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Showing content from https://github.com/Perl/perl5/issues/19198 below:

Setting breakpoint on AUTOLOAD causes segmentation fault · Issue #19198 · Perl/perl5 · GitHub

Description
Setting a breakpoint on an AUTOLOAD under certain circumstances causes a segmentation fault. It's unclear what is the minimum amount of code required to reproduce the issue, but at the very least it seems to require:

  1. Two or more stack frames
  2. An eval block
  3. use vars for $AUTOLOAD
  4. Assigning $AUTOLOAD to another variable

I was able to reproduce this on both 5.32 and 5.34.

Steps to Reproduce

I was able to get this code to segfault, but it didn't happen every time.

package Test;

sub AUTOLOAD {
    use vars '$AUTOLOAD';
    my $sub = $AUTOLOAD;
    return 1;
}

package main;


sub test
{
    Test::test();
}

sub test_test
{
    eval { test() };
}

test_test();

Start the perl debugger with this code, then set a breakpoint on Test::AUTOLOAD, and continue. You should get this error message:

Signal SEGV at autoload_segv.pl line 14.
        main::test() called at autoload_segv.pl line 19
        eval {...} called at autoload_segv.pl line 19
        main::test_test() called at autoload_segv.pl line 22
Aborted (core dumped)

Expected behavior
It should break on the first line of the AUTOLOAD subroutine and not segfault.

Perl configuration

Summary of my perl5 (revision 5 version 34 subversion 0) configuration:
   
  Platform:
    osname=linux
    osvers=4.18.0-305.el8.x86_64
    archname=x86_64-linux
    uname='linux vm-mreisner.epic.com 4.18.0-305.el8.x86_64 #1 smp thu may 27 16:46:28 utc 2021 x86_64 x86_64 x86_64 gnulinux '
    config_args='-de -Dprefix=/home/mreisner/perl5/perlbrew/perls/perl-5.34.0 -Aeval:scriptdir=/home/mreisner/perl5/perlbrew/perls/perl-5.34.0/bin'
    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 -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'
    cppflags='-fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include'
    ccversion=''
    gccversion='8.4.1 20200928 (Red Hat 8.4.1-1)'
    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 /usr/lib64 /usr/local/lib64
    libs=-lpthread -ldl -lm -lcrypt -lutil -lc
    perllibs=-lpthread -ldl -lm -lcrypt -lutil -lc
    libc=libc-2.28.so
    so=so
    useshrplib=false
    libperl=libperl.a
    gnulibc_version='2.28'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs
    dlext=so
    d_dlsymun=undef
    ccdlflags='-Wl,-E'
    cccdlflags='-fPIC'
    lddlflags='-shared -O2 -L/usr/local/lib -fstack-protector-strong'


Characteristics of this binary (from libperl): 
  Compile-time options:
    HAS_TIMES
    PERLIO_LAYERS
    PERL_COPY_ON_WRITE
    PERL_DONT_CREATE_GVSV
    PERL_MALLOC_WRAP
    PERL_OP_PARENT
    PERL_PRESERVE_IVUV
    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 24 2021 16:29:28
  %ENV:
    PERLBREW_HOME="/home/mreisner/.perlbrew"
    PERLBREW_MANPATH="/home/mreisner/perl5/perlbrew/perls/perl-5.34.0/man"
    PERLBREW_PATH="/home/mreisner/perl5/perlbrew/bin:/home/mreisner/perl5/perlbrew/perls/perl-5.34.0/bin"
    PERLBREW_PERL="perl-5.34.0"
    PERLBREW_ROOT="/home/mreisner/perl5/perlbrew"
    PERLBREW_SHELLRC_VERSION="0.92"
    PERLBREW_VERSION="0.92"
  @INC:
    /home/mreisner/perl5/perlbrew/perls/perl-5.34.0/lib/site_perl/5.34.0/x86_64-linux
    /home/mreisner/perl5/perlbrew/perls/perl-5.34.0/lib/site_perl/5.34.0
    /home/mreisner/perl5/perlbrew/perls/perl-5.34.0/lib/5.34.0/x86_64-linux
    /home/mreisner/perl5/perlbrew/perls/perl-5.34.0/lib/5.34.0

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