[NFC] Darwin llgs support from Week of Code

This code represents the Week of Code work I did on bringing up
lldb-server LLGS support for Darwin.  It does not include the
Xcode project changes needed, as we don't want to throw that switch
until more support is implemented (i.e. this change is inert, no
build systems use it yet.  I've verified on Ubuntu 16.04, macOS
Xcode and macOS cmake builds).

This change does some minimal refactoring of code that is shared
with the Linux LLGS portion, moving it from NativeProcessLinux into
NativeProcessProtocol.  That code is also used by NativeProcessDarwin.

Current state on Darwin:
* Process launching is implemented.  (Attach is not).
  Launching on devices has not yet been tested (FBS/BKS might
  need a bit of work).
* Inferior waitpid monitoring and communication of exit status
  via MainLoop callback is implemented.
* Memory read/write, breakpoints, thread register context, etc.
  are not yet implemented.  This impacts process stop/resume, as
  the initial launch suspended immediately starts the process
  up and running because it doesn't know it is supposed to remain
  stopped.
* I implemented the equivalent of MachThreadList as
  NativeThreadListDarwin, in anticipation that we might want to
  factor out common parts into NativeThreadList{Protocol} and share
  some code here.  After writing it, though, the fallout from merging
  Mach Task/Process into a single concept plus some other minor
  changes makes the whole NativeThreadListDarwin concept nothing more
  than dead weight.  I am likely going to get rid of this class and
  just manage it directly in NativeProcessDarwin, much like I did
  for NativeProcessLinux.
* There is a stub-out call for starting a STDIO thread.  That will
  go away and adopt the MainLoop pselect-based IOObject reading.

I am developing the fully-integrated changes in the following repo,
which contains the necessary Xcode bits and the glue that enables
lldb-debugserver on a macOS system:

  https://github.com/tfiala/lldb/tree/llgs-darwin

This change also breaks out a few of the lldb-server tests into
their own directory, and adds some $qHostInfo tests (not sure why
I didn't write those tests back when I initially implemented that
on the Linux side).

llvm-svn: 280604

1 files changed, 737 insertions, 0 deletions

diff --git a/lldb/source/Plugins/Process/Darwin/DarwinProcessLauncher.cpp b/lldb/source/Plugins/Process/Darwin/DarwinProcessLauncher.cpp
new file mode 100644
index 00000000000..91abe4f26e2
--- /dev/null
+++ b/lldb/source/Plugins/Process/Darwin/DarwinProcessLauncher.cpp
@@ -0,0 +1,737 @@
+//
+//  DarwinProcessLauncher.cpp
+//  lldb
+//
+//  Created by Todd Fiala on 8/30/16.
+//
+//
+
+#include "DarwinProcessLauncher.h"
+
+// C includes
+#include <spawn.h>
+#include <sys/ptrace.h>
+#include <sys/stat.h>
+#include <sys/sysctl.h>
+
+#ifndef _POSIX_SPAWN_DISABLE_ASLR
+#define _POSIX_SPAWN_DISABLE_ASLR       0x0100
+#endif
+
+// LLDB includes
+#include "lldb/lldb-enumerations.h"
+
+#include "lldb/Core/Error.h"
+#include "lldb/Core/Log.h"
+#include "lldb/Core/StreamString.h"
+#include "lldb/Target/ProcessLaunchInfo.h"
+#include "lldb/Utility/PseudoTerminal.h"
+
+#include "CFBundle.h"
+#include "CFString.h"
+
+using namespace lldb;
+using namespace lldb_private;
+using namespace lldb_private::process_darwin;
+using namespace lldb_private::darwin_process_launcher;
+
+namespace
+{
+    static LaunchFlavor g_launch_flavor = LaunchFlavor::Default;
+}
+
+namespace lldb_private
+{
+namespace darwin_process_launcher
+{
+
+static uint32_t
+GetCPUTypeForLocalProcess(::pid_t pid)
+{
+    int mib[CTL_MAXNAME]={0,};
+    size_t len = CTL_MAXNAME;
+    if (::sysctlnametomib("sysctl.proc_cputype", mib, &len))
+        return 0;
+
+    mib[len] = pid;
+    len++;
+
+    cpu_type_t cpu;
+    size_t cpu_len = sizeof(cpu);
+    if (::sysctl (mib, static_cast<u_int>(len), &cpu, &cpu_len, 0, 0))
+        cpu = 0;
+    return cpu;
+}
+
+static bool
+ResolveExecutablePath(const char *path, char *resolved_path,
+                      size_t resolved_path_size)
+{
+    if (path == NULL || path[0] == '\0')
+        return false;
+
+    char max_path[PATH_MAX];
+    std::string result;
+    CFString::GlobPath(path, result);
+
+    if (result.empty())
+        result = path;
+
+    struct stat path_stat;
+    if (::stat(path, &path_stat) == 0)
+    {
+        if ((path_stat.st_mode & S_IFMT) == S_IFDIR)
+        {
+            CFBundle bundle(path);
+            CFReleaser<CFURLRef> url(bundle.CopyExecutableURL ());
+            if (url.get())
+            {
+                if (::CFURLGetFileSystemRepresentation(url.get(), true,
+                                                       (UInt8*)resolved_path,
+                                                       resolved_path_size))
+                    return true;
+            }
+        }
+    }
+
+    if (realpath(path, max_path))
+    {
+        // Found the path relatively...
+        ::strncpy(resolved_path, max_path, resolved_path_size);
+        return strlen(resolved_path) + 1 < resolved_path_size;
+    }
+    else
+    {
+        // Not a relative path, check the PATH environment variable if the
+        const char *PATH = getenv("PATH");
+        if (PATH)
+        {
+            const char *curr_path_start = PATH;
+            const char *curr_path_end;
+            while (curr_path_start && *curr_path_start)
+            {
+                curr_path_end = strchr(curr_path_start, ':');
+                if (curr_path_end == NULL)
+                {
+                    result.assign(curr_path_start);
+                    curr_path_start = NULL;
+                }
+                else if (curr_path_end > curr_path_start)
+                {
+                    size_t len = curr_path_end - curr_path_start;
+                    result.assign(curr_path_start, len);
+                    curr_path_start += len + 1;
+                }
+                else
+                    break;
+
+                result += '/';
+                result += path;
+                struct stat s;
+                if (stat(result.c_str(), &s) == 0)
+                {
+                    ::strncpy(resolved_path, result.c_str(),
+                              resolved_path_size);
+                    return result.size() + 1 < resolved_path_size;
+                }
+            }
+        }
+    }
+    return false;
+}
+
+// TODO check if we have a general purpose fork and exec.  We may be
+// able to get rid of this entirely.
+static Error
+ForkChildForPTraceDebugging(const char *path,
+                            char const *argv[],
+                            char const *envp[],
+                            ::pid_t *pid,
+                            int *pty_fd)
+{
+    Error error;
+    if (!path || !argv || !envp || !pid || !pty_fd)
+    {
+        error.SetErrorString("invalid arguments");
+        return error;
+    }
+
+    // Use a fork that ties the child process's stdin/out/err to a pseudo
+    // terminal so we can read it in our MachProcess::STDIOThread
+    // as unbuffered io.
+    lldb_utility::PseudoTerminal pty;
+    char fork_error[256];
+    memset(fork_error, 0, sizeof(fork_error));
+    *pid = static_cast<::pid_t>(pty.Fork(fork_error, sizeof(fork_error)));
+    if (*pid < 0)
+    {
+        //--------------------------------------------------------------
+        // Error during fork.
+        //--------------------------------------------------------------
+        *pid = static_cast<::pid_t>(LLDB_INVALID_PROCESS_ID);
+        error.SetErrorStringWithFormat("%s(): fork failed: %s",
+                                       __FUNCTION__, fork_error);
+        return error;
+    }
+    else if (pid == 0)
+    {
+        //--------------------------------------------------------------
+        // Child process
+        //--------------------------------------------------------------
+
+        // Debug this process.
+        ::ptrace(PT_TRACE_ME, 0, 0, 0);
+
+        // Get BSD signals as mach exceptions.
+        ::ptrace(PT_SIGEXC, 0, 0, 0);
+
+        // If our parent is setgid, lets make sure we don't inherit those
+        // extra powers due to nepotism.
+        if (::setgid(getgid()) == 0)
+        {
+            // Let the child have its own process group. We need to execute
+            // this call in both the child and parent to avoid a race
+            // condition between the two processes.
+
+            // Set the child process group to match its pid.
+            ::setpgid(0, 0);
+
+            // Sleep a bit to before the exec call.
+            ::sleep(1);
+
+            // Turn this process into the given executable.
+            ::execv(path, (char * const *)argv);
+        }
+        // Exit with error code. Child process should have taken
+        // over in above exec call and if the exec fails it will
+        // exit the child process below.
+        ::exit(127);
+    }
+    else
+    {
+        //--------------------------------------------------------------
+        // Parent process
+        //--------------------------------------------------------------
+        // Let the child have its own process group. We need to execute
+        // this call in both the child and parent to avoid a race condition
+        // between the two processes.
+
+        // Set the child process group to match its pid
+        ::setpgid(*pid, *pid);
+        if (pty_fd)
+        {
+            // Release our master pty file descriptor so the pty class doesn't
+            // close it and so we can continue to use it in our STDIO thread
+            *pty_fd = pty.ReleaseMasterFileDescriptor();
+        }
+    }
+    return error;
+}
+
+static Error
+CreatePosixSpawnFileAction(const FileAction &action,
+                           posix_spawn_file_actions_t *file_actions)
+{
+    Error error;
+
+    // Log it.
+    Log *log(GetLogIfAllCategoriesSet(LIBLLDB_LOG_PROCESS));
+    if (log)
+    {
+        StreamString stream;
+        stream.PutCString("converting file action for posix_spawn(): ");
+        action.Dump(stream);
+        stream.Flush();
+        log->PutCString(stream.GetString().c_str());
+    }
+
+    // Validate args.
+    if (!file_actions)
+    {
+        error.SetErrorString("mandatory file_actions arg is null");
+        return error;
+    }
+
+    // Build the posix file action.
+    switch (action.GetAction())
+    {
+        case FileAction::eFileActionOpen:
+        {
+            const int error_code =
+                ::posix_spawn_file_actions_addopen(file_actions,
+                                                   action.GetFD(),
+                                                   action.GetPath(),
+                                                   action.GetActionArgument(),
+                                                   0);
+            if (error_code != 0)
+            {
+                error.SetError(error_code, eErrorTypePOSIX);
+                return error;
+            }
+            break;
+        }
+
+        case FileAction::eFileActionClose:
+        {
+            const int error_code =
+            ::posix_spawn_file_actions_addclose(file_actions,
+                                                action.GetFD());
+            if (error_code != 0)
+            {
+                error.SetError(error_code, eErrorTypePOSIX);
+                return error;
+            }
+            break;
+        }
+
+        case FileAction::eFileActionDuplicate:
+        {
+            const int error_code =
+            ::posix_spawn_file_actions_adddup2(file_actions,
+                                               action.GetFD(),
+                                               action.GetActionArgument());
+            if (error_code != 0)
+            {
+                error.SetError(error_code, eErrorTypePOSIX);
+                return error;
+            }
+            break;
+        }
+
+        case FileAction::eFileActionNone:
+        default:
+            if (log)
+                log->Printf("%s(): unsupported file action %u",
+                            __FUNCTION__, action.GetAction());
+            break;
+    }
+
+    return error;
+}
+
+static Error
+PosixSpawnChildForPTraceDebugging(const char *path,
+                                  ProcessLaunchInfo &launch_info,
+                                  ::pid_t *pid,
+                                  cpu_type_t *actual_cpu_type)
+{
+    Error error;
+    Log *log(GetLogIfAllCategoriesSet(LIBLLDB_LOG_PROCESS));
+
+    if (!pid)
+    {
+        error.SetErrorStringWithFormat("%s(): pid arg cannot be null",
+                                       __FUNCTION__);
+        return error;
+    }
+
+    posix_spawnattr_t attr;
+    short flags;
+    if (log)
+    {
+        StreamString stream;
+        stream.Printf("%s(path='%s',...)\n", __FUNCTION__, path);
+        launch_info.Dump(stream, nullptr);
+        stream.Flush();
+        log->PutCString(stream.GetString().c_str());
+    }
+
+    int error_code;
+    if ((error_code = ::posix_spawnattr_init(&attr)) != 0)
+    {
+        if (log)
+            log->Printf("::posix_spawnattr_init(&attr) failed");
+        error.SetError(error_code, eErrorTypePOSIX);
+        return error;
+    }
+
+    // Ensure we clean up the spawnattr structure however we exit this
+    // function.
+    std::unique_ptr<posix_spawnattr_t, int(*)(posix_spawnattr_t*)>
+        spawnattr_up(&attr, ::posix_spawnattr_destroy);
+
+
+    flags = POSIX_SPAWN_START_SUSPENDED | POSIX_SPAWN_SETSIGDEF |
+        POSIX_SPAWN_SETSIGMASK;
+    if (launch_info.GetFlags().Test(eLaunchFlagDisableASLR))
+        flags |= _POSIX_SPAWN_DISABLE_ASLR;
+
+    sigset_t no_signals;
+    sigset_t all_signals;
+    sigemptyset (&no_signals);
+    sigfillset (&all_signals);
+    ::posix_spawnattr_setsigmask(&attr, &no_signals);
+    ::posix_spawnattr_setsigdefault(&attr, &all_signals);
+
+    if ((error_code = ::posix_spawnattr_setflags(&attr, flags)) != 0)
+    {
+        if (log)
+            log->Printf("::posix_spawnattr_setflags(&attr, "
+                        "POSIX_SPAWN_START_SUSPENDED%s) failed: %s",
+                        flags & _POSIX_SPAWN_DISABLE_ASLR ?
+                        " | _POSIX_SPAWN_DISABLE_ASLR" : "",
+                        strerror(error_code));
+        error.SetError(error_code, eErrorTypePOSIX);
+        return error;
+    }
+
+#if !defined(__arm__)
+
+    // We don't need to do this for ARM, and we really shouldn't now that we
+    // have multiple CPU subtypes and no posix_spawnattr call that allows us
+    // to set which CPU subtype to launch...
+    cpu_type_t desired_cpu_type =
+        launch_info.GetArchitecture().GetMachOCPUType();
+    if (desired_cpu_type != LLDB_INVALID_CPUTYPE)
+    {
+        size_t ocount = 0;
+        error_code = ::posix_spawnattr_setbinpref_np(&attr, 1,
+                                                     &desired_cpu_type,
+                                                     &ocount);
+        if (error_code != 0)
+        {
+            if (log)
+                log->Printf("::posix_spawnattr_setbinpref_np(&attr, 1, "
+                            "cpu_type = 0x%8.8x, count => %llu): %s",
+                            desired_cpu_type, (uint64_t)ocount,
+                            strerror(error_code));
+            error.SetError(error_code, eErrorTypePOSIX);
+            return error;
+        }
+        if (ocount != 1)
+        {
+            error.SetErrorStringWithFormat("posix_spawnattr_setbinpref_np "
+                                           "did not set the expected number "
+                                           "of cpu_type entries: expected 1 "
+                                           "but was %zu", ocount);
+            return error;
+        }
+    }
+#endif
+
+    posix_spawn_file_actions_t file_actions;
+    if ((error_code = ::posix_spawn_file_actions_init(&file_actions)) != 0)
+    {
+        if (log)
+            log->Printf("::posix_spawn_file_actions_init(&file_actions) "
+                        "failed: %s",
+                        strerror(error_code));
+        error.SetError(error_code, eErrorTypePOSIX);
+        return error;
+    }
+
+    // Ensure we clean up file actions however we exit this.  When the
+    // file_actions_up below goes out of scope, we'll get our file action
+    // cleanup.
+    std::unique_ptr<posix_spawn_file_actions_t,
+                    int(*)(posix_spawn_file_actions_t*)>
+        file_actions_up(&file_actions, ::posix_spawn_file_actions_destroy);
+
+    // We assume the caller has setup the file actions appropriately.  We
+    // are not in the business of figuring out what we really need here.
+    // lldb-server will have already called FinalizeFileActions() as well
+    // to button these up properly.
+    const size_t num_actions = launch_info.GetNumFileActions();
+    for (size_t action_index = 0; action_index < num_actions; ++action_index)
+    {
+        const FileAction *const action =
+            launch_info.GetFileActionAtIndex(action_index);
+        if (!action)
+            continue;
+
+        error = CreatePosixSpawnFileAction(*action, &file_actions);
+        if (!error.Success())
+        {
+            if (log)
+                log->Printf("%s(): error converting FileAction to posix_spawn "
+                            "file action: %s", __FUNCTION__, error.AsCString());
+            return error;
+        }
+    }
+
+    // TODO: Verify if we can set the working directory back immediately
+    // after the posix_spawnp call without creating a race condition???
+    const char *const working_directory =
+        launch_info.GetWorkingDirectory().GetCString();
+    if (working_directory && working_directory[0])
+        ::chdir(working_directory);
+
+    auto argv = launch_info.GetArguments().GetArgumentVector();
+    auto envp = launch_info.GetEnvironmentEntries().GetArgumentVector();
+    error_code = ::posix_spawnp(pid, path, &file_actions, &attr,
+                                (char * const*)argv, (char * const*)envp);
+    if (error_code != 0)
+    {
+        if (log)
+            log->Printf("::posix_spawnp(pid => %p, path = '%s', file_actions "
+                        "= %p, attr = %p, argv = %p, envp = %p) failed: %s",
+                        pid, path, &file_actions, &attr, argv, envp,
+                        strerror(error_code));
+        error.SetError(error_code, eErrorTypePOSIX);
+        return error;
+    }
+
+    // Validate we got a pid.
+    if (pid == LLDB_INVALID_PROCESS_ID)
+    {
+        error.SetErrorString("posix_spawn() did not indicate a failure but it "
+                             "failed to return a pid, aborting.");
+        return error;
+    }
+
+    if (actual_cpu_type)
+    {
+        *actual_cpu_type = GetCPUTypeForLocalProcess(*pid);
+        if (log)
+            log->Printf("%s(): cpu type for launched process pid=%i: "
+                        "cpu_type=0x%8.8x", __FUNCTION__, *pid,
+                        *actual_cpu_type);
+    }
+
+    return error;
+}
+
+Error
+LaunchInferior(ProcessLaunchInfo &launch_info, int *pty_master_fd,
+               LaunchFlavor *launch_flavor)
+{
+    Error error;
+    Log *log(GetLogIfAllCategoriesSet(LIBLLDB_LOG_PROCESS));
+
+    if (!launch_flavor)
+    {
+        error.SetErrorString("mandatory launch_flavor field was null");
+        return error;
+    }
+
+    if (log)
+    {
+        StreamString stream;
+        stream.Printf("NativeProcessDarwin::%s(): launching with the "
+                      "following launch info:", __FUNCTION__);
+        launch_info.Dump(stream, nullptr);
+        stream.Flush();
+        log->PutCString(stream.GetString().c_str());
+    }
+
+    // Retrieve the binary name given to us.
+    char given_path[PATH_MAX];
+    given_path[0] = '\0';
+    launch_info.GetExecutableFile().GetPath(given_path, sizeof(given_path));
+
+    // Determine the manner in which we'll launch.
+    *launch_flavor = g_launch_flavor;
+    if (*launch_flavor == LaunchFlavor::Default)
+    {
+        // Our default launch method is posix spawn
+        *launch_flavor = LaunchFlavor::PosixSpawn;
+#if defined WITH_FBS
+        // Check if we have an app bundle, if so launch using BackBoard Services.
+        if (strstr(given_path, ".app"))
+        {
+            *launch_flavor = eLaunchFlavorFBS;
+        }
+#elif defined WITH_BKS
+        // Check if we have an app bundle, if so launch using BackBoard Services.
+        if (strstr(given_path, ".app"))
+        {
+            *launch_flavor = eLaunchFlavorBKS;
+        }
+#elif defined WITH_SPRINGBOARD
+        // Check if we have an app bundle, if so launch using SpringBoard.
+        if (strstr(given_path, ".app"))
+        {
+            *launch_flavor = eLaunchFlavorSpringBoard;
+        }
+#endif
+    }
+
+    // Attempt to resolve the binary name to an absolute path.
+    char resolved_path[PATH_MAX];
+    resolved_path[0] = '\0';
+
+    if (log)
+        log->Printf("%s(): attempting to resolve given binary path: \"%s\"",
+                    __FUNCTION__, given_path);
+
+    // If we fail to resolve the path to our executable, then just use what we
+    // were given and hope for the best
+    if (!ResolveExecutablePath(given_path, resolved_path,
+                               sizeof(resolved_path)) )
+    {
+        if (log)
+            log->Printf("%s(): failed to resolve binary path, using "
+                        "what was given verbatim and hoping for the best",
+                        __FUNCTION__);
+        ::strncpy(resolved_path, given_path,
+                  sizeof(resolved_path));
+    }
+    else
+    {
+        if (log)
+            log->Printf("%s(): resolved given binary path to: \"%s\"",
+                        __FUNCTION__, resolved_path);
+    }
+
+    char launch_err_str[PATH_MAX];
+    launch_err_str[0] = '\0';
+    
+    // TODO figure out how to handle QSetProcessEvent
+    // const char *process_event = ctx.GetProcessEvent();
+    
+    // Ensure the binary is there.
+    struct stat path_stat;
+    if (::stat(resolved_path, &path_stat) == -1)
+    {
+        error.SetErrorToErrno();
+        return error;
+    }
+    
+    // Fork a child process for debugging
+    // state_callback(eStateLaunching);
+
+    const auto argv = launch_info.GetArguments().GetConstArgumentVector();
+    const auto envp =
+        launch_info.GetEnvironmentEntries().GetConstArgumentVector();
+
+    switch (*launch_flavor)
+    {
+        case LaunchFlavor::ForkExec:
+        {
+            ::pid_t pid = LLDB_INVALID_PROCESS_ID;
+            error = ForkChildForPTraceDebugging(resolved_path, argv, envp,
+                                                &pid, pty_master_fd);
+            if (error.Success())
+            {
+                launch_info.SetProcessID(static_cast<lldb::pid_t>(pid));
+            }
+            else
+            {
+                // Reset any variables that might have been set during a failed
+                // launch attempt.
+                if (pty_master_fd)
+                    *pty_master_fd = -1;
+                
+                // We're done.
+                return error;
+            }
+        }
+            break;
+
+#ifdef WITH_FBS
+        case LaunchFlavor::FBS:
+        {
+            const char *app_ext = strstr(path, ".app");
+            if (app_ext && (app_ext[4] == '\0' || app_ext[4] == '/'))
+            {
+                std::string app_bundle_path(path, app_ext + strlen(".app"));
+                m_flags |= eMachProcessFlagsUsingFBS;
+                if (BoardServiceLaunchForDebug (app_bundle_path.c_str(), argv, envp, no_stdio, disable_aslr, event_data, launch_err) != 0)
+                    return m_pid; // A successful SBLaunchForDebug() returns and assigns a non-zero m_pid.
+                else
+                    break; // We tried a FBS launch, but didn't succeed lets get out
+            }
+        }
+            break;
+#endif
+            
+#ifdef WITH_BKS
+        case LaunchFlavor::BKS:
+        {
+            const char *app_ext = strstr(path, ".app");
+            if (app_ext && (app_ext[4] == '\0' || app_ext[4] == '/'))
+            {
+                std::string app_bundle_path(path, app_ext + strlen(".app"));
+                m_flags |= eMachProcessFlagsUsingBKS;
+                if (BoardServiceLaunchForDebug (app_bundle_path.c_str(), argv, envp, no_stdio, disable_aslr, event_data, launch_err) != 0)
+                    return m_pid; // A successful SBLaunchForDebug() returns and assigns a non-zero m_pid.
+                else
+                    break; // We tried a BKS launch, but didn't succeed lets get out
+            }
+        }
+            break;
+#endif
+            
+#ifdef WITH_SPRINGBOARD
+        case LaunchFlavor::SpringBoard:
+        {
+            //  .../whatever.app/whatever ?
+            //  Or .../com.apple.whatever.app/whatever -- be careful of ".app" in "com.apple.whatever" here
+            const char *app_ext = strstr (path, ".app/");
+            if (app_ext == NULL)
+            {
+                // .../whatever.app ?
+                int len = strlen (path);
+                if (len > 5)
+                {
+                    if (strcmp (path + len - 4, ".app") == 0)
+                    {
+                        app_ext = path + len - 4;
+                    }
+                }
+            }
+            if (app_ext)
+            {
+                std::string app_bundle_path(path, app_ext + strlen(".app"));
+                if (SBLaunchForDebug (app_bundle_path.c_str(), argv, envp, no_stdio, disable_aslr, launch_err) != 0)
+                    return m_pid; // A successful SBLaunchForDebug() returns and assigns a non-zero m_pid.
+                else
+                    break; // We tried a springboard launch, but didn't succeed lets get out
+            }
+        }
+            break;
+#endif
+            
+        case LaunchFlavor::PosixSpawn:
+        {
+            ::pid_t pid = LLDB_INVALID_PROCESS_ID;
+
+            // Retrieve paths for stdin/stdout/stderr.
+            cpu_type_t actual_cpu_type = 0;
+            error = PosixSpawnChildForPTraceDebugging(resolved_path,
+                                                      launch_info,
+                                                      &pid,
+                                                      &actual_cpu_type);
+            if (error.Success())
+            {
+                launch_info.SetProcessID(static_cast<lldb::pid_t>(pid));
+                if (pty_master_fd)
+                    *pty_master_fd = launch_info.GetPTY().
+                        ReleaseMasterFileDescriptor();
+            }
+            else
+            {
+                // Reset any variables that might have been set during a failed
+                // launch attempt.
+                if (pty_master_fd)
+                    *pty_master_fd = -1;
+
+                // We're done.
+                return error;
+            }
+            break;
+        }
+            
+        default:
+            // Invalid launch flavor.
+            error.SetErrorStringWithFormat("NativeProcessDarwin::%s(): unknown "
+                                           "launch flavor %d", __FUNCTION__,
+                                           (int)*launch_flavor);
+            return error;
+    }
+    
+    if (launch_info.GetProcessID() == LLDB_INVALID_PROCESS_ID)
+    {
+        // If we don't have a valid process ID and no one has set the error,
+        // then return a generic error.
+        if (error.Success())
+            error.SetErrorStringWithFormat("%s(): failed to launch, no reason "
+                                           "specified", __FUNCTION__);
+    }
+
+    // We're done with the launch side of the operation.
+    return error;
+}
+
+}} // namespaces
+