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1 | =head1 NAME |
2 | |
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3 | perldelta - what's new for perl5.004 |
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4 | |
5 | =head1 DESCRIPTION |
6 | |
7 | This document describes differences between the 5.003 release (as |
8 | documented in I<Programming Perl>, second edition--the Camel Book) and |
9 | this one. |
10 | |
11 | =head1 Supported Environments |
12 | |
13 | Perl5.004 builds out of the box on Unix, Plan9, LynxOS, VMS, OS/2, |
14 | QNX, and AmigaOS. |
15 | |
16 | =head1 Core Changes |
17 | |
18 | Most importantly, many bugs were fixed. See the F<Changes> |
19 | file in the distribution for details. |
20 | |
21 | =head2 Compilation Option: Binary Compatibility With 5.003 |
22 | |
23 | There is a new Configure question that asks if you want to maintain |
24 | binary compatibility with Perl 5.003. If you choose binary |
25 | compatibility, you do not have to recompile your extensions, but you |
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26 | might have symbol conflicts if you embed Perl in another application, |
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27 | just as in the 5.003 release. By default, binary compatibility |
28 | is preserved at the expense of symbol table pollution. |
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29 | |
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30 | =head2 New Opcode Module and Revised Safe Module |
31 | |
32 | A new Opcode module supports the creation, manipulation and |
33 | application of opcode masks. The revised Safe module has a new API |
34 | and is implemented using the new Opcode module. Please read the new |
35 | Opcode and Safe documentation. |
36 | |
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37 | =head2 Extended Fcntl Module |
38 | |
39 | The Fcntl module now supports these new constants |
40 | |
41 | F_GETOWN F_SETOWN |
42 | O_ASYNC O_DEFER O_DSYNC O_RSYNC O_SYNC |
43 | O_EXLOCK O_SHLOCK |
44 | |
45 | provided that your operating system supports these constants. The |
46 | constants are for use with the Perl sysopen() and fcntl(). These |
47 | constants are also visible for the basic database modules like the |
48 | SDBM_File. For the exact meaning of these contants and other Fcntl |
49 | constants please refer to the fcntl() documentation of your operating |
50 | system. Unsupported constants will cause run-time errors. |
51 | |
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52 | =head2 Internal Change: FileHandle Deprecated |
53 | |
54 | Filehandles are now stored internally as type IO::Handle. |
55 | Although C<use FileHandle> and C<*STDOUT{FILEHANDLE}> |
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56 | are still supported for backwards compatibility, |
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57 | C<use IO::Handle> (or C<IO::Seekable> or C<IO::File>) and |
58 | C<*STDOUT{IO}> are the way of the future. |
59 | |
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60 | =head2 Internal Change: PerlIO internal IO abstraction interface |
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61 | |
62 | It is now possible to build Perl with AT&T's sfio IO package |
63 | instead of stdio. See L<perlapio> for more details, and |
64 | the F<INSTALL> file for how to use it. |
65 | |
66 | =head2 New and Changed Built-in Variables |
67 | |
68 | =over |
69 | |
70 | =item $^E |
71 | |
72 | Extended error message under some platforms ($EXTENDED_OS_ERROR |
73 | if you C<use English>). |
74 | |
75 | =item $^H |
76 | |
77 | The current set of syntax checks enabled by C<use strict>. See the |
78 | documentation of C<strict> for more details. Not actually new, but |
79 | newly documented. |
80 | Because it is intended for internal use by Perl core components, |
81 | there is no C<use English> long name for this variable. |
82 | |
83 | =item $^M |
84 | |
85 | By default, running out of memory it is not trappable. However, if |
86 | compiled for this, Perl may use the contents of C<$^M> as an emergency |
87 | pool after die()ing with this message. Suppose that your Perl were |
88 | compiled with -DEMERGENCY_SBRK and used Perl's malloc. Then |
89 | |
90 | $^M = 'a' x (1<<16); |
91 | |
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92 | would allocate a 64K buffer for use when in emergency. |
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93 | See the F<INSTALL> file for information on how to enable this option. |
94 | As a disincentive to casual use of this advanced feature, |
95 | there is no C<use English> long name for this variable. |
96 | |
97 | =back |
98 | |
99 | =head2 New and Changed Built-in Functions |
100 | |
101 | =over |
102 | |
103 | =item delete on slices |
104 | |
105 | This now works. (e.g. C<delete @ENV{'PATH', 'MANPATH'}>) |
106 | |
107 | =item flock |
108 | |
109 | is now supported on more platforms, and prefers fcntl |
110 | to lockf when emulating. |
111 | |
112 | =item keys as an lvalue |
113 | |
114 | As an lvalue, C<keys> allows you to increase the number of hash buckets |
115 | allocated for the given associative array. This can gain you a measure |
116 | of efficiency if you know the hash is going to get big. (This is |
117 | similar to pre-extending an array by assigning a larger number to |
118 | $#array.) If you say |
119 | |
120 | keys %hash = 200; |
121 | |
122 | then C<%hash> will have at least 200 buckets allocated for it. These |
123 | buckets will be retained even if you do C<%hash = ()>; use C<undef |
124 | %hash> if you want to free the storage while C<%hash> is still in scope. |
125 | You can't shrink the number of buckets allocated for the hash using |
126 | C<keys> in this way (but you needn't worry about doing this by accident, |
127 | as trying has no effect). |
128 | |
129 | =item my() in Control Structures |
130 | |
131 | You can now use my() (with or without the parentheses) in the control |
132 | expressions of control structures such as: |
133 | |
134 | while (my $line = <>) { |
135 | $line = lc $line; |
136 | } continue { |
137 | print $line; |
138 | } |
139 | |
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140 | if ((my $answer = <STDIN>) =~ /^y(es)?$/i) { |
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141 | user_agrees(); |
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142 | } elsif ($answer =~ /^n(o)?$/i) { |
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143 | user_disagrees(); |
144 | } else { |
145 | chomp $answer; |
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146 | die "`$answer' is neither `yes' nor `no'"; |
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147 | } |
148 | |
149 | Also, you can declare a foreach loop control variable as lexical by |
150 | preceding it with the word "my". For example, in: |
151 | |
152 | foreach my $i (1, 2, 3) { |
153 | some_function(); |
154 | } |
155 | |
156 | $i is a lexical variable, and the scope of $i extends to the end of |
157 | the loop, but not beyond it. |
158 | |
159 | Note that you still cannot use my() on global punctuation variables |
160 | such as $_ and the like. |
161 | |
162 | =item unpack() and pack() |
163 | |
164 | A new format 'w' represents a BER compressed integer (as defined in |
165 | ASN.1). Its format is a sequence of one or more bytes, each of which |
166 | provides seven bits of the total value, with the most significant |
167 | first. Bit eight of each byte is set, except for the last byte, in |
168 | which bit eight is clear. |
169 | |
170 | =item use VERSION |
171 | |
172 | If the first argument to C<use> is a number, it is treated as a version |
173 | number instead of a module name. If the version of the Perl interpreter |
174 | is less than VERSION, then an error message is printed and Perl exits |
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175 | immediately. Because C<use> occurs at compile time, this check happens |
176 | immediately during the compilation process, unlike C<require VERSION>, |
177 | which waits until run-time for the check. This is often useful if you |
178 | need to check the current Perl version before C<use>ing library modules |
179 | which have changed in incompatible ways from older versions of Perl. |
180 | (We try not to do this more than we have to.) |
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181 | |
182 | =item use Module VERSION LIST |
183 | |
184 | If the VERSION argument is present between Module and LIST, then the |
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185 | C<use> will call the VERSION method in class Module with the given |
186 | version as an argument. The default VERSION method, inherited from |
187 | the Universal class, croaks if the given version is larger than the |
188 | value of the variable $Module::VERSION. (Note that there is not a |
189 | comma after VERSION!) |
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190 | |
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191 | This version-checking mechanism is similar to the one currently used |
192 | in the Exporter module, but it is faster and can be used with modules |
193 | that don't use the Exporter. It is the recommended method for new |
194 | code. |
195 | |
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196 | =item prototype(FUNCTION) |
197 | |
198 | Returns the prototype of a function as a string (or C<undef> if the |
199 | function has no prototype). FUNCTION is a reference to or the name of the |
200 | function whose prototype you want to retrieve. |
201 | (Not actually new; just never documented before.) |
202 | |
203 | =item $_ as Default |
204 | |
205 | Functions documented in the Camel to default to $_ now in |
206 | fact do, and all those that do are so documented in L<perlfunc>. |
207 | |
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208 | =item C<m//g> does not trigger a pos() reset on failure |
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209 | |
210 | The C<m//g> match iteration construct used to reset the iteration |
211 | when it failed to match (so that the next C<m//g> match would start at |
212 | the beginning of the string). You now have to explicitly do a |
213 | C<pos $str = 0;> to reset the "last match" position, or modify the |
214 | string in some way. This change makes it practical to chain C<m//g> |
215 | matches together in conjunction with ordinary matches using the C<\G> |
216 | zero-width assertion. See L<perlop> and L<perlre>. |
217 | |
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218 | =item nested C<sub{}> closures work now |
219 | |
220 | Prior to the 5.004 release, nested anonymous functions |
221 | didn't work right. They do now. |
222 | |
223 | =item formats work right on changing lexicals |
224 | |
225 | Just like anonymous functions that contain lexical variables |
226 | that change (like a lexical index variable for a C<foreach> loop), |
227 | formats now work properly. For example, this silently failed |
228 | before, and is fine now: |
229 | |
230 | my $i; |
231 | foreach $i ( 1 .. 10 ) { |
232 | format = |
233 | my i is @# |
234 | $i |
235 | . |
236 | write; |
237 | } |
238 | |
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239 | =back |
240 | |
241 | =head2 New Built-in Methods |
242 | |
243 | The C<UNIVERSAL> package automatically contains the following methods that |
244 | are inherited by all other classes: |
245 | |
246 | =over 4 |
247 | |
248 | =item isa(CLASS) |
249 | |
250 | C<isa> returns I<true> if its object is blessed into a sub-class of C<CLASS> |
251 | |
252 | C<isa> is also exportable and can be called as a sub with two arguments. This |
253 | allows the ability to check what a reference points to. Example: |
254 | |
255 | use UNIVERSAL qw(isa); |
256 | |
257 | if(isa($ref, 'ARRAY')) { |
258 | ... |
259 | } |
260 | |
261 | =item can(METHOD) |
262 | |
263 | C<can> checks to see if its object has a method called C<METHOD>, |
264 | if it does then a reference to the sub is returned; if it does not then |
265 | I<undef> is returned. |
266 | |
267 | =item VERSION( [NEED] ) |
268 | |
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269 | C<VERSION> returns the version number of the class (package). If the |
270 | NEED argument is given then it will check that the current version (as |
271 | defined by the $VERSION variable in the given package) not less than |
272 | NEED; it will die if this is not the case. This method is normally |
273 | called as a class method. This method is called automatically by the |
274 | C<VERSION> form of C<use>. |
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275 | |
276 | use A 1.2 qw(some imported subs); |
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277 | # implies: |
278 | A->VERSION(1.2); |
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279 | |
280 | =item class() |
281 | |
282 | C<class> returns the class name of its object. |
283 | |
284 | =item is_instance() |
285 | |
286 | C<is_instance> returns true if its object is an instance of some |
287 | class, false if its object is the class (package) itself. Example |
288 | |
289 | A->is_instance(); # False |
290 | |
291 | $var = 'A'; |
292 | $var->is_instance(); # False |
293 | |
294 | $ref = bless [], 'A'; |
295 | $ref->is_instance(); # True |
296 | |
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297 | This can be useful for methods that wish to easily distinguish |
298 | whether they were invoked as class or as instance methods. |
299 | |
300 | sub some_meth { |
301 | my $classname = shift; |
302 | if ($classname->is_instance()) { |
303 | die "unexpectedly called as instance not class method"; |
304 | } |
305 | ..... |
306 | } |
307 | |
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308 | =back |
309 | |
310 | B<NOTE:> C<can> directly uses Perl's internal code for method lookup, and |
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311 | C<isa> uses a very similar method and caching strategy. This may cause |
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312 | strange effects if the Perl code dynamically changes @ISA in any package. |
313 | |
314 | You may add other methods to the UNIVERSAL class via Perl or XS code. |
315 | You do not need to C<use UNIVERSAL> in order to make these methods |
316 | available to your program. This is necessary only if you wish to |
317 | have C<isa> available as a plain subroutine in the current package. |
318 | |
319 | =head2 TIEHANDLE Now Supported |
320 | |
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321 | See L<perltie> for other kinds of tie()s. |
322 | |
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323 | =over |
324 | |
325 | =item TIEHANDLE classname, LIST |
326 | |
327 | This is the constructor for the class. That means it is expected to |
328 | return an object of some sort. The reference can be used to |
329 | hold some internal information. |
330 | |
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331 | sub TIEHANDLE { |
332 | print "<shout>\n"; |
333 | my $i; |
334 | return bless \$i, shift; |
335 | } |
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336 | |
337 | =item PRINT this, LIST |
338 | |
339 | This method will be triggered every time the tied handle is printed to. |
340 | Beyond its self reference it also expects the list that was passed to |
341 | the print function. |
342 | |
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343 | sub PRINT { |
344 | $r = shift; |
345 | $$r++; |
346 | return print join( $, => map {uc} @_), $\; |
347 | } |
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348 | |
349 | =item READLINE this |
350 | |
351 | This method will be called when the handle is read from. The method |
352 | should return undef when there is no more data. |
353 | |
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354 | sub READLINE { |
355 | $r = shift; |
356 | return "PRINT called $$r times\n"; |
357 | } |
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358 | |
359 | =item DESTROY this |
360 | |
361 | As with the other types of ties, this method will be called when the |
362 | tied handle is about to be destroyed. This is useful for debugging and |
363 | possibly for cleaning up. |
364 | |
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365 | sub DESTROY { |
366 | print "</shout>\n"; |
367 | } |
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368 | |
369 | =back |
370 | |
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371 | =item Efficiency Enhancements |
372 | |
373 | All hash keys with the same string are only allocated once, so |
374 | even if you have 100 copies of the same hash, the immutable keys |
375 | never have to be re-allocated. |
376 | |
377 | Functions that have an empty prototype and that do nothing but return |
378 | a fixed value are now inlined (e.g. C<sub PI () { 3.14159 }>). |
379 | |
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380 | =head1 Pragmata |
381 | |
382 | Three new pragmatic modules exist: |
383 | |
384 | =over |
385 | |
386 | =item use blib |
387 | |
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388 | =item use blib 'dir' |
389 | |
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390 | Looks for MakeMaker-like I<'blib'> directory structure starting in |
391 | I<dir> (or current directory) and working back up to five levels of |
392 | parent directories. |
393 | |
394 | Intended for use on command line with B<-M> option as a way of testing |
395 | arbitrary scripts against an uninstalled version of a package. |
396 | |
397 | =item use locale |
398 | |
399 | Tells the compiler to enable (or disable) the use of POSIX locales for |
400 | built-in operations. |
401 | |
402 | When C<use locale> is in effect, the current LC_CTYPE locale is used |
403 | for regular expressions and case mapping; LC_COLLATE for string |
404 | ordering; and LC_NUMERIC for numeric formating in printf and sprintf |
405 | (but B<not> in print). LC_NUMERIC is always used in write, since |
406 | lexical scoping of formats is problematic at best. |
407 | |
408 | Each C<use locale> or C<no locale> affects statements to the end of |
409 | the enclosing BLOCK or, if not inside a BLOCK, to the end of the |
410 | current file. Locales can be switched and queried with |
411 | POSIX::setlocale(). |
412 | |
413 | See L<perllocale> for more information. |
414 | |
415 | =item use ops |
416 | |
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417 | Disable unsafe opcodes, or any named opcodes, when compiling Perl code. |
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418 | |
419 | =back |
420 | |
421 | =head1 Modules |
422 | |
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423 | =head2 Fcntl |
424 | |
425 | New constants in the existing Fcntl modules are now supported, |
426 | provided that your operating system happens to support them: |
427 | |
428 | F_GETOWN F_SETOWN |
429 | O_ASYNC O_DEFER O_DSYNC O_FSYNC O_SYNC |
430 | O_EXLOCK O_SHLOCK |
431 | |
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432 | =head2 Module Information Summary |
433 | |
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434 | Brand new modules, arranged by topic rather than strictly |
435 | alphabetically: |
436 | |
437 | CPAN interface to Comprehensive Perl Archive Network |
438 | CPAN::FirstTime create a CPAN configuration file |
439 | CPAN::Nox run CPAN while avoiding compiled extensions |
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440 | |
441 | IO.pm Top-level interface to IO::* classes |
442 | IO/File.pm IO::File extension Perl module |
443 | IO/Handle.pm IO::Handle extension Perl module |
444 | IO/Pipe.pm IO::Pipe extension Perl module |
445 | IO/Seekable.pm IO::Seekable extension Perl module |
446 | IO/Select.pm IO::Select extension Perl module |
447 | IO/Socket.pm IO::Socket extension Perl module |
448 | |
449 | Opcode.pm Disable named opcodes when compiling Perl code |
450 | |
451 | ExtUtils/Embed.pm Utilities for embedding Perl in C programs |
452 | ExtUtils/testlib.pm Fixes up @INC to use just-built extension |
453 | |
454 | Fatal.pm Make do-or-die equivalents of functions |
455 | FindBin.pm Find path of currently executing program |
456 | |
457 | Class/Template.pm Structure/member template builder |
458 | File/stat.pm Object-oriented wrapper around CORE::stat |
459 | Net/hostent.pm Object-oriented wrapper around CORE::gethost* |
460 | Net/netent.pm Object-oriented wrapper around CORE::getnet* |
461 | Net/protoent.pm Object-oriented wrapper around CORE::getproto* |
462 | Net/servent.pm Object-oriented wrapper around CORE::getserv* |
463 | Time/gmtime.pm Object-oriented wrapper around CORE::gmtime |
464 | Time/localtime.pm Object-oriented wrapper around CORE::localtime |
465 | Time/tm.pm Perl implementation of "struct tm" for {gm,local}time |
466 | User/grent.pm Object-oriented wrapper around CORE::getgr* |
467 | User/pwent.pm Object-oriented wrapper around CORE::getpw* |
468 | |
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469 | Tie/RefHash.pm Base class for tied hashes with references as keys |
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470 | |
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471 | UNIVERSAL.pm Base class for *ALL* classes |
472 | |
473 | =head2 IO |
474 | |
475 | The IO module provides a simple mechanism to load all of the IO modules at one |
476 | go. Currently this includes: |
477 | |
478 | IO::Handle |
479 | IO::Seekable |
480 | IO::File |
481 | IO::Pipe |
482 | IO::Socket |
483 | |
484 | For more information on any of these modules, please see its |
485 | respective documentation. |
486 | |
487 | =head2 Math::Complex |
488 | |
489 | The Math::Complex module has been totally rewritten, and now supports |
490 | more operations. These are overloaded: |
491 | |
492 | + - * / ** <=> neg ~ abs sqrt exp log sin cos atan2 "" (stringify) |
493 | |
494 | And these functions are now exported: |
495 | |
496 | pi i Re Im arg |
497 | log10 logn cbrt root |
498 | tan cotan asin acos atan acotan |
499 | sinh cosh tanh cotanh asinh acosh atanh acotanh |
500 | cplx cplxe |
501 | |
502 | =head2 Overridden Built-ins |
503 | |
504 | Many of the Perl built-ins returning lists now have |
505 | object-oriented overrides. These are: |
506 | |
507 | File::stat |
508 | Net::hostent |
509 | Net::netent |
510 | Net::protoent |
511 | Net::servent |
512 | Time::gmtime |
513 | Time::localtime |
514 | User::grent |
515 | User::pwent |
516 | |
517 | For example, you can now say |
518 | |
519 | use File::stat; |
520 | use User::pwent; |
521 | $his = (stat($filename)->st_uid == pwent($whoever)->pw_uid); |
522 | |
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523 | =head1 Utility Changes |
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524 | |
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525 | =head2 xsubpp |
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526 | |
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527 | =item C<void> XSUBs now default to returning nothing |
528 | |
529 | Due to a documentation/implementation bug in previous versions of |
530 | Perl, XSUBs with a return type of C<void> have actually been |
531 | returning one value. Usually that value was the GV for the XSUB, |
532 | but sometimes it was some already freed or reused value, which would |
533 | sometimes lead to program failure. |
534 | |
535 | In Perl 5.004, if an XSUB is declared as returning C<void>, it |
536 | actually returns no value, i.e. an empty list (though there is a |
537 | backward-compatibility exception; see below). If your XSUB really |
538 | does return an SV, you should give it a return type of C<SV *>. |
539 | |
540 | For backward compatibility, I<xsubpp> tries to guess whether a |
541 | C<void> XSUB is really C<void> or if it wants to return an C<SV *>. |
542 | It does so by examining the text of the XSUB: if I<xsubpp> finds |
543 | what looks like an assignment to C<ST(0)>, it assumes that the |
544 | XSUB's return type is really C<SV *>. |
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545 | |
546 | =head1 Documentation Changes |
547 | |
548 | Many of the base and library pods were updated. These |
549 | new pods are included in section 1: |
550 | |
551 | =over 4 |
552 | |
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553 | =item L<perldelta> |
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554 | |
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555 | This document. |
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556 | |
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557 | =item L<perllocale> |
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558 | |
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559 | Locale support (internationalization and localization). |
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560 | |
561 | =item L<perltoot> |
562 | |
563 | Tutorial on Perl OO programming. |
564 | |
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565 | =item L<perlapio> |
566 | |
567 | Perl internal IO abstraction interface. |
568 | |
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569 | =item L<perldebug> |
570 | |
571 | Although not new, this has been massively updated. |
572 | |
573 | =item L<perlsec> |
574 | |
575 | Although not new, this has been massively updated. |
576 | |
577 | =back |
578 | |
579 | =head1 New Diagnostics |
580 | |
581 | Several new conditions will trigger warnings that were |
582 | silent before. Some only affect certain platforms. |
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583 | The following new warnings and errors outline these. |
584 | These messages are classified as follows (listed in |
585 | increasing order of desperation): |
586 | |
587 | (W) A warning (optional). |
588 | (D) A deprecation (optional). |
589 | (S) A severe warning (mandatory). |
590 | (F) A fatal error (trappable). |
591 | (P) An internal error you should never see (trappable). |
592 | (X) A very fatal error (non-trappable). |
593 | (A) An alien error message (not generated by Perl). |
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594 | |
595 | =over 4 |
596 | |
597 | =item "my" variable %s masks earlier declaration in same scope |
598 | |
599 | (S) A lexical variable has been redeclared in the same scope, effectively |
600 | eliminating all access to the previous instance. This is almost always |
601 | a typographical error. Note that the earlier variable will still exist |
602 | until the end of the scope or until all closure referents to it are |
603 | destroyed. |
604 | |
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605 | =item %s argument is not a HASH element or slice |
606 | |
607 | (F) The argument to delete() must be either a hash element, such as |
608 | |
609 | $foo{$bar} |
610 | $ref->[12]->{"susie"} |
611 | |
612 | or a hash slice, such as |
613 | |
614 | @foo{$bar, $baz, $xyzzy} |
615 | @{$ref->[12]}{"susie", "queue"} |
616 | |
5f05dabc |
617 | =item Allocation too large: %lx |
618 | |
619 | (X) You can't allocate more than 64K on an MSDOS machine. |
620 | |
621 | =item Allocation too large |
622 | |
623 | (F) You can't allocate more than 2^31+"small amount" bytes. |
624 | |
625 | =item Attempt to free non-existent shared string |
626 | |
627 | (P) Perl maintains a reference counted internal table of strings to |
628 | optimize the storage and access of hash keys and other strings. This |
629 | indicates someone tried to decrement the reference count of a string |
630 | that can no longer be found in the table. |
631 | |
632 | =item Attempt to use reference as lvalue in substr |
633 | |
634 | (W) You supplied a reference as the first argument to substr() used |
635 | as an lvalue, which is pretty strange. Perhaps you forgot to |
636 | dereference it first. See L<perlfunc/substr>. |
637 | |
638 | =item Unsupported function fork |
639 | |
640 | (F) Your version of executable does not support forking. |
641 | |
642 | Note that under some systems, like OS/2, there may be different flavors of |
643 | Perl executables, some of which may support fork, some not. Try changing |
644 | the name you call Perl by to C<perl_>, C<perl__>, and so on. |
645 | |
646 | =item Ill-formed logical name |%s| in prime_env_iter |
647 | |
648 | (W) A warning peculiar to VMS. A logical name was encountered when preparing |
649 | to iterate over %ENV which violates the syntactic rules governing logical |
650 | names. Since it cannot be translated normally, it is skipped, and will not |
651 | appear in %ENV. This may be a benign occurrence, as some software packages |
652 | might directly modify logical name tables and introduce non-standard names, |
653 | or it may indicate that a logical name table has been corrupted. |
654 | |
774d564b |
655 | =item Can't use bareword ("%s") as %s ref while "strict refs" in use |
656 | |
657 | (F) Only hard references are allowed by "strict refs". Symbolic references |
658 | are disallowed. See L<perlref>. |
659 | |
660 | =item Constant subroutine %s redefined |
661 | |
662 | (S) You redefined a subroutine which had previously been eligible for |
663 | inlining. See L<perlsub/"Constant Functions"> for commentary and |
664 | workarounds. |
665 | |
666 | =item Died |
667 | |
668 | (F) You passed die() an empty string (the equivalent of C<die "">) or |
669 | you called it with no args and both C<$@> and C<$_> were empty. |
670 | |
5f05dabc |
671 | =item Integer overflow in hex number |
672 | |
673 | (S) The literal hex number you have specified is too big for your |
674 | architecture. On a 32-bit architecture the largest hex literal is |
675 | 0xFFFFFFFF. |
676 | |
677 | =item Integer overflow in octal number |
678 | |
679 | (S) The literal octal number you have specified is too big for your |
680 | architecture. On a 32-bit architecture the largest octal literal is |
681 | 037777777777. |
682 | |
774d564b |
683 | =item Name "%s::%s" used only once: possible typo |
684 | |
685 | (W) Typographical errors often show up as unique variable names. |
686 | If you had a good reason for having a unique name, then just mention |
687 | it again somehow to suppress the message (the C<use vars> pragma is |
688 | provided for just this purpose). |
689 | |
5f05dabc |
690 | =item Null picture in formline |
691 | |
692 | (F) The first argument to formline must be a valid format picture |
693 | specification. It was found to be empty, which probably means you |
694 | supplied it an uninitialized value. See L<perlform>. |
695 | |
696 | =item Offset outside string |
697 | |
698 | (F) You tried to do a read/write/send/recv operation with an offset |
699 | pointing outside the buffer. This is difficult to imagine. |
700 | The sole exception to this is that C<sysread()>ing past the buffer |
701 | will extend the buffer and zero pad the new area. |
702 | |
774d564b |
703 | =item Stub found while resolving method `%s' overloading `%s' in package `%s' |
704 | |
705 | (P) Overloading resolution over @ISA tree may be broken by importing stubs. |
706 | Stubs should never be implicitely created, but explicit calls to C<can> |
707 | may break this. |
708 | |
709 | =item Cannot resolve method `%s' overloading `%s' in package `s' |
710 | |
711 | (P) Internal error trying to resolve overloading specified by a method |
712 | name (as opposed to a subroutine reference). |
713 | |
5f05dabc |
714 | =item Out of memory! |
715 | |
716 | (X|F) The malloc() function returned 0, indicating there was insufficient |
717 | remaining memory (or virtual memory) to satisfy the request. |
718 | |
719 | The request was judged to be small, so the possibility to trap it |
720 | depends on the way Perl was compiled. By default it is not trappable. |
721 | However, if compiled for this, Perl may use the contents of C<$^M> as |
722 | an emergency pool after die()ing with this message. In this case the |
723 | error is trappable I<once>. |
724 | |
725 | =item Out of memory during request for %s |
726 | |
727 | (F) The malloc() function returned 0, indicating there was insufficient |
728 | remaining memory (or virtual memory) to satisfy the request. However, |
729 | the request was judged large enough (compile-time default is 64K), so |
730 | a possibility to shut down by trapping this error is granted. |
731 | |
732 | =item Possible attempt to put comments in qw() list |
733 | |
774d564b |
734 | (W) qw() lists contain items separated by whitespace; as with literal |
735 | strings, comment characters are not ignored, but are instead treated |
736 | as literal data. (You may have used different delimiters than the |
737 | exclamation marks parentheses shown here; braces are also frequently |
738 | used.) |
739 | |
740 | You probably wrote something like this: |
5f05dabc |
741 | |
774d564b |
742 | @list = qw( |
743 | a # a comment |
5f05dabc |
744 | b # another comment |
774d564b |
745 | ); |
5f05dabc |
746 | |
747 | when you should have written this: |
748 | |
774d564b |
749 | @list = qw( |
750 | a |
5f05dabc |
751 | b |
774d564b |
752 | ); |
753 | |
754 | If you really want comments, build your list the |
755 | old-fashioned way, with quotes and commas: |
756 | |
757 | @list = ( |
758 | 'a', # a comment |
759 | 'b', # another comment |
760 | ); |
5f05dabc |
761 | |
762 | =item Possible attempt to separate words with commas |
763 | |
774d564b |
764 | (W) qw() lists contain items separated by whitespace; therefore commas |
765 | aren't needed to separate the items. (You may have used different |
766 | delimiters than the parentheses shown here; braces are also frequently |
767 | used.) |
5f05dabc |
768 | |
774d564b |
769 | You probably wrote something like this: |
5f05dabc |
770 | |
774d564b |
771 | qw! a, b, c !; |
772 | |
773 | which puts literal commas into some of the list items. Write it without |
774 | commas if you don't want them to appear in your data: |
775 | |
776 | qw! a b c !; |
5f05dabc |
777 | |
774d564b |
778 | =item Scalar value @%s{%s} better written as $%s{%s} |
779 | |
780 | (W) You've used a hash slice (indicated by @) to select a single element of |
781 | a hash. Generally it's better to ask for a scalar value (indicated by $). |
782 | The difference is that C<$foo{&bar}> always behaves like a scalar, both when |
783 | assigning to it and when evaluating its argument, while C<@foo{&bar}> behaves |
784 | like a list when you assign to it, and provides a list context to its |
785 | subscript, which can do weird things if you're expecting only one subscript. |
5f05dabc |
786 | |
787 | =item untie attempted while %d inner references still exist |
788 | |
789 | (W) A copy of the object returned from C<tie> (or C<tied>) was still |
790 | valid when C<untie> was called. |
791 | |
774d564b |
792 | =item Value of %s construct can be "0"; test with defined() |
793 | |
794 | (W) In a conditional expression, you used <HANDLE>, <*> (glob), or |
795 | C<readdir> as a boolean value. Each of these constructs can return a |
796 | value of "0"; that would make the conditional expression false, which |
797 | is probably not what you intended. When using these constructs in |
798 | conditional expressions, test their values with the C<defined> operator. |
799 | |
800 | =item Variable "%s" may be unavailable |
801 | |
802 | (W) An inner (nested) I<anonymous> subroutine is inside a I<named> |
803 | subroutine, and outside that is another subroutine; and the anonymous |
804 | (innermost) subroutine is referencing a lexical variable defined in |
805 | the outermost subroutine. For example: |
806 | |
807 | sub outermost { my $a; sub middle { sub { $a } } } |
808 | |
809 | If the anonymous subroutine is called or referenced (directly or |
810 | indirectly) from the outermost subroutine, it will share the variable |
811 | as you would expect. But if the anonymous subroutine is called or |
812 | referenced when the outermost subroutine is not active, it will see |
813 | the value of the shared variable as it was before and during the |
814 | *first* call to the outermost subroutine, which is probably not what |
815 | you want. |
816 | |
817 | In these circumstances, it is usually best to make the middle |
818 | subroutine anonymous, using the C<sub {}> syntax. Perl has specific |
819 | support for shared variables in nested anonymous subroutines; a named |
820 | subroutine in between interferes with this feature. |
821 | |
822 | =item Variable "%s" will not stay shared |
823 | |
824 | (W) An inner (nested) I<named> subroutine is referencing a lexical |
825 | variable defined in an outer subroutine. |
826 | |
827 | When the inner subroutine is called, it will probably see the value of |
828 | the outer subroutine's variable as it was before and during the |
829 | *first* call to the outer subroutine; in this case, after the first |
830 | call to the outer subroutine is complete, the inner and outer |
831 | subroutines will no longer share a common value for the variable. In |
832 | other words, the variable will no longer be shared. |
833 | |
834 | Furthermore, if the outer subroutine is anonymous and references a |
835 | lexical variable outside itself, then the outer and inner subroutines |
836 | will I<never> share the given variable. |
837 | |
838 | This problem can usually be solved by making the inner subroutine |
839 | anonymous, using the C<sub {}> syntax. When inner anonymous subs that |
840 | reference variables in outer subroutines are called or referenced, |
841 | they are automatically re-bound to the current values of such |
842 | variables. |
843 | |
844 | =item Warning: something's wrong |
845 | |
846 | (W) You passed warn() an empty string (the equivalent of C<warn "">) or |
847 | you called it with no args and C<$_> was empty. |
848 | |
849 | =item Got an error from DosAllocMem |
5f05dabc |
850 | |
774d564b |
851 | (P) An error peculiar to OS/2. Most probably you're using an obsolete |
852 | version of Perl, and this should not happen anyway. |
5f05dabc |
853 | |
854 | =item Malformed PERLLIB_PREFIX |
855 | |
856 | (F) An error peculiar to OS/2. PERLLIB_PREFIX should be of the form |
857 | |
858 | prefix1;prefix2 |
859 | |
860 | or |
861 | |
862 | prefix1 prefix2 |
863 | |
864 | with non-empty prefix1 and prefix2. If C<prefix1> is indeed a prefix of |
865 | a builtin library search path, prefix2 is substituted. The error may appear |
866 | if components are not found, or are too long. See L<perlos2/"PERLLIB_PREFIX">. |
867 | |
868 | =item PERL_SH_DIR too long |
869 | |
870 | (F) An error peculiar to OS/2. PERL_SH_DIR is the directory to find the |
871 | C<sh>-shell in. See L<perlos2/"PERL_SH_DIR">. |
872 | |
873 | =item Process terminated by SIG%s |
874 | |
875 | (W) This is a standard message issued by OS/2 applications, while *nix |
876 | applications die in silence. It is considered a feature of the OS/2 |
877 | port. One can easily disable this by appropriate sighandlers, see |
878 | L<perlipc/"Signals">. See L<perlos2/"Process terminated by SIGTERM/SIGINT">. |
879 | |
880 | =back |
881 | |
882 | =head1 BUGS |
883 | |
774d564b |
884 | If you find what you think is a bug, you might check the headers of |
885 | recently posted articles in the comp.lang.perl.misc newsgroup. |
886 | There may also be information at http://www.perl.com/perl/, the Perl |
887 | Home Page. |
5f05dabc |
888 | |
889 | If you believe you have an unreported bug, please run the B<perlbug> |
890 | program included with your release. Make sure you trim your bug |
891 | down to a tiny but sufficient test case. Your bug report, along |
892 | with the output of C<perl -V>, will be sent off to perlbug@perl.com |
893 | to be analysed by the Perl porting team. |
894 | |
895 | =head1 SEE ALSO |
896 | |
897 | The F<Changes> file for exhaustive details on what changed. |
898 | |
899 | The F<INSTALL> file for how to build Perl. This file has been |
900 | significantly updated for 5.004, so even veteran users should |
901 | look through it. |
902 | |
903 | The F<README> file for general stuff. |
904 | |
905 | The F<Copying> file for copyright information. |
906 | |
907 | =head1 HISTORY |
908 | |
909 | Constructed by Tom Christiansen, grabbing material with permission |
910 | from innumerable contributors, with kibitzing by more than a few Perl |
911 | porters. |
912 | |
44a8e56a |
913 | Last update: Tue Jan 14 14:03:02 EST 1997 |