Change 11974 by jhi@alpha on 2001/09/10 12:39:25
Warn against using bare v-strings as IP addresses
(okay if using the wrappers from Socket)
Affected files ...
... //depot/perl/pod/perldata.pod#33 edit
... //depot/perl/pod/perlport.pod#72 edit
Differences ...
==== //depot/perl/pod/perldata.pod#33 (text) ====
Index: perl/pod/perldata.pod
--- perl/pod/perldata.pod.~1~ Mon Sep 10 06:45:05 2001
+++ perl/pod/perldata.pod Mon Sep 10 06:45:05 2001
@@ -333,13 +333,13 @@
an expression.
A literal of the form C<v1.20.300.4000> is parsed as a string composed
-of characters with the specified ordinals. This provides an alternative,
-more readable way to construct strings, rather than use the somewhat less
-readable interpolation form C<"\x{1}\x{14}\x{12c}\x{fa0}">. This is useful
-for representing Unicode strings, and for comparing version "numbers"
-using the string comparison operators, C<cmp>, C<gt>, C<lt> etc.
-If there are two or more dots in the literal, the leading C<v> may be
-omitted.
+of characters with the specified ordinals. This form, known as
+v-strings, provides an alternative, more readable way to construct
+strings, rather than use the somewhat less readable interpolation form
+C<"\x{1}\x{14}\x{12c}\x{fa0}">. This is useful for representing
+Unicode strings, and for comparing version "numbers" using the string
+comparison operators, C<cmp>, C<gt>, C<lt> etc. If there are two or
+more dots in the literal, the leading C<v> may be omitted.
print v9786; # prints UTF-8 encoded SMILEY, "\x{263a}"
print v102.111.111; # prints "foo"
@@ -348,6 +348,8 @@
Such literals are accepted by both C<require> and C<use> for
doing a version check. The C<$^V> special variable also contains the
running Perl interpreter's version in this form. See L<perlvar/$^V>.
+Note that using the v-strings for IPv4 addresses is not portable unless
+you also use the inet_aton()/inet_ntoa() routines of the Socket package.
The special literals __FILE__, __LINE__, and __PACKAGE__
represent the current filename, line number, and package name at that
==== //depot/perl/pod/perlport.pod#72 (text) ====
Index: perl/pod/perlport.pod
--- perl/pod/perlport.pod.~1~ Mon Sep 10 06:45:05 2001
+++ perl/pod/perlport.pod Mon Sep 10 06:45:05 2001
@@ -423,6 +423,14 @@
The Unix System V IPC (C<msg*(), sem*(), shm*()>) is not available
even on all Unix platforms.
+Do not use either the bare result of C<pack("N", 10, 20, 30, 40)
+or bare v-strings (such as C<v10.20.30.40>) or the to represent
+IPv4 addresses: both forms just pack the four bytes into network order.
+That this would be equal to the C language C<in_addr> struct (which is
+what the socket code internally uses) is not guaranteed. To be
+portable use the routines of the Socket extension, such as
+C<inet_aton()>, C<inet_ntoa()>, and C<sockaddr_in()>.
+
The rule of thumb for portable code is: Do it all in portable Perl, or
use a module (that may internally implement it with platform-specific
code, but expose a common interface).
End of Patch.
