fish-shell/proc.cpp

/** \file proc.c

Utilities for keeping track of jobs, processes and subshells, as
well as signal handling functions for tracking children. These
functions do not themselves launch new processes, the exec library
will call proc to create representations of the running jobs as
needed.

Some of the code in this file is based on code from the Glibc manual.

*/
#include "config.h"

#include <stdlib.h>
#include <stdio.h>
#include <sys/wait.h>
#include <wchar.h>
#include <string.h>
#include <errno.h>
#include <termios.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <algorithm>

#ifdef HAVE_SYS_IOCTL_H
#include <sys/ioctl.h>
#endif

#include <unistd.h>
#include <signal.h>
#include <dirent.h>
#include <sys/time.h>

#if HAVE_NCURSES_H
#include <ncurses.h>
#else
#include <curses.h>
#endif

#if HAVE_TERM_H
#include <term.h>
#elif HAVE_NCURSES_TERM_H
#include <ncurses/term.h>
#endif

#ifdef HAVE_SIGINFO_H
#include <siginfo.h>
#endif

#ifdef HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif

#include "fallback.h"
#include "util.h"

#include "wutil.h"
#include "proc.h"
#include "common.h"
#include "reader.h"
#include "sanity.h"
#include "env.h"
#include "parser.h"
#include "signal.h"
#include "event.h"

#include "output.h"

/**
   Size of message buffer
*/
#define MESS_SIZE 256

/**
   Size of buffer for reading buffered output
*/
#define BUFFER_SIZE 4096

/**
	Status of last process to exit
*/
static int last_status=0;

/**
   Signal flag
*/
static sig_atomic_t got_signal=0;

bool job_list_is_empty(void)
{
    ASSERT_IS_MAIN_THREAD();
    return parser_t::principal_parser().job_list().empty();
}

void job_iterator_t::reset()
{
    this->current = job_list->begin();
    this->end = job_list->end();
}

job_iterator_t::job_iterator_t(job_list_t &jobs) : job_list(&jobs)
{
    this->reset();
}


job_iterator_t::job_iterator_t() : job_list(&parser_t::principal_parser().job_list())
{
    ASSERT_IS_MAIN_THREAD();
    this->reset();
}

void print_jobs(void)
{
    job_iterator_t jobs;
    job_t *j;
    while ((j = jobs.next()))
    {
        printf("%p -> %ls -> (foreground %d, complete %d, stopped %d, constructed %d)\n", j, j->command_wcstr(), job_get_flag(j, JOB_FOREGROUND), job_is_completed(j), job_is_stopped(j), job_get_flag(j, JOB_CONSTRUCTED));
    }
}

int is_interactive_session=0;
int is_subshell=0;
int is_block=0;
int is_login=0;
int is_event=0;
pid_t proc_last_bg_pid = 0;
int job_control_mode = JOB_CONTROL_INTERACTIVE;
int no_exec=0;

static int is_interactive = -1;

static bool proc_had_barrier = false;

int get_is_interactive(void)
{
    ASSERT_IS_MAIN_THREAD();
    /* is_interactive is initialized to -1; ensure someone has popped/pushed it before then */
    assert(is_interactive >= 0);
    return is_interactive > 0;
}

bool get_proc_had_barrier()
{
    ASSERT_IS_MAIN_THREAD();
    return proc_had_barrier;
}

void set_proc_had_barrier(bool flag)
{
    ASSERT_IS_MAIN_THREAD();
    proc_had_barrier = flag;
}

/**
   The event variable used to send all process event
*/
static event_t event(0);

/**
   A stack containing the values of is_interactive. Used by proc_push_interactive and proc_pop_interactive.
*/
static std::vector<int> interactive_stack;

void proc_init()
{
    proc_push_interactive(0);
}


/**
   Remove job from list of jobs
*/
static int job_remove(job_t *j)
{
    ASSERT_IS_MAIN_THREAD();
    return parser_t::principal_parser().job_remove(j);
}

void job_promote(job_t *job)
{
    ASSERT_IS_MAIN_THREAD();
    parser_t::principal_parser().job_promote(job);
}


/*
  Remove job from the job list and free all memory associated with
  it.
*/
void job_free(job_t * j)
{
    job_remove(j);
    delete j;
}

void proc_destroy()
{
    job_list_t &jobs = parser_t::principal_parser().job_list();
    while (! jobs.empty())
    {
        job_t *job = jobs.front();
        debug(2, L"freeing leaked job %ls", job->command_wcstr());
        job_free(job);
    }
}

void proc_set_last_status(int s)
{
    ASSERT_IS_MAIN_THREAD();
    last_status = s;
}

int proc_get_last_status()
{
    return last_status;
}

/* Basic thread safe job IDs. The vector consumed_job_ids has a true value wherever the job ID corresponding to that slot is in use. The job ID corresponding to slot 0 is 1. */
static pthread_mutex_t job_id_lock = PTHREAD_MUTEX_INITIALIZER;
static std::vector<bool> consumed_job_ids;

job_id_t acquire_job_id(void)
{
    scoped_lock lock(job_id_lock);

    /* Find the index of the first 0 slot */
    std::vector<bool>::iterator slot = std::find(consumed_job_ids.begin(), consumed_job_ids.end(), false);
    if (slot != consumed_job_ids.end())
    {
        /* We found a slot. Note that slot 0 corresponds to job ID 1. */
        *slot = true;
        return (job_id_t)(slot - consumed_job_ids.begin() + 1);
    }
    else
    {
        /* We did not find a slot; create a new slot. The size of the vector is now the job ID (since it is one larger than the slot). */
        consumed_job_ids.push_back(true);
        return (job_id_t)consumed_job_ids.size();
    }
}

void release_job_id(job_id_t jid)
{
    assert(jid > 0);
    scoped_lock lock(job_id_lock);
    size_t slot = (size_t)(jid - 1), count = consumed_job_ids.size();

    /* Make sure this slot is within our vector and is currently set to consumed */
    assert(slot < count);
    assert(consumed_job_ids.at(slot) == true);

    /* Clear it and then resize the vector to eliminate unused trailing job IDs */
    consumed_job_ids.at(slot) = false;
    while (count--)
    {
        if (consumed_job_ids.at(count))
            break;
    }
    consumed_job_ids.resize(count + 1);
}

job_t *job_get(job_id_t id)
{
    ASSERT_IS_MAIN_THREAD();
    return parser_t::principal_parser().job_get(id);
}

job_t *job_get_from_pid(int pid)
{
    ASSERT_IS_MAIN_THREAD();
    return parser_t::principal_parser().job_get_from_pid(pid);
}


/*
   Return true if all processes in the job have stopped or completed.

   \param j the job to test
*/
int job_is_stopped(const job_t *j)
{
    process_t *p;

    for (p = j->first_process; p; p = p->next)
    {
        if (!p->completed && !p->stopped)
        {
            return 0;
        }
    }
    return 1;
}


/*
   Return true if the last processes in the job has completed.

   \param j the job to test
*/
bool job_is_completed(const job_t *j)
{
    assert(j->first_process != NULL);
    bool result = true;
    for (process_t *p = j->first_process; p != NULL; p = p->next)
    {
        if (! p->completed)
        {
            result = false;
            break;
        }
    }
    return result;
}

void job_set_flag(job_t *j, unsigned int flag, int set)
{
    if (set)
    {
        j->flags |= flag;
    }
    else
    {
        j->flags &= ~flag;
    }
}

int job_get_flag(const job_t *j, unsigned int flag)
{
    return !!(j->flags & flag);
}

int job_signal(job_t *j, int signal)
{
    pid_t my_pid = getpid();
    int res = 0;

    if (j->pgid != my_pid)
    {
        res = killpg(j->pgid, SIGHUP);
    }
    else
    {
        for (process_t *p = j->first_process; p; p=p->next)
        {
            if (! p->completed)
            {
                if (p->pid)
                {
                    if (kill(p->pid, SIGHUP))
                    {
                        res = -1;
                        break;
                    }
                }
            }
        }

    }

    return res;
}


/**
   Store the status of the process pid that was returned by waitpid.
   Return 0 if all went well, nonzero otherwise.
   This is called from a signal handler.
*/
static void mark_process_status(const job_t *j, process_t *p, int status)
{
//	debug( 0, L"Process %ls %ls", p->argv[0], WIFSTOPPED (status)?L"stopped":(WIFEXITED( status )?L"exited":(WIFSIGNALED( status )?L"signaled to exit":L"BLARGH")) );
    p->status = status;

    if (WIFSTOPPED(status))
    {
        p->stopped = 1;
    }
    else if (WIFSIGNALED(status) || WIFEXITED(status))
    {
        p->completed = 1;
    }
    else
    {
        ssize_t ignore;

        /* This should never be reached */
        p->completed = 1;

        char mess[MESS_SIZE];
        snprintf(mess,
                 MESS_SIZE,
                 "Process %ld exited abnormally\n",
                 (long) p->pid);
        /*
          If write fails, do nothing. We're in a signal handlers error
          handler. If things aren't working properly, it's safer to
          give up.
         */
        ignore = write(2, mess, strlen(mess));
    }
}

void job_mark_process_as_failed(const job_t *job, process_t *p)
{
    /* The given process failed to even lift off (e.g. posix_spawn failed) and so doesn't have a valid pid. Mark it as dead. */
    for (process_t *cursor = p; cursor != NULL; cursor = cursor->next)
    {
        cursor->completed = 1;
    }
}

/**
   Handle status update for child \c pid. This function is called by
   the signal handler, so it mustn't use malloc or any such hitech
   nonsense.

   \param pid the pid of the process whose status changes
   \param status the status as returned by wait
*/
static void handle_child_status(pid_t pid, int status)
{
    bool found_proc = false;
    const job_t *j = NULL;
    process_t *p = NULL;
//	char mess[MESS_SIZE];
    /*
      snprintf( mess,
      MESS_SIZE,
      "Process %d\n",
      (int) pid );
      write( 2, mess, strlen(mess ));
    */

    job_iterator_t jobs;
    while (! found_proc && (j = jobs.next()))
    {
        process_t *prev=0;
        for (p=j->first_process; p; p=p->next)
        {
            if (pid == p->pid)
            {
                /*				snprintf( mess,
                  MESS_SIZE,
                  "Process %d is %ls from job %ls\n",
                  (int) pid, p->actual_cmd, j->command );
                  write( 2, mess, strlen(mess ));
                */

                mark_process_status(j, p, status);
                if (p->completed && prev != 0)
                {
                    if (!prev->completed && prev->pid)
                    {
                        /*					snprintf( mess,
                          MESS_SIZE,
                          "Kill previously uncompleted process %ls (%d)\n",
                          prev->actual_cmd,
                          prev->pid );
                          write( 2, mess, strlen(mess ));
                        */
                        kill(prev->pid,SIGPIPE);
                    }
                }
                found_proc = true;
                break;
            }
            prev = p;
        }
    }


    if (WIFSIGNALED(status) &&
            (WTERMSIG(status)==SIGINT  ||
             WTERMSIG(status)==SIGQUIT))
    {
        if (!is_interactive_session)
        {
            struct sigaction act;
            sigemptyset(& act.sa_mask);
            act.sa_flags=0;
            act.sa_handler=SIG_DFL;
            sigaction(SIGINT, &act, 0);
            sigaction(SIGQUIT, &act, 0);
            kill(getpid(), WTERMSIG(status));
        }
        else
        {
            /* In an interactive session, tell the principal parser to skip all blocks we're executing so control-C returns control to the user. */
            if (p && found_proc)
            {
                parser_t::skip_all_blocks();
            }
        }
    }

    if (!found_proc)
    {
        /*
           A child we lost track of?

           There have been bugs in both subshell handling and in
           builtin handling that have caused this previously...
        */
        /*		snprintf( mess,
          MESS_SIZE,
          "Process %d not found by %d\n",
          (int) pid, (int)getpid() );

          write( 2, mess, strlen(mess ));
        */
    }
    return;
}

process_t::process_t() :
    argv_array(),
    argv0_narrow(),
    type(),
    internal_block_node(NODE_OFFSET_INVALID),
    actual_cmd(),
    pid(0),
    pipe_write_fd(0),
    pipe_read_fd(0),
    completed(0),
    stopped(0),
    status(0),
    count_help_magic(0),
    next(NULL)
#ifdef HAVE__PROC_SELF_STAT
    ,last_time(),
    last_jiffies(0)
#endif
{
}

process_t::~process_t()
{
    if (this->next != NULL)
        delete this->next;
}

job_t::job_t(job_id_t jobid, const io_chain_t &bio) :
    command_str(),
    command_narrow(),
    block_io(bio),
    first_process(NULL),
    pgid(0),
    tmodes(),
    job_id(jobid),
    flags(0)
{
}

job_t::~job_t()
{
    if (first_process != NULL)
        delete first_process;
    release_job_id(job_id);
}

/* Return all the IO redirections. Start with the block IO, then walk over the processes */
io_chain_t job_t::all_io_redirections() const
{
    io_chain_t result = this->block_io;
    for (process_t *p = this->first_process; p != NULL; p = p->next)
    {
        result.append(p->io_chain());
    }
    return result;
}

/* This is called from a signal handler */
void job_handle_signal(int signal, siginfo_t *info, void *con)
{

    int status;
    pid_t pid;
    int errno_old = errno;

    got_signal = 1;

//	write( 2, "got signal\n", 11 );

    while (1)
    {
        switch (pid=waitpid(-1,&status,WUNTRACED|WNOHANG))
        {
            case 0:
            case -1:
            {
                errno=errno_old;
                return;
            }
            default:

                handle_child_status(pid, status);
                break;
        }
    }
    kill(0, SIGIO);
    errno=errno_old;
}

/**
	Format information about job status for the user to look at.

	\param j the job to test
	\param status a string description of the job exit type
*/
static void format_job_info(const job_t *j, const wchar_t *status)
{
    fwprintf(stdout, L"\r");
    fwprintf(stdout, _(L"Job %d, \'%ls\' has %ls"), j->job_id, j->command_wcstr(), status);
    fflush(stdout);
    tputs(clr_eol,1,&writeb);
    fwprintf(stdout, L"\n");
}

void proc_fire_event(const wchar_t *msg, int type, pid_t pid, int status)
{

    event.type=type;
    event.param1.pid = pid;

    event.arguments.push_back(msg);
    event.arguments.push_back(to_string<int>(pid));
    event.arguments.push_back(to_string<int>(status));
    event_fire(&event);
    event.arguments.resize(0);
}

int job_reap(bool interactive)
{
    ASSERT_IS_MAIN_THREAD();
    job_t *jnext;
    int found=0;

    static int locked = 0;

    locked++;
    
    /* Preserve the exit status */
    const int saved_status = proc_get_last_status();

    /*
      job_read may fire an event handler, we do not want to call
      ourselves recursively (to avoid infinite recursion).
    */
    if (locked>1)
        return 0;

    job_iterator_t jobs;
    jnext = jobs.next();
    while (jnext)
    {
        job_t *j = jnext;
        jnext = jobs.next();

        /*
          If we are reaping only jobs who do not need status messages
          sent to the console, do not consider reaping jobs that need
          status messages
        */
        if ((!job_get_flag(j, JOB_SKIP_NOTIFICATION)) && (!interactive) && (!job_get_flag(j, JOB_FOREGROUND)))
        {
            continue;
        }

        for (process_t *p = j->first_process; p; p=p->next)
        {
            int s;
            if (!p->completed)
                continue;

            if (!p->pid)
                continue;

            s = p->status;

            proc_fire_event(L"PROCESS_EXIT", EVENT_EXIT, p->pid, (WIFSIGNALED(s)?-1:WEXITSTATUS(s)));

            if (WIFSIGNALED(s))
            {
                /*
                   Ignore signal SIGPIPE.We issue it ourselves to the pipe
                   writer when the pipe reader dies.
                */
                if (WTERMSIG(s) != SIGPIPE)
                {
                    int proc_is_job = ((p==j->first_process) && (p->next == 0));
                    if (proc_is_job)
                        job_set_flag(j, JOB_NOTIFIED, 1);
                    if (!job_get_flag(j, JOB_SKIP_NOTIFICATION))
                    {
                        if (proc_is_job)
                            fwprintf(stdout,
                                     _(L"%ls: Job %d, \'%ls\' terminated by signal %ls (%ls)"),
                                     program_name,
                                     j->job_id,
                                     j->command_wcstr(),
                                     sig2wcs(WTERMSIG(p->status)),
                                     signal_get_desc(WTERMSIG(p->status)));
                        else
                            fwprintf(stdout,
                                     _(L"%ls: Process %d, \'%ls\' from job %d, \'%ls\' terminated by signal %ls (%ls)"),
                                     program_name,
                                     p->pid,
                                     p->argv0(),
                                     j->job_id,
                                     j->command_wcstr(),
                                     sig2wcs(WTERMSIG(p->status)),
                                     signal_get_desc(WTERMSIG(p->status)));
                        tputs(clr_eol,1,&writeb);
                        fwprintf(stdout, L"\n");
                        found=1;
                    }

                    /*
                       Clear status so it is not reported more than once
                    */
                    p->status = 0;
                }
            }
        }

        /*
           If all processes have completed, tell the user the job has
           completed and delete it from the active job list.
        */
        if (job_is_completed(j))
        {
            if (!job_get_flag(j, JOB_FOREGROUND) && !job_get_flag(j, JOB_NOTIFIED) && !job_get_flag(j, JOB_SKIP_NOTIFICATION))
            {
                format_job_info(j, _(L"ended"));
                found=1;
            }
            proc_fire_event(L"JOB_EXIT", EVENT_EXIT, -j->pgid, 0);
            proc_fire_event(L"JOB_EXIT", EVENT_JOB_ID, j->job_id, 0);

            job_free(j);
        }
        else if (job_is_stopped(j) && !job_get_flag(j, JOB_NOTIFIED))
        {
            /*
               Notify the user about newly stopped jobs.
            */
            if (!job_get_flag(j, JOB_SKIP_NOTIFICATION))
            {
                format_job_info(j, _(L"stopped"));
                found=1;
            }
            job_set_flag(j, JOB_NOTIFIED, 1);
        }
    }

    if (found)
        fflush(stdout);

    /* Restore the exit status. */
    proc_set_last_status(saved_status);

    locked = 0;

    return found;
}


#ifdef HAVE__PROC_SELF_STAT

/**
   Maximum length of a /proc/[PID]/stat filename
*/
#define FN_SIZE 256

/**
   Get the CPU time for the specified process
*/
unsigned long proc_get_jiffies(process_t *p)
{
    wchar_t fn[FN_SIZE];

    char state;
    int pid, ppid, pgrp,
        session, tty_nr, tpgid,
        exit_signal, processor;

    long int cutime, cstime, priority,
         nice, placeholder, itrealvalue,
         rss;
    unsigned long int flags, minflt, cminflt,
             majflt, cmajflt, utime,
             stime, starttime, vsize,
             rlim, startcode, endcode,
             startstack, kstkesp, kstkeip,
             signal, blocked, sigignore,
             sigcatch, wchan, nswap, cnswap;
    char comm[1024];

    if (p->pid <= 0)
        return 0;

    swprintf(fn, FN_SIZE, L"/proc/%d/stat", p->pid);

    FILE *f = wfopen(fn, "r");
    if (!f)
        return 0;

    int count = fscanf(f,
                       "%d %s %c "
                       "%d %d %d "
                       "%d %d %lu "

                       "%lu %lu %lu "
                       "%lu %lu %lu "
                       "%ld %ld %ld "

                       "%ld %ld %ld "
                       "%lu %lu %ld "
                       "%lu %lu %lu "

                       "%lu %lu %lu "
                       "%lu %lu %lu "
                       "%lu %lu %lu "

                       "%lu %d %d ",

                       &pid, comm, &state,
                       &ppid, &pgrp, &session,
                       &tty_nr, &tpgid, &flags,

                       &minflt, &cminflt, &majflt,
                       &cmajflt, &utime, &stime,
                       &cutime, &cstime, &priority,

                       &nice, &placeholder, &itrealvalue,
                       &starttime, &vsize, &rss,
                       &rlim, &startcode, &endcode,

                       &startstack, &kstkesp, &kstkeip,
                       &signal, &blocked, &sigignore,
                       &sigcatch, &wchan, &nswap,

                       &cnswap, &exit_signal, &processor
                      );

    if (count < 17)
    {
        return 0;
    }

    /*
      Don't need to check exit status of fclose on read-only streams
    */
    fclose(f);
    return utime+stime+cutime+cstime;

}

/**
   Update the CPU time for all jobs
*/
void proc_update_jiffies()
{
    job_t* job;
    process_t *p;
    job_iterator_t j;

    for (job = j.next(); job; job = j.next())
    {
        for (p=job->first_process; p; p=p->next)
        {
            gettimeofday(&p->last_time, 0);
            p->last_jiffies = proc_get_jiffies(p);
        }
    }
}


#endif

/**
   Check if there are buffers associated with the job, and select on
   them for a while if available.

   \param j the job to test

   \return 1 if buffers were available, zero otherwise
*/
static int select_try(job_t *j)
{
    fd_set fds;
    int maxfd=-1;

    FD_ZERO(&fds);

    const io_chain_t chain = j->all_io_redirections();
    for (size_t idx = 0; idx < chain.size(); idx++)
    {
        const io_data_t *io = chain.at(idx).get();
        if (io->io_mode == IO_BUFFER)
        {
            CAST_INIT(const io_pipe_t *, io_pipe, io);
            int fd = io_pipe->pipe_fd[0];
//			fwprintf( stderr, L"fd %d on job %ls\n", fd, j->command );
            FD_SET(fd, &fds);
            maxfd = maxi(maxfd, fd);
            debug(3, L"select_try on %d\n", fd);
        }
    }

    if (maxfd >= 0)
    {
        int retval;
        struct timeval tv;

        tv.tv_sec=0;
        tv.tv_usec=10000;

        retval =select(maxfd+1, &fds, 0, 0, &tv);
        return retval > 0;
    }

    return -1;
}

/**
   Read from descriptors until they are empty.

   \param j the job to test
*/
static void read_try(job_t *j)
{
    io_buffer_t *buff = NULL;

    /*
      Find the last buffer, which is the one we want to read from
    */
    const io_chain_t chain = j->all_io_redirections();
    for (size_t idx = 0; idx < chain.size(); idx++)
    {
        io_data_t *d = chain.at(idx).get();
        if (d->io_mode == IO_BUFFER)
        {
            buff = static_cast<io_buffer_t *>(d);
        }
    }

    if (buff)
    {
        debug(3, L"proc::read_try('%ls')\n", j->command_wcstr());
        while (1)
        {
            char b[BUFFER_SIZE];
            long l;

            l=read_blocked(buff->pipe_fd[0],
                           b, BUFFER_SIZE);
            if (l==0)
            {
                break;
            }
            else if (l<0)
            {
                if (errno != EAGAIN)
                {
                    debug(1,
                          _(L"An error occured while reading output from code block"));
                    wperror(L"read_try");
                }
                break;
            }
            else
            {
                buff->out_buffer_append(b, l);
            }
        }
    }
}


/**
   Give ownership of the terminal to the specified job.

   \param j The job to give the terminal to.

   \param cont If this variable is set, we are giving back control to
   a job that has previously been stopped. In that case, we need to
   set the terminal attributes to those saved in the job.
 */
static bool terminal_give_to_job(job_t *j, int cont)
{

    if (tcsetpgrp(0, j->pgid))
    {
        debug(1,
              _(L"Could not send job %d ('%ls') to foreground"),
              j->job_id,
              j->command_wcstr());
        wperror(L"tcsetpgrp");
        return false;
    }

    if (cont)
    {
        if (tcsetattr(0, TCSADRAIN, &j->tmodes))
        {
            debug(1,
                  _(L"Could not send job %d ('%ls') to foreground"),
                  j->job_id,
                  j->command_wcstr());
            wperror(L"tcsetattr");
            return false;
        }
    }
    return true;
}

/**
   Returns control of the terminal to the shell, and saves the terminal
   attribute state to the job, so that we can restore the terminal
   ownership to the job at a later time .
*/
static int terminal_return_from_job(job_t *j)
{

    if (tcsetpgrp(0, getpgrp()))
    {
        debug(1, _(L"Could not return shell to foreground"));
        wperror(L"tcsetpgrp");
        return 0;
    }

    /*
       Save jobs terminal modes.
    */
    if (tcgetattr(0, &j->tmodes))
    {
        debug(1, _(L"Could not return shell to foreground"));
        wperror(L"tcgetattr");
        return 0;
    }

    /* Disabling this per https://github.com/adityagodbole/fish-shell/commit/9d229cd18c3e5c25a8bd37e9ddd3b67ddc2d1b72
       On Linux, 'cd . ; ftp' prevents you from typing into the ftp prompt
       See https://github.com/fish-shell/fish-shell/issues/121
    */
#if 0
    /*
       Restore the shell's terminal modes.
    */
    if (tcsetattr(0, TCSADRAIN, &shell_modes))
    {
        debug(1, _(L"Could not return shell to foreground"));
        wperror(L"tcsetattr");
        return 0;
    }
#endif

    return 1;
}

void job_continue(job_t *j, bool cont)
{
    /*
      Put job first in the job list
    */
    job_promote(j);
    job_set_flag(j, JOB_NOTIFIED, 0);

    CHECK_BLOCK();

    debug(4,
          L"Continue job %d, gid %d (%ls), %ls, %ls",
          j->job_id,
          j->pgid,
          j->command_wcstr(),
          job_is_completed(j)?L"COMPLETED":L"UNCOMPLETED",
          is_interactive?L"INTERACTIVE":L"NON-INTERACTIVE");

    if (!job_is_completed(j))
    {
        if (job_get_flag(j, JOB_TERMINAL) && job_get_flag(j, JOB_FOREGROUND))
        {
            /* Put the job into the foreground. Hack: ensure that stdin is marked as blocking first (#176). */
            make_fd_blocking(STDIN_FILENO);

            signal_block();

            bool ok = terminal_give_to_job(j, cont);

            signal_unblock();

            if (!ok)
                return;
        }

        /*
           Send the job a continue signal, if necessary.
        */
        if (cont)
        {
            process_t *p;

            for (p=j->first_process; p; p=p->next)
                p->stopped=0;

            if (job_get_flag(j, JOB_CONTROL))
            {
                if (killpg(j->pgid, SIGCONT))
                {
                    wperror(L"killpg (SIGCONT)");
                    return;
                }
            }
            else
            {
                for (p=j->first_process; p; p=p->next)
                {
                    if (kill(p->pid, SIGCONT) < 0)
                    {
                        wperror(L"kill (SIGCONT)");
                        return;
                    }
                }
            }
        }

        if (job_get_flag(j, JOB_FOREGROUND))
        {
            int quit = 0;

            /*
               Wait for job to report. Looks a bit ugly because it has to
               handle the possibility that a signal is dispatched while
               running job_is_stopped().
            */
            while (!quit)
            {
                do
                {
                    got_signal = 0;
                    quit = job_is_stopped(j) || job_is_completed(j);
                }
                while (got_signal && !quit);

                if (!quit)
                {

//					debug( 1, L"select_try()" );
                    switch (select_try(j))
                    {
                        case 1:
                        {
                            read_try(j);
                            break;
                        }

                        case -1:
                        {
                            /*
                              If there is no funky IO magic, we can use
                              waitpid instead of handling child deaths
                              through signals. This gives a rather large
                              speed boost (A factor 3 startup time
                              improvement on my 300 MHz machine) on
                              short-lived jobs.
                            */
                            int status;
                            pid_t pid = waitpid(-1, &status, WUNTRACED);
                            if (pid > 0)
                            {
                                handle_child_status(pid, status);
                            }
                            else
                            {
                                /*
                                  This probably means we got a
                                  signal. A signal might mean that the
                                  terminal emulator sent us a hup
                                  signal to tell is to close. If so,
                                  we should exit.
                                */
                                if (reader_exit_forced())
                                {
                                    quit = 1;
                                }

                            }
                            break;
                        }

                    }
                }
            }
        }
    }

    if (job_get_flag(j, JOB_FOREGROUND))
    {

        if (job_is_completed(j))
        {

            // It's possible that the job will produce output and exit before we've even read from it.
            // We'll eventually read the output, but it may be after we've executed subsequent calls
            // This is why my prompt colors kept getting screwed up - the builtin echo calls
            // were sometimes having their output combined with the set_color calls in the wrong order!
            read_try(j);

            process_t *p = j->first_process;
            while (p->next)
                p = p->next;

            if (WIFEXITED(p->status) || WIFSIGNALED(p->status))
            {
                /*
                   Mark process status only if we are in the foreground
                   and the last process in a pipe, and it is not a short circuited builtin
                */
                if (p->pid)
                {
                    int status = proc_format_status(p->status);
                    //wprintf(L"setting status %d for %ls\n", job_get_flag( j, JOB_NEGATE )?!status:status, j->command);
                    proc_set_last_status(job_get_flag(j, JOB_NEGATE)?!status:status);
                }
            }
        }

        /* Put the shell back in the foreground. */
        if (job_get_flag(j, JOB_TERMINAL) && job_get_flag(j, JOB_FOREGROUND))
        {
            int ok;

            signal_block();

            ok = terminal_return_from_job(j);

            signal_unblock();

            if (!ok)
                return;

        }
    }

}

int proc_format_status(int status)
{
    if (WIFSIGNALED(status))
    {
        return 128+WTERMSIG(status);
    }
    else if (WIFEXITED(status))
    {
        return WEXITSTATUS(status);
    }
    return status;

}


void proc_sanity_check()
{
    job_t *j;
    job_t *fg_job=0;

    job_iterator_t jobs;
    while ((j = jobs.next()))
    {
        process_t *p;

        if (!job_get_flag(j, JOB_CONSTRUCTED))
            continue;


        validate_pointer(j->first_process,
                         _(L"Process list pointer"),
                         0);

        /*
          More than one foreground job?
        */
        if (job_get_flag(j, JOB_FOREGROUND) && !(job_is_stopped(j) || job_is_completed(j)))
        {
            if (fg_job != 0)
            {
                debug(0,
                      _(L"More than one job in foreground: job 1: '%ls' job 2: '%ls'"),
                      fg_job->command_wcstr(),
                      j->command_wcstr());
                sanity_lose();
            }
            fg_job = j;
        }

        p = j->first_process;
        while (p)
        {
            validate_pointer(p->get_argv(), _(L"Process argument list"), 0);
            validate_pointer(p->argv0(), _(L"Process name"), 0);
            validate_pointer(p->next, _(L"Process list pointer"), 1);

            if ((p->stopped & (~0x00000001)) != 0)
            {
                debug(0,
                      _(L"Job '%ls', process '%ls' has inconsistent state \'stopped\'=%d"),
                      j->command_wcstr(),
                      p->argv0(),
                      p->stopped);
                sanity_lose();
            }

            if ((p->completed & (~0x00000001)) != 0)
            {
                debug(0,
                      _(L"Job '%ls', process '%ls' has inconsistent state \'completed\'=%d"),
                      j->command_wcstr(),
                      p->argv0(),
                      p->completed);
                sanity_lose();
            }

            p=p->next;
        }

    }
}

void proc_push_interactive(int value)
{
    ASSERT_IS_MAIN_THREAD();
    int old = is_interactive;
    interactive_stack.push_back(is_interactive);
    is_interactive = value;
    if (old != value)
        signal_set_handlers();
}

void proc_pop_interactive()
{
    ASSERT_IS_MAIN_THREAD();
    int old = is_interactive;
    is_interactive= interactive_stack.back();
    interactive_stack.pop_back();
    if (is_interactive != old)
        signal_set_handlers();
}