Switch conflicting chdir warning to RuntimeError

The documentation already stated this was an error in one case
(when it was previously a warning).  Describe the other case,
where chdir without block is called inside block passed to chdir.

Fixes [Bug #15661]

2 files changed, 31 insertions, 4 deletions

diff --git a/dir.c b/dir.c
index e5b6705b32..49e6818d25 100644
--- a/dir.c
+++ b/dir.c
@@ -1024,7 +1024,8 @@ chdir_restore(VALUE v)
  *  block. <code>chdir</code> blocks can be nested, but in a
  *  multi-threaded program an error will be raised if a thread attempts
  *  to open a <code>chdir</code> block while another thread has one
- *  open.
+ *  open or a call to <code>chdir</code> without a block occurs inside
+ *  a block passed to <code>chdir</code> (even in the same thread).
  *
  *     Dir.chdir("/var/spool/mail")
  *     puts Dir.pwd
@@ -1064,7 +1065,7 @@ dir_s_chdir(int argc, VALUE *argv, VALUE obj)
 
     if (chdir_blocking > 0) {
 	if (!rb_block_given_p() || rb_thread_current() != chdir_thread)
-	    rb_warn("conflicting chdir during another chdir block");
+            rb_raise(rb_eRuntimeError, "conflicting chdir during another chdir block");
     }
 
     if (rb_block_given_p()) {
diff --git a/test/ruby/test_dir.rb b/test/ruby/test_dir.rb
index 13b9c1ddf2..cf18af134c 100644
--- a/test/ruby/test_dir.rb
+++ b/test/ruby/test_dir.rb
@@ -99,8 +99,12 @@ class TestDir < Test::Unit::TestCase
     ENV["HOME"] = @pwd
     Dir.chdir do
       assert_equal(@pwd, Dir.pwd)
-      Dir.chdir(@root)
-      assert_equal(@root, Dir.pwd)
+      assert_raise(RuntimeError) { Dir.chdir(@root) }
+      assert_equal(@pwd, Dir.pwd)
+      Dir.chdir(@root) do
+        assert_equal(@root, Dir.pwd)
+      end
+      assert_equal(@pwd, Dir.pwd)
     end
 
   ensure
@@ -121,6 +125,28 @@ class TestDir < Test::Unit::TestCase
     end
   end
 
+  def test_chdir_conflict
+    @pwd = Dir.pwd
+    q = Queue.new
+    t = Thread.new do
+      q.pop
+      Dir.chdir(@pwd) rescue $!
+    end
+    Dir.chdir(@pwd) do
+      q.push nil
+      assert_instance_of(RuntimeError, t.value)
+    end
+
+    t = Thread.new do
+      q.pop
+      Dir.chdir(@pwd){} rescue $!
+    end
+    Dir.chdir(@pwd) do
+      q.push nil
+      assert_instance_of(RuntimeError, t.value)
+    end
+  end
+
   def test_chroot_nodir
     skip if RUBY_PLATFORM =~ /android/
     assert_raise(NotImplementedError, Errno::ENOENT, Errno::EPERM