[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.

llvm-svn: 243944

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/IR/Type.cpp b/llvm/lib/IR/Type.cpp
index 1b46b7b01cb..18c2e8c2b48 100644
--- a/llvm/lib/IR/Type.cpp
+++ b/llvm/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);