Added rb_sym2str()

This just converts a Symbol/ID (we treat both as the same) to a String.

spec/ruby/optional/capi/ext/rubyspec.h

@@ -606,6 +606,7 @@
 #define HAVE_RB_IS_CLASS_ID                1
 #define HAVE_RB_IS_CONST_ID                1
 #define HAVE_RB_IS_INSTANCE_ID             1
+#define HAVE_RB_SYM2STR                    1
 
 /* Thread */
 #define HAVE_RB_THREAD_ALONE               1

spec/ruby/optional/capi/ext/symbol_spec.c

@@ -81,6 +81,12 @@ VALUE symbol_spec_rb_is_instance_id(VALUE self, VALUE sym) {
 }
 #endif
 
+#ifdef HAVE_RB_SYM2STR
+VALUE symbol_spec_rb_sym2str(VALUE self, VALUE sym) {
+  return rb_sym2str(sym);
+}
+#endif
+
 void Init_symbol_spec() {
   VALUE cls;
   cls = rb_define_class("CApiSymbolSpecs", rb_cObject);
@@ -121,6 +127,10 @@ void Init_symbol_spec() {
 #ifdef HAVE_RB_IS_INSTANCE_ID
   rb_define_method(cls, "rb_is_instance_id", symbol_spec_rb_is_instance_id, 1);
 #endif
+
+#ifdef HAVE_RB_SYM2STR
+  rb_define_method(cls, "rb_sym2str", symbol_spec_rb_sym2str, 1);
+#endif
 }
 
 #ifdef __cplusplus

spec/ruby/optional/capi/symbol_spec.rb

@@ -104,4 +104,10 @@
       @s.rb_is_class_id(:foo).should == false
     end
   end
+
+  describe "rb_sym2str" do
+    it "converts a Symbol to a String" do
+      @s.rb_sym2str(:bacon).should == "bacon"
+    end
+  end
 end

vm/capi/symbol.cpp

@@ -40,4 +40,8 @@ extern "C" {
     Object* p = reinterpret_cast<Symbol*>(sym)->is_cvar_p(env->state());
     return CBOOL(p) ? Qtrue : Qfalse;
   }
+
+  VALUE rb_sym2str(VALUE sym) {
+    return rb_id2str(SYM2ID(sym));
+  }
 }

vm/include/capi/ruby/ruby.h

@@ -1585,6 +1585,8 @@ struct RTypedData {
   ID      rb_intern_str(VALUE string);
 #define HAVE_RB_INTERN_STR 1
 
+  VALUE rb_sym2str(VALUE sym);
+
   /** Coerce x and y and perform 'x func y' */
   VALUE rb_num_coerce_bin(VALUE x, VALUE y, ID func);