X-Git-Url: https://perl5.git.perl.org/perl5.git/blobdiff_plain/b22bbcf0786b5b4b9edfde241ba29141bb99f219..790f2f66dd0f9e8678a5f5129f984aa0d5baf08c:/lib/feature.pm diff --git a/lib/feature.pm b/lib/feature.pm index a89bc8b..7c60f1d 100644 --- a/lib/feature.pm +++ b/lib/feature.pm @@ -1,40 +1,78 @@ +# -*- buffer-read-only: t -*- +# !!!!!!! DO NOT EDIT THIS FILE !!!!!!! +# This file is built by regen/feature.pl. +# Any changes made here will be lost! + package feature; -our $VERSION = '1.24'; - -# (feature name) => (internal name, used in %^H) -my %feature = ( - say => 'feature_say', - state => 'feature_state', - switch => 'feature_switch', - evalbytes => 'feature_evalbytes', - current_sub => 'feature___SUB__', - unicode_eval => 'feature_unieval', - unicode_strings => 'feature_unicode', +our $VERSION = '1.61'; + +our %feature = ( + fc => 'feature_fc', + isa => 'feature_isa', + say => 'feature_say', + state => 'feature_state', + switch => 'feature_switch', + bitwise => 'feature_bitwise', + indirect => 'feature_indirect', + evalbytes => 'feature_evalbytes', + signatures => 'feature_signatures', + current_sub => 'feature___SUB__', + refaliasing => 'feature_refaliasing', + postderef_qq => 'feature_postderef_qq', + unicode_eval => 'feature_unieval', + declared_refs => 'feature_myref', + unicode_strings => 'feature_unicode', + multidimensional => 'feature_multidimensional', ); -# This gets set (for now) in $^H as well as in %^H, -# for runtime speed of the uc/lc/ucfirst/lcfirst functions. -# See HINT_UNI_8_BIT in perl.h. -our $hint_uni8bit = 0x00000800; - -# NB. the latest bundle must be loaded by the -E switch (see toke.c) - our %feature_bundle = ( - "default" => [], - "5.10" => [qw(say state switch)], - "5.11" => [qw(say state switch unicode_strings)], - "5.15" => [qw(say state switch unicode_strings unicode_eval - evalbytes current_sub)], + "5.10" => [qw(indirect multidimensional say state switch)], + "5.11" => [qw(indirect multidimensional say state switch unicode_strings)], + "5.15" => [qw(current_sub evalbytes fc indirect multidimensional say state switch unicode_eval unicode_strings)], + "5.23" => [qw(current_sub evalbytes fc indirect multidimensional postderef_qq say state switch unicode_eval unicode_strings)], + "5.27" => [qw(bitwise current_sub evalbytes fc indirect multidimensional postderef_qq say state switch unicode_eval unicode_strings)], + "all" => [qw(bitwise current_sub declared_refs evalbytes fc indirect isa multidimensional postderef_qq refaliasing say signatures state switch unicode_eval unicode_strings)], + "default" => [qw(indirect multidimensional)], ); -# Each of these is the same as the previous bundle -for(12...14, 16) { - $feature_bundle{"5.$_"} = $feature_bundle{"5.".($_-1)} -} - -# special case +$feature_bundle{"5.12"} = $feature_bundle{"5.11"}; +$feature_bundle{"5.13"} = $feature_bundle{"5.11"}; +$feature_bundle{"5.14"} = $feature_bundle{"5.11"}; +$feature_bundle{"5.16"} = $feature_bundle{"5.15"}; +$feature_bundle{"5.17"} = $feature_bundle{"5.15"}; +$feature_bundle{"5.18"} = $feature_bundle{"5.15"}; +$feature_bundle{"5.19"} = $feature_bundle{"5.15"}; +$feature_bundle{"5.20"} = $feature_bundle{"5.15"}; +$feature_bundle{"5.21"} = $feature_bundle{"5.15"}; +$feature_bundle{"5.22"} = $feature_bundle{"5.15"}; +$feature_bundle{"5.24"} = $feature_bundle{"5.23"}; +$feature_bundle{"5.25"} = $feature_bundle{"5.23"}; +$feature_bundle{"5.26"} = $feature_bundle{"5.23"}; +$feature_bundle{"5.28"} = $feature_bundle{"5.27"}; +$feature_bundle{"5.29"} = $feature_bundle{"5.27"}; +$feature_bundle{"5.30"} = $feature_bundle{"5.27"}; +$feature_bundle{"5.31"} = $feature_bundle{"5.27"}; +$feature_bundle{"5.32"} = $feature_bundle{"5.27"}; +$feature_bundle{"5.33"} = $feature_bundle{"5.27"}; +$feature_bundle{"5.34"} = $feature_bundle{"5.27"}; $feature_bundle{"5.9.5"} = $feature_bundle{"5.10"}; +my %noops = ( + postderef => 1, + lexical_subs => 1, +); +my %removed = ( + array_base => 1, +); + +our $hint_shift = 26; +our $hint_mask = 0x3c000000; +our @hint_bundles = qw( default 5.10 5.11 5.15 5.23 5.27 ); + +# This gets set (for now) in $^H as well as in %^H, +# for runtime speed of the uc/lc/ucfirst/lcfirst functions. +# See HINT_UNI_8_BIT in perl.h. +our $hint_uni8bit = 0x00000800; # TODO: # - think about versioned features (use feature switch => 2) @@ -71,7 +109,7 @@ pragma.) =head2 Lexical effect Like other pragmas (C, for example), features have a lexical -effect. C will only make the feature "foo" available +effect. C will only make the feature "foo" available from that point to the end of the enclosing block. { @@ -93,13 +131,14 @@ has lexical effect. } say "Yet it is here."; -C with no features specified will turn off all features. +C with no features specified will reset to the default group. To +disable I features (an unusual request!) use C. =head1 AVAILABLE FEATURES =head2 The 'say' feature -C tells the compiler to enable the Perl 6 style +C tells the compiler to enable the Raku-inspired C function. See L for details. @@ -117,85 +156,241 @@ This feature is available starting with Perl 5.10. =head2 The 'switch' feature -C tells the compiler to enable the Perl 6 +B: Because the L is +experimental, Perl will warn when you use this feature, unless you have +explicitly disabled the warning: + + no warnings "experimental::smartmatch"; + +C tells the compiler to enable the Raku given/when construct. -See L for details. +See L for details. This feature is available starting with Perl 5.10. =head2 The 'unicode_strings' feature -C tells the compiler to use Unicode semantics +C tells the compiler to use Unicode rules in all string operations executed within its scope (unless they are also within the scope of either C or C). The same applies to all regular expressions compiled within the scope, even if executed outside -it. +it. It does not change the internal representation of strings, but only how +they are interpreted. C tells the compiler to use the traditional -Perl semantics wherein the native character set semantics is used unless it is +Perl rules wherein the native character set rules is used unless it is clear to Perl that Unicode is desired. This can lead to some surprises when the behavior suddenly changes. (See L for details.) For this reason, if you are potentially using Unicode in your program, the C subpragma is B recommended. -This feature is available starting with Perl 5.12, but was not fully -implemented until Perl 5.14. +This feature is available starting with Perl 5.12; was almost fully +implemented in Perl 5.14; and extended in Perl 5.16 to cover C; +was extended further in Perl 5.26 to cover L; and was extended again in Perl 5.28 to +cover L. =head2 The 'unicode_eval' and 'evalbytes' features -Under the C feature, Perl's C function, when passed a -string, will evaluate it as a string of characters, ignoring any -C declarations. C exists to declare the encoding of -the script, which only makes sense for a stream of bytes, not a string of -characters. Source filters are forbidden, as they also really only make -sense on strings of bytes. Any attempt to activate a source filter will -result in an error. +Together, these two features are intended to replace the legacy string +C function, which behaves problematically in some instances. They are +available starting with Perl 5.16, and are enabled by default by a +S> or higher declaration. -The C feature enables the C keyword, which evaluates -the argument passed to it as a string of bytes. It dies if the string -contains any characters outside the 8-bit range. Source filters work -within C: they apply to the contents of the string being -evaluated. +C changes the behavior of plain string C to work more +consistently, especially in the Unicode world. Certain (mis)behaviors +couldn't be changed without breaking some things that had come to rely on +them, so the feature can be enabled and disabled. Details are at +L. -Together, these two features are intended to replace the historical C -function, which has (at least) two bugs in it, that cannot easily be fixed -without breaking existing programs: +C is like string C, but operating on a byte stream that is +not UTF-8 encoded. Details are at L. Without a +S> nor a S> (or higher) declaration in +the current scope, you can still access it by instead writing +C. -=over +=head2 The 'current_sub' feature -=item * +This provides the C<__SUB__> token that returns a reference to the current +subroutine or C outside of a subroutine. -C behaves differently depending on the internal encoding of the -string, sometimes treating its argument as a string of bytes, and sometimes -as a string of characters. +This feature is available starting with Perl 5.16. -=item * +=head2 The 'array_base' feature -Source filters activated within C leak out into whichever I -scope is currently being compiled. To give an example with the CPAN module -L: +This feature supported the legacy C<$[> variable. See L. +It was on by default but disabled under C (see +L, below) and unavailable since perl 5.30. - BEGIN { eval "use Semi::Semicolons; # not filtered here " } - # filtered here! +This feature is available under this name starting with Perl 5.16. In +previous versions, it was simply on all the time, and this pragma knew +nothing about it. -C fixes that to work the way one would expect: +=head2 The 'fc' feature - use feature "evalbytes"; - BEGIN { evalbytes "use Semi::Semicolons; # filtered " } - # not filtered +C tells the compiler to enable the C function, +which implements Unicode casefolding. -=back +See L for details. -These two features are available starting with Perl 5.16. +This feature is available from Perl 5.16 onwards. -=head2 The 'current_sub' feature +=head2 The 'lexical_subs' feature -This provides the C<__SUB__> token that returns a reference to the current -subroutine or C outside of a subroutine. +In Perl versions prior to 5.26, this feature enabled +declaration of subroutines via C, C +and C syntax. See L for details. -This feature is available starting with Perl 5.16. +This feature is available from Perl 5.18 onwards. From Perl 5.18 to 5.24, +it was classed as experimental, and Perl emitted a warning for its +usage, except when explicitly disabled: + + no warnings "experimental::lexical_subs"; + +As of Perl 5.26, use of this feature no longer triggers a warning, though +the C warning category still exists (for +compatibility with code that disables it). In addition, this syntax is +not only no longer experimental, but it is enabled for all Perl code, +regardless of what feature declarations are in scope. + +=head2 The 'postderef' and 'postderef_qq' features + +The 'postderef_qq' feature extends the applicability of L so that postfix array +and scalar dereference are available in double-quotish interpolations. For +example, it makes the following two statements equivalent: + + my $s = "[@{ $h->{a} }]"; + my $s = "[$h->{a}->@*]"; + +This feature is available from Perl 5.20 onwards. In Perl 5.20 and 5.22, it +was classed as experimental, and Perl emitted a warning for its +usage, except when explicitly disabled: + + no warnings "experimental::postderef"; + +As of Perl 5.24, use of this feature no longer triggers a warning, though +the C warning category still exists (for +compatibility with code that disables it). + +The 'postderef' feature was used in Perl 5.20 and Perl 5.22 to enable +postfix dereference syntax outside double-quotish interpolations. In those +versions, using it triggered the C warning in the +same way as the 'postderef_qq' feature did. As of Perl 5.24, this syntax is +not only no longer experimental, but it is enabled for all Perl code, +regardless of what feature declarations are in scope. + +=head2 The 'signatures' feature + +B: This feature is still experimental and the implementation may +change in future versions of Perl. For this reason, Perl will +warn when you use the feature, unless you have explicitly disabled the +warning: + + no warnings "experimental::signatures"; + +This enables unpacking of subroutine arguments into lexical variables +by syntax such as + + sub foo ($left, $right) { + return $left + $right; + } + +See L for details. + +This feature is available from Perl 5.20 onwards. + +=head2 The 'refaliasing' feature + +B: This feature is still experimental and the implementation may +change in future versions of Perl. For this reason, Perl will +warn when you use the feature, unless you have explicitly disabled the +warning: + + no warnings "experimental::refaliasing"; + +This enables aliasing via assignment to references: + + \$a = \$b; # $a and $b now point to the same scalar + \@a = \@b; # to the same array + \%a = \%b; + \&a = \&b; + foreach \%hash (@array_of_hash_refs) { + ... + } + +See L for details. + +This feature is available from Perl 5.22 onwards. + +=head2 The 'bitwise' feature + +This makes the four standard bitwise operators (C<& | ^ ~>) treat their +operands consistently as numbers, and introduces four new dotted operators +(C<&. |. ^. ~.>) that treat their operands consistently as strings. The +same applies to the assignment variants (C<&= |= ^= &.= |.= ^.=>). + +See L for details. + +This feature is available from Perl 5.22 onwards. Starting in Perl 5.28, +C will enable the feature. Before 5.28, it was still +experimental and would emit a warning in the "experimental::bitwise" +category. + +=head2 The 'declared_refs' feature + +B: This feature is still experimental and the implementation may +change in future versions of Perl. For this reason, Perl will +warn when you use the feature, unless you have explicitly disabled the +warning: + + no warnings "experimental::declared_refs"; + +This allows a reference to a variable to be declared with C, C, +our C, or localized with C. It is intended mainly for use in +conjunction with the "refaliasing" feature. See L for examples. + +This feature is available from Perl 5.26 onwards. + +=head2 The 'isa' feature + +This allows the use of the C infix operator, which tests whether the +scalar given by the left operand is an object of the class given by the +right operand. See L for more details. + +This feature is available from Perl 5.32 onwards. + +=head2 The 'indirect' feature + +This feature allows the use of L for method calls, e.g. C. It is enabled by default, but can be turned off to +disallow indirect object syntax. + +This feature is available under this name from Perl 5.32 onwards. In +previous versions, it was simply on all the time. To disallow (or +warn on) indirect object syntax on older Perls, see the L +CPAN module. + +=head2 The 'multidimensional' feature + +This feature enables multidimensional array emulation, a perl 4 (or +earlier) feature that was used to emulate multidimensional arrays with +hashes. This works by converting code like C<< $foo{$x, y} >> into +C<< $foo{join($;, $x, $y} >>. It is enabled by default, but can be +turned off to disable multidimensional array emulation. + +When this feature is disabled the syntax that is normally replaced +will report a compilation error. + +This feature is available under this name from Perl 5.34 onwards. In +previous versions, it was simply on all the time. + +You can use the L module on CPAN to disable +multidimensional array emulation for older versions of Perl. =head1 FEATURE BUNDLES @@ -209,19 +404,58 @@ The following feature bundles are available: bundle features included --------- ----------------- - :default none + :default indirect multidimensional + + :5.10 indirect multidimensional say state switch + + :5.12 indirect multidimensional say state switch + unicode_strings + + :5.14 indirect multidimensional say state switch + unicode_strings + + :5.16 current_sub evalbytes fc indirect + multidimensional say state switch + unicode_eval unicode_strings + + :5.18 current_sub evalbytes fc indirect + multidimensional say state switch + unicode_eval unicode_strings + + :5.20 current_sub evalbytes fc indirect + multidimensional say state switch + unicode_eval unicode_strings + + :5.22 current_sub evalbytes fc indirect + multidimensional say state switch + unicode_eval unicode_strings + + :5.24 current_sub evalbytes fc indirect + multidimensional postderef_qq say state + switch unicode_eval unicode_strings + + :5.26 current_sub evalbytes fc indirect + multidimensional postderef_qq say state + switch unicode_eval unicode_strings - :5.10 say state switch + :5.28 bitwise current_sub evalbytes fc indirect + multidimensional postderef_qq say state + switch unicode_eval unicode_strings - :5.12 say state switch unicode_strings + :5.30 bitwise current_sub evalbytes fc indirect + multidimensional postderef_qq say state + switch unicode_eval unicode_strings - :5.14 say state switch unicode_strings + :5.32 bitwise current_sub evalbytes fc indirect + multidimensional postderef_qq say state + switch unicode_eval unicode_strings - :5.16 say state switch unicode_strings - unicode_eval evalbytes current_sub + :5.34 bitwise current_sub evalbytes fc indirect + multidimensional postderef_qq say state + switch unicode_eval unicode_strings -The empty C<:default> bundle is provided for future -backwards-compatibility when using L. +The C<:default> bundle represents the feature set that is enabled before +any C or C declaration. Specifying sub-versions such as the C<0> in C<5.14.0> in feature bundles has no effect. Feature bundles are guaranteed to be the same for all sub-versions. @@ -253,7 +487,7 @@ the C construct. That is, will do an implicit - no feature; + no feature ':all'; use feature ':5.10'; and so on. Note how the trailing sub-version @@ -267,50 +501,53 @@ But to avoid portability warnings (see L), you may prefer: with the same effect. If the required version is older than Perl 5.10, the ":default" feature -bundle is automatically loaded instead. It is currently empty and has no -effect, but may be used in the future to support backwards -compatibility. +bundle is automatically loaded instead. + +Unlike C, saying C (or any higher version) +also does the equivalent of C; see L for details. =back =cut sub import { - my $class = shift; - if (@_ == 0) { + shift; + + if (!@_) { croak("No features specified"); } - while (@_) { - my $name = shift(@_); - if (substr($name, 0, 1) eq ":") { - my $v = substr($name, 1); - if (!exists $feature_bundle{$v}) { - $v =~ s/^([0-9]+)\.([0-9]+).[0-9]+$/$1.$2/; - if (!exists $feature_bundle{$v}) { - unknown_feature_bundle(substr($name, 1)); - } - } - unshift @_, @{$feature_bundle{$v}}; - next; - } - if (!exists $feature{$name}) { - unknown_feature($name); - } - $^H{$feature{$name}} = 1; - $^H |= $hint_uni8bit if $name eq 'unicode_strings'; - } + + __common(1, @_); } sub unimport { - my $class = shift; + shift; - # A bare C should disable *all* features + # A bare C should reset to the default bundle if (!@_) { - delete @^H{ values(%feature) }; - $^H &= ~ $hint_uni8bit; - return; + $^H &= ~($hint_uni8bit|$hint_mask); + return; } + __common(0, @_); +} + + +sub __common { + my $import = shift; + my $bundle_number = $^H & $hint_mask; + my $features = $bundle_number != $hint_mask + && $feature_bundle{$hint_bundles[$bundle_number >> $hint_shift]}; + if ($features) { + # Features are enabled implicitly via bundle hints. + # Delete any keys that may be left over from last time. + delete @^H{ values(%feature) }; + $^H |= $hint_mask; + for (@$features) { + $^H{$feature{$_}} = 1; + $^H |= $hint_uni8bit if $_ eq 'unicode_strings'; + } + } while (@_) { my $name = shift; if (substr($name, 0, 1) eq ":") { @@ -324,10 +561,19 @@ sub unimport { unshift @_, @{$feature_bundle{$v}}; next; } - if (!exists($feature{$name})) { + if (!exists $feature{$name}) { + if (exists $noops{$name}) { + next; + } + if (!$import && exists $removed{$name}) { + next; + } unknown_feature($name); } - else { + if ($import) { + $^H{$feature{$name}} = 1; + $^H |= $hint_uni8bit if $name eq 'unicode_strings'; + } else { delete $^H{$feature{$name}}; $^H &= ~ $hint_uni8bit if $name eq 'unicode_strings'; } @@ -352,3 +598,5 @@ sub croak { } 1; + +# ex: set ro: