Re: [PATCH Exporter.pm] Explain dangers & workaround for AUTOLOADed constant subs

Message-Id: <200111290630.IAA08631@tiku.hut.fi>

(plus paragraph rewrapping)

p4raw-id: //depot/perl@13356

diff --git a/lib/Exporter.pm b/lib/Exporter.pm
index 7067464..ce89c59 100644 (file)
--- a/lib/Exporter.pm
+++ b/lib/Exporter.pm
@@ -309,16 +309,17 @@ may make this a fatal error.
 
 =head2 C<AUTOLOAD>ed Constants
 
-Many modules make use of C<AUTOLOAD>ing for constant subroutines to avoid
-having to compile and waste memory on rarely used values (see L<perlsub> for
-details on constant subroutines).  Calls to such constant subroutines are not
-optimized away at compile time because they can't be checked at compile time
-for constancy.
-
-Even if a prototype is available at compile time, the body of the subroutine is
-not (it hasn't been C<AUTOLOAD>ed yet). perl needs to examine both the C<()>
-prototype and the body of a subroutine at compile time to detect that it can
-safely replace calls to that subroutine with the constant value.
+Many modules make use of C<AUTOLOAD>ing for constant subroutines to
+avoid having to compile and waste memory on rarely used values (see
+L<perlsub> for details on constant subroutines).  Calls to such
+constant subroutines are not optimized away at compile time because
+they can't be checked at compile time for constancy.
+
+Even if a prototype is available at compile time, the body of the
+subroutine is not (it hasn't been C<AUTOLOAD>ed yet). perl needs to
+examine both the C<()> prototype and the body of a subroutine at
+compile time to detect that it can safely replace calls to that
+subroutine with the constant value.
 
 A workaround for this is to call the constants once in a C<BEGIN> block:
 
@@ -330,11 +331,11 @@ A workaround for this is to call the constants once in a C<BEGIN> block:
    BEGIN { SO_LINGER }
    foo( SO_LINGER );     ## SO_LINGER optimized away at compile time.
 
-This forces the C<AUTOLOAD> for C<SOLINGER> to take place before SO_LINGER is
-encountered later in C<My> package.
+This forces the C<AUTOLOAD> for C<SO_LINGER> to take place before
+SO_LINGER is encountered later in C<My> package.
 
-If you are writing a package that C<AUTOLOAD>s, consider forcing an C<AUTOLOAD>
-for any constants explicitly imported by other packages or which are usually
-used when your package is C<use>d.
+If you are writing a package that C<AUTOLOAD>s, consider forcing
+an C<AUTOLOAD> for any constants explicitly imported by other packages
+or which are usually used when your package is C<use>d.
 
 =cut