[llvm] r340170 - Fix an undefined behavior when storing an empty StringRef.

[Haojian Wu via llvm-commits]

Author: hokein
Date: Mon Aug 20 06:12:54 2018
New Revision: 340170

URL: http://llvm.org/viewvc/llvm-project?rev=340170&view=rev
Log:
Fix an undefined behavior when storing an empty StringRef.

Summary: Passing a nullptr to memcpy is UB.

Reviewers: ioeric

Subscribers: llvm-commits, cfe-commits

Differential Revision: https://reviews.llvm.org/D50966

Modified:
    llvm/trunk/lib/Support/StringSaver.cpp

Modified: llvm/trunk/lib/Support/StringSaver.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/StringSaver.cpp?rev=340170&r1=340169&r2=340170&view=diff
==============================================================================
--- llvm/trunk/lib/Support/StringSaver.cpp (original)
+++ llvm/trunk/lib/Support/StringSaver.cpp Mon Aug 20 06:12:54 2018
@@ -13,7 +13,8 @@ using namespace llvm;
 
 StringRef StringSaver::save(StringRef S) {
   char *P = Alloc.Allocate<char>(S.size() + 1);
-  memcpy(P, S.data(), S.size());
+  if (!S.empty())
+    memcpy(P, S.data(), S.size());
   P[S.size()] = '\0';
   return StringRef(P, S.size());
 }