parse.y: make shared string modifiable

* parse.y (dedent_string): ensure that the string is modifiable,
  not to set the length of shared string.
  [ruby-core:80987] [Bug #13540]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58561 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 5 insertions, 1 deletions

diff --git a/parse.y b/parse.y
index 028b89c070..ee48ad4f79 100644
--- a/parse.y
+++ b/parse.y
@@ -6392,6 +6392,11 @@ dedent_string(VALUE string, int width)
 	    break;
 	}
     }
+    if (!i) return 0;
+    rb_str_modify(string);
+    str = RSTRING_PTR(string);
+    if (RSTRING_LEN(string) != len)
+	rb_fatal("literal string changed: %+"PRIsVALUE, string);
     MEMMOVE(str, str + i, char, len - i);
     rb_str_set_len(string, len - i);
     return i;
@@ -6448,7 +6453,6 @@ parser_dedent_string(VALUE self, VALUE input, VALUE width)
 
     StringValue(input);
     wid = NUM2UINT(width);
-    rb_str_modify(input);
     col = dedent_string(input, wid);
     return INT2NUM(col);
 }