*FH{IO} and $. scoping ickiness

[p5pRT]

Migrated from rt.perl.org#2566 (status was 'open')

Searchable as RT2566$

[p5pRT]

From @simoncozens

othersideofthe:simon ~ % perl -wle 'my $a;
my $f=do { local *FH; open(FH,"/etc/passwd"); *FH; };
0 while <$f>; print $.'
48

othersideofthe:simon ~ % perl -wle 'my $a;
my $f=do { local *FH; open(FH,"/etc/passwd"); *FH{IO}; };
0 while <$f>; print $.'
Use of uninitialized value in print at -e line 1.

othersideofthe:simon ~ % perl -wle 'my $a;
my $f=do { local *FH; open(FH,"/etc/passwd"); *FH{IO}; };
$a=$. while <$f>; print $.'
48

Perl Info

Flags:
    category=core
    severity=low

Site configuration information for perl v5.6.0:

Configured by simon at Wed Mar 22 01:37:29 JST 2000.

Summary of my perl5 (revision 5.0 version 6 subversion 0) configuration:
  Platform:
    osname=linux, osvers=2.2.14, archname=i686-linux
    uname='linux othersideofthe.earth.li 2.2.14 #3 smp mon mar 13 02:10:19 jst 2000 i686 unknown '
    config_args='-d'
    hint=previous, useposix=true, d_sigaction=define
    usethreads=undef use5005threads=undef useithreads=undef usemultiplicity=undef
    useperlio=undef d_sfio=undef uselargefiles=define 
    use64bitint=undef use64bitall=undef uselongdouble=undef usesocks=undef
  Compiler:
    cc='cc', optimize='-g', gccversion=2.95.2 20000220 (Debian GNU/Linux)
    cppflags='-fno-strict-aliasing -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64'
    ccflags ='-fno-strict-aliasing -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64'
    stdchar='char', d_stdstdio=define, usevfork=false
    intsize=4, longsize=4, ptrsize=4, doublesize=8
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=4, usemymalloc=n, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib
    libs=-lnsl -lndbm -lgdbm -ldb -ldl -lm -lc -lposix -lcrypt
    libc=/lib/libc-2.1.3.so, so=so, useshrplib=false, libperl=libperl.a
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-rdynamic'
    cccdlflags='-fpic', lddlflags='-shared -L/usr/local/lib'

Locally applied patches:
    v5.6.0-RC3


@INC for perl v5.6.0:
    /usr/local/lib/perl5/5.6.0/i686-linux
    /usr/local/lib/perl5/5.6.0
    /usr/local/lib/perl5/site_perl/5.6.0/i686-linux
    /usr/local/lib/perl5/site_perl/5.6.0
    /usr/local/lib/perl5/site_perl/5.5.670
    /usr/local/lib/perl5/site_perl
    .


Environment for perl v5.6.0:
    HOME=/home/simon
    LANG (unset)
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/home/simon/bin:/bin:/usr/bin:/usr/X11R6/bin:/usr/rhs/bin:/usr/local/bin:/usr/local/sbin:/usr/sbin:/sbin:/opt/kde/bin:/home/simon/bin
    PERL_BADLANG (unset)
    SHELL=/bin/zsh

[p5pRT]

From @schwern

This appears to have gotten worse.

> othersideofthe:simon ~ % perl -wle 'my $a;
> my $f=do { local *FH; open(FH,"/etc/passwd"); *FH; };
> 0 while <$f>; print $.'
> 48

[~] perl5.6.2 -wle 'my $a;
my $f=do { local *FH; open(FH,"/etc/passwd"); *FH; };
0 while <$f>; print $.'
28
[~] perl5.8.6 -wle 'my $a;
my $f=do { local *FH; open(FH,"/etc/passwd"); *FH; };
0 while <$f>; print $.'
readline() on unopened filehandle FH at -e line 3.
0


> othersideofthe:simon ~ % perl -wle 'my $a;
> my $f=do { local *FH; open(FH,"/etc/passwd"); *FH{IO}; };
> 0 while <$f>; print $.'
> Use of uninitialized value in print at -e line 1.

[~] perl5.6.2 -wle 'my $a;
my $f=do { local *FH; open(FH,"/etc/passwd"); *FH{IO}; };
0 while <$f>; print $.'
Use of uninitialized value in print at -e line 3.

[~] perl5.8.6 -wle 'my $a;
my $f=do { local *FH; open(FH,"/etc/passwd"); *FH{IO}; };
0 while <$f>; print $.'
Use of uninitialized value in print at -e line 3.


> othersideofthe:simon ~ % perl -wle 'my $a;
> my $f=do { local *FH; open(FH,"/etc/passwd"); *FH{IO}; };
> $a=$. while <$f>; print $.'
> 48

[~] perl5.6.2 -wle 'my $a;
my $f=do { local *FH; open(FH,"/etc/passwd"); *FH{IO}; };
$a=$. while <$f>; print $.'
28
[~] perl5.8.6 -wle 'my $a;
my $f=do { local *FH; open(FH,"/etc/passwd"); *FH{IO}; };
$a=$. while <$f>; print $.'
28

[p5pRT]

@simoncozens, thank you for reporting Perl RT 2566. Your ticket has been moved to https://github.com/Perl/perl5/issues/1420

[toddr]

This appears to still be an issue on perl 5.30. $. is not set if you do <$f> where $f was assigned from *FH{IO}

[Leont]

This appears to still be an issue on perl 5.30. $. is not set if you do <$f> where $f was assigned from *FH{IO}

This can also be formulated as «$^LAST_FH is not set if you do <$f> where $f was an IO reference instead of a glob reference»

[tonycoz]

This appears to still be an issue on perl 5.30. $. is not set if you do <$f> where $f was assigned from *FH{IO}

This can also be formulated as $^LAST_FH is not set if you do <$f> where $f was an IO reference instead of a glob reference

It's not so much that it's not set, it's that it's set and then immediately cleared.

Each of the I/O ops either has a rv2gv generated for it (most) or calls rv2gv itself (readline), which for an IO ref create a mortal GV which is then assigned to PL_last_in_gv, on the next FREETMPS that's released and PL_last_in_gv is cleared (in Perl_sv_clear()).