[libFuzzer] make sure we find buffer overflow in the input buffer. Previously, re-using the same vector object was hiding buffer overflows (unless we used annotated vector)

llvm-svn: 257701

1 files changed, 20 insertions, 0 deletions

diff --git a/llvm/lib/Fuzzer/test/BufferOverflowOnInput.cpp b/llvm/lib/Fuzzer/test/BufferOverflowOnInput.cpp
new file mode 100644
index 0000000..9bebd84
--- /dev/null
+++ b/llvm/lib/Fuzzer/test/BufferOverflowOnInput.cpp
@@ -0,0 +1,20 @@
+// Simple test for a fuzzer. The fuzzer must find the string "Hi!".
+#include <assert.h>
+#include <cstdint>
+#include <cstdlib>
+#include <cstddef>
+#include <iostream>
+
+static volatile bool SeedLargeBuffer;
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
+  assert(Data);
+  if (Size >= 4)
+    SeedLargeBuffer = true;
+  if (Size == 3 && SeedLargeBuffer && Data[3]) {
+    std::cout << "Woops, reading Data[3] w/o crashing\n";
+    exit(1);
+  }
+  return 0;
+}
+