Make String#-@ not freeze receiver if called on unfrozen subclass instance

jeremyevans · jeremyevans · commit 7582287eb27e · 2019-07-02T08:26:50.000-07:00
rb_fstring behavior in this case is to freeze the receiver.  I'm
not sure if that should be changed, so this takes the conservative
approach of duping the receiver in String#-@ before passing
to rb_fstring.

Fixes [Bug #15926]
diff --git a/string.c b/string.c
@@ -2658,6 +2658,9 @@ str_uplus(VALUE str)
 static VALUE
 str_uminus(VALUE str)
 {
+    if (!BARE_STRING_P(str) && !rb_obj_frozen_p(str)) {
+        str = rb_str_dup(str);
+    }
     return rb_fstring(str);
 }
 
diff --git a/test/ruby/test_string.rb b/test/ruby/test_string.rb
@@ -3175,6 +3175,22 @@ def test_uplus_minus
     assert_same(str, -bar, "uminus deduplicates [Feature #13077]")
   end
 
+  def test_uminus_no_freeze_not_bare
+    str = @cls.new("foo")
+    -str
+    assert_equal(false, str.frozen?)
+
+    str = @cls.new("foo")
+    str.instance_variable_set(:@iv, 1)
+    -str
+    assert_equal(false, str.frozen?)
+
+    str = @cls.new("foo")
+    str.taint
+    -str
+    assert_equal(false, str.frozen?)
+  end
+
   def test_ord
     assert_equal(97, "a".ord)
     assert_equal(97, "abc".ord)

Original file line number	Diff line number	Diff line change
`@@ -2658,6 +2658,9 @@ str_uplus(VALUE str)`
`2658`	`2658`	`static VALUE`
`2659`	`2659`	`str_uminus(VALUE str)`
`2660`	`2660`	`{`
	`2661`	`+ if (!BARE_STRING_P(str) && !rb_obj_frozen_p(str)) {`
	`2662`	`+ str = rb_str_dup(str);`
	`2663`	`+ }`
`2661`	`2664`	`return rb_fstring(str);`
`2662`	`2665`	`}`
`2663`	`2666`