perl: op.c:14769: Perl_find_lexical_cv: Assertion `PARENT_PAD_INDEX(name)' failed.

[tonycoz]

Module:

Description

Running this code:

use builtin 'ceil';

my $x;
BEGIN {
    my $e = <<'EOS';
sub { ceil($_[0]) }
EOS
    $x = eval $e;
}

in a DEBUGGING build throws:

$ ./perl -Ilib ../ceilassert.pl 
perl: op.c:14769: Perl_find_lexical_cv: Assertion `PARENT_PAD_INDEX(name)' failed.
Aborted

Backtrace:

#0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
#1  0x00007ffff7c65537 in __GI_abort () at abort.c:79
#2  0x00007ffff7c6540f in __assert_fail_base (
    fmt=0x7ffff7dce128 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n", 
    assertion=0x55555594579a "PARENT_PAD_INDEX(name)", 
    file=0x55555593e331 "op.c", line=14769, function=<optimized out>)
    at assert.c:92
#3  0x00007ffff7c74662 in __GI___assert_fail (
    assertion=0x55555594579a "PARENT_PAD_INDEX(name)", 
    file=0x55555593e331 "op.c", line=14769, 
    function=0x5555559482c0 <__PRETTY_FUNCTION__.33> "Perl_find_lexical_cv")
    at assert.c:101
#4  0x00005555555dd638 in Perl_find_lexical_cv (off=1) at op.c:14769
#5  0x0000555555660eee in yyl_keylookup (s=0x555555c09a2a "($_[0]) }\n\n;", 
    gv=0x0) at toke.c:8805
#6  0x0000555555663a6e in yyl_try (s=0x555555c09a26 "ceil($_[0]) }\n\n;")
    at toke.c:9319
#7  0x0000555555664ed9 in Perl_yylex () at toke.c:9621
#8  0x000055555567ab7e in Perl_yyparse (gramtype=258) at perly.c:357
#9  0x0000555555851412 in S_doeval_compile (gimme=2 '\002', 
    outside=0x555555bf6e08, seq=201, hh=0x0) at pp_ctl.c:3613
#10 0x0000555555858fd3 in Perl_pp_entereval () at pp_ctl.c:4580
#11 0x0000555555729e64 in Perl_runops_debug () at dump.c:2677
#12 0x00005555555f27de in Perl_call_sv (sv=0x555555bf6e08, flags=13)
    at perl.c:3077
#13 0x00005555555fc259 in Perl_call_list (oldscope=2, paramList=0x555555bf6e68)
    at perl.c:5148
#14 0x00005555555d1173 in S_process_special_blocks (floor=42, 
    fullname=0x555555c150f0 "\001", gv=0x555555bf6e80, cv=0x555555bf6e08)
    at op.c:12116
#15 0x00005555555d081a in Perl_newATTRSUB_x (floor=42, o=0x555555c00f60, 
    proto=0x0, attrs=0x0, block=0x555555c0eae0, o_is_gv=false) at op.c:12021
#16 0x000055555567b7d8 in Perl_yyparse (gramtype=258) at perly.y:330
#17 0x00005555555f01b5 in S_parse_body (env=0x0, 
    xsinit=0x5555555a31d2 <xs_init>) at perl.c:2556
#18 0x00005555555ee511 in perl_parse (my_perl=0x555555bd02a0, 
    xsinit=0x5555555a31d2 <xs_init>, argc=3, argv=0x7fffffffe7f8, env=0x0)
    at perl.c:1847
#19 0x00005555555a3118 in main (argc=3, argv=0x7fffffffe7f8, 
    env=0x7fffffffe818) at perlmain.c:106

Steps to Reproduce

Expected behavior

No assertion.

Perl configuration

Summary of my perl5 (revision 5 version 37 subversion 1) configuration:
  Commit id: 75111994648b802c88381a3cd338185fd1bbb6fa
  Platform:
    osname=linux
    osvers=5.10.0-14-amd64
    archname=x86_64-linux
    uname='linux venus 5.10.0-14-amd64 #1 smp debian 5.10.113-1 (2022-04-29) x86_64 gnulinux '
    config_args='-des -Dusedevel -DDEBUGGING -Doptimize=-O0 -g'
    hint=recommended
    useposix=true
    d_sigaction=define
    useithreads=undef
    usemultiplicity=undef
    use64bitint=define
    use64bitall=define
    uselongdouble=undef
    usemymalloc=n
    default_inc_excludes_dot=define
  Compiler:
    cc='cc'
    ccflags ='-fwrapv -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'
    cppflags='-fwrapv -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include'
    ccversion=''
    gccversion='10.2.1 20210110'
    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='cc'
    ldflags =' -fstack-protector-strong -L/usr/local/lib'
    libpth=/usr/local/lib /usr/lib/x86_64-linux-gnu /usr/lib /usr/lib64
    libs=-lpthread -lnsl -lgdbm -ldl -lm -lcrypt -lutil -lc
    perllibs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
    libc=libc-2.31.so
    so=so
    useshrplib=false
    libperl=libperl.a
    gnulibc_version='2.31'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs
    dlext=so
    d_dlsymun=undef
    ccdlflags='-Wl,-E'
    cccdlflags='-fPIC'
    lddlflags='-shared -O0 -g -L/usr/local/lib -fstack-protector-strong'


Characteristics of this binary (from libperl): 
  Compile-time options:
    DEBUGGING
    HAS_TIMES
    PERLIO_LAYERS
    PERL_COPY_ON_WRITE
    PERL_DONT_CREATE_GVSV
    PERL_MALLOC_WRAP
    PERL_OP_PARENT
    PERL_PRESERVE_IVUV
    PERL_USE_DEVEL
    PERL_USE_SAFE_PUTENV
    USE_64_BIT_ALL
    USE_64_BIT_INT
    USE_LARGE_FILES
    USE_LOCALE
    USE_LOCALE_COLLATE
    USE_LOCALE_CTYPE
    USE_LOCALE_NUMERIC
    USE_LOCALE_TIME
    USE_PERLIO
    USE_PERL_ATOF
  Built under linux
  Compiled at Jun 13 2022 14:25:47
  %ENV:
    PERLBREW_BASHRC_VERSION="0.43"
    PERLBREW_HOME="/home/tony/.perlbrew"
    PERLBREW_MANPATH=""
    PERLBREW_PATH="/home/tony/perl5/perlbrew/bin"
    PERLBREW_ROOT="/home/tony/perl5/perlbrew"
    PERLBREW_VERSION="0.67"
  @INC:
    lib
    /usr/local/lib/perl5/site_perl/5.37.1/x86_64-linux
    /usr/local/lib/perl5/site_perl/5.37.1
    /usr/local/lib/perl5/5.37.1/x86_64-linux
    /usr/local/lib/perl5/5.37.1

[jkeenan]

Running this code:

use builtin 'ceil';

my $x;
BEGIN {
    my $e = <<'EOS';
sub { ceil($_[0]) }
EOS
    $x = eval $e;
}

in a DEBUGGING build throws:

$ ./perl -Ilib ../ceilassert.pl 
perl: op.c:14769: Perl_find_lexical_cv: Assertion `PARENT_PAD_INDEX(name)' failed.
Aborted

As you might expect, this problem has been present since ceil was added to builtin. The first commit at which I was able to reproduce this was:

commit 17a8df707746ce70979d18c5b5f9e383c365bbff
Author:     James Raspass <[email protected]>
AuthorDate: Sat Jan 22 11:07:58 2022 +0000
Commit:     Paul "LeoNerd" Evans <[email protected]>
CommitDate: Mon Jan 24 00:35:51 2022 +0000

    Add ceil & floor to builtin

@JRaspass @leonerd , can you take a look?

Thank you very much.
Jim Keenan

[tonycoz]

I expect the problem is with the lexical import mechanism, rather than ceil() itself:

tony@venus:.../git/perl5$ ./perl -Ilib ../19857-import.pl 
perl: op.c:13404: Perl_find_lexical_cv: Assertion `PARENT_PAD_INDEX(name)' failed.
Aborted
tony@venus:.../git/perl5$ cat ../19857-import.pl
use builtin 'is_bool';

my ($x, $y);
BEGIN {
    $x = eval 'is_bool($y)';
}

[tonycoz]

Worse, it happens with plain lexical subs too:

tony@venus:.../git/perl5$ ./perl -e 'my sub foo {} BEGIN { eval "foo()" }'
perl: op.c:13404: Perl_find_lexical_cv: Assertion `PARENT_PAD_INDEX(name)' failed.
Aborted

[jkeenan]

./perl -e 'my sub foo {} BEGIN { eval "foo()" }'

Reproduced in a -DDEBUGGING build on FreeBSD-12:

$ ./perl -e 'my sub foo {} BEGIN { eval "foo()" }'
Assertion failed: (PARENT_PAD_INDEX(name)), function Perl_find_lexical_cv, file op.c, line 13421.
Abort trap (core dumped)

Should we consider making this into a TODO-ed test in the test suite?

[tonycoz]

We don't need the BEGIN:

$ ./perl -Ilib -le 'use builtin "ceil"; sub foo { eval "ceil(1.5)" or die $@ } foo()'
perl: op.c:13423: Perl_find_lexical_cv: Assertion `PARENT_PAD_INDEX(name)' failed.
Aborted

I have a fix for this assertion which I'll pretty up for a PR.

Of course, normal lexical subs have a different problem, even without eval:

$ ./perl -le 'my sub foo { print "Foo" } BEGIN { foo() }'
Undefined subroutine &foo called at -e line 1.
BEGIN failed--compilation aborted at -e line 1.

which means the normal lexical sub won't be available in BEGIN anyway. This isn't a problem for lexical imports since those set the definition at compile-time.

This happens because normal lexical subs don't actually get a definition until runtime, when the clonecv op is executed:

$ ./perl -Ilib -MO=Concise -le 'my $x; my sub foo { print "Foo" } foo()'
a  <@> leave[1 ref] vKP/REFC ->(end)
1     <0> enter v ->2
-     <@> lineseq vK ->4
2        <0> introcv[&foo:4,5] v ->3
3        <0> clonecv[&foo:4,5] v ->4
4     <;> nextstate(main 1 -e:1) v:{ ->5
5     <0> padsv[$x:1,5] vM/LVINTRO ->6
6     <;> nextstate(main 5 -e:1) v:{ ->7
9     <1> entersub vKS ->a
-        <1> ex-list K ->9
7           <0> pushmark s ->8
-           <1> ex-rv2cv sK/1 ->-
8              <0> padcv[&foo:4,5] s ->9
-e syntax OK

I expect the fix for that is going to be moving the cloning for the first pad for a function rather than at runtime.