Incorrect line number reporting due to overoptimization

[p5pRT]

Migrated from rt.perl.org#1031 (status was 'resolved')

Searchable as RT1031$

[p5pRT]

From @tobez

The following script​:

  #! /usr/bin/perl -w
  my $k;
  if (1) {
  #
  #
  #
  my $z = $k+1;
  }

produces ``Use of uninitialized value at bug.pl line 3.'' warning. It
does so in 5.005_03 and 5.005_57.

I tracked the problem down to the optimization performed in op.c's
scope() function, but I am unable to fix it properly (disabling the
optimization does not count, though it fixes the problem). Probably
this output will be helpful for someone​:

[ optimization enabled]
$ perl -MO=Terse bug.pl
bug.pl syntax OK
Use of uninitialized value at /usr/libdata/perl/5.00503/mach/B/Terse.pm line 81.
Use of uninitialized value at /usr/libdata/perl/5.00503/mach/B/Terse.pm line 81.
LISTOP (0x8057940) pp_leave
  OP (0x8059160) pp_enter
  COP (0x80528c0) pp_nextstate
  OP (0x8059120) pp_padsv [1]
  COP (0x8057a00) pp_nextstate
  LISTOP (0x80579c0) pp_scope
  OP (0x8057980) pp_null [173]
  BINOP (0x8059220) pp_sassign
  BINOP (0x8059200) pp_add [3]
  OP (0x80591c0) pp_padsv [1]
  SVOP (0x80591e0) pp_const IV (0x8050ef4) 1
  OP (0x8059180) pp_padsv [2]

The last pp_nextstate corresponds to the line 3.

[ optimization disabled]
$ perl -T bug.pl
Use of uninitialized value at bug.pl line 7.

Correct line number is reported. ^^^^^^

$ perl -T -MO=Terse bug.pl
bug.pl syntax OK
Use of uninitialized value at /usr/libdata/perl/5.00503/mach/B/Terse.pm line 81.
Use of uninitialized value at /usr/libdata/perl/5.00503/mach/B/Terse.pm line 81.
Use of uninitialized value at /usr/libdata/perl/5.00503/mach/B/Terse.pm line 81.
LISTOP (0x8057880) pp_leave
  OP (0x8059500) pp_enter
  COP (0x80528c0) pp_nextstate
  OP (0x80594c0) pp_padsv [1]
  COP (0x8057940) pp_nextstate
  LISTOP (0x8057900) pp_leave
  OP (0x8059600) pp_enter
  COP (0x80578c0) pp_nextstate
  BINOP (0x80595c0) pp_sassign
  BINOP (0x80595a0) pp_add [3]
  OP (0x8059560) pp_padsv [1]
  SVOP (0x8059580) pp_const IV (0x8050ec4) 1
  OP (0x8059520) pp_padsv [2]

pp_scope has been replaced (or is this other way around?) with pp_leave
and pp_enter, and pp_nextstate corresponding to the correct line is
there.

Is there a better way to fix this rather than disabling the optimization
completely?

Perl Info

Site configuration information for perl 5.00503:

Configured by markm at $Date: 1999/05/05 19:09:48 $.

Summary of my perl5 (5.0 patchlevel 5 subversion 3) configuration:
  Platform:
    osname=freebsd, osvers=4.0-current, archname=i386-freebsd
    uname='freebsd freefall.freebsd.org 4.0-current freebsd 4.0-current #0: $Date: 1999/05/05 19:09:48 $'
    hint=recommended, useposix=true, d_sigaction=define
    usethreads=undef useperlio=undef d_sfio=undef
  Compiler:
    cc='cc', optimize='undef', gccversion=egcs-2.91.66 19990314 (egcs-1.1.2 release)
    cppflags=''
    ccflags =''
    stdchar='char', d_stdstdio=undef, usevfork=true
    intsize=4, longsize=4, ptrsize=4, doublesize=8
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    alignbytes=4, usemymalloc=n, prototype=define
  Linker and Libraries:
    ld='cc', ldflags ='-Wl,-E'
    libpth=/usr/lib
    libs=-lm -lc -lcrypt
    libc=/usr/lib/libc.so, so=so, useshrplib=true, libperl=libperl.so.3
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags=' '
    cccdlflags='-DPIC -fpic', lddlflags='-shared'

Locally applied patches:
    


@INC for perl 5.00503:
    /home/tobez/src/Prima
    /home/tobez/src/Prima/scripts/modules
    /usr/libdata/perl/5.00503/mach
    /usr/libdata/perl/5.00503
    /usr/local/lib/perl5/site_perl/5.005/i386-freebsd
    /usr/local/lib/perl5/site_perl/5.005
    .


Environment for perl 5.00503:
    HOME=/home/tobez
    LANG=ru_RU.KOI8-R
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin:/usr/X11R6/bin:/usr/local/site/bin:/home/tobez/bin:/home/tobez/bin/kuim:/plab/usr/home/tobez/bin:/plab/usr/local/site/bin
    PERL5LIB=/home/tobez/src/Prima:/home/tobez/src/Prima/scripts/modules
    PERL_BADLANG (unset)
    SHELL=/usr/local/bin/zsh