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69bcf1d3 FC |
1 | #!/usr/bin/perl |
2 | # | |
3 | # Regenerate (overwriting only if changed): | |
4 | # | |
5 | # lib/feature.pm | |
f2c01b15 | 6 | # feature.h |
69bcf1d3 | 7 | # |
3489ea76 | 8 | # from information hardcoded into this script and from two #defines |
d73d634c | 9 | # in perl.h. |
69bcf1d3 FC |
10 | # |
11 | # This script is normally invoked from regen.pl. | |
12 | ||
13 | BEGIN { | |
14 | require 'regen/regen_lib.pl'; | |
15 | push @INC, './lib'; | |
16 | } | |
17 | use strict ; | |
18 | ||
c452a42f FC |
19 | |
20 | ########################################################################### | |
21 | # Hand-editable data | |
22 | ||
c6b36e45 | 23 | # (feature name) => (internal name, used in %^H and macro names) |
69bcf1d3 | 24 | my %feature = ( |
67bdaa9e FC |
25 | say => 'say', |
26 | state => 'state', | |
27 | switch => 'switch', | |
28 | evalbytes => 'evalbytes', | |
b9a36c95 | 29 | postderef => 'postderef', |
3fff3427 | 30 | array_base => 'arybase', |
67bdaa9e | 31 | current_sub => '__SUB__', |
baabe3fb | 32 | refaliasing => 'refaliasing', |
ebd25686 | 33 | lexical_subs => 'lexsubs', |
158becca | 34 | postderef_qq => 'postderef_qq', |
67bdaa9e FC |
35 | unicode_eval => 'unieval', |
36 | unicode_strings => 'unicode', | |
2a4315f8 | 37 | fc => 'fc', |
30d9c59b | 38 | signatures => 'signatures', |
69bcf1d3 FC |
39 | ); |
40 | ||
40e4d872 FC |
41 | # NOTE: If a feature is ever enabled in a non-contiguous range of Perl |
42 | # versions, any code below that uses %BundleRanges will have to | |
43 | # be changed to account. | |
44 | ||
52fc5c56 | 45 | # 5.odd implies the next 5.even, but an explicit 5.even can override it. |
69bcf1d3 | 46 | my %feature_bundle = ( |
39ec54a5 | 47 | all => [ keys %feature ], |
3fff3427 | 48 | default => [qw(array_base)], |
69bcf1d3 FC |
49 | "5.9.5" => [qw(say state switch array_base)], |
50 | "5.10" => [qw(say state switch array_base)], | |
51 | "5.11" => [qw(say state switch unicode_strings array_base)], | |
69bcf1d3 | 52 | "5.13" => [qw(say state switch unicode_strings array_base)], |
69bcf1d3 | 53 | "5.15" => [qw(say state switch unicode_strings unicode_eval |
2a4315f8 | 54 | evalbytes current_sub fc)], |
d6402ebe RS |
55 | "5.17" => [qw(say state switch unicode_strings unicode_eval |
56 | evalbytes current_sub fc)], | |
d09258e7 RS |
57 | "5.19" => [qw(say state switch unicode_strings unicode_eval |
58 | evalbytes current_sub fc)], | |
b530a4ea RS |
59 | "5.21" => [qw(say state switch unicode_strings unicode_eval |
60 | evalbytes current_sub fc)], | |
69bcf1d3 FC |
61 | ); |
62 | ||
64fbf0dd | 63 | # not actually used currently |
ebd25686 FC |
64 | my @experimental = qw( lexical_subs ); |
65 | ||
c452a42f | 66 | |
69bcf1d3 | 67 | ########################################################################### |
c452a42f | 68 | # More data generated from the above |
69bcf1d3 | 69 | |
52fc5c56 FC |
70 | for (keys %feature_bundle) { |
71 | next unless /^5\.(\d*[13579])\z/; | |
72 | $feature_bundle{"5.".($1+1)} ||= $feature_bundle{$_}; | |
73 | } | |
74 | ||
f2c01b15 FC |
75 | my %UniqueBundles; # "say state switch" => 5.10 |
76 | my %Aliases; # 5.12 => 5.11 | |
77 | for( sort keys %feature_bundle ) { | |
78 | my $value = join(' ', sort @{$feature_bundle{$_}}); | |
79 | if (exists $UniqueBundles{$value}) { | |
80 | $Aliases{$_} = $UniqueBundles{$value}; | |
81 | } | |
82 | else { | |
83 | $UniqueBundles{$value} = $_; | |
84 | } | |
85 | } | |
40e4d872 FC |
86 | # start end |
87 | my %BundleRanges; # say => ['5.10', '5.15'] # unique bundles for values | |
88 | for my $bund ( | |
89 | sort { $a eq 'default' ? -1 : $b eq 'default' ? 1 : $a cmp $b } | |
90 | values %UniqueBundles | |
91 | ) { | |
03222170 | 92 | next if $bund =~ /[^\d.]/ and $bund ne 'default'; |
40e4d872 FC |
93 | for (@{$feature_bundle{$bund}}) { |
94 | if (@{$BundleRanges{$_} ||= []} == 2) { | |
95 | $BundleRanges{$_}[1] = $bund | |
96 | } | |
97 | else { | |
98 | push @{$BundleRanges{$_}}, $bund; | |
99 | } | |
100 | } | |
101 | } | |
69bcf1d3 | 102 | |
47222a2d | 103 | my $HintShift; |
ada44f8c | 104 | my $HintMask; |
3489ea76 | 105 | my $Uni8Bit; |
47222a2d FC |
106 | |
107 | open "perl.h", "perl.h" or die "$0 cannot open perl.h: $!"; | |
3489ea76 FC |
108 | while (readline "perl.h") { |
109 | next unless /#\s*define\s+(HINT_FEATURE_MASK|HINT_UNI_8_BIT)/; | |
110 | my $is_u8b = $1 =~ 8; | |
111 | /(0x[A-Fa-f0-9]+)/ or die "No hex number in:\n\n$_\n "; | |
112 | if ($is_u8b) { | |
113 | $Uni8Bit = $1; | |
114 | } | |
115 | else { | |
ada44f8c | 116 | my $hex = $HintMask = $1; |
47222a2d FC |
117 | my $bits = sprintf "%b", oct $1; |
118 | $bits =~ /^0*1+(0*)\z/ | |
119 | or die "Non-contiguous bits in $bits (binary for $hex):\n\n$_\n "; | |
120 | $HintShift = length $1; | |
121 | my $bits_needed = | |
122 | length sprintf "%b", scalar keys %UniqueBundles; | |
123 | $bits =~ /1{$bits_needed}/ | |
124 | or die "Not enough bits (need $bits_needed)" | |
5d826eae | 125 | . " in $bits (binary for $hex):\n\n$_\n "; |
47222a2d | 126 | } |
3489ea76 | 127 | if ($Uni8Bit && $HintMask) { last } |
47222a2d | 128 | } |
3489ea76 FC |
129 | die "No HINT_FEATURE_MASK defined in perl.h" unless $HintMask; |
130 | die "No HINT_UNI_8_BIT defined in perl.h" unless $Uni8Bit; | |
131 | ||
47222a2d FC |
132 | close "perl.h"; |
133 | ||
ada44f8c FC |
134 | my @HintedBundles = |
135 | ('default', grep !/[^\d.]/, sort values %UniqueBundles); | |
136 | ||
47222a2d | 137 | |
f2c01b15 | 138 | ########################################################################### |
c452a42f | 139 | # Open files to be generated |
f2c01b15 FC |
140 | |
141 | my ($pm, $h) = map { | |
69bcf1d3 | 142 | open_new($_, '>', { by => 'regen/feature.pl' }); |
f2c01b15 | 143 | } 'lib/feature.pm', 'feature.h'; |
69bcf1d3 FC |
144 | |
145 | ||
c452a42f FC |
146 | ########################################################################### |
147 | # Generate lib/feature.pm | |
148 | ||
69bcf1d3 FC |
149 | while (<DATA>) { |
150 | last if /^FEATURES$/ ; | |
151 | print $pm $_ ; | |
152 | } | |
153 | ||
154 | sub longest { | |
155 | my $long; | |
156 | for(@_) { | |
157 | if (!defined $long or length $long < length) { | |
158 | $long = $_; | |
159 | } | |
160 | } | |
161 | $long; | |
162 | } | |
163 | ||
0bb01b05 | 164 | print $pm "our %feature = (\n"; |
69bcf1d3 | 165 | my $width = length longest keys %feature; |
ebd25686 | 166 | for(sort { length $a <=> length $b || $a cmp $b } keys %feature) { |
67bdaa9e FC |
167 | print $pm " $_" . " "x($width-length) |
168 | . " => 'feature_$feature{$_}',\n"; | |
69bcf1d3 FC |
169 | } |
170 | print $pm ");\n\n"; | |
171 | ||
69bcf1d3 | 172 | print $pm "our %feature_bundle = (\n"; |
88da30d7 FC |
173 | $width = length longest values %UniqueBundles; |
174 | for( sort { $UniqueBundles{$a} cmp $UniqueBundles{$b} } | |
175 | keys %UniqueBundles ) { | |
176 | my $bund = $UniqueBundles{$_}; | |
177 | print $pm qq' "$bund"' . " "x($width-length $bund) | |
178 | . qq' => [qw($_)],\n'; | |
69bcf1d3 FC |
179 | } |
180 | print $pm ");\n\n"; | |
181 | ||
88da30d7 FC |
182 | for (sort keys %Aliases) { |
183 | print $pm | |
184 | qq'\$feature_bundle{"$_"} = \$feature_bundle{"$Aliases{$_}"};\n'; | |
185 | }; | |
69bcf1d3 | 186 | |
64fbf0dd FC |
187 | #print $pm "my \%experimental = (\n"; |
188 | #print $pm " $_ => 1,\n", for @experimental; | |
189 | #print $pm ");\n"; | |
ebd25686 | 190 | |
ada44f8c FC |
191 | print $pm <<EOPM; |
192 | ||
0bb01b05 FC |
193 | our \$hint_shift = $HintShift; |
194 | our \$hint_mask = $HintMask; | |
195 | our \@hint_bundles = qw( @HintedBundles ); | |
3489ea76 FC |
196 | |
197 | # This gets set (for now) in \$^H as well as in %^H, | |
198 | # for runtime speed of the uc/lc/ucfirst/lcfirst functions. | |
199 | # See HINT_UNI_8_BIT in perl.h. | |
200 | our \$hint_uni8bit = $Uni8Bit; | |
ada44f8c FC |
201 | EOPM |
202 | ||
69bcf1d3 FC |
203 | |
204 | while (<DATA>) { | |
2b3fe414 FC |
205 | last if /^PODTURES$/ ; |
206 | print $pm $_ ; | |
207 | } | |
208 | ||
209 | select +(select($pm), $~ = 'PODTURES')[0]; | |
210 | format PODTURES = | |
211 | ^<<<<<<<< ^<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<~~ | |
212 | $::bundle, $::feature | |
213 | . | |
214 | ||
215 | for ('default', sort grep /\.\d[02468]/, keys %feature_bundle) { | |
216 | $::bundle = ":$_"; | |
217 | $::feature = join ' ', @{$feature_bundle{$_}}; | |
218 | write $pm; | |
219 | print $pm "\n"; | |
220 | } | |
221 | ||
222 | while (<DATA>) { | |
69bcf1d3 FC |
223 | print $pm $_ ; |
224 | } | |
225 | ||
226 | read_only_bottom_close_and_rename($pm); | |
227 | ||
c452a42f FC |
228 | |
229 | ########################################################################### | |
230 | # Generate feature.h | |
231 | ||
f2c01b15 FC |
232 | print $h <<EOH; |
233 | ||
234 | #if defined(PERL_CORE) || defined (PERL_EXT) | |
235 | ||
236 | #define HINT_FEATURE_SHIFT $HintShift | |
237 | ||
f2c01b15 FC |
238 | EOH |
239 | ||
240 | my $count; | |
016d11cb FC |
241 | for (@HintedBundles) { |
242 | (my $key = uc) =~ y/.//d; | |
243 | print $h "#define FEATURE_BUNDLE_$key ", $count++, "\n"; | |
f2c01b15 FC |
244 | } |
245 | ||
7d058bc9 | 246 | print $h <<'EOH'; |
2b9e0ab7 | 247 | #define FEATURE_BUNDLE_CUSTOM (HINT_FEATURE_MASK >> HINT_FEATURE_SHIFT) |
f2c01b15 | 248 | |
7d058bc9 | 249 | #define CURRENT_HINTS \ |
d1fd0100 | 250 | (PL_curcop == &PL_compiling ? PL_hints : PL_curcop->cop_hints) |
035b6821 FC |
251 | #define CURRENT_FEATURE_BUNDLE \ |
252 | ((CURRENT_HINTS & HINT_FEATURE_MASK) >> HINT_FEATURE_SHIFT) | |
d1fd0100 | 253 | |
fc4b5f72 NC |
254 | /* Avoid using ... && Perl_feature_is_enabled(...) as that triggers a bug in |
255 | the HP-UX cc on PA-RISC */ | |
7d058bc9 | 256 | #define FEATURE_IS_ENABLED(name) \ |
ef744b29 | 257 | ((CURRENT_HINTS \ |
7d058bc9 | 258 | & HINT_LOCALIZE_HH) \ |
fc4b5f72 | 259 | ? Perl_feature_is_enabled(aTHX_ STR_WITH_LEN(name)) : FALSE) |
7d058bc9 | 260 | /* The longest string we pass in. */ |
03222170 FC |
261 | EOH |
262 | ||
1b6e8741 FC |
263 | my $longest_internal_feature_name = longest values %feature; |
264 | print $h <<EOL; | |
265 | #define MAX_FEATURE_LEN (sizeof("$longest_internal_feature_name")-1) | |
266 | ||
267 | EOL | |
268 | ||
03222170 | 269 | for ( |
ebd25686 | 270 | sort { length $a <=> length $b || $a cmp $b } keys %feature |
03222170 FC |
271 | ) { |
272 | my($first,$last) = | |
273 | map { (my $__ = uc) =~ y/.//d; $__ } @{$BundleRanges{$_}}; | |
3fff3427 | 274 | my $name = $feature{$_}; |
03222170 | 275 | my $NAME = uc $name; |
beda0318 FC |
276 | if ($last && $first eq 'DEFAULT') { # ‘>= DEFAULT’ warns |
277 | print $h <<EOI; | |
278 | #define FEATURE_$NAME\_IS_ENABLED \\ | |
279 | ( \\ | |
280 | CURRENT_FEATURE_BUNDLE <= FEATURE_BUNDLE_$last \\ | |
281 | || (CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_CUSTOM && \\ | |
3fff3427 | 282 | FEATURE_IS_ENABLED("$name")) \\ |
beda0318 FC |
283 | ) |
284 | ||
285 | EOI | |
286 | } | |
287 | elsif ($last) { | |
03222170 FC |
288 | print $h <<EOH3; |
289 | #define FEATURE_$NAME\_IS_ENABLED \\ | |
290 | ( \\ | |
291 | (CURRENT_FEATURE_BUNDLE >= FEATURE_BUNDLE_$first && \\ | |
292 | CURRENT_FEATURE_BUNDLE <= FEATURE_BUNDLE_$last) \\ | |
293 | || (CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_CUSTOM && \\ | |
3fff3427 | 294 | FEATURE_IS_ENABLED("$name")) \\ |
03222170 FC |
295 | ) |
296 | ||
297 | EOH3 | |
298 | } | |
ebd25686 | 299 | elsif ($first) { |
03222170 FC |
300 | print $h <<EOH4; |
301 | #define FEATURE_$NAME\_IS_ENABLED \\ | |
302 | ( \\ | |
303 | CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_$first \\ | |
304 | || (CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_CUSTOM && \\ | |
3fff3427 | 305 | FEATURE_IS_ENABLED("$name")) \\ |
03222170 FC |
306 | ) |
307 | ||
308 | EOH4 | |
309 | } | |
ebd25686 FC |
310 | else { |
311 | print $h <<EOH5; | |
312 | #define FEATURE_$NAME\_IS_ENABLED \\ | |
313 | ( \\ | |
314 | CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_CUSTOM && \\ | |
315 | FEATURE_IS_ENABLED("$name") \\ | |
316 | ) | |
317 | ||
318 | EOH5 | |
319 | } | |
03222170 FC |
320 | } |
321 | ||
322 | print $h <<EOH; | |
323 | ||
f2c01b15 | 324 | #endif /* PERL_CORE or PERL_EXT */ |
4160ddbd FC |
325 | |
326 | #ifdef PERL_IN_OP_C | |
327 | PERL_STATIC_INLINE void | |
328 | S_enable_feature_bundle(pTHX_ SV *ver) | |
329 | { | |
330 | SV *comp_ver = sv_newmortal(); | |
331 | PL_hints = (PL_hints &~ HINT_FEATURE_MASK) | |
332 | | ( | |
f2c01b15 FC |
333 | EOH |
334 | ||
4160ddbd FC |
335 | for (reverse @HintedBundles[1..$#HintedBundles]) { # skip default |
336 | my $numver = $_; | |
337 | if ($numver eq '5.10') { $numver = '5.009005' } # special case | |
338 | else { $numver =~ s/\./.0/ } # 5.11 => 5.011 | |
339 | (my $macrover = $_) =~ y/.//d; | |
340 | print $h <<" EOK"; | |
341 | (sv_setnv(comp_ver, $numver), | |
342 | vcmp(ver, upg_version(comp_ver, FALSE)) >= 0) | |
343 | ? FEATURE_BUNDLE_$macrover : | |
344 | EOK | |
345 | } | |
346 | ||
347 | print $h <<EOJ; | |
348 | FEATURE_BUNDLE_DEFAULT | |
349 | ) << HINT_FEATURE_SHIFT; | |
6389c777 FC |
350 | /* special case */ |
351 | assert(PL_curcop == &PL_compiling); | |
352 | if (FEATURE_UNICODE_IS_ENABLED) PL_hints |= HINT_UNI_8_BIT; | |
353 | else PL_hints &= ~HINT_UNI_8_BIT; | |
4160ddbd FC |
354 | } |
355 | #endif /* PERL_IN_OP_C */ | |
356 | EOJ | |
357 | ||
f2c01b15 FC |
358 | read_only_bottom_close_and_rename($h); |
359 | ||
c452a42f FC |
360 | |
361 | ########################################################################### | |
362 | # Template for feature.pm | |
363 | ||
69bcf1d3 FC |
364 | __END__ |
365 | package feature; | |
366 | ||
f86d720e | 367 | our $VERSION = '1.39'; |
69bcf1d3 FC |
368 | |
369 | FEATURES | |
370 | ||
69bcf1d3 FC |
371 | # TODO: |
372 | # - think about versioned features (use feature switch => 2) | |
373 | ||
374 | =head1 NAME | |
375 | ||
376 | feature - Perl pragma to enable new features | |
377 | ||
378 | =head1 SYNOPSIS | |
379 | ||
380 | use feature qw(say switch); | |
381 | given ($foo) { | |
382 | when (1) { say "\$foo == 1" } | |
383 | when ([2,3]) { say "\$foo == 2 || \$foo == 3" } | |
384 | when (/^a[bc]d$/) { say "\$foo eq 'abd' || \$foo eq 'acd'" } | |
385 | when ($_ > 100) { say "\$foo > 100" } | |
386 | default { say "None of the above" } | |
387 | } | |
388 | ||
389 | use feature ':5.10'; # loads all features available in perl 5.10 | |
390 | ||
391 | use v5.10; # implicitly loads :5.10 feature bundle | |
392 | ||
393 | =head1 DESCRIPTION | |
394 | ||
395 | It is usually impossible to add new syntax to Perl without breaking | |
396 | some existing programs. This pragma provides a way to minimize that | |
397 | risk. New syntactic constructs, or new semantic meanings to older | |
398 | constructs, can be enabled by C<use feature 'foo'>, and will be parsed | |
399 | only when the appropriate feature pragma is in scope. (Nevertheless, the | |
400 | C<CORE::> prefix provides access to all Perl keywords, regardless of this | |
401 | pragma.) | |
402 | ||
403 | =head2 Lexical effect | |
404 | ||
405 | Like other pragmas (C<use strict>, for example), features have a lexical | |
301381dc | 406 | effect. C<use feature qw(foo)> will only make the feature "foo" available |
69bcf1d3 FC |
407 | from that point to the end of the enclosing block. |
408 | ||
409 | { | |
410 | use feature 'say'; | |
411 | say "say is available here"; | |
412 | } | |
413 | print "But not here.\n"; | |
414 | ||
415 | =head2 C<no feature> | |
416 | ||
417 | Features can also be turned off by using C<no feature "foo">. This too | |
418 | has lexical effect. | |
419 | ||
420 | use feature 'say'; | |
421 | say "say is available here"; | |
422 | { | |
423 | no feature 'say'; | |
424 | print "But not here.\n"; | |
425 | } | |
426 | say "Yet it is here."; | |
427 | ||
39ec54a5 RS |
428 | C<no feature> with no features specified will reset to the default group. To |
429 | disable I<all> features (an unusual request!) use C<no feature ':all'>. | |
69bcf1d3 FC |
430 | |
431 | =head1 AVAILABLE FEATURES | |
432 | ||
433 | =head2 The 'say' feature | |
434 | ||
435 | C<use feature 'say'> tells the compiler to enable the Perl 6 style | |
436 | C<say> function. | |
437 | ||
438 | See L<perlfunc/say> for details. | |
439 | ||
440 | This feature is available starting with Perl 5.10. | |
441 | ||
442 | =head2 The 'state' feature | |
443 | ||
444 | C<use feature 'state'> tells the compiler to enable C<state> | |
445 | variables. | |
446 | ||
447 | See L<perlsub/"Persistent Private Variables"> for details. | |
448 | ||
449 | This feature is available starting with Perl 5.10. | |
450 | ||
451 | =head2 The 'switch' feature | |
452 | ||
7caca87c DB |
453 | B<WARNING>: Because the L<smartmatch operator|perlop/"Smartmatch Operator"> is |
454 | experimental, Perl will warn when you use this feature, unless you have | |
455 | explicitly disabled the warning: | |
456 | ||
457 | no warnings "experimental::smartmatch"; | |
458 | ||
69bcf1d3 FC |
459 | C<use feature 'switch'> tells the compiler to enable the Perl 6 |
460 | given/when construct. | |
461 | ||
48238296 | 462 | See L<perlsyn/"Switch Statements"> for details. |
69bcf1d3 FC |
463 | |
464 | This feature is available starting with Perl 5.10. | |
465 | ||
466 | =head2 The 'unicode_strings' feature | |
467 | ||
850b7ec9 | 468 | C<use feature 'unicode_strings'> tells the compiler to use Unicode rules |
69bcf1d3 FC |
469 | in all string operations executed within its scope (unless they are also |
470 | within the scope of either C<use locale> or C<use bytes>). The same applies | |
471 | to all regular expressions compiled within the scope, even if executed outside | |
2269d15c KW |
472 | it. It does not change the internal representation of strings, but only how |
473 | they are interpreted. | |
69bcf1d3 FC |
474 | |
475 | C<no feature 'unicode_strings'> tells the compiler to use the traditional | |
850b7ec9 | 476 | Perl rules wherein the native character set rules is used unless it is |
69bcf1d3 FC |
477 | clear to Perl that Unicode is desired. This can lead to some surprises |
478 | when the behavior suddenly changes. (See | |
479 | L<perlunicode/The "Unicode Bug"> for details.) For this reason, if you are | |
480 | potentially using Unicode in your program, the | |
481 | C<use feature 'unicode_strings'> subpragma is B<strongly> recommended. | |
482 | ||
2e2b2571 KW |
483 | This feature is available starting with Perl 5.12; was almost fully |
484 | implemented in Perl 5.14; and extended in Perl 5.16 to cover C<quotemeta>. | |
69bcf1d3 FC |
485 | |
486 | =head2 The 'unicode_eval' and 'evalbytes' features | |
487 | ||
488 | Under the C<unicode_eval> feature, Perl's C<eval> function, when passed a | |
489 | string, will evaluate it as a string of characters, ignoring any | |
490 | C<use utf8> declarations. C<use utf8> exists to declare the encoding of | |
491 | the script, which only makes sense for a stream of bytes, not a string of | |
492 | characters. Source filters are forbidden, as they also really only make | |
493 | sense on strings of bytes. Any attempt to activate a source filter will | |
494 | result in an error. | |
495 | ||
496 | The C<evalbytes> feature enables the C<evalbytes> keyword, which evaluates | |
497 | the argument passed to it as a string of bytes. It dies if the string | |
498 | contains any characters outside the 8-bit range. Source filters work | |
499 | within C<evalbytes>: they apply to the contents of the string being | |
500 | evaluated. | |
501 | ||
502 | Together, these two features are intended to replace the historical C<eval> | |
503 | function, which has (at least) two bugs in it, that cannot easily be fixed | |
504 | without breaking existing programs: | |
505 | ||
506 | =over | |
507 | ||
508 | =item * | |
509 | ||
510 | C<eval> behaves differently depending on the internal encoding of the | |
511 | string, sometimes treating its argument as a string of bytes, and sometimes | |
512 | as a string of characters. | |
513 | ||
514 | =item * | |
515 | ||
516 | Source filters activated within C<eval> leak out into whichever I<file> | |
517 | scope is currently being compiled. To give an example with the CPAN module | |
518 | L<Semi::Semicolons>: | |
519 | ||
520 | BEGIN { eval "use Semi::Semicolons; # not filtered here " } | |
521 | # filtered here! | |
522 | ||
523 | C<evalbytes> fixes that to work the way one would expect: | |
524 | ||
525 | use feature "evalbytes"; | |
526 | BEGIN { evalbytes "use Semi::Semicolons; # filtered " } | |
527 | # not filtered | |
528 | ||
529 | =back | |
530 | ||
531 | These two features are available starting with Perl 5.16. | |
532 | ||
533 | =head2 The 'current_sub' feature | |
534 | ||
535 | This provides the C<__SUB__> token that returns a reference to the current | |
536 | subroutine or C<undef> outside of a subroutine. | |
537 | ||
538 | This feature is available starting with Perl 5.16. | |
539 | ||
540 | =head2 The 'array_base' feature | |
541 | ||
542 | This feature supports the legacy C<$[> variable. See L<perlvar/$[> and | |
543 | L<arybase>. It is on by default but disabled under C<use v5.16> (see | |
544 | L</IMPLICIT LOADING>, below). | |
545 | ||
546 | This feature is available under this name starting with Perl 5.16. In | |
547 | previous versions, it was simply on all the time, and this pragma knew | |
548 | nothing about it. | |
549 | ||
2a4315f8 BF |
550 | =head2 The 'fc' feature |
551 | ||
552 | C<use feature 'fc'> tells the compiler to enable the C<fc> function, | |
553 | which implements Unicode casefolding. | |
554 | ||
555 | See L<perlfunc/fc> for details. | |
556 | ||
557 | This feature is available from Perl 5.16 onwards. | |
558 | ||
ca40957e FC |
559 | =head2 The 'lexical_subs' feature |
560 | ||
561 | B<WARNING>: This feature is still experimental and the implementation may | |
64fbf0dd FC |
562 | change in future versions of Perl. For this reason, Perl will |
563 | warn when you use the feature, unless you have explicitly disabled the | |
ca40957e FC |
564 | warning: |
565 | ||
f1d34ca8 | 566 | no warnings "experimental::lexical_subs"; |
ca40957e FC |
567 | |
568 | This enables declaration of subroutines via C<my sub foo>, C<state sub foo> | |
569 | and C<our sub foo> syntax. See L<perlsub/Lexical Subroutines> for details. | |
570 | ||
571 | This feature is available from Perl 5.18 onwards. | |
572 | ||
f86d720e RS |
573 | =head2 The 'postderef' and 'postderef_qq' features |
574 | ||
575 | B<WARNING>: This feature is still experimental and the implementation may | |
576 | change in future versions of Perl. For this reason, Perl will | |
577 | warn when you use the feature, unless you have explicitly disabled the | |
578 | warning: | |
579 | ||
580 | no warnings "experimental::postderef"; | |
581 | ||
582 | The 'postderef' feature allows the use of L<postfix dereference | |
583 | syntax|perlref/Postfix Dereference Syntax>. For example, it will make the | |
584 | following two statements equivalent: | |
585 | ||
586 | my @x = @{ $h->{a} }; | |
587 | my @x = $h->{a}->@*; | |
588 | ||
589 | The 'postderef_qq' feature extends this, for array and scalar dereference, to | |
590 | working inside of double-quotish interpolations. | |
591 | ||
592 | This feature is available from Perl 5.20 onwards. | |
593 | ||
30d9c59b Z |
594 | =head2 The 'signatures' feature |
595 | ||
596 | B<WARNING>: This feature is still experimental and the implementation may | |
597 | change in future versions of Perl. For this reason, Perl will | |
598 | warn when you use the feature, unless you have explicitly disabled the | |
599 | warning: | |
600 | ||
601 | no warnings "experimental::signatures"; | |
602 | ||
603 | This enables unpacking of subroutine arguments into lexical variables | |
604 | by syntax such as | |
605 | ||
606 | sub foo ($left, $right) { | |
607 | return $left + $right; | |
608 | } | |
609 | ||
610 | See L<perlsub/Signatures> for details. | |
611 | ||
612 | This feature is available from Perl 5.20 onwards. | |
613 | ||
baabe3fb | 614 | =head2 The 'refaliasing' feature |
82848c10 FC |
615 | |
616 | B<WARNING>: This feature is still experimental and the implementation may | |
617 | change in future versions of Perl. For this reason, Perl will | |
618 | warn when you use the feature, unless you have explicitly disabled the | |
619 | warning: | |
620 | ||
baabe3fb | 621 | no warnings "experimental::refaliasing"; |
82848c10 FC |
622 | |
623 | This enables aliasing via assignment to references: | |
624 | ||
625 | \$a = \$b; # $a and $b now point to the same scalar | |
626 | \@a = \@b; # to the same array | |
627 | \%a = \%b; | |
628 | \&a = \&b; | |
629 | foreach \%hash (@array_of_hash_refs) { | |
630 | ... | |
631 | } | |
632 | ||
633 | See L<perlref/Assigning to References> for details. | |
634 | ||
635 | This feature is available from Perl 5.22 onwards. | |
636 | ||
69bcf1d3 FC |
637 | =head1 FEATURE BUNDLES |
638 | ||
639 | It's possible to load multiple features together, using | |
640 | a I<feature bundle>. The name of a feature bundle is prefixed with | |
641 | a colon, to distinguish it from an actual feature. | |
642 | ||
643 | use feature ":5.10"; | |
644 | ||
645 | The following feature bundles are available: | |
646 | ||
647 | bundle features included | |
648 | --------- ----------------- | |
2b3fe414 | 649 | PODTURES |
69bcf1d3 FC |
650 | The C<:default> bundle represents the feature set that is enabled before |
651 | any C<use feature> or C<no feature> declaration. | |
652 | ||
653 | Specifying sub-versions such as the C<0> in C<5.14.0> in feature bundles has | |
654 | no effect. Feature bundles are guaranteed to be the same for all sub-versions. | |
655 | ||
656 | use feature ":5.14.0"; # same as ":5.14" | |
657 | use feature ":5.14.1"; # same as ":5.14" | |
658 | ||
659 | =head1 IMPLICIT LOADING | |
660 | ||
661 | Instead of loading feature bundles by name, it is easier to let Perl do | |
662 | implicit loading of a feature bundle for you. | |
663 | ||
664 | There are two ways to load the C<feature> pragma implicitly: | |
665 | ||
666 | =over 4 | |
667 | ||
668 | =item * | |
669 | ||
670 | By using the C<-E> switch on the Perl command-line instead of C<-e>. | |
671 | That will enable the feature bundle for that version of Perl in the | |
672 | main compilation unit (that is, the one-liner that follows C<-E>). | |
673 | ||
674 | =item * | |
675 | ||
676 | By explicitly requiring a minimum Perl version number for your program, with | |
677 | the C<use VERSION> construct. That is, | |
678 | ||
679 | use v5.10.0; | |
680 | ||
681 | will do an implicit | |
682 | ||
39ec54a5 | 683 | no feature ':all'; |
69bcf1d3 FC |
684 | use feature ':5.10'; |
685 | ||
686 | and so on. Note how the trailing sub-version | |
687 | is automatically stripped from the | |
688 | version. | |
689 | ||
690 | But to avoid portability warnings (see L<perlfunc/use>), you may prefer: | |
691 | ||
692 | use 5.010; | |
693 | ||
694 | with the same effect. | |
695 | ||
696 | If the required version is older than Perl 5.10, the ":default" feature | |
697 | bundle is automatically loaded instead. | |
698 | ||
699 | =back | |
700 | ||
701 | =cut | |
702 | ||
703 | sub import { | |
704 | my $class = shift; | |
36143a0c NC |
705 | |
706 | if (!@_) { | |
69bcf1d3 FC |
707 | croak("No features specified"); |
708 | } | |
36143a0c | 709 | |
d3757264 | 710 | __common(1, @_); |
69bcf1d3 FC |
711 | } |
712 | ||
713 | sub unimport { | |
714 | my $class = shift; | |
715 | ||
39ec54a5 | 716 | # A bare C<no feature> should reset to the default bundle |
69bcf1d3 | 717 | if (!@_) { |
39ec54a5 RS |
718 | $^H &= ~($hint_uni8bit|$hint_mask); |
719 | return; | |
69bcf1d3 FC |
720 | } |
721 | ||
d3757264 NC |
722 | __common(0, @_); |
723 | } | |
724 | ||
725 | ||
726 | sub __common { | |
727 | my $import = shift; | |
0c8d5017 NC |
728 | my $bundle_number = $^H & $hint_mask; |
729 | my $features = $bundle_number != $hint_mask | |
730 | && $feature_bundle{$hint_bundles[$bundle_number >> $hint_shift]}; | |
731 | if ($features) { | |
da5b5421 | 732 | # Features are enabled implicitly via bundle hints. |
d9ee6ccb NC |
733 | # Delete any keys that may be left over from last time. |
734 | delete @^H{ values(%feature) }; | |
735 | $^H |= $hint_mask; | |
736 | for (@$features) { | |
737 | $^H{$feature{$_}} = 1; | |
738 | $^H |= $hint_uni8bit if $_ eq 'unicode_strings'; | |
739 | } | |
da5b5421 | 740 | } |
69bcf1d3 FC |
741 | while (@_) { |
742 | my $name = shift; | |
743 | if (substr($name, 0, 1) eq ":") { | |
744 | my $v = substr($name, 1); | |
745 | if (!exists $feature_bundle{$v}) { | |
746 | $v =~ s/^([0-9]+)\.([0-9]+).[0-9]+$/$1.$2/; | |
747 | if (!exists $feature_bundle{$v}) { | |
748 | unknown_feature_bundle(substr($name, 1)); | |
749 | } | |
750 | } | |
751 | unshift @_, @{$feature_bundle{$v}}; | |
752 | next; | |
753 | } | |
36143a0c | 754 | if (!exists $feature{$name}) { |
69bcf1d3 | 755 | unknown_feature($name); |
69bcf1d3 | 756 | } |
d3757264 NC |
757 | if ($import) { |
758 | $^H{$feature{$name}} = 1; | |
759 | $^H |= $hint_uni8bit if $name eq 'unicode_strings'; | |
760 | } else { | |
69bcf1d3 FC |
761 | delete $^H{$feature{$name}}; |
762 | $^H &= ~ $hint_uni8bit if $name eq 'unicode_strings'; | |
763 | } | |
764 | } | |
765 | } | |
766 | ||
767 | sub unknown_feature { | |
768 | my $feature = shift; | |
769 | croak(sprintf('Feature "%s" is not supported by Perl %vd', | |
770 | $feature, $^V)); | |
771 | } | |
772 | ||
773 | sub unknown_feature_bundle { | |
774 | my $feature = shift; | |
775 | croak(sprintf('Feature bundle "%s" is not supported by Perl %vd', | |
776 | $feature, $^V)); | |
777 | } | |
778 | ||
779 | sub croak { | |
780 | require Carp; | |
781 | Carp::croak(@_); | |
782 | } | |
783 | ||
784 | 1; |