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1 | =head1 NAME |
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2 | |
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3 | perldelta - what is new for perl v5.9.0 |
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4 | |
5 | =head1 DESCRIPTION |
6 | |
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7 | This document describes differences between the 5.8.0 release and |
8 | the 5.9.0 release. |
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9 | |
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10 | =head1 Incompatible Changes |
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11 | |
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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 | |
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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 | |
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120 | =head1 Core Enhancements |
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121 | |
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122 | =head2 Assertions |
123 | |
124 | Perl 5.9.0 has experimental support for assertions. Note that hhe 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 | |
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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 |
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214 | array method. This behaviour is now optional. If the tied array class |
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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 | |
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219 | =head2 Tied hashes in scalar context |
220 | |
221 | As of perl 5.8.2, tied hashes did not return anything useful in scalar |
222 | context, for example when used as boolean tests: |
223 | |
224 | if (%tied_hash) { ... } |
225 | |
226 | The old nonsensical behaviour was always to return false, |
227 | regardless of whether the hash is empty or has elements. |
228 | |
229 | There is now an interface for the implementors of tied hashes to implement |
230 | the behaviour of a hash in scalar context, via the SCALAR method (see |
231 | L<perltie>). Without a SCALAR method, perl will try to guess whether |
232 | the hash is empty, by testing if it's inside an iteration (in this case |
233 | it can't be empty) or by calling FIRSTKEY. |
234 | |
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235 | =head2 local ${$x} |
236 | |
237 | The syntaxes |
238 | |
239 | local ${$x} |
240 | local @{$x} |
241 | local %{$x} |
242 | |
243 | now do localise variables, given that the $x is a valid variable name. |
244 | |
245 | =head2 Unicode Character Database 4.0.0 |
246 | |
247 | The copy of the Unicode Character Database included in Perl 5.8 has |
248 | been updated to 4.0.0 from 3.2.0. This means for example that the |
249 | Unicode character properties are as in Unicode 4.0.0. |
250 | |
251 | =head2 Miscellaneous Enhancements |
252 | |
253 | C<unpack()> now defaults to unpacking the C<$_>. |
254 | |
255 | C<map> in void context is no longer expensive. C<map> is now context |
256 | aware, and will not construct a list if called in void context. |
257 | |
258 | If a socket gets closed by the server while printing to it, the client |
259 | now gets a SIGPIPE. While this new feature was not planned, it fell |
260 | naturally out of PerlIO changes, and is to be considered an accidental |
261 | feature. |
262 | |
263 | PerlIO::get_layers(FH) returns the names of the PerlIO layers |
264 | active on a filehandle. |
265 | |
266 | PerlIO::via layers can now have an optional UTF8 method to |
267 | indicate whether the layer wants to "auto-:utf8" the stream. |
268 | |
269 | utf8::is_utf8() has been added as a quick way to test whether |
270 | a scalar is encoded internally in UTF-8 (Unicode). |
271 | |
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272 | =head1 Modules and Pragmata |
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273 | |
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274 | =head2 Updated Modules And Pragmata |
275 | |
276 | The following modules and pragmata have been updated since Perl 5.8.0: |
277 | |
278 | =over 4 |
279 | |
280 | =item base |
281 | |
282 | =item B::Bytecode |
283 | |
284 | In much better shape than it used to be. Still far from perfect, but |
285 | maybe worth a try. |
286 | |
287 | =item B::Concise |
288 | |
289 | =item B::Deparse |
290 | |
291 | =item Benchmark |
292 | |
293 | An optional feature, C<:hireswallclock>, now allows for high |
294 | resolution wall clock times (uses Time::HiRes). |
295 | |
296 | =item ByteLoader |
297 | |
298 | See B::Bytecode. |
299 | |
300 | =item bytes |
301 | |
302 | Now has bytes::substr. |
303 | |
304 | =item CGI |
305 | |
306 | =item charnames |
307 | |
308 | One can now have custom character name aliases. |
309 | |
310 | =item CPAN |
311 | |
312 | There is now a simple command line frontend to the CPAN.pm |
313 | module called F<cpan>. |
314 | |
315 | =item Data::Dumper |
316 | |
317 | A new option, Pair, allows choosing the separator between hash keys |
318 | and values. |
319 | |
320 | =item DB_File |
321 | |
322 | =item Devel::PPPort |
323 | |
324 | =item Digest::MD5 |
325 | |
326 | =item Encode |
327 | |
328 | Significant updates on the encoding pragma functionality |
329 | (tr/// and the DATA filehandle, formats). |
330 | |
331 | If a filehandle has been marked as to have an encoding, unmappable |
332 | characters are detected already during input, not later (when the |
333 | corrupted data is being used). |
334 | |
335 | The ISO 8859-6 conversion table has been corrected (the 0x30..0x39 |
336 | erroneously mapped to U+0660..U+0669, instead of U+0030..U+0039). The |
337 | GSM 03.38 conversion did not handle escape sequences correctly. The |
338 | UTF-7 encoding has been added (making Encode feature-complete with |
339 | Unicode::String). |
340 | |
341 | =item fields |
342 | |
343 | =item libnet |
344 | |
345 | =item Math::BigInt |
346 | |
347 | A lot of bugs have been fixed since v1.60, the version included in Perl |
348 | v5.8.0. Especially noteworthy are the bug in Calc that caused div and mod to |
349 | fail for some large values, and the fixes to the handling of bad inputs. |
350 | |
351 | Some new features were added, e.g. the broot() method, you can now pass |
352 | parameters to config() to change some settings at runtime, and it is now |
353 | possible to trap the creation of NaN and infinity. |
354 | |
355 | As usual, some optimizations took place and made the math overall a tad |
356 | faster. In some cases, quite a lot faster, actually. Especially alternative |
357 | libraries like Math::BigInt::GMP benefit from this. In addition, a lot of the |
358 | quite clunky routines like fsqrt() and flog() are now much much faster. |
359 | |
360 | =item MIME::Base64 |
361 | |
362 | =item NEXT |
363 | |
364 | Diamond inheritance now works. |
365 | |
366 | =item Net::Ping |
367 | |
368 | =item PerlIO::scalar |
369 | |
370 | Reading from non-string scalars (like the special variables, see |
371 | L<perlvar>) now works. |
372 | |
373 | =item podlators |
374 | |
375 | =item Pod::LaTeX |
376 | |
377 | =item PodParsers |
378 | |
379 | =item Pod::Perldoc |
380 | |
381 | Complete rewrite. As a side-effect, no longer refuses to startup when |
382 | run by root. |
383 | |
384 | =item Scalar::Util |
385 | |
386 | New utilities: refaddr, isvstring, looks_like_number, set_prototype. |
387 | |
388 | =item Storable |
389 | |
390 | Can now store code references (via B::Deparse, so not foolproof). |
391 | |
392 | =item strict |
393 | |
394 | Earlier versions of the strict pragma did not check the parameters |
395 | implicitly passed to its "import" (use) and "unimport" (no) routine. |
396 | This caused the false idiom such as: |
397 | |
398 | use strict qw(@ISA); |
399 | @ISA = qw(Foo); |
400 | |
401 | This however (probably) raised the false expectation that the strict |
402 | refs, vars and subs were being enforced (and that @ISA was somehow |
403 | "declared"). But the strict refs, vars, and subs are B<not> enforced |
404 | when using this false idiom. |
405 | |
406 | Starting from Perl 5.8.1, the above B<will> cause an error to be |
407 | raised. This may cause programs which used to execute seemingly |
408 | correctly without warnings and errors to fail when run under 5.8.1. |
409 | This happens because |
410 | |
411 | use strict qw(@ISA); |
412 | |
413 | will now fail with the error: |
414 | |
415 | Unknown 'strict' tag(s) '@ISA' |
416 | |
417 | The remedy to this problem is to replace this code with the correct idiom: |
418 | |
419 | use strict; |
420 | use vars qw(@ISA); |
421 | @ISA = qw(Foo); |
422 | |
423 | =item Term::ANSIcolor |
424 | |
425 | =item Test::Harness |
426 | |
427 | Now much more picky about extra or missing output from test scripts. |
428 | |
429 | =item Test::More |
430 | |
431 | =item Test::Simple |
432 | |
433 | =item Text::Balanced |
434 | |
435 | =item Time::HiRes |
436 | |
437 | Use of nanosleep(), if available, allows mixing subsecond sleeps with |
438 | alarms. |
439 | |
440 | =item threads |
441 | |
442 | Several fixes, for example for join() problems and memory |
443 | leaks. In some platforms (like Linux) that use glibc the minimum memory |
444 | footprint of one ithread has been reduced by several hundred kilobytes. |
445 | |
446 | =item threads::shared |
447 | |
448 | Many memory leaks have been fixed. |
449 | |
450 | =item Unicode::Collate |
451 | |
452 | =item Unicode::Normalize |
453 | |
454 | =item Win32::GetFolderPath |
455 | |
456 | =item Win32::GetOSVersion |
457 | |
458 | Now returns extra information. |
459 | |
460 | =back |
461 | |
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462 | =head1 Utility Changes |
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463 | |
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464 | The C<h2xs> utility now produces a more modern layout: |
465 | F<Foo-Bar/lib/Foo/Bar.pm> instead of F<Foo/Bar/Bar.pm>. |
466 | Also, the boilerplate test is now called F<t/Foo-Bar.t> |
467 | instead of F<t/1.t>. |
468 | |
469 | The Perl debugger (F<lib/perl5db.pl>) has now been extensively |
470 | documented and bugs found while documenting have been fixed. |
471 | |
472 | C<perldoc> has been rewritten from scratch to be more robust and |
473 | featureful. |
474 | |
475 | C<perlcc -B> works now at least somewhat better, while C<perlcc -c> |
476 | is rather more broken. (The Perl compiler suite as a whole continues |
477 | to be experimental.) |
478 | |
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479 | C<find2perl> now assumes C<-print> as a default action. It needed to be |
480 | specified explicitly. |
481 | |
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482 | =head1 New Documentation |
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483 | |
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484 | perl573delta has been added to list the differences between the |
485 | (now quite obsolete) development releases 5.7.2 and 5.7.3. |
486 | |
487 | perl58delta and perl581delta have been added: these are the perldeltas |
488 | of 5.8.0 and 5.8.1, detailing the differences respectively between |
489 | 5.6.0 and 5.8.0, and between 5.8.0 and 5.8.1. |
490 | |
491 | perlartistic has been added: it is the Artistic License in pod format, |
492 | making it easier for modules to refer to it. |
493 | |
494 | perlcheat has been added: it is a Perl cheat sheet. |
495 | |
496 | perlgpl has been added: it is the GNU General Public License in pod |
497 | format, making it easier for modules to refer to it. |
498 | |
499 | perlmacosx has been added to tell about the installation and use |
500 | of Perl in Mac OS X. |
501 | |
502 | perlos400 has been added to tell about the installation and use |
503 | of Perl in OS/400 PASE. |
504 | |
505 | perlreref has been added: it is a regular expressions quick reference. |
506 | |
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507 | =head1 Performance Enhancements |
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508 | |
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509 | =head1 Installation and Configuration Improvements |
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510 | |
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511 | The UNIX standard Perl location, F</usr/bin/perl>, is no longer |
512 | overwritten by default if it exists. This change was very prudent |
513 | because so many UNIX vendors already provide a F</usr/bin/perl>, |
514 | but simultaneously many system utilities may depend on that |
515 | exact version of Perl, so better not to overwrite it. |
516 | |
517 | One can now specify installation directories for site and vendor man |
518 | and HTML pages, and site and vendor scripts. See F<INSTALL>. |
519 | |
520 | One can now specify a destination directory for Perl installation |
521 | by specifying the DESTDIR variable for C<make install>. (This feature |
522 | is slightly different from the previous C<Configure -Dinstallprefix=...>.) |
523 | See F<INSTALL>. |
524 | |
525 | gcc versions 3.x introduced a new warning that caused a lot of noise |
526 | during Perl compilation: C<gcc -Ialreadyknowndirectory (warning: |
527 | changing search order)>. This warning has now been avoided by |
528 | Configure weeding out such directories before the compilation. |
529 | |
530 | One can now build subsets of Perl core modules by using the |
531 | Configure flags C<-Dnoextensions=...> and C<-Donlyextensions=...>, |
532 | see F<INSTALL>. |
533 | |
534 | =head2 Platform-specific enhancements |
535 | |
536 | In Cygwin Perl can now be built with threads (C<Configure -Duseithreads>). |
537 | This works with both Cygwin 1.3.22 and Cygwin 1.5.3. |
538 | |
539 | In newer FreeBSD releases Perl 5.8.0 compilation failed because of |
540 | trying to use F<malloc.h>, which in FreeBSD is just a dummy file, and |
541 | a fatal error to even try to use. Now F<malloc.h> is not used. |
542 | |
543 | Perl is now known to build also in Hitachi HI-UXMPP. |
544 | |
545 | Perl is now known to build again in LynxOS. |
546 | |
547 | Mac OS X now installs with Perl version number embedded in |
548 | installation directory names for easier upgrading of user-compiled |
549 | Perl, and the installation directories in general are more standard. |
550 | In other words, the default installation no longer breaks the |
551 | Apple-provided Perl. On the other hand, with C<Configure -Dprefix=/usr> |
552 | you can now really replace the Apple-supplied Perl (B<please be careful>). |
553 | |
554 | Mac OS X now builds Perl statically by default. This change was done |
555 | mainly for faster startup times. The Apple-provided Perl is still |
556 | dynamically linked and shared, and you can enable the sharedness for |
557 | your own Perl builds by C<Configure -Duseshrplib>. |
558 | |
559 | Perl has been ported to IBM's OS/400 PASE environment. The best way |
560 | to build a Perl for PASE is to use an AIX host as a cross-compilation |
561 | environment. See README.os400. |
562 | |
563 | Yet another cross-compilation option has been added: now Perl builds |
564 | on OpenZaurus, an Linux distribution based on Mandrake + Embedix for |
565 | the Sharp Zaurus PDA. See the Cross/README file. |
566 | |
567 | Tru64 when using gcc 3 drops the optimisation for F<toke.c> to C<-O2> |
568 | because of gigantic memory use with the default C<-O3>. |
569 | |
570 | Tru64 can now build Perl with the newer Berkeley DBs. |
571 | |
572 | Building Perl on WinCE has been much enhanced, see F<README.ce> |
573 | and F<README.perlce>. |
574 | |
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575 | =head1 Selected Bug Fixes |
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576 | |
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577 | =head2 Closures, eval and lexicals |
578 | |
579 | There have been many fixes in the area of anonymous subs, lexicals and |
580 | closures. Although this means that Perl is now more "correct", it is |
581 | possible that some existing code will break that happens to rely on |
582 | the faulty behaviour. In practice this is unlikely unless your code |
583 | contains a very complex nesting of anonymous subs, evals and lexicals. |
584 | |
585 | =head2 Generic fixes |
586 | |
587 | If an input filehandle is marked C<:utf8> and Perl sees illegal UTF-8 |
588 | coming in when doing C<< <FH> >>, if warnings are enabled a warning is |
589 | immediately given - instead of being silent about it and Perl being |
590 | unhappy about the broken data later. (The C<:encoding(utf8)> layer |
591 | also works the same way.) |
592 | |
593 | binmode(SOCKET, ":utf8") only worked on the input side, not on the |
594 | output side of the socket. Now it works both ways. |
595 | |
596 | For threaded Perls certain system database functions like getpwent() |
597 | and getgrent() now grow their result buffer dynamically, instead of |
598 | failing. This means that at sites with lots of users and groups the |
599 | functions no longer fail by returning only partial results. |
600 | |
601 | Perl 5.8.0 had accidentally broken the capability for users |
602 | to define their own uppercase<->lowercase Unicode mappings |
603 | (as advertised by the Camel). This feature has been fixed and |
604 | is also documented better. |
605 | |
606 | In 5.8.0 this |
607 | |
608 | $some_unicode .= <FH>; |
609 | |
610 | didn't work correctly but instead corrupted the data. This has now |
611 | been fixed. |
612 | |
613 | Tied methods like FETCH etc. may now safely access tied values, i.e. |
614 | resulting in a recursive call to FETCH etc. Remember to break the |
615 | recursion, though. |
616 | |
617 | At startup Perl blocks the SIGFPE signal away since there isn't much |
618 | Perl can do about it. Previously this blocking was in effect also for |
619 | programs executed from within Perl. Now Perl restores the original |
620 | SIGFPE handling routine, whatever it was, before running external |
621 | programs. |
622 | |
623 | Linenumbers in Perl scripts may now be greater than 65536, or 2**16. |
624 | (Perl scripts have always been able to be larger than that, it's just |
625 | that the linenumber for reported errors and warnings have "wrapped |
626 | around".) While scripts that large usually indicate a need to rethink |
627 | your code a bit, such Perl scripts do exist, for example as results |
628 | from generated code. Now linenumbers can go all the way to |
629 | 4294967296, or 2**32. |
630 | |
631 | =head2 Platform-specific fixes |
632 | |
633 | Linux |
634 | |
635 | =over 4 |
636 | |
637 | =item * |
638 | |
639 | Setting $0 works again (with certain limitations that |
640 | Perl cannot do much about: see L<perlvar/$0>) |
641 | |
642 | =back |
643 | |
644 | HP-UX |
645 | |
646 | =over 4 |
647 | |
648 | =item * |
649 | |
650 | Setting $0 now works. |
651 | |
652 | =back |
653 | |
654 | VMS |
655 | |
656 | =over 4 |
657 | |
658 | =item * |
659 | |
660 | Configuration now tests for the presence of C<poll()>, and IO::Poll |
661 | now uses the vendor-supplied function if detected. |
662 | |
663 | =item * |
664 | |
665 | A rare access violation at Perl start-up could occur if the Perl image was |
666 | installed with privileges or if there was an identifier with the |
667 | subsystem attribute set in the process's rightslist. Either of these |
668 | circumstances triggered tainting code that contained a pointer bug. |
669 | The faulty pointer arithmetic has been fixed. |
670 | |
671 | =item * |
672 | |
673 | The length limit on values (not keys) in the %ENV hash has been raised |
674 | from 255 bytes to 32640 bytes (except when the PERL_ENV_TABLES setting |
675 | overrides the default use of logical names for %ENV). If it is |
676 | necessary to access these long values from outside Perl, be aware that |
677 | they are implemented using search list logical names that store the |
678 | value in pieces, each 255-byte piece (up to 128 of them) being an |
679 | element in the search list. When doing a lookup in %ENV from within |
680 | Perl, the elements are combined into a single value. The existing |
681 | VMS-specific ability to access individual elements of a search list |
682 | logical name via the $ENV{'foo;N'} syntax (where N is the search list |
683 | index) is unimpaired. |
684 | |
685 | =item * |
686 | |
687 | The piping implementation now uses local rather than global DCL |
688 | symbols for inter-process communication. |
689 | |
690 | =item * |
691 | |
692 | File::Find could become confused when navigating to a relative |
693 | directory whose name collided with a logical name. This problem has |
694 | been corrected by adding directory syntax to relative path names, thus |
695 | preventing logical name translation. |
696 | |
697 | =back |
698 | |
699 | Win32 |
700 | |
701 | =over 4 |
702 | |
703 | =item * |
704 | |
705 | A memory leak in the fork() emulation has been fixed. |
706 | |
707 | =item * |
708 | |
709 | The return value of the ioctl() built-in function was accidentally |
710 | broken in 5.8.0. This has been corrected. |
711 | |
712 | =item * |
713 | |
714 | The internal message loop executed by perl during blocking operations |
715 | sometimes interfered with messages that were external to Perl. |
716 | This often resulted in blocking operations terminating prematurely or |
717 | returning incorrect results, when Perl was executing under environments |
718 | that could generate Windows messages. This has been corrected. |
719 | |
720 | =item * |
721 | |
722 | Pipes and sockets are now automatically in binary mode. |
723 | |
724 | =item * |
725 | |
726 | The four-argument form of select() did not preserve $! (errno) properly |
727 | when there were errors in the underlying call. This is now fixed. |
728 | |
729 | =item * |
730 | |
731 | The "CR CR LF" problem of has been fixed, binmode(FH, ":crlf") |
732 | is now effectively a no-op. |
733 | |
734 | =back |
735 | |
55e8fca7 |
736 | =head1 New or Changed Diagnostics |
f39f21d8 |
737 | |
1ea9f2df |
738 | All the warnings related to pack() and unpack() were made more |
739 | informative and consistent. |
740 | |
741 | =head2 Changed "A thread exited while %d threads were running" |
742 | |
743 | The old version |
744 | |
745 | A thread exited while %d other threads were still running |
746 | |
747 | was misleading because the "other" included also the thread giving |
748 | the warning. |
749 | |
750 | =head2 Removed "Attempt to clear a restricted hash" |
751 | |
752 | It is not illegal to clear a restricted hash, so the warning |
753 | was removed. |
754 | |
755 | =head2 New "Illegal declaration of anonymous subroutine" |
756 | |
757 | You must specify the block of code for C<sub>. |
758 | |
759 | =head2 Changed "Invalid range "%s" in transliteration operator" |
760 | |
761 | The old version |
762 | |
763 | Invalid [] range "%s" in transliteration operator |
764 | |
765 | was simply wrong because there are no "[] ranges" in tr///. |
766 | |
767 | =head2 New "Missing control char name in \c" |
768 | |
769 | Self-explanatory. |
770 | |
771 | =head2 New "Newline in left-justified string for %s" |
772 | |
773 | The padding spaces would appear after the newline, which is |
774 | probably not what you had in mind. |
775 | |
776 | =head2 New "Possible precedence problem on bitwise %c operator" |
777 | |
778 | If you think this |
779 | |
780 | $x & $y == 0 |
781 | |
782 | tests whether the bitwise AND of $x and $y is zero, |
783 | you will like this warning. |
784 | |
785 | =head2 New "read() on %s filehandle %s" |
786 | |
787 | You cannot read() (or sysread()) from a closed or unopened filehandle. |
788 | |
789 | =head2 New "Tied variable freed while still in use" |
790 | |
791 | Something pulled the plug on a live tied variable, Perl plays |
792 | safe by bailing out. |
793 | |
794 | =head2 New "To%s: illegal mapping '%s'" |
795 | |
796 | An illegal user-defined Unicode casemapping was specified. |
797 | |
798 | =head2 New "Use of freed value in iteration" |
799 | |
800 | Something modified the values being iterated over. This is not good. |
801 | |
77c8cf41 |
802 | =head1 Changed Internals |
f39f21d8 |
803 | |
1ea9f2df |
804 | These news matter to you only if you either write XS code or like to |
805 | know about or hack Perl internals (using Devel::Peek or any of the |
806 | C<B::> modules counts), or like to run Perl with the C<-D> option. |
807 | |
808 | The embedding examples of L<perlembed> have been reviewed to be |
809 | uptodate and consistent: for example, the correct use of |
810 | PERL_SYS_INIT3() and PERL_SYS_TERM(). |
811 | |
812 | Extensive reworking of the pad code (the code responsible |
813 | for lexical variables) has been conducted by Dave Mitchell. |
814 | |
815 | Extensive work on the v-strings by John Peacock. |
816 | |
817 | UTF-8 length and position cache: to speed up the handling of Unicode |
818 | (UTF-8) scalars, a cache was introduced. Potential problems exist if |
819 | an extension bypasses the official APIs and directly modifies the PV |
820 | of an SV: the UTF-8 cache does not get cleared as it should. |
821 | |
822 | APIs obsoleted in Perl 5.8.0, like sv_2pv, sv_catpvn, sv_catsv, |
823 | sv_setsv, are again available. |
824 | |
825 | Certain Perl core C APIs like cxinc and regatom are no longer |
826 | available at all to code outside the Perl core of the Perl core |
827 | extensions. This is intentional. They never should have been |
828 | available with the shorter names, and if you application depends on |
829 | them, you should (be ashamed and) contact perl5-porters to discuss |
830 | what are the proper APIs. |
831 | |
832 | Certain Perl core C APIs like C<Perl_list> are no longer available |
833 | without their C<Perl_> prefix. If your XS module stops working |
834 | because some functions cannot be found, in many cases a simple fix is |
835 | to add the C<Perl_> prefix to the function and the thread context |
836 | C<aTHX_> as the first argument of the function call. This is also how |
837 | it should always have been done: letting the Perl_-less forms to leak |
838 | from the core was an accident. For cleaner embedding you can also |
839 | force this for all APIs by defining at compile time the cpp define |
840 | PERL_NO_SHORT_NAMES. |
841 | |
842 | Perl_save_bool() has been added. |
843 | |
844 | Regexp objects (those created with C<qr>) now have S-magic rather than |
845 | R-magic. This fixed regexps of the form /...(??{...;$x})/ to no |
846 | longer ignore changes made to $x. The S-magic avoids dropping |
847 | the caching optimization and making (??{...}) constructs obscenely |
848 | slow (and consequently useless). See also L<perlguts/"Magic Variables">. |
849 | Regexp::Copy was affected by this change. |
850 | |
851 | The Perl internal debugging macros DEBUG() and DEB() have been renamed |
852 | to PERL_DEBUG() and PERL_DEB() to avoid namespace conflicts. |
853 | |
854 | C<-DL> removed (the leaktest had been broken and unsupported for years, |
855 | use alternative debugging mallocs or tools like valgrind and Purify). |
856 | |
857 | Verbose modifier C<v> added for C<-DXv> and C<-Dsv>, see L<perlrun>. |
858 | |
ebc20e9a |
859 | =head1 New Tests |
77c8cf41 |
860 | |
1ea9f2df |
861 | In Perl 5.8.0 there were about 69000 separate tests in about 700 test files, |
862 | in Perl 5.9.0 there are about 77000 separate tests in about 780 test files. |
863 | The exact numbers depend on the Perl configuration and on the operating |
864 | system platform. |
865 | |
f39f21d8 |
866 | =head1 Known Problems |
867 | |
1ea9f2df |
868 | The hash randomisation mentioned in L</Incompatible Changes> is definitely |
869 | problematic: it will wake dormant bugs and shake out bad assumptions. |
870 | |
871 | Many of the rarer platforms that worked 100% or pretty close to it |
872 | with perl 5.8.0 have been left a little bit untended since their |
873 | maintainers have been otherwise busy lately, and therefore there will |
874 | be more failures on those platforms. Such platforms include Mac OS |
875 | Classic, IBM z/OS (and other EBCDIC platforms), and NetWare. The most |
876 | common Perl platforms (Unix and Unix-like, Microsoft platforms, and |
877 | VMS) have large enough testing and expert population that they are |
878 | doing well. |
879 | |
1ea9f2df |
880 | =head2 Net::Ping 450_service and 510_ping_udp failures |
881 | |
882 | The subtests 9 and 18 of lib/Net/Ping/t/450_service.t, and the |
883 | subtest 2 of lib/Net/Ping/t/510_ping_udp.t might fail if you have |
884 | an unusual networking setup. For example in the latter case the |
885 | test is trying to send a UDP ping to the IP address 127.0.0.1. |
886 | |
887 | =head2 B::C |
888 | |
889 | The C-generating compiler backend B::C (the frontend being |
890 | C<perlcc -c>) is even more broken than it used to be because of |
891 | the extensive lexical variable changes. (The good news is that |
892 | B::Bytecode and ByteLoader are better than they used to be.) |
893 | |
51bcf69b |
894 | =head1 Platform Specific Problems |
895 | |
1ea9f2df |
896 | =head2 EBCDIC Platforms |
897 | |
898 | IBM z/OS and other EBCDIC platforms continue to be problematic |
899 | regarding Unicode support. Many Unicode tests are skipped when |
900 | they really should be fixed. |
901 | |
902 | =head2 Cygwin 1.5 problems |
903 | |
904 | In Cygwin 1.5 the F<io/tell> and F<op/sysio> tests have failures for |
905 | some yet unknown reason. In 1.5.5 the threads tests stress_cv, |
906 | stress_re, and stress_string are failing unless the environment |
907 | variable PERLIO is set to "perlio" (which makes also the io/tell |
908 | failure go away). |
909 | |
910 | Perl 5.8.1 does build and work well with Cygwin 1.3: with (uname -a) |
911 | C<CYGWIN_NT-5.0 ... 1.3.22(0.78/3/2) 2003-03-18 09:20 i686 ...> |
912 | a 100% "make test" was achieved with C<Configure -des -Duseithreads>. |
913 | |
914 | =head2 HP-UX: HP cc warnings about sendfile and sendpath |
915 | |
916 | With certain HP C compiler releases (e.g. B.11.11.02) you will |
917 | get many warnings like this (lines wrapped for easier reading): |
918 | |
919 | cc: "/usr/include/sys/socket.h", line 504: warning 562: |
920 | Redeclaration of "sendfile" with a different storage class specifier: |
921 | "sendfile" will have internal linkage. |
922 | cc: "/usr/include/sys/socket.h", line 505: warning 562: |
923 | Redeclaration of "sendpath" with a different storage class specifier: |
924 | "sendpath" will have internal linkage. |
925 | |
926 | The warnings show up both during the build of Perl and during certain |
927 | lib/ExtUtils tests that invoke the C compiler. The warning, however, |
928 | is not serious and can be ignored. |
929 | |
930 | =head2 IRIX: t/uni/tr_7jis.t falsely failing |
931 | |
932 | The test t/uni/tr_7jis.t is known to report failure under 'make test' |
933 | or the test harness with certain releases of IRIX (at least IRIX 6.5 |
934 | and MIPSpro Compilers Version 7.3.1.1m), but if run manually the test |
935 | fully passes. |
936 | |
937 | =head2 Mac OS X: no usemymalloc |
938 | |
939 | The Perl malloc (C<-Dusemymalloc>) does not work at all in Mac OS X. |
940 | This is not that serious, though, since the native malloc works just |
941 | fine. |
942 | |
943 | =head2 Tru64: No threaded builds with GNU cc (gcc) |
944 | |
945 | In the latest Tru64 releases (e.g. v5.1B or later) gcc cannot be used |
946 | to compile a threaded Perl (-Duseithreads) because the system |
947 | C<< <pthread.h> >> file doesn't know about gcc. |
948 | |
949 | =head2 Win32: sysopen, sysread, syswrite |
950 | |
951 | As of the 5.8.0 release, sysopen()/sysread()/syswrite() do not behave |
952 | like they used to in 5.6.1 and earlier with respect to "text" mode. |
953 | These built-ins now always operate in "binary" mode (even if sysopen() |
954 | was passed the O_TEXT flag, or if binmode() was used on the file |
955 | handle). Note that this issue should only make a difference for disk |
956 | files, as sockets and pipes have always been in "binary" mode in the |
957 | Windows port. As this behavior is currently considered a bug, |
958 | compatible behavior may be re-introduced in a future release. Until |
959 | then, the use of sysopen(), sysread() and syswrite() is not supported |
960 | for "text" mode operations. |
961 | |
962 | =head1 TODO |
963 | |
964 | Here are some things that are planned for perl 5.10.0 : |
965 | |
966 | =over 4 |
967 | |
968 | =item * |
969 | |
970 | Various Copy-On-Write techniques will be investigated in hopes |
971 | of speeding up Perl. |
972 | |
973 | =item * |
974 | |
975 | CPANPLUS, Inline, and Module::Build will become core modules. |
976 | |
977 | =item * |
978 | |
979 | The ability to write true lexically scoped pragmas will be introduced, |
980 | perhaps via a C<pragma> pragma. |
981 | |
982 | =item * |
983 | |
984 | Work will continue on the bytecompiler and byteloader. |
985 | |
986 | =item * |
987 | |
988 | v-strings as they currently exist are scheduled to be deprecated. The |
989 | v-less form (1.2.3) will become a "version object" when used with C<use>, |
990 | C<require>, and C<$VERSION>. $^V will also be a "version object" so the |
991 | printf("%vd",...) construct will no longer be needed. The v-ful version |
992 | (v1.2.3) will become obsolete. The equivalence of strings and v-strings (e.g. |
993 | that currently 5.8.0 is equal to "\5\8\0") will go away. B<There may be no |
994 | deprecation warning for v-strings>, though: it is quite hard to detect when |
995 | v-strings are being used safely, and when they are not. |
996 | |
997 | =back |
998 | |
cc0fca54 |
999 | =head1 Reporting Bugs |
1000 | |
d4ad863d |
1001 | If you find what you think is a bug, you might check the articles |
1002 | recently posted to the comp.lang.perl.misc newsgroup and the perl |
f02c194e |
1003 | bug database at F<http://bugs.perl.org/>. There may also be |
1004 | information at F<http://www.perl.com/>, the Perl Home Page. |
cc0fca54 |
1005 | |
1006 | If you believe you have an unreported bug, please run the B<perlbug> |
1007 | program included with your release. Be sure to trim your bug down |
1008 | to a tiny but sufficient test case. Your bug report, along with the |
d4ad863d |
1009 | output of C<perl -V>, will be sent off to perlbug@perl.org to be |
1ea9f2df |
1010 | analysed by the Perl porting team. You can browse and search |
1011 | the Perl 5 bugs at F<http://bugs.perl.org/>. |
cc0fca54 |
1012 | |
1013 | =head1 SEE ALSO |
1014 | |
1015 | The F<Changes> file for exhaustive details on what changed. |
1016 | |
1017 | The F<INSTALL> file for how to build Perl. |
1018 | |
1019 | The F<README> file for general stuff. |
1020 | |
1021 | The F<Artistic> and F<Copying> files for copyright information. |
1022 | |
cc0fca54 |
1023 | =cut |