Index: include/llvm/DebugInfo/MSF/MSFCommon.h
===================================================================
--- include/llvm/DebugInfo/MSF/MSFCommon.h
+++ include/llvm/DebugInfo/MSF/MSFCommon.h
@@ -50,8 +50,7 @@
 };
 
 struct MSFLayout {
-  MSFLayout() : SB(nullptr) {}
-  const SuperBlock *SB;
+  const SuperBlock *SB = nullptr;
   BitVector FreePageMap;
   ArrayRef<support::ulittle32_t> DirectoryBlocks;
   ArrayRef<support::ulittle32_t> StreamSizes;
Index: include/llvm/DebugInfo/PDB/Raw/PDBFileBuilder.h
===================================================================
--- include/llvm/DebugInfo/PDB/Raw/PDBFileBuilder.h
+++ include/llvm/DebugInfo/PDB/Raw/PDBFileBuilder.h
@@ -38,6 +38,7 @@
 
   Error initialize(const msf::SuperBlock &Super);
 
+  msf::MSFLayout &getMsf();
   msf::MSFBuilder &getMsfBuilder();
   InfoStreamBuilder &getInfoBuilder();
   DbiStreamBuilder &getDbiBuilder();
@@ -49,12 +50,13 @@
 
   Error commit(const msf::WritableStream &Buffer);
 
-private:
-  Expected<msf::MSFLayout> finalizeMsfLayout() const;
+  Error finalizeMsfLayout();
 
+private:
   BumpPtrAllocator &Allocator;
 
-  std::unique_ptr<msf::MSFBuilder> Msf;
+  std::unique_ptr<msf::MSFLayout> Msf;
+  std::unique_ptr<msf::MSFBuilder> MsfBuilder;
   std::unique_ptr<InfoStreamBuilder> Info;
   std::unique_ptr<DbiStreamBuilder> Dbi;
   std::unique_ptr<TpiStreamBuilder> Tpi;
Index: lib/DebugInfo/PDB/Raw/PDBFileBuilder.cpp
===================================================================
--- lib/DebugInfo/PDB/Raw/PDBFileBuilder.cpp
+++ lib/DebugInfo/PDB/Raw/PDBFileBuilder.cpp
@@ -32,6 +32,11 @@
     : Allocator(Allocator) {}
 
 Error PDBFileBuilder::initialize(const msf::SuperBlock &Super) {
+  auto ExpectedMsfBuilder =
+      MSFBuilder::create(Allocator, Super.BlockSize);
+  if (!ExpectedMsfBuilder)
+    return ExpectedMsfBuilder.takeError();
+
   auto ExpectedMsf =
       MSFBuilder::create(Allocator, Super.BlockSize, Super.NumBlocks);
   if (!ExpectedMsf)
@@ -43,64 +48,70 @@
   Msf = llvm::make_unique<MSFBuilder>(std::move(MsfResult));
   Msf->setFreePageMap(Super.FreeBlockMapBlock);
   Msf->setUnknown1(Super.Unknown1);
-  return Error::success();
 }
 
-MSFBuilder &PDBFileBuilder::getMsfBuilder() { return *Msf; }
+MSFLayout &PDBFileBuilder::getMsf() { return *Msf; }
+
+MSFBuilder &PDBFileBuilder::getMsfBuilder() { return *MsfBuilder; }
 
 InfoStreamBuilder &PDBFileBuilder::getInfoBuilder() {
   if (!Info)
-    Info = llvm::make_unique<InfoStreamBuilder>(*Msf);
+    Info = llvm::make_unique<InfoStreamBuilder>(*MsfBuilder);
   return *Info;
 }
 
 DbiStreamBuilder &PDBFileBuilder::getDbiBuilder() {
   if (!Dbi)
-    Dbi = llvm::make_unique<DbiStreamBuilder>(*Msf);
+    Dbi = llvm::make_unique<DbiStreamBuilder>(*MsfBuilder);
   return *Dbi;
 }
 
 TpiStreamBuilder &PDBFileBuilder::getTpiBuilder() {
   if (!Tpi)
-    Tpi = llvm::make_unique<TpiStreamBuilder>(*Msf, StreamTPI);
+    Tpi = llvm::make_unique<TpiStreamBuilder>(*MsfBuilder, StreamTPI);
   return *Tpi;
 }
 
 TpiStreamBuilder &PDBFileBuilder::getIpiBuilder() {
   if (!Ipi)
-    Ipi = llvm::make_unique<TpiStreamBuilder>(*Msf, StreamIPI);
+    Ipi = llvm::make_unique<TpiStreamBuilder>(*MsfBuilder, StreamIPI);
   return *Ipi;
 }
 
-Expected<msf::MSFLayout> PDBFileBuilder::finalizeMsfLayout() const {
+Error PDBFileBuilder::finalizeMsfLayout() {
+  if (Msf)
+    return Error::success();
   if (Info) {
     if (auto EC = Info->finalizeMsfLayout())
-      return std::move(EC);
+      return EC;
   }
   if (Dbi) {
     if (auto EC = Dbi->finalizeMsfLayout())
-      return std::move(EC);
+      return EC;
   }
   if (Tpi) {
     if (auto EC = Tpi->finalizeMsfLayout())
-      return std::move(EC);
+      return EC;
   }
   if (Ipi) {
     if (auto EC = Ipi->finalizeMsfLayout())
-      return std::move(EC);
+      return EC;
   }
 
-  return Msf->build();
+  Expected<msf::MSFLayout> ExpectedMsf = MsfBuilder->build();
+  if (!ExpectedMsf)
+    return ExpectedMsf.takeError();
+  Msf.reset(new MSFLayout(*ExpectedMsf));
+  return Error::success();
 }
 
 Expected<std::unique_ptr<PDBFile>>
 PDBFileBuilder::build(std::unique_ptr<msf::WritableStream> PdbFileBuffer) {
-  auto ExpectedLayout = finalizeMsfLayout();
-  if (!ExpectedLayout)
-    return ExpectedLayout.takeError();
+  if (Error E = finalizeMsfLayout())
+    return std::move(E);
 
   auto File = llvm::make_unique<PDBFile>(std::move(PdbFileBuffer), Allocator);
-  File->ContainerLayout = *ExpectedLayout;
+  File->ContainerLayout = *Msf;
 
   if (Info) {
     auto ExpectedInfo = Info->build(*File, *PdbFileBuffer);
@@ -140,10 +151,9 @@
 
 Error PDBFileBuilder::commit(const msf::WritableStream &Buffer) {
   StreamWriter Writer(Buffer);
-  auto ExpectedLayout = finalizeMsfLayout();
-  if (!ExpectedLayout)
-    return ExpectedLayout.takeError();
-  auto &Layout = *ExpectedLayout;
+  if (Error E = finalizeMsfLayout())
+    return E;
+  msf::MSFLayout &Layout = *Msf;
 
   if (auto EC = Writer.writeObject(*Layout.SB))
     return EC;
@@ -189,4 +199,4 @@
   }
 
   return Buffer.commit();
-}
\ No newline at end of file
+}