perl - 从Perl脚本创建/引发SIGINT(Ctrl-C)-并导致从模具处理程序进入调试器进入步骤模式？

Question

我在尝试调试的Perl(在Linux下)中的一个相当复杂的程序遇到问题。我可以使用以下简单代码段(test.pl)模拟问题:

use warnings;
use strict;
use feature qw/say/;

my @testa = ();
my $numelems = 10000;

# populate array/list of arrays
for (my $ix = 0; $ix < $numelems; $ix++) {
  my @miniarr = ($ix, 1);
  push(@testa, \@miniarr);
}

say "Array is now " . scalar(@testa) . " elements long";

my $BADnumelems = $numelems + 2;
my $sum = 0;

# loop through array/list of arrays
for (my $ix = 0; $ix < $BADnumelems; $ix++) {
  my @minientry = @{$testa[$ix]};
  $sum += $minientry[0];
}

say "Sum of elements is $sum";

运行该程序将退出:

$ perl test.pl 
Array is now 10000 elements long
Can't use an undefined value as an ARRAY reference at test.pl line 22.

所以，现在我想调试它-但该错误导致程序死亡，并退出调试器:

$ perl -d test.pl 

Loading DB routines from perl5db.pl version 1.32
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main::(test.pl:6):  my @testa = ();
  DB<1> c
Array is now 10000 elements long
Can't use an undefined value as an ARRAY reference at test.pl line 22.
 at test.pl line 22
Debugged program terminated.  Use q to quit or R to restart,
  use o inhibit_exit to avoid stopping after program termination,
  h q, h R or h o to get additional info.  
  DB<1> p $sum

  DB<2> exit
$ 

然后，我发现 break on warning in debugger (PerlMonks);所以我尝试添加以下内容:

...
use feature qw/say/;

$SIG{__DIE__} = sub { my($signal) = @_; say "DIEhandler: $signal"; $DB::single = 1; };
$SIG{__WARN__} = sub { my($signal) = @_; say "WARNhandler: $signal"; $DB::single = 1; };

my @testa = ();
...

...但是这也会杀死调试器:

$ perl -d test.pl 

Loading DB routines from perl5db.pl version 1.32
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main::(test.pl:6):  $SIG{__DIE__} = sub { my($signal) = @_; say "DIEhandler: $signal"; $DB::single = 1; };
  DB<1> c
Array is now 10000 elements long
DIEhandler: Can't use an undefined value as an ARRAY reference at test.pl line 25.

Can't use an undefined value as an ARRAY reference at test.pl line 25.
Debugged program terminated.  Use q to quit or R to restart,
  use o inhibit_exit to avoid stopping after program termination,
  h q, h R or h o to get additional info.  

现在，我知道如果我用Ctrl-C中断程序-通常会导致调试器进入步进模式；否则，调试器将进入 Debug模式。例如，您可以设置 my $numelems = 100000000;，并在其循环时按Ctrl-C-并可以调试:

$ perl -d test.pl 

Loading DB routines from perl5db.pl version 1.32
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main::(test.pl:6):  $SIG{__DIE__} = sub { my($signal) = @_; say "DIEhandler: $signal"; $DB::single = 1; };
  DB<1> c
^Cmain::(test.pl:14):     my @miniarr = ($ix, 1);
  DB<1> p $ix
148607
  DB<2> q

现在，我可以 insert break point into source perl program:

...
for (my $ix = 0; $ix < $BADnumelems; $ix++) {
  $DB::single = 1;               ### <=== BREAK HERE
  my @minientry = @{$testa[$ix]};
...

但它在 $ix = 0时进入循环:

$ perl -d test.pl 

Loading DB routines from perl5db.pl version 1.32
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main::(test.pl:6):  $SIG{__DIE__} = sub { my($signal) = @_; say "DIEhandler: $signal"; $DB::single = 1; };
  DB<1> c
Array is now 10000 elements long
main::(test.pl:26):   my @minientry = @{$testa[$ix]};
  DB<1> p $ix
0
  DB<2> q

...并且我不想单步执行10000个元素来了解有问题的部分 :)
因此，我认为以下内容-如果有一种方法可以从Perl脚本本身中引发/生成/创建SIGINT(Ctrl-C)，那么我将能够从die处理程序中引发它，并希望在此过程中有所作为。进程终止之前的调试器。因此，我的问题是:

是否有可能从Perl脚本中引发SIGINT，该脚本会自行中断-如果是这样，怎么办？

如果以前的版本可行，是否可以在进程终止之前使用die handler中的Ctrl-C进入调试器步进模式？

如果以前的版本不可能-我必须在哪种可能性下进入die程序所在的调试器步进模式？

Answer 1

有了这些(尽管不确定我是否正确理解了:)的所有内容)，这要归功于这些:

Perl's Warn and Die Signals (PerlMonks)

How can I get around a 'die' call in a Perl library I can't modify?

只需使用 eval包装和 warn修改代码，如下所示:

...
# loop through array/list of arrays
for (my $ix = 0; $ix < $BADnumelems; $ix++) {
  eval {
    my @minientry;
    @minientry = @{$testa[$ix]};
    $sum += $minientry[0];
  }; # just this causes step into debugger at $ix = 10001
  warn $@ if $@; # this causes step into debugger at $ix=10000 (OK)
}
...

...然后调试器的工作方式如下:

$ perl -d test.pl 

Loading DB routines from perl5db.pl version 1.32
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main::(test.pl:6):  $SIG{__DIE__} = sub { my($signal) = @_; say "DIEhandler: $signal"; @_ = (); $DB::single = 1; };
  DB<1> c
Array is now 10000 elements long
DIEhandler: Can't use an undefined value as an ARRAY reference at test.pl line 27.

main::(test.pl:30):   warn $@ if $@; # this causes step into debugger at $ix=10000 (OK)
  DB<1> p $ix
10000
  DB<2> p @{$testa[$ix]}

  DB<3> p @{$testa[$ix-1]}
99991
  DB<4> p join("--", @{$testa[$ix]})

  DB<5> p join("--", @{$testa[$ix-1]})
9999--1
  DB<6> q

...就是直接进入有问题的行，这就是我想要的。

好吧，希望这对某人有帮助，
干杯!

编辑:也可能相关: Why do I need to localize $@ before using eval?