From 09087bba4d3de1aecdb9d47b0e8b783ce8ec2e42 Mon Sep 17 00:00:00 2001
From: Kostya Serebryany <kcc@google.com>
Date: Mon, 18 Apr 2016 21:14:11 +0000
Subject: [PATCH] [libFuzzer] warn if the corpus is empty

llvm-svn: 266670
---
 llvm/lib/Fuzzer/FuzzerDriver.cpp | 5 ++++-
 llvm/lib/Fuzzer/test/fuzzer.test | 1 +
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/Fuzzer/FuzzerDriver.cpp b/llvm/lib/Fuzzer/FuzzerDriver.cpp
index e5cca6eae7db..57532b4da0a8 100644
--- a/llvm/lib/Fuzzer/FuzzerDriver.cpp
+++ b/llvm/lib/Fuzzer/FuzzerDriver.cpp
@@ -376,8 +376,11 @@ static int FuzzerDriver(const std::vector<std::string> &Args,
     F.SetMaxLen(
         std::min(std::max(kMinDefaultLen, F.MaxUnitSizeInCorpus()), kMaxSaneLen));
 
-  if (F.CorpusSize() == 0)
+  if (F.CorpusSize() == 0) {
     F.AddToCorpus(Unit());  // Can't fuzz empty corpus, so add an empty input.
+    if (Options.Verbosity)
+      Printf("INFO: A corpus is not provided, starting from an empty corpus\n");
+  }
   F.ShuffleAndMinimize();
   if (Flags.drill)
     F.Drill();
diff --git a/llvm/lib/Fuzzer/test/fuzzer.test b/llvm/lib/Fuzzer/test/fuzzer.test
index b42a49b8d7f9..8794e88dd224 100644
--- a/llvm/lib/Fuzzer/test/fuzzer.test
+++ b/llvm/lib/Fuzzer/test/fuzzer.test
@@ -118,3 +118,4 @@ FD_MASK_3: INITED
 
 RUN: LLVMFuzzer-SimpleTest -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