debian/perldoc-pager - https://bugs.debian.org/870340 [rt.cpan.org #120229] Fix perldoc terminal escapes when sensible-pager is less
  DEBPKG​:debian/prune_libs - https://bugs.debian.org/128355 Prune the list of libraries wanted to what we actually need.
  DEBPKG​:fixes/rename-filexp.U-phase1 - regen-configure​: rename filexp.U to filexp_path.U, phase 1
  DEBPKG​:fixes/rename-filexp.U-phase2 - regen-configure​: rename filexp.U to filexp_path.U, phase 2
  DEBPKG​:fixes/packaging_test_skips - Skip various tests if PERL_BUILD_PACKAGING is set
  DEBPKG​:debian/mod_paths - Tweak @​INC ordering for Debian
  DEBPKG​:fixes/encode-alias-regexp - https​://bugs.debian.org/880085 fix dankogai/p5-encode#127
  DEBPKG​:fixes/CVE-2018-6797-testcase - [perl #132227] (perl #132227) restart a node if we change to uni rules within the node and encounter a sharp S
  DEBPKG​:fixes/test-printf-null - https://bugs.debian.org/893601 Fix pointer to integer cast in null_printf check
  DEBPKG​:debian/configure-regen - https://bugs.debian.org/762638 Regenerate Configure et al. after probe unit changes
  DEBPKG​:fixes/CVE-2018-12015-Archive-Tar-directory-traversal - https://bugs.debian.org/900834 [rt.cpan.org #125523] Remove existing files before overwriting them
  DEBPKG​:debian/gdbm-fatal - [perl #133295] https://bugs.debian.org/904005 Temporarily skip GDBM_File fatal.t for gdbm >= 1.15 compatibility
  DEBPKG​:fixes/CVE-2018-18311.patch - [PATCH] Perl_my_setenv(); handle integer wrap
  DEBPKG​:fixes/CVE-2018-18312.patch - [PATCH 242/242] PATCH​: [perl #133423] for 5.26 maint
  DEBPKG​:fixes/CVE-2018-18313.patch - [PATCH] regcomp.c​: Convert some strchr to memchr
  DEBPKG​:fixes/CVE-2018-18314.patch - [PATCH] fix #131649 - extended charclass can trigger assert

---

@​INC for perl 5.26.2​:
  /home/jima/lib/perl
  /home/jima/perl5/lib/perl5/x86_64-linux-gnu-thread-multi
  /home/jima/perl5/lib/perl5/5.26.2/x86_64-linux-gnu-thread-multi
  /home/jima/perl5/lib/perl5/5.26.2
  /home/jima/perl5/lib/perl5/x86_64-linux-gnu-thread-multi
  /home/jima/perl5/lib/perl5
  /etc/perl
  /usr/local/lib/x86_64-linux-gnu/perl/5.26.2
  /usr/local/share/perl/5.26.2
  /usr/lib/x86_64-linux-gnu/perl5/5.26
  /usr/share/perl5
  /usr/lib/x86_64-linux-gnu/perl/5.26
  /usr/share/perl/5.26
  /home/jima/perl5/lib/perl5/5.26.1
  /home/jima/perl5/lib/perl5/5.26.1/x86_64-linux-gnu-thread-multi
  /home/jima/perl5/lib/perl5/5.26.0
  /home/jima/perl5/lib/perl5/5.26.0/x86_64-linux-gnu-thread-multi
  /usr/local/lib/site_perl
  /usr/lib/x86_64-linux-gnu/perl-base

---

Environment for perl 5.26.2​:
  HOME=/home/jima
  LANG=en_US.UTF-8
  LANGUAGE (unset)
  LC_COLLATE=C
  LD_LIBRARY_PATH (unset)
  LOGDIR (unset)
  PATH=/home/jima/.local/bin​:/home/jima/perl5/bin​:/home/jima/bin​:/home/jima/jima_tools/x86_64/bin​:/home/jima/jima_tools/bin​:/opt/Qt/5.12.1/gcc_64/bin​:/opt/Qt/Tools/QtCreator/bin​:/usr/bin​:/bin​:/usr/sbin​:/sbin​:/usr/bin/X11​:/usr/local/bin​:/home/jima/perl5/bin​:/usr/local/sbin​:/usr/games​:/usr/local/games​:/snap/bin​:/usr/lib/jvm/java-8-oracle/bin​:/usr/lib/jvm/java-8-oracle/jre/bin​:.
  PERL5LIB=/home/jima/lib/perl​:/home/jima/perl5/lib/perl5/x86_64-linux-gnu-thread-multi​:/home/jima/perl5/lib/perl5
  PERL_BADLANG (unset)
  PERL_LOCAL_LIB_ROOT=/home/jima/perl5
  PERL_MB_OPT=--install_base /home/jima/perl5
  PERL_MM_OPT=INSTALL_BASE=/home/jima/perl5
  SHELL=/bin/bash

[p5pRT]

From [email protected]

I can confirm this on 5.22.4 Cygwin.

$ perl
use strict;
use warnings;
sub u(_) { defined($_[0]) ? $_[0] : "undef" }
sub f { warn((join ", ", map{u} (caller(0))), "\n"); }
use Carp;
my $bad = 1;
if (0) {
  # # # millions of lines of spagetti code # #
  }
elsif ($bad) {
  # my $x; #un-comment and the problem goes away
  confess("HERE WE ARE"); # HERE WE ARE at /tmp/t2 line 8
}
HERE WE ARE at - line 7.

$ perl
use strict;
use warnings;
sub u(_) { defined($_[0]) ? $_[0] : "undef" }
sub f { warn((join ", ", map{u} (caller(0))), "\n"); }
use Carp;
my $bad = 1;
if ($bad - 1) {
  # # # millions of lines of spagetti code # #
  die;
}
elsif ($bad) {
  # my $x; #un-comment and the problem goes away
  confess("HERE WE ARE 13"); # HERE WE ARE at /tmp/t2 line 8
}
HERE WE ARE 13 at - line 7.

$ perl
use strict;
use warnings;
sub u(_) { defined($_[0]) ? $_[0] : "undef" }
sub f { warn((join ", ", map{u} (caller(0))), "\n"); }
use Carp;
my $bad = 1;
if ($bad - 1) {
  # # # millions of lines of spagetti code # #
  die;
}
elsif ($bad) {
  my $x; #un-comment and the problem goes away
  confess("HERE WE ARE 13"); # HERE WE ARE at /tmp/t2 line 8
}
HERE WE ARE 13 at - line 13.

$ perl
use strict;
use warnings;
sub u(_) { defined($_[0]) ? $_[0] : "undef" }
sub f { warn((join ", ", map{u} (caller(0))), "\n"); }
use Carp;
my $bad = 1;
if ($bad - 1) {
  # # # millions of lines of spagetti code # #
  die;
}
elsif ($bad) {
  # my $x; #un-comment and the problem goes away
  1;
  confess("HERE WE ARE 14"); # HERE WE ARE at /tmp/t2 line 8
}
HERE WE ARE 14 at - line 14.

$ perl
use strict;
use warnings;
sub u(_) { defined($_[0]) ? $_[0] : "undef" }
sub f { warn((join ", ", map{u} (caller(0))), "\n"); }
use Carp;
my $bad = 1;
if ($bad - 1) {
  # # # millions of lines of spagetti code # #
  die;
}
elsif ($bad) {
  # my $x; #un-comment and the problem goes away
  confess("HERE WE ARE 13"); # HERE WE ARE at /tmp/t2 line 8
  1;
}
HERE WE ARE 13 at - line 13.

$ perl
use strict;
use warnings;
sub u(_) { defined($_[0]) ? $_[0] : "undef" }
sub f { warn((join ", ", map{u} (caller(0))), "\n"); }
use Carp;
my $bad = 1;
if ($bad - 1) {
  # # # millions of lines of spagetti code # #
  die;
}
elsif ($bad) {
  confess("HERE WE ARE 13"); # HERE WE ARE at /tmp/t2 line 8
}
HERE WE ARE 13 at - line 7.

[p5pRT]

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