Index: llvm/lib/Fuzzer/FuzzerDriver.cpp
===================================================================
--- llvm/lib/Fuzzer/FuzzerDriver.cpp
+++ llvm/lib/Fuzzer/FuzzerDriver.cpp
@@ -20,6 +20,7 @@
 #include <algorithm>
 #include <atomic>
 #include <chrono>
+#include <cstdlib>
 #include <cstring>
 #include <mutex>
 #include <string>
@@ -642,6 +643,8 @@
   Options.HandleXfsz = Flags.handle_xfsz;
   SetSignalHandler(Options);
 
+  std::atexit(Fuzzer::StaticExitCallback);
+
   if (Flags.minimize_crash)
     return MinimizeCrashInput(Args, Options);
 
Index: llvm/lib/Fuzzer/FuzzerInternal.h
===================================================================
--- llvm/lib/Fuzzer/FuzzerInternal.h
+++ llvm/lib/Fuzzer/FuzzerInternal.h
@@ -60,6 +60,7 @@
 
   static void StaticAlarmCallback();
   static void StaticCrashSignalCallback();
+  static void StaticExitCallback();
   static void StaticInterruptCallback();
   static void StaticFileSizeExceedCallback();
 
@@ -91,6 +92,7 @@
 private:
   void AlarmCallback();
   void CrashCallback();
+  void ExitCallback();
   void CrashOnOverwrittenData();
   void InterruptCallback();
   void MutateAndTestOne();
Index: llvm/lib/Fuzzer/FuzzerLoop.cpp
===================================================================
--- llvm/lib/Fuzzer/FuzzerLoop.cpp
+++ llvm/lib/Fuzzer/FuzzerLoop.cpp
@@ -175,6 +175,11 @@
   F->CrashCallback();
 }
 
+void Fuzzer::StaticExitCallback() {
+  assert(F);
+  F->ExitCallback();
+}
+
 void Fuzzer::StaticInterruptCallback() {
   assert(F);
   F->InterruptCallback();
@@ -198,6 +203,19 @@
   _Exit(Options.ErrorExitCode);  // Stop right now.
 }
 
+void Fuzzer::ExitCallback() {
+  if (!RunningCB)
+    return; // This exit did not come from the user callback
+  Printf("==%lu== ERROR: libFuzzer: fuzz target exited\n", GetPid());
+  if (EF->__sanitizer_print_stack_trace)
+    EF->__sanitizer_print_stack_trace();
+  Printf("SUMMARY: libFuzzer: fuzz target exited\n");
+  DumpCurrentUnit("crash-");
+  PrintFinalStats();
+  _Exit(Options.ErrorExitCode);
+}
+
+
 void Fuzzer::InterruptCallback() {
   Printf("==%lu== libFuzzer: run interrupted; exiting\n", GetPid());
   PrintFinalStats();
Index: llvm/lib/Fuzzer/test/AbsNegAndConstant64Test.cpp
===================================================================
--- llvm/lib/Fuzzer/test/AbsNegAndConstant64Test.cpp
+++ llvm/lib/Fuzzer/test/AbsNegAndConstant64Test.cpp
@@ -16,6 +16,7 @@
   memcpy(&y, Data + sizeof(x), sizeof(y));
   if (llabs(x) < 0 && y == 0xbaddcafedeadbeefULL) {
     printf("BINGO; Found the target, exiting; x = 0x%lx y 0x%lx\n", x, y);
+    fflush(stdout);
     exit(1);
   }
   return 0;
Index: llvm/lib/Fuzzer/test/AbsNegAndConstantTest.cpp
===================================================================
--- llvm/lib/Fuzzer/test/AbsNegAndConstantTest.cpp
+++ llvm/lib/Fuzzer/test/AbsNegAndConstantTest.cpp
@@ -16,6 +16,7 @@
   memcpy(&y, Data + sizeof(x), sizeof(y));
   if (abs(x) < 0 && y == 0xbaddcafe) {
     printf("BINGO; Found the target, exiting; x = 0x%x y 0x%x\n", x, y);
+    fflush(stdout);
     exit(1);
   }
   return 0;
Index: llvm/lib/Fuzzer/test/BufferOverflowOnInput.cpp
===================================================================
--- llvm/lib/Fuzzer/test/BufferOverflowOnInput.cpp
+++ llvm/lib/Fuzzer/test/BufferOverflowOnInput.cpp
@@ -7,6 +7,7 @@
 #include <cstdint>
 #include <cstdlib>
 #include <iostream>
+#include <ostream>
 
 static volatile bool SeedLargeBuffer;
 
@@ -15,7 +16,7 @@
   if (Size >= 4)
     SeedLargeBuffer = true;
   if (Size == 3 && SeedLargeBuffer && Data[3]) {
-    std::cout << "Woops, reading Data[3] w/o crashing\n";
+    std::cout << "Woops, reading Data[3] w/o crashing\n" << std::flush;
     exit(1);
   }
   return 0;
Index: llvm/lib/Fuzzer/test/CustomCrossOverTest.cpp
===================================================================
--- llvm/lib/Fuzzer/test/CustomCrossOverTest.cpp
+++ llvm/lib/Fuzzer/test/CustomCrossOverTest.cpp
@@ -7,6 +7,7 @@
 #include <cstdint>
 #include <cstdlib>
 #include <iostream>
+#include <ostream>
 #include <random>
 #include <string.h>
 
@@ -26,7 +27,7 @@
   if (Size && Data[0] == 'a') sink--;
 
   if (Str.find(Target) != std::string::npos) {
-    std::cout << "BINGO; Found the target, exiting\n";
+    std::cout << "BINGO; Found the target, exiting\n" << std::flush;
     exit(1);
   }
   return 0;
Index: llvm/lib/Fuzzer/test/CustomMutatorTest.cpp
===================================================================
--- llvm/lib/Fuzzer/test/CustomMutatorTest.cpp
+++ llvm/lib/Fuzzer/test/CustomMutatorTest.cpp
@@ -7,6 +7,7 @@
 #include <cstdint>
 #include <cstdlib>
 #include <iostream>
+#include <ostream>
 
 #include "FuzzerInterface.h"
 
@@ -19,7 +20,7 @@
     if (Size > 1 && Data[1] == 'i') {
       Sink = 2;
       if (Size > 2 && Data[2] == '!') {
-        std::cout << "BINGO; Found the target, exiting\n";
+        std::cout << "BINGO; Found the target, exiting\n" << std::flush;
         exit(1);
       }
     }
Index: llvm/lib/Fuzzer/test/NthRunCrashTest.cpp
===================================================================
--- llvm/lib/Fuzzer/test/NthRunCrashTest.cpp
+++ llvm/lib/Fuzzer/test/NthRunCrashTest.cpp
@@ -5,12 +5,13 @@
 #include <cstddef>
 #include <cstdint>
 #include <iostream>
+#include <ostream>
 
 static int Counter;
 
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
   if (Counter++ == 1000) {
-    std::cout << "BINGO; Found the target, exiting\n";
+    std::cout << "BINGO; Found the target, exiting\n" << std::flush;
     exit(1);
   }
   return 0;
Index: llvm/lib/Fuzzer/test/RepeatedBytesTest.cpp
===================================================================
--- llvm/lib/Fuzzer/test/RepeatedBytesTest.cpp
+++ llvm/lib/Fuzzer/test/RepeatedBytesTest.cpp
@@ -7,6 +7,7 @@
 #include <cstdint>
 #include <cstdlib>
 #include <iostream>
+#include <ostream>
 
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
   assert(Data);
@@ -21,7 +22,8 @@
     MaxA = GT * CurA + (!GT) * MaxA;
   }
   if (MaxA >= 20) {
-    std::cout << "BINGO; Found the target (Max: " << MaxA << "), exiting\n";
+    std::cout << "BINGO; Found the target (Max: " << MaxA << "), exiting\n"
+              << std::flush;
     exit(0);
   }
   return 0;
Index: llvm/lib/Fuzzer/test/SimpleDictionaryTest.cpp
===================================================================
--- llvm/lib/Fuzzer/test/SimpleDictionaryTest.cpp
+++ llvm/lib/Fuzzer/test/SimpleDictionaryTest.cpp
@@ -10,6 +10,7 @@
 #include <cstdlib>
 #include <cstring>
 #include <iostream>
+#include <ostream>
 
 static volatile int Zero = 0;
 
@@ -21,7 +22,7 @@
     if (Expected[i] + Zero == Data[i])
       Match++;
   if (Match == strlen(Expected)) {
-    std::cout << "BINGO; Found the target, exiting\n";
+    std::cout << "BINGO; Found the target, exiting\n" << std::flush;
     exit(1);
   }
   return 0;
Index: llvm/lib/Fuzzer/test/SimpleTest.cpp
===================================================================
--- llvm/lib/Fuzzer/test/SimpleTest.cpp
+++ llvm/lib/Fuzzer/test/SimpleTest.cpp
@@ -7,6 +7,7 @@
 #include <cstdint>
 #include <cstdlib>
 #include <iostream>
+#include <ostream>
 
 static volatile int Sink;
 
@@ -17,7 +18,7 @@
     if (Size > 1 && Data[1] == 'i') {
       Sink = 2;
       if (Size > 2 && Data[2] == '!') {
-        std::cout << "BINGO; Found the target, exiting\n";
+        std::cout << "BINGO; Found the target, exiting\n" << std::flush;
         exit(0);
       }
     }
Index: llvm/lib/Fuzzer/test/SimpleThreadedTest.cpp
===================================================================
--- llvm/lib/Fuzzer/test/SimpleThreadedTest.cpp
+++ llvm/lib/Fuzzer/test/SimpleThreadedTest.cpp
@@ -7,12 +7,13 @@
 #include <cstdint>
 #include <cstring>
 #include <iostream>
+#include <ostream>
 #include <thread>
 
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
   auto C = [&] {
     if (Size >= 2 && Data[0] == 'H') {
-        std::cout << "BINGO; Found the target, exiting\n";
+        std::cout << "BINGO; Found the target, exiting\n" << std::flush;
         abort();
     }
   };
Index: llvm/lib/Fuzzer/test/exit-report.test
===================================================================
--- /dev/null
+++ llvm/lib/Fuzzer/test/exit-report.test
@@ -0,0 +1,5 @@
+RUN: not LLVMFuzzer-SimpleTest 2>&1 | FileCheck %s
+
+CHECK: ERROR: libFuzzer: fuzz target exited
+CHECK: SUMMARY: libFuzzer: fuzz target exited
+CHECK: Test unit written to
Index: llvm/lib/Fuzzer/test/fuzzer-flags.test
===================================================================
--- llvm/lib/Fuzzer/test/fuzzer-flags.test
+++ llvm/lib/Fuzzer/test/fuzzer-flags.test
@@ -1,21 +1,21 @@
 # Does not work on windows for unknown reason.
 UNSUPPORTED: windows
 
-RUN: LLVMFuzzer-FlagsTest -foo_bar=1 2>&1 | FileCheck %s --check-prefix=FOO_BAR
+RUN: not LLVMFuzzer-FlagsTest -foo_bar=1 2>&1 | FileCheck %s --check-prefix=FOO_BAR
 FOO_BAR: WARNING: unrecognized flag '-foo_bar=1'; use -help=1 to list all flags
 FOO_BAR: BINGO
 
-RUN: LLVMFuzzer-FlagsTest -runs=10 --max_len=100 2>&1 | FileCheck %s --check-prefix=DASH_DASH
+RUN: not LLVMFuzzer-FlagsTest -runs=10 --max_len=100 2>&1 | FileCheck %s --check-prefix=DASH_DASH
 DASH_DASH: WARNING: did you mean '-max_len=100' (single dash)?
 DASH_DASH: INFO: A corpus is not provided, starting from an empty corpus
 
 RUN: LLVMFuzzer-FlagsTest -help=1 2>&1 | FileCheck %s --check-prefix=NO_INTERNAL
 NO_INTERNAL-NOT: internal flag
 
-RUN: LLVMFuzzer-FlagsTest --foo-bar -runs=10 -ignore_remaining_args=1 --baz -help=1 test 2>&1 | FileCheck %s --check-prefix=PASSTHRU
+RUN: not LLVMFuzzer-FlagsTest --foo-bar -runs=10 -ignore_remaining_args=1 --baz -help=1 test 2>&1 | FileCheck %s --check-prefix=PASSTHRU
 PASSTHRU: BINGO --foo-bar --baz -help=1 test
 
 RUN: mkdir -p %t/T0 %t/T1
 RUN: touch %t/T1/empty
-RUN: LLVMFuzzer-FlagsTest --foo-bar -merge=1 %t/T0 %t/T1 -ignore_remaining_args=1 --baz -help=1 test 2>&1 | FileCheck %s --check-prefix=PASSTHRU-MERGE
+RUN: not LLVMFuzzer-FlagsTest --foo-bar -merge=1 %t/T0 %t/T1 -ignore_remaining_args=1 --baz -help=1 test 2>&1 | FileCheck %s --check-prefix=PASSTHRU-MERGE
 PASSTHRU-MERGE: BINGO --foo-bar --baz -help=1 test
Index: llvm/lib/Fuzzer/test/fuzzer-printcovpcs.test
===================================================================
--- llvm/lib/Fuzzer/test/fuzzer-printcovpcs.test
+++ llvm/lib/Fuzzer/test/fuzzer-printcovpcs.test
@@ -1,4 +1,4 @@
-RUN: LLVMFuzzer-SimpleTest -print_pcs=1 -seed=1 2>&1 | FileCheck %s --check-prefix=PCS
+RUN: not LLVMFuzzer-SimpleTest -print_pcs=1 -seed=1 2>&1 | FileCheck %s --check-prefix=PCS
 PCS-NOT: NEW_PC
 PCS:INITED
 PCS:NEW_PC: {{0x[a-f0-9]+}}
Index: llvm/lib/Fuzzer/test/fuzzer.test
===================================================================
--- llvm/lib/Fuzzer/test/fuzzer.test
+++ llvm/lib/Fuzzer/test/fuzzer.test
@@ -1,10 +1,10 @@
 CHECK: BINGO
 Done1000000: Done 1000000 runs in
 
-RUN: LLVMFuzzer-SimpleTest 2>&1 | FileCheck %s
+RUN: not LLVMFuzzer-SimpleTest 2>&1 | FileCheck %s
 
 # only_ascii mode. Will perform some minimal self-validation.
-RUN: LLVMFuzzer-SimpleTest -only_ascii=1 2>&1
+RUN: not LLVMFuzzer-SimpleTest -only_ascii=1 2>&1
 
 RUN: LLVMFuzzer-SimpleCmpTest -max_total_time=1 -use_cmp=0 2>&1 | FileCheck %s --check-prefix=MaxTotalTime
 MaxTotalTime: Done {{.*}} runs in {{.}} second(s)
@@ -47,7 +47,7 @@
 DSO: INFO: Loaded 3 modules
 DSO: BINGO
 
-RUN: LLVMFuzzer-SimpleTest  -exit_on_src_pos=SimpleTest.cpp:17                 2>&1 | FileCheck %s --check-prefix=EXIT_ON_SRC_POS
+RUN: LLVMFuzzer-SimpleTest  -exit_on_src_pos=SimpleTest.cpp:18                 2>&1 | FileCheck %s --check-prefix=EXIT_ON_SRC_POS
 RUN: LLVMFuzzer-ShrinkControlFlowTest  -exit_on_src_pos=ShrinkControlFlowTest.cpp:23 2>&1 | FileCheck %s --check-prefix=EXIT_ON_SRC_POS
 EXIT_ON_SRC_POS: INFO: found line matching '{{.*}}', exiting.
 
Index: llvm/lib/Fuzzer/test/inline-8bit-counters.test
===================================================================
--- llvm/lib/Fuzzer/test/inline-8bit-counters.test
+++ llvm/lib/Fuzzer/test/inline-8bit-counters.test
@@ -1,4 +1,4 @@
 REQUIRES: linux
 CHECK: INFO: Loaded 1 modules with {{.*}} inline 8-bit counters
 CHECK: BINGO
-RUN: LLVMFuzzer-SimpleTest-Inline8bitCounters -runs=1000000 -seed=1 2>&1 | FileCheck %s
+RUN: not LLVMFuzzer-SimpleTest-Inline8bitCounters -runs=1000000 -seed=1 2>&1 | FileCheck %s
Index: llvm/lib/Fuzzer/test/repeated-bytes.test
===================================================================
--- llvm/lib/Fuzzer/test/repeated-bytes.test
+++ llvm/lib/Fuzzer/test/repeated-bytes.test
@@ -1,2 +1,2 @@
 CHECK: BINGO
-RUN: LLVMFuzzer-RepeatedBytesTest -seed=1 -runs=1000000 2>&1 | FileCheck %s
+RUN: not LLVMFuzzer-RepeatedBytesTest -seed=1 -runs=1000000 2>&1 | FileCheck %s
Index: llvm/lib/Fuzzer/test/trace-pc.test
===================================================================
--- llvm/lib/Fuzzer/test/trace-pc.test
+++ llvm/lib/Fuzzer/test/trace-pc.test
@@ -1,2 +1,2 @@
 CHECK: BINGO
-RUN: LLVMFuzzer-SimpleTest-TracePC -runs=100000 -seed=1 2>&1 | FileCheck %s
+RUN: not LLVMFuzzer-SimpleTest-TracePC -runs=100000 -seed=1 2>&1 | FileCheck %s
Index: llvm/lib/Fuzzer/test/ulimit.test
===================================================================
--- llvm/lib/Fuzzer/test/ulimit.test
+++ llvm/lib/Fuzzer/test/ulimit.test
@@ -1,4 +1,4 @@
 REQUIRES: posix
 
 RUN: ulimit -s 1000
-RUN: LLVMFuzzer-SimpleTest
+RUN: not LLVMFuzzer-SimpleTest