From 1a092e8289d0572ba77aaa769e30896e390d25b9 Mon Sep 17 00:00:00 2001
From: Chandler Carruth <chandlerc@gmail.com>
Date: Tue, 4 Aug 2015 03:48:26 +0000
Subject: [PATCH] [UB] Don't allocate space for contained types and then try to
 copy the contained types into the space when we have no contained types. This
 fixes the UB stemming from a call to memcpy with a null pointer. This also
 reduces the calls to allocate because this actually happens in a notable
 client - Clang.

Found by UBSan.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@243944 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/IR/Type.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/lib/IR/Type.cpp b/lib/IR/Type.cpp
index 1b46b7b01cb..18c2e8c2b48 100644
--- a/lib/IR/Type.cpp
+++ b/lib/IR/Type.cpp
@@ -420,6 +420,12 @@ void StructType::setBody(ArrayRef<Type*> Elements, bool isPacked) {
   if (isPacked)
     setSubclassData(getSubclassData() | SCDB_Packed);
 
+  if (Elements.empty()) {
+    ContainedTys = nullptr;
+    NumContainedTys = 0;
+    return;
+  }
+
   unsigned NumElements = Elements.size();
   Type **Elts = getContext().pImpl->TypeAllocator.Allocate<Type*>(NumElements);
   memcpy(Elts, Elements.data(), sizeof(Elements[0]) * NumElements);
-- 
2.34.1