Index: lib/Fuzzer/FuzzerIOWindows.cpp
===================================================================
--- lib/Fuzzer/FuzzerIOWindows.cpp
+++ lib/Fuzzer/FuzzerIOWindows.cpp
@@ -287,7 +287,12 @@
   return FileName.substr(0, LocationLen + DirLen);
 }
 
-std::string TmpDir() { return "TODO: implement TmpDir"; }
+std::string TmpDir() {
+  if (auto Env = getenv("TMP"))
+    return Env;
+  Printf("Couldn't read TMP environment variable\n");
+  exit(1);
+}
 
 bool IsInterestingCoverageFile(const std::string &FileName) {
   if (FileName.find("Program Files") != std::string::npos)