From: David Greene <greened@obbligato.org>
Date: Thu, 10 Jan 2013 18:17:54 +0000 (+0000)
Subject: Fix Alias Bug
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=5e1b31bf5588cd9ea0b16e94fcc1d908e40027e2;p=oota-llvm.git

Fix Alias Bug

Use memcpy to do type punning instead of a cast.  A cast or similar
operation through a union breaks strict aliasing rules.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172081 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/unittests/Support/YAMLIOTest.cpp b/unittests/Support/YAMLIOTest.cpp
index afa71cc25ea..a39fbebf295 100644
--- a/unittests/Support/YAMLIOTest.cpp
+++ b/unittests/Support/YAMLIOTest.cpp
@@ -783,10 +783,18 @@ namespace yaml {
     static void mapping(IO &io, KindAndFlags& kf) {
       io.mapRequired("kind",  kf.kind);
       // type of flags field varies depending on kind field
-      if ( kf.kind == kindA )
-        io.mapRequired("flags", *((AFlags*)&kf.flags));
-      else
-        io.mapRequired("flags", *((BFlags*)&kf.flags));
+
+      // Use memcpy here to avoid breaking strict aliasing rules.
+      if ( kf.kind == kindA ) {
+        AFlags aflags;
+        memcpy(&aflags, &kf.flags, sizeof(aflags));
+        io.mapRequired("flags", aflags);
+      }
+      else {
+        BFlags bflags;
+        memcpy(&bflags, &kf.flags, sizeof(bflags));
+        io.mapRequired("flags", bflags);
+      }
     }
   };
 }