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Sub::Uplevel (3)
  • >> Sub::Uplevel (3) ( Разные man: Библиотечные вызовы )
  •  

    NAME

    Sub::Uplevel - apparently run a function in a higher stack frame
     
    

    SYNOPSIS

      use Sub::Uplevel;
    
    

      sub foo {
          print join " - ", caller;
      }
    
    

      sub bar {
          uplevel 1, \&foo;
      }
    
    

      #line 11
      bar();    # main - foo.plx - 11
    
    
     

    DESCRIPTION

    Like Tcl's uplevel() function, but not quite so dangerous. The idea is just to fool caller(). All the really naughty bits of Tcl's uplevel() are avoided.

    THIS IS NOT THE SORT OF THING YOU WANT TO DO EVERYDAY

    uplevel
      uplevel $num_frames, \&func, @args;
    
    

    Makes the given function think it's being executed $num_frames higher than the current stack level. So when they use caller($frames) it will actually caller($frames + $num_frames) for them.

    "uplevel(1, \&some_func, @_)" is effectively "goto &some_func" but you don't immediately exit the current subroutine. So while you can't do this:

        sub wrapper {
            print "Before\n";
            goto &some_func;
            print "After\n";
        }
    
    

    you can do this:

        sub wrapper {
            print "Before\n";
            my @out = uplevel 1, &some_func;
            print "After\n";
            return @out;
        }
    
    
     

    EXAMPLE

    The main reason I wrote this module is so I could write wrappers around functions and they wouldn't be aware they've been wrapped.

        use Sub::Uplevel;
    
    

        my $original_foo = \&foo;
    
    

        *foo = sub {
            my @output = uplevel 1, $original_foo;
            print "foo() returned:  @output";
            return @output;
        };
    
    

    If this code frightens you you should not use this module.  

    BUGS and CAVEATS

    Sub::Uplevel must be used as early as possible in your program's compilation.

    Well, the bad news is uplevel() is about 5 times slower than a normal function call. XS implementation anyone?

    Blows over any CORE::GLOBAL::caller you might have (and if you do, you're just sick).  

    HISTORY

    Those who do not learn from HISTORY are doomed to repeat it.

    The lesson here is simple: Don't sit next to a Tcl programmer at the dinner table.  

    THANKS

    Thanks to Brent Welch, Damian Conway and Robin Houston.  

    AUTHOR

    Michael G Schwern <schwern@pobox.com>  

    LICENSE

    Copyright by Michael G Schwern

    This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

    See http://www.perl.com/perl/misc/Artistic.html  

    SEE ALSO

    PadWalker (for the similar idea with lexicals), Hook::LexWrap, Tcl's uplevel() at http://www.scriptics.com/man/tcl8.4/TclCmd/uplevel.htm


     

    Index

    NAME
    SYNOPSIS
    DESCRIPTION
    EXAMPLE
    BUGS and CAVEATS
    HISTORY
    THANKS
    AUTHOR
    LICENSE
    SEE ALSO


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