From 5908845a7e7c6db39e100246a3875f519f5d1f97 Mon Sep 17 00:00:00 2001
From: Rui Ueyama <ruiu@google.com>
Date: Thu, 28 Sep 2017 00:27:39 +0000
Subject: [PATCH] Fix a UBsan bot.

If we do not initialize Prefix here, Prefix.data() returns a nullptr.
Later, it is passed to memcpy. memcpy's behavior is undefined if src (or
dst) is a nullptr even if a given size is 0. That's why this code
triggered UBsan.

llvm-svn: 314368
---
 llvm/lib/Support/TarWriter.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/llvm/lib/Support/TarWriter.cpp b/llvm/lib/Support/TarWriter.cpp
index 5ae6474..5009607 100644
--- a/llvm/lib/Support/TarWriter.cpp
+++ b/llvm/lib/Support/TarWriter.cpp
@@ -127,6 +127,7 @@ static void writePaxHeader(raw_fd_ostream &OS, StringRef Path) {
 // Otherwise, returns false.
 static bool splitUstar(StringRef Path, StringRef &Prefix, StringRef &Name) {
   if (Path.size() < sizeof(UstarHeader::Name)) {
+    Prefix = "";
     Name = Path;
     return true;
   }
-- 
2.7.4