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   1  =head1 NAME
   2  
   3  perl590delta - what is new for perl v5.9.0
   4  
   5  =head1 DESCRIPTION
   6  
   7  This document describes differences between the 5.8.0 release and
   8  the 5.9.0 release.
   9  
  10  =head1 Incompatible Changes
  11  
  12  =head2 Hash Randomisation
  13  
  14  Mainly due to security reasons, the "random ordering" of hashes
  15  has been made even more random.  Previously while the order of hash
  16  elements from keys(), values(), and each() was essentially random,
  17  it was still repeatable.  Now, however, the order varies between
  18  different runs of Perl.
  19  
  20  B<Perl has never guaranteed any ordering of the hash keys>, and the
  21  ordering has already changed several times during the lifetime of
  22  Perl 5.  Also, the ordering of hash keys has always been, and
  23  continues to be, affected by the insertion order.
  24  
  25  The added randomness may affect applications.
  26  
  27  One possible scenario is when output of an application has included
  28  hash data.  For example, if you have used the Data::Dumper module to
  29  dump data into different files, and then compared the files to see
  30  whether the data has changed, now you will have false positives since
  31  the order in which hashes are dumped will vary.  In general the cure
  32  is to sort the keys (or the values); in particular for Data::Dumper to
  33  use the C<Sortkeys> option.  If some particular order is really
  34  important, use tied hashes: for example the Tie::IxHash module
  35  which by default preserves the order in which the hash elements
  36  were added.
  37  
  38  More subtle problem is reliance on the order of "global destruction".
  39  That is what happens at the end of execution: Perl destroys all data
  40  structures, including user data.  If your destructors (the DESTROY
  41  subroutines) have assumed any particular ordering to the global
  42  destruction, there might be problems ahead.  For example, in a
  43  destructor of one object you cannot assume that objects of any other
  44  class are still available, unless you hold a reference to them.
  45  If the environment variable PERL_DESTRUCT_LEVEL is set to a non-zero
  46  value, or if Perl is exiting a spawned thread, it will also destruct
  47  the ordinary references and the symbol tables that are no longer in use.
  48  You can't call a class method or an ordinary function on a class that
  49  has been collected that way.
  50  
  51  The hash randomisation is certain to reveal hidden assumptions about
  52  some particular ordering of hash elements, and outright bugs: it
  53  revealed a few bugs in the Perl core and core modules.
  54  
  55  To disable the hash randomisation in runtime, set the environment
  56  variable PERL_HASH_SEED to 0 (zero) before running Perl (for more
  57  information see L<perlrun/PERL_HASH_SEED>), or to disable the feature
  58  completely in compile time, compile with C<-DNO_HASH_SEED> (see F<INSTALL>).
  59  
  60  See L<perlsec/"Algorithmic Complexity Attacks"> for the original
  61  rationale behind this change.
  62  
  63  =head2 UTF-8 On Filehandles No Longer Activated By Locale
  64  
  65  In Perl 5.8.0 all filehandles, including the standard filehandles,
  66  were implicitly set to be in Unicode UTF-8 if the locale settings
  67  indicated the use of UTF-8.  This feature caused too many problems,
  68  so the feature was turned off and redesigned: see L</"Core Enhancements">.
  69  
  70  =head2 Single-number v-strings are no longer v-strings before "=>"
  71  
  72  The version strings or v-strings (see L<perldata/"Version Strings">)
  73  feature introduced in Perl 5.6.0 has been a source of some confusion--
  74  especially when the user did not want to use it, but Perl thought it
  75  knew better.  Especially troublesome has been the feature that before
  76  a "=>" a version string (a "v" followed by digits) has been interpreted
  77  as a v-string instead of a string literal.  In other words:
  78  
  79      %h = ( v65 => 42 );
  80  
  81  has meant since Perl 5.6.0
  82  
  83      %h = ( 'A' => 42 );
  84  
  85  (at least in platforms of ASCII progeny)  Perl 5.8.1 restored the
  86  more natural interpretation
  87  
  88      %h = ( 'v65' => 42 );
  89  
  90  The multi-number v-strings like v65.66 and 65.66.67 still continue to
  91  be v-strings in Perl 5.8.
  92  
  93  =head2 (Win32) The -C Switch Has Been Repurposed
  94  
  95  The -C switch has changed in an incompatible way.  The old semantics
  96  of this switch only made sense in Win32 and only in the "use utf8"
  97  universe in 5.6.x releases, and do not make sense for the Unicode
  98  implementation in 5.8.0.  Since this switch could not have been used
  99  by anyone, it has been repurposed.  The behavior that this switch
 100  enabled in 5.6.x releases may be supported in a transparent,
 101  data-dependent fashion in a future release.
 102  
 103  For the new life of this switch, see L<"UTF-8 no longer default under
 104  UTF-8 locales">, and L<perlrun/-C>.
 105  
 106  =head2 (Win32) The /d Switch Of cmd.exe
 107  
 108  Since version 5.8.1, perl uses the /d switch when running the cmd.exe shell
 109  internally for system(), backticks, and when opening pipes to external
 110  programs.  The extra switch disables the execution of AutoRun commands
 111  from the registry, which is generally considered undesirable when
 112  running external programs.  If you wish to retain compatibility with
 113  the older behavior, set PERL5SHELL in your environment to C<cmd /x/c>.
 114  
 115  =head2 The C<$*> variable has been removed
 116  
 117  C<$*>, which was deprecated in favor of the C</s> and C</m> regexp
 118  modifiers, has been removed.
 119  
 120  =head1 Core Enhancements
 121  
 122  =head2 Assertions
 123  
 124  Perl 5.9.0 has experimental support for assertions.  Note that the user
 125  interface is not fully stabilized yet, and it may change until the 5.10.0
 126  release.  A new command-line switch, B<-A>, is used to activate
 127  assertions, which are declared with the C<assertions> pragma.  See
 128  L<assertions>.
 129  
 130  =head2 Defined-or operators
 131  
 132  A new operator C<//> (defined-or) has been implemented.
 133  The following statement:
 134  
 135      $a // $b
 136  
 137  is merely equivalent to
 138  
 139     defined $a ? $a : $b
 140  
 141  and
 142  
 143     $c //= $d;
 144  
 145  can be used instead of
 146  
 147     $c = $d unless defined $c;
 148  
 149  This operator has the same precedence and associativity as C<||>.
 150  It has a low-precedence counterpart, C<err>, which has the same precedence
 151  and associativity as C<or>.  Special care has been taken to ensure that
 152  those operators Do What You Mean while not breaking old code, but some
 153  edge cases involving the empty regular expression may now parse
 154  differently.  See L<perlop> for details.
 155  
 156  =head2 UTF-8 no longer default under UTF-8 locales
 157  
 158  In Perl 5.8.0 many Unicode features were introduced.   One of them
 159  was found to be of more nuisance than benefit: the automagic
 160  (and silent) "UTF-8-ification" of filehandles, including the
 161  standard filehandles, if the user's locale settings indicated
 162  use of UTF-8.
 163  
 164  For example, if you had C<en_US.UTF-8> as your locale, your STDIN and
 165  STDOUT were automatically "UTF-8", in other words an implicit
 166  binmode(..., ":utf8") was made.  This meant that trying to print, say,
 167  chr(0xff), ended up printing the bytes 0xc3 0xbf.  Hardly what
 168  you had in mind unless you were aware of this feature of Perl 5.8.0.
 169  The problem is that the vast majority of people weren't: for example
 170  in RedHat releases 8 and 9 the B<default> locale setting is UTF-8, so
 171  all RedHat users got UTF-8 filehandles, whether they wanted it or not.
 172  The pain was intensified by the Unicode implementation of Perl 5.8.0
 173  (still) having nasty bugs, especially related to the use of s/// and
 174  tr///.  (Bugs that have been fixed in 5.8.1)
 175  
 176  Therefore a decision was made to backtrack the feature and change it
 177  from implicit silent default to explicit conscious option.  The new
 178  Perl command line option C<-C> and its counterpart environment
 179  variable PERL_UNICODE can now be used to control how Perl and Unicode
 180  interact at interfaces like I/O and for example the command line
 181  arguments.  See L<perlrun/-C> and L<perlrun/PERL_UNICODE> for more
 182  information.
 183  
 184  =head2 Unsafe signals again available
 185  
 186  In Perl 5.8.0 the so-called "safe signals" were introduced.  This
 187  means that Perl no longer handles signals immediately but instead
 188  "between opcodes", when it is safe to do so.  The earlier immediate
 189  handling easily could corrupt the internal state of Perl, resulting
 190  in mysterious crashes.
 191  
 192  However, the new safer model has its problems too.  Because now an
 193  opcode, a basic unit of Perl execution, is never interrupted but
 194  instead let to run to completion, certain operations that can take a
 195  long time now really do take a long time.  For example, certain
 196  network operations have their own blocking and timeout mechanisms, and
 197  being able to interrupt them immediately would be nice.
 198  
 199  Therefore perl 5.8.1 introduced a "backdoor" to restore the pre-5.8.0
 200  (pre-5.7.3, really) signal behaviour.  Just set the environment variable
 201  PERL_SIGNALS to C<unsafe>, and the old immediate (and unsafe)
 202  signal handling behaviour returns.  See L<perlrun/PERL_SIGNALS>
 203  and L<perlipc/"Deferred Signals (Safe Signals)">.
 204  
 205  In completely unrelated news, you can now use safe signals with
 206  POSIX::SigAction.  See L<POSIX/POSIX::SigAction>.
 207  
 208  =head2 Tied Arrays with Negative Array Indices
 209  
 210  Formerly, the indices passed to C<FETCH>, C<STORE>, C<EXISTS>, and
 211  C<DELETE> methods in tied array class were always non-negative.  If
 212  the actual argument was negative, Perl would call FETCHSIZE implicitly
 213  and add the result to the index before passing the result to the tied
 214  array method.  This behaviour is now optional.  If the tied array class
 215  contains a package variable named C<$NEGATIVE_INDICES> which is set to
 216  a true value, negative values will be passed to C<FETCH>, C<STORE>,
 217  C<EXISTS>, and C<DELETE> unchanged.
 218  
 219  =head2 local ${$x}
 220  
 221  The syntaxes
 222  
 223      local ${$x}
 224      local @{$x}
 225      local %{$x}
 226  
 227  now do localise variables, given that the $x is a valid variable name.
 228  
 229  =head2 Unicode Character Database 4.0.0
 230  
 231  The copy of the Unicode Character Database included in Perl 5.8 has
 232  been updated to 4.0.0 from 3.2.0.  This means for example that the
 233  Unicode character properties are as in Unicode 4.0.0.
 234  
 235  =head2 Miscellaneous Enhancements
 236  
 237  C<unpack()> now defaults to unpacking the C<$_>.
 238  
 239  C<map> in void context is no longer expensive. C<map> is now context
 240  aware, and will not construct a list if called in void context.
 241  
 242  If a socket gets closed by the server while printing to it, the client
 243  now gets a SIGPIPE.  While this new feature was not planned, it fell
 244  naturally out of PerlIO changes, and is to be considered an accidental
 245  feature.
 246  
 247  PerlIO::get_layers(FH) returns the names of the PerlIO layers
 248  active on a filehandle.
 249  
 250  PerlIO::via layers can now have an optional UTF8 method to
 251  indicate whether the layer wants to "auto-:utf8" the stream.
 252  
 253  utf8::is_utf8() has been added as a quick way to test whether
 254  a scalar is encoded internally in UTF-8 (Unicode).
 255  
 256  =head1 Modules and Pragmata
 257  
 258  =head2 Updated Modules And Pragmata
 259  
 260  The following modules and pragmata have been updated since Perl 5.8.0:
 261  
 262  =over 4
 263  
 264  =item base
 265  
 266  =item B::Bytecode
 267  
 268  In much better shape than it used to be.  Still far from perfect, but
 269  maybe worth a try.
 270  
 271  =item B::Concise
 272  
 273  =item B::Deparse
 274  
 275  =item Benchmark
 276  
 277  An optional feature, C<:hireswallclock>, now allows for high
 278  resolution wall clock times (uses Time::HiRes).
 279  
 280  =item ByteLoader
 281  
 282  See B::Bytecode.
 283  
 284  =item bytes
 285  
 286  Now has bytes::substr.
 287  
 288  =item CGI
 289  
 290  =item charnames
 291  
 292  One can now have custom character name aliases.
 293  
 294  =item CPAN
 295  
 296  There is now a simple command line frontend to the CPAN.pm
 297  module called F<cpan>.
 298  
 299  =item Data::Dumper
 300  
 301  A new option, Pair, allows choosing the separator between hash keys
 302  and values.
 303  
 304  =item DB_File
 305  
 306  =item Devel::PPPort
 307  
 308  =item Digest::MD5
 309  
 310  =item Encode
 311  
 312  Significant updates on the encoding pragma functionality
 313  (tr/// and the DATA filehandle, formats).
 314  
 315  If a filehandle has been marked as to have an encoding, unmappable
 316  characters are detected already during input, not later (when the
 317  corrupted data is being used).
 318  
 319  The ISO 8859-6 conversion table has been corrected (the 0x30..0x39
 320  erroneously mapped to U+0660..U+0669, instead of U+0030..U+0039).  The
 321  GSM 03.38 conversion did not handle escape sequences correctly.  The
 322  UTF-7 encoding has been added (making Encode feature-complete with
 323  Unicode::String).
 324  
 325  =item fields
 326  
 327  =item libnet
 328  
 329  =item Math::BigInt
 330  
 331  A lot of bugs have been fixed since v1.60, the version included in Perl
 332  v5.8.0. Especially noteworthy are the bug in Calc that caused div and mod to
 333  fail for some large values, and the fixes to the handling of bad inputs.
 334  
 335  Some new features were added, e.g. the broot() method, you can now pass
 336  parameters to config() to change some settings at runtime, and it is now
 337  possible to trap the creation of NaN and infinity.
 338  
 339  As usual, some optimizations took place and made the math overall a tad
 340  faster. In some cases, quite a lot faster, actually. Especially alternative
 341  libraries like Math::BigInt::GMP benefit from this. In addition, a lot of the
 342  quite clunky routines like fsqrt() and flog() are now much much faster.
 343  
 344  =item MIME::Base64
 345  
 346  =item NEXT
 347  
 348  Diamond inheritance now works.
 349  
 350  =item Net::Ping
 351  
 352  =item PerlIO::scalar
 353  
 354  Reading from non-string scalars (like the special variables, see
 355  L<perlvar>) now works.
 356  
 357  =item podlators
 358  
 359  =item Pod::LaTeX
 360  
 361  =item PodParsers
 362  
 363  =item Pod::Perldoc
 364  
 365  Complete rewrite.  As a side-effect, no longer refuses to startup when
 366  run by root.
 367  
 368  =item Scalar::Util
 369  
 370  New utilities: refaddr, isvstring, looks_like_number, set_prototype.
 371  
 372  =item Storable
 373  
 374  Can now store code references (via B::Deparse, so not foolproof).
 375  
 376  =item strict
 377  
 378  Earlier versions of the strict pragma did not check the parameters
 379  implicitly passed to its "import" (use) and "unimport" (no) routine.
 380  This caused the false idiom such as:
 381  
 382          use strict qw(@ISA);
 383          @ISA = qw(Foo);
 384  
 385  This however (probably) raised the false expectation that the strict
 386  refs, vars and subs were being enforced (and that @ISA was somehow
 387  "declared").  But the strict refs, vars, and subs are B<not> enforced
 388  when using this false idiom.
 389  
 390  Starting from Perl 5.8.1, the above B<will> cause an error to be
 391  raised.  This may cause programs which used to execute seemingly
 392  correctly without warnings and errors to fail when run under 5.8.1.
 393  This happens because
 394  
 395          use strict qw(@ISA);
 396  
 397  will now fail with the error:
 398  
 399          Unknown 'strict' tag(s) '@ISA'
 400  
 401  The remedy to this problem is to replace this code with the correct idiom:
 402  
 403          use strict;
 404          use vars qw(@ISA);
 405          @ISA = qw(Foo);
 406  
 407  =item Term::ANSIcolor
 408  
 409  =item Test::Harness
 410  
 411  Now much more picky about extra or missing output from test scripts.
 412  
 413  =item Test::More
 414  
 415  =item Test::Simple
 416  
 417  =item Text::Balanced
 418  
 419  =item Time::HiRes
 420  
 421  Use of nanosleep(), if available, allows mixing subsecond sleeps with
 422  alarms.
 423  
 424  =item threads
 425  
 426  Several fixes, for example for join() problems and memory
 427  leaks.  In some platforms (like Linux) that use glibc the minimum memory
 428  footprint of one ithread has been reduced by several hundred kilobytes.
 429  
 430  =item threads::shared
 431  
 432  Many memory leaks have been fixed.
 433  
 434  =item Unicode::Collate
 435  
 436  =item Unicode::Normalize
 437  
 438  =item Win32::GetFolderPath
 439  
 440  =item Win32::GetOSVersion
 441  
 442  Now returns extra information.
 443  
 444  =back
 445  
 446  =head1 Utility Changes
 447  
 448  The C<h2xs> utility now produces a more modern layout:
 449  F<Foo-Bar/lib/Foo/Bar.pm> instead of F<Foo/Bar/Bar.pm>.
 450  Also, the boilerplate test is now called F<t/Foo-Bar.t>
 451  instead of F<t/1.t>.
 452  
 453  The Perl debugger (F<lib/perl5db.pl>) has now been extensively
 454  documented and bugs found while documenting have been fixed.
 455  
 456  C<perldoc> has been rewritten from scratch to be more robust and
 457  feature rich.
 458  
 459  C<perlcc -B> works now at least somewhat better, while C<perlcc -c>
 460  is rather more broken.  (The Perl compiler suite as a whole continues
 461  to be experimental.)
 462  
 463  =head1 New Documentation
 464  
 465  perl573delta has been added to list the differences between the
 466  (now quite obsolete) development releases 5.7.2 and 5.7.3.
 467  
 468  perl58delta and perl581delta have been added: these are the perldeltas
 469  of 5.8.0 and 5.8.1, detailing the differences respectively between
 470  5.6.0 and 5.8.0, and between 5.8.0 and 5.8.1.
 471  
 472  perlartistic has been added: it is the Artistic License in pod format,
 473  making it easier for modules to refer to it.
 474  
 475  perlcheat has been added: it is a Perl cheat sheet.
 476  
 477  perlgpl has been added: it is the GNU General Public License in pod
 478  format, making it easier for modules to refer to it.
 479  
 480  perlmacosx has been added to tell about the installation and use
 481  of Perl in Mac OS X.
 482  
 483  perlos400 has been added to tell about the installation and use
 484  of Perl in OS/400 PASE.
 485  
 486  perlreref has been added: it is a regular expressions quick reference.
 487  
 488  =head1 Performance Enhancements
 489  
 490  =head1 Installation and Configuration Improvements
 491  
 492  The UNIX standard Perl location, F</usr/bin/perl>, is no longer
 493  overwritten by default if it exists.  This change was very prudent
 494  because so many UNIX vendors already provide a F</usr/bin/perl>,
 495  but simultaneously many system utilities may depend on that
 496  exact version of Perl, so better not to overwrite it.
 497  
 498  One can now specify installation directories for site and vendor man
 499  and HTML pages, and site and vendor scripts.  See F<INSTALL>.
 500  
 501  One can now specify a destination directory for Perl installation
 502  by specifying the DESTDIR variable for C<make install>.  (This feature
 503  is slightly different from the previous C<Configure -Dinstallprefix=...>.)
 504  See F<INSTALL>.
 505  
 506  gcc versions 3.x introduced a new warning that caused a lot of noise
 507  during Perl compilation: C<gcc -Ialreadyknowndirectory (warning:
 508  changing search order)>.  This warning has now been avoided by
 509  Configure weeding out such directories before the compilation.
 510  
 511  One can now build subsets of Perl core modules by using the
 512  Configure flags C<-Dnoextensions=...> and C<-Donlyextensions=...>,
 513  see F<INSTALL>.
 514  
 515  =head2 Platform-specific enhancements
 516  
 517  In Cygwin Perl can now be built with threads (C<Configure -Duseithreads>).
 518  This works with both Cygwin 1.3.22 and Cygwin 1.5.3.
 519  
 520  In newer FreeBSD releases Perl 5.8.0 compilation failed because of
 521  trying to use F<malloc.h>, which in FreeBSD is just a dummy file, and
 522  a fatal error to even try to use.  Now F<malloc.h> is not used.
 523  
 524  Perl is now known to build also in Hitachi HI-UXMPP.
 525  
 526  Perl is now known to build again in LynxOS.
 527  
 528  Mac OS X now installs with Perl version number embedded in
 529  installation directory names for easier upgrading of user-compiled
 530  Perl, and the installation directories in general are more standard.
 531  In other words, the default installation no longer breaks the
 532  Apple-provided Perl.  On the other hand, with C<Configure -Dprefix=/usr>
 533  you can now really replace the Apple-supplied Perl (B<please be careful>).
 534  
 535  Mac OS X now builds Perl statically by default.  This change was done
 536  mainly for faster startup times.  The Apple-provided Perl is still
 537  dynamically linked and shared, and you can enable the sharedness for
 538  your own Perl builds by C<Configure -Duseshrplib>.
 539  
 540  Perl has been ported to IBM's OS/400 PASE environment.  The best way
 541  to build a Perl for PASE is to use an AIX host as a cross-compilation
 542  environment.  See README.os400.
 543  
 544  Yet another cross-compilation option has been added: now Perl builds
 545  on OpenZaurus, an Linux distribution based on Mandrake + Embedix for
 546  the Sharp Zaurus PDA.  See the Cross/README file.
 547  
 548  Tru64 when using gcc 3 drops the optimisation for F<toke.c> to C<-O2>
 549  because of gigantic memory use with the default C<-O3>.
 550  
 551  Tru64 can now build Perl with the newer Berkeley DBs.
 552  
 553  Building Perl on WinCE has been much enhanced, see F<README.ce>
 554  and F<README.perlce>.
 555  
 556  =head1 Selected Bug Fixes
 557  
 558  =head2 Closures, eval and lexicals
 559  
 560  There have been many fixes in the area of anonymous subs, lexicals and
 561  closures.  Although this means that Perl is now more "correct", it is
 562  possible that some existing code will break that happens to rely on
 563  the faulty behaviour.  In practice this is unlikely unless your code
 564  contains a very complex nesting of anonymous subs, evals and lexicals.
 565  
 566  =head2 Generic fixes
 567  
 568  If an input filehandle is marked C<:utf8> and Perl sees illegal UTF-8
 569  coming in when doing C<< <FH> >>, if warnings are enabled a warning is
 570  immediately given - instead of being silent about it and Perl being
 571  unhappy about the broken data later.  (The C<:encoding(utf8)> layer
 572  also works the same way.)
 573  
 574  binmode(SOCKET, ":utf8") only worked on the input side, not on the
 575  output side of the socket.  Now it works both ways.
 576  
 577  For threaded Perls certain system database functions like getpwent()
 578  and getgrent() now grow their result buffer dynamically, instead of
 579  failing.  This means that at sites with lots of users and groups the
 580  functions no longer fail by returning only partial results.
 581  
 582  Perl 5.8.0 had accidentally broken the capability for users
 583  to define their own uppercase<->lowercase Unicode mappings
 584  (as advertised by the Camel).  This feature has been fixed and
 585  is also documented better.
 586  
 587  In 5.8.0 this
 588  
 589      $some_unicode .= <FH>;
 590  
 591  didn't work correctly but instead corrupted the data.  This has now
 592  been fixed.
 593  
 594  Tied methods like FETCH etc. may now safely access tied values, i.e.
 595  resulting in a recursive call to FETCH etc.  Remember to break the
 596  recursion, though.
 597  
 598  At startup Perl blocks the SIGFPE signal away since there isn't much
 599  Perl can do about it.  Previously this blocking was in effect also for
 600  programs executed from within Perl.  Now Perl restores the original
 601  SIGFPE handling routine, whatever it was, before running external
 602  programs.
 603  
 604  Linenumbers in Perl scripts may now be greater than 65536, or 2**16.
 605  (Perl scripts have always been able to be larger than that, it's just
 606  that the linenumber for reported errors and warnings have "wrapped
 607  around".)  While scripts that large usually indicate a need to rethink
 608  your code a bit, such Perl scripts do exist, for example as results
 609  from generated code.  Now linenumbers can go all the way to
 610  4294967296, or 2**32.
 611  
 612  =head2 Platform-specific fixes
 613  
 614  Linux
 615  
 616  =over 4
 617  
 618  =item *
 619  
 620  Setting $0 works again (with certain limitations that
 621  Perl cannot do much about: see L<perlvar/$0>)
 622  
 623  =back
 624  
 625  HP-UX
 626  
 627  =over 4
 628  
 629  =item *
 630  
 631  Setting $0 now works.
 632  
 633  =back
 634  
 635  VMS
 636  
 637  =over 4
 638  
 639  =item *
 640  
 641  Configuration now tests for the presence of C<poll()>, and IO::Poll
 642  now uses the vendor-supplied function if detected.
 643  
 644  =item *
 645  
 646  A rare access violation at Perl start-up could occur if the Perl image was
 647  installed with privileges or if there was an identifier with the
 648  subsystem attribute set in the process's rightslist.  Either of these
 649  circumstances triggered tainting code that contained a pointer bug. 
 650  The faulty pointer arithmetic has been fixed.
 651  
 652  =item *
 653  
 654  The length limit on values (not keys) in the %ENV hash has been raised
 655  from 255 bytes to 32640 bytes (except when the PERL_ENV_TABLES setting
 656  overrides the default use of logical names for %ENV).  If it is
 657  necessary to access these long values from outside Perl, be aware that
 658  they are implemented using search list logical names that store the
 659  value in pieces, each 255-byte piece (up to 128 of them) being an
 660  element in the search list. When doing a lookup in %ENV from within
 661  Perl, the elements are combined into a single value.  The existing
 662  VMS-specific ability to access individual elements of a search list
 663  logical name via the $ENV{'foo;N'} syntax (where N is the search list
 664  index) is unimpaired.
 665  
 666  =item *
 667  
 668  The piping implementation now uses local rather than global DCL
 669  symbols for inter-process communication.
 670  
 671  =item *
 672  
 673  File::Find could become confused when navigating to a relative
 674  directory whose name collided with a logical name.  This problem has
 675  been corrected by adding directory syntax to relative path names, thus
 676  preventing logical name translation.
 677  
 678  =back
 679  
 680  Win32
 681  
 682  =over 4
 683  
 684  =item *
 685  
 686  A memory leak in the fork() emulation has been fixed.
 687  
 688  =item *
 689  
 690  The return value of the ioctl() built-in function was accidentally
 691  broken in 5.8.0.  This has been corrected.
 692  
 693  =item *
 694  
 695  The internal message loop executed by perl during blocking operations
 696  sometimes interfered with messages that were external to Perl.
 697  This often resulted in blocking operations terminating prematurely or
 698  returning incorrect results, when Perl was executing under environments
 699  that could generate Windows messages.  This has been corrected.
 700  
 701  =item *
 702  
 703  Pipes and sockets are now automatically in binary mode.
 704  
 705  =item *
 706  
 707  The four-argument form of select() did not preserve $! (errno) properly
 708  when there were errors in the underlying call.  This is now fixed.
 709  
 710  =item *
 711  
 712  The "CR CR LF" problem of has been fixed, binmode(FH, ":crlf")
 713  is now effectively a no-op.
 714  
 715  =back
 716  
 717  =head1 New or Changed Diagnostics
 718  
 719  All the warnings related to pack() and unpack() were made more
 720  informative and consistent.
 721  
 722  =head2 Changed "A thread exited while %d threads were running"
 723  
 724  The old version
 725  
 726      A thread exited while %d other threads were still running
 727  
 728  was misleading because the "other" included also the thread giving
 729  the warning.
 730  
 731  =head2 Removed "Attempt to clear a restricted hash"
 732  
 733  It is not illegal to clear a restricted hash, so the warning
 734  was removed.
 735  
 736  =head2 New "Illegal declaration of anonymous subroutine"
 737  
 738  You must specify the block of code for C<sub>.
 739  
 740  =head2 Changed "Invalid range "%s" in transliteration operator"
 741  
 742  The old version
 743  
 744      Invalid [] range "%s" in transliteration operator
 745  
 746  was simply wrong because there are no "[] ranges" in tr///.
 747  
 748  =head2 New "Missing control char name in \c"
 749  
 750  Self-explanatory.
 751  
 752  =head2 New "Newline in left-justified string for %s"
 753  
 754  The padding spaces would appear after the newline, which is
 755  probably not what you had in mind.
 756  
 757  =head2 New "Possible precedence problem on bitwise %c operator"
 758  
 759  If you think this
 760  
 761      $x & $y == 0
 762  
 763  tests whether the bitwise AND of $x and $y is zero,
 764  you will like this warning.
 765  
 766  =head2 New "read() on %s filehandle %s"
 767  
 768  You cannot read() (or sysread()) from a closed or unopened filehandle.
 769  
 770  =head2 New "Tied variable freed while still in use"
 771  
 772  Something pulled the plug on a live tied variable, Perl plays
 773  safe by bailing out.
 774  
 775  =head2 New "To%s: illegal mapping '%s'"
 776  
 777  An illegal user-defined Unicode casemapping was specified.
 778  
 779  =head2 New "Use of freed value in iteration"
 780  
 781  Something modified the values being iterated over.  This is not good.
 782  
 783  =head1 Changed Internals
 784  
 785  These news matter to you only if you either write XS code or like to
 786  know about or hack Perl internals (using Devel::Peek or any of the
 787  C<B::> modules counts), or like to run Perl with the C<-D> option.
 788  
 789  The embedding examples of L<perlembed> have been reviewed to be
 790  up to date and consistent: for example, the correct use of
 791  PERL_SYS_INIT3() and PERL_SYS_TERM().
 792  
 793  Extensive reworking of the pad code (the code responsible
 794  for lexical variables) has been conducted by Dave Mitchell.
 795  
 796  Extensive work on the v-strings by John Peacock.
 797  
 798  UTF-8 length and position cache: to speed up the handling of Unicode
 799  (UTF-8) scalars, a cache was introduced.  Potential problems exist if
 800  an extension bypasses the official APIs and directly modifies the PV
 801  of an SV: the UTF-8 cache does not get cleared as it should.
 802  
 803  APIs obsoleted in Perl 5.8.0, like sv_2pv, sv_catpvn, sv_catsv,
 804  sv_setsv, are again available.
 805  
 806  Certain Perl core C APIs like cxinc and regatom are no longer
 807  available at all to code outside the Perl core of the Perl core
 808  extensions.  This is intentional.  They never should have been
 809  available with the shorter names, and if you application depends on
 810  them, you should (be ashamed and) contact perl5-porters to discuss
 811  what are the proper APIs.
 812  
 813  Certain Perl core C APIs like C<Perl_list> are no longer available
 814  without their C<Perl_> prefix.  If your XS module stops working
 815  because some functions cannot be found, in many cases a simple fix is
 816  to add the C<Perl_> prefix to the function and the thread context
 817  C<aTHX_> as the first argument of the function call.  This is also how
 818  it should always have been done: letting the Perl_-less forms to leak
 819  from the core was an accident.  For cleaner embedding you can also
 820  force this for all APIs by defining at compile time the cpp define
 821  PERL_NO_SHORT_NAMES.
 822  
 823  Perl_save_bool() has been added.
 824  
 825  Regexp objects (those created with C<qr>) now have S-magic rather than
 826  R-magic.  This fixed regexps of the form /...(??{...;$x})/ to no
 827  longer ignore changes made to $x.  The S-magic avoids dropping
 828  the caching optimization and making (??{...}) constructs obscenely
 829  slow (and consequently useless).  See also L<perlguts/"Magic Variables">.
 830  Regexp::Copy was affected by this change.
 831  
 832  The Perl internal debugging macros DEBUG() and DEB() have been renamed
 833  to PERL_DEBUG() and PERL_DEB() to avoid namespace conflicts.
 834  
 835  C<-DL> removed (the leaktest had been broken and unsupported for years,
 836  use alternative debugging mallocs or tools like valgrind and Purify).
 837  
 838  Verbose modifier C<v> added for C<-DXv> and C<-Dsv>, see L<perlrun>.
 839  
 840  =head1 New Tests
 841  
 842  In Perl 5.8.0 there were about 69000 separate tests in about 700 test files,
 843  in Perl 5.9.0 there are about 77000 separate tests in about 780 test files.
 844  The exact numbers depend on the Perl configuration and on the operating
 845  system platform.
 846  
 847  =head1 Known Problems
 848  
 849  The hash randomisation mentioned in L</Incompatible Changes> is definitely
 850  problematic: it will wake dormant bugs and shake out bad assumptions.
 851  
 852  Many of the rarer platforms that worked 100% or pretty close to it
 853  with perl 5.8.0 have been left a little bit untended since their
 854  maintainers have been otherwise busy lately, and therefore there will
 855  be more failures on those platforms.  Such platforms include Mac OS
 856  Classic, IBM z/OS (and other EBCDIC platforms), and NetWare.  The most
 857  common Perl platforms (Unix and Unix-like, Microsoft platforms, and
 858  VMS) have large enough testing and expert population that they are
 859  doing well.
 860  
 861  =head2 Tied hashes in scalar context
 862  
 863  Tied hashes do not currently return anything useful in scalar context,
 864  for example when used as boolean tests:
 865  
 866      if (%tied_hash) { ... }
 867  
 868  The current nonsensical behaviour is always to return false,
 869  regardless of whether the hash is empty or has elements.
 870  
 871  The root cause is that there is no interface for the implementors of
 872  tied hashes to implement the behaviour of a hash in scalar context.
 873  
 874  =head2 Net::Ping 450_service and 510_ping_udp failures
 875  
 876  The subtests 9 and 18 of lib/Net/Ping/t/450_service.t, and the
 877  subtest 2 of lib/Net/Ping/t/510_ping_udp.t might fail if you have
 878  an unusual networking setup.  For example in the latter case the
 879  test is trying to send a UDP ping to the IP address 127.0.0.1.
 880  
 881  =head2 B::C
 882  
 883  The C-generating compiler backend B::C (the frontend being
 884  C<perlcc -c>) is even more broken than it used to be because of
 885  the extensive lexical variable changes.  (The good news is that
 886  B::Bytecode and ByteLoader are better than they used to be.)
 887  
 888  =head1 Platform Specific Problems
 889  
 890  =head2 EBCDIC Platforms
 891  
 892  IBM z/OS and other EBCDIC platforms continue to be problematic
 893  regarding Unicode support.  Many Unicode tests are skipped when
 894  they really should be fixed.
 895  
 896  =head2 Cygwin 1.5 problems
 897  
 898  In Cygwin 1.5 the F<io/tell> and F<op/sysio> tests have failures for
 899  some yet unknown reason.  In 1.5.5 the threads tests stress_cv,
 900  stress_re, and stress_string are failing unless the environment
 901  variable PERLIO is set to "perlio" (which makes also the io/tell
 902  failure go away).
 903  
 904  Perl 5.8.1 does build and work well with Cygwin 1.3: with (uname -a)
 905  C<CYGWIN_NT-5.0 ... 1.3.22(0.78/3/2) 2003-03-18 09:20 i686 ...>
 906  a 100% "make test"  was achieved with C<Configure -des -Duseithreads>.
 907  
 908  =head2 HP-UX: HP cc warnings about sendfile and sendpath
 909  
 910  With certain HP C compiler releases (e.g. B.11.11.02) you will
 911  get many warnings like this (lines wrapped for easier reading):
 912  
 913    cc: "/usr/include/sys/socket.h", line 504: warning 562:
 914      Redeclaration of "sendfile" with a different storage class specifier:
 915        "sendfile" will have internal linkage.
 916    cc: "/usr/include/sys/socket.h", line 505: warning 562:
 917      Redeclaration of "sendpath" with a different storage class specifier:
 918        "sendpath" will have internal linkage.
 919  
 920  The warnings show up both during the build of Perl and during certain
 921  lib/ExtUtils tests that invoke the C compiler.  The warning, however,
 922  is not serious and can be ignored.
 923  
 924  =head2 IRIX: t/uni/tr_7jis.t falsely failing
 925  
 926  The test t/uni/tr_7jis.t is known to report failure under 'make test'
 927  or the test harness with certain releases of IRIX (at least IRIX 6.5
 928  and MIPSpro Compilers Version 7.3.1.1m), but if run manually the test
 929  fully passes.
 930  
 931  =head2 Mac OS X: no usemymalloc
 932  
 933  The Perl malloc (C<-Dusemymalloc>) does not work at all in Mac OS X.
 934  This is not that serious, though, since the native malloc works just
 935  fine.
 936  
 937  =head2 Tru64: No threaded builds with GNU cc (gcc)
 938  
 939  In the latest Tru64 releases (e.g. v5.1B or later) gcc cannot be used
 940  to compile a threaded Perl (-Duseithreads) because the system
 941  C<< <pthread.h> >> file doesn't know about gcc.
 942  
 943  =head2 Win32: sysopen, sysread, syswrite
 944  
 945  As of the 5.8.0 release, sysopen()/sysread()/syswrite() do not behave
 946  like they used to in 5.6.1 and earlier with respect to "text" mode.
 947  These built-ins now always operate in "binary" mode (even if sysopen()
 948  was passed the O_TEXT flag, or if binmode() was used on the file
 949  handle).  Note that this issue should only make a difference for disk
 950  files, as sockets and pipes have always been in "binary" mode in the
 951  Windows port.  As this behavior is currently considered a bug,
 952  compatible behavior may be re-introduced in a future release.  Until
 953  then, the use of sysopen(), sysread() and syswrite() is not supported
 954  for "text" mode operations.
 955  
 956  =head1 TODO
 957  
 958  Here are some things that are planned for perl 5.10.0 :
 959  
 960  =over 4
 961  
 962  =item *
 963  
 964  Various Copy-On-Write techniques will be investigated in hopes
 965  of speeding up Perl.
 966  
 967  =item *
 968  
 969  CPANPLUS, Inline, and Module::Build will become core modules.
 970  
 971  =item *
 972  
 973  The ability to write true lexically scoped pragmas will be introduced,
 974  perhaps via a C<pragma> pragma.
 975  
 976  =item *
 977  
 978  Work will continue on the bytecompiler and byteloader.
 979  
 980  =item *
 981  
 982  v-strings as they currently exist are scheduled to be deprecated.  The
 983  v-less form (1.2.3) will become a "version object" when used with C<use>,
 984  C<require>, and C<$VERSION>.  $^V will also be a "version object" so the
 985  printf("%vd",...) construct will no longer be needed.  The v-ful version
 986  (v1.2.3) will become obsolete.  The equivalence of strings and v-strings (e.g.
 987  that currently 5.8.0 is equal to "\5\8\0") will go away.  B<There may be no
 988  deprecation warning for v-strings>, though: it is quite hard to detect when
 989  v-strings are being used safely, and when they are not.
 990  
 991  =back
 992  
 993  =head1 Reporting Bugs
 994  
 995  If you find what you think is a bug, you might check the articles
 996  recently posted to the comp.lang.perl.misc newsgroup and the perl
 997  bug database at F<http://bugs.perl.org/>.  There may also be
 998  information at F<http://www.perl.com/>, the Perl Home Page.
 999  
1000  If you believe you have an unreported bug, please run the B<perlbug>
1001  program included with your release.  Be sure to trim your bug down
1002  to a tiny but sufficient test case.  Your bug report, along with the
1003  output of C<perl -V>, will be sent off to perlbug@perl.org to be
1004  analysed by the Perl porting team.  You can browse and search
1005  the Perl 5 bugs at F<http://bugs.perl.org/>.
1006  
1007  =head1 SEE ALSO
1008  
1009  The F<Changes> file for exhaustive details on what changed.
1010  
1011  The F<INSTALL> file for how to build Perl.
1012  
1013  The F<README> file for general stuff.
1014  
1015  The F<Artistic> and F<Copying> files for copyright information.
1016  
1017  =cut