Commit | Line | Data |
5f05dabc |
1 | =head1 NAME |
2 | |
774d564b |
3 | perldelta - what's new for perl5.004 |
5f05dabc |
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 |
44a8e56a |
26 | might have symbol conflicts if you embed Perl in another application, |
774d564b |
27 | just as in the 5.003 release. By default, binary compatibility |
28 | is preserved at the expense of symbol table pollution. |
5f05dabc |
29 | |
7cfe7857 |
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 | |
5f05dabc |
37 | =head2 Internal Change: FileHandle Deprecated |
38 | |
39 | Filehandles are now stored internally as type IO::Handle. |
40 | Although C<use FileHandle> and C<*STDOUT{FILEHANDLE}> |
774d564b |
41 | are still supported for backwards compatibility, |
5f05dabc |
42 | C<use IO::Handle> (or C<IO::Seekable> or C<IO::File>) and |
43 | C<*STDOUT{IO}> are the way of the future. |
44 | |
28757baa |
45 | =head2 Internal Change: PerlIO internal IO abstraction interface |
5f05dabc |
46 | |
47 | It is now possible to build Perl with AT&T's sfio IO package |
48 | instead of stdio. See L<perlapio> for more details, and |
49 | the F<INSTALL> file for how to use it. |
50 | |
51 | =head2 New and Changed Built-in Variables |
52 | |
53 | =over |
54 | |
55 | =item $^E |
56 | |
f86702cc |
57 | Extended error message on some platforms. (Also known as |
58 | $EXTENDED_OS_ERROR if you C<use English>). |
5f05dabc |
59 | |
60 | =item $^H |
61 | |
62 | The current set of syntax checks enabled by C<use strict>. See the |
63 | documentation of C<strict> for more details. Not actually new, but |
64 | newly documented. |
65 | Because it is intended for internal use by Perl core components, |
66 | there is no C<use English> long name for this variable. |
67 | |
68 | =item $^M |
69 | |
70 | By default, running out of memory it is not trappable. However, if |
71 | compiled for this, Perl may use the contents of C<$^M> as an emergency |
72 | pool after die()ing with this message. Suppose that your Perl were |
73 | compiled with -DEMERGENCY_SBRK and used Perl's malloc. Then |
74 | |
75 | $^M = 'a' x (1<<16); |
76 | |
774d564b |
77 | would allocate a 64K buffer for use when in emergency. |
5f05dabc |
78 | See the F<INSTALL> file for information on how to enable this option. |
79 | As a disincentive to casual use of this advanced feature, |
80 | there is no C<use English> long name for this variable. |
81 | |
82 | =back |
83 | |
84 | =head2 New and Changed Built-in Functions |
85 | |
86 | =over |
87 | |
88 | =item delete on slices |
89 | |
90 | This now works. (e.g. C<delete @ENV{'PATH', 'MANPATH'}>) |
91 | |
92 | =item flock |
93 | |
94 | is now supported on more platforms, and prefers fcntl |
95 | to lockf when emulating. |
96 | |
046ff0ed |
97 | =item printf and sprintf |
98 | |
99 | now support "%i" as a synonym for "%d", and the "h" modifier. |
100 | So "%hi" means "short integer in decimal", and "%ho" means |
101 | "unsigned short integer as octal". |
102 | |
5f05dabc |
103 | =item keys as an lvalue |
104 | |
105 | As an lvalue, C<keys> allows you to increase the number of hash buckets |
106 | allocated for the given associative array. This can gain you a measure |
107 | of efficiency if you know the hash is going to get big. (This is |
108 | similar to pre-extending an array by assigning a larger number to |
109 | $#array.) If you say |
110 | |
111 | keys %hash = 200; |
112 | |
113 | then C<%hash> will have at least 200 buckets allocated for it. These |
114 | buckets will be retained even if you do C<%hash = ()>; use C<undef |
115 | %hash> if you want to free the storage while C<%hash> is still in scope. |
116 | You can't shrink the number of buckets allocated for the hash using |
117 | C<keys> in this way (but you needn't worry about doing this by accident, |
118 | as trying has no effect). |
119 | |
120 | =item my() in Control Structures |
121 | |
122 | You can now use my() (with or without the parentheses) in the control |
123 | expressions of control structures such as: |
124 | |
125 | while (my $line = <>) { |
126 | $line = lc $line; |
127 | } continue { |
128 | print $line; |
129 | } |
130 | |
774d564b |
131 | if ((my $answer = <STDIN>) =~ /^y(es)?$/i) { |
5f05dabc |
132 | user_agrees(); |
774d564b |
133 | } elsif ($answer =~ /^n(o)?$/i) { |
5f05dabc |
134 | user_disagrees(); |
135 | } else { |
136 | chomp $answer; |
774d564b |
137 | die "`$answer' is neither `yes' nor `no'"; |
5f05dabc |
138 | } |
139 | |
140 | Also, you can declare a foreach loop control variable as lexical by |
141 | preceding it with the word "my". For example, in: |
142 | |
143 | foreach my $i (1, 2, 3) { |
144 | some_function(); |
145 | } |
146 | |
147 | $i is a lexical variable, and the scope of $i extends to the end of |
148 | the loop, but not beyond it. |
149 | |
150 | Note that you still cannot use my() on global punctuation variables |
151 | such as $_ and the like. |
152 | |
153 | =item unpack() and pack() |
154 | |
155 | A new format 'w' represents a BER compressed integer (as defined in |
156 | ASN.1). Its format is a sequence of one or more bytes, each of which |
157 | provides seven bits of the total value, with the most significant |
158 | first. Bit eight of each byte is set, except for the last byte, in |
159 | which bit eight is clear. |
160 | |
161 | =item use VERSION |
162 | |
163 | If the first argument to C<use> is a number, it is treated as a version |
164 | number instead of a module name. If the version of the Perl interpreter |
165 | is less than VERSION, then an error message is printed and Perl exits |
774d564b |
166 | immediately. Because C<use> occurs at compile time, this check happens |
167 | immediately during the compilation process, unlike C<require VERSION>, |
168 | which waits until run-time for the check. This is often useful if you |
169 | need to check the current Perl version before C<use>ing library modules |
170 | which have changed in incompatible ways from older versions of Perl. |
171 | (We try not to do this more than we have to.) |
5f05dabc |
172 | |
173 | =item use Module VERSION LIST |
174 | |
175 | If the VERSION argument is present between Module and LIST, then the |
71be2cbc |
176 | C<use> will call the VERSION method in class Module with the given |
177 | version as an argument. The default VERSION method, inherited from |
178 | the Universal class, croaks if the given version is larger than the |
179 | value of the variable $Module::VERSION. (Note that there is not a |
180 | comma after VERSION!) |
5f05dabc |
181 | |
7cfe7857 |
182 | This version-checking mechanism is similar to the one currently used |
183 | in the Exporter module, but it is faster and can be used with modules |
184 | that don't use the Exporter. It is the recommended method for new |
185 | code. |
186 | |
5f05dabc |
187 | =item prototype(FUNCTION) |
188 | |
189 | Returns the prototype of a function as a string (or C<undef> if the |
190 | function has no prototype). FUNCTION is a reference to or the name of the |
191 | function whose prototype you want to retrieve. |
192 | (Not actually new; just never documented before.) |
193 | |
194 | =item $_ as Default |
195 | |
196 | Functions documented in the Camel to default to $_ now in |
197 | fact do, and all those that do are so documented in L<perlfunc>. |
198 | |
774d564b |
199 | =item C<m//g> does not trigger a pos() reset on failure |
44a8e56a |
200 | |
201 | The C<m//g> match iteration construct used to reset the iteration |
202 | when it failed to match (so that the next C<m//g> match would start at |
203 | the beginning of the string). You now have to explicitly do a |
204 | C<pos $str = 0;> to reset the "last match" position, or modify the |
205 | string in some way. This change makes it practical to chain C<m//g> |
206 | matches together in conjunction with ordinary matches using the C<\G> |
207 | zero-width assertion. See L<perlop> and L<perlre>. |
208 | |
774d564b |
209 | =item nested C<sub{}> closures work now |
210 | |
211 | Prior to the 5.004 release, nested anonymous functions |
212 | didn't work right. They do now. |
213 | |
214 | =item formats work right on changing lexicals |
215 | |
216 | Just like anonymous functions that contain lexical variables |
217 | that change (like a lexical index variable for a C<foreach> loop), |
218 | formats now work properly. For example, this silently failed |
219 | before, and is fine now: |
220 | |
221 | my $i; |
222 | foreach $i ( 1 .. 10 ) { |
223 | format = |
224 | my i is @# |
225 | $i |
226 | . |
227 | write; |
228 | } |
229 | |
5f05dabc |
230 | =back |
231 | |
232 | =head2 New Built-in Methods |
233 | |
234 | The C<UNIVERSAL> package automatically contains the following methods that |
235 | are inherited by all other classes: |
236 | |
0a753a76 |
237 | =over |
5f05dabc |
238 | |
239 | =item isa(CLASS) |
240 | |
241 | C<isa> returns I<true> if its object is blessed into a sub-class of C<CLASS> |
242 | |
243 | C<isa> is also exportable and can be called as a sub with two arguments. This |
244 | allows the ability to check what a reference points to. Example: |
245 | |
246 | use UNIVERSAL qw(isa); |
247 | |
248 | if(isa($ref, 'ARRAY')) { |
249 | ... |
250 | } |
251 | |
252 | =item can(METHOD) |
253 | |
254 | C<can> checks to see if its object has a method called C<METHOD>, |
255 | if it does then a reference to the sub is returned; if it does not then |
256 | I<undef> is returned. |
257 | |
258 | =item VERSION( [NEED] ) |
259 | |
71be2cbc |
260 | C<VERSION> returns the version number of the class (package). If the |
261 | NEED argument is given then it will check that the current version (as |
262 | defined by the $VERSION variable in the given package) not less than |
263 | NEED; it will die if this is not the case. This method is normally |
264 | called as a class method. This method is called automatically by the |
265 | C<VERSION> form of C<use>. |
5f05dabc |
266 | |
267 | use A 1.2 qw(some imported subs); |
71be2cbc |
268 | # implies: |
269 | A->VERSION(1.2); |
5f05dabc |
270 | |
5f05dabc |
271 | =back |
272 | |
273 | B<NOTE:> C<can> directly uses Perl's internal code for method lookup, and |
774d564b |
274 | C<isa> uses a very similar method and caching strategy. This may cause |
5f05dabc |
275 | strange effects if the Perl code dynamically changes @ISA in any package. |
276 | |
277 | You may add other methods to the UNIVERSAL class via Perl or XS code. |
278 | You do not need to C<use UNIVERSAL> in order to make these methods |
279 | available to your program. This is necessary only if you wish to |
280 | have C<isa> available as a plain subroutine in the current package. |
281 | |
282 | =head2 TIEHANDLE Now Supported |
283 | |
774d564b |
284 | See L<perltie> for other kinds of tie()s. |
285 | |
5f05dabc |
286 | =over |
287 | |
288 | =item TIEHANDLE classname, LIST |
289 | |
290 | This is the constructor for the class. That means it is expected to |
291 | return an object of some sort. The reference can be used to |
292 | hold some internal information. |
293 | |
774d564b |
294 | sub TIEHANDLE { |
295 | print "<shout>\n"; |
296 | my $i; |
297 | return bless \$i, shift; |
298 | } |
5f05dabc |
299 | |
300 | =item PRINT this, LIST |
301 | |
302 | This method will be triggered every time the tied handle is printed to. |
303 | Beyond its self reference it also expects the list that was passed to |
304 | the print function. |
305 | |
774d564b |
306 | sub PRINT { |
307 | $r = shift; |
308 | $$r++; |
309 | return print join( $, => map {uc} @_), $\; |
310 | } |
5f05dabc |
311 | |
312 | =item READLINE this |
313 | |
314 | This method will be called when the handle is read from. The method |
315 | should return undef when there is no more data. |
316 | |
774d564b |
317 | sub READLINE { |
318 | $r = shift; |
319 | return "PRINT called $$r times\n"; |
320 | } |
5f05dabc |
321 | |
322 | =item DESTROY this |
323 | |
324 | As with the other types of ties, this method will be called when the |
325 | tied handle is about to be destroyed. This is useful for debugging and |
326 | possibly for cleaning up. |
327 | |
774d564b |
328 | sub DESTROY { |
329 | print "</shout>\n"; |
330 | } |
5f05dabc |
331 | |
332 | =back |
333 | |
774d564b |
334 | =item Efficiency Enhancements |
335 | |
336 | All hash keys with the same string are only allocated once, so |
337 | even if you have 100 copies of the same hash, the immutable keys |
338 | never have to be re-allocated. |
339 | |
340 | Functions that have an empty prototype and that do nothing but return |
341 | a fixed value are now inlined (e.g. C<sub PI () { 3.14159 }>). |
342 | |
5f05dabc |
343 | =head1 Pragmata |
344 | |
ff0cee69 |
345 | Four new pragmatic modules exist: |
5f05dabc |
346 | |
347 | =over |
348 | |
349 | =item use blib |
350 | |
774d564b |
351 | =item use blib 'dir' |
352 | |
5f05dabc |
353 | Looks for MakeMaker-like I<'blib'> directory structure starting in |
354 | I<dir> (or current directory) and working back up to five levels of |
355 | parent directories. |
356 | |
357 | Intended for use on command line with B<-M> option as a way of testing |
358 | arbitrary scripts against an uninstalled version of a package. |
359 | |
360 | =item use locale |
361 | |
362 | Tells the compiler to enable (or disable) the use of POSIX locales for |
363 | built-in operations. |
364 | |
365 | When C<use locale> is in effect, the current LC_CTYPE locale is used |
366 | for regular expressions and case mapping; LC_COLLATE for string |
367 | ordering; and LC_NUMERIC for numeric formating in printf and sprintf |
368 | (but B<not> in print). LC_NUMERIC is always used in write, since |
369 | lexical scoping of formats is problematic at best. |
370 | |
371 | Each C<use locale> or C<no locale> affects statements to the end of |
372 | the enclosing BLOCK or, if not inside a BLOCK, to the end of the |
373 | current file. Locales can be switched and queried with |
374 | POSIX::setlocale(). |
375 | |
376 | See L<perllocale> for more information. |
377 | |
378 | =item use ops |
379 | |
7cfe7857 |
380 | Disable unsafe opcodes, or any named opcodes, when compiling Perl code. |
5f05dabc |
381 | |
ff0cee69 |
382 | =item use vmsish |
383 | |
384 | Enable VMS-specific language features. Currently, there are three |
385 | VMS-specific feature available: 'status', which makes C<$?> and |
386 | C<system> return genuine VMS status values instead of emulating POSIX; |
387 | 'exit', which makes C<exit> take a genuine VMS status value instead of |
388 | assuming that C<exit 1> is an error; and 'time', which makes all times |
389 | relative to the local time zone, in the VMS tradition. |
390 | |
5f05dabc |
391 | =back |
392 | |
393 | =head1 Modules |
394 | |
f86702cc |
395 | =head2 Installation Directories |
396 | |
397 | The I<installperl> script now places the Perl source files for |
398 | extensions in the architecture-specific library directory, which is |
399 | where the shared libraries for extensions have always been. This |
400 | change is intended to allow administrators to keep the Perl 5.004 |
401 | library directory unchanged from a previous version, without running |
402 | the risk of binary incompatibility between extensions' Perl source and |
403 | shared libraries. |
404 | |
774d564b |
405 | =head2 Fcntl |
406 | |
407 | New constants in the existing Fcntl modules are now supported, |
408 | provided that your operating system happens to support them: |
409 | |
410 | F_GETOWN F_SETOWN |
411 | O_ASYNC O_DEFER O_DSYNC O_FSYNC O_SYNC |
412 | O_EXLOCK O_SHLOCK |
413 | |
0a753a76 |
414 | These constants are intended for use with the Perl operators sysopen() |
415 | and fcntl() and the basic database modules like SDBM_File. For the |
416 | exact meaning of these and other Fcntl constants please refer to your |
417 | operating system's documentation for fcntl() and open(). |
418 | |
419 | In addition, the Fcntl module now provides these constants for use |
420 | with the Perl operator flock(): |
421 | |
422 | LOCK_SH LOCK_EX LOCK_NB LOCK_UN |
423 | |
424 | These constants are defined in all environments (because where there is |
425 | no flock() system call, Perl emulates it). However, for historical |
426 | reasons, these constants are not exported unless they are explicitly |
427 | requested with the ":flock" tag (e.g. C<use Fcntl ':flock'>). |
428 | |
5f05dabc |
429 | =head2 Module Information Summary |
430 | |
774d564b |
431 | Brand new modules, arranged by topic rather than strictly |
432 | alphabetically: |
433 | |
434 | CPAN interface to Comprehensive Perl Archive Network |
435 | CPAN::FirstTime create a CPAN configuration file |
436 | CPAN::Nox run CPAN while avoiding compiled extensions |
5f05dabc |
437 | |
438 | IO.pm Top-level interface to IO::* classes |
439 | IO/File.pm IO::File extension Perl module |
440 | IO/Handle.pm IO::Handle extension Perl module |
441 | IO/Pipe.pm IO::Pipe extension Perl module |
442 | IO/Seekable.pm IO::Seekable extension Perl module |
443 | IO/Select.pm IO::Select extension Perl module |
444 | IO/Socket.pm IO::Socket extension Perl module |
445 | |
446 | Opcode.pm Disable named opcodes when compiling Perl code |
447 | |
448 | ExtUtils/Embed.pm Utilities for embedding Perl in C programs |
449 | ExtUtils/testlib.pm Fixes up @INC to use just-built extension |
450 | |
5f05dabc |
451 | FindBin.pm Find path of currently executing program |
452 | |
453 | Class/Template.pm Structure/member template builder |
454 | File/stat.pm Object-oriented wrapper around CORE::stat |
455 | Net/hostent.pm Object-oriented wrapper around CORE::gethost* |
456 | Net/netent.pm Object-oriented wrapper around CORE::getnet* |
457 | Net/protoent.pm Object-oriented wrapper around CORE::getproto* |
458 | Net/servent.pm Object-oriented wrapper around CORE::getserv* |
459 | Time/gmtime.pm Object-oriented wrapper around CORE::gmtime |
460 | Time/localtime.pm Object-oriented wrapper around CORE::localtime |
461 | Time/tm.pm Perl implementation of "struct tm" for {gm,local}time |
462 | User/grent.pm Object-oriented wrapper around CORE::getgr* |
463 | User/pwent.pm Object-oriented wrapper around CORE::getpw* |
464 | |
774d564b |
465 | Tie/RefHash.pm Base class for tied hashes with references as keys |
7a4c00b4 |
466 | |
5f05dabc |
467 | UNIVERSAL.pm Base class for *ALL* classes |
468 | |
469 | =head2 IO |
470 | |
471 | The IO module provides a simple mechanism to load all of the IO modules at one |
472 | go. Currently this includes: |
473 | |
474 | IO::Handle |
475 | IO::Seekable |
476 | IO::File |
477 | IO::Pipe |
478 | IO::Socket |
479 | |
480 | For more information on any of these modules, please see its |
481 | respective documentation. |
482 | |
483 | =head2 Math::Complex |
484 | |
485 | The Math::Complex module has been totally rewritten, and now supports |
486 | more operations. These are overloaded: |
487 | |
488 | + - * / ** <=> neg ~ abs sqrt exp log sin cos atan2 "" (stringify) |
489 | |
490 | And these functions are now exported: |
491 | |
492 | pi i Re Im arg |
493 | log10 logn cbrt root |
494 | tan cotan asin acos atan acotan |
495 | sinh cosh tanh cotanh asinh acosh atanh acotanh |
496 | cplx cplxe |
497 | |
0a753a76 |
498 | =head2 DB_File |
499 | |
500 | There have been quite a few changes made to DB_File. Here are a few of |
501 | the highlights: |
502 | |
503 | =over |
504 | |
505 | =item * |
506 | |
507 | Fixed a handful of bugs. |
508 | |
509 | =item * |
510 | |
511 | By public demand, added support for the standard hash function exists(). |
512 | |
513 | =item * |
514 | |
515 | Made it compatible with Berkeley DB 1.86. |
516 | |
517 | =item * |
518 | |
519 | Made negative subscripts work with RECNO interface. |
520 | |
521 | =item * |
522 | |
523 | Changed the default flags from O_RDWR to O_CREAT|O_RDWR and the default |
524 | mode from 0640 to 0666. |
525 | |
526 | =item * |
527 | |
528 | Made DB_File automatically import the open() constants (O_RDWR, |
529 | O_CREAT etc.) from Fcntl, if available. |
530 | |
531 | =item * |
532 | |
533 | Updated documentation. |
534 | |
535 | =back |
536 | |
537 | Refer to the HISTORY section in DB_File.pm for a complete list of |
538 | changes. Everything after DB_File 1.01 has been added since 5.003. |
539 | |
540 | =head2 Net::Ping |
541 | |
542 | Major rewrite - support added for both udp echo and real icmp pings. |
543 | |
5f05dabc |
544 | =head2 Overridden Built-ins |
545 | |
546 | Many of the Perl built-ins returning lists now have |
547 | object-oriented overrides. These are: |
548 | |
549 | File::stat |
550 | Net::hostent |
551 | Net::netent |
552 | Net::protoent |
553 | Net::servent |
554 | Time::gmtime |
555 | Time::localtime |
556 | User::grent |
557 | User::pwent |
558 | |
559 | For example, you can now say |
560 | |
561 | use File::stat; |
562 | use User::pwent; |
563 | $his = (stat($filename)->st_uid == pwent($whoever)->pw_uid); |
564 | |
774d564b |
565 | =head1 Utility Changes |
5f05dabc |
566 | |
774d564b |
567 | =head2 xsubpp |
5f05dabc |
568 | |
0a753a76 |
569 | =over |
570 | |
774d564b |
571 | =item C<void> XSUBs now default to returning nothing |
572 | |
573 | Due to a documentation/implementation bug in previous versions of |
574 | Perl, XSUBs with a return type of C<void> have actually been |
575 | returning one value. Usually that value was the GV for the XSUB, |
576 | but sometimes it was some already freed or reused value, which would |
577 | sometimes lead to program failure. |
578 | |
579 | In Perl 5.004, if an XSUB is declared as returning C<void>, it |
580 | actually returns no value, i.e. an empty list (though there is a |
581 | backward-compatibility exception; see below). If your XSUB really |
582 | does return an SV, you should give it a return type of C<SV *>. |
583 | |
584 | For backward compatibility, I<xsubpp> tries to guess whether a |
585 | C<void> XSUB is really C<void> or if it wants to return an C<SV *>. |
586 | It does so by examining the text of the XSUB: if I<xsubpp> finds |
587 | what looks like an assignment to C<ST(0)>, it assumes that the |
588 | XSUB's return type is really C<SV *>. |
5f05dabc |
589 | |
0a753a76 |
590 | =back |
591 | |
592 | =head1 C Language API Changes |
593 | |
594 | =over |
595 | |
596 | =item C<gv_fetchmethod> and C<perl_call_sv> |
597 | |
598 | The C<gv_fetchmethod> function finds a method for an object, just like |
599 | in Perl 5.003. The GV it returns may be a method cache entry. |
600 | However, in Perl 5.004, method cache entries are not visible to users; |
601 | therefore, they can no longer be passed directly to C<perl_call_sv>. |
602 | Instead, you should use the C<GvCV> macro on the GV to extract its CV, |
603 | and pass the CV to C<perl_call_sv>. |
604 | |
605 | The most likely symptom of passing the result of C<gv_fetchmethod> to |
606 | C<perl_call_sv> is Perl's producing an "Undefined subroutine called" |
607 | error on the I<second> call to a given method (since there is no cache |
608 | on the first call). |
609 | |
610 | =back |
611 | |
5f05dabc |
612 | =head1 Documentation Changes |
613 | |
614 | Many of the base and library pods were updated. These |
615 | new pods are included in section 1: |
616 | |
0a753a76 |
617 | =over |
5f05dabc |
618 | |
774d564b |
619 | =item L<perldelta> |
5f05dabc |
620 | |
71be2cbc |
621 | This document. |
5f05dabc |
622 | |
71be2cbc |
623 | =item L<perllocale> |
5f05dabc |
624 | |
71be2cbc |
625 | Locale support (internationalization and localization). |
5f05dabc |
626 | |
627 | =item L<perltoot> |
628 | |
629 | Tutorial on Perl OO programming. |
630 | |
71be2cbc |
631 | =item L<perlapio> |
632 | |
633 | Perl internal IO abstraction interface. |
634 | |
5f05dabc |
635 | =item L<perldebug> |
636 | |
637 | Although not new, this has been massively updated. |
638 | |
639 | =item L<perlsec> |
640 | |
641 | Although not new, this has been massively updated. |
642 | |
643 | =back |
644 | |
645 | =head1 New Diagnostics |
646 | |
647 | Several new conditions will trigger warnings that were |
648 | silent before. Some only affect certain platforms. |
774d564b |
649 | The following new warnings and errors outline these. |
650 | These messages are classified as follows (listed in |
651 | increasing order of desperation): |
652 | |
653 | (W) A warning (optional). |
654 | (D) A deprecation (optional). |
655 | (S) A severe warning (mandatory). |
656 | (F) A fatal error (trappable). |
657 | (P) An internal error you should never see (trappable). |
658 | (X) A very fatal error (non-trappable). |
659 | (A) An alien error message (not generated by Perl). |
5f05dabc |
660 | |
0a753a76 |
661 | =over |
5f05dabc |
662 | |
663 | =item "my" variable %s masks earlier declaration in same scope |
664 | |
665 | (S) A lexical variable has been redeclared in the same scope, effectively |
666 | eliminating all access to the previous instance. This is almost always |
667 | a typographical error. Note that the earlier variable will still exist |
668 | until the end of the scope or until all closure referents to it are |
669 | destroyed. |
670 | |
774d564b |
671 | =item %s argument is not a HASH element or slice |
672 | |
673 | (F) The argument to delete() must be either a hash element, such as |
674 | |
675 | $foo{$bar} |
676 | $ref->[12]->{"susie"} |
677 | |
678 | or a hash slice, such as |
679 | |
680 | @foo{$bar, $baz, $xyzzy} |
681 | @{$ref->[12]}{"susie", "queue"} |
682 | |
5f05dabc |
683 | =item Allocation too large: %lx |
684 | |
685 | (X) You can't allocate more than 64K on an MSDOS machine. |
686 | |
687 | =item Allocation too large |
688 | |
689 | (F) You can't allocate more than 2^31+"small amount" bytes. |
690 | |
691 | =item Attempt to free non-existent shared string |
692 | |
693 | (P) Perl maintains a reference counted internal table of strings to |
694 | optimize the storage and access of hash keys and other strings. This |
695 | indicates someone tried to decrement the reference count of a string |
696 | that can no longer be found in the table. |
697 | |
698 | =item Attempt to use reference as lvalue in substr |
699 | |
700 | (W) You supplied a reference as the first argument to substr() used |
701 | as an lvalue, which is pretty strange. Perhaps you forgot to |
702 | dereference it first. See L<perlfunc/substr>. |
703 | |
704 | =item Unsupported function fork |
705 | |
706 | (F) Your version of executable does not support forking. |
707 | |
708 | Note that under some systems, like OS/2, there may be different flavors of |
709 | Perl executables, some of which may support fork, some not. Try changing |
710 | the name you call Perl by to C<perl_>, C<perl__>, and so on. |
711 | |
712 | =item Ill-formed logical name |%s| in prime_env_iter |
713 | |
714 | (W) A warning peculiar to VMS. A logical name was encountered when preparing |
715 | to iterate over %ENV which violates the syntactic rules governing logical |
716 | names. Since it cannot be translated normally, it is skipped, and will not |
717 | appear in %ENV. This may be a benign occurrence, as some software packages |
718 | might directly modify logical name tables and introduce non-standard names, |
719 | or it may indicate that a logical name table has been corrupted. |
720 | |
774d564b |
721 | =item Can't use bareword ("%s") as %s ref while "strict refs" in use |
722 | |
723 | (F) Only hard references are allowed by "strict refs". Symbolic references |
724 | are disallowed. See L<perlref>. |
725 | |
726 | =item Constant subroutine %s redefined |
727 | |
728 | (S) You redefined a subroutine which had previously been eligible for |
729 | inlining. See L<perlsub/"Constant Functions"> for commentary and |
730 | workarounds. |
731 | |
732 | =item Died |
733 | |
734 | (F) You passed die() an empty string (the equivalent of C<die "">) or |
735 | you called it with no args and both C<$@> and C<$_> were empty. |
736 | |
5f05dabc |
737 | =item Integer overflow in hex number |
738 | |
739 | (S) The literal hex number you have specified is too big for your |
740 | architecture. On a 32-bit architecture the largest hex literal is |
741 | 0xFFFFFFFF. |
742 | |
743 | =item Integer overflow in octal number |
744 | |
745 | (S) The literal octal number you have specified is too big for your |
746 | architecture. On a 32-bit architecture the largest octal literal is |
747 | 037777777777. |
748 | |
774d564b |
749 | =item Name "%s::%s" used only once: possible typo |
750 | |
751 | (W) Typographical errors often show up as unique variable names. |
752 | If you had a good reason for having a unique name, then just mention |
753 | it again somehow to suppress the message (the C<use vars> pragma is |
754 | provided for just this purpose). |
755 | |
5f05dabc |
756 | =item Null picture in formline |
757 | |
758 | (F) The first argument to formline must be a valid format picture |
759 | specification. It was found to be empty, which probably means you |
760 | supplied it an uninitialized value. See L<perlform>. |
761 | |
762 | =item Offset outside string |
763 | |
764 | (F) You tried to do a read/write/send/recv operation with an offset |
765 | pointing outside the buffer. This is difficult to imagine. |
766 | The sole exception to this is that C<sysread()>ing past the buffer |
767 | will extend the buffer and zero pad the new area. |
768 | |
774d564b |
769 | =item Stub found while resolving method `%s' overloading `%s' in package `%s' |
770 | |
771 | (P) Overloading resolution over @ISA tree may be broken by importing stubs. |
772 | Stubs should never be implicitely created, but explicit calls to C<can> |
773 | may break this. |
774 | |
775 | =item Cannot resolve method `%s' overloading `%s' in package `s' |
776 | |
777 | (P) Internal error trying to resolve overloading specified by a method |
778 | name (as opposed to a subroutine reference). |
779 | |
5f05dabc |
780 | =item Out of memory! |
781 | |
782 | (X|F) The malloc() function returned 0, indicating there was insufficient |
783 | remaining memory (or virtual memory) to satisfy the request. |
784 | |
785 | The request was judged to be small, so the possibility to trap it |
786 | depends on the way Perl was compiled. By default it is not trappable. |
787 | However, if compiled for this, Perl may use the contents of C<$^M> as |
788 | an emergency pool after die()ing with this message. In this case the |
789 | error is trappable I<once>. |
790 | |
791 | =item Out of memory during request for %s |
792 | |
793 | (F) The malloc() function returned 0, indicating there was insufficient |
794 | remaining memory (or virtual memory) to satisfy the request. However, |
795 | the request was judged large enough (compile-time default is 64K), so |
796 | a possibility to shut down by trapping this error is granted. |
797 | |
798 | =item Possible attempt to put comments in qw() list |
799 | |
774d564b |
800 | (W) qw() lists contain items separated by whitespace; as with literal |
801 | strings, comment characters are not ignored, but are instead treated |
802 | as literal data. (You may have used different delimiters than the |
803 | exclamation marks parentheses shown here; braces are also frequently |
804 | used.) |
805 | |
806 | You probably wrote something like this: |
5f05dabc |
807 | |
774d564b |
808 | @list = qw( |
809 | a # a comment |
5f05dabc |
810 | b # another comment |
774d564b |
811 | ); |
5f05dabc |
812 | |
813 | when you should have written this: |
814 | |
774d564b |
815 | @list = qw( |
816 | a |
5f05dabc |
817 | b |
774d564b |
818 | ); |
819 | |
820 | If you really want comments, build your list the |
821 | old-fashioned way, with quotes and commas: |
822 | |
823 | @list = ( |
824 | 'a', # a comment |
825 | 'b', # another comment |
826 | ); |
5f05dabc |
827 | |
828 | =item Possible attempt to separate words with commas |
829 | |
774d564b |
830 | (W) qw() lists contain items separated by whitespace; therefore commas |
831 | aren't needed to separate the items. (You may have used different |
832 | delimiters than the parentheses shown here; braces are also frequently |
833 | used.) |
5f05dabc |
834 | |
774d564b |
835 | You probably wrote something like this: |
5f05dabc |
836 | |
774d564b |
837 | qw! a, b, c !; |
838 | |
839 | which puts literal commas into some of the list items. Write it without |
840 | commas if you don't want them to appear in your data: |
841 | |
842 | qw! a b c !; |
5f05dabc |
843 | |
774d564b |
844 | =item Scalar value @%s{%s} better written as $%s{%s} |
845 | |
846 | (W) You've used a hash slice (indicated by @) to select a single element of |
847 | a hash. Generally it's better to ask for a scalar value (indicated by $). |
848 | The difference is that C<$foo{&bar}> always behaves like a scalar, both when |
849 | assigning to it and when evaluating its argument, while C<@foo{&bar}> behaves |
850 | like a list when you assign to it, and provides a list context to its |
851 | subscript, which can do weird things if you're expecting only one subscript. |
5f05dabc |
852 | |
853 | =item untie attempted while %d inner references still exist |
854 | |
855 | (W) A copy of the object returned from C<tie> (or C<tied>) was still |
856 | valid when C<untie> was called. |
857 | |
774d564b |
858 | =item Value of %s construct can be "0"; test with defined() |
859 | |
860 | (W) In a conditional expression, you used <HANDLE>, <*> (glob), or |
861 | C<readdir> as a boolean value. Each of these constructs can return a |
862 | value of "0"; that would make the conditional expression false, which |
863 | is probably not what you intended. When using these constructs in |
864 | conditional expressions, test their values with the C<defined> operator. |
865 | |
866 | =item Variable "%s" may be unavailable |
867 | |
868 | (W) An inner (nested) I<anonymous> subroutine is inside a I<named> |
869 | subroutine, and outside that is another subroutine; and the anonymous |
870 | (innermost) subroutine is referencing a lexical variable defined in |
871 | the outermost subroutine. For example: |
872 | |
873 | sub outermost { my $a; sub middle { sub { $a } } } |
874 | |
875 | If the anonymous subroutine is called or referenced (directly or |
876 | indirectly) from the outermost subroutine, it will share the variable |
877 | as you would expect. But if the anonymous subroutine is called or |
878 | referenced when the outermost subroutine is not active, it will see |
879 | the value of the shared variable as it was before and during the |
880 | *first* call to the outermost subroutine, which is probably not what |
881 | you want. |
882 | |
883 | In these circumstances, it is usually best to make the middle |
884 | subroutine anonymous, using the C<sub {}> syntax. Perl has specific |
885 | support for shared variables in nested anonymous subroutines; a named |
886 | subroutine in between interferes with this feature. |
887 | |
888 | =item Variable "%s" will not stay shared |
889 | |
890 | (W) An inner (nested) I<named> subroutine is referencing a lexical |
891 | variable defined in an outer subroutine. |
892 | |
893 | When the inner subroutine is called, it will probably see the value of |
894 | the outer subroutine's variable as it was before and during the |
895 | *first* call to the outer subroutine; in this case, after the first |
896 | call to the outer subroutine is complete, the inner and outer |
897 | subroutines will no longer share a common value for the variable. In |
898 | other words, the variable will no longer be shared. |
899 | |
900 | Furthermore, if the outer subroutine is anonymous and references a |
901 | lexical variable outside itself, then the outer and inner subroutines |
902 | will I<never> share the given variable. |
903 | |
904 | This problem can usually be solved by making the inner subroutine |
905 | anonymous, using the C<sub {}> syntax. When inner anonymous subs that |
906 | reference variables in outer subroutines are called or referenced, |
907 | they are automatically re-bound to the current values of such |
908 | variables. |
909 | |
910 | =item Warning: something's wrong |
911 | |
912 | (W) You passed warn() an empty string (the equivalent of C<warn "">) or |
913 | you called it with no args and C<$_> was empty. |
914 | |
915 | =item Got an error from DosAllocMem |
5f05dabc |
916 | |
774d564b |
917 | (P) An error peculiar to OS/2. Most probably you're using an obsolete |
918 | version of Perl, and this should not happen anyway. |
5f05dabc |
919 | |
920 | =item Malformed PERLLIB_PREFIX |
921 | |
922 | (F) An error peculiar to OS/2. PERLLIB_PREFIX should be of the form |
923 | |
924 | prefix1;prefix2 |
925 | |
926 | or |
927 | |
928 | prefix1 prefix2 |
929 | |
930 | with non-empty prefix1 and prefix2. If C<prefix1> is indeed a prefix of |
931 | a builtin library search path, prefix2 is substituted. The error may appear |
932 | if components are not found, or are too long. See L<perlos2/"PERLLIB_PREFIX">. |
933 | |
934 | =item PERL_SH_DIR too long |
935 | |
936 | (F) An error peculiar to OS/2. PERL_SH_DIR is the directory to find the |
937 | C<sh>-shell in. See L<perlos2/"PERL_SH_DIR">. |
938 | |
939 | =item Process terminated by SIG%s |
940 | |
941 | (W) This is a standard message issued by OS/2 applications, while *nix |
942 | applications die in silence. It is considered a feature of the OS/2 |
943 | port. One can easily disable this by appropriate sighandlers, see |
944 | L<perlipc/"Signals">. See L<perlos2/"Process terminated by SIGTERM/SIGINT">. |
945 | |
946 | =back |
947 | |
948 | =head1 BUGS |
949 | |
774d564b |
950 | If you find what you think is a bug, you might check the headers of |
951 | recently posted articles in the comp.lang.perl.misc newsgroup. |
952 | There may also be information at http://www.perl.com/perl/, the Perl |
953 | Home Page. |
5f05dabc |
954 | |
955 | If you believe you have an unreported bug, please run the B<perlbug> |
956 | program included with your release. Make sure you trim your bug |
957 | down to a tiny but sufficient test case. Your bug report, along |
958 | with the output of C<perl -V>, will be sent off to perlbug@perl.com |
959 | to be analysed by the Perl porting team. |
960 | |
961 | =head1 SEE ALSO |
962 | |
963 | The F<Changes> file for exhaustive details on what changed. |
964 | |
965 | The F<INSTALL> file for how to build Perl. This file has been |
966 | significantly updated for 5.004, so even veteran users should |
967 | look through it. |
968 | |
969 | The F<README> file for general stuff. |
970 | |
971 | The F<Copying> file for copyright information. |
972 | |
973 | =head1 HISTORY |
974 | |
975 | Constructed by Tom Christiansen, grabbing material with permission |
976 | from innumerable contributors, with kibitzing by more than a few Perl |
977 | porters. |
978 | |
44a8e56a |
979 | Last update: Tue Jan 14 14:03:02 EST 1997 |