在perl中检测声明的包变量

我尽力了,甚至试着问 eval STRING 是否 $main::f 已通过 our 或 my . (这需要复制、关闭和稍后恢复 STDERR 一旦您更改了包,这些声明在临时切换中就不再可见了。

下面的技术将检测 $f

use vars qw/ $f /;

代码如下:

package MyModule;

use warnings;
use strict;

# using $f will confuse the compiler, generating
# warnings of 'Variable "%f" is not available'
# although we're going for $main::f
my $__f = "from MyModule";

my %IMPORT_OK = (
  '$f' => [f => \$__f],
);

sub import {
  my($pkg,@imports) = @_;
  my $callpkg = caller;

  die "I don't speak your dirty Pig-Latin"
    if $callpkg !~ /\A\w+(::\w+)*\z/ ||
       grep !/\A[\$@%]\w+\z/, @imports;

  foreach my $name (@imports) {
    my($sym,$ref) = @{ $IMPORT_OK{$name} || [] };
    die "unknown import: $name" unless $sym;

    open my $saverr, ">&", \*STDERR or die "dup STDERR: $!";
    close STDERR;

    my $declared = eval qq{
      package $callpkg;
      my(undef)=$name;
      1;
    };

    open STDERR, ">&", $saverr or print "restore STDERR: $!";
    die "${callpkg}::$sym already exists" if $declared;

    {
      no strict 'refs';
      *{$callpkg . "::" . $sym} = $ref;
    }
  }
}

1;

摘要

在这一点上,经过相当广泛的研究,我坚定地认为,在一个名为“X”的符号表条目被声明但没有被赋值的情况下,它是 glob中的哪些引用类型实际上是在使用Devel::stuff的深度探测时声明的。

1. 完全没有声明X(符号表条目不存在)

2. 声明了X,并将一些glob类型实际分配给了。

   • 你呢 可以 找出哪些glob类型被分配了,哪些没有

   • 但是,你 不能 找出哪些未分配给glob的类型是声明的和未分配的,哪些是根本没有声明的。

   换言之 our $f = 1; our @f; $main::f 是标量; 但我们无法判断 @f 和 %f 是否被宣布-这是无法区分的 our $f = 1; our %f; .

原始答案

好吧,区分标量和子例程的非常有限的解决方案是使用UNIVERSAL::can:

use strict; 
our $f; 
sub g {};
foreach my $n ("f","g","h") {
    # First off, check if we are in main:: namespace, 
    # and if we are, that we are a scalar
    no strict "refs"; 
    next unless exists $main::{$n} && *{"main::$n"}; 
    use strict "refs"; 
    # Now, we are a declared scalr, unless we are a executable subroutine:
    print "Declared: \$$n\n" unless UNIVERSAL::can("main",$n)
}

Declared: $f

请注意 {SCALAR} @A 和 %H 如果我声明它们并添加到循环中。

我尝试了brian d foy在“精通perl”第8章中的方法,但不知怎么的,它无法用于标量、哈希或数组;但正如draegtun在下面提到的,它适用于子程序或变量 已经分配给 :

> perl5.8 -we '{use strict; use Data::Dumper; 
  our $f; sub g {}; our @A=(); sub B{}; our $B; our %H=();
  foreach my $n ("f","g","h","STDOUT","A","H","B") {
      no strict "refs"; 
      next unless exists $main::{$n};
      print "Exists: $n\n";
      if ( defined ${$n}) { print "Defined scalar: $n\n"}; 
      if ( defined @{$n}) { print "Defined ARRAY: $n\n"}; 
      if ( defined %{$n}) { print "Defined HASH: $n\n"}; 
      if ( defined &{$n}) { print "Defined SUB: $n\n"}; 
      use strict "refs";}}'       

Exists: f
Exists: g
Defined SUB: g           <===== No other defined prints worked
Exists: STDOUT
Exists: A
Exists: H
Exists: B
Defined SUB: B           <===== No other defined prints worked

旧的perl(5.10之前的版本)在标量槽中总是有一些东西。

在较新的perl上,当您 试着做*FOO{SCALAR}。

不过,您可以使用B内省模块检查标量插槽:

# package main;
our $f;
sub f {}
sub g {}

use B;
use 5.010;
if ( ${ B::svref_2object(\*f)->SV } ) {
   say "f: Thar be a scalar tharrr!";
}
if ( ${ B::svref_2object(\*g)->SV } ) {
   say "g: Thar be a scalar tharrr!";
}

1;

say 'g() defined in main' if defined &{'main::g'};

不幸的是,相同的方法仅适用于已赋值的包变量:

our $f = 1;
say '$f defined with value in main' if defined ${'main::f'};

/I3az公司/

Devel::Peek似乎能够区分标量插槽中已使用和未使用的内容:

use strict;
use warnings;
use Devel::Peek;

our $f;
sub f { }
sub g { }

Dump(*f);
Dump(*g);

SV = PVGV(0x187360c) at 0x182c0f4
  REFCNT = 3
  FLAGS = (MULTI,IN_PAD)
  NAME = "f"
  NAMELEN = 1
  GvSTASH = 0x24a084    "main"
  GP = 0x1874bd4
    SV = 0x182c0a4
    REFCNT = 1
    IO = 0x0
    FORM = 0x0  
    AV = 0x0
    HV = 0x0
    CV = 0x24a234
    CVGEN = 0x0
    LINE = 6
    FILE = "c:\temp\foo.pl"
    FLAGS = 0xa
    EGV = 0x182c0f4 "f"
SV = PVGV(0x187362c) at 0x18514dc
  REFCNT = 2
  FLAGS = (MULTI,IN_PAD)
  NAME = "g"
  NAMELEN = 1
  GvSTASH = 0x24a084    "main"
  GP = 0x1874cbc
    SV = 0x0
    REFCNT = 1
    IO = 0x0
    FORM = 0x0  
    AV = 0x0
    HV = 0x0
    CV = 0x1865234
    CVGEN = 0x0
    LINE = 8
    FILE = "c:\temp\foo.pl"
    FLAGS = 0xa
    EGV = 0x18514dc "g"

兴趣线在下面 GP = *g SV = 0x0 . 不幸的是,似乎没有一个程序化的方法来获取这些信息。一种钝器方法是捕捉 Dump() 然后分析它。