[ruby/rdoc] Fix to parse rb_define_global_const

https://github.com/ruby/ruby/pull/12357

https://github.com/ruby/rdoc/commit/458ecbb7f7

lib/rdoc/parser/c.rb

@@ -405,6 +405,7 @@ class RDoc::Parser::C < RDoc::Parser
                  \s*(.*?)\s*\)\s*;
                  %xm) do |type, var_name, const_name, definition|
       var_name = "rb_cObject" if !var_name or var_name == "rb_mKernel"
+      type = "const" if type == "global_const"
       handle_constants type, var_name, const_name, definition
     end
 
@@ -760,6 +761,10 @@ class RDoc::Parser::C < RDoc::Parser
         rb_define_(?<type>\w+)\(\s*(?:\w+),\s*
                            "(?<name>\w+)"\s*,
                            .*?\)\s*;
+    | (?<doc>(?>^\s*/\*.*?\*/\s+))
+        rb_define_global_(?<type>const)\(\s*
+                           "(?<name>\w+)"\s*,
+                           .*?\)\s*;
     |  (?<doc>(?>^\s*/\*.*?\*/\s+))
         rb_file_(?<type>const)\(\s*
                            "(?<name>\w+)"\s*,

test/rdoc/test_rdoc_parser_c.rb

@@ -577,6 +577,38 @@ Multiline comment goes here because this comment spans multiple lines.
     assert constants.empty?, constants.inspect
   end
 
+  def test_do_constants_global
+    content = <<-'EOF'
+#include <ruby.h>
+
+void Init_foo(){
+
+   /* Toplevel const */
+   rb_define_global_const("ANSWER", INT2FIX(42));
+
+}
+    EOF
+
+    @parser = util_parser content
+
+    @parser.do_classes_and_modules
+    @parser.do_constants
+
+    klass = @parser.classes['rb_cObject']
+    assert klass
+
+    constants = klass.constants
+    assert !klass.constants.empty?
+
+    assert_equal @top_level, constants.first.file
+
+    constants = constants.map { |c| [c.name, c.value, c.comment.text] }
+    assert_equal ['ANSWER', 'INT2FIX(42)', "Toplevel const   "],
+                 constants.shift
+
+    assert constants.empty?, constants.inspect
+  end
+
   def test_do_constants_curses
     content = <<-EOF
 void Init_curses(){
@@ -1037,6 +1069,21 @@ rb_define_const(cFoo, "CONST", value);
     assert_equal "/*\n * A comment\n */\n", comment.text
   end
 
+  def test_find_const_comment_rb_define_global
+    content = <<-EOF
+/*
+ * A comment
+ */
+rb_define_global_const("CONST", value);
+    EOF
+
+    parser = util_parser content
+
+    comment = parser.find_const_comment 'const', 'CONST'
+
+    assert_equal "/*\n * A comment\n */\n", comment.text
+  end
+
   def test_find_const_comment_document_const
     content = <<-EOF
 /*