feature class: attempting to create an object of an incomplete class asserts

[tonycoz]

Module:

Description

Perl crashes with an assertion (debugging builds) or an unhelpful message (non-debugging) if you attempt to create an object of an incomplete class.

Steps to Reproduce

$ ~/perl/blead/bin/perl5.39.9 -Mfeature=class -e 'eval "class Foo {"; Foo->new'
class is experimental at (eval 1) line 1.
perl5.39.9: class.c:170: injected_constructor: Assertion `aux->xhv_class_initfields_cv' failed.
Aborted

Expected behavior

A helpful error message.

Perl configuration

# perl -V output goes here
Summary of my perl5 (revision 5 version 39 subversion 9) configuration:
  Commit id: bc2427acad39d9b52d84a987047ca10c3c2f7b77
  Platform:
    osname=linux
    osvers=6.1.0-17-amd64
    archname=x86_64-linux
    uname='linux venus 6.1.0-17-amd64 #1 smp preempt_dynamic debian 6.1.69-1 (2023-12-30) x86_64 gnulinux '
    config_args='-des -Dusedevel -DDEBUGGING -Dprefix=/home/tony/perl/blead'
    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='-O2 -g'
    cppflags='-fwrapv -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include'
    ccversion=''
    gccversion='12.2.0'
    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 -lgdbm -ldl -lm -lcrypt -lutil -lc -lgdbm_compat
    perllibs=-lpthread -ldl -lm -lcrypt -lutil -lc
    libc=/lib/x86_64-linux-gnu/libc.so.6
    so=so
    useshrplib=false
    libperl=libperl.a
    gnulibc_version='2.36'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs
    dlext=so
    d_dlsymun=undef
    ccdlflags='-Wl,-E'
    cccdlflags='-fPIC'
    lddlflags='-shared -O2 -g -L/usr/local/lib -fstack-protector-strong'


Characteristics of this binary (from libperl): 
  Compile-time options:
    DEBUGGING
    HAS_LONG_DOUBLE
    HAS_STRTOLD
    HAS_TIMES
    PERLIO_LAYERS
    PERL_COPY_ON_WRITE
    PERL_DONT_CREATE_GVSV
    PERL_HASH_FUNC_SIPHASH13
    PERL_HASH_USE_SBOX32
    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 Mar  4 2024 11:01:24
  %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:
    /home/tony/perl/blead/lib/site_perl/5.39.9/x86_64-linux
    /home/tony/perl/blead/lib/site_perl/5.39.9
    /home/tony/perl/blead/lib/5.39.9/x86_64-linux
    /home/tony/perl/blead/lib/5.39.9

[jkeenan]

Perl crashes with an assertion (debugging builds) or an unhelpful message (non-debugging) if you attempt to create an object of an incomplete class.

Is this the "unhelpful message" you get in non-debugging builds?

$ ./bin/perl -Ilib -Mfeature=class -e 'eval "class Foo {"; Foo->new'
class is experimental at (eval 1) line 1.
Not a CODE reference at -e line 1.

(From a non-debugging build of perl-5.39.5 on Linux; similar output at today's HEAD on blead.)

[jkeenan]

The "unhelpful" error message on regular build, as well as the crash on debugging build, appear to have first appeared at commit 080297a back in September.

$ git show --format=fuller 080297a1c0
commit 080297a1c054c421f95cf78ca4f58a960f1d124f
Author:     Tony Cook <tony@develop-help.com>
AuthorDate: Tue Sep 5 16:37:48 2023 +1000
Commit:     Tony Cook <tony@develop-help.com>
CommitDate: Fri Sep 15 09:10:37 2023 +1000

    class: don't leak the default initialiser ops if they're forbidden
...

$  uname -mrs; gcc --version | head -n 1
Linux 6.5.0-27-generic x86_64
gcc (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0

$ sh ./Configure -des -Dusedevel -Dcc=gcc && make

$ git describe
v5.39.2-120-g37f50f0f03
$ ./perl -Ilib -Mfeature=class -e 'eval "class Foo {"; Foo->new'
class is experimental at (eval 1) line 1.
Undefined subroutine called at -e line 1.

$ git describe; ./perl -Ilib -Mfeature=class -e 'eval "class Foo {"; Foo->new'
v5.39.2-121-g080297a1c0
class is experimental at (eval 1) line 1.
Not a CODE reference at -e line 1.


$ sh ./Configure -des -Dusedevel -Dcc=gcc -DDEBUGGING && make

$ git describe; ./perl -Ilib -Mfeature=class -e 'eval "class Foo {"; Foo->new'
v5.39.2-120-g37f50f0f03
class is experimental at (eval 1) line 1.
Undefined subroutine called at -e line 1.

$ git describe; ./perl -Ilib -Mfeature=class -e 'eval "class Foo {"; Foo->new'
v5.39.2-121-g080297a1c0
class is experimental at (eval 1) line 1.
perl: class.c:170: injected_constructor: Assertion `aux->xhv_class_initfields_cv' failed.
Aborted (core dumped)

I think this qualifies as a Release Blocker; so labeling.