[perl5.git] / t / op / sort.t

#!./perl

BEGIN {
    chdir 't' if -d 't';
    @INC = qw(. ../lib); require 'test.pl';
}
use warnings;
plan( tests => 144 );

# these shouldn't hang
{
    no warnings;
    sort { for ($_ = 0;; $_++) {} } @a;
    sort { while(1) {}            } @a;
    sort { while(1) { last; }     } @a;
    sort { while(0) { last; }     } @a;

    # Change 26011: Re: A surprising segfault
    map scalar(sort(+())), ('')x68;
}

sub Backwards { $a lt $b ? 1 : $a gt $b ? -1 : 0 }
sub Backwards_stacked($$) { my($a,$b) = @_; $a lt $b ? 1 : $a gt $b ? -1 : 0 }
sub Backwards_other { $a lt $b ? 1 : $a gt $b ? -1 : 0 }

my $upperfirst = 'A' lt 'a';

# Beware: in future this may become hairier because of possible
# collation complications: qw(A a B b) can be sorted at least as
# any of the following
#
#	A a B b
#	A B a b
#	a b A B
#	a A b B
#
# All the above orders make sense.
#
# That said, EBCDIC sorts all small letters first, as opposed
# to ASCII which sorts all big letters first.

@harry = ('dog','cat','x','Cain','Abel');
@george = ('gone','chased','yz','punished','Axed');

$x = join('', sort @harry);
$expected = $upperfirst ? 'AbelCaincatdogx' : 'catdogxAbelCain';

cmp_ok($x,'eq',$expected,'upper first 1');

$x = join('', sort( Backwards @harry));
$expected = $upperfirst ? 'xdogcatCainAbel' : 'CainAbelxdogcat';

cmp_ok($x,'eq',$expected,'upper first 2');

$x = join('', sort( Backwards_stacked @harry));
$expected = $upperfirst ? 'xdogcatCainAbel' : 'CainAbelxdogcat';

cmp_ok($x,'eq',$expected,'upper first 3');

$x = join('', sort @george, 'to', @harry);
$expected = $upperfirst ?
    'AbelAxedCaincatchaseddoggonepunishedtoxyz' :
    'catchaseddoggonepunishedtoxyzAbelAxedCain' ;

cmp_ok($x,'eq',$expected,'upper first 4');
$" = ' ';
@a = ();
@b = reverse @a;
cmp_ok("@b",'eq',"",'reverse 1');

@a = (1);
@b = reverse @a;
cmp_ok("@b",'eq',"1",'reverse 2');

@a = (1,2);
@b = reverse @a;
cmp_ok("@b",'eq',"2 1",'reverse 3');

@a = (1,2,3);
@b = reverse @a;
cmp_ok("@b",'eq',"3 2 1",'reverse 4');

@a = (1,2,3,4);
@b = reverse @a;
cmp_ok("@b",'eq',"4 3 2 1",'reverse 5');

@a = (10,2,3,4);
@b = sort {$a <=> $b;} @a;
cmp_ok("@b",'eq',"2 3 4 10",'sort numeric');

$sub = 'Backwards';
$x = join('', sort $sub @harry);
$expected = $upperfirst ? 'xdogcatCainAbel' : 'CainAbelxdogcat';

cmp_ok($x,'eq',$expected,'sorter sub name in var 1');

$sub = 'Backwards_stacked';
$x = join('', sort $sub @harry);
$expected = $upperfirst ? 'xdogcatCainAbel' : 'CainAbelxdogcat';

cmp_ok($x,'eq',$expected,'sorter sub name in var 2');

# literals, combinations

@b = sort (4,1,3,2);
cmp_ok("@b",'eq','1 2 3 4','just sort');


@b = sort grep { $_ } (4,1,3,2);
cmp_ok("@b",'eq','1 2 3 4','grep then sort');


@b = sort map { $_ } (4,1,3,2);
cmp_ok("@b",'eq','1 2 3 4','map then sort');


@b = sort reverse (4,1,3,2);
cmp_ok("@b",'eq','1 2 3 4','reverse then sort');


sub twoface { no warnings 'redefine'; *twoface = sub { $a <=> $b }; &twoface }
eval { @b = sort twoface 4,1,3,2 };
cmp_ok("@b",'eq','1 2 3 4','redefine sort sub inside the sort sub');


eval { no warnings 'redefine'; *twoface = sub { &Backwards } };
ok(!$@,"redefining sort subs outside the sort \$@=[$@]");

eval { @b = sort twoface 4,1,3,2 };
cmp_ok("@b",'eq','4 3 2 1','twoface redefinition');

{
  no warnings 'redefine';
  *twoface = sub { *twoface = *Backwards_other; $a <=> $b };
}

eval { @b = sort twoface 4,1,9,5 };
ok(($@ eq "" && "@b" eq "1 4 5 9"),'redefinition should not take effect during the sort');

{
  no warnings 'redefine';
  *twoface = sub {
                 eval 'sub twoface { $a <=> $b }';
		 die($@ eq "" ? "good\n" : "bad\n");
		 $a <=> $b;
	       };
}
eval { @b = sort twoface 4,1 };
cmp_ok(substr($@,0,4), 'eq', 'good', 'twoface eval');

eval <<'CODE';
    my @result = sort main'Backwards 'one', 'two';
CODE
cmp_ok($@,'eq','',q(old skool package));

eval <<'CODE';
    # "sort 'one', 'two'" should not try to parse "'one" as a sort sub
    my @result = sort 'one', 'two';
CODE
cmp_ok($@,'eq','',q(one is not a sub));

{
  my $sortsub = \&Backwards;
  my $sortglob = *Backwards;
  my $sortglobr = \*Backwards;
  my $sortname = 'Backwards';
  @b = sort $sortsub 4,1,3,2;
  cmp_ok("@b",'eq','4 3 2 1','sortname 1');
  @b = sort $sortglob 4,1,3,2;
  cmp_ok("@b",'eq','4 3 2 1','sortname 2');
  @b = sort $sortname 4,1,3,2;
  cmp_ok("@b",'eq','4 3 2 1','sortname 3');
  @b = sort $sortglobr 4,1,3,2;
  cmp_ok("@b",'eq','4 3 2 1','sortname 4');
}

{
  my $sortsub = \&Backwards_stacked;
  my $sortglob = *Backwards_stacked;
  my $sortglobr = \*Backwards_stacked;
  my $sortname = 'Backwards_stacked';
  @b = sort $sortsub 4,1,3,2;
  cmp_ok("@b",'eq','4 3 2 1','sortname 5');
  @b = sort $sortglob 4,1,3,2;
  cmp_ok("@b",'eq','4 3 2 1','sortname 6');
  @b = sort $sortname 4,1,3,2;
  cmp_ok("@b",'eq','4 3 2 1','sortname 7');
  @b = sort $sortglobr 4,1,3,2;
  cmp_ok("@b",'eq','4 3 2 1','sortname 8');
}

{
  local $sortsub = \&Backwards;
  local $sortglob = *Backwards;
  local $sortglobr = \*Backwards;
  local $sortname = 'Backwards';
  @b = sort $sortsub 4,1,3,2;
  cmp_ok("@b",'eq','4 3 2 1','sortname local 1');
  @b = sort $sortglob 4,1,3,2;
  cmp_ok("@b",'eq','4 3 2 1','sortname local 2');
  @b = sort $sortname 4,1,3,2;
  cmp_ok("@b",'eq','4 3 2 1','sortname local 3');
  @b = sort $sortglobr 4,1,3,2;
  cmp_ok("@b",'eq','4 3 2 1','sortname local 4');
}

{
  local $sortsub = \&Backwards_stacked;
  local $sortglob = *Backwards_stacked;
  local $sortglobr = \*Backwards_stacked;
  local $sortname = 'Backwards_stacked';
  @b = sort $sortsub 4,1,3,2;
  cmp_ok("@b",'eq','4 3 2 1','sortname local 5');
  @b = sort $sortglob 4,1,3,2;
  cmp_ok("@b",'eq','4 3 2 1','sortname local 6');
  @b = sort $sortname 4,1,3,2;
  cmp_ok("@b",'eq','4 3 2 1','sortname local 7');
  @b = sort $sortglobr 4,1,3,2;
  cmp_ok("@b",'eq','4 3 2 1','sortname local 8');
}

## exercise sort builtins... ($a <=> $b already tested)
@a = ( 5, 19, 1996, 255, 90 );
@b = sort {
    my $dummy;		# force blockness
    return $b <=> $a
} @a;
cmp_ok("@b",'eq','1996 255 90 19 5','force blockness');

$x = join('', sort { $a cmp $b } @harry);
$expected = $upperfirst ? 'AbelCaincatdogx' : 'catdogxAbelCain';
cmp_ok($x,'eq',$expected,'a cmp b');

$x = join('', sort { $b cmp $a } @harry);
$expected = $upperfirst ? 'xdogcatCainAbel' : 'CainAbelxdogcat';
cmp_ok($x,'eq',$expected,'b cmp a');

{
    use integer;
    @b = sort { $a <=> $b } @a;
    cmp_ok("@b",'eq','5 19 90 255 1996','integer a <=> b');

    @b = sort { $b <=> $a } @a;
    cmp_ok("@b",'eq','1996 255 90 19 5','integer b <=> a');

    $x = join('', sort { $a cmp $b } @harry);
    $expected = $upperfirst ? 'AbelCaincatdogx' : 'catdogxAbelCain';
    cmp_ok($x,'eq',$expected,'integer a cmp b');

    $x = join('', sort { $b cmp $a } @harry);
    $expected = $upperfirst ? 'xdogcatCainAbel' : 'CainAbelxdogcat';
    cmp_ok($x,'eq',$expected,'integer b cmp a');

}


$x = join('', sort { $a <=> $b } 3, 1, 2);
cmp_ok($x,'eq','123',q(optimized-away comparison block doesn't take any other arguments away with it));

# test sorting in non-main package
package Foo;
@a = ( 5, 19, 1996, 255, 90 );
@b = sort { $b <=> $a } @a;
main::cmp_ok("@b",'eq','1996 255 90 19 5','not in main:: 1');


@b = sort main::Backwards_stacked @a;
main::cmp_ok("@b",'eq','90 5 255 1996 19','not in main:: 2');


# check if context for sort arguments is handled right


sub test_if_list {
    my $gimme = wantarray;
    main::is($gimme,1,'wantarray 1');


}
my $m = sub { $a <=> $b };

sub cxt_one { sort $m test_if_list() }
cxt_one();
sub cxt_two { sort { $a <=> $b } test_if_list() }
cxt_two();
sub cxt_three { sort &test_if_list() }
cxt_three();

sub test_if_scalar {
    my $gimme = wantarray;
    main::is(!($gimme or !defined($gimme)),1,'wantarray 2');


}

$m = \&test_if_scalar;
sub cxt_four { sort $m 1,2 }
@x = cxt_four();
sub cxt_five { sort { test_if_scalar($a,$b); } 1,2 }
@x = cxt_five();
sub cxt_six { sort test_if_scalar 1,2 }
@x = cxt_six();

# test against a reentrancy bug
{
    package Bar;
    sub compare { $a cmp $b }
    sub reenter { my @force = sort compare qw/a b/ }
}
{
    my($def, $init) = (0, 0);
    @b = sort {
	$def = 1 if defined $Bar::a;
	Bar::reenter() unless $init++;
	$a <=> $b
    } qw/4 3 1 2/;
    main::cmp_ok("@b",'eq','1 2 3 4','reenter 1');

    main::ok(!$def,'reenter 2');
}


{
    sub routine { "one", "two" };
    @a = sort(routine(1));
    main::cmp_ok("@a",'eq',"one two",'bug id 19991001.003');
}


#my $test = 59;
sub ok { main::cmp_ok($_[0],'eq',$_[1],$_[2]);
#    print "not " unless $_[0] eq $_[1];
#    print "ok $test - $_[2]\n";
#    print "#[$_[0]] ne [$_[1]]\n" unless $_[0] eq $_[1];
#    $test++;
}

# check for in-place optimisation of @a = sort @a
{
    my ($r1,$r2,@a);
    our @g;
    @g = (3,2,1); $r1 = \$g[2]; @g = sort @g; $r2 = \$g[0];
    ok "$r1-@g", "$r2-1 2 3", "inplace sort of global";

    @a = qw(b a c); $r1 = \$a[1]; @a = sort @a; $r2 = \$a[0];
    ok "$r1-@a", "$r2-a b c", "inplace sort of lexical";

    @g = (2,3,1); $r1 = \$g[1]; @g = sort { $b <=> $a } @g; $r2 = \$g[0];
    ok "$r1-@g", "$r2-3 2 1", "inplace reversed sort of global";

    @g = (2,3,1);
    $r1 = \$g[1]; @g = sort { $a<$b?1:$a>$b?-1:0 } @g; $r2 = \$g[0];
    ok "$r1-@g", "$r2-3 2 1", "inplace custom sort of global";

    sub mysort { $b cmp $a };
    @a = qw(b c a); $r1 = \$a[1]; @a = sort mysort @a; $r2 = \$a[0];
    ok "$r1-@a", "$r2-c b a", "inplace sort with function of lexical";

    use Tie::Array;
    my @t;
    tie @t, 'Tie::StdArray';

    @t = qw(b c a); @t = sort @t;
    ok "@t", "a b c", "inplace sort of tied array";

    @t = qw(b c a); @t = sort mysort @t;
    ok "@t", "c b a", "inplace sort of tied array with function";

    #  [perl #29790] don't optimise @a = ('a', sort @a) !

    @g = (3,2,1); @g = ('0', sort @g);
    ok "@g", "0 1 2 3", "un-inplace sort of global";
    @g = (3,2,1); @g = (sort(@g),'4');
    ok "@g", "1 2 3 4", "un-inplace sort of global 2";

    @a = qw(b a c); @a = ('x', sort @a);
    ok "@a", "x a b c", "un-inplace sort of lexical";
    @a = qw(b a c); @a = ((sort @a), 'x');
    ok "@a", "a b c x", "un-inplace sort of lexical 2";

    @g = (2,3,1); @g = ('0', sort { $b <=> $a } @g);
    ok "@g", "0 3 2 1", "un-inplace reversed sort of global";
    @g = (2,3,1); @g = ((sort { $b <=> $a } @g),'4');
    ok "@g", "3 2 1 4", "un-inplace reversed sort of global 2";

    @g = (2,3,1); @g = ('0', sort { $a<$b?1:$a>$b?-1:0 } @g);
    ok "@g", "0 3 2 1", "un-inplace custom sort of global";
    @g = (2,3,1); @g = ((sort { $a<$b?1:$a>$b?-1:0 } @g),'4');
    ok "@g", "3 2 1 4", "un-inplace custom sort of global 2";

    @a = qw(b c a); @a = ('x', sort mysort @a);
    ok "@a", "x c b a", "un-inplace sort with function of lexical";
    @a = qw(b c a); @a = ((sort mysort @a),'x');
    ok "@a", "c b a x", "un-inplace sort with function of lexical 2";

    # RT#54758. Git 62b40d2474e7487e6909e1872b6bccdf812c6818
    no warnings 'void';
    my @m; push @m, 0 for 1 .. 1024; $#m; @m = sort @m;
    main::pass("in-place sorting segfault");
}

# Test optimisations of reversed sorts. As we now guarantee stability by
# default, # optimisations which do not provide this are bogus.

{
    package Oscalar;
    use overload (qw("" stringify 0+ numify fallback 1));

    sub new {
	bless [$_[1], $_[2]], $_[0];
    }

    sub stringify { $_[0]->[0] }

    sub numify { $_[0]->[1] }
}

sub generate {
    my $count = 0;
    map {new Oscalar $_, $count++} qw(A A A B B B C C C);
}

my @input = &generate;
my @output = sort @input;
ok join(" ", map {0+$_} @output), "0 1 2 3 4 5 6 7 8", "Simple stable sort";

@input = &generate;
@input = sort @input;
ok join(" ", map {0+$_} @input), "0 1 2 3 4 5 6 7 8",
    "Simple stable in place sort";

# This won't be very interesting
@input = &generate;
@output = sort {$a <=> $b} @input;
ok "@output", "A A A B B B C C C", 'stable $a <=> $b sort';

@input = &generate;
@output = sort {$a cmp $b} @input;
ok join(" ", map {0+$_} @output), "0 1 2 3 4 5 6 7 8", 'stable $a cmp $b sort';

@input = &generate;
@input = sort {$a cmp $b} @input;
ok join(" ", map {0+$_} @input), "0 1 2 3 4 5 6 7 8",
    'stable $a cmp $b in place sort';

@input = &generate;
@output = sort {$b cmp $a} @input;
ok join(" ", map {0+$_} @output), "6 7 8 3 4 5 0 1 2", 'stable $b cmp $a sort';

@input = &generate;
@input = sort {$b cmp $a} @input;
ok join(" ", map {0+$_} @input), "6 7 8 3 4 5 0 1 2",
    'stable $b cmp $a in place sort';

@input = &generate;
@output = reverse sort @input;
ok join(" ", map {0+$_} @output), "8 7 6 5 4 3 2 1 0", "Reversed stable sort";

@input = &generate;
@input = reverse sort @input;
ok join(" ", map {0+$_} @input), "8 7 6 5 4 3 2 1 0",
    "Reversed stable in place sort";

@input = &generate;
my $output = reverse sort @input;
ok $output, "CCCBBBAAA", "Reversed stable sort in scalar context";


@input = &generate;
@output = reverse sort {$a cmp $b} @input;
ok join(" ", map {0+$_} @output), "8 7 6 5 4 3 2 1 0",
    'reversed stable $a cmp $b sort';

@input = &generate;
@input = reverse sort {$a cmp $b} @input;
ok join(" ", map {0+$_} @input), "8 7 6 5 4 3 2 1 0",
    'revesed stable $a cmp $b in place sort';

@input = &generate;
$output = reverse sort {$a cmp $b} @input;
ok $output, "CCCBBBAAA", 'Reversed stable $a cmp $b sort in scalar context';

@input = &generate;
@output = reverse sort {$b cmp $a} @input;
ok join(" ", map {0+$_} @output), "2 1 0 5 4 3 8 7 6",
    'reversed stable $b cmp $a sort';

@input = &generate;
@input = reverse sort {$b cmp $a} @input;
ok join(" ", map {0+$_} @input), "2 1 0 5 4 3 8 7 6",
    'revesed stable $b cmp $a in place sort';

@input = &generate;
$output = reverse sort {$b cmp $a} @input;
ok $output, "AAABBBCCC", 'Reversed stable $b cmp $a sort in scalar context';

sub stuff {
    # Something complex enough to defeat any constant folding optimiser
    $$ - $$;
}

@input = &generate;
@output = reverse sort {stuff || $a cmp $b} @input;
ok join(" ", map {0+$_} @output), "8 7 6 5 4 3 2 1 0",
    'reversed stable complex sort';

@input = &generate;
@input = reverse sort {stuff || $a cmp $b} @input;
ok join(" ", map {0+$_} @input), "8 7 6 5 4 3 2 1 0",
    'revesed stable complex in place sort';

@input = &generate;
$output = reverse sort {stuff || $a cmp $b } @input;
ok $output, "CCCBBBAAA", 'Reversed stable complex sort in scalar context';

sub sortr {
    reverse sort @_;
}

@output = sortr &generate;
ok join(" ", map {0+$_} @output), "8 7 6 5 4 3 2 1 0",
    'reversed stable sort return list context';
$output = sortr &generate;
ok $output, "CCCBBBAAA",
    'reversed stable sort return scalar context';

sub sortcmpr {
    reverse sort {$a cmp $b} @_;
}

@output = sortcmpr &generate;
ok join(" ", map {0+$_} @output), "8 7 6 5 4 3 2 1 0",
    'reversed stable $a cmp $b sort return list context';
$output = sortcmpr &generate;
ok $output, "CCCBBBAAA",
    'reversed stable $a cmp $b sort return scalar context';

sub sortcmprba {
    reverse sort {$b cmp $a} @_;
}

@output = sortcmprba &generate;
ok join(" ", map {0+$_} @output), "2 1 0 5 4 3 8 7 6",
    'reversed stable $b cmp $a sort return list context';
$output = sortcmprba &generate;
ok $output, "AAABBBCCC",
'reversed stable $b cmp $a sort return scalar context';

sub sortcmprq {
    reverse sort {stuff || $a cmp $b} @_;
}

@output = sortcmpr &generate;
ok join(" ", map {0+$_} @output), "8 7 6 5 4 3 2 1 0",
    'reversed stable complex sort return list context';
$output = sortcmpr &generate;
ok $output, "CCCBBBAAA",
    'reversed stable complex sort return scalar context';

# And now with numbers

sub generate1 {
    my $count = 'A';
    map {new Oscalar $count++, $_} 0, 0, 0, 1, 1, 1, 2, 2, 2;
}

# This won't be very interesting
@input = &generate1;
@output = sort {$a cmp $b} @input;
ok "@output", "A B C D E F G H I", 'stable $a cmp $b sort';

@input = &generate1;
@output = sort {$a <=> $b} @input;
ok "@output", "A B C D E F G H I", 'stable $a <=> $b sort';

@input = &generate1;
@input = sort {$a <=> $b} @input;
ok "@input", "A B C D E F G H I", 'stable $a <=> $b in place sort';

@input = &generate1;
@output = sort {$b <=> $a} @input;
ok "@output", "G H I D E F A B C", 'stable $b <=> $a sort';

@input = &generate1;
@input = sort {$b <=> $a} @input;
ok "@input", "G H I D E F A B C", 'stable $b <=> $a in place sort';

# test that optimized {$b cmp $a} and {$b <=> $a} remain stable
# (new in 5.9) without overloading
{ no warnings;
@b = sort { $b <=> $a } @input = qw/5first 6first 5second 6second/;
ok "@b" , "6first 6second 5first 5second", "optimized {$b <=> $a} without overloading" ;
@input = sort {$b <=> $a} @input;
ok "@input" , "6first 6second 5first 5second","inline optimized {$b <=> $a} without overloading" ;
};

# These two are actually doing string cmp on 0 1 and 2
@input = &generate1;
@output = reverse sort @input;
ok "@output", "I H G F E D C B A", "Reversed stable sort";

@input = &generate1;
@input = reverse sort @input;
ok "@input", "I H G F E D C B A", "Reversed stable in place sort";

@input = &generate1;
$output = reverse sort @input;
ok $output, "IHGFEDCBA", "Reversed stable sort in scalar context";

@input = &generate1;
@output = reverse sort {$a <=> $b} @input;
ok "@output", "I H G F E D C B A", 'reversed stable $a <=> $b sort';

@input = &generate1;
@input = reverse sort {$a <=> $b} @input;
ok "@input", "I H G F E D C B A", 'revesed stable $a <=> $b in place sort';

@input = &generate1;
$output = reverse sort {$a <=> $b} @input;
ok $output, "IHGFEDCBA", 'reversed stable $a <=> $b sort in scalar context';

@input = &generate1;
@output = reverse sort {$b <=> $a} @input;
ok "@output", "C B A F E D I H G", 'reversed stable $b <=> $a sort';

@input = &generate1;
@input = reverse sort {$b <=> $a} @input;
ok "@input", "C B A F E D I H G", 'revesed stable $b <=> $a in place sort';

@input = &generate1;
$output = reverse sort {$b <=> $a} @input;
ok $output, "CBAFEDIHG", 'reversed stable $b <=> $a sort in scalar context';

@input = &generate1;
@output = reverse sort {stuff || $a <=> $b} @input;
ok "@output", "I H G F E D C B A", 'reversed stable complex sort';

@input = &generate1;
@input = reverse sort {stuff || $a <=> $b} @input;
ok "@input", "I H G F E D C B A", 'revesed stable complex in place sort';

@input = &generate1;
$output = reverse sort {stuff || $a <=> $b} @input;
ok $output, "IHGFEDCBA", 'reversed stable complex sort in scalar context';

sub sortnumr {
    reverse sort {$a <=> $b} @_;
}

@output = sortnumr &generate1;
ok "@output", "I H G F E D C B A",
    'reversed stable $a <=> $b sort return list context';
$output = sortnumr &generate1;
ok $output, "IHGFEDCBA", 'reversed stable $a <=> $b sort return scalar context';

sub sortnumrba {
    reverse sort {$b <=> $a} @_;
}

@output = sortnumrba &generate1;
ok "@output", "C B A F E D I H G",
    'reversed stable $b <=> $a sort return list context';
$output = sortnumrba &generate1;
ok $output, "CBAFEDIHG", 'reversed stable $b <=> $a sort return scalar context';

sub sortnumrq {
    reverse sort {stuff || $a <=> $b} @_;
}

@output = sortnumrq &generate1;
ok "@output", "I H G F E D C B A",
    'reversed stable complex sort return list context';
$output = sortnumrq &generate1;
ok $output, "IHGFEDCBA", 'reversed stable complex sort return scalar context';

@output = reverse (sort(qw(C A B)), 0);
ok "@output", "0 C B A", 'reversed sort with trailing argument';

@output = reverse (0, sort(qw(C A B)));
ok "@output", "C B A 0", 'reversed sort with leading argument';

eval { @output = sort {goto sub {}} 1,2; };
$fail_msg = q(Can't goto subroutine outside a subroutine);
main::cmp_ok(substr($@,0,length($fail_msg)),'eq',$fail_msg,'goto subr outside subr');


sub goto_sub {goto sub{}}
eval { @output = sort goto_sub 1,2; };
$fail_msg = q(Can't goto subroutine from a sort sub);
main::cmp_ok(substr($@,0,length($fail_msg)),'eq',$fail_msg,'goto subr from a sort sub');


eval { @output = sort {goto label} 1,2; };
$fail_msg = q(Can't "goto" out of a pseudo block);
main::cmp_ok(substr($@,0,length($fail_msg)),'eq',$fail_msg,'goto out of a pseudo block 1');


sub goto_label {goto label}
label: eval { @output = sort goto_label 1,2; };
$fail_msg = q(Can't "goto" out of a pseudo block);
main::cmp_ok(substr($@,0,length($fail_msg)),'eq',$fail_msg,'goto out of a pseudo block 2');


sub self_immolate {undef &self_immolate; $a<=>$b}
eval { @output = sort self_immolate 1,2,3 };
$fail_msg = q(Can't undef active subroutine);
main::cmp_ok(substr($@,0,length($fail_msg)),'eq',$fail_msg,'undef active subr');


{
    my $failed = 0;

    sub rec {
	my $n = shift;
	if (!defined($n)) {  # No arg means we're being called by sort()
	    return 1;
	}
	if ($n<5) { rec($n+1); }
	else { () = sort rec 1,2; }

	$failed = 1 if !defined $n;
    }

    rec(1);
    main::ok(!$failed, "sort from active sub");
}

# $a and $b are set in the package the sort() is called from,
# *not* the package the sort sub is in. This is longstanding
# de facto behaviour that shouldn't be broken.
package main;
my $answer = "good";
() = sort OtherPack::foo 1,2,3,4;

{
    package OtherPack;
    no warnings 'once';
    sub foo {
	$answer = "something was unexpectedly defined or undefined" if
	defined($a) || defined($b) || !defined($main::a) || !defined($main::b);
	$main::a <=> $main::b;
    }
}

main::cmp_ok($answer,'eq','good','sort subr called from other package');


# Bug 36430 - sort called in package2 while a
# sort in package1 is active should set $package2::a/b.

$answer = "good";
my @list = sort { A::min(@$a) <=> A::min(@$b) }
  [3, 1, 5], [2, 4], [0];

main::cmp_ok($answer,'eq','good','bug 36430');

package A;
sub min {
  my @list = sort {
    $answer = '$a and/or $b are not defined ' if !defined($a) || !defined($b);
    $a <=> $b;
  } @_;
  $list[0];
}

# Bug 7567 - an array shouldn't be modifiable while it's being
# sorted in-place.
eval { @a=(1..8); @a = sort { @a = (0) } @a; };

$fail_msg = q(Modification of a read-only value attempted);
main::cmp_ok(substr($@,0,length($fail_msg)),'eq',$fail_msg,'bug 7567');


# Sorting shouldn't increase the refcount of a sub
sub foo {(1+$a) <=> (1+$b)}
my $refcnt = &Internals::SvREFCNT(\&foo);
@output = sort foo 3,7,9;
package Foo;
ok($refcnt, &Internals::SvREFCNT(\&foo), "sort sub refcnt");
$fail_msg = q(Modification of a read-only value attempted);
# Sorting a read-only array in-place shouldn't be allowed
my @readonly = (1..10);
Internals::SvREADONLY(@readonly, 1);
eval { @readonly = sort @readonly; };
main::cmp_ok(substr($@,0,length($fail_msg)),'eq',$fail_msg,'in-place sort of read-only array');


# Using return() should be okay even in a deeper context
@b = sort {while (1) {return ($a <=> $b)} } 1..10;
ok("@b", "1 2 3 4 5 6 7 8 9 10", "return within loop");

# Using return() should be okay even if there are other items
# on the stack at the time.
@b = sort {$_ = ($a<=>$b) + do{return $b<=> $a}} 1..10;
ok("@b", "10 9 8 7 6 5 4 3 2 1", "return with SVs on stack");

# As above, but with a sort sub rather than a sort block.
sub ret_with_stacked { $_ = ($a<=>$b) + do {return $b <=> $a} }
@b = sort ret_with_stacked 1..10;
ok("@b", "10 9 8 7 6 5 4 3 2 1", "return with SVs on stack");