load base packages based on nonexistent $VERSION

	Message-ID: <sfcsob2m5ub.fsf@dubravka.in-berlin.de>
	Subject: Re: base.pm flaw

p4raw-id: //depot/perl@3302

diff --git a/lib/base.pm b/lib/base.pm
index 3500cbf..9a733ea 100644 (file)
--- a/lib/base.pm
+++ b/lib/base.pm
@@ -19,12 +19,21 @@ Roughly similar in effect to
 
 Will also initialize the %FIELDS hash if one of the base classes has
 it.  Multiple inheritance of %FIELDS is not supported.  The 'base'
-pragma will croak if multiple base classes has a %FIELDS hash.  See
+pragma will croak if multiple base classes have a %FIELDS hash.  See
 L<fields> for a description of this feature.
 
 When strict 'vars' is in scope I<base> also let you assign to @ISA
 without having to declare @ISA with the 'vars' pragma first.
 
+If any of the base classes are not loaded yet, I<base> silently
+C<require>s them.  Whether to C<require> a base class package is
+determined by the absence of a global $VERSION in the base package.
+If $VERSION is not detected even after loading it, <base> will
+define $VERSION in the base package, setting it to the string
+C<-1, defined by base.pm>.
+
+=head1 HISTORY
+
 This module was introduced with Perl 5.004_04.
 
 =head1 SEE ALSO
@@ -34,13 +43,15 @@ L<fields>
 =cut
 
 package base;
+use vars qw($VERSION);
+$VERSION = "1.00";
 
 sub import {
     my $class = shift;
     my $fields_base;
 
     foreach my $base (@_) {
-       unless (defined %{"$base\::"}) {
+       unless (exists ${"$base\::"}{VERSION}) {
            eval "require $base";
            # Only ignore "Can't locate" errors from our eval require.
            # Other fatal errors (syntax etc) must be reported.
@@ -51,6 +62,8 @@ sub import {
                            "\t(Perhaps you need to 'use' the module ",
                            "which defines that package first.)");
            }
+           ${"$base\::VERSION"} = "-1, set by base.pm"
+               unless exists ${"$base\::"}{VERSION};
        }
 
        # A simple test like (defined %{"$base\::FIELDS"}) will

diff --git a/lib/locale.pm b/lib/locale.pm
index 48213ab..44e88f4 100644 (file)
--- a/lib/locale.pm
+++ b/lib/locale.pm
@@ -20,6 +20,9 @@ locales for built-in operations (LC_CTYPE for regular expressions, and
 LC_COLLATE for string comparison).  Each "use locale" or "no locale"
 affects statements to the end of the enclosing BLOCK.
 
+See L<perllocale> for more detailed information on how Perl supports
+locales.
+
 =cut
 
 sub import {