“local $!” erroneously restores empty value

[p5pRT]

Migrated from rt.perl.org#128460 (status was 'open')

Searchable as RT128460$

[p5pRT]

From @FGasper

Created by @FGasper

--------------------
our $foo = 'bar';

unlink('/i/do/not/exist');
{
  local $foo = 'qux';
  local $! = $!;
}
print "err​: [$!]; foo​: [$foo]\n";
--------------------

Run the above, and note that $! doesn�t get restored after the
block with the local()s, even though $foo does get restored.

If you remove the �local $!� line, $! has the expected value.

Perl Info

Flags:
    category=core
    severity=low

Site configuration information for perl 5.22.2:

Configured by buildbot at Sat May  7 02:51:01 PDT 2016.

Summary of my perl5 (revision 5 version 22 subversion 2) configuration:
   
  Platform:
    osname=darwin, osvers=15.4.0, archname=darwin-thread-multi-2level
    uname='darwin teneleven-slave.macports.org 15.4.0 darwin kernel version 15.4.0: fri feb 26 22:08:05 pst 2016; root:xnu-3248.40.184~3release_x86_64 x86_64 '
    config_args='-des -Dprefix=/opt/local -Dscriptdir=/opt/local/bin -Dcppflags=-I/opt/local/include -Dccflags=-pipe -Os  -Dldflags=-L/opt/local/lib -Wl,-headerpad_max_install_names  -Dvendorprefix=/opt/local -Dusemultiplicity=y -Dusethreads -Duseshrplib -Dcc=/usr/bin/clang -Dld=env MACOSX_DEPLOYMENT_TARGET=10.11 /usr/bin/clang -Dman1ext=1pm -Dman3ext=3pm -Dman1dir=/opt/local/share/man/man1p -Dman3dir=/opt/local/share/man/man3p -Dsitebin=/opt/local/libexec/perl5.22/sitebin -Dsiteman1dir=/opt/local/share/perl5.22/siteman/man1 -Dsiteman3dir=/opt/local/share/perl5.22/siteman/man3 -Dvendorbin=/opt/local/libexec/perl5.22 -Dvendorman1dir=/opt/local/share/perl5.22/man/man1 -Dvendorman3dir=/opt/local/share/perl5.22/man/man3 -Dpager=/usr/bin/less -sR -Dperlpath=/opt/local/bin/perl5.22 -Dstartperl=#!/opt/local/bin/perl5.22'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='/usr/bin/clang', ccflags ='-pipe -Os  -fno-common -DPERL_DARWIN -I/opt/local/include -fno-strict-aliasing -fstack-protector-strong -I/opt/local/include -DPERL_USE_SAFE_PUTENV',
    optimize='-O3',
    cppflags='-I/opt/local/include -pipe -Os  -fno-common -DPERL_DARWIN -I/opt/local/include -fno-strict-aliasing -fstack-protector-strong -I/opt/local/include'
    ccversion='', gccversion='4.2.1 Compatible Apple LLVM 7.0.2 (clang-700.1.81)', 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='env MACOSX_DEPLOYMENT_TARGET=10.11 /usr/bin/clang', ldflags ='-L/opt/local/lib -Wl,-headerpad_max_install_names  -fstack-protector-strong'
    libpth=/opt/local/lib /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/7.0.2/lib /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib /usr/lib
    libs=-lpthread -lgdbm -ldbm -ldl -lm -lutil -lc
    perllibs=-lpthread -ldl -lm -lutil -lc
    libc=, so=dylib, useshrplib=true, libperl=libperl.dylib
    gnulibc_version=''
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=bundle, d_dlsymun=undef, ccdlflags=' '
    cccdlflags=' ', lddlflags='-L/opt/local/lib -Wl,-headerpad_max_install_names  -bundle -undefined dynamic_lookup -fstack-protector-strong'



@INC for perl 5.22.2:
    /opt/local/lib/perl5/site_perl/5.22/darwin-thread-multi-2level
    /opt/local/lib/perl5/site_perl/5.22
    /opt/local/lib/perl5/vendor_perl/5.22/darwin-thread-multi-2level
    /opt/local/lib/perl5/vendor_perl/5.22
    /opt/local/lib/perl5/5.22/darwin-thread-multi-2level
    /opt/local/lib/perl5/5.22
    .


Environment for perl 5.22.2:
    DYLD_LIBRARY_PATH (unset)
    HOME=/Users/Felipe
    LANG=en_US.UTF-8
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/opt/local/bin:/opt/local/sbin:/opt/local/bin:/opt/local/sbin:/opt/local/bin:/opt/local/sbin:/Users/Felipe/.opt/bin:/opt/local/bin:/opt/local/sbin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/opt/X11/bin:/Users/Felipe/.opt/bin
    PERL_BADLANG (unset)
    SHELL=/bin/bash

[p5pRT]

From zefram@fysh.org

I think this is a duplicate of [perl #119683].

-zefram

[p5pRT]

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

[p5pRT]

From @FGasper

Hm. The other case involves use of ref; this shows more general breakage?

On June 22, 2016 11​:20​:51 AM CDT, Zefram via RT <perlbug-followup@​perl.org> wrote​:

I think this is a duplicate of [perl #119683].

-zefram

--
Sent from my Android device with K-9 Mail. Please excuse my brevity.

[p5pRT]

From zefram@fysh.org

Felipe Gasper wrote​:

Hm. The other case involves use of ref; this shows more general breakage?

ref turned out not to be critical to it. That ticket moved on to more
general trouble with localisation of $!, due to its magic.

-zefram

[FGasper]

Improved demonstration of the bug:

our $foo = 'bar';

unlink('/i/do/not/exist');
my $val = $!;
print "err: $!\n";
$! = $val;
{
  local $foo = 'qux';
  local $! = $!;
}
print "err: [$!]; foo: [$foo]\n";

[Leont]

This is indeed a duplicate of #13244. Compare:

perl -le '$!=42; {local $! = $!} print 0+$!'

with:

perl -le '$!=42; {local $! = 0+$!} print 0+$!'