Some global variables can be accessed from ractors

Some global variables should be used from non-main Ractors.
[Bug #17268]

```ruby
     # ractor-local (derived from created ractor): debug
     '$DEBUG' => $DEBUG,
     '$-d' => $-d,

     # ractor-local (derived from created ractor): verbose
     '$VERBOSE' => $VERBOSE,
     '$-w' => $-w,
     '$-W' => $-W,
     '$-v' => $-v,

     # process-local (readonly): other commandline parameters
     '$-p' => $-p,
     '$-l' => $-l,
     '$-a' => $-a,

     # process-local (readonly): getpid
     '$$'  => $$,

     # thread local: process result
     '$?'  => $?,

     # scope local: match
     '$~'  => $~.inspect,
     '$&'  => $&,
     '$`'  => $`,
     '$\''  => $',
     '$+'  => $+,
     '$1'  => $1,

     # scope local: last line
     '$_' => $_,

     # scope local: last backtrace
     '$@' => $@,
     '$!' => $!,

     # ractor local: stdin, out, err
     '$stdin'  => $stdin.inspect,
     '$stdout' => $stdout.inspect,
     '$stderr' => $stderr.inspect,
```

1 files changed, 41 insertions, 9 deletions

diff --git a/ruby.c b/ruby.c
index 9ca980dfbd..4feae7757a 100644
--- a/ruby.c
+++ b/ruby.c
@@ -63,6 +63,7 @@
 #include "ruby/thread.h"
 #include "ruby/util.h"
 #include "ruby/version.h"
+#include "ruby/internal/error.h"
 
 #ifndef MAXPATHLEN
 # define MAXPATHLEN 1024
@@ -2021,6 +2022,10 @@ process_options(int argc, char **argv, ruby_cmdline_options_t *opt)
     rb_define_readonly_boolean("$-l", opt->do_line);
     rb_define_readonly_boolean("$-a", opt->do_split);
 
+    rb_gvar_ractor_local("$-p");
+    rb_gvar_ractor_local("$-l");
+    rb_gvar_ractor_local("$-a");
+
     if ((rb_e_script = opt->e_script) != 0) {
         rb_gc_register_mark_object(opt->e_script);
     }
@@ -2430,16 +2435,24 @@ forbid_setid(const char *s, const ruby_cmdline_options_t *opt)
         rb_raise(rb_eSecurityError, "no %s allowed while running setgid", s);
 }
 
+static VALUE
+verbose_getter(ID id, VALUE *ptr)
+{
+    return *rb_ruby_verbose_ptr();
+}
+
 static void
 verbose_setter(VALUE val, ID id, VALUE *variable)
 {
-    *variable = RTEST(val) ? Qtrue : val;
+    *rb_ruby_verbose_ptr() = RTEST(val) ? Qtrue : val;
 }
 
 static VALUE
-opt_W_getter(ID id, VALUE *variable)
+opt_W_getter(ID id, VALUE *dmy)
 {
-    switch (*variable) {
+    VALUE v = *rb_ruby_verbose_ptr();
+
+    switch (v) {
       case Qnil:
 	return INT2FIX(0);
       case Qfalse:
@@ -2451,16 +2464,35 @@ opt_W_getter(ID id, VALUE *variable)
     }
 }
 
+static VALUE
+debug_getter(ID id, VALUE *dmy)
+{
+    return *rb_ruby_debug_ptr();
+}
+
+static void
+debug_setter(VALUE val, ID id, VALUE *dmy)
+{
+    *rb_ruby_debug_ptr() = val;
+}
+
 /*! Defines built-in variables */
 void
 ruby_prog_init(void)
 {
-    rb_define_hooked_variable("$VERBOSE", &ruby_verbose, 0, verbose_setter);
-    rb_define_hooked_variable("$-v", &ruby_verbose, 0, verbose_setter);
-    rb_define_hooked_variable("$-w", &ruby_verbose, 0, verbose_setter);
-    rb_define_hooked_variable("$-W", &ruby_verbose, opt_W_getter, rb_gvar_readonly_setter);
-    rb_define_variable("$DEBUG", &ruby_debug);
-    rb_define_variable("$-d", &ruby_debug);
+    rb_define_virtual_variable("$VERBOSE", verbose_getter, verbose_setter);
+    rb_define_virtual_variable("$-v",      verbose_getter, verbose_setter);
+    rb_define_virtual_variable("$-w",      verbose_getter, verbose_setter);
+    rb_define_virtual_variable("$-W",      opt_W_getter,   rb_gvar_readonly_setter);
+    rb_define_virtual_variable("$DEBUG",   debug_getter,   debug_setter);
+    rb_define_virtual_variable("$-d",      debug_getter,   debug_setter);
+
+    rb_gvar_ractor_local("$VERBOSE");
+    rb_gvar_ractor_local("$-v");
+    rb_gvar_ractor_local("$-w");
+    rb_gvar_ractor_local("$-W");
+    rb_gvar_ractor_local("$DEBUG");
+    rb_gvar_ractor_local("$-d");
 
     rb_define_hooked_variable("$0", &rb_progname, 0, set_arg0);
     rb_define_hooked_variable("$PROGRAM_NAME", &rb_progname, 0, set_arg0);