use 5.008; package base; use strict 'vars'; our $VERSION = '2.27'; $VERSION =~ tr/_//d; # simplest way to avoid indexing of the package: no package statement sub base::__inc::unhook { @INC = grep !(ref eq 'CODE' && $_ == $_[0]), @INC } # instance is blessed array of coderefs to be removed from @INC at scope exit sub base::__inc::scope_guard::DESTROY { base::__inc::unhook $_ for @{$_[0]} } # constant.pm is slow sub SUCCESS () { 1 } sub PUBLIC () { 2**0 } sub PRIVATE () { 2**1 } sub INHERITED () { 2**2 } sub PROTECTED () { 2**3 } my $Fattr = \%fields::attr; sub has_fields { my($base) = shift; my $fglob = ${"$base\::"}{FIELDS}; return( ($fglob && 'GLOB' eq ref($fglob) && *$fglob{HASH}) ? 1 : 0 ); } sub has_attr { my($proto) = shift; my($class) = ref $proto || $proto; return exists $Fattr->{$class}; } sub get_attr { $Fattr->{$_[0]} = [1] unless $Fattr->{$_[0]}; return $Fattr->{$_[0]}; } if ($] < 5.009) { *get_fields = sub { # Shut up a possible typo warning. () = \%{$_[0].'::FIELDS'}; my $f = \%{$_[0].'::FIELDS'}; # should be centralized in fields? perhaps # fields::mk_FIELDS_be_OK. Peh. As long as %{ $package . '::FIELDS' } # is used here anyway, it doesn't matter. bless $f, 'pseudohash' if (ref($f) ne 'pseudohash'); return $f; } } else { *get_fields = sub { # Shut up a possible typo warning. () = \%{$_[0].'::FIELDS'}; return \%{$_[0].'::FIELDS'}; } } if ($] < 5.008) { *_module_to_filename = sub { (my $fn = $_[0]) =~ s!::!/!g; $fn .= '.pm'; return $fn; } } else { *_module_to_filename = sub { (my $fn = $_[0]) =~ s!::!/!g; $fn .= '.pm'; utf8::encode($fn); return $fn; } } sub import { my $class = shift; return SUCCESS unless @_; # List of base classes from which we will inherit %FIELDS. my $fields_base; my $inheritor = caller(0); my @bases; foreach my $base (@_) { if ( $inheritor eq $base ) { warn "Class '$inheritor' tried to inherit from itself\n"; } next if grep $_->isa($base), ($inheritor, @bases); # Following blocks help isolate $SIG{__DIE__} and @INC changes { my $sigdie; { local $SIG{__DIE__}; my $fn = _module_to_filename($base); my $dot_hidden; eval { my $guard; if ($INC[-1] eq '.' && %{"$base\::"}) { # So: the package already exists => this an optional load # And: there is a dot at the end of @INC => we want to hide it # However: we only want to hide it during our *own* require() # (i.e. without affecting nested require()s). # So we add a hook to @INC whose job is to hide the dot, but which # first checks checks the callstack depth, because within nested # require()s the callstack is deeper. # Since CORE::GLOBAL::require makes it unknowable in advance what # the exact relevant callstack depth will be, we have to record it # inside a hook. So we put another hook just for that at the front # of @INC, where it's guaranteed to run -- immediately. # The dot-hiding hook does its job by sitting directly in front of # the dot and removing itself from @INC when reached. This causes # the dot to move up one index in @INC, causing the loop inside # pp_require() to skip it. # Loaded coded may disturb this precise arrangement, but that's OK # because the hook is inert by that time. It is only active during # the top-level require(), when @INC is in our control. The only # possible gotcha is if other hooks already in @INC modify @INC in # some way during that initial require(). # Note that this jiggery hookery works just fine recursively: if # a module loaded via base.pm uses base.pm itself, there will be # one pair of hooks in @INC per base::import call frame, but the # pairs from different nestings do not interfere with each other. my $lvl; unshift @INC, sub { return if defined $lvl; 1 while defined caller ++$lvl; () }; splice @INC, -1, 0, sub { return if defined caller $lvl; ++$dot_hidden, &base::__inc::unhook; () }; $guard = bless [ @INC[0,-2] ], 'base::__inc::scope_guard'; } require $fn }; if ($dot_hidden && (my @fn = grep -e && !( -d _ || -b _ ), $fn.'c', $fn)) { require Carp; Carp::croak(<<ERROR); Base class package "$base" is not empty but "$fn[0]" exists in the current directory. To help avoid security issues, base.pm now refuses to load optional modules from the current working directory when it is the last entry in \@INC. If your software worked on previous versions of Perl, the best solution is to use FindBin to detect the path properly and to add that path to \@INC. As a last resort, you can re-enable looking in the current working directory by adding "use lib '.'" to your code. ERROR } # Only ignore "Can't locate" errors from our eval require. # Other fatal errors (syntax etc) must be reported. # # changing the check here is fragile - if the check # here isn't catching every error you want, you should # probably be using parent.pm, which doesn't try to # guess whether require is needed or failed, # see [perl #118561] die if $@ && $@ !~ /^Can't locate \Q$fn\E .*? at .* line [0-9]+(?:, <[^>]*> (?:line|chunk) [0-9]+)?\.\n\z/s || $@ =~ /Compilation failed in require at .* line [0-9]+(?:, <[^>]*> (?:line|chunk) [0-9]+)?\.\n\z/; unless (%{"$base\::"}) { require Carp; local $" = " "; Carp::croak(<<ERROR); Base class package "$base" is empty. (Perhaps you need to 'use' the module which defines that package first, or make that module available in \@INC (\@INC contains: @INC). ERROR } $sigdie = $SIG{__DIE__} || undef; } # Make sure a global $SIG{__DIE__} makes it out of the localization. $SIG{__DIE__} = $sigdie if defined $sigdie; } push @bases, $base; if ( has_fields($base) || has_attr($base) ) { # No multiple fields inheritance *suck* if ($fields_base) { require Carp; Carp::croak("Can't multiply inherit fields"); } else { $fields_base = $base; } } } # Save this until the end so it's all or nothing if the above loop croaks. push @{"$inheritor\::ISA"}, @bases; if( defined $fields_base ) { inherit_fields($inheritor, $fields_base); } } sub inherit_fields { my($derived, $base) = @_; return SUCCESS unless $base; my $battr = get_attr($base); my $dattr = get_attr($derived); my $dfields = get_fields($derived); my $bfields = get_fields($base); $dattr->[0] = @$battr; if( keys %$dfields ) { warn <<"END"; $derived is inheriting from $base but already has its own fields! This will cause problems. Be sure you use base BEFORE declaring fields. END } # Iterate through the base's fields adding all the non-private # ones to the derived class. Hang on to the original attribute # (Public, Private, etc...) and add Inherited. # This is all too complicated to do efficiently with add_fields(). while (my($k,$v) = each %$bfields) { my $fno; if ($fno = $dfields->{$k} and $fno != $v) { require Carp; Carp::croak ("Inherited fields can't override existing fields"); } if( $battr->[$v] & PRIVATE ) { $dattr->[$v] = PRIVATE | INHERITED; } else { $dattr->[$v] = INHERITED | $battr->[$v]; $dfields->{$k} = $v; } } foreach my $idx (1..$#{$battr}) { next if defined $dattr->[$idx]; $dattr->[$idx] = $battr->[$idx] & INHERITED; } } 1; __END__ =head1 NAME base - Establish an ISA relationship with base classes at compile time =head1 SYNOPSIS package Baz; use base qw(Foo Bar); =head1 DESCRIPTION Unless you are using the C<fields> pragma, consider this module discouraged in favor of the lighter-weight C<parent>. Allows you to both load one or more modules, while setting up inheritance from those modules at the same time. Roughly similar in effect to package Baz; BEGIN { require Foo; require Bar; push @ISA, qw(Foo Bar); } When C<base> tries to C<require> a module, it will not die if it cannot find the module's file, but will die on any other error. After all this, should your base class be empty, containing no symbols, C<base> will die. This is useful for inheriting from classes in the same file as yourself but where the filename does not match the base module name, like so: # in Bar.pm package Foo; sub exclaim { "I can have such a thing?!" } package Bar; use base "Foo"; There is no F<Foo.pm>, but because C<Foo> defines a symbol (the C<exclaim> subroutine), C<base> will not die when the C<require> fails to load F<Foo.pm>. C<base> will also initialize the fields if one of the base classes has it. Multiple inheritance of fields is B<NOT> supported, if two or more base classes each have inheritable fields the 'base' pragma will croak. See L<fields> for a description of this feature. The base class' C<import> method is B<not> called. =head1 DIAGNOSTICS =over 4 =item Base class package "%s" is empty. base.pm was unable to require the base package, because it was not found in your path. =item Class 'Foo' tried to inherit from itself Attempting to inherit from yourself generates a warning. package Foo; use base 'Foo'; =back =head1 HISTORY This module was introduced with Perl 5.004_04. =head1 CAVEATS Due to the limitations of the implementation, you must use base I<before> you declare any of your own fields. =head1 SEE ALSO L<fields> =cut