如何编写在eval块中不触发的SIG {__ DIE__}处理程序? [英] How can I write a SIG{__DIE__} handler that does not trigger in eval blocks?

问题描述

根据 perldoc -f die $ SIG {__ DIE __}

尽管此功能仅在程序退出前运行，但当前并非如此: $ SIG {__ DIE __} 钩子即使在逃避的块/字符串中也被调用！如果希望在这种情况下该钩子不执行任何操作，请将 die @_ if $ ^ S; 作为处理程序的第一行(请参阅perlvar中的 $ ^ S ).因为这会在远处促进奇怪的动作，所以这种反直觉的行为可能会在将来的版本中得到解决.

Although this feature was to be run only right before your program was to exit, this is not currently so: the $SIG{__DIE__} hook is currently called even inside evaled blocks/strings! If one wants the hook to do nothing in such situations, put die @_ if $^S; as the first line of the handler (see $^S in perlvar). Because this promotes strange action at a distance, this counterintuitive behavior may be fixed in a future release.

因此，让我们来看一个基本的信号处理程序，该处理程序将通过 eval {die 42} ，

So let's take a basic signal handler which will trigger with eval { die 42 },

package Stupid::Insanity {
  BEGIN { $SIG{__DIE__} = sub { print STDERR "ERROR"; exit; }; }
}

我们通过以下方式确保这一点

We make this safe with

package Stupid::Insanity {
  BEGIN { $SIG{__DIE__} = sub { return if $^S; print STDERR "ERROR"; exit; }; }
}

现在，此操作将不通过 eval {die 42} 触发，但是当相同的代码位于 BEGIN {} 中时将触发像

Now this will NOT trigger with eval { die 42 }, but it will trigger when that same code is in a BEGIN {} block like

BEGIN { eval { die 42 } }

这似乎有些晦涩，但它是真实世界，因为您可以看到它被在此方法中使用(其中require 失败，并且被 eval )捕获，或者在我的情况下，特别是在

This may seem obscure but it's rather real-world as you can see it being used in this method here (where the require fails and it's caught by an eval), or in my case specifically here Net::DNS::Parameters. You may think you can catch the compiler phase too, like this,

BEGIN {
  $SIG{__DIE__} = sub {
    return if ${^GLOBAL_PHASE} eq 'START' || $^S;
    print STDERR "ERROR";
    exit;
  };
}

哪种方法适用于上述情况，但是不能适用于其中包含BEGIN语句的文档的要求

Which will work for the above case, but alas it will NOT work for a require of a document which has a BEGIN statement in it,

eval "BEGIN { eval { die 42 } }";

总有办法解决此问题并编写一个不会干扰 eval 的 $ SIG {__ DIE __} 处理程序吗?

Is there anyway to solve this problem and write a $SIG{__DIE__} handler that doesn't interfere with eval?

推荐答案

检查 caller(1)

使用 [caller(1)]-> [3] eq'(eval)'

return if [caller(1)]->[3] eq '(eval)' || ${^GLOBAL_PHASE} eq 'START' || $^S;

抓取整个调用堆栈

您可以抓取整个堆栈，并确保您不与...进行深入评估，

Crawl entire call stack

You can crawl the entire stack and be sure you're NOT deeply in an eval with,

for ( my $i = 0; my @frame = caller($i); $i++ ) {
  return if $frame[3] eq '(eval)'
}

---

是的，这完全是精神错乱.感谢 irc.freenode.net/#perl 上的mst作为指针.

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