Add a specs for printing VALUEs as pointers using rb_sprintf.

Author: aardvark179

optional/capi/ext/string_spec.c

@@ -479,6 +479,15 @@ static VALUE string_spec_rb_sprintf6(VALUE self, VALUE width, VALUE precision, V
   return rb_sprintf("Result: %*.*" PRIsVALUE ".", FIX2INT(width), FIX2INT(precision), str);
 }
 
+static VALUE string_spec_rb_sprintf7(VALUE self, VALUE str, VALUE obj) {
+  VALUE results = rb_ary_new();
+  rb_ary_push(results, rb_sprintf(RSTRING_PTR(str), obj));
+  char cstr[256];
+  int len = snprintf(cstr, 256, RSTRING_PTR(str), obj);
+  rb_ary_push(results, rb_str_new(cstr, len));
+  return results;
+}
+
 PRINTF_ARGS(static VALUE string_spec_rb_vsprintf_worker(char* fmt, ...), 1, 2);
 static VALUE string_spec_rb_vsprintf_worker(char* fmt, ...) {
   va_list varargs;
@@ -638,6 +647,7 @@ void Init_string_spec(void) {
   rb_define_method(cls, "rb_sprintf4", string_spec_rb_sprintf4, 1);
   rb_define_method(cls, "rb_sprintf5", string_spec_rb_sprintf5, 3);
   rb_define_method(cls, "rb_sprintf6", string_spec_rb_sprintf6, 3);
+  rb_define_method(cls, "rb_sprintf7", string_spec_rb_sprintf7, 2);
   rb_define_method(cls, "rb_vsprintf", string_spec_rb_vsprintf, 4);
   rb_define_method(cls, "rb_str_equal", string_spec_rb_str_equal, 2);
   rb_define_method(cls, "rb_usascii_str_new", string_spec_rb_usascii_str_new, 2);

optional/capi/string_spec.rb

@@ -1085,6 +1085,16 @@ def inspect
       s = 'Result:    Hello.'
       @s.rb_sprintf6(8, 5, "Hello").should == s
     end
+
+    it "can format a nil VALUE as a pointer and gives the same output as sprintf in C" do
+      res = @s.rb_sprintf7("%p", nil);
+      res[0].should == res[1]
+    end
+
+    it "can format a string VALUE as a pointer and gives the same output as sprintf in C" do
+      res = @s.rb_sprintf7("%p", "Hello")
+      res[0].should == res[1]
+    end
   end
 
   describe "rb_vsprintf" do