merge revision(s) 77596fb7a9: [Backport #16138]

Do not turn on keyword_init for Struct subclass if keyword hash is
	 empty

	This was accidentally turned on because there was no checking for
	Qundef.

	Also, since only a single keyword is currently supported, simplify
	the rb_get_kwargs call.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@67866 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

struct.c

@@ -517,7 +517,7 @@ rb_struct_define_under(VALUE outer, const char *name, ...)
 static VALUE
 rb_struct_s_def(int argc, VALUE *argv, VALUE klass)
 {
-    VALUE name, rest, keyword_init;
+    VALUE name, rest, keyword_init = Qfalse;
     long i;
     VALUE st;
     st_table *tbl;
@@ -533,18 +533,16 @@ rb_struct_s_def(int argc, VALUE *argv, VALUE klass)
     }
 
     if (RB_TYPE_P(argv[argc-1], T_HASH)) {
-	VALUE kwargs[1];
 	static ID keyword_ids[1];
 
 	if (!keyword_ids[0]) {
 	    keyword_ids[0] = rb_intern("keyword_init");
 	}
-	rb_get_kwargs(argv[argc-1], keyword_ids, 0, 1, kwargs);
+        rb_get_kwargs(argv[argc-1], keyword_ids, 0, 1, &keyword_init);
+        if (keyword_init == Qundef) {
+            keyword_init = Qfalse;
+        }
 	--argc;
-	keyword_init = kwargs[0];
-    }
-    else {
-	keyword_init = Qfalse;
     }
 
     rest = rb_ident_hash_new();

test/ruby/test_struct.rb

@@ -92,6 +92,10 @@ module TestStruct
     assert_equal([:utime, :stime, :cutime, :cstime], Process.times.members)
   end
 
+  def test_struct_new_with_empty_hash
+    assert_equal({:a=>1}, Struct.new(:a, {}).new({:a=>1}).a)
+  end
+
   def test_struct_new_with_keyword_init
     @Struct.new("KeywordInitTrue", :a, :b, keyword_init: true)
     @Struct.new("KeywordInitFalse", :a, :b, keyword_init: false)

version.h

@@ -1,6 +1,6 @@
 #define RUBY_VERSION "2.5.8"
 #define RUBY_RELEASE_DATE "2020-03-31"
-#define RUBY_PATCHLEVEL 215
+#define RUBY_PATCHLEVEL 216
 
 #define RUBY_RELEASE_YEAR 2020
 #define RUBY_RELEASE_MONTH 3