add support for the vRun GDB packet

## Purpose
Add support for GDB's `vRun` packet to ds2 debug sessions. Fixes issue
#150.

## Overview
* Override `SessionDelegate::onRunAttach` in `DebugSession`. Use
existing `spawnProcess` method to actually launch the process.
* Preserve environment variables set on `_spawner` by previous calls to
`onSetEnvironmentVariable`.
* Preserve previous executable and arguments set on `_spawner` from
previous calls to `onRunAttach`.
* Update `spawnProcess` to use memoized executable, arguments, and
environment when new ones are not provided.
* Fix missing `index++` in `Session::Handle_vRun.

## Problem Details
The following test cases rely on the `vRun` packet to work properly in
the debug session:
```
GdbRemoteLaunchTestCase.test_QEnvironmentHexEncoded_llgs
GdbRemoteLaunchTestCase.test_QEnvironment_llgs
GdbRemoteLaunchTestCase.test_launch_via_vRun_llgs
GdbRemoteLaunchTestCase.test_launch_via_vRun_no_args_llgs
```

## Validation
Combined with PR #143, this change gets all of the
`GdbRemoteLaunchTestCase` test cases passing against ds2 running on
Linux x86_64.

Author: andrurogerz

Headers/DebugServer2/GDBRemote/DebugSessionImpl.h

@@ -145,6 +145,9 @@ class DebugSessionImplBase : public DummySessionDelegateImpl {
 protected:
   ErrorCode onAttach(Session &session, ProcessId pid, AttachMode mode,
                      StopInfo &stop) override;
+  ErrorCode onRunAttach(Session &session, std::string const &filename,
+                        StringCollection const &arguments,
+                        StopInfo &stop) override;
 
 protected:
   ErrorCode onResume(Session &session,

Headers/DebugServer2/Host/POSIX/ProcessSpawner.h

@@ -112,6 +112,9 @@ class ProcessSpawner {
   inline ProcessId pid() const { return _pid; }
   inline int exitStatus() const { return _exitStatus; }
   inline int signalCode() const { return _signalCode; }
+  inline std::string const &executable() const { return _executablePath; }
+  inline StringCollection const &arguments() const { return _arguments; }
+  inline EnvironmentBlock const &environment() const { return _environment; }
 
 public:
   ErrorCode input(ByteVector const &buf);

Headers/DebugServer2/Host/Windows/ProcessSpawner.h

@@ -91,6 +91,9 @@ class ProcessSpawner {
   inline HANDLE threadHandle() const { return _threadHandle; }
   inline int exitStatus() const { return 0; }
   inline int signalCode() const { return 0; }
+  inline std::string const &executable() const { return _executablePath; }
+  inline StringCollection const &arguments() const { return _arguments; }
+  inline EnvironmentBlock const &environment() const { return _environment; }
 
 public:
   ErrorCode input(ByteVector const &buf) { return kErrorUnsupported; }

Sources/GDBRemote/DebugSessionImpl.cpp

@@ -845,6 +845,23 @@ ErrorCode DebugSessionImplBase::onAttach(Session &session, ProcessId pid,
   return queryStopInfo(session, pid, stop);
 }
 
+ErrorCode DebugSessionImplBase::onRunAttach(Session &session,
+                                            std::string const &filename,
+                                            StringCollection const &arguments,
+                                            StopInfo &stop) {
+  if (_process != nullptr)
+    return kErrorAlreadyExist;
+
+  if (!filename.empty())
+    _spawner.setExecutable(filename);
+
+  if (!arguments.empty())
+    _spawner.setArguments(arguments);
+
+  CHK(spawnProcess({}, {}));
+  return queryStopInfo(session, _spawner.pid(), stop);
+}
+
 ErrorCode
 DebugSessionImplBase::onResume(Session &session,
                                ThreadResumeAction::Collection const &actions,
@@ -1134,25 +1151,14 @@ ErrorCode DebugSessionImplBase::onRemoveBreakpoint(Session &session,
 
 ErrorCode DebugSessionImplBase::spawnProcess(StringCollection const &args,
                                              EnvironmentBlock const &env) {
-  bool displayArgs = args.size() > 1;
-  auto it = args.begin();
-  DS2LOG(Debug, "spawning process '%s'%s", (it++)->c_str(),
-         displayArgs ? " with args:" : "");
-  while (it != args.end()) {
-    DS2LOG(Debug, "  %s", (it++)->c_str());
-  }
+  if (!args.empty())
+    _spawner.setExecutable(args[0]);
 
-  _spawner.setExecutable(args[0]);
-  _spawner.setArguments(StringCollection(args.begin() + 1, args.end()));
-
-  if (!env.empty()) {
-    DS2LOG(Debug, "%swith environment:", displayArgs ? "and " : "");
-    for (auto const &val : env) {
-      DS2LOG(Debug, "  %s=%s", val.first.c_str(), val.second.c_str());
-    }
+  if (args.size() > 1)
+    _spawner.setArguments(StringCollection(args.begin() + 1, args.end()));
 
+  if (!env.empty())
     _spawner.setEnvironment(env);
-  }
 
   auto outputDelegate = [this](void *buf, size_t size) {
     appendOutput(static_cast<char *>(buf), size);
@@ -1162,6 +1168,18 @@ ErrorCode DebugSessionImplBase::spawnProcess(StringCollection const &args,
   _spawner.redirectOutputToDelegate(outputDelegate);
   _spawner.redirectErrorToDelegate(outputDelegate);
 
+  const bool displayArgs = !_spawner.arguments().empty();
+  DS2LOG(Debug, "spawning process '%s'%s", _spawner.executable().c_str(),
+         displayArgs ? " with args:" : "");
+  for (auto const &val : _spawner.arguments())
+    DS2LOG(Debug, "  %s", val.c_str());
+
+  if (!_spawner.environment().empty()) {
+    DS2LOG(Debug, "%swith environment:", displayArgs ? "and " : "");
+    for (auto const &val : _spawner.environment())
+      DS2LOG(Debug, "  %s=%s", val.first.c_str(), val.second.c_str());
+  }
+
   _process = ds2::Target::Process::Create(_spawner);
   if (_process == nullptr) {
     DS2LOG(Error, "cannot execute '%s'", args[0].c_str());

Sources/GDBRemote/Session.cpp

@@ -3233,7 +3233,7 @@ void Session::Handle_vRun(ProtocolInterpreter::Handler const &,
   size_t index = 0;
 
   ParseList(args, ';', [&](std::string const &arg) {
-    if (index == 0) {
+    if (index++ == 0) {
       filename = HexToString(arg);
     } else {
       arguments.push_back(HexToString(arg));