[PATCH] Add a Fuzzer library

[Yury Gribov]

================
Comment at: lib/Fuzzer/FuzzerFlags.h:16
@@ +15,3 @@
+FUZZER_FLAG(int, iterations, -1,
+            "Number of iterations of the fuzzer (-1 for infinite runs).")
+FUZZER_FLAG(int, max_len, 64, "Maximal length of the test input.")
----------------
I wonder if people will mostly be interested to run fuzzer until coverage keeps increasing.

================
Comment at: lib/Fuzzer/FuzzerIO.cpp:19
@@ +18,3 @@
+  DIR *D = opendir(Dir.c_str());
+  if (!D) return V;
+  while (auto E = readdir(D)) {
----------------
Perhaps allow files as well?

================
Comment at: lib/Fuzzer/FuzzerLoop.cpp:118
@@ +117,3 @@
+    if (NewCoverage) {
+      Corpus.push_back(*U);
+      NewUnits++;
----------------
Just curious, have you considered making this a heap to explore the most covering units first?

================
Comment at: lib/Fuzzer/FuzzerMain.cpp:70
@@ +69,3 @@
+  if (Param[0] == '-' && strstr(Param + 1, Name) == Param + 1 &&
+      Param[Len + 1] == '=')
+      return &Param[Len + 2];
----------------
You know the len so perhaps just do memcmp for both checks?

================
Comment at: lib/Fuzzer/FuzzerMain.cpp:85
@@ +84,3 @@
+        std::cerr << "Flag: " << Name << " " << Val << "\n";
+      return true;;
+    }
----------------
Extra ;

================
Comment at: lib/Fuzzer/FuzzerMain.cpp:118
@@ +117,3 @@
+  if (!inputs.empty())
+    Options.OutputCorpus = inputs[0];
+  Fuzzer F(Options);
----------------
Perhaps add an option for this?

================
Comment at: lib/Fuzzer/FuzzerMutate.cpp:34
@@ +33,3 @@
+
+void Mutate(Unit *U, size_t MaxLen) {
+  assert(MaxLen > 0);
----------------
dblaikie wrote:
> pass U by reference?
Ditto for other places (CrossOver, MutateAndTestOne, etc.)?

================
Comment at: lib/Fuzzer/FuzzerUtil.cpp:56
@@ +55,3 @@
+  memset(&sigact, 0, sizeof(sigact));
+  sigact.sa_sigaction = AlarmHandler;
+  Res = sigaction(SIGALRM, &sigact, 0);
----------------
Don't you need SA_SIGINFO and perhaps SA_ONSTACK here?

http://reviews.llvm.org/D7184

EMAIL PREFERENCES
  http://reviews.llvm.org/settings/panel/emailpreferences/