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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 | |
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21 | =head2 Compilation option: Binary compatibility with 5.003 |
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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 $PERL5OPT environment variable |
31 | |
32 | You may now put Perl options in the $PERL5OPT environment variable. |
33 | Unless Perl is running with taint checks, it will interpret this |
34 | variable as if its contents had appeared on a "#!perl" line at the |
35 | beginning of your script, except that hyphens are optional. PERL5OPT |
36 | may only be used to set the following switches: B<-[DIMUdmw]>. |
37 | |
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38 | =head2 Limitations on B<-M>, and C<-m>, and B<-T> options |
39 | |
40 | The C<-M> and C<-m> options are no longer allowed on the C<#!> line of |
41 | a script. If a script needs a module, it should invoke it with the |
42 | C<use> pragma. |
43 | |
44 | The B<-T> option is also forbidden on the C<#!> line of a script, |
45 | unless it was present on the Perl command line. Due to the way C<#!> |
46 | works, this usually means that B<-T> must be in the first argument. |
47 | Thus: |
48 | |
49 | #!/usr/bin/perl -T -w |
50 | |
51 | will probably work for an executable script invoked as C<scriptname>, |
52 | while: |
53 | |
54 | #!/usr/bin/perl -w -T |
55 | |
56 | will probably fail under the same conditions. (Non-Unix systems will |
57 | probably not follow this rule.) But C<perl scriptname> is guaranteed |
58 | to fail, since then there is no chance of B<-T> being found on the |
59 | command line before it is found on the C<#!> line. |
60 | |
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61 | =head2 More precise warnings |
62 | |
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63 | If you removed the B<-w> option from your Perl 5.003 scripts because it |
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64 | made Perl too verbose, we recommend that you try putting it back when |
65 | you upgrade to Perl 5.004. Each new perl version tends to remove some |
66 | undesirable warnings, while adding new warnings that may catch bugs in |
67 | your scripts. |
68 | |
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69 | =head2 Deprecated: Inherited C<AUTOLOAD> for non-methods |
70 | |
71 | Before Perl 5.004, C<AUTOLOAD> functions were looked up as methods |
72 | (using the C<@ISA> hierarchy), even when the function to be autoloaded |
73 | was called as a plain function (e.g. C<Foo::bar()>), not a method |
74 | (e.g. C<Foo->bar()> or C<$obj->bar()>). |
75 | |
76 | Perl 5.005 will use method lookup only for methods' C<AUTOLOAD>s. |
77 | However, there is a significant base of existing code that may be using |
78 | the old behavior. So, as an interim step, Perl 5.004 issues an optional |
79 | warning when a non-method uses an inherited C<AUTOLOAD>. |
80 | |
81 | The simple rule is: Inheritance will not work when autoloading |
82 | non-methods. The simple fix for old code is: In any module that used to |
83 | depend on inheriting C<AUTOLOAD> for non-methods from a base class named |
84 | C<BaseClass>, execute C<*AUTOLOAD = \&BaseClass::AUTOLOAD> during startup. |
85 | |
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86 | =head2 Subroutine arguments created only when they're modified |
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87 | |
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88 | In Perl 5.004, nonexistent array and hash elements used as subroutine |
89 | parameters are brought into existence only if they are actually |
90 | assigned to (via C<@_>). |
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91 | |
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92 | Earlier versions of Perl vary in their handling of such arguments. |
93 | Perl versions 5.002 and 5.003 always brought them into existence. |
94 | Perl versions 5.000, 5.001, and 5.002 brought them into existence only |
95 | if they were not the first argument (which was almost certainly a |
96 | bug). Earlier versions of Perl never brought them into existence. |
97 | |
98 | For example, given this code: |
99 | |
100 | undef @a; undef %a; |
101 | sub show { print $_[0] }; |
102 | sub change { $_[0]++ }; |
103 | show($a[2]); |
104 | change($a{b}); |
105 | |
106 | After this code executes in Perl 5.004, $a{b} exists but $a[2] does |
107 | not. In Perl 5.002 and 5.003, both $a{b} and $a[2] would have existed |
108 | (but $a[2]'s value would have been undefined). |
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109 | |
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110 | =head2 Group vector changeable with C<$)> |
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111 | |
112 | The C<$)> special variable has always (well, in Perl 5, at least) |
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113 | reflected not only the current effective group, but also the group list |
114 | as returned by the C<getgroups()> C function (if there is one). |
115 | However, until this release, there has not been a way to call the |
116 | C<setgroups()> C function from Perl. |
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117 | |
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118 | In Perl 5.004, assigning to C<$)> is exactly symmetrical with examining |
119 | it: The first number in its string value is used as the effective gid; |
120 | if there are any numbers after the first one, they are passed to the |
121 | C<setgroups()> C function (if there is one). |
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122 | |
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123 | =head2 Fixed parsing of $$<digit>, &$<digit>, etc. |
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124 | |
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125 | Perl versions before 5.004 misinterpreted any type marker followed by |
126 | "$" and a digit. For example, "$$0" was incorrectly taken to mean |
127 | "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004. |
128 | |
129 | However, the developers of Perl 5.004 could not fix this bug completely, |
130 | because at least two widely-used modules depend on the old meaning of |
131 | "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the |
132 | old (broken) way inside strings; but it generates this message as a |
133 | warning. And in Perl 5.005, this special treatment will cease. |
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134 | |
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135 | =head2 No resetting of $. on implicit close |
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136 | |
137 | The documentation for Perl 5.0 has always stated that C<$.> is I<not> |
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138 | reset when an already-open file handle is reopened with no intervening |
139 | call to C<close>. Due to a bug, perl versions 5.000 through 5.003 |
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140 | I<did> reset C<$.> under that circumstance; Perl 5.004 does not. |
141 | |
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142 | =head2 C<wantarray> may return undef |
143 | |
144 | The C<wantarray> operator returns true if a subroutine is expected to |
145 | return a list, and false otherwise. In Perl 5.004, C<wantarray> can |
146 | also return the undefined value if a subroutine's return value will |
147 | not be used at all, which allows subroutines to avoid a time-consuming |
148 | calculation of a return value if it isn't going to be used. |
149 | |
150 | =head2 Changes to tainting checks |
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151 | |
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152 | A bug in previous versions may have failed to detect some insecure |
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153 | conditions when taint checks are turned on. (Taint checks are used |
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154 | in setuid or setgid scripts, or when explicitly turned on with the |
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155 | C<-T> invocation option.) Although it's unlikely, this may cause a |
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156 | previously-working script to now fail -- which should be construed |
157 | as a blessing, since that indicates a potentially-serious security |
158 | hole was just plugged. |
159 | |
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160 | =head2 New Opcode module and revised Safe module |
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161 | |
162 | A new Opcode module supports the creation, manipulation and |
163 | application of opcode masks. The revised Safe module has a new API |
164 | and is implemented using the new Opcode module. Please read the new |
165 | Opcode and Safe documentation. |
166 | |
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167 | =head2 Embedding improvements |
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168 | |
169 | In older versions of Perl it was not possible to create more than one |
170 | Perl interpreter instance inside a single process without leaking like a |
171 | sieve and/or crashing. The bugs that caused this behavior have all been |
172 | fixed. However, you still must take care when embedding Perl in a C |
173 | program. See the updated perlembed manpage for tips on how to manage |
174 | your interpreters. |
175 | |
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176 | =head2 Internal change: FileHandle class based on IO::* classes |
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177 | |
178 | File handles are now stored internally as type IO::Handle. The |
179 | FileHandle module is still supported for backwards compatibility, but |
180 | it is now merely a front end to the IO::* modules -- specifically, |
181 | IO::Handle, IO::Seekable, and IO::File. We suggest, but do not |
182 | require, that you use the IO::* modules in new code. |
183 | |
184 | In harmony with this change, C<*GLOB{FILEHANDLE}> is now a |
185 | backward-compatible synonym for C<*STDOUT{IO}>. |
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186 | |
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187 | =head2 Internal change: PerlIO abstraction interface |
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188 | |
189 | It is now possible to build Perl with AT&T's sfio IO package |
190 | instead of stdio. See L<perlapio> for more details, and |
191 | the F<INSTALL> file for how to use it. |
192 | |
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193 | =head2 New and changed builtin variables |
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194 | |
195 | =over |
196 | |
197 | =item $^E |
198 | |
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199 | Extended error message on some platforms. (Also known as |
200 | $EXTENDED_OS_ERROR if you C<use English>). |
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201 | |
202 | =item $^H |
203 | |
204 | The current set of syntax checks enabled by C<use strict>. See the |
205 | documentation of C<strict> for more details. Not actually new, but |
206 | newly documented. |
207 | Because it is intended for internal use by Perl core components, |
208 | there is no C<use English> long name for this variable. |
209 | |
210 | =item $^M |
211 | |
212 | By default, running out of memory it is not trappable. However, if |
213 | compiled for this, Perl may use the contents of C<$^M> as an emergency |
214 | pool after die()ing with this message. Suppose that your Perl were |
215 | compiled with -DEMERGENCY_SBRK and used Perl's malloc. Then |
216 | |
217 | $^M = 'a' x (1<<16); |
218 | |
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219 | would allocate a 64K buffer for use when in emergency. |
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220 | See the F<INSTALL> file for information on how to enable this option. |
221 | As a disincentive to casual use of this advanced feature, |
222 | there is no C<use English> long name for this variable. |
223 | |
224 | =back |
225 | |
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226 | =head2 New and changed builtin functions |
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227 | |
228 | =over |
229 | |
230 | =item delete on slices |
231 | |
232 | This now works. (e.g. C<delete @ENV{'PATH', 'MANPATH'}>) |
233 | |
234 | =item flock |
235 | |
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236 | is now supported on more platforms, prefers fcntl to lockf when |
237 | emulating, and always flushes before (un)locking. |
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238 | |
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239 | =item printf and sprintf |
240 | |
241 | now support "%i" as a synonym for "%d", and the "h" modifier. |
242 | So "%hi" means "short integer in decimal", and "%ho" means |
243 | "unsigned short integer as octal". |
244 | |
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245 | =item keys as an lvalue |
246 | |
247 | As an lvalue, C<keys> allows you to increase the number of hash buckets |
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248 | allocated for the given hash. This can gain you a measure of efficiency if |
249 | you know the hash is going to get big. (This is similar to pre-extending |
250 | an array by assigning a larger number to $#array.) If you say |
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251 | |
252 | keys %hash = 200; |
253 | |
254 | then C<%hash> will have at least 200 buckets allocated for it. These |
255 | buckets will be retained even if you do C<%hash = ()>; use C<undef |
256 | %hash> if you want to free the storage while C<%hash> is still in scope. |
257 | You can't shrink the number of buckets allocated for the hash using |
258 | C<keys> in this way (but you needn't worry about doing this by accident, |
259 | as trying has no effect). |
260 | |
261 | =item my() in Control Structures |
262 | |
263 | You can now use my() (with or without the parentheses) in the control |
264 | expressions of control structures such as: |
265 | |
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266 | while (defined(my $line = <>)) { |
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267 | $line = lc $line; |
268 | } continue { |
269 | print $line; |
270 | } |
271 | |
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272 | if ((my $answer = <STDIN>) =~ /^y(es)?$/i) { |
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273 | user_agrees(); |
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274 | } elsif ($answer =~ /^n(o)?$/i) { |
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275 | user_disagrees(); |
276 | } else { |
277 | chomp $answer; |
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278 | die "`$answer' is neither `yes' nor `no'"; |
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279 | } |
280 | |
281 | Also, you can declare a foreach loop control variable as lexical by |
282 | preceding it with the word "my". For example, in: |
283 | |
284 | foreach my $i (1, 2, 3) { |
285 | some_function(); |
286 | } |
287 | |
288 | $i is a lexical variable, and the scope of $i extends to the end of |
289 | the loop, but not beyond it. |
290 | |
291 | Note that you still cannot use my() on global punctuation variables |
292 | such as $_ and the like. |
293 | |
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294 | =item pack() and unpack() |
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295 | |
296 | A new format 'w' represents a BER compressed integer (as defined in |
297 | ASN.1). Its format is a sequence of one or more bytes, each of which |
298 | provides seven bits of the total value, with the most significant |
299 | first. Bit eight of each byte is set, except for the last byte, in |
300 | which bit eight is clear. |
301 | |
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302 | Both pack() and unpack() now fail when their templates contain invalid |
303 | types. (Invalid types used to be ignored.) |
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304 | |
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305 | =item sysseek() |
306 | |
307 | The new sysseek() operator is a variant of seek() that sets and gets the |
308 | file's system read/write position, using the lseek(2) system call. It is |
309 | the only reliable way to seek before using sysread() or syswrite(). Its |
310 | return value is the new position, or the undefined value on failure. |
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311 | |
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312 | =item use VERSION |
313 | |
314 | If the first argument to C<use> is a number, it is treated as a version |
315 | number instead of a module name. If the version of the Perl interpreter |
316 | is less than VERSION, then an error message is printed and Perl exits |
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317 | immediately. Because C<use> occurs at compile time, this check happens |
318 | immediately during the compilation process, unlike C<require VERSION>, |
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319 | which waits until runtime for the check. This is often useful if you |
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320 | need to check the current Perl version before C<use>ing library modules |
321 | which have changed in incompatible ways from older versions of Perl. |
322 | (We try not to do this more than we have to.) |
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323 | |
324 | =item use Module VERSION LIST |
325 | |
326 | If the VERSION argument is present between Module and LIST, then the |
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327 | C<use> will call the VERSION method in class Module with the given |
328 | version as an argument. The default VERSION method, inherited from |
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329 | the UNIVERSAL class, croaks if the given version is larger than the |
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330 | value of the variable $Module::VERSION. (Note that there is not a |
331 | comma after VERSION!) |
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332 | |
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333 | This version-checking mechanism is similar to the one currently used |
334 | in the Exporter module, but it is faster and can be used with modules |
335 | that don't use the Exporter. It is the recommended method for new |
336 | code. |
337 | |
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338 | =item prototype(FUNCTION) |
339 | |
340 | Returns the prototype of a function as a string (or C<undef> if the |
341 | function has no prototype). FUNCTION is a reference to or the name of the |
342 | function whose prototype you want to retrieve. |
343 | (Not actually new; just never documented before.) |
344 | |
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345 | =item srand |
346 | |
347 | The default seed for C<srand>, which used to be C<time>, has been changed. |
348 | Now it's a heady mix of difficult-to-predict system-dependent values, |
349 | which should be sufficient for most everyday purposes. |
350 | |
351 | Previous to version 5.004, calling C<rand> without first calling C<srand> |
352 | would yield the same sequence of random numbers on most or all machines. |
353 | Now, when perl sees that you're calling C<rand> and haven't yet called |
354 | C<srand>, it calls C<srand> with the default seed. You should still call |
355 | C<srand> manually if your code might ever be run on a pre-5.004 system, |
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356 | of course, or if you want a seed other than the default. |
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357 | |
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358 | =item $_ as Default |
359 | |
360 | Functions documented in the Camel to default to $_ now in |
361 | fact do, and all those that do are so documented in L<perlfunc>. |
362 | |
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363 | =item C<m//g> does not reset search position on failure |
364 | |
365 | The C<m//g> match iteration construct used to reset its target string's |
366 | search position (which is visible through the C<pos> operator) when a |
367 | match failed; as a result, the next C<m//g> match would start at the |
368 | beginning of the string). With Perl 5.004, the search position must be |
369 | reset explicitly, as with C<pos $str = 0;>, or by modifying the target |
370 | string. This change in Perl makes it possible to chain matches together |
371 | in conjunction with the C<\G> zero-width assertion. See L<perlop> and |
372 | L<perlre>. |
373 | |
374 | Here is an illustration of what it takes to get the old behavior: |
375 | |
376 | for ( qw(this and that are not what you think you got) ) { |
377 | while ( /(\w*t\w*)/g ) { print "t word is: $1\n" } |
378 | pos = 0; # REQUIRED FOR 5.004 |
379 | while ( /(\w*a\w*)/g ) { print "a word is: $1\n" } |
380 | print "\n"; |
381 | } |
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382 | |
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383 | =item C<m//x> ignores whitespace before ?*+{} |
384 | |
385 | The C<m//x> construct has always been intended to ignore all unescaped |
386 | whitespace. However, before Perl 5.004, whitespace had the effect of |
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387 | escaping repeat modifiers like "*" or "?"; for example, C</a *b/x> was |
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388 | (mis)interpreted as C</a\*b/x>. This bug has been fixed in 5.004. |
389 | |
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390 | =item nested C<sub{}> closures work now |
391 | |
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392 | Prior to the 5.004 release, nested anonymous functions didn't work |
393 | right. They do now. |
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394 | |
395 | =item formats work right on changing lexicals |
396 | |
397 | Just like anonymous functions that contain lexical variables |
398 | that change (like a lexical index variable for a C<foreach> loop), |
399 | formats now work properly. For example, this silently failed |
400 | before, and is fine now: |
401 | |
402 | my $i; |
403 | foreach $i ( 1 .. 10 ) { |
404 | format = |
405 | my i is @# |
406 | $i |
407 | . |
408 | write; |
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409 | } |
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410 | |
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411 | =back |
412 | |
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413 | =head2 New builtin methods |
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414 | |
415 | The C<UNIVERSAL> package automatically contains the following methods that |
416 | are inherited by all other classes: |
417 | |
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418 | =over |
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419 | |
420 | =item isa(CLASS) |
421 | |
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422 | C<isa> returns I<true> if its object is blessed into a subclass of C<CLASS> |
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423 | |
424 | C<isa> is also exportable and can be called as a sub with two arguments. This |
425 | allows the ability to check what a reference points to. Example: |
426 | |
427 | use UNIVERSAL qw(isa); |
428 | |
429 | if(isa($ref, 'ARRAY')) { |
430 | ... |
431 | } |
432 | |
433 | =item can(METHOD) |
434 | |
435 | C<can> checks to see if its object has a method called C<METHOD>, |
436 | if it does then a reference to the sub is returned; if it does not then |
437 | I<undef> is returned. |
438 | |
439 | =item VERSION( [NEED] ) |
440 | |
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441 | C<VERSION> returns the version number of the class (package). If the |
442 | NEED argument is given then it will check that the current version (as |
443 | defined by the $VERSION variable in the given package) not less than |
444 | NEED; it will die if this is not the case. This method is normally |
445 | called as a class method. This method is called automatically by the |
446 | C<VERSION> form of C<use>. |
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447 | |
448 | use A 1.2 qw(some imported subs); |
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449 | # implies: |
450 | A->VERSION(1.2); |
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451 | |
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452 | =back |
453 | |
454 | B<NOTE:> C<can> directly uses Perl's internal code for method lookup, and |
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455 | C<isa> uses a very similar method and caching strategy. This may cause |
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456 | strange effects if the Perl code dynamically changes @ISA in any package. |
457 | |
458 | You may add other methods to the UNIVERSAL class via Perl or XS code. |
459 | You do not need to C<use UNIVERSAL> in order to make these methods |
460 | available to your program. This is necessary only if you wish to |
461 | have C<isa> available as a plain subroutine in the current package. |
462 | |
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463 | =head2 TIEHANDLE now supported |
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464 | |
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465 | See L<perltie> for other kinds of tie()s. |
466 | |
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467 | =over |
468 | |
469 | =item TIEHANDLE classname, LIST |
470 | |
471 | This is the constructor for the class. That means it is expected to |
472 | return an object of some sort. The reference can be used to |
473 | hold some internal information. |
474 | |
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475 | sub TIEHANDLE { |
476 | print "<shout>\n"; |
477 | my $i; |
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478 | return bless \$i, shift; |
479 | } |
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480 | |
481 | =item PRINT this, LIST |
482 | |
483 | This method will be triggered every time the tied handle is printed to. |
484 | Beyond its self reference it also expects the list that was passed to |
485 | the print function. |
486 | |
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487 | sub PRINT { |
488 | $r = shift; |
489 | $$r++; |
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490 | return print join( $, => map {uc} @_), $\; |
491 | } |
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492 | |
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493 | =item PRINTF this, LIST |
494 | |
495 | This method will be triggered every time the tied handle is printed to |
496 | with the C<printf()> function. |
497 | Beyond its self reference it also expects the format and list that was |
498 | passed to the printf function. |
499 | |
500 | sub PRINTF { |
501 | shift; |
502 | my $fmt = shift; |
503 | print sprintf($fmt, @_)."\n"; |
504 | } |
505 | |
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506 | =item READ this LIST |
507 | |
508 | This method will be called when the handle is read from via the C<read> |
509 | or C<sysread> functions. |
510 | |
511 | sub READ { |
512 | $r = shift; |
513 | my($buf,$len,$offset) = @_; |
514 | print "READ called, \$buf=$buf, \$len=$len, \$offset=$offset"; |
515 | } |
516 | |
5f05dabc |
517 | =item READLINE this |
518 | |
519 | This method will be called when the handle is read from. The method |
520 | should return undef when there is no more data. |
521 | |
2ae324a7 |
522 | sub READLINE { |
523 | $r = shift; |
524 | return "PRINT called $$r times\n" |
774d564b |
525 | } |
5f05dabc |
526 | |
2ae324a7 |
527 | =item GETC this |
528 | |
529 | This method will be called when the C<getc> function is called. |
530 | |
531 | sub GETC { print "Don't GETC, Get Perl"; return "a"; } |
532 | |
5f05dabc |
533 | =item DESTROY this |
534 | |
535 | As with the other types of ties, this method will be called when the |
536 | tied handle is about to be destroyed. This is useful for debugging and |
537 | possibly for cleaning up. |
538 | |
2ae324a7 |
539 | sub DESTROY { |
774d564b |
540 | print "</shout>\n"; |
541 | } |
5f05dabc |
542 | |
543 | =back |
544 | |
54310121 |
545 | =head2 Malloc enhancements |
aa689395 |
546 | |
2ae324a7 |
547 | Four new compilation flags are recognized by malloc.c. (They have no |
548 | effect if perl is compiled with system malloc().) |
549 | |
550 | =over |
551 | |
552 | =item -DDEBUGGING_MSTATS |
553 | |
554 | If perl is compiled with C<DEBUGGING_MSTATS> defined, you can print |
555 | memory statistics at runtime by running Perl thusly: |
aa689395 |
556 | |
557 | env PERL_DEBUG_MSTATS=2 perl your_script_here |
558 | |
559 | The value of 2 means to print statistics after compilation and on |
560 | exit; with a value of 1, the statistics ares printed only on exit. |
561 | (If you want the statistics at an arbitrary time, you'll need to |
562 | install the optional module Devel::Peek.) |
563 | |
aa689395 |
564 | =item -DEMERGENCY_SBRK |
565 | |
566 | If this macro is defined, running out of memory need not be a fatal |
567 | error: a memory pool can allocated by assigning to the special |
568 | variable C<$^M>. See L<"$^M">. |
774d564b |
569 | |
aa689395 |
570 | =item -DPACK_MALLOC |
571 | |
572 | Perl memory allocation is by bucket with sizes close to powers of two. |
573 | Because of these malloc overhead may be big, especially for data of |
574 | size exactly a power of two. If C<PACK_MALLOC> is defined, perl uses |
575 | a slightly different algorithm for small allocations (up to 64 bytes |
576 | long), which makes it possible to have overhead down to 1 byte for |
577 | allocations which are powers of two (and appear quite often). |
578 | |
579 | Expected memory savings (with 8-byte alignment in C<alignbytes>) is |
580 | about 20% for typical Perl usage. Expected slowdown due to additional |
581 | malloc overhead is in fractions of a percent (hard to measure, because |
582 | of the effect of saved memory on speed). |
583 | |
584 | =item -DTWO_POT_OPTIMIZE |
585 | |
586 | Similarly to C<PACK_MALLOC>, this macro improves allocations of data |
587 | with size close to a power of two; but this works for big allocations |
588 | (starting with 16K by default). Such allocations are typical for big |
589 | hashes and special-purpose scripts, especially image processing. |
590 | |
591 | On recent systems, the fact that perl requires 2M from system for 1M |
592 | allocation will not affect speed of execution, since the tail of such |
593 | a chunk is not going to be touched (and thus will not require real |
594 | memory). However, it may result in a premature out-of-memory error. |
595 | So if you will be manipulating very large blocks with sizes close to |
596 | powers of two, it would be wise to define this macro. |
597 | |
598 | Expected saving of memory is 0-100% (100% in applications which |
599 | require most memory in such 2**n chunks); expected slowdown is |
600 | negligible. |
601 | |
602 | =back |
603 | |
54310121 |
604 | =head2 Miscellaneous efficiency enhancements |
774d564b |
605 | |
606 | Functions that have an empty prototype and that do nothing but return |
607 | a fixed value are now inlined (e.g. C<sub PI () { 3.14159 }>). |
608 | |
aa689395 |
609 | Each unique hash key is only allocated once, no matter how many hashes |
610 | have an entry with that key. So even if you have 100 copies of the |
68dc0745 |
611 | same hash, the hash keys never have to be reallocated. |
aa689395 |
612 | |
5f05dabc |
613 | =head1 Pragmata |
614 | |
54310121 |
615 | Six new pragmatic modules exist: |
5f05dabc |
616 | |
617 | =over |
618 | |
54310121 |
619 | =item use autouse MODULE => qw(sub1 sub2 sub3) |
620 | |
621 | Defers C<require MODULE> until someone calls one of the specified |
622 | subroutines (which must be exported by MODULE). This pragma should be |
623 | used with caution, and only when necessary. |
624 | |
5f05dabc |
625 | =item use blib |
626 | |
774d564b |
627 | =item use blib 'dir' |
628 | |
5f05dabc |
629 | Looks for MakeMaker-like I<'blib'> directory structure starting in |
630 | I<dir> (or current directory) and working back up to five levels of |
631 | parent directories. |
632 | |
633 | Intended for use on command line with B<-M> option as a way of testing |
634 | arbitrary scripts against an uninstalled version of a package. |
635 | |
54310121 |
636 | =item use constant NAME => VALUE |
637 | |
638 | Provides a convenient interface for creating compile-time constants, |
639 | See L<perlsub/"Constant Functions">. |
640 | |
5f05dabc |
641 | =item use locale |
642 | |
643 | Tells the compiler to enable (or disable) the use of POSIX locales for |
54310121 |
644 | builtin operations. |
5f05dabc |
645 | |
646 | When C<use locale> is in effect, the current LC_CTYPE locale is used |
647 | for regular expressions and case mapping; LC_COLLATE for string |
648 | ordering; and LC_NUMERIC for numeric formating in printf and sprintf |
649 | (but B<not> in print). LC_NUMERIC is always used in write, since |
650 | lexical scoping of formats is problematic at best. |
651 | |
652 | Each C<use locale> or C<no locale> affects statements to the end of |
653 | the enclosing BLOCK or, if not inside a BLOCK, to the end of the |
654 | current file. Locales can be switched and queried with |
655 | POSIX::setlocale(). |
656 | |
657 | See L<perllocale> for more information. |
658 | |
659 | =item use ops |
660 | |
7cfe7857 |
661 | Disable unsafe opcodes, or any named opcodes, when compiling Perl code. |
5f05dabc |
662 | |
ff0cee69 |
663 | =item use vmsish |
664 | |
665 | Enable VMS-specific language features. Currently, there are three |
aa689395 |
666 | VMS-specific features available: 'status', which makes C<$?> and |
ff0cee69 |
667 | C<system> return genuine VMS status values instead of emulating POSIX; |
668 | 'exit', which makes C<exit> take a genuine VMS status value instead of |
669 | assuming that C<exit 1> is an error; and 'time', which makes all times |
670 | relative to the local time zone, in the VMS tradition. |
671 | |
5f05dabc |
672 | =back |
673 | |
674 | =head1 Modules |
675 | |
5cd24f17 |
676 | =head2 Required Updates |
677 | |
678 | Though Perl 5.004 is compatible with almost all modules that work |
679 | with Perl 5.003, there are a few exceptions: |
680 | |
681 | Module Required Version for Perl 5.004 |
682 | ------ ------------------------------- |
137443ea |
683 | Filter Filter-1.12 |
684 | LWP libwww-perl-5.08 |
5cd24f17 |
685 | Tk Tk400.202 (-w makes noise) |
686 | |
137443ea |
687 | Also, the majordomo mailing list program, version 1.94.1, doesn't work |
688 | with Perl 5.004 (nor with perl 4), because it executes an invalid |
689 | regular expression. This bug is fixed in majordomo version 1.94.2. |
690 | |
54310121 |
691 | =head2 Installation directories |
f86702cc |
692 | |
693 | The I<installperl> script now places the Perl source files for |
694 | extensions in the architecture-specific library directory, which is |
695 | where the shared libraries for extensions have always been. This |
696 | change is intended to allow administrators to keep the Perl 5.004 |
697 | library directory unchanged from a previous version, without running |
698 | the risk of binary incompatibility between extensions' Perl source and |
699 | shared libraries. |
700 | |
54310121 |
701 | =head2 Module information summary |
5f05dabc |
702 | |
774d564b |
703 | Brand new modules, arranged by topic rather than strictly |
704 | alphabetically: |
705 | |
137443ea |
706 | CGI.pm Web server interface ("Common Gateway Interface") |
707 | CGI/Apache.pm Support for Apache's Perl module |
708 | CGI/Carp.pm Log server errors with helpful context |
709 | CGI/Fast.pm Support for FastCGI (persistent server process) |
710 | CGI/Push.pm Support for server push |
711 | CGI/Switch.pm Simple interface for multiple server types |
712 | |
713 | CPAN Interface to Comprehensive Perl Archive Network |
714 | CPAN::FirstTime Utility for creating CPAN configuration file |
715 | CPAN::Nox Runs CPAN while avoiding compiled extensions |
5f05dabc |
716 | |
717 | IO.pm Top-level interface to IO::* classes |
718 | IO/File.pm IO::File extension Perl module |
719 | IO/Handle.pm IO::Handle extension Perl module |
720 | IO/Pipe.pm IO::Pipe extension Perl module |
721 | IO/Seekable.pm IO::Seekable extension Perl module |
722 | IO/Select.pm IO::Select extension Perl module |
723 | IO/Socket.pm IO::Socket extension Perl module |
724 | |
725 | Opcode.pm Disable named opcodes when compiling Perl code |
726 | |
727 | ExtUtils/Embed.pm Utilities for embedding Perl in C programs |
728 | ExtUtils/testlib.pm Fixes up @INC to use just-built extension |
729 | |
5f05dabc |
730 | FindBin.pm Find path of currently executing program |
731 | |
8cc95fdb |
732 | Class/Struct.pm Declare struct-like datatypes as Perl classes |
46fc3d4c |
733 | File/stat.pm By-name interface to Perl's builtin stat |
734 | Net/hostent.pm By-name interface to Perl's builtin gethost* |
735 | Net/netent.pm By-name interface to Perl's builtin getnet* |
736 | Net/protoent.pm By-name interface to Perl's builtin getproto* |
737 | Net/servent.pm By-name interface to Perl's builtin getserv* |
738 | Time/gmtime.pm By-name interface to Perl's builtin gmtime |
739 | Time/localtime.pm By-name interface to Perl's builtin localtime |
8cc95fdb |
740 | Time/tm.pm Internal object for Time::{gm,local}time |
46fc3d4c |
741 | User/grent.pm By-name interface to Perl's builtin getgr* |
742 | User/pwent.pm By-name interface to Perl's builtin getpw* |
5f05dabc |
743 | |
774d564b |
744 | Tie/RefHash.pm Base class for tied hashes with references as keys |
7a4c00b4 |
745 | |
5f05dabc |
746 | UNIVERSAL.pm Base class for *ALL* classes |
747 | |
54310121 |
748 | =head2 Fcntl |
749 | |
750 | New constants in the existing Fcntl modules are now supported, |
751 | provided that your operating system happens to support them: |
752 | |
753 | F_GETOWN F_SETOWN |
754 | O_ASYNC O_DEFER O_DSYNC O_FSYNC O_SYNC |
755 | O_EXLOCK O_SHLOCK |
756 | |
757 | These constants are intended for use with the Perl operators sysopen() |
758 | and fcntl() and the basic database modules like SDBM_File. For the |
759 | exact meaning of these and other Fcntl constants please refer to your |
760 | operating system's documentation for fcntl() and open(). |
761 | |
762 | In addition, the Fcntl module now provides these constants for use |
763 | with the Perl operator flock(): |
764 | |
765 | LOCK_SH LOCK_EX LOCK_NB LOCK_UN |
766 | |
767 | These constants are defined in all environments (because where there is |
768 | no flock() system call, Perl emulates it). However, for historical |
769 | reasons, these constants are not exported unless they are explicitly |
770 | requested with the ":flock" tag (e.g. C<use Fcntl ':flock'>). |
771 | |
5f05dabc |
772 | =head2 IO |
773 | |
774 | The IO module provides a simple mechanism to load all of the IO modules at one |
775 | go. Currently this includes: |
776 | |
777 | IO::Handle |
778 | IO::Seekable |
779 | IO::File |
780 | IO::Pipe |
781 | IO::Socket |
782 | |
783 | For more information on any of these modules, please see its |
784 | respective documentation. |
785 | |
786 | =head2 Math::Complex |
787 | |
788 | The Math::Complex module has been totally rewritten, and now supports |
789 | more operations. These are overloaded: |
790 | |
791 | + - * / ** <=> neg ~ abs sqrt exp log sin cos atan2 "" (stringify) |
792 | |
793 | And these functions are now exported: |
794 | |
795 | pi i Re Im arg |
5cd24f17 |
796 | log10 logn ln cbrt root |
797 | tan |
798 | csc sec cot |
799 | asin acos atan |
800 | acsc asec acot |
801 | sinh cosh tanh |
802 | csch sech coth |
803 | asinh acosh atanh |
804 | acsch asech acoth |
5f05dabc |
805 | cplx cplxe |
806 | |
5aabfad6 |
807 | =head2 Math::Trig |
808 | |
5cd24f17 |
809 | This new module provides a simpler interface to parts of Math::Complex for |
5aabfad6 |
810 | those who need trigonometric functions only for real numbers. |
811 | |
0a753a76 |
812 | =head2 DB_File |
813 | |
814 | There have been quite a few changes made to DB_File. Here are a few of |
815 | the highlights: |
816 | |
817 | =over |
818 | |
819 | =item * |
820 | |
821 | Fixed a handful of bugs. |
822 | |
823 | =item * |
824 | |
825 | By public demand, added support for the standard hash function exists(). |
826 | |
827 | =item * |
828 | |
829 | Made it compatible with Berkeley DB 1.86. |
830 | |
831 | =item * |
832 | |
833 | Made negative subscripts work with RECNO interface. |
834 | |
835 | =item * |
836 | |
837 | Changed the default flags from O_RDWR to O_CREAT|O_RDWR and the default |
838 | mode from 0640 to 0666. |
839 | |
840 | =item * |
841 | |
842 | Made DB_File automatically import the open() constants (O_RDWR, |
843 | O_CREAT etc.) from Fcntl, if available. |
844 | |
845 | =item * |
846 | |
847 | Updated documentation. |
848 | |
849 | =back |
850 | |
851 | Refer to the HISTORY section in DB_File.pm for a complete list of |
852 | changes. Everything after DB_File 1.01 has been added since 5.003. |
853 | |
854 | =head2 Net::Ping |
855 | |
856 | Major rewrite - support added for both udp echo and real icmp pings. |
857 | |
54310121 |
858 | =head2 Object-oriented overrides for builtin operators |
5f05dabc |
859 | |
54310121 |
860 | Many of the Perl builtins returning lists now have |
5f05dabc |
861 | object-oriented overrides. These are: |
862 | |
863 | File::stat |
864 | Net::hostent |
865 | Net::netent |
866 | Net::protoent |
867 | Net::servent |
868 | Time::gmtime |
869 | Time::localtime |
870 | User::grent |
871 | User::pwent |
872 | |
873 | For example, you can now say |
874 | |
875 | use File::stat; |
876 | use User::pwent; |
877 | $his = (stat($filename)->st_uid == pwent($whoever)->pw_uid); |
878 | |
774d564b |
879 | =head1 Utility Changes |
5f05dabc |
880 | |
774d564b |
881 | =head2 xsubpp |
5f05dabc |
882 | |
0a753a76 |
883 | =over |
884 | |
774d564b |
885 | =item C<void> XSUBs now default to returning nothing |
886 | |
887 | Due to a documentation/implementation bug in previous versions of |
888 | Perl, XSUBs with a return type of C<void> have actually been |
889 | returning one value. Usually that value was the GV for the XSUB, |
890 | but sometimes it was some already freed or reused value, which would |
891 | sometimes lead to program failure. |
892 | |
893 | In Perl 5.004, if an XSUB is declared as returning C<void>, it |
894 | actually returns no value, i.e. an empty list (though there is a |
895 | backward-compatibility exception; see below). If your XSUB really |
896 | does return an SV, you should give it a return type of C<SV *>. |
897 | |
898 | For backward compatibility, I<xsubpp> tries to guess whether a |
899 | C<void> XSUB is really C<void> or if it wants to return an C<SV *>. |
900 | It does so by examining the text of the XSUB: if I<xsubpp> finds |
901 | what looks like an assignment to C<ST(0)>, it assumes that the |
902 | XSUB's return type is really C<SV *>. |
5f05dabc |
903 | |
0a753a76 |
904 | =back |
905 | |
906 | =head1 C Language API Changes |
907 | |
908 | =over |
909 | |
910 | =item C<gv_fetchmethod> and C<perl_call_sv> |
911 | |
912 | The C<gv_fetchmethod> function finds a method for an object, just like |
913 | in Perl 5.003. The GV it returns may be a method cache entry. |
914 | However, in Perl 5.004, method cache entries are not visible to users; |
915 | therefore, they can no longer be passed directly to C<perl_call_sv>. |
916 | Instead, you should use the C<GvCV> macro on the GV to extract its CV, |
917 | and pass the CV to C<perl_call_sv>. |
918 | |
919 | The most likely symptom of passing the result of C<gv_fetchmethod> to |
920 | C<perl_call_sv> is Perl's producing an "Undefined subroutine called" |
921 | error on the I<second> call to a given method (since there is no cache |
922 | on the first call). |
923 | |
137443ea |
924 | =item C<perl_eval_pv> |
925 | |
8903cb82 |
926 | A new function handy for eval'ing strings of Perl code inside C code. |
137443ea |
927 | This function returns the value from the eval statement, which can |
928 | be used instead of fetching globals from the symbol table. See |
929 | L<perlguts>, L<perlembed> and L<perlcall> for details and examples. |
930 | |
1e422769 |
931 | =item Extended API for manipulating hashes |
932 | |
933 | Internal handling of hash keys has changed. The old hashtable API is |
934 | still fully supported, and will likely remain so. The additions to the |
935 | API allow passing keys as C<SV*>s, so that C<tied> hashes can be given |
54310121 |
936 | real scalars as keys rather than plain strings (nontied hashes still |
1e422769 |
937 | can only use strings as keys). New extensions must use the new hash |
938 | access functions and macros if they wish to use C<SV*> keys. These |
939 | additions also make it feasible to manipulate C<HE*>s (hash entries), |
940 | which can be more efficient. See L<perlguts> for details. |
941 | |
0a753a76 |
942 | =back |
943 | |
5f05dabc |
944 | =head1 Documentation Changes |
945 | |
946 | Many of the base and library pods were updated. These |
947 | new pods are included in section 1: |
948 | |
0a753a76 |
949 | =over |
5f05dabc |
950 | |
774d564b |
951 | =item L<perldelta> |
5f05dabc |
952 | |
71be2cbc |
953 | This document. |
5f05dabc |
954 | |
71be2cbc |
955 | =item L<perllocale> |
5f05dabc |
956 | |
71be2cbc |
957 | Locale support (internationalization and localization). |
5f05dabc |
958 | |
959 | =item L<perltoot> |
960 | |
961 | Tutorial on Perl OO programming. |
962 | |
71be2cbc |
963 | =item L<perlapio> |
964 | |
965 | Perl internal IO abstraction interface. |
966 | |
5f05dabc |
967 | =item L<perldebug> |
968 | |
969 | Although not new, this has been massively updated. |
970 | |
971 | =item L<perlsec> |
972 | |
973 | Although not new, this has been massively updated. |
974 | |
975 | =back |
976 | |
977 | =head1 New Diagnostics |
978 | |
979 | Several new conditions will trigger warnings that were |
980 | silent before. Some only affect certain platforms. |
2ae324a7 |
981 | The following new warnings and errors outline these. |
774d564b |
982 | These messages are classified as follows (listed in |
983 | increasing order of desperation): |
984 | |
985 | (W) A warning (optional). |
986 | (D) A deprecation (optional). |
987 | (S) A severe warning (mandatory). |
988 | (F) A fatal error (trappable). |
989 | (P) An internal error you should never see (trappable). |
54310121 |
990 | (X) A very fatal error (nontrappable). |
774d564b |
991 | (A) An alien error message (not generated by Perl). |
5f05dabc |
992 | |
0a753a76 |
993 | =over |
5f05dabc |
994 | |
995 | =item "my" variable %s masks earlier declaration in same scope |
996 | |
997 | (S) A lexical variable has been redeclared in the same scope, effectively |
998 | eliminating all access to the previous instance. This is almost always |
999 | a typographical error. Note that the earlier variable will still exist |
1000 | until the end of the scope or until all closure referents to it are |
1001 | destroyed. |
1002 | |
774d564b |
1003 | =item %s argument is not a HASH element or slice |
1004 | |
1005 | (F) The argument to delete() must be either a hash element, such as |
1006 | |
1007 | $foo{$bar} |
1008 | $ref->[12]->{"susie"} |
1009 | |
1010 | or a hash slice, such as |
1011 | |
1012 | @foo{$bar, $baz, $xyzzy} |
1013 | @{$ref->[12]}{"susie", "queue"} |
1014 | |
5f05dabc |
1015 | =item Allocation too large: %lx |
1016 | |
54310121 |
1017 | (X) You can't allocate more than 64K on an MS-DOS machine. |
5f05dabc |
1018 | |
1019 | =item Allocation too large |
1020 | |
1021 | (F) You can't allocate more than 2^31+"small amount" bytes. |
1022 | |
54310121 |
1023 | =item Applying %s to %s will act on scalar(%s) |
1024 | |
1025 | (W) The pattern match (//), substitution (s///), and translation (tr///) |
1026 | operators work on scalar values. If you apply one of them to an array |
1027 | or a hash, it will convert the array or hash to a scalar value -- the |
1028 | length of an array, or the population info of a hash -- and then work on |
1029 | that scalar value. This is probably not what you meant to do. See |
1030 | L<perlfunc/grep> and L<perlfunc/map> for alternatives. |
1031 | |
1032 | =item Attempt to free nonexistent shared string |
5f05dabc |
1033 | |
1034 | (P) Perl maintains a reference counted internal table of strings to |
1035 | optimize the storage and access of hash keys and other strings. This |
1036 | indicates someone tried to decrement the reference count of a string |
1037 | that can no longer be found in the table. |
1038 | |
1039 | =item Attempt to use reference as lvalue in substr |
1040 | |
1041 | (W) You supplied a reference as the first argument to substr() used |
1042 | as an lvalue, which is pretty strange. Perhaps you forgot to |
1043 | dereference it first. See L<perlfunc/substr>. |
1044 | |
774d564b |
1045 | =item Can't use bareword ("%s") as %s ref while "strict refs" in use |
1046 | |
1047 | (F) Only hard references are allowed by "strict refs". Symbolic references |
1048 | are disallowed. See L<perlref>. |
1049 | |
54310121 |
1050 | =item Cannot resolve method `%s' overloading `%s' in package `%s' |
1051 | |
1052 | (P) Internal error trying to resolve overloading specified by a method |
1053 | name (as opposed to a subroutine reference). |
1054 | |
774d564b |
1055 | =item Constant subroutine %s redefined |
1056 | |
1057 | (S) You redefined a subroutine which had previously been eligible for |
dc848c6f |
1058 | inlining. See L<perlsub/"Constant Functions"> for commentary and |
54310121 |
1059 | workarounds. |
1060 | |
1061 | =item Constant subroutine %s undefined |
1062 | |
1063 | (S) You undefined a subroutine which had previously been eligible for |
774d564b |
1064 | inlining. See L<perlsub/"Constant Functions"> for commentary and |
1065 | workarounds. |
1066 | |
54310121 |
1067 | =item Copy method did not return a reference |
1068 | |
1069 | (F) The method which overloads "=" is buggy. See L<overload/Copy Constructor>. |
1070 | |
774d564b |
1071 | =item Died |
1072 | |
1073 | (F) You passed die() an empty string (the equivalent of C<die "">) or |
1074 | you called it with no args and both C<$@> and C<$_> were empty. |
1075 | |
54310121 |
1076 | =item Exiting pseudo-block via %s |
1077 | |
1078 | (W) You are exiting a rather special block construct (like a sort block or |
1079 | subroutine) by unconventional means, such as a goto, or a loop control |
1080 | statement. See L<perlfunc/sort>. |
1081 | |
8903cb82 |
1082 | =item Identifier too long |
1083 | |
1084 | (F) Perl limits identifiers (names for variables, functions, etc.) to |
1085 | 252 characters for simple names, somewhat more for compound names (like |
1086 | C<$A::B>). You've exceeded Perl's limits. Future versions of Perl are |
1087 | likely to eliminate these arbitrary limitations. |
1088 | |
54310121 |
1089 | =item Illegal character %s (carriage return) |
1090 | |
1091 | (F) A carriage return character was found in the input. This is an |
1092 | error, and not a warning, because carriage return characters can break |
1093 | multi-line strings, including here documents (e.g., C<print E<lt>E<lt>EOF;>). |
1094 | |
1095 | =item Illegal switch in PERL5OPT: %s |
1096 | |
1097 | (X) The PERL5OPT environment variable may only be used to set the |
1098 | following switches: B<-[DIMUdmw]>. |
1099 | |
5f05dabc |
1100 | =item Integer overflow in hex number |
1101 | |
1102 | (S) The literal hex number you have specified is too big for your |
1103 | architecture. On a 32-bit architecture the largest hex literal is |
1104 | 0xFFFFFFFF. |
1105 | |
1106 | =item Integer overflow in octal number |
1107 | |
1108 | (S) The literal octal number you have specified is too big for your |
1109 | architecture. On a 32-bit architecture the largest octal literal is |
1110 | 037777777777. |
1111 | |
5cd24f17 |
1112 | =item internal error: glob failed |
1113 | |
1114 | (P) Something went wrong with the external program(s) used for C<glob> |
1115 | and C<E<lt>*.cE<gt>>. This may mean that your csh (C shell) is |
1116 | broken. If so, you should change all of the csh-related variables in |
1117 | config.sh: If you have tcsh, make the variables refer to it as if it |
1118 | were csh (e.g. C<full_csh='/usr/bin/tcsh'>); otherwise, make them all |
1119 | empty (except that C<d_csh> should be C<'undef'>) so that Perl will |
1120 | think csh is missing. In either case, after editing config.sh, run |
1121 | C<./Configure -S> and rebuild Perl. |
1122 | |
8903cb82 |
1123 | =item Invalid type in pack: '%s' |
1124 | |
1125 | (F) The given character is not a valid pack type. See L<perlfunc/pack>. |
1126 | |
1127 | =item Invalid type in unpack: '%s' |
1128 | |
1129 | (F) The given character is not a valid unpack type. See L<perlfunc/unpack>. |
1130 | |
774d564b |
1131 | =item Name "%s::%s" used only once: possible typo |
1132 | |
1133 | (W) Typographical errors often show up as unique variable names. |
1134 | If you had a good reason for having a unique name, then just mention |
1135 | it again somehow to suppress the message (the C<use vars> pragma is |
1136 | provided for just this purpose). |
1137 | |
5f05dabc |
1138 | =item Null picture in formline |
1139 | |
1140 | (F) The first argument to formline must be a valid format picture |
1141 | specification. It was found to be empty, which probably means you |
1142 | supplied it an uninitialized value. See L<perlform>. |
1143 | |
1144 | =item Offset outside string |
1145 | |
1146 | (F) You tried to do a read/write/send/recv operation with an offset |
1147 | pointing outside the buffer. This is difficult to imagine. |
1148 | The sole exception to this is that C<sysread()>ing past the buffer |
1149 | will extend the buffer and zero pad the new area. |
1150 | |
1151 | =item Out of memory! |
1152 | |
1153 | (X|F) The malloc() function returned 0, indicating there was insufficient |
1154 | remaining memory (or virtual memory) to satisfy the request. |
1155 | |
1156 | The request was judged to be small, so the possibility to trap it |
1157 | depends on the way Perl was compiled. By default it is not trappable. |
1158 | However, if compiled for this, Perl may use the contents of C<$^M> as |
1159 | an emergency pool after die()ing with this message. In this case the |
1160 | error is trappable I<once>. |
1161 | |
1162 | =item Out of memory during request for %s |
1163 | |
1164 | (F) The malloc() function returned 0, indicating there was insufficient |
1165 | remaining memory (or virtual memory) to satisfy the request. However, |
1166 | the request was judged large enough (compile-time default is 64K), so |
1167 | a possibility to shut down by trapping this error is granted. |
1168 | |
1169 | =item Possible attempt to put comments in qw() list |
1170 | |
774d564b |
1171 | (W) qw() lists contain items separated by whitespace; as with literal |
1172 | strings, comment characters are not ignored, but are instead treated |
1173 | as literal data. (You may have used different delimiters than the |
1174 | exclamation marks parentheses shown here; braces are also frequently |
1175 | used.) |
1176 | |
1177 | You probably wrote something like this: |
5f05dabc |
1178 | |
2ae324a7 |
1179 | @list = qw( |
774d564b |
1180 | a # a comment |
5f05dabc |
1181 | b # another comment |
774d564b |
1182 | ); |
5f05dabc |
1183 | |
1184 | when you should have written this: |
1185 | |
774d564b |
1186 | @list = qw( |
2ae324a7 |
1187 | a |
5f05dabc |
1188 | b |
774d564b |
1189 | ); |
1190 | |
1191 | If you really want comments, build your list the |
1192 | old-fashioned way, with quotes and commas: |
1193 | |
1194 | @list = ( |
1195 | 'a', # a comment |
1196 | 'b', # another comment |
1197 | ); |
5f05dabc |
1198 | |
1199 | =item Possible attempt to separate words with commas |
1200 | |
774d564b |
1201 | (W) qw() lists contain items separated by whitespace; therefore commas |
1202 | aren't needed to separate the items. (You may have used different |
1203 | delimiters than the parentheses shown here; braces are also frequently |
1204 | used.) |
5f05dabc |
1205 | |
2ae324a7 |
1206 | You probably wrote something like this: |
5f05dabc |
1207 | |
774d564b |
1208 | qw! a, b, c !; |
1209 | |
1210 | which puts literal commas into some of the list items. Write it without |
1211 | commas if you don't want them to appear in your data: |
1212 | |
1213 | qw! a b c !; |
5f05dabc |
1214 | |
774d564b |
1215 | =item Scalar value @%s{%s} better written as $%s{%s} |
1216 | |
1217 | (W) You've used a hash slice (indicated by @) to select a single element of |
1218 | a hash. Generally it's better to ask for a scalar value (indicated by $). |
1219 | The difference is that C<$foo{&bar}> always behaves like a scalar, both when |
1220 | assigning to it and when evaluating its argument, while C<@foo{&bar}> behaves |
1221 | like a list when you assign to it, and provides a list context to its |
1222 | subscript, which can do weird things if you're expecting only one subscript. |
5f05dabc |
1223 | |
54310121 |
1224 | =item Stub found while resolving method `%s' overloading `%s' in package `%s' |
1225 | |
1226 | (P) Overloading resolution over @ISA tree may be broken by importing stubs. |
1227 | Stubs should never be implicitely created, but explicit calls to C<can> |
1228 | may break this. |
1229 | |
1230 | =item Too late for "B<-T>" option |
1231 | |
1232 | (X) The #! line (or local equivalent) in a Perl script contains the |
1233 | B<-T> option, but Perl was not invoked with B<-T> in its argument |
1234 | list. This is an error because, by the time Perl discovers a B<-T> in |
1235 | a script, it's too late to properly taint everything from the |
1236 | environment. So Perl gives up. |
1237 | |
5f05dabc |
1238 | =item untie attempted while %d inner references still exist |
1239 | |
1240 | (W) A copy of the object returned from C<tie> (or C<tied>) was still |
1241 | valid when C<untie> was called. |
1242 | |
54310121 |
1243 | =item Unrecognized character %s |
1244 | |
1245 | (F) The Perl parser has no idea what to do with the specified character |
1246 | in your Perl script (or eval). Perhaps you tried to run a compressed |
1247 | script, a binary program, or a directory as a Perl program. |
1248 | |
1249 | =item Unsupported function fork |
1250 | |
1251 | (F) Your version of executable does not support forking. |
1252 | |
1253 | Note that under some systems, like OS/2, there may be different flavors of |
1254 | Perl executables, some of which may support fork, some not. Try changing |
1255 | the name you call Perl by to C<perl_>, C<perl__>, and so on. |
1256 | |
5cd24f17 |
1257 | =item Use of "$$<digit>" to mean "${$}<digit>" is deprecated |
1258 | |
1259 | (D) Perl versions before 5.004 misinterpreted any type marker followed |
1260 | by "$" and a digit. For example, "$$0" was incorrectly taken to mean |
1261 | "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004. |
1262 | |
1263 | However, the developers of Perl 5.004 could not fix this bug completely, |
1264 | because at least two widely-used modules depend on the old meaning of |
1265 | "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the |
1266 | old (broken) way inside strings; but it generates this message as a |
1267 | warning. And in Perl 5.005, this special treatment will cease. |
1268 | |
54310121 |
1269 | =item Value of %s can be "0"; test with defined() |
774d564b |
1270 | |
54310121 |
1271 | (W) In a conditional expression, you used <HANDLE>, <*> (glob), C<each()>, |
1272 | or C<readdir()> as a boolean value. Each of these constructs can return a |
1273 | value of "0"; that would make the conditional expression false, which is |
1274 | probably not what you intended. When using these constructs in conditional |
1275 | expressions, test their values with the C<defined> operator. |
774d564b |
1276 | |
1277 | =item Variable "%s" may be unavailable |
1278 | |
1279 | (W) An inner (nested) I<anonymous> subroutine is inside a I<named> |
1280 | subroutine, and outside that is another subroutine; and the anonymous |
1281 | (innermost) subroutine is referencing a lexical variable defined in |
1282 | the outermost subroutine. For example: |
1283 | |
1284 | sub outermost { my $a; sub middle { sub { $a } } } |
1285 | |
1286 | If the anonymous subroutine is called or referenced (directly or |
1287 | indirectly) from the outermost subroutine, it will share the variable |
1288 | as you would expect. But if the anonymous subroutine is called or |
1289 | referenced when the outermost subroutine is not active, it will see |
1290 | the value of the shared variable as it was before and during the |
1291 | *first* call to the outermost subroutine, which is probably not what |
1292 | you want. |
1293 | |
1294 | In these circumstances, it is usually best to make the middle |
1295 | subroutine anonymous, using the C<sub {}> syntax. Perl has specific |
1296 | support for shared variables in nested anonymous subroutines; a named |
1297 | subroutine in between interferes with this feature. |
1298 | |
1299 | =item Variable "%s" will not stay shared |
1300 | |
1301 | (W) An inner (nested) I<named> subroutine is referencing a lexical |
1302 | variable defined in an outer subroutine. |
1303 | |
1304 | When the inner subroutine is called, it will probably see the value of |
1305 | the outer subroutine's variable as it was before and during the |
1306 | *first* call to the outer subroutine; in this case, after the first |
1307 | call to the outer subroutine is complete, the inner and outer |
1308 | subroutines will no longer share a common value for the variable. In |
1309 | other words, the variable will no longer be shared. |
1310 | |
1311 | Furthermore, if the outer subroutine is anonymous and references a |
1312 | lexical variable outside itself, then the outer and inner subroutines |
1313 | will I<never> share the given variable. |
1314 | |
1315 | This problem can usually be solved by making the inner subroutine |
1316 | anonymous, using the C<sub {}> syntax. When inner anonymous subs that |
1317 | reference variables in outer subroutines are called or referenced, |
54310121 |
1318 | they are automatically rebound to the current values of such |
774d564b |
1319 | variables. |
1320 | |
1321 | =item Warning: something's wrong |
1322 | |
1323 | (W) You passed warn() an empty string (the equivalent of C<warn "">) or |
1324 | you called it with no args and C<$_> was empty. |
1325 | |
54310121 |
1326 | =item Ill-formed logical name |%s| in prime_env_iter |
1327 | |
1328 | (W) A warning peculiar to VMS. A logical name was encountered when preparing |
1329 | to iterate over %ENV which violates the syntactic rules governing logical |
1330 | names. Since it cannot be translated normally, it is skipped, and will not |
1331 | appear in %ENV. This may be a benign occurrence, as some software packages |
1332 | might directly modify logical name tables and introduce nonstandard names, |
1333 | or it may indicate that a logical name table has been corrupted. |
1334 | |
774d564b |
1335 | =item Got an error from DosAllocMem |
5f05dabc |
1336 | |
774d564b |
1337 | (P) An error peculiar to OS/2. Most probably you're using an obsolete |
1338 | version of Perl, and this should not happen anyway. |
5f05dabc |
1339 | |
1340 | =item Malformed PERLLIB_PREFIX |
1341 | |
dc848c6f |
1342 | (F) An error peculiar to OS/2. PERLLIB_PREFIX should be of the form |
5f05dabc |
1343 | |
1344 | prefix1;prefix2 |
1345 | |
1346 | or |
1347 | |
1348 | prefix1 prefix2 |
1349 | |
dc848c6f |
1350 | with nonempty prefix1 and prefix2. If C<prefix1> is indeed a prefix |
1351 | of a builtin library search path, prefix2 is substituted. The error |
1352 | may appear if components are not found, or are too long. See |
1353 | "PERLLIB_PREFIX" in F<README.os2>. |
5f05dabc |
1354 | |
1355 | =item PERL_SH_DIR too long |
1356 | |
1357 | (F) An error peculiar to OS/2. PERL_SH_DIR is the directory to find the |
dc848c6f |
1358 | C<sh>-shell in. See "PERL_SH_DIR" in F<README.os2>. |
5f05dabc |
1359 | |
1360 | =item Process terminated by SIG%s |
1361 | |
1362 | (W) This is a standard message issued by OS/2 applications, while *nix |
dc848c6f |
1363 | applications die in silence. It is considered a feature of the OS/2 |
1364 | port. One can easily disable this by appropriate sighandlers, see |
1365 | L<perlipc/"Signals">. See also "Process terminated by SIGTERM/SIGINT" |
1366 | in F<README.os2>. |
5f05dabc |
1367 | |
1368 | =back |
1369 | |
1370 | =head1 BUGS |
1371 | |
774d564b |
1372 | If you find what you think is a bug, you might check the headers of |
1373 | recently posted articles in the comp.lang.perl.misc newsgroup. |
1374 | There may also be information at http://www.perl.com/perl/, the Perl |
1375 | Home Page. |
5f05dabc |
1376 | |
1377 | If you believe you have an unreported bug, please run the B<perlbug> |
9607fc9c |
1378 | program included with your release. Make sure you trim your bug down |
1379 | to a tiny but sufficient test case. Your bug report, along with the |
1380 | output of C<perl -V>, will be sent off to <F<perlbug@perl.com>> to be |
1381 | analysed by the Perl porting team. |
5f05dabc |
1382 | |
1383 | =head1 SEE ALSO |
1384 | |
1385 | The F<Changes> file for exhaustive details on what changed. |
1386 | |
1387 | The F<INSTALL> file for how to build Perl. This file has been |
1388 | significantly updated for 5.004, so even veteran users should |
1389 | look through it. |
1390 | |
1391 | The F<README> file for general stuff. |
1392 | |
1393 | The F<Copying> file for copyright information. |
1394 | |
1395 | =head1 HISTORY |
1396 | |
1397 | Constructed by Tom Christiansen, grabbing material with permission |
1398 | from innumerable contributors, with kibitzing by more than a few Perl |
1399 | porters. |
1400 | |
2ae324a7 |
1401 | Last update: Sat Mar 8 19:51:26 EST 1997 |