* string.c (rb_str_set_len): should fail to modify shared string.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@28865 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,7 @@
+Thu Aug  5 16:42:41 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* string.c (rb_str_set_len): should fail to modify shared string.
+
 Thu Aug  5 14:12:44 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* ruby.c (ruby_init_loadpath_safe): ensure sopath to be modifiable

ext/-test-/string/extconf.rb

@@ -0,0 +1,6 @@
+$srcs = Dir[File.join($srcdir, "*.{#{SRC_EXT.join(%q{,})}}")]
+inits = $srcs.map {|s| File.basename(s, ".*")}
+inits.delete("init")
+inits.map! {|s|"X(#{s})"}
+$defs << "-DTEST_INIT_FUNCS(X)=\"#{inits.join(' ')}\""
+create_makefile("-test-/string/string")

ext/-test-/string/init.c

@@ -0,0 +1,19 @@
+#include "ruby.h"
+
+#define init(n) {void Init_##n(VALUE klass); Init_##n(klass);}
+
+VALUE
+bug_str_modify(VALUE str)
+{
+    rb_str_modify(str);
+    return str;
+}
+
+void
+Init_string(void)
+{
+    VALUE mBug = rb_define_module("Bug");
+    VALUE klass = rb_define_class_under(mBug, "String", rb_cString);
+    rb_define_method(klass, "modify!", bug_str_modify, 0);
+    TEST_INIT_FUNCS(init);
+}

ext/-test-/string/set_len.c

@@ -0,0 +1,14 @@
+#include "ruby.h"
+
+static VALUE
+bug_str_set_len(VALUE str, VALUE len)
+{
+    rb_str_set_len(str, NUM2LONG(len));
+    return str;
+}
+
+void
+Init_set_len(VALUE klass)
+{
+    rb_define_method(klass, "set_len", bug_str_set_len, 1);
+}

string.c

@@ -1694,6 +1694,9 @@ void
 rb_str_set_len(VALUE str, long len)
 {
     str_modifiable(str);
+    if (STR_SHARED_P(str)) {
+	rb_raise(rb_eRuntimeError, "can't set length of shared string");
+    }
     STR_SET_LEN(str, len);
     RSTRING_PTR(str)[len] = '\0';
 }

test/-ext-/string/test_set_len.rb

@@ -0,0 +1,25 @@
+require 'test/unit'
+require "-test-/string/string"
+
+class Test_StrSetLen < Test::Unit::TestCase
+  def setup
+    @s0 = [*"a".."z"].join("").freeze
+    @s1 = Bug::String.new(@s0)
+  end
+
+  def teardown
+    orig = [*"a".."z"].join("")
+    assert_equal(orig, @s0)
+  end
+
+  def test_non_shared
+    @s1.modify!
+    assert_equal("abc", @s1.set_len(3))
+  end
+
+  def test_shared
+    assert_raise(RuntimeError) {
+      assert_equal("abc", @s1.set_len(3))
+    }
+  end
+end