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Signal handlers aren't honoured at END time #15485

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p5pRT opened this issue Jul 29, 2016 · 6 comments
Open

Signal handlers aren't honoured at END time #15485

p5pRT opened this issue Jul 29, 2016 · 6 comments

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@p5pRT
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@p5pRT p5pRT commented Jul 29, 2016

Migrated from rt.perl.org#128774 (status was 'open')

Searchable as RT128774$

@p5pRT
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@p5pRT p5pRT commented Jul 29, 2016

From @leonerd

Created by @leonerd

The following test program produces unexpected results​:

$ perl -E '$SIG{ABRT} = sub { say "Caught" }; END { kill ABRT => $$ }'
Aborted

The installed signal handler is not invoked, leading to the standard behaviour
on SIGABRT rather than my custom handler.

This appears to have broken between 5.10 and 5.12​:

$ perl5.10.1 -E '$SIG{ABRT} = sub { say "Caught" }; END { kill ABRT => $$ }'
Caught

$ perl5.12.5 -E '$SIG{ABRT} = sub { say "Caught" }; END { kill ABRT => $$ }'
Aborted

Further discussion on #p5p has lead to​:

  18​:51 <alh> Oh hey, this worked up until 5.10.1, stopped working in 5.11.0

  19​:02 <alh> 01be072
  19​:03 <alh> ^ That's where the behaviour changed

Perl Info

Flags:
    category=core
    severity=low

Site configuration information for perl 5.22.2:

Configured by Debian Project at Sat Apr 30 12:20:51 UTC 2016.

Summary of my perl5 (revision 5 version 22 subversion 2) configuration:
   
  Platform:
    osname=linux, osvers=3.16.0, archname=x86_64-linux-gnu-thread-multi
    uname='linux localhost 3.16.0 #1 smp debian 3.16.0 x86_64 gnulinux '
    config_args='-Dusethreads -Duselargefiles -Dcc=x86_64-linux-gnu-gcc -Dcpp=x86_64-linux-gnu-cpp -Dld=x86_64-linux-gnu-gcc -Dccflags=-DDEBIAN -Wdate-time -D_FORTIFY_SOURCE=2 -g -O2 -fstack-protector-strong -Wformat -Werror=format-security -Dldflags= -Wl,-z,relro -Dlddlflags=-shared -Wl,-z,relro -Dcccdlflags=-fPIC -Darchname=x86_64-linux-gnu -Dprefix=/usr -Dprivlib=/usr/share/perl/5.22 -Darchlib=/usr/lib/x86_64-linux-gnu/perl/5.22 -Dvendorprefix=/usr -Dvendorlib=/usr/share/perl5 -Dvendorarch=/usr/lib/x86_64-linux-gnu/perl5/5.22 -Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl/5.22.2 -Dsitearch=/usr/local/lib/x86_64-linux-gnu/perl/5.22.2 -Dman1dir=/usr/share/man/man1 -Dman3dir=/usr/share/man/man3 -Dsiteman1dir=/usr/local/man/man1 -Dsiteman3dir=/usr/local/man/man3 -Duse64bitint -Dman1ext=1 -Dman3ext=3perl -Dpager=/usr/bin/sensible-pager -Uafs -Ud_csh -Ud_ualarm -Uusesfio -Uusenm -Ui_libutil -Uversiononly -DDEBUGGING=-g -Doptimize=-O2 -dEs -Duseshrplib -Dlibperl=libperl.so.5.22.
 2'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='x86_64-linux-gnu-gcc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fwrapv -fno-strict-aliasing -pipe -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-O2 -g',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fwrapv -fno-strict-aliasing -pipe -I/usr/local/include'
    ccversion='', gccversion='5.3.1 20160424', 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='x86_64-linux-gnu-gcc', ldflags =' -fstack-protector-strong -L/usr/local/lib'
    libpth=/usr/local/lib /usr/lib/gcc/x86_64-linux-gnu/5/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
    libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
    perllibs=-ldl -lm -lpthread -lc -lcrypt
    libc=libc-2.22.so, so=so, useshrplib=true, libperl=libperl.so.5.22
    gnulibc_version='2.22'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fPIC', lddlflags='-shared -L/usr/local/lib -fstack-protector-strong'

Locally applied patches:
    DEBPKG:debian/cpan_definstalldirs - Provide a sensible INSTALLDIRS default for modules installed from CPAN.
    DEBPKG:debian/db_file_ver - http://bugs.debian.org/340047 Remove overly restrictive DB_File version check.
    DEBPKG:debian/doc_info - Replace generic man(1) instructions with Debian-specific information.
    DEBPKG:debian/enc2xs_inc - http://bugs.debian.org/290336 Tweak enc2xs to follow symlinks and ignore missing @INC directories.
    DEBPKG:debian/errno_ver - http://bugs.debian.org/343351 Remove Errno version check due to upgrade problems with long-running processes.
    DEBPKG:debian/libperl_embed_doc - http://bugs.debian.org/186778 Note that libperl-dev package is required for embedded linking
    DEBPKG:fixes/respect_umask - Respect umask during installation
    DEBPKG:debian/writable_site_dirs - Set umask approproately for site install directories
    DEBPKG:debian/extutils_set_libperl_path - EU:MM: set location of libperl.a under /usr/lib
    DEBPKG:debian/no_packlist_perllocal - Don't install .packlist or perllocal.pod for perl or vendor
    DEBPKG:debian/fakeroot - Postpone LD_LIBRARY_PATH evaluation to the binary targets.
    DEBPKG:debian/instmodsh_doc - Debian policy doesn't install .packlist files for core or vendor.
    DEBPKG:debian/ld_run_path - Remove standard libs from LD_RUN_PATH as per Debian policy.
    DEBPKG:debian/libnet_config_path - Set location of libnet.cfg to /etc/perl/Net as /usr may not be writable.
    DEBPKG:debian/mod_paths - Tweak @INC ordering for Debian
    DEBPKG:debian/prune_libs - http://bugs.debian.org/128355 Prune the list of libraries wanted to what we actually need.
    DEBPKG:fixes/net_smtp_docs - [rt.cpan.org #36038] http://bugs.debian.org/100195 Document the Net::SMTP 'Port' option
    DEBPKG:debian/perlivp - http://bugs.debian.org/510895 Make perlivp skip include directories in /usr/local
    DEBPKG:debian/deprecate-with-apt - http://bugs.debian.org/747628 Point users to Debian packages of deprecated core modules
    DEBPKG:debian/squelch-locale-warnings - http://bugs.debian.org/508764 Squelch locale warnings in Debian package maintainer scripts
    DEBPKG:debian/skip-upstream-git-tests - Skip tests specific to the upstream Git repository
    DEBPKG:debian/patchlevel - http://bugs.debian.org/567489 List packaged patches for 5.22.2-1 in patchlevel.h
    DEBPKG:debian/skip-kfreebsd-crash - http://bugs.debian.org/628493 [perl #96272] Skip a crashing test case in t/op/threads.t on GNU/kFreeBSD
    DEBPKG:fixes/document_makemaker_ccflags - http://bugs.debian.org/628522 [rt.cpan.org #68613] Document that CCFLAGS should include $Config{ccflags}
    DEBPKG:debian/find_html2text - http://bugs.debian.org/640479 Configure CPAN::Distribution with correct name of html2text
    DEBPKG:debian/perl5db-x-terminal-emulator.patch - http://bugs.debian.org/668490 Invoke x-terminal-emulator rather than xterm in perl5db.pl
    DEBPKG:debian/cpan-missing-site-dirs - http://bugs.debian.org/688842 Fix CPAN::FirstTime defaults with nonexisting site dirs if a parent is writable
    DEBPKG:fixes/memoize_storable_nstore - [rt.cpan.org #77790] http://bugs.debian.org/587650 Memoize::Storable: respect 'nstore' option not respected
    DEBPKG:debian/regen-skip - Skip a regeneration check in unrelated git repositories
    DEBPKG:debian/makemaker-pasthru - http://bugs.debian.org/758471 Pass LD settings through to subdirectories
    DEBPKG:fixes/pod_man_reproducible_date - http://bugs.debian.org/759405 Support POD_MAN_DATE in Pod::Man for the left-hand footer
    DEBPKG:debian/locale-robustness - http://bugs.debian.org/782068 [perl #124310] Make t/run/locale.t survive missing locales masked by LC_ALL
    DEBPKG:fixes/podman-utc - http://bugs.debian.org/780259 Make the embedded date from Pod::Man reproducible
    DEBPKG:fixes/podman-utc-docs - http://bugs.debian.org/780259 Documentation and test suite updates for UTC fix
    DEBPKG:fixes/podman-empty-date - http://bugs.debian.org/780259 Support an empty POD_MAN_DATE environment variable
    DEBPKG:fixes/podman-pipe - http://bugs.debian.org/777405 Better errors for man pages from standard input
    DEBPKG:debian/pod2man-customized - Update porting/customized.dat for pod2man modifications
    DEBPKG:debian/makemaker-manext - http://bugs.debian.org/247370 Make EU::MakeMaker honour MANnEXT settings in generated manpage headers
    DEBPKG:debian/makemaker_customized - Update t/porting/customized.dat for files patched in Debian
    DEBPKG:debian/do-not-record-build-date - [6baa8db] http://bugs.debian.org/774422 [perl #125830] Allow overriding the compile time in "perl -V" output
    DEBPKG:fixes/podman-source-date-epoch - http://bugs.debian.org/801621 Make Pod::Man honor the SOURCE_DATE_EPOCH environment variable
    DEBPKG:fixes/podman-source-date-epoch-cleanups - http://bugs.debian.org/801621 Coding style and documentation for SOURCE_EPOCH_DATE
    DEBPKG:fixes/podman-source-date-epoch-testfix - http://bugs.debian.org/807086 Guard for building with SOURCE_DATE_EPOCH or POD_MAN_DATE set
    DEBPKG:debian/devel-ppport-reproducibility - http://bugs.debian.org/801523 Sort the list of XS code files when generating RealPPPort.xs
    DEBPKG:fixes/encode-unicode-bom - http://bugs.debian.org/798727 [rt.cpan.org #107043] Address https://rt.cpan.org/Public/Bug/Display.html?id=107043
    DEBPKG:debian/encode-unicode-bom-doc - http://bugs.debian.org/798727 Document Debian backport of Encode::Unicode fix
    DEBPKG:debian/kfreebsd-softupdates - http://bugs.debian.org/796798 Work around Debian Bug#796798
    DEBPKG:fixes/autodie-scope - http://bugs.debian.org/798096 Fix a scoping issue with "no autodie" and the "system" sub
    DEBPKG:debian/debugperl-compat-fix - [perl #127212] http://bugs.debian.org/810326 Disable PERL_TRACK_MEMPOOL for debugging builds
    DEBPKG:fixes/crosscompile-no-targethost - [perl #127234] Fix the Configure escape with usecrosscompile but no targethost
    DEBPKG:fixes/podlators-no-encode - [rt.cpan.org #111156] Degrade gracefully if utf8 is requested but Encode is not available
    DEBPKG:debian/cross-time-hires - [rt.cpan.org #111391] Add an environment variable to skip running configuration probes
    DEBPKG:fixes/encode-unicode-pod - Unicode.pm: Fix POD error
    DEBPKG:fixes/memoize-pod - [rt.cpan.org #89441] Fix POD errors in Memoize
    DEBPKG:fixes/ok-pod - Added encoding for pod.
    DEBPKG:debian/hurd-softupdates - http://bugs.debian.org/822735 Fix t/op/stat.t failures on hurd


@INC for perl 5.22.2:
    /home/leo/lib/perl5/x86_64-linux-gnu-thread-multi
    /home/leo/lib/perl5
    /etc/perl
    /usr/local/lib/x86_64-linux-gnu/perl/5.22.2
    /usr/local/share/perl/5.22.2
    /usr/lib/x86_64-linux-gnu/perl5/5.22
    /usr/share/perl5
    /usr/lib/x86_64-linux-gnu/perl/5.22
    /usr/share/perl/5.22
    /usr/local/lib/site_perl
    /usr/lib/x86_64-linux-gnu/perl-base
    .


Environment for perl 5.22.2:
    HOME=/home/leo
    LANG=en_GB.UTF-8
    LANGUAGE=en_GB:en
    LD_LIBRARY_PATH=/home/leo/lib
    LOGDIR (unset)
    PATH=/home/leo/bin:/home/leo/bin:/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games
    PERL5LIB=/home/leo/lib/perl5
    PERL_BADLANG (unset)
    PERL_MB_OPT=install_base=~
    PERL_MM_OPT=INSTALL_BASE=~
    SHELL=/bin/bash

@p5pRT
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@p5pRT p5pRT commented Jul 30, 2016

From zefram@fysh.org

Paul LeoNerd Evans wrote​:

19​:02 <alh> 01be072
19​:03 <alh> ^ That's where the behaviour changed

The change is to unhook at the C level all Perl signal handlers before
interpreter destruction. There's a valid rationale for that, but it's
happening too early. It shouldn't happen before END blocks, in which
everything in the interpreter is still operable and the Perl language is
still expected to be well behaved. It could happen just before global
destruction, or just after.

-zefram

@p5pRT
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@p5pRT p5pRT commented Jul 30, 2016

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

@p5pRT
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@p5pRT p5pRT commented Jul 30, 2016

From @leonerd

On Sat, 30 Jul 2016 05​:47​:58 +0100
Zefram <zefram@​fysh.org> wrote​:

It shouldn't happen before END blocks, in which
everything in the interpreter is still operable and the Perl language
is still expected to be well behaved. It could happen just before
global destruction, or just after.

I have no great opinion on which side of GD this happens. Obviously it
would be nice if the perl-visible things were still valid even during
GD, but if some implementation reason makes that a lot harder to
implement, then I could live with perl documenting "Signal handlers may
not apply during GD", as already GD is a weird time.

--
Paul "LeoNerd" Evans

leonerd@​leonerd.org.uk | https://metacpan.org/author/PEVANS
http​://www.leonerd.org.uk/ | https://www.tindie.com/stores/leonerd/

@p5pRT
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@p5pRT p5pRT commented Jul 30, 2016

From @Leont

On Sat, Jul 30, 2016 at 6​:47 AM, Zefram <zefram@​fysh.org> wrote​:

The change is to unhook at the C level all Perl signal handlers before
interpreter destruction. There's a valid rationale for that, but it's
happening too early. It shouldn't happen before END blocks, in which
everything in the interpreter is still operable and the Perl language is
still expected to be well behaved.

Agreed.

It could happen just before global
destruction, or just after.

I would argue before. Global destruction is unpredictable enough as it is,
adding signals to that will only make it worse. I think that in the
non-object phase it might even segfault because the CV doesn't exist
anymore. One could argue to unhook it right after global object destruction
(so well before global non-object destruction) though.

Leon

@p5pRT
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@p5pRT p5pRT commented Aug 1, 2016

From @xsawyerx

On 07/30/2016 04​:47 PM, Leon Timmermans wrote​:

On Sat, Jul 30, 2016 at 6​:47 AM, Zefram <zefram@​fysh.org
<mailto​:zefram@​fysh.org>> wrote​:

The change is to unhook at the C level all Perl signal handlers before
interpreter destruction\.  There's a valid rationale for that\, but it's
happening too early\.  It shouldn't happen before END blocks\, in which
everything in the interpreter is still operable and the Perl
language is
still expected to be well behaved\. 

Agreed.

It could happen just before global
destruction\, or just after\.

I would argue before. Global destruction is unpredictable enough as it
is, adding signals to that will only make it worse. I think that in
the non-object phase it might even segfault because the CV doesn't
exist anymore. One could argue to unhook it right after global object
destruction (so well before global non-object destruction) though.

I appreciate Paul's comment on this​: "[...] as already GD is a weird
time.". :)

What would worry me is that if it's after GD, people might depend on it
and now refactoring this, cleaning it up, optimizing it - those actions
might conflict. I would rather keep it before unless there's a good[1]
reason.

[1] "I want" should probably not be a good enough reason.

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