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1 | =encoding utf8 |
2 | |
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3 | =head1 NAME |
4 | |
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5 | perl593delta - what is new for perl v5.9.3 |
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6 | |
7 | =head1 DESCRIPTION |
8 | |
9 | This document describes differences between the 5.9.2 and the 5.9.3 |
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10 | development releases. See L<perl590delta>, L<perl591delta> and |
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11 | L<perl592delta> for the differences between 5.8.0 and 5.9.2. |
12 | |
13 | =head1 Incompatible Changes |
14 | |
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15 | =head2 Parsing of C<-f _> |
16 | |
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17 | The identifier C<_> is now forced to be a bareword after a filetest |
18 | operator. This solves a number of misparsing issues when a global C<_> |
19 | subroutine is defined. |
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20 | |
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21 | =head2 C<mkdir()> |
22 | |
23 | C<mkdir()> without arguments now defaults to C<$_>. |
24 | |
25 | =head2 Magic goto and eval |
26 | |
27 | The construct C<eval { goto &foo }> is now disallowed. (Note that the |
28 | similar construct, but with C<eval("")> instead, was already forbidden.) |
29 | |
30 | =head2 C<$#> has been removed |
31 | |
32 | The deprecated C<$#> variable (output format for numbers) has been |
33 | removed. A new warning, C<$# is no longer supported>, has been added. |
34 | |
35 | =head2 C<:unique> |
36 | |
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37 | The C<:unique> attribute has been made a no-op, since its current |
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38 | implementation was fundamentally flawed and not threadsafe. |
39 | |
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40 | =head2 Scoping of the C<sort> pragma |
41 | |
42 | The C<sort> pragma is now lexically scoped. Its effect used to be global. |
43 | |
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44 | =head1 Core Enhancements |
45 | |
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46 | =head2 The C<feature> pragma |
47 | |
48 | The C<feature> pragma is used to enable new syntax that would break Perl's |
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49 | backwards-compatibility with older releases of the language. It's a lexical |
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50 | pragma, like C<strict> or C<warnings>. |
51 | |
52 | Currently the following new features are available: C<switch> (adds a |
53 | switch statement), C<~~> (adds a Perl 6-like smart match operator), C<say> |
54 | (adds a C<say> built-in function), and C<err> (adds an C<err> keyword). |
55 | Those features are described below. |
56 | |
57 | Note that C<err> low-precedence defined-or operator used to be enabled by |
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58 | default (although as a weak keyword, meaning that any function would |
59 | override it). It's now only recognized when explicitly turned on (and is |
60 | then a regular keyword). |
61 | |
62 | Those features, and the C<feature> pragma itself, have been contributed by |
63 | Robin Houston. |
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64 | |
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65 | =head2 Switch and Smart Match operator |
66 | |
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67 | Perl 5 now has a switch statement. It's available when C<use feature |
68 | 'switch'> is in effect. This feature introduces three new keywords, |
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69 | C<given>, C<when>, and C<default>: |
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70 | |
71 | given ($foo) { |
72 | when (/^abc/) { $abc = 1; } |
73 | when (/^def/) { $def = 1; } |
74 | when (/^xyz/) { $xyz = 1; } |
75 | default { $nothing = 1; } |
76 | } |
77 | |
78 | A more complete description of how Perl matches the switch variable |
79 | against the C<when> conditions is given in L<perlsyn/"Switch statements">. |
80 | |
81 | This kind of match is called I<smart match>, and it's also possible to use |
82 | it outside of switch statements, via the new C<~~> operator (enabled via |
83 | the C<use feature '~~'> directive). See L<perlsyn/"Smart matching in |
84 | detail">. |
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85 | |
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86 | =head2 C<say()> |
87 | |
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88 | say() is a new built-in, only available when C<use feature 'say'> is in |
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89 | effect, that is similar to print(), but that implicitly appends a newline |
90 | to the printed string. See L<perlfunc/say>. |
91 | |
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92 | =head2 C<CLONE_SKIP()> |
93 | |
94 | Perl has now support for the C<CLONE_SKIP> special subroutine. Like |
95 | C<CLONE>, C<CLONE_SKIP> is called once per package; however, it is called |
96 | just before cloning starts, and in the context of the parent thread. If it |
97 | returns a true value, then no objects of that class will be cloned. See |
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98 | L<perlmod> for details. (Contributed by Dave Mitchell.) |
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99 | |
100 | =head2 C<${^CHILD_ERROR_NATIVE}> |
101 | |
102 | A new internal variable, C<${^CHILD_ERROR_NATIVE}>, gives the native |
103 | status returned by the last pipe close, backtick command, successful call |
104 | to wait() or waitpid(), or from the system() operator. See L<perlrun> for |
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105 | details. (Contributed by Gisle Aas.) |
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106 | |
107 | =head2 Assertions |
108 | |
109 | The support for assertions, introduced in perl 5.9.0, has been improved. |
110 | The syntax for the C<-A> command-line switch has changed; it now accepts |
111 | an optional module name, defaulting to C<assertions::activate>. See |
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112 | L<assertions> and L<perlrun>. (Contributed by Salvador Fandiño García.) |
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113 | |
114 | =head2 Unicode Character Database 4.1.0 |
115 | |
116 | The copy of the Unicode Character Database included in Perl 5.9 has |
117 | been updated to 4.1.0. |
118 | |
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119 | =head2 C<no VERSION> |
120 | |
121 | You can now use C<no> followed by a version number to specify that you |
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122 | want to use a version of perl older than the specified one. |
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123 | |
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124 | =head2 Recursive sort subs |
125 | |
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126 | You can now use recursive subroutines with sort(), thanks to Robin Houston. |
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127 | |
128 | =head2 Effect of pragmas in eval |
129 | |
130 | The compile-time value of the C<%^H> hint variable can now propagate into |
131 | eval("")uated code. This makes it more useful to implement lexical |
132 | pragmas. |
133 | |
134 | As a side-effect of this, the overloaded-ness of constants now propagates |
135 | into eval(""). |
136 | |
137 | =head2 New B<-E> command-line switch |
138 | |
139 | B<-E> is equivalent to B<-e>, but it implicitly enables all |
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140 | optional features (like C<use feature ":5.10">). |
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141 | |
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142 | =head2 C<chdir>, C<chmod> and C<chown> on filehandles |
143 | |
144 | C<chdir>, C<chmod> and C<chown> can now work on filehandles as well as |
145 | filenames, if the system supports respectively C<fchdir>, C<fchmod> and |
146 | C<fchown>, thanks to a patch provided by Gisle Aas. |
147 | |
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148 | =head2 OS groups |
149 | |
150 | C<$(> and C<$)> now return groups in the order where the OS returns them, |
151 | thanks to Gisle Aas. This wasn't previously the case. |
152 | |
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153 | =head1 Modules and Pragmata |
154 | |
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155 | =head2 New Core Modules |
156 | |
157 | =over 4 |
158 | |
159 | =item * |
160 | |
161 | A new pragma, C<feature>, has been added; see above in L</"Core |
162 | Enhancements">. |
163 | |
164 | =item * |
165 | |
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166 | C<assertions::compat>, also available on CPAN, allows the use of assertions on |
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167 | perl versions prior to 5.9.0 (that is the first one to natively support |
168 | them). |
169 | |
170 | =item * |
171 | |
172 | C<Math::BigInt::FastCalc> is an XS-enabled, and thus faster, version of |
173 | C<Math::BigInt::Calc>. |
174 | |
175 | =item * |
176 | |
177 | C<Compress::Zlib> is an interface to the zlib compression library. It |
178 | comes with a bundled version of zlib, so having a working zlib is not a |
179 | prerequisite to install it. It's used by C<Archive::Tar> (see below). |
180 | |
181 | =item * |
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182 | |
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183 | C<IO::Zlib> is an C<IO::>-style interface to C<Compress::Zlib>. |
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184 | |
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185 | =item * |
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186 | |
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187 | C<Archive::Tar> is a module to manipulate C<tar> archives. |
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188 | |
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189 | =item * |
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190 | |
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191 | C<Digest::SHA> is a module used to calculate many types of SHA digests, |
192 | has been included for SHA support in the CPAN module. |
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193 | |
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194 | =item * |
195 | |
196 | C<ExtUtils::CBuilder> and C<ExtUtils::ParseXS> have been added. |
197 | |
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198 | =back |
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199 | |
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200 | =head1 Utility Changes |
201 | |
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202 | =head2 C<ptar> |
203 | |
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204 | C<ptar> is a pure perl implementation of C<tar>, that comes with |
205 | C<Archive::Tar>. |
206 | |
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207 | =head2 C<ptardiff> |
208 | |
209 | C<ptardiff> is a small script used to generate a diff between the contents |
210 | of a tar archive and a directory tree. Like C<ptar>, it comes with |
211 | C<Archive::Tar>. |
212 | |
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213 | =head2 C<shasum> |
214 | |
215 | This command-line utility, used to print or to check SHA digests, comes |
216 | with the new C<Digest::SHA> module. |
217 | |
218 | =head2 C<h2xs> enhancements |
219 | |
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220 | C<h2xs> implements a new option C<--use-xsloader> to force use of |
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221 | C<XSLoader> even in backwards compatible modules. |
222 | |
223 | The handling of authors' names that had apostrophes has been fixed. |
224 | |
225 | Any enums with negative values are now skipped. |
226 | |
227 | =head2 C<perlivp> enhancements |
228 | |
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229 | C<perlivp> no longer checks for F<*.ph> files by default. Use the new C<-a> |
230 | option to run I<all> tests. |
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231 | |
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232 | =head1 Documentation |
233 | |
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234 | =head2 Perl Glossary |
235 | |
236 | The L<perlglossary> manpage is a glossary of terms used in the Perl |
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237 | documentation, technical and otherwise, kindly provided by O'Reilly Media, |
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238 | Inc. |
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239 | |
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240 | L<perltodo> now lists a rough roadmap to Perl 5.10. |
241 | |
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242 | =head1 Performance Enhancements |
243 | |
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244 | =head2 XS-assisted SWASHGET |
245 | |
246 | Some pure-perl code that perl was using to retrieve Unicode properties and |
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247 | transliteration mappings has been reimplemented in XS. |
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248 | |
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249 | =head2 Constant subroutines |
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250 | |
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251 | The interpreter internals now support a far more memory efficient form of |
252 | inlineable constants. Storing a reference to a constant value in a symbol |
253 | table is equivalent to a full typeglob referencing a constant subroutine, |
254 | but using about 400 bytes less memory. This proxy constant subroutine is |
255 | automatically upgraded to a real typeglob with subroutine if necessary. |
256 | The approach taken is analogous to the existing space optimisation for |
257 | subroutine stub declarations, which are stored as plain scalars in place |
258 | of the full typeglob. |
259 | |
260 | Several of the core modules have been converted to use this feature for |
261 | their system dependent constants - as a result C<use POSIX;> now takes about |
262 | 200K less memory. |
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263 | |
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264 | =head2 C<PERL_DONT_CREATE_GVSV> |
265 | |
266 | The new compilation flag C<PERL_DONT_CREATE_GVSV>, introduced as an option |
267 | in perl 5.8.8, is turned on by default in perl 5.9.3. It prevents perl |
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268 | from creating an empty scalar with every new typeglob. See L<perl589delta> |
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269 | for details. |
270 | |
271 | =head2 Weak references are cheaper |
272 | |
273 | Weak reference creation is now I<O(1)> rather than I<O(n)>, courtesy of |
274 | Nicholas Clark. Weak reference deletion remains I<O(n)>, but if deletion only |
275 | happens at program exit, it may be skipped completely. |
276 | |
277 | =head2 sort() enhancements |
278 | |
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279 | Salvador Fandiño provided improvements to reduce the memory usage of C<sort> |
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280 | and to speed up some cases. |
281 | |
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282 | =head1 Installation and Configuration Improvements |
283 | |
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284 | =head2 Compilation improvements |
285 | |
286 | Parallel makes should work properly now, although there may still be problems |
287 | if C<make test> is instructed to run in parallel. |
288 | |
289 | Building with Borland's compilers on Win32 should work more smoothly. In |
290 | particular Steve Hay has worked to side step many warnings emitted by their |
291 | compilers and at least one C compiler internal error. |
292 | |
293 | Perl extensions on Windows now can be statically built into the Perl DLL, |
294 | thanks to a work by Vadim Konovalov. |
295 | |
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296 | =head2 New Or Improved Platforms |
297 | |
298 | Perl is being ported to Symbian OS. See L<perlsymbian> for more |
299 | information. |
300 | |
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301 | The VMS port has been improved. See L<perlvms>. |
302 | |
303 | DynaLoader::dl_unload_file() now works on Windows. |
304 | |
305 | Portability of Perl on various recent compilers on Windows has been |
306 | improved (Borland C++, Visual C++ 7.0). |
307 | |
308 | =head2 New probes |
309 | |
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310 | C<Configure> will now detect C<clearenv> and C<unsetenv>, thanks to a |
311 | patch from Alan Burlison. It will also probe for C<futimes> (and use it |
312 | internally if available), and whether C<sprintf> correctly returns the |
313 | length of the formatted string. |
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314 | |
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315 | =head2 Module auxiliary files |
316 | |
317 | README files and changelogs for CPAN modules bundled with perl are no |
318 | longer installed. |
319 | |
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320 | =head1 Selected Bug Fixes |
321 | |
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322 | =head2 C<defined $$x> |
323 | |
324 | C<use strict "refs"> was ignoring taking a hard reference in an argument |
325 | to defined(), as in : |
326 | |
327 | use strict "refs"; |
328 | my $x = "foo"; |
329 | if (defined $$x) {...} |
330 | |
331 | This now correctly produces the run-time error C<Can't use string as a |
332 | SCALAR ref while "strict refs" in use>. (However, C<defined @$foo> and |
333 | C<defined %$foo> are still allowed. Those constructs are discouraged |
334 | anyway.) |
335 | |
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336 | =head2 Calling CORE::require() |
337 | |
338 | CORE::require() and CORE::do() were always parsed as require() and do() |
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339 | when they were overridden. This is now fixed. |
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340 | |
341 | =head2 Subscripts of slices |
342 | |
343 | You can now use a non-arrowed form for chained subscripts after a list |
344 | slice, like in: |
345 | |
346 | ({foo => "bar"})[0]{foo} |
347 | |
348 | This used to be a syntax error; a C<< -> >> was required. |
349 | |
350 | =head2 Remove over-optimisation |
351 | |
352 | Perl 5.9.2 introduced a change so that assignments of C<undef> to a |
353 | scalar, or of an empty list to an array or a hash, were optimised out. As |
354 | this could cause problems when C<goto> jumps were involved, this change |
355 | was backed out. |
356 | |
357 | =head2 sprintf() fixes |
358 | |
359 | Using the sprintf() function with some formats could lead to a buffer |
360 | overflow in some specific cases. This has been fixed, along with several |
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361 | other bugs, notably in bounds checking. |
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362 | |
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363 | In related fixes, it was possible for badly written code that did not follow |
364 | the documentation of C<Sys::Syslog> to have formatting vulnerabilities. |
365 | C<Sys::Syslog> has been changed to protect people from poor quality third |
366 | party code. |
367 | |
368 | =head2 no warnings 'category' works correctly with -w |
369 | |
370 | Previously when running with warnings enabled globally via C<-w>, selective |
371 | disabling of specific warning categories would actually turn off all warnings. |
372 | This is now fixed; now C<no warnings 'io';> will only turn off warnings in the |
373 | C<io> class. Previously it would erroneously turn off all warnings. |
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374 | |
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375 | =head2 Smaller fixes |
376 | |
377 | =over 4 |
378 | |
379 | =item * |
380 | |
381 | C<FindBin> now works better with directories where access rights are more |
382 | restrictive than usual. |
383 | |
384 | =item * |
385 | |
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386 | Several memory leaks in ithreads were closed. Also, ithreads were made |
387 | less memory-intensive. |
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388 | |
389 | =item * |
390 | |
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391 | Trailing spaces are now trimmed from C<$!> and C<$^E>. |
392 | |
393 | =item * |
394 | |
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395 | Operations that require perl to read a process's list of groups, such as reads |
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396 | of C<$(> and C<$)>, now dynamically allocate memory rather than using a |
397 | fixed sized array. The fixed size array could cause C stack exhaustion on |
398 | systems configured to use large numbers of groups. |
399 | |
400 | =item * |
401 | |
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402 | C<PerlIO::scalar> now works better with non-default C<$/> settings. |
403 | |
404 | =item * |
405 | |
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406 | The C<x> repetition operator is now able to operate on C<qw//> lists. This |
407 | used to raise a syntax error. |
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408 | |
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409 | =item * |
410 | |
411 | The debugger now traces correctly execution in eval("")uated code that |
412 | contains #line directives. |
413 | |
414 | =item * |
415 | |
416 | The value of the C<open> pragma is no longer ignored for three-argument |
417 | opens. |
418 | |
419 | =item * |
420 | |
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421 | Perl will now use the C library calls C<unsetenv> and C<clearenv> if present |
422 | to delete keys from C<%ENV> and delete C<%ENV> entirely, thanks to a patch |
423 | from Alan Burlison. |
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424 | |
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425 | =back |
426 | |
427 | =head2 More Unicode Fixes |
428 | |
429 | =over 4 |
430 | |
431 | =item * |
432 | |
433 | chr() on a negative value now gives C<\x{FFFD}>, the Unicode replacement |
434 | character, unless when the C<bytes> pragma is in effect, where the low |
435 | eight bytes of the value are used. |
436 | |
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437 | =item * |
438 | |
439 | Some case insensitive matches between UTF-8 encoded data and 8 bit regexps, |
440 | and vice versa, could give malformed character warnings. These have been |
441 | fixed by Dave Mitchell and Yves Orton. |
442 | |
443 | =item * |
444 | |
445 | C<lcfirst> and C<ucfirst> could corrupt the string for certain cases where |
446 | the length UTF-8 encoding of the string in lower case, upper case or title |
447 | case differed. This was fixed by Nicholas Clark. |
448 | |
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449 | =back |
450 | |
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451 | =head1 New or Changed Diagnostics |
452 | |
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453 | =head2 Attempt to set length of freed array |
454 | |
455 | This is a new warning, produced in situations like the following one: |
456 | |
457 | $r = do {my @a; \$#a}; |
458 | $$r = 503; |
459 | |
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460 | =head2 Non-string passed as bitmask |
461 | |
462 | This is a new warning, produced when number has been passed as a argument to |
463 | select(), instead of a bitmask. |
464 | |
465 | # Wrong, will now warn |
466 | $rin = fileno(STDIN); |
467 | ($nfound,$timeleft) = select($rout=$rin, undef, undef, $timeout); |
468 | |
469 | # Should be |
470 | $rin = ''; |
471 | vec($rin,fileno(STDIN),1) = 1; |
472 | ($nfound,$timeleft) = select($rout=$rin, undef, undef, $timeout); |
473 | |
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474 | =head2 Search pattern not terminated or ternary operator parsed as search pattern |
475 | |
476 | This syntax error indicates that the lexer couldn't find the final |
477 | delimiter of a C<?PATTERN?> construct. Mentioning the ternary operator in |
478 | this error message makes syntax diagnostic easier. |
479 | |
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480 | =head2 "%s" variable %s masks earlier declaration |
481 | |
482 | This warning is now emitted in more consistent cases; in short, when one |
483 | of the declarations involved is a C<my> variable: |
484 | |
485 | my $x; my $x; # warns |
486 | my $x; our $x; # warns |
487 | our $x; my $x; # warns |
488 | |
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489 | On the other hand, the following: |
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490 | |
491 | our $x; our $x; |
492 | |
493 | now gives a C<"our" variable %s redeclared> warning. |
494 | |
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495 | =head2 readdir()/closedir()/etc. attempted on invalid dirhandle |
496 | |
497 | These new warnings are now emitted when a dirhandle is used but is |
498 | either closed or not really a dirhandle. |
499 | |
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500 | =head1 Changed Internals |
501 | |
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502 | In general, the source code of perl has been refactored, tied up, and |
503 | optimized in many places. Also, memory management and allocation has been |
504 | improved in a couple of points. |
505 | |
506 | Andy Lester supplied many improvements to determine which function |
507 | parameters and local variables could actually be declared C<const> to the C |
508 | compiler. Steve Peters provided new C<*_set> macros and reworked the core to |
509 | use these rather than assigning to macros in LVALUE context. |
510 | |
511 | Dave Mitchell improved the lexer debugging output under C<-DT>. |
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512 | |
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513 | A new file, F<mathoms.c>, has been added. It contains functions that are |
514 | no longer used in the perl core, but that remain available for binary or |
515 | source compatibility reasons. However, those functions will not be |
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516 | compiled in if you add C<-DNO_MATHOMS> in the compiler flags. |
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517 | |
518 | The C<AvFLAGS> macro has been removed. |
519 | |
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520 | The C<av_*()> functions, used to manipulate arrays, no longer accept null |
521 | C<AV*> parameters. |
522 | |
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523 | =head2 B:: modules inheritance changed |
524 | |
525 | The inheritance hierarchy of C<B::> modules has changed; C<B::NV> now |
526 | inherits from C<B::SV> (it used to inherit from C<B::IV>). |
527 | |
496c75d0 |
528 | =head1 Reporting Bugs |
529 | |
530 | If you find what you think is a bug, you might check the articles |
531 | recently posted to the comp.lang.perl.misc newsgroup and the perl |
532 | bug database at http://bugs.perl.org/ . There may also be |
533 | information at http://www.perl.org/ , the Perl Home Page. |
534 | |
535 | If you believe you have an unreported bug, please run the B<perlbug> |
536 | program included with your release. Be sure to trim your bug down |
537 | to a tiny but sufficient test case. Your bug report, along with the |
538 | output of C<perl -V>, will be sent off to perlbug@perl.org to be |
539 | analysed by the Perl porting team. |
540 | |
541 | =head1 SEE ALSO |
542 | |
543 | The F<Changes> file for exhaustive details on what changed. |
544 | |
545 | The F<INSTALL> file for how to build Perl. |
546 | |
547 | The F<README> file for general stuff. |
548 | |
549 | The F<Artistic> and F<Copying> files for copyright information. |
550 | |
551 | =cut |