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

1 files changed, 1 insertions, 0 deletions

diff --git a/llvm/lib/Support/TarWriter.cpp b/llvm/lib/Support/TarWriter.cpp
index 5ae64741c52..5009607a478 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;
   }