[perl #130651] regcomp.c:6881: REGEXP *Perl_re_op_compile(SV**const, int, OP *, const regexp_engine *, REGEXP *, _Bool *, U32, U32):Assertion `expr' failed

# New Ticket Created by  Sergey Aleynikov 
# Please include the string:  [perl #130651]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=130651 >


This is a bug report for perl from sergey.aleynikov@gmail.com,
generated with the help of perlbug 1.40 running under perl 5.25.9.


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

While fuzzing perl v5.25.9-35-g32207c637b built with afl and run
under libdislocator, I found the following program

qr!@{return%0}0[(?{!

to cause an assertion failure on debugging builds and crash on regular
build. This is a regression between v5.16.0 and v5.18.0, bisect points
to

9f141731d83a1ac6294a5580a5b11ff41490309a is the first bad commit
commit 9f141731d83a1ac6294a5580a5b11ff41490309a
Author: David Mitchell <davem@iabyn.com>
Date:   Fri Nov 4 10:12:20 2011 +0000

    Move bulk of pp_regcomp() into re_op_compile()

    When called, pp_regcomp() is presented with a list of SVs on the stack.
    Previously, it would perform (amongst other things):
      * overloading those SVs;
      * concatenating them;
      * detection of bare /$qr/;
      * detection of unchanged pattern;
    optionally followed by a call to the built-in or an external regexp
    compiler.

    Since we want to avoid premature concatenation (so that we can handle
    /$runtime(?{...})/), move all these activities from pp_regcomp() into
    re_op_compile().

    This makes re_op_compile() a bit cumbersome, with a large arg list,
    but I haven't found any way of only moving only a subset of the above.

    Note that a side-effect of this is that qr-overloading now works for all
    regex compilations, not just those reached via pp_regcomp(); in particular
    this now invokes the qr method rather than the "" method if available:
    /(??{ $overloaded_object })/

GDB info about the crash location:

(gdb) bt
#0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:58
#1  0x00007f638067840a in __GI_abort () at abort.c:89
#2  0x00007f638066fe47 in __assert_fail_base (fmt=<optimized out>,
assertion=assertion@entry=0x7f6381d5c686 "expr",
    file=file@entry=0x7f6381d5a198 "regcomp.c", line=line@entry=6881,
    function=function@entry=0x7f6381d63580 <__PRETTY_FUNCTION__.16856>
"Perl_re_op_compile") at assert.c:92
#3  0x00007f638066fef2 in __GI___assert_fail (assertion=0x7f6381d5c686
"expr", file=0x7f6381d5a198 "regcomp.c", line=6881,
    function=0x7f6381d63580 <__PRETTY_FUNCTION__.16856>
"Perl_re_op_compile") at assert.c:101
#4  0x00007f6381aa179b in Perl_re_op_compile (patternp=0x7f63838a0b58,
pat_count=0, expr=0x0, eng=0x7f6381fe6540 <PL_core_reg_engine>,
old_re=0x0,
    is_bare_re=0x7ffeaf6f0a5a, orig_rx_flags=0, pm_flags=1342177280)
at regcomp.c:6881
#5  0x00007f6381c080f1 in Perl_pp_regcomp () at pp_ctl.c:107
#6  0x00007f6381afb6e9 in Perl_runops_debug () at dump.c:2444
#7  0x00007f63819f4936 in S_run_body (oldscope=1) at perl.c:2528
#8  0x00007f63819f3eb4 in perl_run (my_perl=0x7f638389c010) at perl.c:2451
#9  0x00007f63819aeeee in main (argc=2, argv=0x7ffeaf6f0e28,
env=0x7ffeaf6f0e40) at perlmain.c:123

[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
    category=core
    severity=medium
---
Site configuration information for perl 5.25.9:

Configured by root at Sat Jan 14 02:25:05 MSK 2017.

Summary of my perl5 (revision 5 version 25 subversion 9) configuration:
  Commit id: cbe2fc5001aa59cdc73e04cc35e097a2ecfbeec0
  Platform:
    osname=linux
    osvers=3.16.0-4-amd64
    archname=x86_64-linux
    uname='linux dorothy 3.16.0-4-amd64 #1 smp debian 3.16.36-1+deb8u2
(2016-10-19) x86_64 gnulinux '
    config_args='-des -Dusedevel -DDEBUGGING -Dcc=afl-clang-fast
-Doptimize=-O0 -g -ggdb3'
    hint=recommended
    useposix=true
    d_sigaction=define
    useithreads=undef
    usemultiplicity=undef
    use64bitint=define
    use64bitall=define
    uselongdouble=undef
    usemymalloc=n
    bincompat5005=undef
  Compiler:
    cc='afl-clang-fast'
    ccflags ='-DDEBUGGING -fno-strict-aliasing -pipe
-fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE
-D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=2'
    optimize='-O0 -g -ggdb3'
    cppflags='-DDEBUGGING -fno-strict-aliasing -pipe
-fstack-protector-strong -I/usr/local/include'
    ccversion=''
    gccversion='4.2.1 Compatible Clang 3.9.1 (tags/RELEASE_391/rc2)'
    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='afl-clang-fast'
    ldflags =' -fstack-protector-strong -L/usr/local/lib'
    libpth=/usr/local/lib /usr/lib/llvm-3.9/bin/../lib/clang/3.9.1/lib
/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=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
    perllibs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
    libc=libc-2.24.so
    so=so
    useshrplib=false
    libperl=libperl.a
    gnulibc_version='2.24'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs
    dlext=so
    d_dlsymun=undef
    ccdlflags='-Wl,-E'
    cccdlflags='-fPIC'
    lddlflags='-shared -O0 -g -ggdb3 -L/usr/local/lib -fstack-protector-strong'


---
@INC for perl 5.25.9:
    lib
    /usr/local/lib/perl5/site_perl/5.25.9/x86_64-linux
    /usr/local/lib/perl5/site_perl/5.25.9
    /usr/local/lib/perl5/5.25.9/x86_64-linux
    /usr/local/lib/perl5/5.25.9

---
Environment for perl 5.25.9:
    HOME=/home/afl
    LANG=en_US.UTF-8
    LANGUAGE=en_US:en
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/home/afl/perlbrew/bin:/home/afl/perlbrew/perls/perl-5.22.1/bin:/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games
    PERLBREW_BASHRC_VERSION=0.78
    PERLBREW_HOME=/home/afl/.perlbrew
    PERLBREW_MANPATH=/home/afl/perlbrew/perls/perl-5.22.1/man
    PERLBREW_PATH=/home/afl/perlbrew/bin:/home/afl/perlbrew/perls/perl-5.22.1/bin
    PERLBREW_PERL=perl-5.22.1
    PERLBREW_ROOT=/home/afl/perlbrew
    PERLBREW_VERSION=0.78
    PERL_BADLANG (unset)
    SHELL=/usr/bin/zsh

• [perl #130651] regcomp.c:6881: REGEXP *Perl_re_op_compile(SV**const, int, OP *, const regexp_engine *, REGEXP *, _Bool *, U32, U32):Assertion `expr' failed by Sergey Aleynikov
• Re: [perl #130651] regcomp.c:6881: REGEXP *Perl_re_op_compile(SV**const, int, OP *, const regexp_engine *, REGEXP *, _Bool *, U32, U32):Assertion `expr' failed by Dave Mitchell