X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=folly%2FLazy.h;h=bb6411f8e44809470f03d1585505f36c175f9d8e;hb=4a9aef96b778f9fa7b31f94196e46b5733335326;hp=2b18ea7b84b36fdb9588c96a87d0f949a8bf6009;hpb=12c8603da89f7ea8f2fbd0a414125aa8117ac97b;p=folly.git

diff --git a/folly/Lazy.h b/folly/Lazy.h
index 2b18ea7b..bb6411f8 100644
--- a/folly/Lazy.h
+++ b/folly/Lazy.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2013 Facebook, Inc.
+ * Copyright 2014 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,7 +19,7 @@
 #include <utility>
 #include <type_traits>
 
-#include "folly/Optional.h"
+#include <folly/Optional.h>
 
 namespace folly {
 
@@ -35,8 +35,8 @@ namespace folly {
  * The value is created using folly::lazy, usually with a lambda, and
  * its value is requested using operator().
  *
- * Note that the value is not safe for current accesses by multiple
- * threads, even if you declare it const.
+ * Note that the value is not safe for concurrent accesses by multiple
+ * threads, even if you declare it const.  See note below.
  *
  *
  * Example Usage:
@@ -70,6 +70,16 @@ namespace folly {
  *      value unnecessarily.  Sharing with mutable lazies would also
  *      leave them with non-value semantics despite looking
  *      value-like.
+ *
+ *    - Not thread safe for const accesses.  Many use cases for lazy
+ *      values are local variables on the stack, where multiple
+ *      threads shouldn't even be able to reach the value.  It still
+ *      is useful to indicate/check that the value doesn't change with
+ *      const, particularly when it is captured by a large family of
+ *      lambdas.  Adding internal synchronization seems like it would
+ *      pessimize the most common use case in favor of less likely use
+ *      cases.
+ *
  */
 
 //////////////////////////////////////////////////////////////////////