[perl #130198] chop(@x =~ tr///)

# New Ticket Created by  Hugo van der Sanden 
# Please include the string:  [perl #130198]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=130198 >


This is a bug report for perl from hv@crypt.org,
generated with the help of perlbug 1.40 running under perl 5.25.7.


-----------------------------------------------------------------
[Please describe your issue here]

In [perl #124368], Brian reports a second unrelated AFL-generated case
that happens to hit the same assertion in Perl_sv_2pv_flags(); in short:

% perl -e 'chop(@x =~ tr/1/1/)'
perl: sv.c:2941: Perl_sv_2pv_flags: Assertion `((svtype)((sv)->sv_flags & 0xff)) != SVt_PVAV && ((svtype)((sv)->sv_flags & 0xff)) != SVt_PVHV && ((svtype)((sv)->sv_flags & 0xff)) != SVt_PVFM' failed.
Aborted (core dumped)
% 

Without -DDEBUGGING:

% ./miniperl -wle '@x=(1..11); print scalar @x; print @x =~ tr/1/1/; print chop(@x =~ tr/1/1/)'
Applying transliteration (tr///) to @x will act on scalar(@x) at -e line 1.
Applying transliteration (tr///) to @x will act on scalar(@x) at -e line 1.
11
2
Use of uninitialized value in transliteration (tr///) at -e line 1.
0
% 

The same works fine on a string, apparently happy to chop the temp scalar:

% ./miniperl -wle '$s="11"; print $s; print $s =~ tr/1/1/; print chop($s =~ tr/1/1/)'
11
2
2
% 

.. but I note that if you throw a scalar() in there (which I'd have expected to have no effect), both cases complain (and in rather dodgy style):

% ./miniperl -wle '@x=(1..11); chop(scalar(@x) =~ tr/1/1/)'
Can't modify scalar in chop at -e line 1, near "tr/1/1/)
"
Execution of -e aborted due to compilation errors.
% ./miniperl -wle '$s="11"; chop(scalar($s) =~ tr/1/1/)'
Can't modify scalar in chop at -e line 1, near "tr/1/1/)
"
Execution of -e aborted due to compilation errors.
% 

I'm not sure now what correct behaviour would be here, or how to make it so.

[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
    category=core
    severity=low
---
Site configuration information for perl 5.25.7:

Configured by hv at Wed Nov  9 13:58:26 GMT 2016.

Summary of my perl5 (revision 5 version 25 subversion 7) configuration:
  Commit id: 392582f8c00033c1199d338baf72f42bbd9ef2dc
  Platform:
    osname=linux
    osvers=3.13.0-37-generic
    archname=x86_64-linux
    uname='linux shad2 3.13.0-37-generic #64-ubuntu smp mon sep 22 21:28:38 utc 2014 x86_64 x86_64 x86_64 gnulinux '
    config_args='-des -Dcc=gcc -Dprefix=/opt/blead-d0 -Doptimize=-g -O0 -DDEBUGGING -Dusedevel -Uversiononly'
    hint=recommended
    useposix=true
    d_sigaction=define
    useithreads=undef
    usemultiplicity=undef
    use64bitint=define
    use64bitall=define
    uselongdouble=undef
    usemymalloc=n
    bincompat5005=undef
  Compiler:
    cc='gcc'
    ccflags ='-fwrapv -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=2'
    optimize='-g -O0'
    cppflags='-fwrapv -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include'
    ccversion=''
    gccversion='4.8.4'
    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='gcc'
    ldflags =' -fstack-protector -L/usr/local/lib'
    libpth=/usr/local/lib /usr/lib/gcc/x86_64-linux-gnu/4.8/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 /lib64 /usr/lib64
    libs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
    perllibs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
    libc=libc-2.19.so
    so=so
    useshrplib=false
    libperl=libperl.a
    gnulibc_version='2.19'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs
    dlext=so
    d_dlsymun=undef
    ccdlflags='-Wl,-E'
    cccdlflags='-fPIC'
    lddlflags='-shared -g -O0 -L/usr/local/lib -fstack-protector'


---
@INC for perl 5.25.7:
    /opt/blead-d0/lib/perl5/site_perl/5.25.7/x86_64-linux
    /opt/blead-d0/lib/perl5/site_perl/5.25.7
    /opt/blead-d0/lib/perl5/5.25.7/x86_64-linux
    /opt/blead-d0/lib/perl5/5.25.7

---
Environment for perl 5.25.7:
    HOME=/home/hv
    LANG=C
    LANGUAGE=en_GB:en
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/home/hv/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
    PERL_BADLANG (unset)
    SHELL=/bin/bash

• [perl #130198] chop(@x =~ tr///) by Hugo van der Sanden