[libFuzzer] make len_control less agressive: set the initial max len to the length of the largest seed. This was the original intent, but... Now, with a test, to ensure it stays this way

llvm-svn: 354191

1 files changed, 5 insertions, 1 deletions

diff --git a/compiler-rt/lib/fuzzer/FuzzerLoop.cpp b/compiler-rt/lib/fuzzer/FuzzerLoop.cpp
index 75dc600870a..b86512b1255 100644
--- a/compiler-rt/lib/fuzzer/FuzzerLoop.cpp
+++ b/compiler-rt/lib/fuzzer/FuzzerLoop.cpp
@@ -153,7 +153,7 @@ Fuzzer::Fuzzer(UserCallback CB, InputCorpus &Corpus, MutationDispatcher &MD,
   if (!Options.OutputCorpus.empty() && Options.ReloadIntervalSec)
     EpochOfLastReadOfOutputCorpus = GetEpoch(Options.OutputCorpus);
   MaxInputLen = MaxMutationLen = Options.MaxLen;
-  TmpMaxMutationLen = Max(size_t(4), Corpus.MaxInputSize());
+  TmpMaxMutationLen = 0;  // Will be set once we load the corpus.
   AllocateCurrentUnitData();
   CurrentUnitSize = 0;
   memset(BaseSha1, 0, sizeof(BaseSha1));
@@ -781,6 +781,10 @@ void Fuzzer::Loop(const Vector<std::string> &CorpusDirs,
   TPC.SetPrintNewPCs(Options.PrintNewCovPcs);
   TPC.SetPrintNewFuncs(Options.PrintNewCovFuncs);
   system_clock::time_point LastCorpusReload = system_clock::now();
+
+  TmpMaxMutationLen =
+      Min(MaxMutationLen, Max(size_t(4), Corpus.MaxInputSize()));
+
   while (true) {
     auto Now = system_clock::now();
     if (duration_cast<seconds>(Now - LastCorpusReload).count() >=