考虑这个小的 perl 程序,test.pl
:
#!/usr/bin/env perl
use warnings;
use strict;
use Number::Format qw(:subs); # sudo perl -MCPAN -e 'install Number::Format'
my $tstr = "";
my $numFormatter = new Number::Format();
for (my $ix=0; $ix<20; $ix++) {
$tstr = $tstr . int(rand(10));
my $ftstr = $numFormatter->format_number($tstr, 2, 1);
print "ix: $ix ; in: $tstr ; out: $ftstr\n";
}
如果我运行它,它会失败并显示错误。如果我在 Perl 调试器中运行它,使用
perl -d
,它也失败并出现错误:$ perl -d test.pl
Loading DB routines from perl5db.pl version 1.39_10
Editor support available.
Enter h or 'h h' for help, or 'man perldebug' for more help.
main::(test.pl:6): my $tstr = "";
DB<1> c
ix: 0 ; in: 6 ; out: 6.00
ix: 1 ; in: 63 ; out: 63.00
ix: 2 ; in: 637 ; out: 637.00
ix: 3 ; in: 6379 ; out: 6,379.00
ix: 4 ; in: 63790 ; out: 63,790.00
ix: 5 ; in: 637906 ; out: 637,906.00
ix: 6 ; in: 6379062 ; out: 6,379,062.00
ix: 7 ; in: 63790624 ; out: 63,790,624.00
ix: 8 ; in: 637906246 ; out: 637,906,246.00
ix: 9 ; in: 6379062467 ; out: 6,379,062,467.00
ix: 10 ; in: 63790624671 ; out: 63,790,624,671.00
ix: 11 ; in: 637906246715 ; out: 637,906,246,715.00
ix: 12 ; in: 6379062467152 ; out: 6,379,062,467,152.00
ix: 13 ; in: 63790624671522 ; out: 63,790,624,671,522.00
round() overflow. Try smaller precision or use Math::BigFloat at test.pl line 11.
at /usr/local/share/perl/5.18.2/Number/Format.pm line 535.
Number::Format::round('Number::Format=HASH(0x9d0b6cc)', 637906246715226, 2) called at /usr/local/share/perl/5.18.2/Number/Format.pm line 601
Number::Format::format_number('Number::Format=HASH(0x9d0b6cc)', 637906246715226, 2, 1) called at test.pl line 11
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 $ix
DB<2>
...但是当它失败时,它不会在失败的行“停止”,如
gdb
使用 C 程序可能会这样做 - 程序再次终止,因此我不再需要检查上下文变量。当然,像这样的循环可能会运行数千次,这就是为什么在有问题的行上设置断点并执行
c
的原因。手动继续在这里不会有太大帮助......有没有办法让 Perl 调试器在出现错误/异常时中断程序,从而保留局部变量上下文,以便检查那里的变量?
最佳答案
将违规行包裹在 eval
中并设置 $DB::single
当$@
设置:
#!/usr/bin/env perl
use warnings;
use strict;
use Number::Format qw(:subs); # sudo perl -MCPAN -e 'install Number::Format'
my $tstr = "";
my $numFormatter = new Number::Format();
for (my $ix=0; $ix<20; $ix++) {
$tstr = $tstr . int(rand(10));
my $ftstr = eval { $numFormatter->format_number($tstr, 2, 1); };
$DB::single = 1 if $@;
print "ix: $ix ; in: $tstr ; out: $ftstr\n";
}
然后,
% perl -d test.pl
Loading DB routines from perl5db.pl version 1.49
Editor support available.
Enter h or 'h h' for help, or 'man perldebug' for more help.
main::(test.pl:6): my $tstr = "";
DB<1> r
ix: 0 ; in: 7 ; out: 7.00
ix: 1 ; in: 71 ; out: 71.00
ix: 2 ; in: 715 ; out: 715.00
ix: 3 ; in: 7153 ; out: 7,153.00
ix: 4 ; in: 71537 ; out: 71,537.00
ix: 5 ; in: 715379 ; out: 715,379.00
ix: 6 ; in: 7153794 ; out: 7,153,794.00
ix: 7 ; in: 71537941 ; out: 71,537,941.00
ix: 8 ; in: 715379417 ; out: 715,379,417.00
ix: 9 ; in: 7153794174 ; out: 7,153,794,174.00
ix: 10 ; in: 71537941740 ; out: 71,537,941,740.00
ix: 11 ; in: 715379417408 ; out: 715,379,417,408.00
ix: 12 ; in: 7153794174086 ; out: 7,153,794,174,086.00
ix: 13 ; in: 71537941740864 ; out: 71,537,941,740,864.00
main::(test.pl:13): print "ix: $ix ; in: $tstr ; out: $tstr\n";
DB<1> print $tstr
715379417408646
DB<2>
有没有搞错??
神奇的背后有两个原则:
要捕获异常,请使用
eval BLOCK
构造。这会将异常存储在 $@
中。多变的。如 $@
不是空字符串,抛出异常。请注意,上面的代码虽然惯用,但并不完全正确;如果抛出的异常是字符串 0
,它会被忽略(因为 if 0
会是假的)。 Perl 中的异常处理很复杂。 Try::Tiny
有一个很好的讨论。现在异常不再是致命的,如何停止调试器?有很多方法可以做到这一点。此示例使用
$DB::single
变量,当为真时,通知调试器停止。缺点是您必须编辑代码才能实现此行为。另一种选择是set a breakpoint with a condition :% perl -d test.pl
Loading DB routines from perl5db.pl version 1.49
Editor support available.
Enter h or 'h h' for help, or 'man perldebug' for more help.
main::(test.pl:6): my $tstr = "";
DB<1> b 11 $@ ne ''
DB<2> r
[... output as above ...]
main::(test.pl:11): my $ftstr = eval { $numFormatter->format_number($tstr, 2, 1); };
DB<2> p $tstr
3247014520717436
见 perl debugger documentation更多。
关于Perl 调试器 - 出错时中断(异常)?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/39898091/