=head1 NAME
-perlnews - what's new for perl5.004
+perldelta - what's new for perl5.004
=head1 DESCRIPTION
binary compatibility with Perl 5.003. If you choose binary
compatibility, you do not have to recompile your extensions, but you
might have symbol conflicts if you embed Perl in another application,
-just as in the 5.003 release.
+just as in the 5.003 release. By default, binary compatibility
+is preserved at the expense of symbol table pollution.
=head2 New Opcode Module and Revised Safe Module
Filehandles are now stored internally as type IO::Handle.
Although C<use FileHandle> and C<*STDOUT{FILEHANDLE}>
-are still supported for backwards compatibility
+are still supported for backwards compatibility,
C<use IO::Handle> (or C<IO::Seekable> or C<IO::File>) and
C<*STDOUT{IO}> are the way of the future.
=item $^E
-Extended error message under some platforms ($EXTENDED_OS_ERROR
-if you C<use English>).
+Extended error message on some platforms. (Also known as
+$EXTENDED_OS_ERROR if you C<use English>).
=item $^H
$^M = 'a' x (1<<16);
-would allocate 64K buffer for use when in emergency.
+would allocate a 64K buffer for use when in emergency.
See the F<INSTALL> file for information on how to enable this option.
As a disincentive to casual use of this advanced feature,
there is no C<use English> long name for this variable.
+=item $^S
+
+The status returned by the last pipe close, back-tick (C<``>) command, or
+system() operator, in the native system format. On UNIX and UNIX-like
+systems, C<$^S> is a synonym for C<$?>. Elsewhere, C<$^S> can be used to
+determine aspects of child status that are system-specific. Check C<$^O>
+before using this variable. (Mnemonic: System-Specific Subprocess Status.
+Also known as $SYSTEM_CHILD_STATUS if you C<use English>.)
+
=back
=head2 New and Changed Built-in Functions
print $line;
}
- if ((my $answer = <STDIN>) =~ /^yes$/i) {
+ if ((my $answer = <STDIN>) =~ /^y(es)?$/i) {
user_agrees();
- } elsif ($answer =~ /^no$/i) {
+ } elsif ($answer =~ /^n(o)?$/i) {
user_disagrees();
} else {
chomp $answer;
- die "'$answer' is neither 'yes' nor 'no'";
+ die "`$answer' is neither `yes' nor `no'";
}
Also, you can declare a foreach loop control variable as lexical by
If the first argument to C<use> is a number, it is treated as a version
number instead of a module name. If the version of the Perl interpreter
is less than VERSION, then an error message is printed and Perl exits
-immediately. This is often useful if you need to check the current
-Perl version before C<use>ing library modules which have changed in
-incompatible ways from older versions of Perl. (We try not to do
-this more than we have to.)
+immediately. Because C<use> occurs at compile time, this check happens
+immediately during the compilation process, unlike C<require VERSION>,
+which waits until run-time for the check. This is often useful if you
+need to check the current Perl version before C<use>ing library modules
+which have changed in incompatible ways from older versions of Perl.
+(We try not to do this more than we have to.)
=item use Module VERSION LIST
Functions documented in the Camel to default to $_ now in
fact do, and all those that do are so documented in L<perlfunc>.
-=head2 C<m//g> does not trigger a pos() reset on failure
+=item C<m//g> does not trigger a pos() reset on failure
The C<m//g> match iteration construct used to reset the iteration
when it failed to match (so that the next C<m//g> match would start at
matches together in conjunction with ordinary matches using the C<\G>
zero-width assertion. See L<perlop> and L<perlre>.
+=item nested C<sub{}> closures work now
+
+Prior to the 5.004 release, nested anonymous functions
+didn't work right. They do now.
+
+=item formats work right on changing lexicals
+
+Just like anonymous functions that contain lexical variables
+that change (like a lexical index variable for a C<foreach> loop),
+formats now work properly. For example, this silently failed
+before, and is fine now:
+
+ my $i;
+ foreach $i ( 1 .. 10 ) {
+ format =
+ my i is @#
+ $i
+ .
+ write;
+ }
+
=back
=head2 New Built-in Methods
The C<UNIVERSAL> package automatically contains the following methods that
are inherited by all other classes:
-=over 4
+=over
=item isa(CLASS)
$ref = bless [], 'A';
$ref->is_instance(); # True
+This can be useful for methods that wish to easily distinguish
+whether they were invoked as class or as instance methods.
+
+ sub some_meth {
+ my $classname = shift;
+ if ($classname->is_instance()) {
+ die "unexpectedly called as instance not class method";
+ }
+ .....
+ }
+
=back
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
+C<isa> uses a very similar method and caching strategy. This may cause
strange effects if the Perl code dynamically changes @ISA in any package.
You may add other methods to the UNIVERSAL class via Perl or XS code.
=head2 TIEHANDLE Now Supported
+See L<perltie> for other kinds of tie()s.
+
=over
=item TIEHANDLE classname, LIST
return an object of some sort. The reference can be used to
hold some internal information.
- sub TIEHANDLE { print "<shout>\n"; my $i; bless \$i, shift }
+ sub TIEHANDLE {
+ print "<shout>\n";
+ my $i;
+ return bless \$i, shift;
+ }
=item PRINT this, LIST
Beyond its self reference it also expects the list that was passed to
the print function.
- sub PRINT { $r = shift; $$r++; print join($,,map(uc($_),@_)),$\ }
+ sub PRINT {
+ $r = shift;
+ $$r++;
+ return print join( $, => map {uc} @_), $\;
+ }
=item READLINE this
This method will be called when the handle is read from. The method
should return undef when there is no more data.
- sub READLINE { $r = shift; "PRINT called $$r times\n"; }
+ sub READLINE {
+ $r = shift;
+ return "PRINT called $$r times\n";
+ }
=item DESTROY this
tied handle is about to be destroyed. This is useful for debugging and
possibly for cleaning up.
- sub DESTROY { print "</shout>\n" }
+ sub DESTROY {
+ print "</shout>\n";
+ }
=back
+=item Efficiency Enhancements
+
+All hash keys with the same string are only allocated once, so
+even if you have 100 copies of the same hash, the immutable keys
+never have to be re-allocated.
+
+Functions that have an empty prototype and that do nothing but return
+a fixed value are now inlined (e.g. C<sub PI () { 3.14159 }>).
+
=head1 Pragmata
Three new pragmatic modules exist:
=item use blib
+=item use blib 'dir'
+
Looks for MakeMaker-like I<'blib'> directory structure starting in
I<dir> (or current directory) and working back up to five levels of
parent directories.
=head1 Modules
+=head2 Installation Directories
+
+The I<installperl> script now places the Perl source files for
+extensions in the architecture-specific library directory, which is
+where the shared libraries for extensions have always been. This
+change is intended to allow administrators to keep the Perl 5.004
+library directory unchanged from a previous version, without running
+the risk of binary incompatibility between extensions' Perl source and
+shared libraries.
+
+=head2 Fcntl
+
+New constants in the existing Fcntl modules are now supported,
+provided that your operating system happens to support them:
+
+ F_GETOWN F_SETOWN
+ O_ASYNC O_DEFER O_DSYNC O_FSYNC O_SYNC
+ O_EXLOCK O_SHLOCK
+
+These constants are intended for use with the Perl operators sysopen()
+and fcntl() and the basic database modules like SDBM_File. For the
+exact meaning of these and other Fcntl constants please refer to your
+operating system's documentation for fcntl() and open().
+
+In addition, the Fcntl module now provides these constants for use
+with the Perl operator flock():
+
+ LOCK_SH LOCK_EX LOCK_NB LOCK_UN
+
+These constants are defined in all environments (because where there is
+no flock() system call, Perl emulates it). However, for historical
+reasons, these constants are not exported unless they are explicitly
+requested with the ":flock" tag (e.g. C<use Fcntl ':flock'>).
+
=head2 Module Information Summary
-Brand new modules:
+Brand new modules, arranged by topic rather than strictly
+alphabetically:
+
+ CPAN interface to Comprehensive Perl Archive Network
+ CPAN::FirstTime create a CPAN configuration file
+ CPAN::Nox run CPAN while avoiding compiled extensions
IO.pm Top-level interface to IO::* classes
IO/File.pm IO::File extension Perl module
User/grent.pm Object-oriented wrapper around CORE::getgr*
User/pwent.pm Object-oriented wrapper around CORE::getpw*
- lib/Tie/RefHash.pm Base class for tied hashes with references as keys
+ Tie/RefHash.pm Base class for tied hashes with references as keys
UNIVERSAL.pm Base class for *ALL* classes
sinh cosh tanh cotanh asinh acosh atanh acotanh
cplx cplxe
+=head2 DB_File
+
+There have been quite a few changes made to DB_File. Here are a few of
+the highlights:
+
+=over
+
+=item *
+
+Fixed a handful of bugs.
+
+=item *
+
+By public demand, added support for the standard hash function exists().
+
+=item *
+
+Made it compatible with Berkeley DB 1.86.
+
+=item *
+
+Made negative subscripts work with RECNO interface.
+
+=item *
+
+Changed the default flags from O_RDWR to O_CREAT|O_RDWR and the default
+mode from 0640 to 0666.
+
+=item *
+
+Made DB_File automatically import the open() constants (O_RDWR,
+O_CREAT etc.) from Fcntl, if available.
+
+=item *
+
+Updated documentation.
+
+=back
+
+Refer to the HISTORY section in DB_File.pm for a complete list of
+changes. Everything after DB_File 1.01 has been added since 5.003.
+
+=head2 Net::Ping
+
+Major rewrite - support added for both udp echo and real icmp pings.
+
=head2 Overridden Built-ins
Many of the Perl built-ins returning lists now have
use User::pwent;
$his = (stat($filename)->st_uid == pwent($whoever)->pw_uid);
-=head1 Efficiency Enhancements
+=head1 Utility Changes
-All hash keys with the same string are only allocated once, so
-even if you have 100 copies of the same hash, the immutable keys
-never have to be re-allocated.
+=head2 xsubpp
-Functions that have an empty prototype and that do nothing but return
-a fixed value are now inlined (e.g. C<sub PI () { 3.14159 }>).
+=over
+
+=item C<void> XSUBs now default to returning nothing
+
+Due to a documentation/implementation bug in previous versions of
+Perl, XSUBs with a return type of C<void> have actually been
+returning one value. Usually that value was the GV for the XSUB,
+but sometimes it was some already freed or reused value, which would
+sometimes lead to program failure.
+
+In Perl 5.004, if an XSUB is declared as returning C<void>, it
+actually returns no value, i.e. an empty list (though there is a
+backward-compatibility exception; see below). If your XSUB really
+does return an SV, you should give it a return type of C<SV *>.
+
+For backward compatibility, I<xsubpp> tries to guess whether a
+C<void> XSUB is really C<void> or if it wants to return an C<SV *>.
+It does so by examining the text of the XSUB: if I<xsubpp> finds
+what looks like an assignment to C<ST(0)>, it assumes that the
+XSUB's return type is really C<SV *>.
+
+=back
+
+=head1 C Language API Changes
+
+=over
+
+=item C<gv_fetchmethod> and C<perl_call_sv>
+
+The C<gv_fetchmethod> function finds a method for an object, just like
+in Perl 5.003. The GV it returns may be a method cache entry.
+However, in Perl 5.004, method cache entries are not visible to users;
+therefore, they can no longer be passed directly to C<perl_call_sv>.
+Instead, you should use the C<GvCV> macro on the GV to extract its CV,
+and pass the CV to C<perl_call_sv>.
+
+The most likely symptom of passing the result of C<gv_fetchmethod> to
+C<perl_call_sv> is Perl's producing an "Undefined subroutine called"
+error on the I<second> call to a given method (since there is no cache
+on the first call).
+
+=back
=head1 Documentation Changes
Many of the base and library pods were updated. These
new pods are included in section 1:
-=over 4
+=over
-=item L<perlnews>
+=item L<perldelta>
This document.
Several new conditions will trigger warnings that were
silent before. Some only affect certain platforms.
-The following new warnings and errors
-outline these:
+The following new warnings and errors outline these.
+These messages are classified as follows (listed in
+increasing order of desperation):
+
+ (W) A warning (optional).
+ (D) A deprecation (optional).
+ (S) A severe warning (mandatory).
+ (F) A fatal error (trappable).
+ (P) An internal error you should never see (trappable).
+ (X) A very fatal error (non-trappable).
+ (A) An alien error message (not generated by Perl).
-=over 4
+=over
=item "my" variable %s masks earlier declaration in same scope
until the end of the scope or until all closure referents to it are
destroyed.
+=item %s argument is not a HASH element or slice
+
+(F) The argument to delete() must be either a hash element, such as
+
+ $foo{$bar}
+ $ref->[12]->{"susie"}
+
+or a hash slice, such as
+
+ @foo{$bar, $baz, $xyzzy}
+ @{$ref->[12]}{"susie", "queue"}
+
=item Allocation too large: %lx
(X) You can't allocate more than 64K on an MSDOS machine.
might directly modify logical name tables and introduce non-standard names,
or it may indicate that a logical name table has been corrupted.
+=item Can't use bareword ("%s") as %s ref while "strict refs" in use
+
+(F) Only hard references are allowed by "strict refs". Symbolic references
+are disallowed. See L<perlref>.
+
+=item Constant subroutine %s redefined
+
+(S) You redefined a subroutine which had previously been eligible for
+inlining. See L<perlsub/"Constant Functions"> for commentary and
+workarounds.
+
+=item Died
+
+(F) You passed die() an empty string (the equivalent of C<die "">) or
+you called it with no args and both C<$@> and C<$_> were empty.
+
=item Integer overflow in hex number
(S) The literal hex number you have specified is too big for your
architecture. On a 32-bit architecture the largest octal literal is
037777777777.
+=item Name "%s::%s" used only once: possible typo
+
+(W) Typographical errors often show up as unique variable names.
+If you had a good reason for having a unique name, then just mention
+it again somehow to suppress the message (the C<use vars> pragma is
+provided for just this purpose).
+
=item Null picture in formline
(F) The first argument to formline must be a valid format picture
The sole exception to this is that C<sysread()>ing past the buffer
will extend the buffer and zero pad the new area.
+=item Stub found while resolving method `%s' overloading `%s' in package `%s'
+
+(P) Overloading resolution over @ISA tree may be broken by importing stubs.
+Stubs should never be implicitely created, but explicit calls to C<can>
+may break this.
+
+=item Cannot resolve method `%s' overloading `%s' in package `s'
+
+(P) Internal error trying to resolve overloading specified by a method
+name (as opposed to a subroutine reference).
+
=item Out of memory!
(X|F) The malloc() function returned 0, indicating there was insufficient
=item Possible attempt to put comments in qw() list
-(W) You probably wrote something like this:
+(W) qw() lists contain items separated by whitespace; as with literal
+strings, comment characters are not ignored, but are instead treated
+as literal data. (You may have used different delimiters than the
+exclamation marks parentheses shown here; braces are also frequently
+used.)
- qw( a # a comment
+You probably wrote something like this:
+
+ @list = qw(
+ a # a comment
b # another comment
- ) ;
+ );
when you should have written this:
- qw( a
+ @list = qw(
+ a
b
- ) ;
+ );
+
+If you really want comments, build your list the
+old-fashioned way, with quotes and commas:
+
+ @list = (
+ 'a', # a comment
+ 'b', # another comment
+ );
=item Possible attempt to separate words with commas
-(W) You probably wrote something like this:
+(W) qw() lists contain items separated by whitespace; therefore commas
+aren't needed to separate the items. (You may have used different
+delimiters than the parentheses shown here; braces are also frequently
+used.)
- qw( a, b, c );
+You probably wrote something like this:
-when you should have written this:
+ qw! a, b, c !;
+
+which puts literal commas into some of the list items. Write it without
+commas if you don't want them to appear in your data:
+
+ qw! a b c !;
+
+=item Scalar value @%s{%s} better written as $%s{%s}
- qw( a b c );
+(W) You've used a hash slice (indicated by @) to select a single element of
+a hash. Generally it's better to ask for a scalar value (indicated by $).
+The difference is that C<$foo{&bar}> always behaves like a scalar, both when
+assigning to it and when evaluating its argument, while C<@foo{&bar}> behaves
+like a list when you assign to it, and provides a list context to its
+subscript, which can do weird things if you're expecting only one subscript.
=item untie attempted while %d inner references still exist
(W) A copy of the object returned from C<tie> (or C<tied>) was still
valid when C<untie> was called.
-=item Got an error from DosAllocMem:
+=item Value of %s construct can be "0"; test with defined()
+
+(W) In a conditional expression, you used <HANDLE>, <*> (glob), or
+C<readdir> as a boolean value. Each of these constructs can return a
+value of "0"; that would make the conditional expression false, which
+is probably not what you intended. When using these constructs in
+conditional expressions, test their values with the C<defined> operator.
+
+=item Variable "%s" may be unavailable
+
+(W) An inner (nested) I<anonymous> subroutine is inside a I<named>
+subroutine, and outside that is another subroutine; and the anonymous
+(innermost) subroutine is referencing a lexical variable defined in
+the outermost subroutine. For example:
+
+ sub outermost { my $a; sub middle { sub { $a } } }
+
+If the anonymous subroutine is called or referenced (directly or
+indirectly) from the outermost subroutine, it will share the variable
+as you would expect. But if the anonymous subroutine is called or
+referenced when the outermost subroutine is not active, it will see
+the value of the shared variable as it was before and during the
+*first* call to the outermost subroutine, which is probably not what
+you want.
+
+In these circumstances, it is usually best to make the middle
+subroutine anonymous, using the C<sub {}> syntax. Perl has specific
+support for shared variables in nested anonymous subroutines; a named
+subroutine in between interferes with this feature.
+
+=item Variable "%s" will not stay shared
+
+(W) An inner (nested) I<named> subroutine is referencing a lexical
+variable defined in an outer subroutine.
+
+When the inner subroutine is called, it will probably see the value of
+the outer subroutine's variable as it was before and during the
+*first* call to the outer subroutine; in this case, after the first
+call to the outer subroutine is complete, the inner and outer
+subroutines will no longer share a common value for the variable. In
+other words, the variable will no longer be shared.
+
+Furthermore, if the outer subroutine is anonymous and references a
+lexical variable outside itself, then the outer and inner subroutines
+will I<never> share the given variable.
+
+This problem can usually be solved by making the inner subroutine
+anonymous, using the C<sub {}> syntax. When inner anonymous subs that
+reference variables in outer subroutines are called or referenced,
+they are automatically re-bound to the current values of such
+variables.
+
+=item Warning: something's wrong
+
+(W) You passed warn() an empty string (the equivalent of C<warn "">) or
+you called it with no args and C<$_> was empty.
+
+=item Got an error from DosAllocMem
-(P) An error peculiar to OS/2. Most probably you use an obsolete version
-of Perl, and should not happen anyway.
+(P) An error peculiar to OS/2. Most probably you're using an obsolete
+version of Perl, and this should not happen anyway.
=item Malformed PERLLIB_PREFIX
=head1 BUGS
-If you find what you think is a bug, you might check the headers
-of recently posted articles
-in the comp.lang.perl.misc newsgroup. There may also be
-information at http://www.perl.com/perl/, the Perl Home Page.
+If you find what you think is a bug, you might check the headers of
+recently posted articles in the comp.lang.perl.misc newsgroup.
+There may also be information at http://www.perl.com/perl/, the Perl
+Home Page.
If you believe you have an unreported bug, please run the B<perlbug>
program included with your release. Make sure you trim your bug
projects / p5sagit/p5-mst-13.2.git / blobdiff