[MachineVerifier] Avoid reference to nullptr

Instantiation of the MachineVerifierPass through
PassInfo::getNormalCtor would yield a segfault since the default
constructor of the MachineVerifierPass takes a reference to nullptr.

Patch by Simone Pellegrini.

Differential Revision: https://reviews.llvm.org/D31387

llvm-svn: 298987

diff --git a/llvm/lib/CodeGen/MachineVerifier.cpp b/llvm/lib/CodeGen/MachineVerifier.cpp
index 15694cb..5c263b3 100644 (file)
--- a/llvm/lib/CodeGen/MachineVerifier.cpp
+++ b/llvm/lib/CodeGen/MachineVerifier.cpp
@@ -260,8 +260,8 @@ namespace {
     static char ID; // Pass ID, replacement for typeid
     const std::string Banner;
 
-    MachineVerifierPass(const std::string &banner = nullptr)
-      : MachineFunctionPass(ID), Banner(banner) {
+    MachineVerifierPass(const std::string banner = std::string())
+      : MachineFunctionPass(ID), Banner(std::move(banner)) {
         initializeMachineVerifierPassPass(*PassRegistry::getPassRegistry());
       }