Re: Undefining symbol tables and globs and things, oh my

How does perl know how to find $Yakkity::Yak::a after the package's symbol table is gone?

Because you have a compile-time reference to the typeglob associated with a, in the code print "a = $Yakkity::Yak::a\n"; undeffing the symbol table just removes a ref to the typeglob; the typeglob itslef continues to exist. At run-time, perl ops do not lookup variables in stashes; instead the ops contain a pointer to the typeglob.

Dave.

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Re^2: Undefining symbol tables and globs and things, oh my by ikegami (Patriarch) on Aug 10, 2005 at 13:56 UTC
To illustrate dave_the_m's and Bob9000's point, compare `#!/usr/bin/perl $Yakkity::Yak::a = 42; print "a = $Yakkity::Yak::a\n"; print "Undeffing symbol table\n"; undef %Yakkity::Yak::; print "a = $Yakkity::Yak::a\n"; __END__ a = 42 Undeffing symbol table a = 42` [download] with `#!/usr/bin/perl $Yakkity::Yak::a = 42; print "a = $Yakkity::Yak::a\n"; print "Undeffing symbol table\n"; undef %Yakkity::Yak::; print "a = ${'Yakkity::Yak::a'}\n"; # <- Hardcoded reference removed __END__ a = 42 Undeffing symbol table a =` [download] The last reference to $Yakkity::Yak::a keeps the symbol alive. If the reference to one built at run-time, the symbol disappears along with the table. Sorry, this post just explains what is seen, not how to work around it. Hopefully, someone has a solution.	[reply] [d/l] [select]

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Re^2: Undefining symbol tables and globs and things, oh my
by ikegami (Patriarch) on Aug 10, 2005 at 13:56 UTC

To illustrate dave_the_m's and Bob9000's point, compare

#!/usr/bin/perl
$Yakkity::Yak::a = 42;
print "a = $Yakkity::Yak::a\n";
print "Undeffing symbol table\n";
undef %Yakkity::Yak::;
print "a = $Yakkity::Yak::a\n";
__END__
a = 42
Undeffing symbol table
a = 42
[download]

with

#!/usr/bin/perl
$Yakkity::Yak::a = 42;
print "a = $Yakkity::Yak::a\n";
print "Undeffing symbol table\n";
undef %Yakkity::Yak::;
print "a = ${'Yakkity::Yak::a'}\n";  # <- Hardcoded reference removed
__END__
a = 42
Undeffing symbol table
a =
[download]

The last reference to $Yakkity::Yak::a keeps the symbol alive. If the reference to one built at run-time, the symbol disappears along with the table.

Sorry, this post just explains what is seen, not how to work around it. Hopefully, someone has a solution.

[reply]
[d/l]
[select]