[libFuzzer] make trace-based fuzzing not crash in presence of threads

llvm-svn: 256876

3 files changed, 31 insertions, 0 deletions

diff --git a/llvm/lib/Fuzzer/test/CMakeLists.txt b/llvm/lib/Fuzzer/test/CMakeLists.txt
index 674fcc3c9f8..cd0b167eb38 100644
--- a/llvm/lib/Fuzzer/test/CMakeLists.txt
+++ b/llvm/lib/Fuzzer/test/CMakeLists.txt
@@ -26,6 +26,7 @@ set(Tests
   StrcmpTest
   StrncmpTest
   SwitchTest
+  ThreadedTest
   TimeoutTest
   )
 
diff --git a/llvm/lib/Fuzzer/test/ThreadedTest.cpp b/llvm/lib/Fuzzer/test/ThreadedTest.cpp
new file mode 100644
index 00000000000..7aa114a41f3
--- /dev/null
+++ b/llvm/lib/Fuzzer/test/ThreadedTest.cpp
@@ -0,0 +1,23 @@
+// Threaded test for a fuzzer. The fuzzer should not crash.
+#include <assert.h>
+#include <cstdint>
+#include <cstddef>
+#include <cstring>
+#include <thread>
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
+  if (Size < 8) return 0;
+  assert(Data);
+  auto C = [&] {
+    size_t Res = 0;
+    for (size_t i = 0; i < Size / 2; i++)
+      Res += memcmp(Data, Data + Size / 2, 4);
+    return Res;
+  };
+  std::thread T[] = {std::thread(C), std::thread(C), std::thread(C),
+                     std::thread(C), std::thread(C), std::thread(C)};
+  for (auto &X : T)
+    X.join();
+  return 0;
+}
+
diff --git a/llvm/lib/Fuzzer/test/fuzzer-threaded.test b/llvm/lib/Fuzzer/test/fuzzer-threaded.test
new file mode 100644
index 00000000000..c58a33456cc
--- /dev/null
+++ b/llvm/lib/Fuzzer/test/fuzzer-threaded.test
@@ -0,0 +1,7 @@
+CHECK: Done 1000 runs in
+
+RUN: LLVMFuzzer-ThreadedTest -use_traces=1 -runs=1000  2>&1 | FileCheck %s
+RUN: LLVMFuzzer-ThreadedTest -use_traces=1 -runs=1000  2>&1 | FileCheck %s
+RUN: LLVMFuzzer-ThreadedTest -use_traces=1 -runs=1000  2>&1 | FileCheck %s
+RUN: LLVMFuzzer-ThreadedTest -use_traces=1 -runs=1000  2>&1 | FileCheck %s
+