Host/common/Host.cpp

//===-- Host.cpp ------------------------------------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "lldb/lldb-python.h"

// C includes
#include <errno.h>
#include <limits.h>
#include <sys/types.h>
#ifdef _WIN32
#include "lldb/Host/windows/windows.h"
#include <winsock2.h>
#include <WS2tcpip.h>
#else
#include <dlfcn.h>
#include <grp.h>
#include <netdb.h>
#include <pwd.h>
#include <sys/stat.h>
#endif

#if !defined (__GNU__) && !defined (_WIN32)
// Does not exist under GNU/HURD or Windows
#include <sys/sysctl.h>
#endif

#if defined (__APPLE__)
#include <mach/mach_port.h>
#include <mach/mach_init.h>
#include <mach-o/dyld.h>
#include <AvailabilityMacros.h>
#endif

#if defined (__linux__) || defined (__FreeBSD__) || defined (__FreeBSD_kernel__)
#include <spawn.h>
#include <sys/wait.h>
#include <sys/syscall.h>
#endif

#if defined (__FreeBSD__)
#include <pthread_np.h>
#endif

#include "lldb/Host/Host.h"
#include "lldb/Core/ArchSpec.h"
#include "lldb/Core/ConstString.h"
#include "lldb/Core/Debugger.h"
#include "lldb/Core/Error.h"
#include "lldb/Core/Log.h"
#include "lldb/Core/Module.h"
#include "lldb/Core/StreamString.h"
#include "lldb/Core/ThreadSafeSTLMap.h"
#include "lldb/Host/Config.h"
#include "lldb/Host/Endian.h"
#include "lldb/Host/FileSpec.h"
#include "lldb/Host/Mutex.h"
#include "lldb/Target/Process.h"
#include "lldb/Target/TargetList.h"
#include "lldb/Utility/CleanUp.h"

#include "llvm/ADT/SmallString.h"
#include "llvm/Support/Host.h"
#include "llvm/Support/raw_ostream.h"


using namespace lldb;
using namespace lldb_private;


#if !defined (__APPLE__) && !defined (_WIN32)
struct MonitorInfo
{
    lldb::pid_t pid;                            // The process ID to monitor
    Host::MonitorChildProcessCallback callback; // The callback function to call when "pid" exits or signals
    void *callback_baton;                       // The callback baton for the callback function
    bool monitor_signals;                       // If true, call the callback when "pid" gets signaled.
};

static thread_result_t
MonitorChildProcessThreadFunction (void *arg);

lldb::thread_t
Host::StartMonitoringChildProcess
(
    Host::MonitorChildProcessCallback callback,
    void *callback_baton,
    lldb::pid_t pid,
    bool monitor_signals
)
{
    lldb::thread_t thread = LLDB_INVALID_HOST_THREAD;
    MonitorInfo * info_ptr = new MonitorInfo();

    info_ptr->pid = pid;
    info_ptr->callback = callback;
    info_ptr->callback_baton = callback_baton;
    info_ptr->monitor_signals = monitor_signals;

    char thread_name[256];
    ::snprintf (thread_name, sizeof(thread_name), "<lldb.host.wait4(pid=%" PRIu64 ")>", pid);
    thread = ThreadCreate (thread_name,
                           MonitorChildProcessThreadFunction,
                           info_ptr,
                           NULL);

    return thread;
}

//------------------------------------------------------------------
// Scoped class that will disable thread canceling when it is
// constructed, and exception safely restore the previous value it
// when it goes out of scope.
//------------------------------------------------------------------
class ScopedPThreadCancelDisabler
{
public:
    ScopedPThreadCancelDisabler()
    {
        // Disable the ability for this thread to be cancelled
        int err = ::pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, &m_old_state);
        if (err != 0)
            m_old_state = -1;

    }

    ~ScopedPThreadCancelDisabler()
    {
        // Restore the ability for this thread to be cancelled to what it
        // previously was.
        if (m_old_state != -1)
            ::pthread_setcancelstate (m_old_state, 0);
    }
private:
    int m_old_state;    // Save the old cancelability state.
};

static thread_result_t
MonitorChildProcessThreadFunction (void *arg)
{
    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_PROCESS));
    const char *function = __FUNCTION__;
    if (log)
        log->Printf ("%s (arg = %p) thread starting...", function, arg);

    MonitorInfo *info = (MonitorInfo *)arg;

    const Host::MonitorChildProcessCallback callback = info->callback;
    void * const callback_baton = info->callback_baton;
    const bool monitor_signals = info->monitor_signals;

    assert (info->pid <= UINT32_MAX);
    const ::pid_t pid = monitor_signals ? -1 * info->pid : info->pid;

    delete info;

    int status = -1;
#if defined (__FreeBSD__) || defined (__FreeBSD_kernel__)
    #define __WALL 0
#endif
    const int options = __WALL;

    while (1)
    {
        log = lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_PROCESS);
        if (log)
            log->Printf("%s ::wait_pid (pid = %" PRIi32 ", &status, options = %i)...", function, pid, options);

        // Wait for all child processes
        ::pthread_testcancel ();
        // Get signals from all children with same process group of pid
        const ::pid_t wait_pid = ::waitpid (pid, &status, options);
        ::pthread_testcancel ();

        if (wait_pid == -1)
        {
            if (errno == EINTR)
                continue;
            else
            {
                if (log)
                    log->Printf ("%s (arg = %p) thread exiting because waitpid failed (%s)...", __FUNCTION__, arg, strerror(errno));
                break;
            }
        }
        else if (wait_pid > 0)
        {
            bool exited = false;
            int signal = 0;
            int exit_status = 0;
            const char *status_cstr = NULL;
            if (WIFSTOPPED(status))
            {
                signal = WSTOPSIG(status);
                status_cstr = "STOPPED";
            }
            else if (WIFEXITED(status))
            {
                exit_status = WEXITSTATUS(status);
                status_cstr = "EXITED";
                exited = true;
            }
            else if (WIFSIGNALED(status))
            {
                signal = WTERMSIG(status);
                status_cstr = "SIGNALED";
                if (wait_pid == abs(pid)) {
                    exited = true;
                    exit_status = -1;
                }
            }
            else
            {
                status_cstr = "(\?\?\?)";
            }

            // Scope for pthread_cancel_disabler
            {
                ScopedPThreadCancelDisabler pthread_cancel_disabler;

                log = lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_PROCESS);
                if (log)
                    log->Printf ("%s ::waitpid (pid = %" PRIi32 ", &status, options = %i) => pid = %" PRIi32 ", status = 0x%8.8x (%s), signal = %i, exit_state = %i",
                                 function,
                                 wait_pid,
                                 options,
                                 pid,
                                 status,
                                 status_cstr,
                                 signal,
                                 exit_status);

                if (exited || (signal != 0 && monitor_signals))
                {
                    bool callback_return = false;
                    if (callback)
                        callback_return = callback (callback_baton, wait_pid, exited, signal, exit_status);

                    // If our process exited, then this thread should exit
                    if (exited && wait_pid == abs(pid))
                    {
                        if (log)
                            log->Printf ("%s (arg = %p) thread exiting because pid received exit signal...", __FUNCTION__, arg);
                        break;
                    }
                    // If the callback returns true, it means this process should
                    // exit
                    if (callback_return)
                    {
                        if (log)
                            log->Printf ("%s (arg = %p) thread exiting because callback returned true...", __FUNCTION__, arg);
                        break;
                    }
                }
            }
        }
    }

    log = lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_PROCESS);
    if (log)
        log->Printf ("%s (arg = %p) thread exiting...", __FUNCTION__, arg);

    return NULL;
}

#endif // #if !defined (__APPLE__) && !defined (_WIN32)

#if !defined (__APPLE__)

void
Host::SystemLog (SystemLogType type, const char *format, va_list args)
{
    vfprintf (stderr, format, args);
}

#endif

void
Host::SystemLog (SystemLogType type, const char *format, ...)
{
    va_list args;
    va_start (args, format);
    SystemLog (type, format, args);
    va_end (args);
}

const ArchSpec &
Host::GetArchitecture (SystemDefaultArchitecture arch_kind)
{
    static bool g_supports_32 = false;
    static bool g_supports_64 = false;
    static ArchSpec g_host_arch_32;
    static ArchSpec g_host_arch_64;

#if defined (__APPLE__)

    // Apple is different in that it can support both 32 and 64 bit executables
    // in the same operating system running concurrently. Here we detect the
    // correct host architectures for both 32 and 64 bit including if 64 bit
    // executables are supported on the system.

    if (g_supports_32 == false && g_supports_64 == false)
    {
        // All apple systems support 32 bit execution.
        g_supports_32 = true;
        uint32_t cputype, cpusubtype;
        uint32_t is_64_bit_capable = false;
        size_t len = sizeof(cputype);
        ArchSpec host_arch;
        // These will tell us about the kernel architecture, which even on a 64
        // bit machine can be 32 bit...
        if  (::sysctlbyname("hw.cputype", &cputype, &len, NULL, 0) == 0)
        {
            len = sizeof (cpusubtype);
            if (::sysctlbyname("hw.cpusubtype", &cpusubtype, &len, NULL, 0) != 0)
                cpusubtype = CPU_TYPE_ANY;

            len = sizeof (is_64_bit_capable);
            if  (::sysctlbyname("hw.cpu64bit_capable", &is_64_bit_capable, &len, NULL, 0) == 0)
            {
                if (is_64_bit_capable)
                    g_supports_64 = true;
            }

            if (is_64_bit_capable)
            {
#if defined (__i386__) || defined (__x86_64__)
                if (cpusubtype == CPU_SUBTYPE_486)
                    cpusubtype = CPU_SUBTYPE_I386_ALL;
#endif
                if (cputype & CPU_ARCH_ABI64)
                {
                    // We have a 64 bit kernel on a 64 bit system
                    g_host_arch_32.SetArchitecture (eArchTypeMachO, ~(CPU_ARCH_MASK) & cputype, cpusubtype);
                    g_host_arch_64.SetArchitecture (eArchTypeMachO, cputype, cpusubtype);
                }
                else
                {
                    // We have a 32 bit kernel on a 64 bit system
                    g_host_arch_32.SetArchitecture (eArchTypeMachO, cputype, cpusubtype);
                    cputype |= CPU_ARCH_ABI64;
                    g_host_arch_64.SetArchitecture (eArchTypeMachO, cputype, cpusubtype);
                }
            }
            else
            {
                g_host_arch_32.SetArchitecture (eArchTypeMachO, cputype, cpusubtype);
                g_host_arch_64.Clear();
            }
        }
    }

#else // #if defined (__APPLE__)

    if (g_supports_32 == false && g_supports_64 == false)
    {
        llvm::Triple triple(llvm::sys::getDefaultTargetTriple());

        g_host_arch_32.Clear();
        g_host_arch_64.Clear();

        // If the OS is Linux, "unknown" in the vendor slot isn't what we want
        // for the default triple.  It's probably an artifact of config.guess.
        if (triple.getOS() == llvm::Triple::Linux && triple.getVendor() == llvm::Triple::UnknownVendor)
            triple.setVendorName("");

        switch (triple.getArch())
        {
        default:
            g_host_arch_32.SetTriple(triple);
            g_supports_32 = true;
            break;

        case llvm::Triple::x86_64:
            g_host_arch_64.SetTriple(triple);
            g_supports_64 = true;
            g_host_arch_32.SetTriple(triple.get32BitArchVariant());
            g_supports_32 = true;
            break;

        case llvm::Triple::sparcv9:
        case llvm::Triple::ppc64:
            g_host_arch_64.SetTriple(triple);
            g_supports_64 = true;
            break;
        }

        g_supports_32 = g_host_arch_32.IsValid();
        g_supports_64 = g_host_arch_64.IsValid();
    }

#endif // #else for #if defined (__APPLE__)

    if (arch_kind == eSystemDefaultArchitecture32)
        return g_host_arch_32;
    else if (arch_kind == eSystemDefaultArchitecture64)
        return g_host_arch_64;

    if (g_supports_64)
        return g_host_arch_64;

    return g_host_arch_32;
}

const ConstString &
Host::GetVendorString()
{
    static ConstString g_vendor;
    if (!g_vendor)
    {
        const ArchSpec &host_arch = GetArchitecture (eSystemDefaultArchitecture);
        const llvm::StringRef &str_ref = host_arch.GetTriple().getVendorName();
        g_vendor.SetCStringWithLength(str_ref.data(), str_ref.size());
    }
    return g_vendor;
}

const ConstString &
Host::GetOSString()
{
    static ConstString g_os_string;
    if (!g_os_string)
    {
        const ArchSpec &host_arch = GetArchitecture (eSystemDefaultArchitecture);
        const llvm::StringRef &str_ref = host_arch.GetTriple().getOSName();
        g_os_string.SetCStringWithLength(str_ref.data(), str_ref.size());
    }
    return g_os_string;
}

const ConstString &
Host::GetTargetTriple()
{
    static ConstString g_host_triple;
    if (!(g_host_triple))
    {
        const ArchSpec &host_arch = GetArchitecture (eSystemDefaultArchitecture);
        g_host_triple.SetCString(host_arch.GetTriple().getTriple().c_str());
    }
    return g_host_triple;
}

lldb::pid_t
Host::GetCurrentProcessID()
{
    return ::getpid();
}

#ifndef _WIN32

lldb::tid_t
Host::GetCurrentThreadID()
{
#if defined (__APPLE__)
    // Calling "mach_port_deallocate()" bumps the reference count on the thread
    // port, so we need to deallocate it. mach_task_self() doesn't bump the ref
    // count.
    thread_port_t thread_self = mach_thread_self();
    mach_port_deallocate(mach_task_self(), thread_self);
    return thread_self;
#elif defined(__FreeBSD__)
    return lldb::tid_t(pthread_getthreadid_np());
#elif defined(__linux__)
    return lldb::tid_t(syscall(SYS_gettid));
#else
    return lldb::tid_t(pthread_self());
#endif
}

lldb::thread_t
Host::GetCurrentThread ()
{
    return lldb::thread_t(pthread_self());
}

const char *
Host::GetSignalAsCString (int signo)
{
    switch (signo)
    {
    case SIGHUP:    return "SIGHUP";    // 1    hangup
    case SIGINT:    return "SIGINT";    // 2    interrupt
    case SIGQUIT:   return "SIGQUIT";   // 3    quit
    case SIGILL:    return "SIGILL";    // 4    illegal instruction (not reset when caught)
    case SIGTRAP:   return "SIGTRAP";   // 5    trace trap (not reset when caught)
    case SIGABRT:   return "SIGABRT";   // 6    abort()
#if  (defined(_POSIX_C_SOURCE) && !defined(_DARWIN_C_SOURCE))
    case SIGPOLL:   return "SIGPOLL";   // 7    pollable event ([XSR] generated, not supported)
#endif
#if  !defined(_POSIX_C_SOURCE)
    case SIGEMT:    return "SIGEMT";    // 7    EMT instruction
#endif
    case SIGFPE:    return "SIGFPE";    // 8    floating point exception
    case SIGKILL:   return "SIGKILL";   // 9    kill (cannot be caught or ignored)
    case SIGBUS:    return "SIGBUS";    // 10    bus error
    case SIGSEGV:   return "SIGSEGV";   // 11    segmentation violation
    case SIGSYS:    return "SIGSYS";    // 12    bad argument to system call
    case SIGPIPE:   return "SIGPIPE";   // 13    write on a pipe with no one to read it
    case SIGALRM:   return "SIGALRM";   // 14    alarm clock
    case SIGTERM:   return "SIGTERM";   // 15    software termination signal from kill
    case SIGURG:    return "SIGURG";    // 16    urgent condition on IO channel
    case SIGSTOP:   return "SIGSTOP";   // 17    sendable stop signal not from tty
    case SIGTSTP:   return "SIGTSTP";   // 18    stop signal from tty
    case SIGCONT:   return "SIGCONT";   // 19    continue a stopped process
    case SIGCHLD:   return "SIGCHLD";   // 20    to parent on child stop or exit
    case SIGTTIN:   return "SIGTTIN";   // 21    to readers pgrp upon background tty read
    case SIGTTOU:   return "SIGTTOU";   // 22    like TTIN for output if (tp->t_local&LTOSTOP)
#if  !defined(_POSIX_C_SOURCE)
    case SIGIO:     return "SIGIO";     // 23    input/output possible signal
#endif
    case SIGXCPU:   return "SIGXCPU";   // 24    exceeded CPU time limit
    case SIGXFSZ:   return "SIGXFSZ";   // 25    exceeded file size limit
    case SIGVTALRM: return "SIGVTALRM"; // 26    virtual time alarm
    case SIGPROF:   return "SIGPROF";   // 27    profiling time alarm
#if  !defined(_POSIX_C_SOURCE)
    case SIGWINCH:  return "SIGWINCH";  // 28    window size changes
    case SIGINFO:   return "SIGINFO";   // 29    information request
#endif
    case SIGUSR1:   return "SIGUSR1";   // 30    user defined signal 1
    case SIGUSR2:   return "SIGUSR2";   // 31    user defined signal 2
    default:
        break;
    }
    return NULL;
}

#endif

void
Host::WillTerminate ()
{
}

#if !defined (__APPLE__) && !defined (__FreeBSD__) && !defined (__FreeBSD_kernel__) && !defined (__linux__) // see macosx/Host.mm

void
Host::ThreadCreated (const char *thread_name)
{
}

void
Host::Backtrace (Stream &strm, uint32_t max_frames)
{
    // TODO: Is there a way to backtrace the current process on other systems?
}

size_t
Host::GetEnvironment (StringList &env)
{
    // TODO: Is there a way to the host environment for this process on other systems?
    return 0;
}

#endif // #if !defined (__APPLE__) && !defined (__FreeBSD__) && !defined (__FreeBSD_kernel__) && !defined (__linux__)

struct HostThreadCreateInfo
{
    std::string thread_name;
    thread_func_t thread_fptr;
    thread_arg_t thread_arg;

    HostThreadCreateInfo (const char *name, thread_func_t fptr, thread_arg_t arg) :
        thread_name (name ? name : ""),
        thread_fptr (fptr),
        thread_arg (arg)
    {
    }
};

static thread_result_t
#ifdef _WIN32
__stdcall
#endif
ThreadCreateTrampoline (thread_arg_t arg)
{
    HostThreadCreateInfo *info = (HostThreadCreateInfo *)arg;
    Host::ThreadCreated (info->thread_name.c_str());
    thread_func_t thread_fptr = info->thread_fptr;
    thread_arg_t thread_arg = info->thread_arg;

    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_THREAD));
    if (log)
        log->Printf("thread created");

    delete info;
    return thread_fptr (thread_arg);
}

lldb::thread_t
Host::ThreadCreate
(
    const char *thread_name,
    thread_func_t thread_fptr,
    thread_arg_t thread_arg,
    Error *error
)
{
    lldb::thread_t thread = LLDB_INVALID_HOST_THREAD;

    // Host::ThreadCreateTrampoline will delete this pointer for us.
    HostThreadCreateInfo *info_ptr = new HostThreadCreateInfo (thread_name, thread_fptr, thread_arg);

#ifdef _WIN32
    thread = ::_beginthreadex(0, 0, ThreadCreateTrampoline, info_ptr, 0, NULL);
    int err = thread <= 0 ? GetLastError() : 0;
#else
    int err = ::pthread_create (&thread, NULL, ThreadCreateTrampoline, info_ptr);
#endif
    if (err == 0)
    {
        if (error)
            error->Clear();
        return thread;
    }

    if (error)
        error->SetError (err, eErrorTypePOSIX);

    return LLDB_INVALID_HOST_THREAD;
}

#ifndef _WIN32

bool
Host::ThreadCancel (lldb::thread_t thread, Error *error)
{
    int err = ::pthread_cancel (thread);
    if (error)
        error->SetError(err, eErrorTypePOSIX);
    return err == 0;
}

bool
Host::ThreadDetach (lldb::thread_t thread, Error *error)
{
    int err = ::pthread_detach (thread);
    if (error)
        error->SetError(err, eErrorTypePOSIX);
    return err == 0;
}

bool
Host::ThreadJoin (lldb::thread_t thread, thread_result_t *thread_result_ptr, Error *error)
{
    int err = ::pthread_join (thread, thread_result_ptr);
    if (error)
        error->SetError(err, eErrorTypePOSIX);
    return err == 0;
}

lldb::thread_key_t
Host::ThreadLocalStorageCreate(ThreadLocalStorageCleanupCallback callback)
{
    pthread_key_t key;
    ::pthread_key_create (&key, callback);
    return key;
}

void*
Host::ThreadLocalStorageGet(lldb::thread_key_t key)
{
    return ::pthread_getspecific (key);
}

void
Host::ThreadLocalStorageSet(lldb::thread_key_t key, void *value)
{
   ::pthread_setspecific (key, value);
}

bool
Host::SetThreadName (lldb::pid_t pid, lldb::tid_t tid, const char *name)
{
#if defined(__APPLE__) && MAC_OS_X_VERSION_MAX_ALLOWED > MAC_OS_X_VERSION_10_5
    lldb::pid_t curr_pid = Host::GetCurrentProcessID();
    lldb::tid_t curr_tid = Host::GetCurrentThreadID();
    if (pid == LLDB_INVALID_PROCESS_ID)
        pid = curr_pid;

    if (tid == LLDB_INVALID_THREAD_ID)
        tid = curr_tid;

    // Set the pthread name if possible
    if (pid == curr_pid && tid == curr_tid)
    {
        if (::pthread_setname_np (name) == 0)
            return true;
    }
    return false;
#elif defined (__FreeBSD__)
    lldb::pid_t curr_pid = Host::GetCurrentProcessID();
    lldb::tid_t curr_tid = Host::GetCurrentThreadID();
    if (pid == LLDB_INVALID_PROCESS_ID)
        pid = curr_pid;

    if (tid == LLDB_INVALID_THREAD_ID)
        tid = curr_tid;

    // Set the pthread name if possible
    if (pid == curr_pid && tid == curr_tid)
    {
        ::pthread_set_name_np (::pthread_self(), name);
        return true;
    }
    return false;
#elif defined (__linux__) || defined (__GLIBC__)
    void *fn = dlsym (RTLD_DEFAULT, "pthread_setname_np");
    if (fn)
    {
        lldb::pid_t curr_pid = Host::GetCurrentProcessID();
        lldb::tid_t curr_tid = Host::GetCurrentThreadID();
        if (pid == LLDB_INVALID_PROCESS_ID)
            pid = curr_pid;

        if (tid == LLDB_INVALID_THREAD_ID)
            tid = curr_tid;

        if (pid == curr_pid && tid == curr_tid)
        {
            int (*pthread_setname_np_func)(pthread_t thread, const char *name);
            *reinterpret_cast<void **> (&pthread_setname_np_func) = fn;

            if (pthread_setname_np_func (::pthread_self(), name) == 0)
                return true;
        }
    }
    return false;
#else
    return false;
#endif
}

bool
Host::SetShortThreadName (lldb::pid_t pid, lldb::tid_t tid,
                          const char *thread_name, size_t len)
{
    char *namebuf = (char *)::malloc (len + 1);

    // Thread names are coming in like '<lldb.comm.debugger.edit>' and
    // '<lldb.comm.debugger.editline>'.  So just chopping the end of the string
    // off leads to a lot of similar named threads.  Go through the thread name
    // and search for the last dot and use that.
    const char *lastdot = ::strrchr (thread_name, '.');

    if (lastdot && lastdot != thread_name)
        thread_name = lastdot + 1;
    ::strncpy (namebuf, thread_name, len);
    namebuf[len] = 0;

    int namebuflen = strlen(namebuf);
    if (namebuflen > 0)
    {
        if (namebuf[namebuflen - 1] == '(' || namebuf[namebuflen - 1] == '>')
        {
            // Trim off trailing '(' and '>' characters for a bit more cleanup.
            namebuflen--;
            namebuf[namebuflen] = 0;
        }
        return Host::SetThreadName (pid, tid, namebuf);
    }

    ::free(namebuf);
    return false;
}

#endif

FileSpec
Host::GetProgramFileSpec ()
{
    static FileSpec g_program_filespec;
    if (!g_program_filespec)
    {
#if defined (__APPLE__)
        char program_fullpath[PATH_MAX];
        // If DST is NULL, then return the number of bytes needed.
        uint32_t len = sizeof(program_fullpath);
        int err = _NSGetExecutablePath (program_fullpath, &len);
        if (err == 0)
            g_program_filespec.SetFile (program_fullpath, false);
        else if (err == -1)
        {
            char *large_program_fullpath = (char *)::malloc (len + 1);

            err = _NSGetExecutablePath (large_program_fullpath, &len);
            if (err == 0)
                g_program_filespec.SetFile (large_program_fullpath, false);

            ::free (large_program_fullpath);
        }
#elif defined (__linux__)
        char exe_path[PATH_MAX];
        ssize_t len = readlink("/proc/self/exe", exe_path, sizeof(exe_path) - 1);
        if (len > 0) {
            exe_path[len] = 0;
            g_program_filespec.SetFile(exe_path, false);
        }
#elif defined (__FreeBSD__) || defined (__FreeBSD_kernel__)
        int exe_path_mib[4] = { CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, getpid() };
        size_t exe_path_size;
        if (sysctl(exe_path_mib, 4, NULL, &exe_path_size, NULL, 0) == 0)
        {
            char *exe_path = new char[exe_path_size];
            if (sysctl(exe_path_mib, 4, exe_path, &exe_path_size, NULL, 0) == 0)
                g_program_filespec.SetFile(exe_path, false);
            delete[] exe_path;
        }
#endif
    }
    return g_program_filespec;
}

#if !defined (__APPLE__) // see Host.mm

bool
Host::GetBundleDirectory (const FileSpec &file, FileSpec &bundle)
{
    bundle.Clear();
    return false;
}

bool
Host::ResolveExecutableInBundle (FileSpec &file)
{
    return false;
}
#endif

#ifndef _WIN32

// Opaque info that tracks a dynamic library that was loaded
struct DynamicLibraryInfo
{
    DynamicLibraryInfo (const FileSpec &fs, int o, void *h) :
        file_spec (fs),
        open_options (o),
        handle (h)
    {
    }

    const FileSpec file_spec;
    uint32_t open_options;
    void * handle;
};

void *
Host::DynamicLibraryOpen (const FileSpec &file_spec, uint32_t options, Error &error)
{
    char path[PATH_MAX];
    if (file_spec.GetPath(path, sizeof(path)))
    {
        int mode = 0;

        if (options & eDynamicLibraryOpenOptionLazy)
            mode |= RTLD_LAZY;
        else
            mode |= RTLD_NOW;


        if (options & eDynamicLibraryOpenOptionLocal)
            mode |= RTLD_LOCAL;
        else
            mode |= RTLD_GLOBAL;

#ifdef LLDB_CONFIG_DLOPEN_RTLD_FIRST_SUPPORTED
        if (options & eDynamicLibraryOpenOptionLimitGetSymbol)
            mode |= RTLD_FIRST;
#endif

        void * opaque = ::dlopen (path, mode);

        if (opaque)
        {
            error.Clear();
            return new DynamicLibraryInfo (file_spec, options, opaque);
        }
        else
        {
            error.SetErrorString(::dlerror());
        }
    }
    else
    {
        error.SetErrorString("failed to extract path");
    }
    return NULL;
}

Error
Host::DynamicLibraryClose (void *opaque)
{
    Error error;
    if (opaque == NULL)
    {
        error.SetErrorString ("invalid dynamic library handle");
    }
    else
    {
        DynamicLibraryInfo *dylib_info = (DynamicLibraryInfo *) opaque;
        if (::dlclose (dylib_info->handle) != 0)
        {
            error.SetErrorString(::dlerror());
        }

        dylib_info->open_options = 0;
        dylib_info->handle = 0;
        delete dylib_info;
    }
    return error;
}

void *
Host::DynamicLibraryGetSymbol (void *opaque, const char *symbol_name, Error &error)
{
    if (opaque == NULL)
    {
        error.SetErrorString ("invalid dynamic library handle");
    }
    else
    {
        DynamicLibraryInfo *dylib_info = (DynamicLibraryInfo *) opaque;

        void *symbol_addr = ::dlsym (dylib_info->handle, symbol_name);
        if (symbol_addr)
        {
#ifndef LLDB_CONFIG_DLOPEN_RTLD_FIRST_SUPPORTED
            // This host doesn't support limiting searches to this shared library
            // so we need to verify that the match came from this shared library
            // if it was requested in the Host::DynamicLibraryOpen() function.
            if (dylib_info->open_options & eDynamicLibraryOpenOptionLimitGetSymbol)
            {
                FileSpec match_dylib_spec (Host::GetModuleFileSpecForHostAddress (symbol_addr));
                if (match_dylib_spec != dylib_info->file_spec)
                {
                    char dylib_path[PATH_MAX];
                    if (dylib_info->file_spec.GetPath (dylib_path, sizeof(dylib_path)))
                        error.SetErrorStringWithFormat ("symbol not found in \"%s\"", dylib_path);
                    else
                        error.SetErrorString ("symbol not found");
                    return NULL;
                }
            }
#endif
            error.Clear();
            return symbol_addr;
        }
        else
        {
            error.SetErrorString(::dlerror());
        }
    }
    return NULL;
}

FileSpec
Host::GetModuleFileSpecForHostAddress (const void *host_addr)
{
    FileSpec module_filespec;
    Dl_info info;
    if (::dladdr (host_addr, &info))
    {
        if (info.dli_fname)
            module_filespec.SetFile(info.dli_fname, true);
    }
    return module_filespec;
}

#endif

bool
Host::GetLLDBPath (PathType path_type, FileSpec &file_spec)
{
    // To get paths related to LLDB we get the path to the executable that
    // contains this function. On MacOSX this will be "LLDB.framework/.../LLDB",
    // on linux this is assumed to be the "lldb" main executable. If LLDB on
    // linux is actually in a shared library (liblldb.so) then this function will
    // need to be modified to "do the right thing".
    Log *log = lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_HOST);

    switch (path_type)
    {
    case ePathTypeLLDBShlibDir:
        {
            static ConstString g_lldb_so_dir;
            if (!g_lldb_so_dir)
            {
                FileSpec lldb_file_spec (Host::GetModuleFileSpecForHostAddress ((void *)Host::GetLLDBPath));
                g_lldb_so_dir = lldb_file_spec.GetDirectory();
                if (log)
                    log->Printf("Host::GetLLDBPath(ePathTypeLLDBShlibDir) => '%s'", g_lldb_so_dir.GetCString());
            }
            file_spec.GetDirectory() = g_lldb_so_dir;
            return (bool)file_spec.GetDirectory();
        }
        break;

    case ePathTypeSupportExecutableDir:
        {
            static ConstString g_lldb_support_exe_dir;
            if (!g_lldb_support_exe_dir)
            {
                FileSpec lldb_file_spec;
                if (GetLLDBPath (ePathTypeLLDBShlibDir, lldb_file_spec))
                {
                    char raw_path[PATH_MAX];
                    char resolved_path[PATH_MAX];
                    lldb_file_spec.GetPath(raw_path, sizeof(raw_path));

#if defined (__APPLE__)
                    char *framework_pos = ::strstr (raw_path, "LLDB.framework");
                    if (framework_pos)
                    {
                        framework_pos += strlen("LLDB.framework");
#if defined (__arm__)
                        // Shallow bundle
                        *framework_pos = '\0';
#else
                        // Normal bundle
                        ::strncpy (framework_pos, "/Resources", PATH_MAX - (framework_pos - raw_path));
#endif
                    }
#endif
                    FileSpec::Resolve (raw_path, resolved_path, sizeof(resolved_path));
                    g_lldb_support_exe_dir.SetCString(resolved_path);
                }
                if (log)
                    log->Printf("Host::GetLLDBPath(ePathTypeSupportExecutableDir) => '%s'", g_lldb_support_exe_dir.GetCString());
            }
            file_spec.GetDirectory() = g_lldb_support_exe_dir;
            return (bool)file_spec.GetDirectory();
        }
        break;

    case ePathTypeHeaderDir:
        {
            static ConstString g_lldb_headers_dir;
            if (!g_lldb_headers_dir)
            {
#if defined (__APPLE__)
                FileSpec lldb_file_spec;
                if (GetLLDBPath (ePathTypeLLDBShlibDir, lldb_file_spec))
                {
                    char raw_path[PATH_MAX];
                    char resolved_path[PATH_MAX];
                    lldb_file_spec.GetPath(raw_path, sizeof(raw_path));

                    char *framework_pos = ::strstr (raw_path, "LLDB.framework");
                    if (framework_pos)
                    {
                        framework_pos += strlen("LLDB.framework");
                        ::strncpy (framework_pos, "/Headers", PATH_MAX - (framework_pos - raw_path));
                    }
                    FileSpec::Resolve (raw_path, resolved_path, sizeof(resolved_path));
                    g_lldb_headers_dir.SetCString(resolved_path);
                }
#else
                // TODO: Anyone know how we can determine this for linux? Other systems??
                g_lldb_headers_dir.SetCString ("/opt/local/include/lldb");
#endif
                if (log)
                    log->Printf("Host::GetLLDBPath(ePathTypeHeaderDir) => '%s'", g_lldb_headers_dir.GetCString());
            }
            file_spec.GetDirectory() = g_lldb_headers_dir;
            return (bool)file_spec.GetDirectory();
        }
        break;

#ifdef LLDB_DISABLE_PYTHON
    case ePathTypePythonDir:
        return false;
#else
    case ePathTypePythonDir:
        {
            static ConstString g_lldb_python_dir;
            if (!g_lldb_python_dir)
            {
                FileSpec lldb_file_spec;
                if (GetLLDBPath (ePathTypeLLDBShlibDir, lldb_file_spec))
                {
                    char raw_path[PATH_MAX];
                    char resolved_path[PATH_MAX];
                    lldb_file_spec.GetPath(raw_path, sizeof(raw_path));

#if defined (__APPLE__)
                    char *framework_pos = ::strstr (raw_path, "LLDB.framework");
                    if (framework_pos)
                    {
                        framework_pos += strlen("LLDB.framework");
                        ::strncpy (framework_pos, "/Resources/Python", PATH_MAX - (framework_pos - raw_path));
                    }
#else
                    llvm::SmallString<256> python_version_dir;
                    llvm::raw_svector_ostream os(python_version_dir);
                    os << "/python" << PY_MAJOR_VERSION << '.' << PY_MINOR_VERSION << "/site-packages";
                    os.flush();

                    // We may get our string truncated. Should we protect
                    // this with an assert?

                    ::strncat(raw_path, python_version_dir.c_str(),
                              sizeof(raw_path) - strlen(raw_path) - 1);

#endif
                    FileSpec::Resolve (raw_path, resolved_path, sizeof(resolved_path));
                    g_lldb_python_dir.SetCString(resolved_path);
                }

                if (log)
                    log->Printf("Host::GetLLDBPath(ePathTypePythonDir) => '%s'", g_lldb_python_dir.GetCString());

            }
            file_spec.GetDirectory() = g_lldb_python_dir;
            return (bool)file_spec.GetDirectory();
        }
        break;
#endif

    case ePathTypeLLDBSystemPlugins:    // System plug-ins directory
        {
#if defined (__APPLE__) || defined(__linux__)
            static ConstString g_lldb_system_plugin_dir;
            static bool g_lldb_system_plugin_dir_located = false;
            if (!g_lldb_system_plugin_dir_located)
            {
                g_lldb_system_plugin_dir_located = true;
#if defined (__APPLE__)
                FileSpec lldb_file_spec;
                if (GetLLDBPath (ePathTypeLLDBShlibDir, lldb_file_spec))
                {
                    char raw_path[PATH_MAX];
                    char resolved_path[PATH_MAX];
                    lldb_file_spec.GetPath(raw_path, sizeof(raw_path));

                    char *framework_pos = ::strstr (raw_path, "LLDB.framework");
                    if (framework_pos)
                    {
                        framework_pos += strlen("LLDB.framework");
                        ::strncpy (framework_pos, "/Resources/PlugIns", PATH_MAX - (framework_pos - raw_path));
                        FileSpec::Resolve (raw_path, resolved_path, sizeof(resolved_path));
                        g_lldb_system_plugin_dir.SetCString(resolved_path);
                    }
                    return false;
                }
#elif defined (__linux__)
                FileSpec lldb_file_spec("/usr/lib/lldb", true);
                if (lldb_file_spec.Exists())
                {
                    g_lldb_system_plugin_dir.SetCString(lldb_file_spec.GetPath().c_str());
                }
#endif // __APPLE__ || __linux__

                if (log)
                    log->Printf("Host::GetLLDBPath(ePathTypeLLDBSystemPlugins) => '%s'", g_lldb_system_plugin_dir.GetCString());

            }

            if (g_lldb_system_plugin_dir)
            {
                file_spec.GetDirectory() = g_lldb_system_plugin_dir;
                return true;
            }
#else
            // TODO: where would system LLDB plug-ins be located on other systems?
            return false;
#endif
        }
        break;

    case ePathTypeLLDBUserPlugins:      // User plug-ins directory
        {
#if defined (__APPLE__)
            static ConstString g_lldb_user_plugin_dir;
            if (!g_lldb_user_plugin_dir)
            {
                char user_plugin_path[PATH_MAX];
                if (FileSpec::Resolve ("~/Library/Application Support/LLDB/PlugIns",
                                       user_plugin_path,
                                       sizeof(user_plugin_path)))
                {
                    g_lldb_user_plugin_dir.SetCString(user_plugin_path);
                }
            }
            file_spec.GetDirectory() = g_lldb_user_plugin_dir;
            return (bool)file_spec.GetDirectory();
#elif defined (__linux__)
            static ConstString g_lldb_user_plugin_dir;
            if (!g_lldb_user_plugin_dir)
            {
                // XDG Base Directory Specification
                // http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html
                // If XDG_DATA_HOME exists, use that, otherwise use ~/.local/share/lldb.
                FileSpec lldb_file_spec;
                const char *xdg_data_home = getenv("XDG_DATA_HOME");
                if (xdg_data_home && xdg_data_home[0])
                {
                    std::string user_plugin_dir (xdg_data_home);
                    user_plugin_dir += "/lldb";
                    lldb_file_spec.SetFile (user_plugin_dir.c_str(), true);
                }
                else
                {
                    const char *home_dir = getenv("HOME");
                    if (home_dir && home_dir[0])
                    {
                        std::string user_plugin_dir (home_dir);
                        user_plugin_dir += "/.local/share/lldb";
                        lldb_file_spec.SetFile (user_plugin_dir.c_str(), true);
                    }
                }

                if (lldb_file_spec.Exists())
                    g_lldb_user_plugin_dir.SetCString(lldb_file_spec.GetPath().c_str());
                if (log)
                    log->Printf("Host::GetLLDBPath(ePathTypeLLDBUserPlugins) => '%s'", g_lldb_user_plugin_dir.GetCString());
            }
            file_spec.GetDirectory() = g_lldb_user_plugin_dir;
            return (bool)file_spec.GetDirectory();
#endif
            // TODO: where would user LLDB plug-ins be located on other systems?
            return false;
        }
    }

    return false;
}


bool
Host::GetHostname (std::string &s)
{
    char hostname[PATH_MAX];
    hostname[sizeof(hostname) - 1] = '\0';
    if (::gethostname (hostname, sizeof(hostname) - 1) == 0)
    {
        struct hostent* h = ::gethostbyname (hostname);
        if (h)
            s.assign (h->h_name);
        else
            s.assign (hostname);
        return true;
    }
    return false;
}

#ifndef _WIN32

const char *
Host::GetUserName (uint32_t uid, std::string &user_name)
{
    struct passwd user_info;
    struct passwd *user_info_ptr = &user_info;
    char user_buffer[PATH_MAX];
    size_t user_buffer_size = sizeof(user_buffer);
    if (::getpwuid_r (uid,
                      &user_info,
                      user_buffer,
                      user_buffer_size,
                      &user_info_ptr) == 0)
    {
        if (user_info_ptr)
        {
            user_name.assign (user_info_ptr->pw_name);
            return user_name.c_str();
        }
    }
    user_name.clear();
    return NULL;
}

const char *
Host::GetGroupName (uint32_t gid, std::string &group_name)
{
    char group_buffer[PATH_MAX];
    size_t group_buffer_size = sizeof(group_buffer);
    struct group group_info;
    struct group *group_info_ptr = &group_info;
    // Try the threadsafe version first
    if (::getgrgid_r (gid,
                      &group_info,
                      group_buffer,
                      group_buffer_size,
                      &group_info_ptr) == 0)
    {
        if (group_info_ptr)
        {
            group_name.assign (group_info_ptr->gr_name);
            return group_name.c_str();
        }
    }
    else
    {
        // The threadsafe version isn't currently working
        // for me on darwin, but the non-threadsafe version
        // is, so I am calling it below.
        group_info_ptr = ::getgrgid (gid);
        if (group_info_ptr)
        {
            group_name.assign (group_info_ptr->gr_name);
            return group_name.c_str();
        }
    }
    group_name.clear();
    return NULL;
}

uint32_t
Host::GetUserID ()
{
    return getuid();
}

uint32_t
Host::GetGroupID ()
{
    return getgid();
}

uint32_t
Host::GetEffectiveUserID ()
{
    return geteuid();
}

uint32_t
Host::GetEffectiveGroupID ()
{
    return getegid();
}

#endif

#if !defined (__APPLE__) && !defined (__FreeBSD__) && !defined (__FreeBSD_kernel__) // see macosx/Host.mm
bool
Host::GetOSBuildString (std::string &s)
{
    s.clear();
    return false;
}

bool
Host::GetOSKernelDescription (std::string &s)
{
    s.clear();
    return false;
}
#endif

#if !defined (__APPLE__) && !defined (__FreeBSD__) && !defined (__FreeBSD_kernel__) && !defined(__linux__)
uint32_t
Host::FindProcesses (const ProcessInstanceInfoMatch &match_info, ProcessInstanceInfoList &process_infos)
{
    process_infos.Clear();
    return process_infos.GetSize();
}

bool
Host::GetProcessInfo (lldb::pid_t pid, ProcessInstanceInfo &process_info)
{
    process_info.Clear();
    return false;
}
#endif

#if !defined(__linux__)
bool
Host::FindProcessThreads (const lldb::pid_t pid, TidMap &tids_to_attach)
{
    return false;
}
#endif

lldb::TargetSP
Host::GetDummyTarget (lldb_private::Debugger &debugger)
{
    static TargetSP g_dummy_target_sp;

    // FIXME: Maybe the dummy target should be per-Debugger
    if (!g_dummy_target_sp || !g_dummy_target_sp->IsValid())
    {
        ArchSpec arch(Target::GetDefaultArchitecture());
        if (!arch.IsValid())
            arch = Host::GetArchitecture ();
        Error err = debugger.GetTargetList().CreateTarget(debugger,
                                                          NULL,
                                                          arch.GetTriple().getTriple().c_str(),
                                                          false,
                                                          NULL,
                                                          g_dummy_target_sp);
    }

    return g_dummy_target_sp;
}

struct ShellInfo
{
    ShellInfo () :
        process_reaped (false),
        can_delete (false),
        pid (LLDB_INVALID_PROCESS_ID),
        signo(-1),
        status(-1)
    {
    }

    lldb_private::Predicate<bool> process_reaped;
    lldb_private::Predicate<bool> can_delete;
    lldb::pid_t pid;
    int signo;
    int status;
};

static bool
MonitorShellCommand (void *callback_baton,
                     lldb::pid_t pid,
                     bool exited,       // True if the process did exit
                     int signo,         // Zero for no signal
                     int status)   // Exit value of process if signal is zero
{
    ShellInfo *shell_info = (ShellInfo *)callback_baton;
    shell_info->pid = pid;
    shell_info->signo = signo;
    shell_info->status = status;
    // Let the thread running Host::RunShellCommand() know that the process
    // exited and that ShellInfo has been filled in by broadcasting to it
    shell_info->process_reaped.SetValue(1, eBroadcastAlways);
    // Now wait for a handshake back from that thread running Host::RunShellCommand
    // so we know that we can delete shell_info_ptr
    shell_info->can_delete.WaitForValueEqualTo(true);
    // Sleep a bit to allow the shell_info->can_delete.SetValue() to complete...
    usleep(1000);
    // Now delete the shell info that was passed into this function
    delete shell_info;
    return true;
}

Error
Host::RunShellCommand (const char *command,
                       const char *working_dir,
                       int *status_ptr,
                       int *signo_ptr,
                       std::string *command_output_ptr,
                       uint32_t timeout_sec,
                       const char *shell)
{
    Error error;
    ProcessLaunchInfo launch_info;
    if (shell && shell[0])
    {
        // Run the command in a shell
        launch_info.SetShell(shell);
        launch_info.GetArguments().AppendArgument(command);
        const bool localhost = true;
        const bool will_debug = false;
        const bool first_arg_is_full_shell_command = true;
        launch_info.ConvertArgumentsForLaunchingInShell (error,
                                                         localhost,
                                                         will_debug,
                                                         first_arg_is_full_shell_command,
                                                         0);
    }
    else
    {
        // No shell, just run it
        Args args (command);
        const bool first_arg_is_executable = true;
        launch_info.SetArguments(args, first_arg_is_executable);
    }

    if (working_dir)
        launch_info.SetWorkingDirectory(working_dir);
    char output_file_path_buffer[L_tmpnam];
    const char *output_file_path = NULL;
    if (command_output_ptr)
    {
        // Create a temporary file to get the stdout/stderr and redirect the
        // output of the command into this file. We will later read this file
        // if all goes well and fill the data into "command_output_ptr"
        output_file_path = ::tmpnam(output_file_path_buffer);
        launch_info.AppendSuppressFileAction (STDIN_FILENO, true, false);
        launch_info.AppendOpenFileAction(STDOUT_FILENO, output_file_path, false, true);
        launch_info.AppendDuplicateFileAction(STDOUT_FILENO, STDERR_FILENO);
    }
    else
    {
        launch_info.AppendSuppressFileAction (STDIN_FILENO, true, false);
        launch_info.AppendSuppressFileAction (STDOUT_FILENO, false, true);
        launch_info.AppendSuppressFileAction (STDERR_FILENO, false, true);
    }

    // The process monitor callback will delete the 'shell_info_ptr' below...
    std::unique_ptr<ShellInfo> shell_info_ap (new ShellInfo());

    const bool monitor_signals = false;
    launch_info.SetMonitorProcessCallback(MonitorShellCommand, shell_info_ap.get(), monitor_signals);

    error = LaunchProcess (launch_info);
    const lldb::pid_t pid = launch_info.GetProcessID();

    if (error.Success() && pid == LLDB_INVALID_PROCESS_ID)
        error.SetErrorString("failed to get process ID");

    if (error.Success())
    {
        // The process successfully launched, so we can defer ownership of
        // "shell_info" to the MonitorShellCommand callback function that will
        // get called when the process dies. We release the unique pointer as it
        // doesn't need to delete the ShellInfo anymore.
        ShellInfo *shell_info = shell_info_ap.release();
        TimeValue *timeout_ptr = nullptr;
        TimeValue timeout_time(TimeValue::Now());
        if (timeout_sec > 0) {
            timeout_time.OffsetWithSeconds(timeout_sec);
            timeout_ptr = &timeout_time;
        }
        bool timed_out = false;
        shell_info->process_reaped.WaitForValueEqualTo(true, timeout_ptr, &timed_out);
        if (timed_out)
        {
            error.SetErrorString("timed out waiting for shell command to complete");

            // Kill the process since it didn't complete withint the timeout specified
            Kill (pid, SIGKILL);
            // Wait for the monitor callback to get the message
            timeout_time = TimeValue::Now();
            timeout_time.OffsetWithSeconds(1);
            timed_out = false;
            shell_info->process_reaped.WaitForValueEqualTo(true, &timeout_time, &timed_out);
        }
        else
        {
            if (status_ptr)
                *status_ptr = shell_info->status;

            if (signo_ptr)
                *signo_ptr = shell_info->signo;

            if (command_output_ptr)
            {
                command_output_ptr->clear();
                FileSpec file_spec(output_file_path, File::eOpenOptionRead);
                uint64_t file_size = file_spec.GetByteSize();
                if (file_size > 0)
                {
                    if (file_size > command_output_ptr->max_size())
                    {
                        error.SetErrorStringWithFormat("shell command output is too large to fit into a std::string");
                    }
                    else
                    {
                        command_output_ptr->resize(file_size);
                        file_spec.ReadFileContents(0, &((*command_output_ptr)[0]), command_output_ptr->size(), &error);
                    }
                }
            }
        }
        shell_info->can_delete.SetValue(true, eBroadcastAlways);
    }

    if (output_file_path)
        ::unlink (output_file_path);
    // Handshake with the monitor thread, or just let it know in advance that
    // it can delete "shell_info" in case we timed out and were not able to kill
    // the process...
    return error;
}

#if defined(__linux__) || defined(__FreeBSD__)
// The functions below implement process launching via posix_spawn() for Linux
// and FreeBSD.

// The posix_spawn() and posix_spawnp() functions first appeared in FreeBSD 8.0,
static Error
LaunchProcessPosixSpawn (const char *exe_path, ProcessLaunchInfo &launch_info, ::pid_t &pid)
{
    Error error;
    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_HOST | LIBLLDB_LOG_PROCESS));

    assert(exe_path);
    assert(!launch_info.GetFlags().Test (eLaunchFlagDebug));

    posix_spawnattr_t attr;

    error.SetError( ::posix_spawnattr_init (&attr), eErrorTypePOSIX);
    error.LogIfError(log, "::posix_spawnattr_init ( &attr )");
    if (error.Fail())
        return error;

    // Make a quick class that will cleanup the posix spawn attributes in case
    // we return in the middle of this function.
    lldb_utility::CleanUp <posix_spawnattr_t *, int> posix_spawnattr_cleanup(&attr, posix_spawnattr_destroy);

    sigset_t no_signals;
    sigset_t all_signals;
    sigemptyset (&no_signals);
    sigfillset (&all_signals);
    ::posix_spawnattr_setsigmask(&attr, &all_signals);
    ::posix_spawnattr_setsigdefault(&attr, &no_signals);

    short flags = POSIX_SPAWN_SETSIGDEF | POSIX_SPAWN_SETSIGMASK;

    error.SetError( ::posix_spawnattr_setflags (&attr, flags), eErrorTypePOSIX);
    error.LogIfError(log, "::posix_spawnattr_setflags ( &attr, flags=0x%8.8x )", flags);
    if (error.Fail())
        return error;

    const size_t num_file_actions = launch_info.GetNumFileActions ();
    posix_spawn_file_actions_t file_actions, *file_action_ptr = NULL;
    // Make a quick class that will cleanup the posix spawn attributes in case
    // we return in the middle of this function.
    lldb_utility::CleanUp <posix_spawn_file_actions_t *, int>
        posix_spawn_file_actions_cleanup (file_action_ptr, NULL, posix_spawn_file_actions_destroy);

    if (num_file_actions > 0)
    {
        error.SetError( ::posix_spawn_file_actions_init (&file_actions), eErrorTypePOSIX);
        error.LogIfError(log, "::posix_spawn_file_actions_init ( &file_actions )");
        if (error.Fail())
            return error;

        file_action_ptr = &file_actions;
        posix_spawn_file_actions_cleanup.set(file_action_ptr);

        for (size_t i = 0; i < num_file_actions; ++i)
        {
            const ProcessLaunchInfo::FileAction *launch_file_action = launch_info.GetFileActionAtIndex(i);
            if (launch_file_action &&
                !ProcessLaunchInfo::FileAction::AddPosixSpawnFileAction (&file_actions,
                                                                         launch_file_action,
                                                                         log,
                                                                         error))
                return error;
        }
    }

    // Change working directory if neccessary.
    char current_dir[PATH_MAX];
    current_dir[0] = '\0';

    const char *working_dir = launch_info.GetWorkingDirectory();
    if (working_dir != NULL)
    {
        if (::getcwd(current_dir, sizeof(current_dir)) == NULL)
        {
            error.SetError(errno, eErrorTypePOSIX);
            error.LogIfError(log, "unable to save the current directory");
            return error;
        }

        if (::chdir(working_dir) == -1)
        {
            error.SetError(errno, eErrorTypePOSIX);
            error.LogIfError(log, "unable to change working directory to %s", working_dir);
            return error;
        }
    }

    const char *tmp_argv[2];
    char * const *argv = (char * const*)launch_info.GetArguments().GetConstArgumentVector();
    char * const *envp = (char * const*)launch_info.GetEnvironmentEntries().GetConstArgumentVector();

    // Prepare minimal argument list if we didn't get it from the launch_info structure.
    // We must pass argv into posix_spawnp and it must contain at least two items -
    // pointer to an executable and NULL.
    if (argv == NULL)
    {
        tmp_argv[0] = exe_path;
        tmp_argv[1] = NULL;
        argv = (char * const*)tmp_argv;
    }

    error.SetError (::posix_spawnp (&pid,
                                    exe_path,
                                    (num_file_actions > 0) ? &file_actions : NULL,
                                    &attr,
                                    argv,
                                    envp),
                    eErrorTypePOSIX);

    error.LogIfError(log, "::posix_spawnp ( pid => %i, path = '%s', file_actions = %p, attr = %p, argv = %p, envp = %p )",
                     pid, exe_path, file_action_ptr, &attr, argv, envp);

    // Change back the current directory.
    // NOTE: do not override previously established error from posix_spawnp.
    if (working_dir != NULL && ::chdir(current_dir) == -1 && error.Success())
    {
        error.SetError(errno, eErrorTypePOSIX);
        error.LogIfError(log, "unable to change current directory back to %s",
                         current_dir);
    }

    return error;
}


Error
Host::LaunchProcess (ProcessLaunchInfo &launch_info)
{
    Error error;
    char exe_path[PATH_MAX];

    PlatformSP host_platform_sp (Platform::GetDefaultPlatform ());

    const ArchSpec &arch_spec = launch_info.GetArchitecture();

    FileSpec exe_spec(launch_info.GetExecutableFile());

    FileSpec::FileType file_type = exe_spec.GetFileType();
    if (file_type != FileSpec::eFileTypeRegular)
    {
        lldb::ModuleSP exe_module_sp;
        error = host_platform_sp->ResolveExecutable (exe_spec,
                                                     arch_spec,
                                                     exe_module_sp,
                                                     NULL);

        if (error.Fail())
            return error;

        if (exe_module_sp)
            exe_spec = exe_module_sp->GetFileSpec();
    }

    if (exe_spec.Exists())
    {
        exe_spec.GetPath (exe_path, sizeof(exe_path));
    }
    else
    {
        launch_info.GetExecutableFile().GetPath (exe_path, sizeof(exe_path));
        error.SetErrorStringWithFormat ("executable doesn't exist: '%s'", exe_path);
        return error;
    }

    assert(!launch_info.GetFlags().Test (eLaunchFlagLaunchInTTY));

    ::pid_t pid = LLDB_INVALID_PROCESS_ID;

    error = LaunchProcessPosixSpawn(exe_path, launch_info, pid);

    if (pid != LLDB_INVALID_PROCESS_ID)
    {
        // If all went well, then set the process ID into the launch info
        launch_info.SetProcessID(pid);

        // Make sure we reap any processes we spawn or we will have zombies.
        if (!launch_info.MonitorProcess())
        {
            const bool monitor_signals = false;
            StartMonitoringChildProcess (Process::SetProcessExitStatus,
                                         NULL,
                                         pid,
                                         monitor_signals);
        }
    }
    else
    {
        // Invalid process ID, something didn't go well
        if (error.Success())
            error.SetErrorString ("process launch failed for unknown reasons");
    }
    return error;
}

#endif // defined(__linux__) or defined(__FreeBSD__)

#ifndef _WIN32

size_t
Host::GetPageSize()
{
    return ::getpagesize();
}

uint32_t
Host::GetNumberCPUS ()
{
    static uint32_t g_num_cores = UINT32_MAX;
    if (g_num_cores == UINT32_MAX)
    {
#if defined(__APPLE__) or defined (__linux__) or defined (__FreeBSD__) or defined (__FreeBSD_kernel__)

        g_num_cores = ::sysconf(_SC_NPROCESSORS_ONLN);

#else

        // Assume POSIX support if a host specific case has not been supplied above
        g_num_cores = 0;
        int num_cores = 0;
        size_t num_cores_len = sizeof(num_cores);
#ifdef HW_AVAILCPU
        int mib[] = { CTL_HW, HW_AVAILCPU };
#else
        int mib[] = { CTL_HW, HW_NCPU };
#endif

        /* get the number of CPUs from the system */
        if (sysctl(mib, sizeof(mib)/sizeof(int), &num_cores, &num_cores_len, NULL, 0) == 0 && (num_cores > 0))
        {
            g_num_cores = num_cores;
        }
        else
        {
            mib[1] = HW_NCPU;
            num_cores_len = sizeof(num_cores);
            if (sysctl(mib, sizeof(mib)/sizeof(int), &num_cores, &num_cores_len, NULL, 0) == 0 && (num_cores > 0))
            {
                if (num_cores > 0)
                    g_num_cores = num_cores;
            }
        }
#endif
    }
    return g_num_cores;
}

void
Host::Kill(lldb::pid_t pid, int signo)
{
    ::kill(pid, signo);
}

#endif

#if !defined (__APPLE__)
bool
Host::OpenFileInExternalEditor (const FileSpec &file_spec, uint32_t line_no)
{
    return false;
}

void
Host::SetCrashDescriptionWithFormat (const char *format, ...)
{
}

void
Host::SetCrashDescription (const char *description)
{
}

lldb::pid_t
Host::LaunchApplication (const FileSpec &app_file_spec)
{
    return LLDB_INVALID_PROCESS_ID;
}

#endif


#ifdef LLDB_DISABLE_POSIX

Error
Host::MakeDirectory (const char* path, uint32_t mode)
{
    Error error;
    error.SetErrorStringWithFormat("%s in not implemented on this host", __PRETTY_FUNCTION__);
    return error;
}

Error
Host::GetFilePermissions (const char* path, uint32_t &file_permissions)
{
    Error error;
    error.SetErrorStringWithFormat("%s is not supported on this host", __PRETTY_FUNCTION__);
    return error;
}

Error
Host::SetFilePermissions (const char* path, uint32_t file_permissions)
{
    Error error;
    error.SetErrorStringWithFormat("%s is not supported on this host", __PRETTY_FUNCTION__);
    return error;
}

Error
Host::Symlink (const char *src, const char *dst)
{
    Error error;
    error.SetErrorStringWithFormat("%s is not supported on this host", __PRETTY_FUNCTION__);
    return error;
}

Error
Host::Readlink (const char *path, char *buf, size_t buf_len)
{
    Error error;
    error.SetErrorStringWithFormat("%s is not supported on this host", __PRETTY_FUNCTION__);
    return error;
}

Error
Host::Unlink (const char *path)
{
    Error error;
    error.SetErrorStringWithFormat("%s is not supported on this host", __PRETTY_FUNCTION__);
    return error;
}

#else

Error
Host::MakeDirectory (const char* path, uint32_t file_permissions)
{
    Error error;
    if (path && path[0])
    {
        if (::mkdir(path, file_permissions) != 0)
        {
            error.SetErrorToErrno();
            switch (error.GetError())
            {
            case ENOENT:
                {
                    // Parent directory doesn't exist, so lets make it if we can
                    FileSpec spec(path, false);
                    if (spec.GetDirectory() && spec.GetFilename())
                    {
                        // Make the parent directory and try again
                        Error error2 = Host::MakeDirectory(spec.GetDirectory().GetCString(), file_permissions);
                        if (error2.Success())
                        {
                            // Try and make the directory again now that the parent directory was made successfully
                            if (::mkdir(path, file_permissions) == 0)
                                error.Clear();
                            else
                                error.SetErrorToErrno();
                        }
                    }
                }
                break;
            case EEXIST:
                {
                    FileSpec path_spec(path, false);
                    if (path_spec.IsDirectory())
                        error.Clear(); // It is a directory and it already exists
                }
                break;
            }
        }
    }
    else
    {
        error.SetErrorString("empty path");
    }
    return error;
}

Error
Host::GetFilePermissions (const char* path, uint32_t &file_permissions)
{
    Error error;
    struct stat file_stats;
    if (::stat (path, &file_stats) == 0)
    {
        // The bits in "st_mode" currently match the definitions
        // for the file mode bits in unix.
        file_permissions = file_stats.st_mode & (S_IRWXU | S_IRWXG | S_IRWXO);
    }
    else
    {
        error.SetErrorToErrno();
    }
    return error;
}

Error
Host::SetFilePermissions (const char* path, uint32_t file_permissions)
{
    Error error;
    if (::chmod(path, file_permissions) != 0)
        error.SetErrorToErrno();
    return error;
}

Error
Host::Symlink (const char *src, const char *dst)
{
    Error error;
    if (::symlink(dst, src) == -1)
        error.SetErrorToErrno();
    return error;
}

Error
Host::Unlink (const char *path)
{
    Error error;
    if (::unlink(path) == -1)
        error.SetErrorToErrno();
    return error;
}

Error
Host::Readlink (const char *path, char *buf, size_t buf_len)
{
    Error error;
    ssize_t count = ::readlink(path, buf, buf_len);
    if (count < 0)
        error.SetErrorToErrno();
    else if (count < (buf_len-1))
        buf[count] = '\0'; // Success
    else
        error.SetErrorString("'buf' buffer is too small to contain link contents");
    return error;
}


#endif

typedef std::map<lldb::user_id_t, lldb::FileSP> FDToFileMap;
FDToFileMap& GetFDToFileMap()
{
    static FDToFileMap g_fd2filemap;
    return g_fd2filemap;
}

lldb::user_id_t
Host::OpenFile (const FileSpec& file_spec,
                uint32_t flags,
                uint32_t mode,
                Error &error)
{
    std::string path (file_spec.GetPath());
    if (path.empty())
    {
        error.SetErrorString("empty path");
        return UINT64_MAX;
    }
    FileSP file_sp(new File());
    error = file_sp->Open(path.c_str(),flags,mode);
    if (file_sp->IsValid() == false)
        return UINT64_MAX;
    lldb::user_id_t fd = file_sp->GetDescriptor();
    GetFDToFileMap()[fd] = file_sp;
    return fd;
}

bool
Host::CloseFile (lldb::user_id_t fd, Error &error)
{
    if (fd == UINT64_MAX)
    {
        error.SetErrorString ("invalid file descriptor");
        return false;
    }
    FDToFileMap& file_map = GetFDToFileMap();
    FDToFileMap::iterator pos = file_map.find(fd);
    if (pos == file_map.end())
    {
        error.SetErrorStringWithFormat ("invalid host file descriptor %" PRIu64, fd);
        return false;
    }
    FileSP file_sp = pos->second;
    if (!file_sp)
    {
        error.SetErrorString ("invalid host backing file");
        return false;
    }
    error = file_sp->Close();
    file_map.erase(pos);
    return error.Success();
}

uint64_t
Host::WriteFile (lldb::user_id_t fd, uint64_t offset, const void* src, uint64_t src_len, Error &error)
{
    if (fd == UINT64_MAX)
    {
        error.SetErrorString ("invalid file descriptor");
        return UINT64_MAX;
    }
    FDToFileMap& file_map = GetFDToFileMap();
    FDToFileMap::iterator pos = file_map.find(fd);
    if (pos == file_map.end())
    {
        error.SetErrorStringWithFormat("invalid host file descriptor %" PRIu64 , fd);
        return false;
    }
    FileSP file_sp = pos->second;
    if (!file_sp)
    {
        error.SetErrorString ("invalid host backing file");
        return UINT64_MAX;
    }
    if (file_sp->SeekFromStart(offset, &error) != offset || error.Fail())
        return UINT64_MAX;
    size_t bytes_written = src_len;
    error = file_sp->Write(src, bytes_written);
    if (error.Fail())
        return UINT64_MAX;
    return bytes_written;
}

uint64_t
Host::ReadFile (lldb::user_id_t fd, uint64_t offset, void* dst, uint64_t dst_len, Error &error)
{
    if (fd == UINT64_MAX)
    {
        error.SetErrorString ("invalid file descriptor");
        return UINT64_MAX;
    }
    FDToFileMap& file_map = GetFDToFileMap();
    FDToFileMap::iterator pos = file_map.find(fd);
    if (pos == file_map.end())
    {
        error.SetErrorStringWithFormat ("invalid host file descriptor %" PRIu64, fd);
        return false;
    }
    FileSP file_sp = pos->second;
    if (!file_sp)
    {
        error.SetErrorString ("invalid host backing file");
        return UINT64_MAX;
    }
    if (file_sp->SeekFromStart(offset, &error) != offset || error.Fail())
        return UINT64_MAX;
    size_t bytes_read = dst_len;
    error = file_sp->Read(dst ,bytes_read);
    if (error.Fail())
        return UINT64_MAX;
    return bytes_read;
}

lldb::user_id_t
Host::GetFileSize (const FileSpec& file_spec)
{
    return file_spec.GetByteSize();
}

bool
Host::GetFileExists (const FileSpec& file_spec)
{
    return file_spec.Exists();
}

bool
Host::CalculateMD5 (const FileSpec& file_spec,
                    uint64_t &low,
                    uint64_t &high)
{
#if defined (__APPLE__)
    StreamString md5_cmd_line;
    md5_cmd_line.Printf("md5 -q '%s'", file_spec.GetPath().c_str());
    std::string hash_string;
    Error err = Host::RunShellCommand(md5_cmd_line.GetData(), NULL, NULL, NULL, &hash_string, 60);
    if (err.Fail())
        return false;
    // a correctly formed MD5 is 16-bytes, that is 32 hex digits
    // if the output is any other length it is probably wrong
    if (hash_string.size() != 32)
        return false;
    std::string part1(hash_string,0,16);
    std::string part2(hash_string,16);
    const char* part1_cstr = part1.c_str();
    const char* part2_cstr = part2.c_str();
    high = ::strtoull(part1_cstr, NULL, 16);
    low = ::strtoull(part2_cstr, NULL, 16);
    return true;
#else
    // your own MD5 implementation here
    return false;
#endif
}