1 files changed, 75 insertions, 0 deletions
diff --git a/www/compatibility.html b/www/compatibility.html
index 0f8409b..cf0d96e 100644
--- a/www/compatibility.html
+++ b/www/compatibility.html
@@ -33,6 +33,7 @@
     <ul>
       <li><a href="#inline">C99 inline functions</a></li>
       <li><a href="#lvalue-cast">Lvalue casts</a></li>
+      <li><a href="#blocks-in-protected-scope">Jumps to within <tt>__block</tt> variable scope</a></li>
     </ul>
   </li>
   <li><a href="#objective-c">Objective-C compatibility</a>
@@ -58,6 +59,9 @@
     <ul>
       <li><a href="#implicit-downcasts">Implicit downcasts</a></li>
     </ul>
+    <ul>
+      <li><a href="#Use of class as method name">Use of class as method name</a></li>
+    </ul>
   </li>
 </ul>
 
@@ -132,6 +136,55 @@ example, one could use:</p>
 </pre>
 
 <!-- ======================================================================= -->
+<h3 id="blocks-in-protected-scope">Jumps to within <tt>__block</tt> variable scope</h3>
+<!-- ======================================================================= -->
+
+<p>Clang disallows jumps into the scope of a <tt>__block</tt> variable, similar
+to the manner in which both GCC and Clang disallow jumps into the scope of
+variables which have user defined constructors (in C++).</p>
+
+<p>Variables marked with <tt>__block</tt> require special runtime initialization
+before they can be used. A jump into the scope of a <tt>__block</tt> variable
+would bypass this initialization and therefore the variable cannot safely be
+used.</p>
+
+<p>For example, consider the following code fragment:</p>
+
+<pre>
+int f0(int c) {
+  if (c)
+    goto error;
+
+  __block int x;
+  x = 1;
+  return x;
+
+ error:
+  x = 0;
+  return x;
+}
+</pre>
+
+<p>GCC accepts this code, but it will crash at runtime along the error path,
+because the runtime setup for the storage backing the <tt>x</tt> variable will
+not have been initialized. Clang rejects this code with a hard error:</p>
+
+<pre>
+t.c:3:5: error: goto into protected scope
+    goto error;
+    ^
+t.c:5:15: note: jump bypasses setup of __block variable
+  __block int x;
+              ^
+</pre>
+
+<p>Some instances of this construct may be safe if the variable is never used
+after the jump target, however the protected scope checker does not check the
+uses of the variable, only the scopes in which it is visible. You should rewrite
+your code to put the <tt>__block</tt> variables in a scope which is only visible
+where they are used.</p>
+
+<!-- ======================================================================= -->
 <h2 id="objective-c">Objective-C compatibility</h3>
 <!-- ======================================================================= -->
 
@@ -604,6 +657,28 @@ explicit cast:</p>
   f((Derived *)base);
 </pre>
 
+<!-- ======================================================================= -->
+<h3 id="Use of class as method name">Use of class as method name</h3>
+<!-- ======================================================================= -->
+
+<p>Use of 'class' name to declare a method is allowed in objective-c++ mode to
+be compatible with GCC. However, use of property dot syntax notation to call
+this method is not allowed in clang++, as [I class] is a suitable syntax that 
+will work. So, this test will fail in clang++.
+
+<pre>
+@interface I {
+int cls;
+}
++ (int)class;
+@end
+
+@implementation  I
+- (int) Meth { return I.class; }
+@end
+<pre>
+
+
 </div>
 </body>
 </html>