[libFuzzer] Encapsulate commands in a class

[aarongreen]

Summary

To be more portable (especially w.r.t. platforms without system()), commands should be managed programmatically rather than via string manipulation on the command line. This change introduces Fuzzer::Command, with methods to manage arguments and flags, set output options, and execute the command.

[kcc]

Nice, thank you!
Do I understand correctly that this is a no-functional-change-intended change?

Some comments below.
Matt, please make the next round of reviews (once my comments are addressed) and land it when done. (Assuming Aaron doesn't have commit access).

lib/fuzzer/FuzzerCommand.cpp

53 ↗

(On Diff #123086)

here and below:
LLVM coding style prefers to not use {} for single-statement if-body

lib/fuzzer/FuzzerCommand.h

22

consider haing all of this class in the header. There is not too much code in it and splitting it into t .h and .cpp bloats the code.

22

s/haing/having

23

Does this class deserve a gunit-style unit test in lib/fuzzer/tests/FuzzerUnittest.cpp ?

[morehouse]

lib/fuzzer/FuzzerCommand.cpp

38 ↗

(On Diff #123086)

LLVM style prefers first letter of parameters and locals to be capitalized. (here and below)

The one common exception I've seen is for one-letter loop indexes to be lowercase (though some people capitalize those too).

[aarongreen]

Holidays, illnesses, and more have kept me from closing on this; apologies.

Yes, kcc, this change is supposed maintain functional equivalence. It should only provide a more convenient way to build processes from commands without having to do a bunch of string parsing.

I've tried to go through and match the style guide. I'm still familiarizing myself with that one, please correct me if I'm not compliant. I also added the unit tests. Finally, I changed ExecuteCommand to take a Command rather than a string since the change was small enough that I don't think it warrants a separate review.

Thanks for the review!

[morehouse]

LGTM. Do you have commit access, or should I land this for you?

[aarongreen]

To the best of my knowledge, I do not have commit access, and believe I would know if I did . :)

lib/fuzzer/CMakeLists.txt

 set(LIBFUZZER_SOURCES
   FuzzerClangCounters.cpp
+  FuzzerCommand.cpp
   FuzzerCrossOver.cpp
   FuzzerDriver.cpp
   FuzzerExtFunctionsDlsym.cpp
   FuzzerExtFunctionsDlsymWin.cpp
   FuzzerExtFunctionsWeak.cpp
   FuzzerExtraCounters.cpp
   FuzzerIO.cpp
   FuzzerIOPosix.cpp

lib/fuzzer/FuzzerCommand.h

+//===- FuzzerCommand.h - Interface representing a process -------*- C++ -* ===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// FuzzerCommand represents a command to run in a subprocess.  It allows callers
+// to manage command line arguments and output and error streams.
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_FUZZER_COMMAND_H
+#define LLVM_FUZZER_COMMAND_H
+
+#include "FuzzerDefs.h"
+#include "FuzzerIO.h"
+
+#include <algorithm>
+#include <sstream>
+#include <string>
+#include <vector>
+
+namespace fuzzer {
+
+class Command final {
+public:
+  // This command line flag is used to indicate that the remaining command line
+  // is immutable, meaning this flag effectively marks the end of the mutable
+  // argument list.
+  static inline const char *const ignoreRemainingArgs() {
+    static const char *const kIgnoreRemaining = "-ignore_remaining_args=1";
+    return kIgnoreRemaining;
+  }
+
+  Command() : CombinedOutAndErr(false) {}
+
+  explicit Command(const Vector<std::string> &ArgsToAdd)
+      : Args(ArgsToAdd), CombinedOutAndErr(false) {}
+
+  explicit Command(const Command &Other)
+      : Args(Other.Args), CombinedOutAndErr(Other.CombinedOutAndErr),
+        OutputFile(Other.OutputFile) {}
+
+  Command &operator=(const Command &Other) {
+    Args = Other.Args;
+    CombinedOutAndErr = Other.CombinedOutAndErr;
+    OutputFile = Other.OutputFile;
+    return *this;
+  }
+
+  ~Command() {}
+
+  // Returns true if the given Arg is present in Args.  Only checks up to
+  // "-ignore_remaining_args=1".
+  bool hasArgument(const std::string &Arg) const {
+    auto i = endMutableArgs();
+    return std::find(Args.begin(), i, Arg) != i;
+  }
+
+  // Gets all of the current command line arguments, **including** those after
+  // "-ignore-remaining-args=1".
+  const Vector<std::string> &getArguments() const { return Args; }
+
+  // Adds the given argument before "-ignore_remaining_args=1", or at the end
+  // if that flag isn't present.
+  void addArgument(const std::string &Arg) {
+    Args.insert(endMutableArgs(), Arg);
+  }
+
+  // Adds all given arguments before "-ignore_remaining_args=1", or at the end
+  // if that flag isn't present.
+  void addArguments(const Vector<std::string> &ArgsToAdd) {
+    Args.insert(endMutableArgs(), ArgsToAdd.begin(), ArgsToAdd.end());
+  }
+
+  // Removes the given argument from the command argument list.  Ignores any
+  // occurrences after "-ignore_remaining_args=1", if present.
+  void removeArgument(const std::string &Arg) {
+    auto i = endMutableArgs();
+    Args.erase(std::remove(Args.begin(), i, Arg), i);
+  }
+
+  // Like hasArgument, but checks for "-[Flag]=...".
+  bool hasFlag(const std::string &Flag) {
+    std::string Arg("-" + Flag + "=");
+    auto IsMatch = [&](const std::string &Other) {
+      return Arg.compare(0, std::string::npos, Other, 0, Arg.length()) == 0;
+    };
+    return std::any_of(Args.begin(), endMutableArgs(), IsMatch);
+  }
+
+  // Returns the value of the first instance of a given flag, or an empty string
+  // if the flag isn't present.  Ignores any occurrences after
+  // "-ignore_remaining_args=1", if present.
+  std::string getFlagValue(const std::string &Flag) {
+    std::string Arg("-" + Flag + "=");
+    auto IsMatch = [&](const std::string &Other) {
+      return Arg.compare(0, std::string::npos, Other, 0, Arg.length()) == 0;
+    };
+    auto i = endMutableArgs();
+    auto j = std::find_if(Args.begin(), i, IsMatch);
+    std::string result;
+    if (j != i) {
+      result = j->substr(Arg.length());
+    }
+    return result;
+  }
+
+  // Like AddArgument, but adds "-[Flag]=[Value]".
+  void addFlag(const std::string &Flag, const std::string &Value) {
+    addArgument("-" + Flag + "=" + Value);
+  }
+
+  // Like RemoveArgument, but removes "-[Flag]=...".
+  void removeFlag(const std::string &Flag) {
+    std::string Arg("-" + Flag + "=");
+    auto IsMatch = [&](const std::string &Other) {
+      return Arg.compare(0, std::string::npos, Other, 0, Arg.length()) == 0;
+    };
+    auto i = endMutableArgs();
+    Args.erase(std::remove_if(Args.begin(), i, IsMatch), i);
+  }
+
+  // Returns whether the command's stdout is being written to an output file.
+  bool hasOutputFile() const { return !OutputFile.empty(); }
+
+  // Returns the currently set output file.
+  const std::string &getOutputFile() const { return OutputFile; }
+
+  // Configures the command to redirect its output to the name file.
+  void setOutputFile(const std::string &FileName) { OutputFile = FileName; }
+
+  // Returns whether the command's stderr is redirected to stdout.
+  bool isOutAndErrCombined() const { return CombinedOutAndErr; }
+
+  // Sets whether to redirect the command's stderr to its stdout.
+  void combineOutAndErr(bool combine = true) { CombinedOutAndErr = combine; }
+
+  // Returns a string representation of the command.  On many systems this will
+  // be the equivalent command line.
+  std::string toString() const {
+    std::stringstream SS;
+    for (auto arg : getArguments())
+      SS << arg << " ";
+    if (isOutAndErrCombined())
+      SS << "2>&1 ";
+    if (hasOutputFile())
+      SS << ">" << getOutputFile() << " ";
+    std::string result = SS.str();
+    if (!result.empty())
+      result = result.substr(0, result.length() - 1);
+    return result;
+  }
+
+private:
+  Command(Command &&Other) = delete;
+  Command &operator=(Command &&Other) = delete;
+
+  Vector<std::string>::iterator endMutableArgs() {
+    return std::find(Args.begin(), Args.end(), ignoreRemainingArgs());
+  }
+
+  Vector<std::string>::const_iterator endMutableArgs() const {
+    return std::find(Args.begin(), Args.end(), ignoreRemainingArgs());
+  }
+
+  // The command arguments.  Args[0] is the command name.
+  Vector<std::string> Args;
+
+  // True indicates stderr is redirected to stdout.
+  bool CombinedOutAndErr;
+
+  // If not empty, stdout is redirected to the named file.
+  std::string OutputFile;
+};
+
+} // namespace fuzzer
+
+#endif // LLVM_FUZZER_COMMAND_H

lib/fuzzer/FuzzerDriver.cpp

 //===- FuzzerDriver.cpp - FuzzerDriver function and flags -----------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 // FuzzerDriver and flag parsing.
 //===----------------------------------------------------------------------===//
 
+#include "FuzzerCommand.h"
 #include "FuzzerCorpus.h"
 #include "FuzzerIO.h"
 #include "FuzzerInterface.h"
 #include "FuzzerInternal.h"
 #include "FuzzerMutate.h"
 #include "FuzzerRandom.h"
 #include "FuzzerShmem.h"
 #include "FuzzerTracePC.h"

 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<unsigned> *Counter,
+static void WorkerThread(const Command &BaseCmd, std::atomic<unsigned> *Counter,
                          unsigned NumJobs, std::atomic<bool> *HasErrors) {
   while (true) {
     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);
+    Command Cmd(BaseCmd);
+    Cmd.setOutputFile(Log);
+    Cmd.combineOutAndErr();
+    if (Flags.verbosity) {
+      std::string CommandLine = Cmd.toString();
+      Printf("%s", CommandLine.c_str());
+    }
+    int ExitCode = ExecuteCommand(Cmd);
     if (ExitCode != 0)
       *HasErrors = true;
     std::lock_guard<std::mutex> Lock(Mu);
     Printf("================== Job %u exited with exit code %d ============\n",
            C, ExitCode);
     fuzzer::CopyFileToErr(Log);
   }
 }
 
 std::string CloneArgsWithoutX(const 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 int RunInMultipleProcesses(const Vector<std::string> &Args,
                                   unsigned NumWorkers, unsigned NumJobs) {
   std::atomic<unsigned> Counter(0);
   std::atomic<bool> HasErrors(false);
-  std::string Cmd = CloneArgsWithoutX(Args, "jobs", "workers");
+  Command Cmd(Args);
+  Cmd.removeFlag("jobs");
+  Cmd.removeFlag("workers");
   Vector<std::thread> V;
   std::thread Pulse(PulseThread);
   Pulse.detach();
   for (unsigned i = 0; i < NumWorkers; i++)
-    V.push_back(std::thread(WorkerThread, Cmd, &Counter, NumJobs, &HasErrors));
+    V.push_back(std::thread(WorkerThread, std::ref(Cmd), &Counter, NumJobs, &HasErrors));
   for (auto &T : V)
     T.join();
   return HasErrors ? 1 : 0;
 }
 
 static void RssThread(Fuzzer *F, size_t RssLimitMb) {
   while (true) {
     SleepSeconds(1);
int CleanseCrashInput(const Vector<std::string> &Args,
                        const FuzzingOptions &Options) {
   if (Inputs->size() != 1 || !Flags.exact_artifact_path) {
     Printf("ERROR: -cleanse_crash should be given one input file and"
           " -exact_artifact_path\n");
     exit(1);
   }
   std::string InputFilePath = Inputs->at(0);
   std::string OutputFilePath = Flags.exact_artifact_path;
-  std::string BaseCmd =
-      CloneArgsWithoutX(Args, "cleanse_crash", "cleanse_crash");
+  Command Cmd(Args);
+  Cmd.removeFlag("cleanse_crash");
 
-  auto InputPos = BaseCmd.find(" " + InputFilePath + " ");
-  assert(InputPos != std::string::npos);
-  BaseCmd.erase(InputPos, InputFilePath.size() + 1);
+  assert(Cmd.hasArgument(InputFilePath));
+  Cmd.removeArgument(InputFilePath);
 
   auto LogFilePath = DirPlusFile(
       TmpDir(), "libFuzzerTemp." + std::to_string(GetPid()) + ".txt");
   auto TmpFilePath = DirPlusFile(
       TmpDir(), "libFuzzerTemp." + std::to_string(GetPid()) + ".repro");
-  auto LogFileRedirect = " > " + LogFilePath + " 2>&1 ";
-
-  auto Cmd = BaseCmd + " " + TmpFilePath + LogFileRedirect;
+  Cmd.addArgument(TmpFilePath);
+  Cmd.setOutputFile(LogFilePath);
+  Cmd.combineOutAndErr();
 
   std::string CurrentFilePath = InputFilePath;
   auto U = FileToVector(CurrentFilePath);
   size_t Size = U.size();
 
   const Vector<uint8_t> ReplacementBytes = {' ', 0xff};
   for (int NumAttempts = 0; NumAttempts < 5; NumAttempts++) {
     bool Changed = false;

 
 int MinimizeCrashInput(const Vector<std::string> &Args,
                        const FuzzingOptions &Options) {
   if (Inputs->size() != 1) {
     Printf("ERROR: -minimize_crash should be given one input file\n");
     exit(1);
   }
   std::string InputFilePath = Inputs->at(0);
-  auto BaseCmd = SplitBefore(
-      "-ignore_remaining_args=1",
-      CloneArgsWithoutX(Args, "minimize_crash", "exact_artifact_path"));
-  auto InputPos = BaseCmd.first.find(" " + InputFilePath + " ");
-  assert(InputPos != std::string::npos);
-  BaseCmd.first.erase(InputPos, InputFilePath.size() + 1);
+  Command BaseCmd(Args);
+  BaseCmd.removeFlag("minimize_crash");
+  BaseCmd.removeFlag("exact_artifact_path");
+  assert(BaseCmd.hasArgument(InputFilePath));
+  BaseCmd.removeArgument(InputFilePath);
   if (Flags.runs <= 0 && Flags.max_total_time == 0) {
     Printf("INFO: you need to specify -runs=N or "
            "-max_total_time=N with -minimize_crash=1\n"
            "INFO: defaulting to -max_total_time=600\n");
-    BaseCmd.first += " -max_total_time=600";
+    BaseCmd.addFlag("max_total_time", "600");
   }
 
   auto LogFilePath = DirPlusFile(
       TmpDir(), "libFuzzerTemp." + std::to_string(GetPid()) + ".txt");
-  auto LogFileRedirect = " > " + LogFilePath + " 2>&1 ";
+  BaseCmd.setOutputFile(LogFilePath);
+  BaseCmd.combineOutAndErr();
 
   std::string CurrentFilePath = InputFilePath;
   while (true) {
     Unit U = FileToVector(CurrentFilePath);
     Printf("CRASH_MIN: minimizing crash input: '%s' (%zd bytes)\n",
            CurrentFilePath.c_str(), U.size());
 
-    auto Cmd = BaseCmd.first + " " + CurrentFilePath + LogFileRedirect + " " +
-               BaseCmd.second;
+    Command Cmd(BaseCmd);
+    Cmd.addArgument(CurrentFilePath);
 
-    Printf("CRASH_MIN: executing: %s\n", Cmd.c_str());
+    std::string CommandLine = Cmd.toString();
+    Printf("CRASH_MIN: executing: %s\n", CommandLine.c_str());
     int ExitCode = ExecuteCommand(Cmd);
     if (ExitCode == 0) {
       Printf("ERROR: the input %s did not crash\n", CurrentFilePath.c_str());
       exit(1);
     }
     Printf("CRASH_MIN: '%s' (%zd bytes) caused a crash. Will try to minimize "
            "it further\n",
            CurrentFilePath.c_str(), U.size());
     auto DedupToken1 = GetDedupTokenFromFile(LogFilePath);
     if (!DedupToken1.empty())
       Printf("CRASH_MIN: DedupToken1: %s\n", DedupToken1.c_str());
 
     std::string ArtifactPath =
         Flags.exact_artifact_path
             ? Flags.exact_artifact_path
             : Options.ArtifactPrefix + "minimized-from-" + Hash(U);
-    Cmd += " -minimize_crash_internal_step=1 -exact_artifact_path=" +
-        ArtifactPath;
-    Printf("CRASH_MIN: executing: %s\n", Cmd.c_str());
+    Cmd.addFlag("minimize_crash_internal_step", "1");
+    Cmd.addFlag("exact_artifact_path", ArtifactPath);
+    CommandLine = Cmd.toString();
+    Printf("CRASH_MIN: executing: %s\n", CommandLine.c_str());
     ExitCode = ExecuteCommand(Cmd);
     CopyFileToErr(LogFilePath);
     if (ExitCode == 0) {
       if (Flags.exact_artifact_path) {
         CurrentFilePath = Flags.exact_artifact_path;
         WriteToFile(U, CurrentFilePath);
       }
       Printf("CRASH_MIN: failed to minimize beyond %s (%d bytes), exiting\n",

lib/fuzzer/FuzzerMerge.cpp

 //===- FuzzerMerge.cpp - merging corpora ----------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 // Merging corpora.
 //===----------------------------------------------------------------------===//
 
+#include "FuzzerCommand.h"
 #include "FuzzerMerge.h"
 #include "FuzzerIO.h"
 #include "FuzzerInternal.h"
 #include "FuzzerTracePC.h"
 #include "FuzzerUtil.h"
 
 #include <fstream>
 #include <iterator>
for (size_t i = M.FirstNotProcessedFile; i < M.Files.size(); i++) {
     auto U = FileToVector(M.Files[i].Name);
     if (U.size() > MaxInputLen) {
       U.resize(MaxInputLen);
       U.shrink_to_fit();
     }
     std::ostringstream StartedLine;
     // Write the pre-run marker.
     OF << "STARTED " << std::dec << i << " " << U.size() << "\n";
-    OF.flush();  // Flush is important since ExecuteCommand may crash.
+    OF.flush();  // Flush is important since Command::Execute may crash.
     // Run.
     TPC.ResetMaps();
     ExecuteCallback(U.data(), U.size());
     // Collect coverage. We are iterating over the files in this order:
     // * First, files in the initial corpus ordered by size, smallest first.
     // * Then, all other files, smallest first.
     // So it makes no sense to record all features for all files, instead we
     // only record features that were not seen before.
if (!NumAttempts) {
     Printf("MERGE-OUTER: %zd files, %zd in the initial corpus\n",
            AllFiles.size(), NumFilesInFirstCorpus);
     WriteNewControlFile(CFPath, AllFiles, NumFilesInFirstCorpus);
     NumAttempts = AllFiles.size();
   }
 
   // Execute the inner process until it passes.
   // Every inner process should execute at least one input.
-  auto BaseCmd = SplitBefore("-ignore_remaining_args=1",
-                             CloneArgsWithoutX(Args, "merge"));
+  Command BaseCmd(Args);
+  BaseCmd.removeFlag("merge");
   bool Success = false;
   for (size_t Attempt = 1; Attempt <= NumAttempts; Attempt++) {
     MaybeExitGracefully();
     Printf("MERGE-OUTER: attempt %zd\n", Attempt);
-    auto ExitCode =
-        ExecuteCommand(BaseCmd.first + " -merge_control_file=" + CFPath +
-                       " -merge_inner=1 " + BaseCmd.second);
+    Command Cmd(BaseCmd);
+    Cmd.addFlag("merge_control_file", CFPath);
+    Cmd.addFlag("merge_inner", "1");
+    auto ExitCode = ExecuteCommand(Cmd);
     if (!ExitCode) {
       Printf("MERGE-OUTER: succesfull in %zd attempt(s)\n", Attempt);
       Success = true;
       break;
     }
   }
   if (!Success) {
     Printf("MERGE-OUTER: zero succesfull attempts, exiting\n");

lib/fuzzer/FuzzerUtil.h

 //===- FuzzerUtil.h - Internal header for the Fuzzer Utils ------*- C++ -* ===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 // Util functions.
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_FUZZER_UTIL_H
 #define LLVM_FUZZER_UTIL_H
 
 #include "FuzzerDefs.h"
+#include "FuzzerCommand.h"
 
 namespace fuzzer {
 
 void PrintHexArray(const Unit &U, const char *PrintAfter = "");
 
 void PrintHexArray(const uint8_t *Data, size_t Size,
                    const char *PrintAfter = "");
 

 void SetSignalHandler(const FuzzingOptions& Options);
 
 void SleepSeconds(int Seconds);
 
 unsigned long GetPid();
 
 size_t GetPeakRSSMb();
 
-int ExecuteCommand(const std::string &Command);
+int ExecuteCommand(const Command &Cmd);
 
 FILE *OpenProcessPipe(const char *Command, const char *Mode);
 
 const void *SearchMemory(const void *haystack, size_t haystacklen,
                          const void *needle, size_t needlelen);
 
 std::string CloneArgsWithoutX(const Vector<std::string> &Args,
                               const char *X1, const char *X2);

lib/fuzzer/FuzzerUtilDarwin.cpp

 //===- FuzzerUtilDarwin.cpp - Misc utils ----------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 // Misc utils for Darwin.
 //===----------------------------------------------------------------------===//
 #include "FuzzerDefs.h"
 #if LIBFUZZER_APPLE
-
+#include "FuzzerCommand.h"
 #include "FuzzerIO.h"
 #include <mutex>
 #include <signal.h>
 #include <spawn.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/wait.h>
 

 static sigset_t OldBlockedSignalsSet;
 
 // This is a reimplementation of Libc's `system()`. On Darwin the Libc
 // implementation contains a mutex which prevents it from being used
 // concurrently. This implementation **can** be used concurrently. It sets the
 // signal handlers when the first thread enters and restores them when the last
 // thread finishes execution of the function and ensures this is not racey by
 // using a mutex.
-int ExecuteCommand(const std::string &Command) {
+int ExecuteCommand(const Command &Cmd) {
+  std::string CmdLine = Cmd.toString();
   posix_spawnattr_t SpawnAttributes;
   if (posix_spawnattr_init(&SpawnAttributes))
     return -1;
   // Block and ignore signals of the current process when the first thread
   // enters.
   {
     std::lock_guard<std::mutex> Lock(SignalMutex);
     if (ActiveThreadCount == 0) {
int ExecuteCommand(const Command &Cmd) {
   (void)posix_spawnattr_setsigdefault(&SpawnAttributes, &DefaultSigSet);
   // Make sure the child process doesn't block SIGCHLD
   (void)posix_spawnattr_setsigmask(&SpawnAttributes, &OldBlockedSignalsSet);
   short SpawnFlags = POSIX_SPAWN_SETSIGDEF | POSIX_SPAWN_SETSIGMASK;
   (void)posix_spawnattr_setflags(&SpawnAttributes, SpawnFlags);
 
   pid_t Pid;
   char **Environ = environ; // Read from global
-  const char *CommandCStr = Command.c_str();
+  const char *CommandCStr = CmdLine.c_str();
   char *const Argv[] = {
     strdup("sh"),
     strdup("-c"),
     strdup(CommandCStr),
     NULL
   };
   int ErrorCode = 0, ProcessStatus = 0;
   // FIXME: We probably shouldn't hardcode the shell path.

lib/fuzzer/FuzzerUtilLinux.cpp

 //===- FuzzerUtilLinux.cpp - Misc utils for Linux. ------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 // Misc utils for Linux.
 //===----------------------------------------------------------------------===//
 #include "FuzzerDefs.h"
 #if LIBFUZZER_LINUX || LIBFUZZER_NETBSD
+#include "FuzzerCommand.h"
 
 #include <stdlib.h>
 
 namespace fuzzer {
 
-int ExecuteCommand(const std::string &Command) {
-  return system(Command.c_str());
+int ExecuteCommand(const Command &Cmd) {
+  std::string CmdLine = Cmd.toString();
+  return system(CmdLine.c_str());
 }
 
 } // namespace fuzzer
 
 #endif // LIBFUZZER_LINUX || LIBFUZZER_NETBSD

lib/fuzzer/FuzzerUtilWindows.cpp

 //===- FuzzerUtilWindows.cpp - Misc utils for Windows. --------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 // Misc utils implementation for Windows.
 //===----------------------------------------------------------------------===//
 #include "FuzzerDefs.h"
 #if LIBFUZZER_WINDOWS
+#include "FuzzerCommand.h"
 #include "FuzzerIO.h"
 #include "FuzzerInternal.h"
 #include <cassert>
 #include <chrono>
 #include <cstring>
 #include <errno.h>
 #include <iomanip>
 #include <signal.h>
if (!GetProcessMemoryInfo(GetCurrentProcess(), &info, sizeof(info)))
     return 0;
   return info.PeakWorkingSetSize >> 20;
 }
 
 FILE *OpenProcessPipe(const char *Command, const char *Mode) {
   return _popen(Command, Mode);
 }
 
-int ExecuteCommand(const std::string &Command) {
-  return system(Command.c_str());
+int ExecuteCommand(const Command &Cmd) {
+  std::string CmdLine = Cmd.toString();
+  return system(CmdLine.c_str());
 }
 
 const void *SearchMemory(const void *Data, size_t DataLen, const void *Patt,
                          size_t PattLen) {
   // TODO: make this implementation more efficient.
   const char *Cdata = (const char *)Data;
   const char *Cpatt = (const char *)Patt;
 

lib/fuzzer/tests/FuzzerUnittest.cpp

TEST(Fuzzer, ForEachNonZeroByte) {
 
   Res.clear();
   ForEachNonZeroByte(Ar + 9, Ar + N - 9, 109, CB);
   Expected = {          {109, 2}, {118, 3}, {120, 4},
               {135, 5}, {137, 6}, {146, 7}};
   EXPECT_EQ(Res, Expected);
 }
 
+// FuzzerCommand unit tests. The arguments in the two helper methods below must
+// match.
+static void makeCommandArgs(Vector<std::string> *ArgsToAdd) {
+  assert(ArgsToAdd);
+  ArgsToAdd->clear();
+  ArgsToAdd->push_back("foo");
+  ArgsToAdd->push_back("-bar=baz");
+  ArgsToAdd->push_back("qux");
+  ArgsToAdd->push_back(Command::ignoreRemainingArgs());
+  ArgsToAdd->push_back("quux");
+  ArgsToAdd->push_back("-grault=garply");
+}
+
+static std::string makeCmdLine(const char *separator, const char *suffix) {
+  std::string CmdLine("foo -bar=baz qux ");
+  if (strlen(separator) != 0) {
+    CmdLine += separator;
+    CmdLine += " ";
+  }
+  CmdLine += Command::ignoreRemainingArgs();
+  CmdLine += " quux -grault=garply";
+  if (strlen(suffix) != 0) {
+    CmdLine += " ";
+    CmdLine += suffix;
+  }
+  return CmdLine;
+}
+
+TEST(FuzzerCommand, Create) {
+  std::string CmdLine;
+
+  // Default constructor
+  Command DefaultCmd;
+
+  CmdLine = DefaultCmd.toString();
+  EXPECT_EQ(CmdLine, "");
+
+  // Explicit constructor
+  Vector<std::string> ArgsToAdd;
+  makeCommandArgs(&ArgsToAdd);
+  Command InitializedCmd(ArgsToAdd);
+
+  CmdLine = InitializedCmd.toString();
+  EXPECT_EQ(CmdLine, makeCmdLine("", ""));
+
+  // Compare each argument
+  auto InitializedArgs = InitializedCmd.getArguments();
+  auto i = ArgsToAdd.begin();
+  auto j = InitializedArgs.begin();
+  while (i != ArgsToAdd.end() && j != InitializedArgs.end()) {
+    EXPECT_EQ(*i++, *j++);
+  }
+  EXPECT_EQ(i, ArgsToAdd.end());
+  EXPECT_EQ(j, InitializedArgs.end());
+
+  // Copy constructor
+  Command CopiedCmd(InitializedCmd);
+
+  CmdLine = CopiedCmd.toString();
+  EXPECT_EQ(CmdLine, makeCmdLine("", ""));
+
+  // Assignment operator
+  Command AssignedCmd;
+  AssignedCmd = CopiedCmd;
+
+  CmdLine = AssignedCmd.toString();
+  EXPECT_EQ(CmdLine, makeCmdLine("", ""));
+}
+
+TEST(FuzzerCommand, ModifyArguments) {
+  Vector<std::string> ArgsToAdd;
+  makeCommandArgs(&ArgsToAdd);
+  Command Cmd;
+  std::string CmdLine;
+
+  Cmd.addArguments(ArgsToAdd);
+  CmdLine = Cmd.toString();
+  EXPECT_EQ(CmdLine, makeCmdLine("", ""));
+
+  Cmd.addArgument("waldo");
+  EXPECT_TRUE(Cmd.hasArgument("waldo"));
+
+  CmdLine = Cmd.toString();
+  EXPECT_EQ(CmdLine, makeCmdLine("waldo", ""));
+
+  Cmd.removeArgument("waldo");
+  EXPECT_FALSE(Cmd.hasArgument("waldo"));
+
+  CmdLine = Cmd.toString();
+  EXPECT_EQ(CmdLine, makeCmdLine("", ""));
+}
+
+TEST(FuzzerCommand, ModifyFlags) {
+  Vector<std::string> ArgsToAdd;
+  makeCommandArgs(&ArgsToAdd);
+  Command Cmd(ArgsToAdd);
+  std::string Value, CmdLine;
+  ASSERT_FALSE(Cmd.hasFlag("fred"));
+
+  Value = Cmd.getFlagValue("fred");
+  EXPECT_EQ(Value, "");
+
+  CmdLine = Cmd.toString();
+  EXPECT_EQ(CmdLine, makeCmdLine("", ""));
+
+  Cmd.addFlag("fred", "plugh");
+  EXPECT_TRUE(Cmd.hasFlag("fred"));
+
+  Value = Cmd.getFlagValue("fred");
+  EXPECT_EQ(Value, "plugh");
+
+  CmdLine = Cmd.toString();
+  EXPECT_EQ(CmdLine, makeCmdLine("-fred=plugh", ""));
+
+  Cmd.removeFlag("fred");
+  EXPECT_FALSE(Cmd.hasFlag("fred"));
+
+  Value = Cmd.getFlagValue("fred");
+  EXPECT_EQ(Value, "");
+
+  CmdLine = Cmd.toString();
+  EXPECT_EQ(CmdLine, makeCmdLine("", ""));
+}
+
+TEST(FuzzerCommand, SetOutput) {
+  Vector<std::string> ArgsToAdd;
+  makeCommandArgs(&ArgsToAdd);
+  Command Cmd(ArgsToAdd);
+  std::string CmdLine;
+  ASSERT_FALSE(Cmd.hasOutputFile());
+  ASSERT_FALSE(Cmd.isOutAndErrCombined());
+
+  Cmd.combineOutAndErr(true);
+  EXPECT_TRUE(Cmd.isOutAndErrCombined());
+
+  CmdLine = Cmd.toString();
+  EXPECT_EQ(CmdLine, makeCmdLine("", "2>&1"));
+
+  Cmd.combineOutAndErr(false);
+  EXPECT_FALSE(Cmd.isOutAndErrCombined());
+
+  Cmd.setOutputFile("xyzzy");
+  EXPECT_TRUE(Cmd.hasOutputFile());
+
+  CmdLine = Cmd.toString();
+  EXPECT_EQ(CmdLine, makeCmdLine("", ">xyzzy"));
+
+  Cmd.setOutputFile("thud");
+  EXPECT_TRUE(Cmd.hasOutputFile());
+
+  CmdLine = Cmd.toString();
+  EXPECT_EQ(CmdLine, makeCmdLine("", ">thud"));
+
+  Cmd.combineOutAndErr();
+  EXPECT_TRUE(Cmd.isOutAndErrCombined());
+
+  CmdLine = Cmd.toString();
+  EXPECT_EQ(CmdLine, makeCmdLine("", "2>&1 >thud"));
+}
+
 int main(int argc, char **argv) {
   testing::InitGoogleTest(&argc, argv);
   return RUN_ALL_TESTS();
 }