X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperldelta.pod;h=4ec71c8eb55ae8e51be7af4b985d529df28c4289;hb=f4dad39ef1a76c1f6bbf6733d7c2ee209381be78;hp=5132b49ae225d27ef096be7c7dd08bc64cb27d2a;hpb=96e4d5b14cf2dfb0235faa8bc3f701c15b15bb05;p=p5sagit%2Fp5-mst-13.2.git diff --git a/pod/perldelta.pod b/pod/perldelta.pod index 5132b49..4ec71c8 100644 --- a/pod/perldelta.pod +++ b/pod/perldelta.pod @@ -1,1341 +1,27 @@ =head1 NAME -perldelta - what's new for perl5.004 +perldelta - what's new for perl5.005 =head1 DESCRIPTION -This document describes differences between the 5.003 release (as -documented in I, second edition--the Camel Book) and -this one. +This document describes differences between the 5.004 release and this one. -=head1 Supported Environments - -Perl5.004 builds out of the box on Unix, Plan9, LynxOS, VMS, OS/2, -QNX, and AmigaOS. +=head1 Incompatible Changes =head1 Core Changes -Most importantly, many bugs were fixed. See the F -file in the distribution for details. - -=head2 Compilation option: Binary compatibility with 5.003 - -There is a new Configure question that asks if you want to maintain -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. By default, binary compatibility -is preserved at the expense of symbol table pollution. - -=head2 $PERL5OPT environment variable - -You may now put Perl options in the $PERL5OPT environment variable. -Unless Perl is running with taint checks, it will interpret this -variable as if its contents had appeared on a "#!perl" line at the -beginning of your script, except that hyphens are optional. PERL5OPT -may only be used to set the following switches: B<-[DIMUdmw]>. - -=head2 Limitations on B<-M>, and C<-m>, and B<-T> options - -The C<-M> and C<-m> options are no longer allowed on the C<#!> line of -a script. If a script needs a module, it should invoke it with the -C pragma. - -The B<-T> option is also forbidden on the C<#!> line of a script, -unless it was present on the Perl command line. Due to the way C<#!> -works, this usually means that B<-T> must be in the first argument. -Thus: - - #!/usr/bin/perl -T -w - -will probably work for an executable script invoked as C, -while: - - #!/usr/bin/perl -w -T - -will probably fail under the same conditions. (Non-Unix systems will -probably not follow this rule.) But C is guaranteed -to fail, since then there is no chance of B<-T> being found on the -command line before it is found on the C<#!> line. - -=head2 More precise warnings - -If you removed the B<-w> option from your Perl 5.003 scripts because it -made Perl too verbose, we recommend that you try putting it back when -you upgrade to Perl 5.004. Each new perl version tends to remove some -undesirable warnings, while adding new warnings that may catch bugs in -your scripts. - -=head2 Deprecated: Inherited C for non-methods - -Before Perl 5.004, C functions were looked up as methods -(using the C<@ISA> hierarchy), even when the function to be autoloaded -was called as a plain function (e.g. C), not a method -(e.g. Cbar()> or C<$obj->bar()>). - -Perl 5.005 will use method lookup only for methods' Cs. -However, there is a significant base of existing code that may be using -the old behavior. So, as an interim step, Perl 5.004 issues an optional -warning when a non-method uses an inherited C. - -The simple rule is: Inheritance will not work when autoloading -non-methods. The simple fix for old code is: In any module that used to -depend on inheriting C for non-methods from a base class named -C, execute C<*AUTOLOAD = \&BaseClass::AUTOLOAD> during startup. - -=head2 Subroutine arguments created only when they're modified - -In Perl 5.004, nonexistent array and hash elements used as subroutine -parameters are brought into existence only if they are actually -assigned to (via C<@_>). - -Earlier versions of Perl vary in their handling of such arguments. -Perl versions 5.002 and 5.003 always brought them into existence. -Perl versions 5.000, 5.001, and 5.002 brought them into existence only -if they were not the first argument (which was almost certainly a -bug). Earlier versions of Perl never brought them into existence. - -For example, given this code: - - undef @a; undef %a; - sub show { print $_[0] }; - sub change { $_[0]++ }; - show($a[2]); - change($a{b}); - -After this code executes in Perl 5.004, $a{b} exists but $a[2] does -not. In Perl 5.002 and 5.003, both $a{b} and $a[2] would have existed -(but $a[2]'s value would have been undefined). - -=head2 Group vector changeable with C<$)> - -The C<$)> special variable has always (well, in Perl 5, at least) -reflected not only the current effective group, but also the group list -as returned by the C C function (if there is one). -However, until this release, there has not been a way to call the -C C function from Perl. - -In Perl 5.004, assigning to C<$)> is exactly symmetrical with examining -it: The first number in its string value is used as the effective gid; -if there are any numbers after the first one, they are passed to the -C C function (if there is one). - -=head2 Fixed parsing of $$, &$, etc. - -Perl versions before 5.004 misinterpreted any type marker followed by -"$" and a digit. For example, "$$0" was incorrectly taken to mean -"${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004. - -However, the developers of Perl 5.004 could not fix this bug completely, -because at least two widely-used modules depend on the old meaning of -"$$0" in a string. So Perl 5.004 still interprets "$$" in the -old (broken) way inside strings; but it generates this message as a -warning. And in Perl 5.005, this special treatment will cease. - -=head2 No resetting of $. on implicit close - -The documentation for Perl 5.0 has always stated that C<$.> is I -reset when an already-open file handle is reopened with no intervening -call to C. Due to a bug, perl versions 5.000 through 5.003 -I reset C<$.> under that circumstance; Perl 5.004 does not. - -=head2 C may return undef - -The C operator returns true if a subroutine is expected to -return a list, and false otherwise. In Perl 5.004, C can -also return the undefined value if a subroutine's return value will -not be used at all, which allows subroutines to avoid a time-consuming -calculation of a return value if it isn't going to be used. - -=head2 Changes to tainting checks - -A bug in previous versions may have failed to detect some insecure -conditions when taint checks are turned on. (Taint checks are used -in setuid or setgid scripts, or when explicitly turned on with the -C<-T> invocation option.) Although it's unlikely, this may cause a -previously-working script to now fail -- which should be construed -as a blessing, since that indicates a potentially-serious security -hole was just plugged. - -=head2 New Opcode module and revised Safe module - -A new Opcode module supports the creation, manipulation and -application of opcode masks. The revised Safe module has a new API -and is implemented using the new Opcode module. Please read the new -Opcode and Safe documentation. - -=head2 Embedding improvements - -In older versions of Perl it was not possible to create more than one -Perl interpreter instance inside a single process without leaking like a -sieve and/or crashing. The bugs that caused this behavior have all been -fixed. However, you still must take care when embedding Perl in a C -program. See the updated perlembed manpage for tips on how to manage -your interpreters. - -=head2 Internal change: FileHandle class based on IO::* classes - -File handles are now stored internally as type IO::Handle. The -FileHandle module is still supported for backwards compatibility, but -it is now merely a front end to the IO::* modules -- specifically, -IO::Handle, IO::Seekable, and IO::File. We suggest, but do not -require, that you use the IO::* modules in new code. - -In harmony with this change, C<*GLOB{FILEHANDLE}> is now a -backward-compatible synonym for C<*STDOUT{IO}>. - -=head2 Internal change: PerlIO abstraction interface - -It is now possible to build Perl with AT&T's sfio IO package -instead of stdio. See L for more details, and -the F file for how to use it. - -=head2 New and changed builtin variables - -=over - -=item $^E - -Extended error message on some platforms. (Also known as -$EXTENDED_OS_ERROR if you C). - -=item $^H - -The current set of syntax checks enabled by C. See the -documentation of C for more details. Not actually new, but -newly documented. -Because it is intended for internal use by Perl core components, -there is no C long name for this variable. - -=item $^M - -By default, running out of memory it is not trappable. However, if -compiled for this, Perl may use the contents of C<$^M> as an emergency -pool after die()ing with this message. Suppose that your Perl were -compiled with -DEMERGENCY_SBRK and used Perl's malloc. Then - - $^M = 'a' x (1<<16); - -would allocate a 64K buffer for use when in emergency. -See the F file for information on how to enable this option. -As a disincentive to casual use of this advanced feature, -there is no C long name for this variable. - -=back - -=head2 New and changed builtin functions - -=over - -=item delete on slices - -This now works. (e.g. C) - -=item flock - -is now supported on more platforms, prefers fcntl to lockf when -emulating, and always flushes before (un)locking. - -=item printf and sprintf - -now support "%i" as a synonym for "%d", and the "h" modifier. -So "%hi" means "short integer in decimal", and "%ho" means -"unsigned short integer as octal". - -=item keys as an lvalue - -As an lvalue, C allows you to increase the number of hash buckets -allocated for the given hash. This can gain you a measure of efficiency if -you know the hash is going to get big. (This is similar to pre-extending -an array by assigning a larger number to $#array.) If you say - - keys %hash = 200; - -then C<%hash> will have at least 200 buckets allocated for it. These -buckets will be retained even if you do C<%hash = ()>; use C if you want to free the storage while C<%hash> is still in scope. -You can't shrink the number of buckets allocated for the hash using -C in this way (but you needn't worry about doing this by accident, -as trying has no effect). - -=item my() in Control Structures - -You can now use my() (with or without the parentheses) in the control -expressions of control structures such as: - - while (defined(my $line = <>)) { - $line = lc $line; - } continue { - print $line; - } - - if ((my $answer = ) =~ /^y(es)?$/i) { - user_agrees(); - } elsif ($answer =~ /^n(o)?$/i) { - user_disagrees(); - } else { - chomp $answer; - die "`$answer' is neither `yes' nor `no'"; - } - -Also, you can declare a foreach loop control variable as lexical by -preceding it with the word "my". For example, in: - - foreach my $i (1, 2, 3) { - some_function(); - } - -$i is a lexical variable, and the scope of $i extends to the end of -the loop, but not beyond it. - -Note that you still cannot use my() on global punctuation variables -such as $_ and the like. - -=item pack() and unpack() - -A new format 'w' represents a BER compressed integer (as defined in -ASN.1). Its format is a sequence of one or more bytes, each of which -provides seven bits of the total value, with the most significant -first. Bit eight of each byte is set, except for the last byte, in -which bit eight is clear. - -=item sysseek() and systell() - -These are new. The sysseek() operator is a variant of seek() that works -on the system file pointer. It is the only reliable way to seek before -using sysread() or syswrite(). Its companion operator systell() reports -the current position of the system file pointer. - -=item use VERSION - -If the first argument to C 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. Because C occurs at compile time, this check happens -immediately during the compilation process, unlike C, -which waits until runtime for the check. This is often useful if you -need to check the current Perl version before Cing 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 - -If the VERSION argument is present between Module and LIST, then the -C will call the VERSION method in class Module with the given -version as an argument. The default VERSION method, inherited from -the UNIVERSAL class, croaks if the given version is larger than the -value of the variable $Module::VERSION. (Note that there is not a -comma after VERSION!) - -This version-checking mechanism is similar to the one currently used -in the Exporter module, but it is faster and can be used with modules -that don't use the Exporter. It is the recommended method for new -code. - -=item prototype(FUNCTION) - -Returns the prototype of a function as a string (or C if the -function has no prototype). FUNCTION is a reference to or the name of the -function whose prototype you want to retrieve. -(Not actually new; just never documented before.) - -=item srand - -The default seed for C, which used to be C