PATCH: GH #17367 read 1 beyond end of buffer

[perl5.git] / lib / UNIVERSAL.pm

diff --git a/lib/UNIVERSAL.pm b/lib/UNIVERSAL.pm
index 6c75665..12800fb 100644 (file)
--- a/lib/UNIVERSAL.pm
+++ b/lib/UNIVERSAL.pm
@@ -1,21 +1,18 @@
 package UNIVERSAL;
 
-our $VERSION = '1.04';
+our $VERSION = '1.13';
 
 # UNIVERSAL should not contain any extra subs/methods beyond those
-# that it exists to define. The use of Exporter below is a historical
-# accident that can't be fixed without breaking code.  Note that we
-# *don't* set @ISA here, as we don't want all classes/objects inheriting from
-# Exporter.  It's bad enough that all classes have a import() method
-# whenever UNIVERSAL.pm is loaded.
-require Exporter;
-@EXPORT_OK = qw(isa can VERSION);
+# that it exists to define. The existence of import() below is a historical
+# accident that can't be fixed without breaking code.
 
 # Make sure that even though the import method is called, it doesn't do
 # anything unless called on UNIVERSAL.
 sub import {
     return unless $_[0] eq __PACKAGE__;
-    goto &Exporter::import;
+    return unless @_ > 1;
+    require Carp;
+    Carp::croak("UNIVERSAL does not export anything");
 }
 
 1;
@@ -68,7 +65,7 @@ is a package name
 
 =item C<$obj>
 
-is a blessed reference or a string containing a package name
+is a blessed reference or a package name
 
 =item C<CLASS>
 
@@ -93,11 +90,11 @@ If you're not sure what you have (the C<VAL> case), wrap the method call in an
 C<eval> block to catch the exception if C<VAL> is undefined.
 
 If you want to be sure that you're calling C<isa> as a method, not a class,
-check the invocant with C<blessed> from L<Scalar::Util> first:
+check the invocand with C<blessed> from L<Scalar::Util> first:
 
   use Scalar::Util 'blessed';
 
-  if ( blessed( $obj ) && $obj->isa("Some::Class") {
+  if ( blessed( $obj ) && $obj->isa("Some::Class") ) {
       ...
   }
 
@@ -113,7 +110,7 @@ itself.  For example, logging or serialization may be roles.
 C<DOES> and C<isa> are similar, in that if either is true, you know that the
 object or class on which you call the method can perform specific behavior.
 However, C<DOES> is different from C<isa> in that it does not care I<how> the
-invocant performs the operations, merely that it does.  (C<isa> of course
+invocand performs the operations, merely that it does.  (C<isa> of course
 mandates an inheritance relationship.  Other relationships include aggregation,
 delegation, and mocking.)
 
@@ -141,7 +138,7 @@ I<undef>.  This includes methods inherited or imported by C<$obj>, C<CLASS>, or
 C<VAL>.
 
 C<can> cannot know whether an object will be able to provide a method through
-AUTOLOAD (unless the object's class has overriden C<can> appropriately), so a
+AUTOLOAD (unless the object's class has overridden C<can> appropriately), so a
 return value of I<undef> does not necessarily mean the object will not be able
 to handle the method call. To get around this some module authors use a forward
 declaration (see L<perlsub>) for methods they will handle via AUTOLOAD. For
@@ -151,7 +148,7 @@ calling the coderef will cause an error.
 
 You may call C<can> as a class (static) method or an object method.
 
-Again, the same rule about having a valid invocant applies -- use an C<eval>
+Again, the same rule about having a valid invocand applies -- use an C<eval>
 block or C<blessed> if you need to be extra paranoid.
 
 =item C<VERSION ( [ REQUIRE ] )>
@@ -159,29 +156,40 @@ block or C<blessed> if you need to be extra paranoid.
 C<VERSION> will return the value of the variable C<$VERSION> in the
 package the object is blessed into. If C<REQUIRE> is given then
 it will do a comparison and die if the package version is not
-greater than or equal to C<REQUIRE>.
+greater than or equal to C<REQUIRE>, or if either C<$VERSION> or C<REQUIRE>
+is not a "lax" version number (as defined by the L<version> module).
+
+The return from C<VERSION> will actually be the stringified version object
+using the package C<$VERSION> scalar, which is guaranteed to be equivalent
+but may not be precisely the contents of the C<$VERSION> scalar.  If you want
+the actual contents of C<$VERSION>, use C<$CLASS::VERSION> instead.
 
 C<VERSION> can be called as either a class (static) method or an object
 method.
 
 =back
 
-=head1 EXPORTS
+=head1 WARNINGS
 
-None by default.
+B<NOTE:> C<can> directly uses Perl's internal code for method lookup, and
+C<isa> uses a very similar method and cache-ing strategy. This may cause
+strange effects if the Perl code dynamically changes @ISA in any package.
 
-You may request the import of three functions (C<isa>, C<can>, and C<VERSION>),
-however it is usually harmful to do so.  Please don't do this in new code.
+You may add other methods to the UNIVERSAL class via Perl or XS code.
+You do not need to C<use UNIVERSAL> to make these methods
+available to your program (and you should not do so).
 
-For example, previous versions of this documentation suggested using C<isa> as
-a function to determine the type of a reference:
+=head1 EXPORTS
+
+None.
 
-  use UNIVERSAL 'isa';
+Previous versions of this documentation suggested using C<isa> as
+a function to determine the type of a reference:
 
-  $yes = isa $h, "HASH";
-  $yes = isa "Foo", "Bar";
+  $yes = UNIVERSAL::isa($h, "HASH");
+  $yes = UNIVERSAL::isa("Foo", "Bar");
 
-The problem is that this code will I<never> call an overridden C<isa> method in
+The problem is that this code would I<never> call an overridden C<isa> method in
 any class.  Instead, use C<reftype> from L<Scalar::Util> for the first case:
 
   use Scalar::Util 'reftype';