=head1 NAME
-perldelta - what's new for perl5.004
+perldelta - what's new for perl v5.6 (as of v5.005_58)
=head1 DESCRIPTION
-This document describes differences between the 5.003 release (as
-documented in I<Programming Perl>, second edition--the Camel Book) and
-this one.
+This is an unsupported alpha release, meant for intrepid Perl developers
+only. The included sources may not even build correctly on some platforms.
+Subscribing to perl5-porters is the best way to monitor and contribute
+to the progress of development releases (see www.perl.org for info).
-=head1 Supported Environments
+This document describes differences between the 5.005 release and this one.
-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<Changes>
-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 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 Internal Change: FileHandle Deprecated
-
-Filehandles are now stored internally as type IO::Handle.
-Although C<use FileHandle> and C<*STDOUT{FILEHANDLE}>
-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.
-
-=head2 Internal Change: PerlIO internal IO abstraction interface
-
-It is now possible to build Perl with AT&T's sfio IO package
-instead of stdio. See L<perlapio> for more details, and
-the F<INSTALL> file for how to use it.
-
-=head2 New and Changed Built-in Variables
-
-=over
-
-=item $^E
-
-Extended error message on some platforms. (Also known as
-$EXTENDED_OS_ERROR if you C<use English>).
-
-=item $^H
-
-The current set of syntax checks enabled by C<use strict>. See the
-documentation of C<strict> for more details. Not actually new, but
-newly documented.
-Because it is intended for internal use by Perl core components,
-there is no C<use English> 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
-
- $^M = 'a' x (1<<16);
-
-would allocate a 64K buffer for use when in emergency.
-See the F<INSTALL> file for information on how to enable this option.
-As a disincentive to casual use of this advanced feature,
-there is no C<use English> long name for this variable.
-
-=back
-
-=head2 New and Changed Built-in Functions
-
-=over
-
-=item delete on slices
-
-This now works. (e.g. C<delete @ENV{'PATH', 'MANPATH'}>)
+=head2 Perl Source Incompatibilities
-=item flock
+TODO
-is now supported on more platforms, and prefers fcntl
-to lockf when emulating.
+=head2 C Source Incompatibilities
-=item printf and sprintf
+=over 4
-now support "%i" as a synonym for "%d", and the "h" modifier.
-So "%hi" means "short integer in decimal", and "%ho" means
-"unsigned short integer as octal".
+=item C<PERL_POLLUTE>
-=item keys as an lvalue
+Release 5.005 grandfathered old global symbol names by providing preprocessor
+macros for extension source compatibility. As of release 5.6, these
+preprocessor definitions are not available by default. You need to explicitly
+compile perl with C<-DPERL_POLLUTE> to get these definitions. For
+extensions still using the old symbols, this option can be
+specified via MakeMaker:
-As an lvalue, C<keys> allows you to increase the number of hash buckets
-allocated for the given associative array. This can gain you a measure
-of efficiency if you know the hash is going to get big. (This is
-similar to pre-extending an array by assigning a larger number to
-$#array.) If you say
+ perl Makefile.PL POLLUTE=1
- keys %hash = 200;
+=item C<PERL_IMPLICIT_CONTEXT>
-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<undef
-%hash> 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<keys> in this way (but you needn't worry about doing this by accident,
-as trying has no effect).
+This new build option provides a set of macros for all API functions
+such that an implicit interpreter/thread context argument is passed to
+every API function. As a result of this, something like C<sv_setsv(foo,bar)>
+amounts to a macro invocation that actually translates to something like
+C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
+to not have any significant source compatibility issues, the difference
+between a macro and a real function call will need to be considered.
-=item my() in Control Structures
+This means that there B<is> a source compatibility issue as a result of
+this if your extensions attempt to use pointers to any of the Perl API
+functions.
-You can now use my() (with or without the parentheses) in the control
-expressions of control structures such as:
+Note that the above issue is not relevant to the default build of
+Perl, whose interfaces continue to match those of prior versions
+(but subject to the other options described here).
- while (my $line = <>) {
- $line = lc $line;
- } continue {
- print $line;
- }
+For testing purposes, the 5.005_58 release automatically enables
+PERL_IMPLICIT_CONTEXT whenever Perl is built with -Dusethreads or
+-Dusemultiplicity.
- if ((my $answer = <STDIN>) =~ /^y(es)?$/i) {
- user_agrees();
- } elsif ($answer =~ /^n(o)?$/i) {
- user_disagrees();
- } else {
- chomp $answer;
- die "`$answer' is neither `yes' nor `no'";
- }
+See L<perlguts/"The Perl API"> for detailed information on the
+ramifications of building Perl using this option.
-Also, you can declare a foreach loop control variable as lexical by
-preceding it with the word "my". For example, in:
+=item C<PERL_POLLUTE_MALLOC>
- foreach my $i (1, 2, 3) {
- some_function();
- }
+Enabling Perl's malloc in release 5.005 and earlier caused
+the namespace of system versions of the malloc family of functions to
+be usurped by the Perl versions, since by default they used the
+same names.
-$i is a lexical variable, and the scope of $i extends to the end of
-the loop, but not beyond it.
+Besides causing problems on platforms that do not allow these functions to
+be cleanly replaced, this also meant that the system versions could not
+be called in programs that used Perl's malloc. Previous versions of Perl
+have allowed this behaviour to be suppressed with the HIDEMYMALLOC and
+EMBEDMYMALLOC preprocessor definitions.
-Note that you still cannot use my() on global punctuation variables
-such as $_ and the like.
+As of release 5.6, Perl's malloc family of functions have default names
+distinct from the system versions. You need to explicitly compile perl with
+C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
+and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
+the default.
-=item unpack() and pack()
+Note that these functions do B<not> constitute Perl's memory allocation API.
+See L<perlguts/"Memory Allocation"> for further information about that.
-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 C<PL_na> and C<dTHR> Issues
-=item use VERSION
-
-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. 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
-
-If the VERSION argument is present between Module and LIST, then the
-C<use> 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<undef> 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 $_ as Default
-
-Functions documented in the Camel to default to $_ now in
-fact do, and all those that do are so documented in L<perlfunc>.
-
-=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
-the beginning of the string). You now have to explicitly do a
-C<pos $str = 0;> to reset the "last match" position, or modify the
-string in some way. This change makes it practical to chain C<m//g>
-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 @#
- $i
- .
- write;
- }
+The C<PL_na> global is now thread local, so a C<dTHR> declaration is needed
+in the scope in which the global appears. XSUBs should handle this automatically,
+but if you have used C<PL_na> in support functions, you either need to
+change the C<PL_na> to a local variable (which is recommended), or put in
+a C<dTHR>.
=back
-=head2 New Built-in Methods
-
-The C<UNIVERSAL> package automatically contains the following methods that
-are inherited by all other classes:
+=head2 Compatible C Source API Changes
=over
-=item isa(CLASS)
-
-C<isa> returns I<true> if its object is blessed into a sub-class of C<CLASS>
-
-C<isa> is also exportable and can be called as a sub with two arguments. This
-allows the ability to check what a reference points to. Example:
-
- use UNIVERSAL qw(isa);
-
- if(isa($ref, 'ARRAY')) {
- ...
- }
-
-=item can(METHOD)
+=item C<PATCHLEVEL> is now C<PERL_VERSION>
-C<can> checks to see if its object has a method called C<METHOD>,
-if it does then a reference to the sub is returned; if it does not then
-I<undef> is returned.
+The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
+are now available by default from perl.h, and reflect the base revision,
+patchlevel, and subversion respectively. C<PERL_REVISION> had no
+prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
+previously available as C<PATCHLEVEL> and C<SUBVERSION>.
-=item VERSION( [NEED] )
-
-C<VERSION> returns the version number of the class (package). If the
-NEED argument is given then it will check that the current version (as
-defined by the $VERSION variable in the given package) not less than
-NEED; it will die if this is not the case. This method is normally
-called as a class method. This method is called automatically by the
-C<VERSION> form of C<use>.
-
- use A 1.2 qw(some imported subs);
- # implies:
- A->VERSION(1.2);
+The new names cause less pollution of the B<cpp> namespace and reflect what
+the numbers have come to stand for in common practice. For compatibility,
+the old names are still supported when F<patchlevel.h> is explicitly
+included (as required before), so there is no source incompatibility
+from the change.
=back
-B<NOTE:> C<can> directly uses Perl's internal code for method lookup, and
-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.
-You do not need to C<use UNIVERSAL> in order to make these methods
-available to your program. This is necessary only if you wish to
-have C<isa> available as a plain subroutine in the current package.
-
-=head2 TIEHANDLE Now Supported
-
-See L<perltie> for other kinds of tie()s.
-
-=over
-
-=item TIEHANDLE classname, LIST
-
-This is the constructor for the class. That means it is expected to
-return an object of some sort. The reference can be used to
-hold some internal information.
-
- sub TIEHANDLE {
- print "<shout>\n";
- my $i;
- return bless \$i, shift;
- }
-
-=item PRINT this, LIST
-
-This method will be triggered every time the tied handle is printed to.
-Beyond its self reference it also expects the list that was passed to
-the print function.
-
- sub PRINT {
- $r = shift;
- $$r++;
- return print join( $, => map {uc} @_), $\;
- }
-
-=item READLINE this
+=head2 Binary Incompatibilities
-This method will be called when the handle is read from. The method
-should return undef when there is no more data.
+The default build of this release can be made binary compatible with the
+5.005 release or its maintenance versions. Add -DPERL_BINCOMPAT_5005
+to ccflags in config.sh to achieve this. See INSTALL for further
+information about adding build flags to config.sh.
- sub READLINE {
- $r = shift;
- return "PRINT called $$r times\n";
- }
+The usethreads or usemultiplicity builds are B<not> binary compatible
+with the corresponding builds in 5.005.
-=item DESTROY this
-
-As with the other types of ties, this method will be called when the
-tied handle is about to be destroyed. This is useful for debugging and
-possibly for cleaning up.
-
- sub DESTROY {
- print "</shout>\n";
- }
-
-=back
-
-=item Efficiency Enhancements
+=head1 Core 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 Unicode and UTF-8 support
-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 }>).
+Perl can optionally use UTF-8 as its internal representation for character
+strings. The C<use utf8> pragma enables this support in the current lexical
+scope. See L<utf8> for more information.
-=head1 Pragmata
+=head2 Lexically scoped warning categories
-Four new pragmatic modules exist:
+You can now control the granularity of warnings emitted by perl at a finer
+level using the C<use warning> pragma. See L<warning> and L<perllexwarn>
+for details.
-=over
+=head2 Binary numbers supported
-=item use blib
+Binary numbers are now supported as literals, in s?printf formats, and
+C<oct()>:
-=item use blib 'dir'
+ $answer = 0b101010;
+ printf "The answer is: %b\n", oct("0b101010");
-Looks for MakeMaker-like I<'blib'> directory structure starting in
-I<dir> (or current directory) and working back up to five levels of
-parent directories.
+=head2 syswrite() ease-of-use
-Intended for use on command line with B<-M> option as a way of testing
-arbitrary scripts against an uninstalled version of a package.
+The length argument of C<syswrite()> is now optional.
-=item use locale
+=head2 64-bit support
-Tells the compiler to enable (or disable) the use of POSIX locales for
-built-in operations.
+Better 64-bit support -- but full support still a distant goal. One
+must Configure with -Duse64bits to get Configure to probe for the
+extent of 64-bit support. Depending on the platform (hints file) more
+or less 64-awareness becomes available. As of 5.005_54 at least
+somewhat 64-bit aware platforms are HP-UX 11 or better, Solaris 2.6 or
+better, IRIX 6.2 or better. Naturally 64-bit platforms like Digital
+Unix and UNICOS also have 64-bit support.
-When C<use locale> is in effect, the current LC_CTYPE locale is used
-for regular expressions and case mapping; LC_COLLATE for string
-ordering; and LC_NUMERIC for numeric formating in printf and sprintf
-(but B<not> in print). LC_NUMERIC is always used in write, since
-lexical scoping of formats is problematic at best.
+=head2 Better syntax checks on parenthesized unary operators
-Each C<use locale> or C<no locale> affects statements to the end of
-the enclosing BLOCK or, if not inside a BLOCK, to the end of the
-current file. Locales can be switched and queried with
-POSIX::setlocale().
+Expressions such as:
-See L<perllocale> for more information.
+ print defined(&foo,&bar,&baz);
+ print uc("foo","bar","baz");
+ undef($foo,&bar);
-=item use ops
+used to be accidentally allowed in earlier versions, and produced
+unpredictable behaviour. Some produced ancillary warnings
+when used in this way; others silently did the wrong thing.
-Disable unsafe opcodes, or any named opcodes, when compiling Perl code.
+The parenthesized forms of most unary operators that expect a single
+argument now ensure that they are not called with more than one
+argument, making the cases shown above syntax errors. The usual
+behaviour of:
-=item use vmsish
+ print defined &foo, &bar, &baz;
+ print uc "foo", "bar", "baz";
+ undef $foo, &bar;
-Enable VMS-specific language features. Currently, there are three
-VMS-specific feature available: 'status', which makes C<$?> and
-C<system> return genuine VMS status values instead of emulating POSIX;
-'exit', which makes C<exit> take a genuine VMS status value instead of
-assuming that C<exit 1> is an error; and 'time', which makes all times
-relative to the local time zone, in the VMS tradition.
+remains unchanged. See L<perlop>.
-=back
+=head2 POSIX character class syntax [: :] supported
-=head1 Modules
+For example to match alphabetic characters use /[[:alpha:]]/.
+See L<perlre> for details.
-=head2 Installation Directories
+=head2 Improved C<qw//> operator
-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.
+The C<qw//> operator is now evaluated at compile time into a true list
+instead of being replaced with a run time call to C<split()>. This
+removes the confusing misbehaviour of C<qw//> in scalar context, which
+had inherited that behaviour from split().
-=head2 Fcntl
+Thus:
-New constants in the existing Fcntl modules are now supported,
-provided that your operating system happens to support them:
+ $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
- F_GETOWN F_SETOWN
- O_ASYNC O_DEFER O_DSYNC O_FSYNC O_SYNC
- O_EXLOCK O_SHLOCK
+now correctly prints "3|a", instead of "2|a".
-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().
+=head2 pack() format 'Z' supported
-In addition, the Fcntl module now provides these constants for use
-with the Perl operator flock():
+The new format type 'Z' is useful for packing and unpacking null-terminated
+strings. See L<perlfunc/"pack">.
- LOCK_SH LOCK_EX LOCK_NB LOCK_UN
+=head2 pack() format modifier '!' supported
-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'>).
+The new format type modifier '!' is useful for packing and unpacking
+native shorts, ints, and longs. See L<perlfunc/"pack">.
-=head2 Module Information Summary
+=head2 pack() and unpack() support counted strings
-Brand new modules, arranged by topic rather than strictly
-alphabetically:
+The template character '#' can be used to specify a counted string
+type to be packed or unpacked. See L<perlfunc/"pack">.
- CPAN interface to Comprehensive Perl Archive Network
- CPAN::FirstTime create a CPAN configuration file
- CPAN::Nox run CPAN while avoiding compiled extensions
+=head2 $^X variables may now have names longer than one character
- IO.pm Top-level interface to IO::* classes
- IO/File.pm IO::File extension Perl module
- IO/Handle.pm IO::Handle extension Perl module
- IO/Pipe.pm IO::Pipe extension Perl module
- IO/Seekable.pm IO::Seekable extension Perl module
- IO/Select.pm IO::Select extension Perl module
- IO/Socket.pm IO::Socket extension Perl module
+Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
+error. Now variable names that begin with a control character may be
+arbitrarily long. However, for compatibility reasons, these variables
+I<must> be written with explicit braces, as C<${^XY}> for example.
+C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
+than one control character, such as C<${^XY^Z}>, are illegal.
- Opcode.pm Disable named opcodes when compiling Perl code
+The old syntax has not changed. As before, `^X' may be either a
+literal control-X character or the two-character sequence `caret' plus
+`X'. When braces are omitted, the variable name stops after the
+control character. Thus C<"$^XYZ"> continues to be synonymous with
+C<$^X . "YZ"> as before.
- ExtUtils/Embed.pm Utilities for embedding Perl in C programs
- ExtUtils/testlib.pm Fixes up @INC to use just-built extension
+As before, lexical variables may not have names beginning with control
+characters. As before, variables whose names begin with a control
+character are always forced to be in package `main'. All such variables
+are reserved for future extensions, except those that begin with
+C<^_>, which may be used by user programs and is guaranteed not to
+acquire special meaning in any future version of Perl.
- FindBin.pm Find path of currently executing program
+=head1 Significant bug fixes
- Class/Template.pm Structure/member template builder
- File/stat.pm Object-oriented wrapper around CORE::stat
- Net/hostent.pm Object-oriented wrapper around CORE::gethost*
- Net/netent.pm Object-oriented wrapper around CORE::getnet*
- Net/protoent.pm Object-oriented wrapper around CORE::getproto*
- Net/servent.pm Object-oriented wrapper around CORE::getserv*
- Time/gmtime.pm Object-oriented wrapper around CORE::gmtime
- Time/localtime.pm Object-oriented wrapper around CORE::localtime
- Time/tm.pm Perl implementation of "struct tm" for {gm,local}time
- User/grent.pm Object-oriented wrapper around CORE::getgr*
- User/pwent.pm Object-oriented wrapper around CORE::getpw*
+=head2 E<lt>HANDLEE<gt> on empty files
- Tie/RefHash.pm Base class for tied hashes with references as keys
+With C<$/> set to C<undef>, slurping an empty file returns a string of
+zero length (instead of C<undef>, as it used to) the first time the
+HANDLE is read. Further reads yield C<undef>.
- UNIVERSAL.pm Base class for *ALL* classes
+This means that the following will append "foo" to an empty file (it used
+to do nothing):
-=head2 IO
+ perl -0777 -pi -e 's/^/foo/' empty_file
-The IO module provides a simple mechanism to load all of the IO modules at one
-go. Currently this includes:
+The behaviour of:
- IO::Handle
- IO::Seekable
- IO::File
- IO::Pipe
- IO::Socket
+ perl -pi -e 's/^/foo/' empty_file
-For more information on any of these modules, please see its
-respective documentation.
+is unchanged (it continues to leave the file empty).
-=head2 Math::Complex
+=head2 C<eval '...'> improvements
-The Math::Complex module has been totally rewritten, and now supports
-more operations. These are overloaded:
+Line numbers (as reflected by caller() and most diagnostics) within
+C<eval '...'> were often incorrect when here documents were involved.
+This has been corrected.
- + - * / ** <=> neg ~ abs sqrt exp log sin cos atan2 "" (stringify)
+Lexical lookups for variables appearing in C<eval '...'> within
+functions that were themselves called within an C<eval '...'> were
+searching the wrong place for lexicals. The lexical search now
+correctly ends at the subroutine's block boundary.
-And these functions are now exported:
+Parsing of here documents used to be flawed when they appeared as
+the replacement expression in C<eval 's/.../.../e'>. This has
+been fixed.
- pi i Re Im arg
- log10 logn cbrt root
- tan cotan asin acos atan acotan
- sinh cosh tanh cotanh asinh acosh atanh acotanh
- cplx cplxe
+=head2 Automatic flushing of output buffers
-=head2 DB_File
+fork(), exec(), system(), qx//, and pipe open()s now flush buffers
+of all files opened for output when the operation
+was attempted. This mostly eliminates confusing
+buffering mishaps suffered by users unaware of how Perl internally
+handles I/O.
-There have been quite a few changes made to DB_File. Here are a few of
-the highlights:
+=head2 Better diagnostics on meaningless filehandle operations
-=over
+Constructs such as C<open(E<lt>FHE<gt>)> and C<close(E<lt>FHE<gt>)>
+are compile time errors. Attempting to read from filehandles that
+were opened only for writing will now produce warnings (just as
+writing to read-only filehandles does).
-=item *
+=head1 Supported Platforms
-Fixed a handful of bugs.
+=over 4
=item *
-By public demand, added support for the standard hash function exists().
+VM/ESA is now supported.
=item *
-Made it compatible with Berkeley DB 1.86.
+Siemens BS2000 is now supported under the POSIX Shell.
=item *
-Made negative subscripts work with RECNO interface.
+The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
+extension.
=item *
-Changed the default flags from O_RDWR to O_CREAT|O_RDWR and the default
-mode from 0640 to 0666.
+GNU/Hurd is now supported.
=item *
-Made DB_File automatically import the open() constants (O_RDWR,
-O_CREAT etc.) from Fcntl, if available.
+Rhapsody is now supported.
=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
-object-oriented overrides. These are:
-
- File::stat
- Net::hostent
- Net::netent
- Net::protoent
- Net::servent
- Time::gmtime
- Time::localtime
- User::grent
- User::pwent
-
-For example, you can now say
-
- use File::stat;
- use User::pwent;
- $his = (stat($filename)->st_uid == pwent($whoever)->pw_uid);
-
-=head1 Utility Changes
-
-=head2 xsubpp
-
-=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 *>.
+EPOC is is now supported (on Psion 5).
=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 New tests
-=head1 Documentation Changes
+=over 4
-Many of the base and library pods were updated. These
-new pods are included in section 1:
+=item op/io_const
-=over
+IO constants (SEEK_*, _IO*).
-=item L<perldelta>
+=item op/io_dir
-This document.
+Directory-related IO methods (new, read, close, rewind, tied delete).
-=item L<perllocale>
+=item op/io_multihomed
-Locale support (internationalization and localization).
+INET sockets with multi-homed hosts.
-=item L<perltoot>
+=item op/io_poll
-Tutorial on Perl OO programming.
+IO poll().
-=item L<perlapio>
+=item op/io_unix
-Perl internal IO abstraction interface.
+UNIX sockets.
-=item L<perldebug>
+=item op/filetest
-Although not new, this has been massively updated.
+File test operators.
-=item L<perlsec>
+=item op/lex_assign
-Although not new, this has been massively updated.
+Verify operations that access pad objects (lexicals and temporaries).
=back
-=head1 New Diagnostics
-
-Several new conditions will trigger warnings that were
-silent before. Some only affect certain platforms.
-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
-
-=item "my" variable %s masks earlier declaration in same scope
-
-(S) A lexical variable has been redeclared in the same scope, effectively
-eliminating all access to the previous instance. This is almost always
-a typographical error. Note that the earlier variable will still exist
-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}
- $ref->[12]->{"susie"}
-
-or a hash slice, such as
+=head1 Modules and Pragmata
- @foo{$bar, $baz, $xyzzy}
- @{$ref->[12]}{"susie", "queue"}
+=head2 Modules
-=item Allocation too large: %lx
+=over 4
-(X) You can't allocate more than 64K on an MSDOS machine.
+=item ByteLoader
-=item Allocation too large
+The ByteLoader is a dedication extension to generate and run
+Perl bytecode. See L<ByteLoader>.
-(F) You can't allocate more than 2^31+"small amount" bytes.
+=item B
-=item Attempt to free non-existent shared string
+The Perl Compiler suite has been extensively reworked for this
+release.
-(P) Perl maintains a reference counted internal table of strings to
-optimize the storage and access of hash keys and other strings. This
-indicates someone tried to decrement the reference count of a string
-that can no longer be found in the table.
+=item Devel::DProf
-=item Attempt to use reference as lvalue in substr
+Devel::DProf, a Perl source code profiler has been added.
-(W) You supplied a reference as the first argument to substr() used
-as an lvalue, which is pretty strange. Perhaps you forgot to
-dereference it first. See L<perlfunc/substr>.
+=item Dumpvalue
-=item Unsupported function fork
+Added Dumpvalue module provides screen dumps of Perl data.
-(F) Your version of executable does not support forking.
+=item Benchmark
-Note that under some systems, like OS/2, there may be different flavors of
-Perl executables, some of which may support fork, some not. Try changing
-the name you call Perl by to C<perl_>, C<perl__>, and so on.
+You can now run tests for I<n> seconds instead of guessing the right
+number of tests to run: e.g. timethese(-5, ...) will run each
+code for at least 5 CPU seconds. Zero as the "number of repetitions"
+means "for at least 3 CPU seconds". The output format has also
+changed. For example:
-=item Ill-formed logical name |%s| in prime_env_iter
+use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
-(W) A warning peculiar to VMS. A logical name was encountered when preparing
-to iterate over %ENV which violates the syntactic rules governing logical
-names. Since it cannot be translated normally, it is skipped, and will not
-appear in %ENV. This may be a benign occurrence, as some software packages
-might directly modify logical name tables and introduce non-standard names,
-or it may indicate that a logical name table has been corrupted.
+will now output something like this:
-=item Can't use bareword ("%s") as %s ref while "strict refs" in use
+Benchmark: running a, b, each for at least 5 CPU seconds...
+ a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
+ b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
-(F) Only hard references are allowed by "strict refs". Symbolic references
-are disallowed. See L<perlref>.
+New features: "each for at least N CPU seconds...", "wallclock secs",
+and the "@ operations/CPU second (n=operations)".
-=item Constant subroutine %s redefined
+=item Devel::Peek
-(S) You redefined a subroutine which had previously been eligible for
-inlining. See L<perlsub/"Constant Functions"> for commentary and
-workarounds.
+The Devel::Peek module provides access to the internal representation
+of Perl variables and data. It is a data debugging tool for the XS programmer.
-=item Died
+=item Fcntl
-(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.
+More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
+large (more than 4G) file access (64-bit support is not yet
+working, though, so no need to get overly excited), Free/Net/OpenBSD
+locking behaviour flags F_FLOCK, F_POSIX, Linux F_SHLCK, and
+O_ACCMODE: the mask of O_RDONLY, O_WRONLY, and O_RDWR.
-=item Integer overflow in hex number
+=item File::Spec
-(S) The literal hex number you have specified is too big for your
-architecture. On a 32-bit architecture the largest hex literal is
-0xFFFFFFFF.
+New methods have been added to the File::Spec module: devnull() returns
+the name of the null device (/dev/null on Unix) and tmpdir() the name of
+the temp directory (normally /tmp on Unix). There are now also methods
+to convert between absolute and relative filenames: abs2rel() and
+rel2abs(). For compatibility with operating systems that specify volume
+names in file paths, the splitpath(), splitdir(), and catdir() methods
+have been added.
-=item Integer overflow in octal number
+=item File::Spec::Functions
-(S) The literal octal number you have specified is too big for your
-architecture. On a 32-bit architecture the largest octal literal is
-037777777777.
+The new File::Spec::Functions modules provides a function interface
+to the File::Spec module. Allows shorthand
-=item Name "%s::%s" used only once: possible typo
+ $fullname = catfile($dir1, $dir2, $file);
-(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).
+instead of
-=item Null picture in formline
+ $fullname = File::Spec->catfile($dir1, $dir2, $file);
-(F) The first argument to formline must be a valid format picture
-specification. It was found to be empty, which probably means you
-supplied it an uninitialized value. See L<perlform>.
+=item Math::BigInt
-=item Offset outside string
+The logical operations C<E<lt>E<lt>>, C<E<gt>E<gt>>, C<&>, C<|>,
+and C<~> are now supported on bigints.
-(F) You tried to do a read/write/send/recv operation with an offset
-pointing outside the buffer. This is difficult to imagine.
-The sole exception to this is that C<sysread()>ing past the buffer
-will extend the buffer and zero pad the new area.
+=item Math::Complex
-=item Stub found while resolving method `%s' overloading `%s' in package `%s'
+The accessor methods Re, Im, arg, abs, rho, and theta can now also
+act as mutators (accessor $z->Re(), mutator $z->Re(3)).
-(P) Overloading resolution over @ISA tree may be broken by importing stubs.
-Stubs should never be implicitely created, but explicit calls to C<can>
-may break this.
+=item Math::Trig
-=item Cannot resolve method `%s' overloading `%s' in package `s'
+A little bit of radial trigonometry (cylindrical and spherical),
+radial coordinate conversions, and the great circle distance were added.
-(P) Internal error trying to resolve overloading specified by a method
-name (as opposed to a subroutine reference).
+=item SDBM_File
-=item Out of memory!
+An EXISTS method has been added to this module (and sdbm_exists() has
+been added to the underlying sdbm library), so one can now call exists
+on an SDBM_File tied hash and get the correct result, rather than a
+runtime error.
-(X|F) The malloc() function returned 0, indicating there was insufficient
-remaining memory (or virtual memory) to satisfy the request.
+=item Time::Local
-The request was judged to be small, so the possibility to trap it
-depends on the way Perl was compiled. By default it is not trappable.
-However, if compiled for this, Perl may use the contents of C<$^M> as
-an emergency pool after die()ing with this message. In this case the
-error is trappable I<once>.
+The timelocal() and timegm() functions used to silently return bogus
+results when the date exceeded the machine's integer range. They
+now consistently croak() if the date falls in an unsupported range.
-=item Out of memory during request for %s
+=item Win32
-(F) The malloc() function returned 0, indicating there was insufficient
-remaining memory (or virtual memory) to satisfy the request. However,
-the request was judged large enough (compile-time default is 64K), so
-a possibility to shut down by trapping this error is granted.
+The error return value in list context has been changed for all functions
+that return a list of values. Previously these functions returned a list
+with a single element C<undef> if an error occurred. Now these functions
+return the empty list in these situations. This applies to the following
+functions:
-=item Possible attempt to put comments in qw() list
+ Win32::FsType
+ Win32::GetOSVersion
-(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.)
+The remaining functions are unchanged and continue to return C<undef> on
+error even in list context.
-You probably wrote something like this:
+The Win32::SetLastError(ERROR) function has been added as a complement
+to the Win32::GetLastError() function.
- @list = qw(
- a # a comment
- b # another comment
- );
+The new Win32::GetFullPathName(FILENAME) returns the full absolute
+pathname for FILENAME in scalar context. In list context it returns
+a two-element list containing the fully qualified directory name and
+the filename.
-when you should have written this:
+=item DBM Filters
- @list = qw(
- a
- b
- );
+A new feature called "DBM Filters" has been added to all the
+DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
+DBM Filters add four new methods to each DBM module:
-If you really want comments, build your list the
-old-fashioned way, with quotes and commas:
+ filter_store_key
+ filter_store_value
+ filter_fetch_key
+ filter_fetch_value
- @list = (
- 'a', # a comment
- 'b', # another comment
- );
+These can be used to filter key-value pairs before the pairs are
+written to the database or just after they are read from the database.
+See L<perldbmfilter> for further information.
-=item Possible attempt to separate words with commas
+=back
-(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.)
+=head2 Pragmata
-You probably wrote something like this:
+C<use utf8> to enable UTF-8 and Unicode support.
- qw! a, b, c !;
+C<use caller 'encoding'> allows modules to inherit pragmatic attributes
+from the caller's context. C<encoding> is currently the only supported
+attribute.
-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:
+Lexical warnings pragma, C<use warning;>, to control optional warnings.
- qw! a b c !;
+C<use filetest> to control the behaviour of filetests (C<-r> C<-w> ...).
+Currently only one subpragma implemented, "use filetest 'access';",
+that enables the use of access(2) or equivalent to check
+permissions instead of using stat(2) as usual. This matters
+in filesystems where there are ACLs (access control lists): the
+stat(2) might lie, but access(2) knows better.
-=item Scalar value @%s{%s} better written as $%s{%s}
+=head1 Utility Changes
-(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.
+Todo.
-=item untie attempted while %d inner references still exist
+=head1 Documentation Changes
-(W) A copy of the object returned from C<tie> (or C<tied>) was still
-valid when C<untie> was called.
+=over 4
-=item Value of %s construct can be "0"; test with defined()
+=item perlopentut.pod
-(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.
+A tutorial on using open() effectively.
-=item Variable "%s" may be unavailable
+=item perlreftut.pod
-(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:
+A tutorial that introduces the essentials of references.
- sub outermost { my $a; sub middle { sub { $a } } }
+=item perltootc.pod
-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.
+A tutorial on managing class data for object modules.
-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.
+=back
-=item Variable "%s" will not stay shared
+=head1 New Diagnostics
-(W) An inner (nested) I<named> subroutine is referencing a lexical
-variable defined in an outer subroutine.
+=item /%s/: Unrecognized escape \\%c passed through
-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.
+(W) You used a backslash-character combination which is not recognized
+by Perl. This combination appears in an interpolated variable or a
+C<'>-delimited regular expression.
-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.
+=item Filehandle %s opened only for output
-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.
+(W) You tried to read from a filehandle opened only for writing. If you
+intended it to be a read-write filehandle, you needed to open it with
+"+E<lt>" or "+E<gt>" or "+E<gt>E<gt>" instead of with "E<lt>" or nothing. If
+you intended only to read from the file, use "E<lt>". See
+L<perlfunc/open>.
-=item Warning: something's wrong
+=item Missing command in piped open
-(W) You passed warn() an empty string (the equivalent of C<warn "">) or
-you called it with no args and C<$_> was empty.
+(W) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
+construction, but the command was missing or blank.
-=item Got an error from DosAllocMem
+=item Unrecognized escape \\%c passed through
-(P) An error peculiar to OS/2. Most probably you're using an obsolete
-version of Perl, and this should not happen anyway.
+(W) You used a backslash-character combination which is not recognized
+by Perl.
-=item Malformed PERLLIB_PREFIX
+=item defined(@array) is deprecated
-(F) An error peculiar to OS/2. PERLLIB_PREFIX should be of the form
+(D) defined() is not usually useful on arrays because it checks for an
+undefined I<scalar> value. If you want to see if the array is empty,
+just use C<if (@array) { # not empty }> for example.
- prefix1;prefix2
+=item defined(%hash) is deprecated
-or
+(D) defined() is not usually useful on hashes because it checks for an
+undefined I<scalar> value. If you want to see if the hash is empty,
+just use C<if (%hash) { # not empty }> for example.
- prefix1 prefix2
+=head1 Obsolete Diagnostics
-with non-empty prefix1 and prefix2. If C<prefix1> is indeed a prefix of
-a builtin library search path, prefix2 is substituted. The error may appear
-if components are not found, or are too long. See L<perlos2/"PERLLIB_PREFIX">.
+Todo.
-=item PERL_SH_DIR too long
+=head1 Configuration Changes
-(F) An error peculiar to OS/2. PERL_SH_DIR is the directory to find the
-C<sh>-shell in. See L<perlos2/"PERL_SH_DIR">.
+=head2 installusrbinperl
-=item Process terminated by SIG%s
+You can use "Configure -Uinstallusrbinperl" which causes installperl
+to skip installing perl also as /usr/bin/perl. This is useful if you
+prefer not to modify /usr/bin for some reason or another but harmful
+because many scripts assume to find Perl in /usr/bin/perl.
-(W) This is a standard message issued by OS/2 applications, while *nix
-applications die in silence. It is considered a feature of the OS/2
-port. One can easily disable this by appropriate sighandlers, see
-L<perlipc/"Signals">. See L<perlos2/"Process terminated by SIGTERM/SIGINT">.
+=head2 SOCKS support
-=back
+You can use "Configure -Dusesocks" which causes Perl to probe
+for the SOCKS proxy protocol library, http://www.socks.nec.com/
=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.
+articles recently posted to 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
-down to a tiny but sufficient test case. Your bug report, along
-with the output of C<perl -V>, will be sent off to perlbug@perl.com
-to be analysed by the Perl porting team.
+program included with your release. Make sure to trim your bug down
+to a tiny but sufficient test case. Your bug report, along with the
+output of C<perl -V>, will be sent off to perlbug@perl.com to be
+analysed by the Perl porting team.
=head1 SEE ALSO
The F<Changes> file for exhaustive details on what changed.
-The F<INSTALL> file for how to build Perl. This file has been
-significantly updated for 5.004, so even veteran users should
-look through it.
+The F<INSTALL> file for how to build Perl.
The F<README> file for general stuff.
-The F<Copying> file for copyright information.
+The F<Artistic> and F<Copying> files for copyright information.
=head1 HISTORY
-Constructed by Tom Christiansen, grabbing material with permission
-from innumerable contributors, with kibitzing by more than a few Perl
-porters.
+Written by Gurusamy Sarathy <F<gsar@umich.edu>>, with many contributions
+from The Perl Porters.
+
+Send omissions or corrections to <F<perlbug@perl.com>>.
-Last update: Tue Jan 14 14:03:02 EST 1997
+=cut
https://perl5.git.perl.org / perl5.git / blobdiff