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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 Subroutine Parameters Are Not Autovivified |
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31 | |
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32 | In Perl versions 5.002 and 5.003, array and hash elements used as |
33 | subroutine parameters were "autovivified"; that is, they were brought |
34 | into existence if they did not already exist. For example, calling |
35 | C<func($h{foo})> would create C<$h{foo}> if it did not already exist, |
36 | causing C<exists $h{foo}> to become true and C<keys %h> to return |
37 | C<('foo')>. |
38 | |
39 | Perl 5.004 returns to the pre-5.002 behavior of I<not> autovivifying |
40 | array and hash elements used as subroutine parameters. |
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41 | |
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42 | =head2 Fixed Parsing of $$<digit>, &$<digit>, etc. |
43 | |
44 | A bug in previous versions of Perl 5.0 prevented proper parsing of |
45 | numeric special variables as symbolic references. That bug has been |
46 | fixed. As a result, the string "$$0" is no longer equivalent to |
47 | C<$$."0">, but rather to C<${$0}>. To get the old behavior, change |
48 | "$$" followed by a digit to "${$}". |
49 | |
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50 | =head2 Changes to Tainting Checks |
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51 | |
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52 | A bug in previous versions may have failed to detect some insecure |
53 | conditions when taint checks are turned on. (Taint checks are used |
54 | in setuid or setgid scripts, or when explicitly turned on with the |
55 | C<-T> invocation option.) Although it's unlikely, this may cause a |
56 | previously-working script to now fail -- which should be construed |
57 | as a blessing, since that indicates a potentially-serious security |
58 | hole was just plugged. |
59 | |
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60 | =head2 New Opcode Module and Revised Safe Module |
61 | |
62 | A new Opcode module supports the creation, manipulation and |
63 | application of opcode masks. The revised Safe module has a new API |
64 | and is implemented using the new Opcode module. Please read the new |
65 | Opcode and Safe documentation. |
66 | |
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67 | =head2 Internal Change: FileHandle Class Based on IO::* Classes |
68 | |
69 | File handles are now stored internally as type IO::Handle. The |
70 | FileHandle module is still supported for backwards compatibility, but |
71 | it is now merely a front end to the IO::* modules -- specifically, |
72 | IO::Handle, IO::Seekable, and IO::File. We suggest, but do not |
73 | require, that you use the IO::* modules in new code. |
74 | |
75 | In harmony with this change, C<*GLOB{FILEHANDLE}> is now a |
76 | backward-compatible synonym for C<*STDOUT{IO}>. |
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77 | |
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78 | =head2 Internal Change: PerlIO internal IO abstraction interface |
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79 | |
80 | It is now possible to build Perl with AT&T's sfio IO package |
81 | instead of stdio. See L<perlapio> for more details, and |
82 | the F<INSTALL> file for how to use it. |
83 | |
84 | =head2 New and Changed Built-in Variables |
85 | |
86 | =over |
87 | |
88 | =item $^E |
89 | |
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90 | Extended error message on some platforms. (Also known as |
91 | $EXTENDED_OS_ERROR if you C<use English>). |
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92 | |
93 | =item $^H |
94 | |
95 | The current set of syntax checks enabled by C<use strict>. See the |
96 | documentation of C<strict> for more details. Not actually new, but |
97 | newly documented. |
98 | Because it is intended for internal use by Perl core components, |
99 | there is no C<use English> long name for this variable. |
100 | |
101 | =item $^M |
102 | |
103 | By default, running out of memory it is not trappable. However, if |
104 | compiled for this, Perl may use the contents of C<$^M> as an emergency |
105 | pool after die()ing with this message. Suppose that your Perl were |
106 | compiled with -DEMERGENCY_SBRK and used Perl's malloc. Then |
107 | |
108 | $^M = 'a' x (1<<16); |
109 | |
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110 | would allocate a 64K buffer for use when in emergency. |
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111 | See the F<INSTALL> file for information on how to enable this option. |
112 | As a disincentive to casual use of this advanced feature, |
113 | there is no C<use English> long name for this variable. |
114 | |
115 | =back |
116 | |
117 | =head2 New and Changed Built-in Functions |
118 | |
119 | =over |
120 | |
121 | =item delete on slices |
122 | |
123 | This now works. (e.g. C<delete @ENV{'PATH', 'MANPATH'}>) |
124 | |
125 | =item flock |
126 | |
127 | is now supported on more platforms, and prefers fcntl |
128 | to lockf when emulating. |
129 | |
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130 | =item printf and sprintf |
131 | |
132 | now support "%i" as a synonym for "%d", and the "h" modifier. |
133 | So "%hi" means "short integer in decimal", and "%ho" means |
134 | "unsigned short integer as octal". |
135 | |
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136 | =item keys as an lvalue |
137 | |
138 | As an lvalue, C<keys> allows you to increase the number of hash buckets |
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139 | allocated for the given hash. This can gain you a measure of efficiency if |
140 | you know the hash is going to get big. (This is similar to pre-extending |
141 | an array by assigning a larger number to $#array.) If you say |
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142 | |
143 | keys %hash = 200; |
144 | |
145 | then C<%hash> will have at least 200 buckets allocated for it. These |
146 | buckets will be retained even if you do C<%hash = ()>; use C<undef |
147 | %hash> if you want to free the storage while C<%hash> is still in scope. |
148 | You can't shrink the number of buckets allocated for the hash using |
149 | C<keys> in this way (but you needn't worry about doing this by accident, |
150 | as trying has no effect). |
151 | |
152 | =item my() in Control Structures |
153 | |
154 | You can now use my() (with or without the parentheses) in the control |
155 | expressions of control structures such as: |
156 | |
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157 | while (defined(my $line = <>)) { |
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158 | $line = lc $line; |
159 | } continue { |
160 | print $line; |
161 | } |
162 | |
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163 | if ((my $answer = <STDIN>) =~ /^y(es)?$/i) { |
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164 | user_agrees(); |
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165 | } elsif ($answer =~ /^n(o)?$/i) { |
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166 | user_disagrees(); |
167 | } else { |
168 | chomp $answer; |
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169 | die "`$answer' is neither `yes' nor `no'"; |
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170 | } |
171 | |
172 | Also, you can declare a foreach loop control variable as lexical by |
173 | preceding it with the word "my". For example, in: |
174 | |
175 | foreach my $i (1, 2, 3) { |
176 | some_function(); |
177 | } |
178 | |
179 | $i is a lexical variable, and the scope of $i extends to the end of |
180 | the loop, but not beyond it. |
181 | |
182 | Note that you still cannot use my() on global punctuation variables |
183 | such as $_ and the like. |
184 | |
185 | =item unpack() and pack() |
186 | |
187 | A new format 'w' represents a BER compressed integer (as defined in |
188 | ASN.1). Its format is a sequence of one or more bytes, each of which |
189 | provides seven bits of the total value, with the most significant |
190 | first. Bit eight of each byte is set, except for the last byte, in |
191 | which bit eight is clear. |
192 | |
193 | =item use VERSION |
194 | |
195 | If the first argument to C<use> is a number, it is treated as a version |
196 | number instead of a module name. If the version of the Perl interpreter |
197 | is less than VERSION, then an error message is printed and Perl exits |
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198 | immediately. Because C<use> occurs at compile time, this check happens |
199 | immediately during the compilation process, unlike C<require VERSION>, |
200 | which waits until run-time for the check. This is often useful if you |
201 | need to check the current Perl version before C<use>ing library modules |
202 | which have changed in incompatible ways from older versions of Perl. |
203 | (We try not to do this more than we have to.) |
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204 | |
205 | =item use Module VERSION LIST |
206 | |
207 | If the VERSION argument is present between Module and LIST, then the |
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208 | C<use> will call the VERSION method in class Module with the given |
209 | version as an argument. The default VERSION method, inherited from |
210 | the Universal class, croaks if the given version is larger than the |
211 | value of the variable $Module::VERSION. (Note that there is not a |
212 | comma after VERSION!) |
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213 | |
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214 | This version-checking mechanism is similar to the one currently used |
215 | in the Exporter module, but it is faster and can be used with modules |
216 | that don't use the Exporter. It is the recommended method for new |
217 | code. |
218 | |
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219 | =item prototype(FUNCTION) |
220 | |
221 | Returns the prototype of a function as a string (or C<undef> if the |
222 | function has no prototype). FUNCTION is a reference to or the name of the |
223 | function whose prototype you want to retrieve. |
224 | (Not actually new; just never documented before.) |
225 | |
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226 | =item srand |
227 | |
228 | The default seed for C<srand>, which used to be C<time>, has been changed. |
229 | Now it's a heady mix of difficult-to-predict system-dependent values, |
230 | which should be sufficient for most everyday purposes. |
231 | |
232 | Previous to version 5.004, calling C<rand> without first calling C<srand> |
233 | would yield the same sequence of random numbers on most or all machines. |
234 | Now, when perl sees that you're calling C<rand> and haven't yet called |
235 | C<srand>, it calls C<srand> with the default seed. You should still call |
236 | C<srand> manually if your code might ever be run on a pre-5.004 system, |
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237 | of course, or if you want a seed other than the default. |
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238 | |
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239 | =item $_ as Default |
240 | |
241 | Functions documented in the Camel to default to $_ now in |
242 | fact do, and all those that do are so documented in L<perlfunc>. |
243 | |
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244 | =item C<m//g> does not trigger a pos() reset on failure |
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245 | |
246 | The C<m//g> match iteration construct used to reset the iteration |
247 | when it failed to match (so that the next C<m//g> match would start at |
248 | the beginning of the string). You now have to explicitly do a |
249 | C<pos $str = 0;> to reset the "last match" position, or modify the |
250 | string in some way. This change makes it practical to chain C<m//g> |
251 | matches together in conjunction with ordinary matches using the C<\G> |
252 | zero-width assertion. See L<perlop> and L<perlre>. |
253 | |
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254 | =item nested C<sub{}> closures work now |
255 | |
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256 | Prior to the 5.004 release, nested anonymous functions didn't work |
257 | right. They do now. |
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258 | |
259 | =item formats work right on changing lexicals |
260 | |
261 | Just like anonymous functions that contain lexical variables |
262 | that change (like a lexical index variable for a C<foreach> loop), |
263 | formats now work properly. For example, this silently failed |
264 | before, and is fine now: |
265 | |
266 | my $i; |
267 | foreach $i ( 1 .. 10 ) { |
268 | format = |
269 | my i is @# |
270 | $i |
271 | . |
272 | write; |
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273 | } |
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274 | |
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275 | =back |
276 | |
277 | =head2 New Built-in Methods |
278 | |
279 | The C<UNIVERSAL> package automatically contains the following methods that |
280 | are inherited by all other classes: |
281 | |
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282 | =over |
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283 | |
284 | =item isa(CLASS) |
285 | |
286 | C<isa> returns I<true> if its object is blessed into a sub-class of C<CLASS> |
287 | |
288 | C<isa> is also exportable and can be called as a sub with two arguments. This |
289 | allows the ability to check what a reference points to. Example: |
290 | |
291 | use UNIVERSAL qw(isa); |
292 | |
293 | if(isa($ref, 'ARRAY')) { |
294 | ... |
295 | } |
296 | |
297 | =item can(METHOD) |
298 | |
299 | C<can> checks to see if its object has a method called C<METHOD>, |
300 | if it does then a reference to the sub is returned; if it does not then |
301 | I<undef> is returned. |
302 | |
303 | =item VERSION( [NEED] ) |
304 | |
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305 | C<VERSION> returns the version number of the class (package). If the |
306 | NEED argument is given then it will check that the current version (as |
307 | defined by the $VERSION variable in the given package) not less than |
308 | NEED; it will die if this is not the case. This method is normally |
309 | called as a class method. This method is called automatically by the |
310 | C<VERSION> form of C<use>. |
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311 | |
312 | use A 1.2 qw(some imported subs); |
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313 | # implies: |
314 | A->VERSION(1.2); |
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315 | |
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316 | =back |
317 | |
318 | B<NOTE:> C<can> directly uses Perl's internal code for method lookup, and |
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319 | C<isa> uses a very similar method and caching strategy. This may cause |
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320 | strange effects if the Perl code dynamically changes @ISA in any package. |
321 | |
322 | You may add other methods to the UNIVERSAL class via Perl or XS code. |
323 | You do not need to C<use UNIVERSAL> in order to make these methods |
324 | available to your program. This is necessary only if you wish to |
325 | have C<isa> available as a plain subroutine in the current package. |
326 | |
327 | =head2 TIEHANDLE Now Supported |
328 | |
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329 | See L<perltie> for other kinds of tie()s. |
330 | |
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331 | =over |
332 | |
333 | =item TIEHANDLE classname, LIST |
334 | |
335 | This is the constructor for the class. That means it is expected to |
336 | return an object of some sort. The reference can be used to |
337 | hold some internal information. |
338 | |
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339 | sub TIEHANDLE { |
340 | print "<shout>\n"; |
341 | my $i; |
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342 | return bless \$i, shift; |
343 | } |
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344 | |
345 | =item PRINT this, LIST |
346 | |
347 | This method will be triggered every time the tied handle is printed to. |
348 | Beyond its self reference it also expects the list that was passed to |
349 | the print function. |
350 | |
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351 | sub PRINT { |
352 | $r = shift; |
353 | $$r++; |
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354 | return print join( $, => map {uc} @_), $\; |
355 | } |
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356 | |
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357 | =item READ this LIST |
358 | |
359 | This method will be called when the handle is read from via the C<read> |
360 | or C<sysread> functions. |
361 | |
362 | sub READ { |
363 | $r = shift; |
364 | my($buf,$len,$offset) = @_; |
365 | print "READ called, \$buf=$buf, \$len=$len, \$offset=$offset"; |
366 | } |
367 | |
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368 | =item READLINE this |
369 | |
370 | This method will be called when the handle is read from. The method |
371 | should return undef when there is no more data. |
372 | |
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373 | sub READLINE { |
374 | $r = shift; |
375 | return "PRINT called $$r times\n" |
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376 | } |
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377 | |
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378 | =item GETC this |
379 | |
380 | This method will be called when the C<getc> function is called. |
381 | |
382 | sub GETC { print "Don't GETC, Get Perl"; return "a"; } |
383 | |
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384 | =item DESTROY this |
385 | |
386 | As with the other types of ties, this method will be called when the |
387 | tied handle is about to be destroyed. This is useful for debugging and |
388 | possibly for cleaning up. |
389 | |
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390 | sub DESTROY { |
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391 | print "</shout>\n"; |
392 | } |
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393 | |
394 | =back |
395 | |
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396 | =head2 Malloc Enhancements |
397 | |
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398 | Four new compilation flags are recognized by malloc.c. (They have no |
399 | effect if perl is compiled with system malloc().) |
400 | |
401 | =over |
402 | |
403 | =item -DDEBUGGING_MSTATS |
404 | |
405 | If perl is compiled with C<DEBUGGING_MSTATS> defined, you can print |
406 | memory statistics at runtime by running Perl thusly: |
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407 | |
408 | env PERL_DEBUG_MSTATS=2 perl your_script_here |
409 | |
410 | The value of 2 means to print statistics after compilation and on |
411 | exit; with a value of 1, the statistics ares printed only on exit. |
412 | (If you want the statistics at an arbitrary time, you'll need to |
413 | install the optional module Devel::Peek.) |
414 | |
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415 | =item -DEMERGENCY_SBRK |
416 | |
417 | If this macro is defined, running out of memory need not be a fatal |
418 | error: a memory pool can allocated by assigning to the special |
419 | variable C<$^M>. See L<"$^M">. |
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420 | |
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421 | =item -DPACK_MALLOC |
422 | |
423 | Perl memory allocation is by bucket with sizes close to powers of two. |
424 | Because of these malloc overhead may be big, especially for data of |
425 | size exactly a power of two. If C<PACK_MALLOC> is defined, perl uses |
426 | a slightly different algorithm for small allocations (up to 64 bytes |
427 | long), which makes it possible to have overhead down to 1 byte for |
428 | allocations which are powers of two (and appear quite often). |
429 | |
430 | Expected memory savings (with 8-byte alignment in C<alignbytes>) is |
431 | about 20% for typical Perl usage. Expected slowdown due to additional |
432 | malloc overhead is in fractions of a percent (hard to measure, because |
433 | of the effect of saved memory on speed). |
434 | |
435 | =item -DTWO_POT_OPTIMIZE |
436 | |
437 | Similarly to C<PACK_MALLOC>, this macro improves allocations of data |
438 | with size close to a power of two; but this works for big allocations |
439 | (starting with 16K by default). Such allocations are typical for big |
440 | hashes and special-purpose scripts, especially image processing. |
441 | |
442 | On recent systems, the fact that perl requires 2M from system for 1M |
443 | allocation will not affect speed of execution, since the tail of such |
444 | a chunk is not going to be touched (and thus will not require real |
445 | memory). However, it may result in a premature out-of-memory error. |
446 | So if you will be manipulating very large blocks with sizes close to |
447 | powers of two, it would be wise to define this macro. |
448 | |
449 | Expected saving of memory is 0-100% (100% in applications which |
450 | require most memory in such 2**n chunks); expected slowdown is |
451 | negligible. |
452 | |
453 | =back |
454 | |
455 | =head2 Miscellaneous Efficiency Enhancements |
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456 | |
457 | Functions that have an empty prototype and that do nothing but return |
458 | a fixed value are now inlined (e.g. C<sub PI () { 3.14159 }>). |
459 | |
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460 | Each unique hash key is only allocated once, no matter how many hashes |
461 | have an entry with that key. So even if you have 100 copies of the |
462 | same hash, the hash keys never have to be re-allocated. |
463 | |
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464 | =head1 Pragmata |
465 | |
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466 | Four new pragmatic modules exist: |
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467 | |
468 | =over |
469 | |
470 | =item use blib |
471 | |
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472 | =item use blib 'dir' |
473 | |
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474 | Looks for MakeMaker-like I<'blib'> directory structure starting in |
475 | I<dir> (or current directory) and working back up to five levels of |
476 | parent directories. |
477 | |
478 | Intended for use on command line with B<-M> option as a way of testing |
479 | arbitrary scripts against an uninstalled version of a package. |
480 | |
481 | =item use locale |
482 | |
483 | Tells the compiler to enable (or disable) the use of POSIX locales for |
484 | built-in operations. |
485 | |
486 | When C<use locale> is in effect, the current LC_CTYPE locale is used |
487 | for regular expressions and case mapping; LC_COLLATE for string |
488 | ordering; and LC_NUMERIC for numeric formating in printf and sprintf |
489 | (but B<not> in print). LC_NUMERIC is always used in write, since |
490 | lexical scoping of formats is problematic at best. |
491 | |
492 | Each C<use locale> or C<no locale> affects statements to the end of |
493 | the enclosing BLOCK or, if not inside a BLOCK, to the end of the |
494 | current file. Locales can be switched and queried with |
495 | POSIX::setlocale(). |
496 | |
497 | See L<perllocale> for more information. |
498 | |
499 | =item use ops |
500 | |
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501 | Disable unsafe opcodes, or any named opcodes, when compiling Perl code. |
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502 | |
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503 | =item use vmsish |
504 | |
505 | Enable VMS-specific language features. Currently, there are three |
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506 | VMS-specific features available: 'status', which makes C<$?> and |
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507 | C<system> return genuine VMS status values instead of emulating POSIX; |
508 | 'exit', which makes C<exit> take a genuine VMS status value instead of |
509 | assuming that C<exit 1> is an error; and 'time', which makes all times |
510 | relative to the local time zone, in the VMS tradition. |
511 | |
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512 | =back |
513 | |
514 | =head1 Modules |
515 | |
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516 | =head2 Installation Directories |
517 | |
518 | The I<installperl> script now places the Perl source files for |
519 | extensions in the architecture-specific library directory, which is |
520 | where the shared libraries for extensions have always been. This |
521 | change is intended to allow administrators to keep the Perl 5.004 |
522 | library directory unchanged from a previous version, without running |
523 | the risk of binary incompatibility between extensions' Perl source and |
524 | shared libraries. |
525 | |
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526 | =head2 Fcntl |
527 | |
528 | New constants in the existing Fcntl modules are now supported, |
529 | provided that your operating system happens to support them: |
530 | |
531 | F_GETOWN F_SETOWN |
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532 | O_ASYNC O_DEFER O_DSYNC O_FSYNC O_SYNC |
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533 | O_EXLOCK O_SHLOCK |
534 | |
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535 | These constants are intended for use with the Perl operators sysopen() |
536 | and fcntl() and the basic database modules like SDBM_File. For the |
537 | exact meaning of these and other Fcntl constants please refer to your |
538 | operating system's documentation for fcntl() and open(). |
539 | |
540 | In addition, the Fcntl module now provides these constants for use |
541 | with the Perl operator flock(): |
542 | |
543 | LOCK_SH LOCK_EX LOCK_NB LOCK_UN |
544 | |
545 | These constants are defined in all environments (because where there is |
546 | no flock() system call, Perl emulates it). However, for historical |
547 | reasons, these constants are not exported unless they are explicitly |
548 | requested with the ":flock" tag (e.g. C<use Fcntl ':flock'>). |
549 | |
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550 | =head2 Module Information Summary |
551 | |
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552 | Brand new modules, arranged by topic rather than strictly |
553 | alphabetically: |
554 | |
555 | CPAN interface to Comprehensive Perl Archive Network |
556 | CPAN::FirstTime create a CPAN configuration file |
557 | CPAN::Nox run CPAN while avoiding compiled extensions |
5f05dabc |
558 | |
559 | IO.pm Top-level interface to IO::* classes |
560 | IO/File.pm IO::File extension Perl module |
561 | IO/Handle.pm IO::Handle extension Perl module |
562 | IO/Pipe.pm IO::Pipe extension Perl module |
563 | IO/Seekable.pm IO::Seekable extension Perl module |
564 | IO/Select.pm IO::Select extension Perl module |
565 | IO/Socket.pm IO::Socket extension Perl module |
566 | |
567 | Opcode.pm Disable named opcodes when compiling Perl code |
568 | |
569 | ExtUtils/Embed.pm Utilities for embedding Perl in C programs |
570 | ExtUtils/testlib.pm Fixes up @INC to use just-built extension |
571 | |
5f05dabc |
572 | FindBin.pm Find path of currently executing program |
573 | |
574 | Class/Template.pm Structure/member template builder |
575 | File/stat.pm Object-oriented wrapper around CORE::stat |
576 | Net/hostent.pm Object-oriented wrapper around CORE::gethost* |
577 | Net/netent.pm Object-oriented wrapper around CORE::getnet* |
578 | Net/protoent.pm Object-oriented wrapper around CORE::getproto* |
579 | Net/servent.pm Object-oriented wrapper around CORE::getserv* |
580 | Time/gmtime.pm Object-oriented wrapper around CORE::gmtime |
581 | Time/localtime.pm Object-oriented wrapper around CORE::localtime |
582 | Time/tm.pm Perl implementation of "struct tm" for {gm,local}time |
583 | User/grent.pm Object-oriented wrapper around CORE::getgr* |
584 | User/pwent.pm Object-oriented wrapper around CORE::getpw* |
585 | |
774d564b |
586 | Tie/RefHash.pm Base class for tied hashes with references as keys |
7a4c00b4 |
587 | |
5f05dabc |
588 | UNIVERSAL.pm Base class for *ALL* classes |
589 | |
590 | =head2 IO |
591 | |
592 | The IO module provides a simple mechanism to load all of the IO modules at one |
593 | go. Currently this includes: |
594 | |
595 | IO::Handle |
596 | IO::Seekable |
597 | IO::File |
598 | IO::Pipe |
599 | IO::Socket |
600 | |
601 | For more information on any of these modules, please see its |
602 | respective documentation. |
603 | |
604 | =head2 Math::Complex |
605 | |
606 | The Math::Complex module has been totally rewritten, and now supports |
607 | more operations. These are overloaded: |
608 | |
609 | + - * / ** <=> neg ~ abs sqrt exp log sin cos atan2 "" (stringify) |
610 | |
611 | And these functions are now exported: |
612 | |
613 | pi i Re Im arg |
614 | log10 logn cbrt root |
615 | tan cotan asin acos atan acotan |
616 | sinh cosh tanh cotanh asinh acosh atanh acotanh |
617 | cplx cplxe |
618 | |
0a753a76 |
619 | =head2 DB_File |
620 | |
621 | There have been quite a few changes made to DB_File. Here are a few of |
622 | the highlights: |
623 | |
624 | =over |
625 | |
626 | =item * |
627 | |
628 | Fixed a handful of bugs. |
629 | |
630 | =item * |
631 | |
632 | By public demand, added support for the standard hash function exists(). |
633 | |
634 | =item * |
635 | |
636 | Made it compatible with Berkeley DB 1.86. |
637 | |
638 | =item * |
639 | |
640 | Made negative subscripts work with RECNO interface. |
641 | |
642 | =item * |
643 | |
644 | Changed the default flags from O_RDWR to O_CREAT|O_RDWR and the default |
645 | mode from 0640 to 0666. |
646 | |
647 | =item * |
648 | |
649 | Made DB_File automatically import the open() constants (O_RDWR, |
650 | O_CREAT etc.) from Fcntl, if available. |
651 | |
652 | =item * |
653 | |
654 | Updated documentation. |
655 | |
656 | =back |
657 | |
658 | Refer to the HISTORY section in DB_File.pm for a complete list of |
659 | changes. Everything after DB_File 1.01 has been added since 5.003. |
660 | |
661 | =head2 Net::Ping |
662 | |
663 | Major rewrite - support added for both udp echo and real icmp pings. |
664 | |
5f05dabc |
665 | =head2 Overridden Built-ins |
666 | |
667 | Many of the Perl built-ins returning lists now have |
668 | object-oriented overrides. These are: |
669 | |
670 | File::stat |
671 | Net::hostent |
672 | Net::netent |
673 | Net::protoent |
674 | Net::servent |
675 | Time::gmtime |
676 | Time::localtime |
677 | User::grent |
678 | User::pwent |
679 | |
680 | For example, you can now say |
681 | |
682 | use File::stat; |
683 | use User::pwent; |
684 | $his = (stat($filename)->st_uid == pwent($whoever)->pw_uid); |
685 | |
774d564b |
686 | =head1 Utility Changes |
5f05dabc |
687 | |
774d564b |
688 | =head2 xsubpp |
5f05dabc |
689 | |
0a753a76 |
690 | =over |
691 | |
774d564b |
692 | =item C<void> XSUBs now default to returning nothing |
693 | |
694 | Due to a documentation/implementation bug in previous versions of |
695 | Perl, XSUBs with a return type of C<void> have actually been |
696 | returning one value. Usually that value was the GV for the XSUB, |
697 | but sometimes it was some already freed or reused value, which would |
698 | sometimes lead to program failure. |
699 | |
700 | In Perl 5.004, if an XSUB is declared as returning C<void>, it |
701 | actually returns no value, i.e. an empty list (though there is a |
702 | backward-compatibility exception; see below). If your XSUB really |
703 | does return an SV, you should give it a return type of C<SV *>. |
704 | |
705 | For backward compatibility, I<xsubpp> tries to guess whether a |
706 | C<void> XSUB is really C<void> or if it wants to return an C<SV *>. |
707 | It does so by examining the text of the XSUB: if I<xsubpp> finds |
708 | what looks like an assignment to C<ST(0)>, it assumes that the |
709 | XSUB's return type is really C<SV *>. |
5f05dabc |
710 | |
0a753a76 |
711 | =back |
712 | |
713 | =head1 C Language API Changes |
714 | |
715 | =over |
716 | |
717 | =item C<gv_fetchmethod> and C<perl_call_sv> |
718 | |
719 | The C<gv_fetchmethod> function finds a method for an object, just like |
720 | in Perl 5.003. The GV it returns may be a method cache entry. |
721 | However, in Perl 5.004, method cache entries are not visible to users; |
722 | therefore, they can no longer be passed directly to C<perl_call_sv>. |
723 | Instead, you should use the C<GvCV> macro on the GV to extract its CV, |
724 | and pass the CV to C<perl_call_sv>. |
725 | |
726 | The most likely symptom of passing the result of C<gv_fetchmethod> to |
727 | C<perl_call_sv> is Perl's producing an "Undefined subroutine called" |
728 | error on the I<second> call to a given method (since there is no cache |
729 | on the first call). |
730 | |
1e422769 |
731 | =item Extended API for manipulating hashes |
732 | |
733 | Internal handling of hash keys has changed. The old hashtable API is |
734 | still fully supported, and will likely remain so. The additions to the |
735 | API allow passing keys as C<SV*>s, so that C<tied> hashes can be given |
736 | real scalars as keys rather than plain strings (non-tied hashes still |
737 | can only use strings as keys). New extensions must use the new hash |
738 | access functions and macros if they wish to use C<SV*> keys. These |
739 | additions also make it feasible to manipulate C<HE*>s (hash entries), |
740 | which can be more efficient. See L<perlguts> for details. |
741 | |
63a6ff3a |
742 | =item Embedding improvements |
743 | |
744 | In older versions of Perl it was not possible to create more than one |
745 | instance of a Perl interpreter inside the same process without leaking |
746 | like mad and/or crashing. The major bugs which caused this behavior |
747 | have been fixed, however, you still must take care when embedding Perl |
748 | in a C program. See the updated perlembed manpage for tips on how to |
749 | manage your interpreters. |
750 | |
0a753a76 |
751 | =back |
752 | |
5f05dabc |
753 | =head1 Documentation Changes |
754 | |
755 | Many of the base and library pods were updated. These |
756 | new pods are included in section 1: |
757 | |
0a753a76 |
758 | =over |
5f05dabc |
759 | |
774d564b |
760 | =item L<perldelta> |
5f05dabc |
761 | |
71be2cbc |
762 | This document. |
5f05dabc |
763 | |
71be2cbc |
764 | =item L<perllocale> |
5f05dabc |
765 | |
71be2cbc |
766 | Locale support (internationalization and localization). |
5f05dabc |
767 | |
768 | =item L<perltoot> |
769 | |
770 | Tutorial on Perl OO programming. |
771 | |
71be2cbc |
772 | =item L<perlapio> |
773 | |
774 | Perl internal IO abstraction interface. |
775 | |
5f05dabc |
776 | =item L<perldebug> |
777 | |
778 | Although not new, this has been massively updated. |
779 | |
780 | =item L<perlsec> |
781 | |
782 | Although not new, this has been massively updated. |
783 | |
784 | =back |
785 | |
786 | =head1 New Diagnostics |
787 | |
788 | Several new conditions will trigger warnings that were |
789 | silent before. Some only affect certain platforms. |
2ae324a7 |
790 | The following new warnings and errors outline these. |
774d564b |
791 | These messages are classified as follows (listed in |
792 | increasing order of desperation): |
793 | |
794 | (W) A warning (optional). |
795 | (D) A deprecation (optional). |
796 | (S) A severe warning (mandatory). |
797 | (F) A fatal error (trappable). |
798 | (P) An internal error you should never see (trappable). |
799 | (X) A very fatal error (non-trappable). |
800 | (A) An alien error message (not generated by Perl). |
5f05dabc |
801 | |
0a753a76 |
802 | =over |
5f05dabc |
803 | |
804 | =item "my" variable %s masks earlier declaration in same scope |
805 | |
806 | (S) A lexical variable has been redeclared in the same scope, effectively |
807 | eliminating all access to the previous instance. This is almost always |
808 | a typographical error. Note that the earlier variable will still exist |
809 | until the end of the scope or until all closure referents to it are |
810 | destroyed. |
811 | |
774d564b |
812 | =item %s argument is not a HASH element or slice |
813 | |
814 | (F) The argument to delete() must be either a hash element, such as |
815 | |
816 | $foo{$bar} |
817 | $ref->[12]->{"susie"} |
818 | |
819 | or a hash slice, such as |
820 | |
821 | @foo{$bar, $baz, $xyzzy} |
822 | @{$ref->[12]}{"susie", "queue"} |
823 | |
5f05dabc |
824 | =item Allocation too large: %lx |
825 | |
826 | (X) You can't allocate more than 64K on an MSDOS machine. |
827 | |
828 | =item Allocation too large |
829 | |
830 | (F) You can't allocate more than 2^31+"small amount" bytes. |
831 | |
832 | =item Attempt to free non-existent shared string |
833 | |
834 | (P) Perl maintains a reference counted internal table of strings to |
835 | optimize the storage and access of hash keys and other strings. This |
836 | indicates someone tried to decrement the reference count of a string |
837 | that can no longer be found in the table. |
838 | |
839 | =item Attempt to use reference as lvalue in substr |
840 | |
841 | (W) You supplied a reference as the first argument to substr() used |
842 | as an lvalue, which is pretty strange. Perhaps you forgot to |
843 | dereference it first. See L<perlfunc/substr>. |
844 | |
845 | =item Unsupported function fork |
846 | |
847 | (F) Your version of executable does not support forking. |
848 | |
849 | Note that under some systems, like OS/2, there may be different flavors of |
850 | Perl executables, some of which may support fork, some not. Try changing |
851 | the name you call Perl by to C<perl_>, C<perl__>, and so on. |
852 | |
853 | =item Ill-formed logical name |%s| in prime_env_iter |
854 | |
855 | (W) A warning peculiar to VMS. A logical name was encountered when preparing |
856 | to iterate over %ENV which violates the syntactic rules governing logical |
857 | names. Since it cannot be translated normally, it is skipped, and will not |
858 | appear in %ENV. This may be a benign occurrence, as some software packages |
859 | might directly modify logical name tables and introduce non-standard names, |
860 | or it may indicate that a logical name table has been corrupted. |
861 | |
774d564b |
862 | =item Can't use bareword ("%s") as %s ref while "strict refs" in use |
863 | |
864 | (F) Only hard references are allowed by "strict refs". Symbolic references |
865 | are disallowed. See L<perlref>. |
866 | |
867 | =item Constant subroutine %s redefined |
868 | |
869 | (S) You redefined a subroutine which had previously been eligible for |
870 | inlining. See L<perlsub/"Constant Functions"> for commentary and |
871 | workarounds. |
872 | |
873 | =item Died |
874 | |
875 | (F) You passed die() an empty string (the equivalent of C<die "">) or |
876 | you called it with no args and both C<$@> and C<$_> were empty. |
877 | |
5f05dabc |
878 | =item Integer overflow in hex number |
879 | |
880 | (S) The literal hex number you have specified is too big for your |
881 | architecture. On a 32-bit architecture the largest hex literal is |
882 | 0xFFFFFFFF. |
883 | |
884 | =item Integer overflow in octal number |
885 | |
886 | (S) The literal octal number you have specified is too big for your |
887 | architecture. On a 32-bit architecture the largest octal literal is |
888 | 037777777777. |
889 | |
774d564b |
890 | =item Name "%s::%s" used only once: possible typo |
891 | |
892 | (W) Typographical errors often show up as unique variable names. |
893 | If you had a good reason for having a unique name, then just mention |
894 | it again somehow to suppress the message (the C<use vars> pragma is |
895 | provided for just this purpose). |
896 | |
5f05dabc |
897 | =item Null picture in formline |
898 | |
899 | (F) The first argument to formline must be a valid format picture |
900 | specification. It was found to be empty, which probably means you |
901 | supplied it an uninitialized value. See L<perlform>. |
902 | |
903 | =item Offset outside string |
904 | |
905 | (F) You tried to do a read/write/send/recv operation with an offset |
906 | pointing outside the buffer. This is difficult to imagine. |
907 | The sole exception to this is that C<sysread()>ing past the buffer |
908 | will extend the buffer and zero pad the new area. |
909 | |
774d564b |
910 | =item Stub found while resolving method `%s' overloading `%s' in package `%s' |
911 | |
912 | (P) Overloading resolution over @ISA tree may be broken by importing stubs. |
913 | Stubs should never be implicitely created, but explicit calls to C<can> |
914 | may break this. |
915 | |
916 | =item Cannot resolve method `%s' overloading `%s' in package `s' |
917 | |
918 | (P) Internal error trying to resolve overloading specified by a method |
919 | name (as opposed to a subroutine reference). |
920 | |
5f05dabc |
921 | =item Out of memory! |
922 | |
923 | (X|F) The malloc() function returned 0, indicating there was insufficient |
924 | remaining memory (or virtual memory) to satisfy the request. |
925 | |
926 | The request was judged to be small, so the possibility to trap it |
927 | depends on the way Perl was compiled. By default it is not trappable. |
928 | However, if compiled for this, Perl may use the contents of C<$^M> as |
929 | an emergency pool after die()ing with this message. In this case the |
930 | error is trappable I<once>. |
931 | |
932 | =item Out of memory during request for %s |
933 | |
934 | (F) The malloc() function returned 0, indicating there was insufficient |
935 | remaining memory (or virtual memory) to satisfy the request. However, |
936 | the request was judged large enough (compile-time default is 64K), so |
937 | a possibility to shut down by trapping this error is granted. |
938 | |
939 | =item Possible attempt to put comments in qw() list |
940 | |
774d564b |
941 | (W) qw() lists contain items separated by whitespace; as with literal |
942 | strings, comment characters are not ignored, but are instead treated |
943 | as literal data. (You may have used different delimiters than the |
944 | exclamation marks parentheses shown here; braces are also frequently |
945 | used.) |
946 | |
947 | You probably wrote something like this: |
5f05dabc |
948 | |
2ae324a7 |
949 | @list = qw( |
774d564b |
950 | a # a comment |
5f05dabc |
951 | b # another comment |
774d564b |
952 | ); |
5f05dabc |
953 | |
954 | when you should have written this: |
955 | |
774d564b |
956 | @list = qw( |
2ae324a7 |
957 | a |
5f05dabc |
958 | b |
774d564b |
959 | ); |
960 | |
961 | If you really want comments, build your list the |
962 | old-fashioned way, with quotes and commas: |
963 | |
964 | @list = ( |
965 | 'a', # a comment |
966 | 'b', # another comment |
967 | ); |
5f05dabc |
968 | |
969 | =item Possible attempt to separate words with commas |
970 | |
774d564b |
971 | (W) qw() lists contain items separated by whitespace; therefore commas |
972 | aren't needed to separate the items. (You may have used different |
973 | delimiters than the parentheses shown here; braces are also frequently |
974 | used.) |
5f05dabc |
975 | |
2ae324a7 |
976 | You probably wrote something like this: |
5f05dabc |
977 | |
774d564b |
978 | qw! a, b, c !; |
979 | |
980 | which puts literal commas into some of the list items. Write it without |
981 | commas if you don't want them to appear in your data: |
982 | |
983 | qw! a b c !; |
5f05dabc |
984 | |
774d564b |
985 | =item Scalar value @%s{%s} better written as $%s{%s} |
986 | |
987 | (W) You've used a hash slice (indicated by @) to select a single element of |
988 | a hash. Generally it's better to ask for a scalar value (indicated by $). |
989 | The difference is that C<$foo{&bar}> always behaves like a scalar, both when |
990 | assigning to it and when evaluating its argument, while C<@foo{&bar}> behaves |
991 | like a list when you assign to it, and provides a list context to its |
992 | subscript, which can do weird things if you're expecting only one subscript. |
5f05dabc |
993 | |
994 | =item untie attempted while %d inner references still exist |
995 | |
996 | (W) A copy of the object returned from C<tie> (or C<tied>) was still |
997 | valid when C<untie> was called. |
998 | |
774d564b |
999 | =item Value of %s construct can be "0"; test with defined() |
1000 | |
1001 | (W) In a conditional expression, you used <HANDLE>, <*> (glob), or |
1002 | C<readdir> as a boolean value. Each of these constructs can return a |
1003 | value of "0"; that would make the conditional expression false, which |
1004 | is probably not what you intended. When using these constructs in |
1005 | conditional expressions, test their values with the C<defined> operator. |
1006 | |
1007 | =item Variable "%s" may be unavailable |
1008 | |
1009 | (W) An inner (nested) I<anonymous> subroutine is inside a I<named> |
1010 | subroutine, and outside that is another subroutine; and the anonymous |
1011 | (innermost) subroutine is referencing a lexical variable defined in |
1012 | the outermost subroutine. For example: |
1013 | |
1014 | sub outermost { my $a; sub middle { sub { $a } } } |
1015 | |
1016 | If the anonymous subroutine is called or referenced (directly or |
1017 | indirectly) from the outermost subroutine, it will share the variable |
1018 | as you would expect. But if the anonymous subroutine is called or |
1019 | referenced when the outermost subroutine is not active, it will see |
1020 | the value of the shared variable as it was before and during the |
1021 | *first* call to the outermost subroutine, which is probably not what |
1022 | you want. |
1023 | |
1024 | In these circumstances, it is usually best to make the middle |
1025 | subroutine anonymous, using the C<sub {}> syntax. Perl has specific |
1026 | support for shared variables in nested anonymous subroutines; a named |
1027 | subroutine in between interferes with this feature. |
1028 | |
1029 | =item Variable "%s" will not stay shared |
1030 | |
1031 | (W) An inner (nested) I<named> subroutine is referencing a lexical |
1032 | variable defined in an outer subroutine. |
1033 | |
1034 | When the inner subroutine is called, it will probably see the value of |
1035 | the outer subroutine's variable as it was before and during the |
1036 | *first* call to the outer subroutine; in this case, after the first |
1037 | call to the outer subroutine is complete, the inner and outer |
1038 | subroutines will no longer share a common value for the variable. In |
1039 | other words, the variable will no longer be shared. |
1040 | |
1041 | Furthermore, if the outer subroutine is anonymous and references a |
1042 | lexical variable outside itself, then the outer and inner subroutines |
1043 | will I<never> share the given variable. |
1044 | |
1045 | This problem can usually be solved by making the inner subroutine |
1046 | anonymous, using the C<sub {}> syntax. When inner anonymous subs that |
1047 | reference variables in outer subroutines are called or referenced, |
1048 | they are automatically re-bound to the current values of such |
1049 | variables. |
1050 | |
1051 | =item Warning: something's wrong |
1052 | |
1053 | (W) You passed warn() an empty string (the equivalent of C<warn "">) or |
1054 | you called it with no args and C<$_> was empty. |
1055 | |
1056 | =item Got an error from DosAllocMem |
5f05dabc |
1057 | |
774d564b |
1058 | (P) An error peculiar to OS/2. Most probably you're using an obsolete |
1059 | version of Perl, and this should not happen anyway. |
5f05dabc |
1060 | |
1061 | =item Malformed PERLLIB_PREFIX |
1062 | |
1063 | (F) An error peculiar to OS/2. PERLLIB_PREFIX should be of the form |
1064 | |
1065 | prefix1;prefix2 |
1066 | |
1067 | or |
1068 | |
1069 | prefix1 prefix2 |
1070 | |
1071 | with non-empty prefix1 and prefix2. If C<prefix1> is indeed a prefix of |
1072 | a builtin library search path, prefix2 is substituted. The error may appear |
1073 | if components are not found, or are too long. See L<perlos2/"PERLLIB_PREFIX">. |
1074 | |
1075 | =item PERL_SH_DIR too long |
1076 | |
1077 | (F) An error peculiar to OS/2. PERL_SH_DIR is the directory to find the |
1078 | C<sh>-shell in. See L<perlos2/"PERL_SH_DIR">. |
1079 | |
1080 | =item Process terminated by SIG%s |
1081 | |
1082 | (W) This is a standard message issued by OS/2 applications, while *nix |
1083 | applications die in silence. It is considered a feature of the OS/2 |
1084 | port. One can easily disable this by appropriate sighandlers, see |
1085 | L<perlipc/"Signals">. See L<perlos2/"Process terminated by SIGTERM/SIGINT">. |
1086 | |
1087 | =back |
1088 | |
1089 | =head1 BUGS |
1090 | |
774d564b |
1091 | If you find what you think is a bug, you might check the headers of |
1092 | recently posted articles in the comp.lang.perl.misc newsgroup. |
1093 | There may also be information at http://www.perl.com/perl/, the Perl |
1094 | Home Page. |
5f05dabc |
1095 | |
1096 | If you believe you have an unreported bug, please run the B<perlbug> |
9607fc9c |
1097 | program included with your release. Make sure you trim your bug down |
1098 | to a tiny but sufficient test case. Your bug report, along with the |
1099 | output of C<perl -V>, will be sent off to <F<perlbug@perl.com>> to be |
1100 | analysed by the Perl porting team. |
5f05dabc |
1101 | |
1102 | =head1 SEE ALSO |
1103 | |
1104 | The F<Changes> file for exhaustive details on what changed. |
1105 | |
1106 | The F<INSTALL> file for how to build Perl. This file has been |
1107 | significantly updated for 5.004, so even veteran users should |
1108 | look through it. |
1109 | |
1110 | The F<README> file for general stuff. |
1111 | |
1112 | The F<Copying> file for copyright information. |
1113 | |
1114 | =head1 HISTORY |
1115 | |
1116 | Constructed by Tom Christiansen, grabbing material with permission |
1117 | from innumerable contributors, with kibitzing by more than a few Perl |
1118 | porters. |
1119 | |
2ae324a7 |
1120 | Last update: Sat Mar 8 19:51:26 EST 1997 |