[libFuzzer] Diff 9 - 2 - Properly use unsigned for workers, jobs and NumberOfCpuCores.

[mpividori]

Summary

According to amccarth's suggestions in: https://reviews.llvm.org/D27234?id=79657#inline-234115 , I modify NumberOfCpuCores() to return unsigned.

The number of cpus is used to define the number of workers in:

Flags.workers = std::min(NumberOfCpuCores() / 2, Flags.jobs);

So, I decided to update the worker and jobs flags to be defined as unsigned. These are not strictly necessary changes, I could have casted the result of the division to int, as :

Flags.workers = std::min(int(NumberOfCpuCores() / 2), Flags.jobs);

But I decided it would be better to avoid that and properly use unsigned for workers and jobs.

[kcc]

again: what problem are you trying to solve?

[mpividori]

@kcc std::thread::hardware_concurrency() returns unsigned, so NumberOfCpuCores() should return unsigned. Would you agree on this?
As NumberOfCpuCores() returns unsigned I thought it would be more appropriate to use unsigned for jobs and workers. If you don't want that changes, I can use an explicit cast as I mentioned above.
Just let me know what you want and I will include that changes.
Thanks

[kcc]

LGTM
(got it!)

lib/Fuzzer/FuzzerDriver.cpp

 static void PulseThread() {
   while (true) {
     SleepSeconds(600);
     std::lock_guard<std::mutex> Lock(Mu);
     Printf("pulse...\n");
   }
 }
 
-static void WorkerThread(const std::string &Cmd, std::atomic<int> *Counter,
-                        int NumJobs, std::atomic<bool> *HasErrors) {
+static void WorkerThread(const std::string &Cmd, std::atomic<unsigned> *Counter,
+                         unsigned NumJobs, std::atomic<bool> *HasErrors) {
   while (true) {
-    int C = (*Counter)++;
+    unsigned C = (*Counter)++;
     if (C >= NumJobs) break;
     std::string Log = "fuzz-" + std::to_string(C) + ".log";
     std::string ToRun = Cmd + " > " + Log + " 2>&1\n";
     if (Flags.verbosity)
       Printf("%s", ToRun.c_str());
     int ExitCode = ExecuteCommand(ToRun);
     if (ExitCode != 0)
       *HasErrors = true;
     std::lock_guard<std::mutex> Lock(Mu);
-    Printf("================== Job %d exited with exit code %d ============\n",
+    Printf("================== Job %u exited with exit code %d ============\n",
            C, ExitCode);
     fuzzer::CopyFileToErr(Log);
   }
 }
 
 static std::string CloneArgsWithoutX(const std::vector<std::string> &Args,
                                      const char *X1, const char *X2) {
   std::string Cmd;
   for (auto &S : Args) {
     if (FlagValue(S.c_str(), X1) || FlagValue(S.c_str(), X2))
       continue;
     Cmd += S + " ";
   }
   return Cmd;
 }
 
 static std::string CloneArgsWithoutX(const std::vector<std::string> &Args,
                                      const char *X) {
   return CloneArgsWithoutX(Args, X, X);
 }
 
 static int RunInMultipleProcesses(const std::vector<std::string> &Args,
-                                  int NumWorkers, int NumJobs) {
-  std::atomic<int> Counter(0);
+                                  unsigned NumWorkers, unsigned NumJobs) {
+  std::atomic<unsigned> Counter(0);
   std::atomic<bool> HasErrors(false);
   std::string Cmd = CloneArgsWithoutX(Args, "jobs", "workers");
   std::vector<std::thread> V;
   std::thread Pulse(PulseThread);
   Pulse.detach();
-  for (int i = 0; i < NumWorkers; i++)
+  for (unsigned i = 0; i < NumWorkers; i++)
     V.push_back(std::thread(WorkerThread, Cmd, &Counter, NumJobs, &HasErrors));
   for (auto &T : V)
     T.join();
   return HasErrors ? 1 : 0;
 }
 
 static void RssThread(Fuzzer *F, size_t RssLimitMb) {
   while (true) {
int FuzzerDriver(int *argc, char ***argv, UserCallback Callback) {
   if (Flags.close_fd_mask & 2)
     DupAndCloseStderr();
   if (Flags.close_fd_mask & 1)
     CloseStdout();
 
   if (Flags.jobs > 0 && Flags.workers == 0) {
     Flags.workers = std::min(NumberOfCpuCores() / 2, Flags.jobs);
     if (Flags.workers > 1)
-      Printf("Running %d workers\n", Flags.workers);
+      Printf("Running %u workers\n", Flags.workers);
   }
 
   if (Flags.workers > 0 && Flags.jobs > 0)
     return RunInMultipleProcesses(Args, Flags.workers, Flags.jobs);
 
   const size_t kMaxSaneLen = 1 << 20;
   const size_t kMinDefaultLen = 64;
   FuzzingOptions Options;

lib/Fuzzer/FuzzerFlags.def

 FUZZER_FLAG_INT(use_memcmp, 1,
                 "Use hints from intercepting memcmp, strcmp, etc")
 FUZZER_FLAG_INT(use_memmem, 1,
                 "Use hints from intercepting memmem, strstr, etc")
 FUZZER_FLAG_INT(use_value_profile, 0,
                 "Experimental. Use value profile to guide fuzzing.")
 FUZZER_FLAG_INT(use_cmp, 1, "Use CMP traces to guide mutations")
 FUZZER_FLAG_INT(shrink, 0, "Experimental. Try to shrink corpus elements.")
-FUZZER_FLAG_INT(jobs, 0, "Number of jobs to run. If jobs >= 1 we spawn"
+FUZZER_FLAG_UNSIGNED(jobs, 0, "Number of jobs to run. If jobs >= 1 we spawn"
                           " this number of jobs in separate worker processes"
                           " with stdout/stderr redirected to fuzz-JOB.log.")
-FUZZER_FLAG_INT(workers, 0,
+FUZZER_FLAG_UNSIGNED(workers, 0,
             "Number of simultaneous worker processes to run the jobs."
             " If zero, \"min(jobs,NumberOfCpuCores()/2)\" is used.")
 FUZZER_FLAG_INT(reload, 1,
                 "Reload the main corpus every <N> seconds to get new units"
                 " discovered by other processes. If 0, disabled")
 FUZZER_FLAG_INT(report_slow_units, 10,
     "Report slowest units if they run for more than this number of seconds.")
 FUZZER_FLAG_INT(only_ascii, 0,

lib/Fuzzer/FuzzerUtil.h

 bool IsASCII(const uint8_t *Data, size_t Size);
 
 std::string Base64(const Unit &U);
 
 void PrintPC(const char *SymbolizedFMT, const char *FallbackFMT, uintptr_t PC);
 
 std::string DescribePC(const char *SymbolizedFMT, uintptr_t PC);
 
-int NumberOfCpuCores();
+unsigned NumberOfCpuCores();
 
 bool ExecuteCommandAndReadOutput(const std::string &Command, std::string *Out);
 
 // Platform specific functions.
 void SetSignalHandler(const FuzzingOptions& Options);
 
 void SleepSeconds(int Seconds);
 

lib/Fuzzer/FuzzerUtil.cpp

 
 void PrintPC(const char *SymbolizedFMT, const char *FallbackFMT, uintptr_t PC) {
   if (EF->__sanitizer_symbolize_pc)
     Printf("%s", DescribePC(SymbolizedFMT, PC).c_str());
   else
     Printf(FallbackFMT, PC);
 }
 
-int NumberOfCpuCores() {
+unsigned NumberOfCpuCores() {
   unsigned N = std::thread::hardware_concurrency();
   if (!N) {
     Printf("WARNING: std::thread::hardware_concurrency not well defined for "
       "your platform. Assuming CPU count of 1.\n");
     N = 1;
   }
   return N;
 }