Index: compiler-rt/lib/fuzzer/tests/FuzzerTestUtil.h
===================================================================
--- compiler-rt/lib/fuzzer/tests/FuzzerTestUtil.h
+++ compiler-rt/lib/fuzzer/tests/FuzzerTestUtil.h
@@ -11,21 +11,31 @@
 #ifndef LLVM_FUZZER_TEST_UTIL_H
 #define LLVM_FUZZER_TEST_UTIL_H
 
+#include "FuzzerExtFunctions.h"
 #include "FuzzerTracePC.h"
 #include "gtest/gtest.h"
 #include <cstddef>
 #include <cstdint>
 #include <initializer_list>
 #include <memory>
-#include <vector>
 
 namespace fuzzer {
 
 // Helper environment to ensure that:
 // * The PRNG is seeded deterministically.
+// * The ExternalFunctions are allocated.
 class TestEnvironment : public testing::Environment {
 public:
-  void SetUp() override { srand(0); }
+  void SetUp() override {
+    srand(0);
+    ExtFuncs.reset(new ExternalFunctions());
+    EF = ExtFuncs.get();
+  }
+
+  void TearDown() override { EF = nullptr; }
+
+private:
+  std::unique_ptr<ExternalFunctions> ExtFuncs;
 };
 
 // Test utilities for picking repeatable psuedorandom numbers.
Index: compiler-rt/lib/fuzzer/tests/FuzzerUnittest.cpp
===================================================================
--- compiler-rt/lib/fuzzer/tests/FuzzerUnittest.cpp
+++ compiler-rt/lib/fuzzer/tests/FuzzerUnittest.cpp
@@ -48,8 +48,6 @@
 }
 
 TEST(Fuzzer, CrossOver) {
-  std::unique_ptr<ExternalFunctions> t(new ExternalFunctions());
-  fuzzer::EF = t.get();
   Random Rand(0);
   std::unique_ptr<MutationDispatcher> MD(new MutationDispatcher(Rand, {}));
   Unit A({0, 1, 2}), B({5, 6, 7});
@@ -118,8 +116,6 @@
                                               size_t MaxSize);
 
 void TestEraseBytes(Mutator M, int NumIter) {
-  std::unique_ptr<ExternalFunctions> t(new ExternalFunctions());
-  fuzzer::EF = t.get();
   uint8_t REM0[8] = {0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77};
   uint8_t REM1[8] = {0x00, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77};
   uint8_t REM2[8] = {0x00, 0x11, 0x33, 0x44, 0x55, 0x66, 0x77};
@@ -172,8 +168,6 @@
 }
 
 void TestInsertByte(Mutator M, int NumIter) {
-  std::unique_ptr<ExternalFunctions> t(new ExternalFunctions());
-  fuzzer::EF = t.get();
   Random Rand(0);
   std::unique_ptr<MutationDispatcher> MD(new MutationDispatcher(Rand, {}));
   int FoundMask = 0;
@@ -208,8 +202,6 @@
 }
 
 void TestInsertRepeatedBytes(Mutator M, int NumIter) {
-  std::unique_ptr<ExternalFunctions> t(new ExternalFunctions());
-  fuzzer::EF = t.get();
   Random Rand(0);
   std::unique_ptr<MutationDispatcher> MD(new MutationDispatcher(Rand, {}));
   int FoundMask = 0;
@@ -252,8 +244,6 @@
 }
 
 void TestChangeByte(Mutator M, int NumIter) {
-  std::unique_ptr<ExternalFunctions> t(new ExternalFunctions());
-  fuzzer::EF = t.get();
   Random Rand(0);
   std::unique_ptr<MutationDispatcher> MD(new MutationDispatcher(Rand, {}));
   int FoundMask = 0;
@@ -288,8 +278,6 @@
 }
 
 void TestChangeBit(Mutator M, int NumIter) {
-  std::unique_ptr<ExternalFunctions> t(new ExternalFunctions());
-  fuzzer::EF = t.get();
   Random Rand(0);
   std::unique_ptr<MutationDispatcher> MD(new MutationDispatcher(Rand, {}));
   int FoundMask = 0;
@@ -324,8 +312,6 @@
 }
 
 void TestShuffleBytes(Mutator M, int NumIter) {
-  std::unique_ptr<ExternalFunctions> t(new ExternalFunctions());
-  fuzzer::EF = t.get();
   Random Rand(0);
   std::unique_ptr<MutationDispatcher> MD(new MutationDispatcher(Rand, {}));
   int FoundMask = 0;
@@ -354,8 +340,6 @@
 }
 
 void TestCopyPart(Mutator M, int NumIter) {
-  std::unique_ptr<ExternalFunctions> t(new ExternalFunctions());
-  fuzzer::EF = t.get();
   Random Rand(0);
   std::unique_ptr<MutationDispatcher> MD(new MutationDispatcher(Rand, {}));
   int FoundMask = 0;
@@ -404,8 +388,6 @@
   // This (non exhaustively) tests if `Mutate_CopyPart` tries to perform an
   // insert on an input of size `MaxSize`.  Performing an insert in this case
   // will lead to the mutation failing.
-  std::unique_ptr<ExternalFunctions> t(new ExternalFunctions());
-  fuzzer::EF = t.get();
   Random Rand(0);
   std::unique_ptr<MutationDispatcher> MD(new MutationDispatcher(Rand, {}));
   uint8_t Data[8] = {0x00, 0x11, 0x22, 0x33, 0x44, 0x00, 0x11, 0x22};
@@ -417,8 +399,6 @@
 }
 
 void TestAddWordFromDictionary(Mutator M, int NumIter) {
-  std::unique_ptr<ExternalFunctions> t(new ExternalFunctions());
-  fuzzer::EF = t.get();
   Random Rand(0);
   std::unique_ptr<MutationDispatcher> MD(new MutationDispatcher(Rand, {}));
   uint8_t Word1[4] = {0xAA, 0xBB, 0xCC, 0xDD};
@@ -459,8 +439,6 @@
 }
 
 void TestChangeASCIIInteger(Mutator M, int NumIter) {
-  std::unique_ptr<ExternalFunctions> t(new ExternalFunctions());
-  fuzzer::EF = t.get();
   Random Rand(0);
   std::unique_ptr<MutationDispatcher> MD(new MutationDispatcher(Rand, {}));
 
@@ -491,8 +469,6 @@
 }
 
 void TestChangeBinaryInteger(Mutator M, int NumIter) {
-  std::unique_ptr<ExternalFunctions> t(new ExternalFunctions());
-  fuzzer::EF = t.get();
   Random Rand(0);
   std::unique_ptr<MutationDispatcher> MD(new MutationDispatcher(Rand, {}));