Separate 'goto' tests according to flavor tested

Create t/op/goto-sub.t to hold tests for 'goto &NAME', as they will
presumably be unaffected by deprecation/fatalization of certain other
usages of 'goto'.

In the course of working on this a few other small cleanups were made,
e.g., disambiguation of various uses of $ok; small whitespace cleanup;
more use of {} blocks to distinguish among clusters of tests.

Author: jkeenan

MANIFEST

@@ -6348,6 +6348,7 @@ t/op/getppid.t				See if getppid works
 t/op/glob.t				See if <*> works
 t/op/gmagic.t				See if GMAGIC works
 t/op/goto.t				See if goto works
+t/op/goto-sub.t				See if goto &NAME works
 t/op/goto_xs.t				See if "goto &sub" works on XSUBs
 t/op/grent.t				See if getgr*() functions work
 t/op/grep.t				See if grep() and map() work

t/op/goto-sub.t

@@ -0,0 +1,364 @@
+#!./perl
+
+BEGIN {
+    chdir 't' if -d 't';
+    require "./test.pl";
+    set_up_inc( qw(. ../lib) );
+	require './charset_tools.pl';
+}
+
+use warnings;
+use strict;
+use Config;
+plan tests => 40;
+
+# Excerpts from 'perldoc -f goto' as of perl-5.40.1 (Aug 2025)
+#
+# The "goto &NAME" form is quite different from the other forms of
+# "goto". In fact, it isn't a goto in the normal sense at all, and
+# doesn't have the stigma associated with other gotos. Instead, it
+# exits the current subroutine (losing any changes set by "local")
+# and immediately calls in its place the named subroutine using
+# the current value of @_. This is used by "AUTOLOAD" subroutines
+# that wish to load another subroutine and then pretend that the
+# other subroutine had been called in the first place (except that
+# any modifications to @_ in the current subroutine are propagated
+# to the other subroutine.) After the "goto", not even "caller"
+# will be able to tell that this routine was called first.
+#
+# NAME needn't be the name of a subroutine; it can be a scalar
+# variable containing a code reference or a block that evaluates
+# to a code reference.
+
+# but earlier, we see:
+#
+# The "goto EXPR" form expects to evaluate "EXPR" to a code
+# reference or a label name. If it evaluates to a code reference,
+# it will be handled like "goto &NAME", below. This is especially
+# useful for implementing tail recursion via "goto __SUB__".
+#
+# The purpose this test file is to consolidate all tests formerly found in
+# t/op/goto.t that exercise the "goto &NAME" functionality.  These should be
+# outside the scope of the current (5.42) deprecation of aspects of "goto
+# LABEL" (GH #23618) now scheduled for 5.44.  If we have done that
+# successfully, then during the 5.43 dev cycle we shouldn't see any instances
+# of this warning (or of its fatalization replacement).
+
+my $deprecated = 0;
+
+local $SIG{__WARN__} = sub {
+    if ($_[0] =~ m/jump into a construct.*?, and will become fatal in Perl 5\.42/) {
+        $deprecated++;
+    }
+    else { warn $_[0] }
+};
+
+our $foo;
+
+###################
+
+# bug #9990 - don't prematurely free the CV we're &going to.
+
+sub f1 {
+    my $x;
+    goto sub { $x=0; ok(1,"don't prematurely free CV\n") }
+}
+f1();
+
+# bug #99850, which is similar - freeing the subroutine we are about to
+# go(in)to during a FREETMPS call should not crash perl.
+
+package _99850 {
+    sub reftype{}
+    DESTROY { undef &reftype }
+    eval { sub { my $guard = bless []; goto &reftype }->() };
+}
+like $@, qr/^Goto undefined subroutine &_99850::reftype at /,
+   'goto &foo undefining &foo on sub cleanup';
+
+# When croaking after discovering that the new CV you're about to goto is
+# undef, make sure that the old CV isn't doubly freed.
+
+package Do_undef {
+    my $count;
+
+    # creating a new closure here encourages any prematurely freed
+    # CV to be reallocated
+    sub DESTROY { undef &undef_sub; my $x = sub { $count } }
+
+    sub f {
+        $count++;
+        my $guard = bless []; # trigger DESTROY during goto
+        *undef_sub = sub {};
+        goto &undef_sub
+    }
+
+    for (1..10) {
+        eval { f() };
+    }
+    ::is($count, 10, "goto undef_sub safe");
+}
+
+# make sure that nothing nasty happens if the old CV is freed while
+# goto'ing
+
+package Free_cv {
+    my $results;
+    sub f {
+        no warnings 'redefine';
+        *f = sub {};
+        goto &g;
+    }
+    sub g { $results = "(@_)" }
+
+    f(1,2,3);
+    ::is($results, "(1 2 3)", "Free_cv");
+}
+
+# [perl #29708] - goto &foo could leave foo() at depth two with
+# @_ == PL_sv_undef, causing a coredump
+
+my $r = runperl(
+    prog =>
+	'sub f { return if $d; $d=1; my $a=sub {goto &f}; &$a; f() } f(); print qq(ok\n)',
+    stderr => 1
+    );
+is($r, "ok\n", 'avoid pad without an @_');
+
+# see if a modified @_ propagates
+{
+  my $i;
+  package Foo;
+  sub DESTROY	{ my $s = shift; ::is($s->[0], $i, "destroy $i"); }
+  sub show	{ ::is(+@_, 5, "show $i",); }
+  sub start	{ push @_, 1, "foo", {}; goto &show; }
+  for (1..3)	{ $i = $_; start(bless([$_]), 'bar'); }
+}
+
+sub auto {
+    goto &loadit;
+}
+my $ok;
+
+sub AUTOLOAD { $ok = 1 if "@_" eq "foo" }
+
+$ok = 0;
+auto("foo");
+ok($ok, 'autoload');
+
+# Test autoloading mechanism.
+
+sub two {
+    my ($pack, $file, $line) = caller;	# Should indicate original call stats.
+    is("@_ $pack $file $line", "1 2 3 main $::FILE $::LINE",
+	'autoloading mechanism.');
+}
+
+sub one {
+    eval <<'END';
+    no warnings 'redefine';
+    sub one { pass('sub one'); goto &two; fail('sub one tail'); }
+END
+    goto &one;
+}
+
+$::FILE = __FILE__;
+$::LINE = __LINE__ + 1;
+&one(1,2,3);
+
+# deep recursion with gotos eventually caused a stack reallocation
+# which messed up buggy internals that didn't expect the stack to move
+
+sub recurse1 {
+    unshift @_, "x";
+    no warnings 'recursion';
+    goto &recurse2;
+}
+sub recurse2 {
+    my $x = shift;
+    $_[0] ? +1 + recurse1($_[0] - 1) : 0
+}
+
+{
+my $w = 0;
+    local $SIG{__WARN__} = sub { ++$w };
+    is(recurse1(500), 500, 'recursive goto &foo');
+    is $w, 0, 'no recursion warnings for "no warnings; goto &sub"';
+    delete $SIG{__WARN__};
+}
+
+# [perl #32039] Chained goto &sub drops data too early.
+
+sub a32039 { @_=("foo"); goto &b32039; }
+sub b32039 { goto &c32039; }
+sub c32039 { is($_[0], 'foo', 'chained &goto') }
+a32039();
+
+###################
+
+# goto &foo not allowed in evals
+
+sub null { 1 };
+eval 'goto &null';
+like($@, qr/Can't goto subroutine from an eval-string/, 'eval string');
+eval { goto &null };
+like($@, qr/Can't goto subroutine from an eval-block/, 'eval block');
+
+# goto &foo leaves @_ alone when called from a sub
+sub returnarg { $_[0] };
+is sub {
+    local *_ = ["ick and queasy"];
+    goto &returnarg;
+}->("quick and easy"), "ick and queasy",
+  'goto &foo with *_{ARRAY} replaced';
+my @__ = byte_utf8a_to_utf8n("\xc4\x80");
+sub { local *_ = \@__; goto &utf8::decode }->("no thinking aloud");
+is "@__", chr 256, 'goto &xsub with replaced *_{ARRAY}';
+
+# And goto &foo should leave reified @_ alone
+sub { *__ = \@_;  goto &null } -> ("rough and tubbery");
+is ${*__}[0], 'rough and tubbery', 'goto &foo leaves reified @_ alone';
+
+# goto &xsub when @_ has nonexistent elements
+{
+    no warnings "uninitialized";
+    local @_ = ();
+    $#_++;
+    & {sub { goto &utf8::encode }};
+    is @_, 1, 'num of elems in @_ after goto &xsub with nonexistent $_[0]';
+    is $_[0], "", 'content of nonexistent $_[0] is modified by goto &xsub';
+}
+
+# goto &xsub when @_ itself does not exist
+undef *_;
+eval { & { sub { goto &utf8::encode } } };
+# The main thing we are testing is that it did not crash.  But make sure 
+# *_{ARRAY} was untouched, too.
+is *_{ARRAY}, undef, 'goto &xsub when @_ does not exist';
+
+# goto &perlsub when @_ itself does not exist [perl #119949]
+# This was only crashing when the replaced sub call had an argument list.
+# (I.e., &{ sub { goto ... } } did not crash.)
+sub {
+    undef *_;
+    goto sub {
+	is *_{ARRAY}, undef, 'goto &perlsub when @_ does not exist';
+    }
+}->();
+sub {
+    local *_;
+    goto sub {
+	is *_{ARRAY}, undef, 'goto &sub when @_ does not exist (local *_)';
+    }
+}->();
+
+# [perl #36521] goto &foo in warn handler could defeat recursion avoider
+
+{
+    my $r = runperl(
+		stderr => 1,
+		prog => 'my $d; my $w = sub { return if $d++; warn q(bar)}; local $SIG{__WARN__} = sub { goto &$w; }; warn q(foo);'
+    );
+    like($r, qr/bar/, "goto &foo in warn");
+}
+
+{
+    sub TIESCALAR { bless [pop] }
+    sub FETCH     { $_[0][0] }
+    tie my $t, "", sub { "cluck up porridge" };
+    is eval { sub { goto $t }->() }//$@, 'cluck up porridge',
+      'tied arg returning sub ref';
+}
+
+# v5.31.3-198-gd2cd363728 broke this. goto &XS_sub  wasn't restoring
+# cx->blk_sub.old_cxsubix. Would panic in pp_return
+
+{
+    # isa is an XS sub
+    sub g198 {  goto &UNIVERSAL::isa }
+
+    sub f198 {
+        g198([], 1 );
+        {
+            return 1;
+        }
+    }
+    eval { f198(); };
+    is $@, "", "v5.31.3-198-gd2cd363728";
+}
+
+# GH #19188
+#
+# 'goto &xs_sub' should provide the correct caller context to an XS sub
+
+SKIP:
+{
+    skip "No XS::APItest in miniperl", 6 if is_miniperl();
+    skip "No XS::APItest in static perl", 6 if not $Config{usedl};
+
+    require XS::APItest;
+
+    sub f_19188 { goto &XS::APItest::gimme }
+    sub g_19188{ f_19188(); }
+    my ($s, @a);
+
+    f_19188();
+    is ($XS::APItest::GIMME_V, 1, 'xs_goto void (#19188)');
+
+    $s = f_19188();
+    is ($XS::APItest::GIMME_V, 2, 'xs_goto scalar (#19188)');
+
+    @a = f_19188();
+    is ($XS::APItest::GIMME_V, 3, 'xs_goto list (#19188)');
+
+    g_19188();
+    is ($XS::APItest::GIMME_V, 1, 'xs_goto indirect void (#19188)');
+
+    $s = g_19188();
+    is ($XS::APItest::GIMME_V, 2, 'xs_goto indirect scalar (#19188)');
+
+    @a = g_19188();
+    is ($XS::APItest::GIMME_V, 3, 'xs_goto indirect list (#19188)');
+}
+
+# GH #19936 segfault on goto &xs_sub when calling sub is replaced
+SKIP:
+{
+    skip "No XS::APItest in miniperl", 2 if is_miniperl();
+    skip "No XS::APItest in static perl", 2 if not $Config{usedl};
+
+    # utf8::is_utf8() is just an example of an XS sub
+    sub foo_19936 { *foo_19936 = {}; goto &utf8::is_utf8 }
+    ok(foo_19936("\x{100}"), "GH #19936 utf8 XS call");
+
+    # the gimme XS function accesses PL_op, which was null before the fix
+    sub bar_19936 { *bar_19936 = {}; goto &XS::APItest::gimme }
+    my @a = bar_19936();
+    is($XS::APItest::GIMME_V, 3, "GH #19936 gimme XS call");
+}
+
+# goto &sub could leave AvARRAY() slots of @_ uninitialised.
+
+{
+    my $i = 0;
+    my $f = sub {
+        goto &{ sub {} } unless $i++;
+        $_[1] = 1; # create a hole
+        # accessing $_[0] is more for valgrind/ASAN to chew on rather than
+        # we're too concerned about its value. Or it might give "bizarre
+        # copy" errors.
+        is($_[0], undef, "goto and AvARRAY");
+    };
+
+    # first call does goto, which gives &$f a fresh AV in pad[0],
+    # which formerly allocated an AvARRAY for it, but didn't zero it
+    $f->();
+    # second call creates hole in @_ which used to to be a wild SV pointer
+    $f->();
+}
+
+
+# Final test: ensure that we saw no deprecation warnings
+# ... but rework this to count fatalizations once work is more developed
+
+is($deprecated, 0, "No 'jump into a construct' warnings seen");