[deliverable/binutils-gdb.git] / gdb / infrun.c

/* Start and stop the inferior process, for GDB.
   Copyright (C) 1986, 1987, 1988 Free Software Foundation, Inc.

GDB is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY.  No author or distributor accepts responsibility to anyone
for the consequences of using it or for whether it serves any
particular purpose or works at all, unless he says so in writing.
Refer to the GDB General Public License for full details.

Everyone is granted permission to copy, modify and redistribute GDB,
but only under the conditions described in the GDB General Public
License.  A copy of this license is supposed to have been given to you
along with GDB so you can know your rights and responsibilities.  It
should be in a file named COPYING.  Among other things, the copyright
notice and this notice must be preserved on all copies.

In other words, go ahead and share GDB, but don't try to stop
anyone else from sharing it farther.  Help stamp out software hoarding!
*/

#include "defs.h"
#include "initialize.h"
#include "param.h"
#include "symtab.h"
#include "frame.h"
#include "inferior.h"
#include "wait.h"

#include <stdio.h>
#include <signal.h>
#include <a.out.h>
#include <sys/file.h>

#ifdef UMAX_PTRACE
#include <sys/param.h>
#include <sys/ptrace.h>
#endif UMAX_PTRACE

extern char *sys_siglist[];
extern int errno;

/* Tables of how to react to signals; the user sets them.  */

static char signal_stop[NSIG];
static char signal_print[NSIG];
static char signal_program[NSIG];

/* Nonzero if breakpoints are now inserted in the inferior.  */

static int breakpoints_inserted;

/* Function inferior was in as of last step command.  */

static struct symbol *step_start_function;

/* This is the sequence of bytes we insert for a breakpoint.  */

static char break_insn[] = BREAKPOINT;

/* Nonzero => address for special breakpoint for resuming stepping.  */ 

static CORE_ADDR step_resume_break_address;

/* Original contents of the byte where the special breakpoint is.  */

static char step_resume_break_shadow[sizeof break_insn];

/* Nonzero means the special breakpoint is a duplicate
   so it has not itself been inserted.  */

static int step_resume_break_duplicate;

/* Nonzero if we are expecting a trace trap and should proceed from it.
   2 means expecting 2 trace traps and should continue both times.
   That occurs when we tell sh to exec the program: we will get
   a trap after the exec of sh and a second when the program is exec'd.  */

static int trap_expected;

/* Nonzero if the next time we try to continue the inferior, it will
   step one instruction and generate a spurious trace trap.
   This is used to compensate for a bug in HP-UX.  */

static int trap_expected_after_continue;

/* Nonzero means expecting a trace trap
   and should stop the inferior and return silently when it happens.  */

static int stop_after_trap;

/* Nonzero means expecting a trace trap due to attaching to a process.  */

static int stop_after_attach;

/* Nonzero if pc has been changed by the debugger
   since the inferior stopped.  */

int pc_changed;

/* Nonzero if debugging a remote machine via a serial link or ethernet.  */

int remote_debugging;

/* Save register contents here when about to pop a stack dummy frame.  */

char stop_registers[REGISTER_BYTES];

/* Nonzero if program stopped due to error trying to insert breakpoints.  */

static int breakpoints_failed;

/* Nonzero if inferior is in sh before our program got exec'd.  */

static int running_in_shell;

/* Nonzero after stop if current stack frame should be printed.  */

static int stop_print_frame;

static void insert_step_breakpoint ();
static void remove_step_breakpoint ();
static void wait_for_inferior ();
static void normal_stop ();

START_FILE
\f
/* Clear out all variables saying what to do when inferior is continued.
   First do this, then set the ones you want, then call `proceed'.  */

void
clear_proceed_status ()
{
  trap_expected = 0;
  step_range_start = 0;
  step_range_end = 0;
  step_frame = 0;
  step_over_calls = -1;
  step_resume_break_address = 0;
  stop_after_trap = 0;
  stop_after_attach = 0;

  /* Discard any remaining commands left by breakpoint we had stopped at.  */
  clear_breakpoint_commands ();
}

/* Basic routine for continuing the program in various fashions.

   ADDR is the address to resume at, or -1 for resume where stopped.
   SIGNAL is the signal to give it, or 0 for none,
     or -1 for act according to how it stopped.
   STEP is nonzero if should trap after one instruction.
     -1 means return after that and print nothing.
     You should probably set various step_... variables
     before calling here, if you are stepping.

   You should call clear_proceed_status before calling proceed.  */

void
proceed (addr, signal, step)
     CORE_ADDR addr;
     int signal;
     int step;
{
  int oneproc = 0;

  if (step > 0)
    step_start_function = find_pc_function (read_pc ());
  if (step < 0)
    stop_after_trap = 1;

  if (addr == -1)
    {
      /* If there is a breakpoint at the address we will resume at,
         step one instruction before inserting breakpoints
         so that we do not stop right away.  */

      if (!pc_changed && breakpoint_here_p (read_pc ()))
        oneproc = 1;
    }
  else
    write_register (PC_REGNUM, addr);

  if (trap_expected_after_continue)
    {
      /* If (step == 0), a trap will be automatically generated after
         the first instruction is executed.  Force step one
         instruction to clear this condition.  This should not occur
         if step is nonzero, but it is harmless in that case.  */
      oneproc = 1;
      trap_expected_after_continue = 0;
    }

  if (oneproc)
    /* We will get a trace trap after one instruction.
       Continue it automatically and insert breakpoints then.  */
    trap_expected = 1;
  else
    {
      int temp = insert_breakpoints ();
      if (temp)
        {
          print_sys_errmsg ("ptrace", temp);
          error ("Cannot insert breakpoints.\n\
The same program may be running in another process.");
        }
      breakpoints_inserted = 1;
    }

  /* Install inferior's terminal modes.  */
  terminal_inferior ();

  if (signal >= 0)
    stop_signal = signal;
  /* If this signal should not be seen by program,
     give it zero.  Used for debugging signals.  */
  else if (stop_signal < NSIG && !signal_program[stop_signal])
    stop_signal= 0;

  /* Resume inferior.  */
  resume (oneproc || step, stop_signal);

  /* Wait for it to stop (if not standalone)
     and in any case decode why it stopped, and act accordingly.  */

  wait_for_inferior ();
  normal_stop ();
}

/* Writing the inferior pc as a register calls this function
   to inform infrun that the pc has been set in the debugger.  */

writing_pc (val)
     CORE_ADDR val;
{
  stop_pc = val;
  pc_changed = 1;
}

/* Start an inferior process for the first time.
   Actually it was started by the fork that created it,
   but it will have stopped one instruction after execing sh.
   Here we must get it up to actual execution of the real program.  */

start_inferior ()
{
  /* We will get a trace trap after one instruction.
     Continue it automatically.  Eventually (after shell does an exec)
     it will get another trace trap.  Then insert breakpoints and continue.  */
  trap_expected = 2;
  running_in_shell = 0;         /* Set to 1 at first SIGTRAP, 0 at second.  */
  trap_expected_after_continue = 0;
  breakpoints_inserted = 0;
  mark_breakpoints_out ();

  /* Set up the "saved terminal modes" of the inferior
     based on what modes we are starting it with.  */
  terminal_init_inferior ();

  /* Install inferior's terminal modes.  */
  terminal_inferior ();

  if (remote_debugging)
    {
      trap_expected = 0;
      fetch_inferior_registers();
      set_current_frame (read_register(FP_REGNUM));
      stop_frame = get_current_frame();
      inferior_pid = 3;
      if (insert_breakpoints())
        fatal("Can't insert breakpoints");
      breakpoints_inserted = 1;
      proceed(-1, -1, 0);
    }
  else
    {
      wait_for_inferior ();
      normal_stop ();
    }
}

/* Start remote-debugging of a machine over a serial link.  */

void
start_remote ()
{
  clear_proceed_status ();
  running_in_shell = 0;
  trap_expected = 0;
  inferior_pid = 3;
  breakpoints_inserted = 0;
  mark_breakpoints_out ();
  wait_for_inferior ();
  normal_stop();
}

#ifdef ATTACH_DETACH

/* Attach to process PID, then initialize for debugging it
   and wait for the trace-trap that results from attaching.  */

void
attach_program (pid)
     int pid;
{
  attach (pid);
  inferior_pid = pid;

  mark_breakpoints_out ();
  terminal_init_inferior ();
  clear_proceed_status ();
  stop_after_attach = 1;
  /*proceed (-1, 0, -2);*/
  wait_for_inferior ();
  normal_stop ();
}
#endif /* ATTACH_DETACH */
\f
/* Wait for control to return from inferior to debugger.
   If inferior gets a signal, we may decide to start it up again
   instead of returning.  That is why there is a loop in this function.
   When this function actually returns it means the inferior
   should be left stopped and GDB should read more commands.  */

static void
wait_for_inferior ()
{
  register int pid;
  WAITTYPE w;
  CORE_ADDR pc;
  int tem;
  int another_trap;
  int random_signal;
  CORE_ADDR stop_sp;
  int stop_step_resume_break;
  int newmisc;
  int newfun_pc;
  struct symbol *newfun;
  struct symtab_and_line sal;
  int prev_pc;

  prev_pc = read_pc ();

  while (1)
    {
      if (remote_debugging)
        remote_wait (&w);
      else
        {
          pid = wait (&w);
          if (pid != inferior_pid)
            continue;
        }

      pc_changed = 0;
      fetch_inferior_registers ();
      stop_pc = read_pc ();
      set_current_frame (read_register (FP_REGNUM));
      stop_frame = get_current_frame ();
      stop_sp = read_register (SP_REGNUM);
      another_trap = 0;
      stop_breakpoint = 0;
      stop_step = 0;
      stop_stack_dummy = 0;
      stop_print_frame = 1;
      stop_step_resume_break = 0;
      random_signal = 0;
      breakpoints_failed = 0;

      /* Look at the cause of the stop, and decide what to do.
         The alternatives are:
         1) break; to really stop and return to the debugger,
         2) drop through to start up again
           (set another_trap to 1 to single step once)
         3) set random_signal to 1, and the decision between 1 and 2 
           will be made according to the signal handling tables.  */

      if (WIFEXITED (w))
        {
          terminal_ours_for_output ();
          if (WRETCODE (w))
            printf ("\nProgram exited with code 0%o.\n", WRETCODE (w));
          else
            printf ("\nProgram exited normally.\n");
          fflush (stdout);
          inferior_died ();
          stop_print_frame = 0;
          break;
        }
      else if (!WIFSTOPPED (w))
        {
          kill_inferior ();
          stop_print_frame = 0;
          stop_signal = WTERMSIG (w);
          terminal_ours_for_output ();
          printf ("\nProgram terminated with signal %d, %s\n",
                  stop_signal,
                  stop_signal < NSIG
                  ? sys_siglist[stop_signal]
                  : "(undocumented)");
          printf ("The inferior process no longer exists.\n");
          fflush (stdout);
          break;
        }
      else
        {
          stop_signal = WSTOPSIG (w);

          /* First, distinguish signals caused by the debugger from signals
             that have to do with the program's own actions.
             Note that breakpoint insns may cause SIGTRAP or SIGILL
             or SIGEMT, depending on the operating system version.
             Here we detect when a SIGILL or SIGEMT is really a breakpoint
             and change it to SIGTRAP.  */

          if (stop_signal == SIGTRAP
              || (breakpoints_inserted &&
                  (stop_signal == SIGILL
                   || stop_signal == SIGEMT))
              || stop_after_attach)
            {
              if (stop_signal == SIGTRAP && stop_after_trap)
                {
                  stop_print_frame = 0;
                  break;
                }
              if (stop_after_attach)
                break;
              /* Don't even think about breakpoints
                 if still running the shell that will exec the program
                 or if just proceeded over a breakpoint.  */
              if (stop_signal == SIGTRAP && trap_expected)
                stop_breakpoint = 0;
              else
                /* See if there is a breakpoint at the current PC.  */
#if DECR_PC_AFTER_BREAK
                /* Notice the case of stepping through a jump
                   that leads just after a breakpoint.
                   Don't confuse that with hitting the breakpoint.
                   What we check for is that 1) stepping is going on
                   and 2) the pc before the last insn does not match
                   the address of the breakpoint before the current pc.  */
                if (!(prev_pc != stop_pc - DECR_PC_AFTER_BREAK
                      && step_range_end && !step_resume_break_address))
#endif /* DECR_PC_AFTER_BREAK not zero */
                  {
                    select_frame (stop_frame, 0); /* For condition exprs. */
                    stop_breakpoint = breakpoint_stop_status (stop_pc, stop_frame);
                    /* Following in case break condition called a function.  */
                    stop_print_frame = 1;
                    if (stop_breakpoint && DECR_PC_AFTER_BREAK)
                      {
                        stop_pc -= DECR_PC_AFTER_BREAK;
                        write_register (PC_REGNUM, stop_pc);
                        pc_changed = 0;
                      }
                  }
              /* See if we stopped at the special breakpoint for
                 stepping over a subroutine call.  */
              if (stop_pc - DECR_PC_AFTER_BREAK == step_resume_break_address)
                {
                  stop_step_resume_break = 1;
                  if (DECR_PC_AFTER_BREAK)
                    {
                      stop_pc -= DECR_PC_AFTER_BREAK;
                      write_register (PC_REGNUM, stop_pc);
                      pc_changed = 0;
                    }
                }

              if (stop_signal == SIGTRAP)
                random_signal
                  = !(stop_breakpoint || trap_expected
                      || stop_step_resume_break
                      || (stop_sp INNER_THAN stop_pc && stop_pc INNER_THAN stop_frame)
                      || (step_range_end && !step_resume_break_address));
              else
                {
                  random_signal
                    = !(stop_breakpoint || stop_step_resume_break);
                  if (!random_signal)
                    stop_signal = SIGTRAP;
                }
            }
          else
            random_signal = 1;

          /* For the program's own signals, act according to
             the signal handling tables.  */

          if (random_signal
              && !(running_in_shell && stop_signal == SIGSEGV))
            {
              /* Signal not for debugging purposes.  */
              int printed = 0;

              if (stop_signal >= NSIG
                  || signal_print[stop_signal])
                {
                  printed = 1;
                  terminal_ours_for_output ();
                  printf ("\nProgram received signal %d, %s\n",
                          stop_signal,
                          stop_signal < NSIG
                           ? sys_siglist[stop_signal]
                           : "(undocumented)");
                  fflush (stdout);
                }
              if (stop_signal >= NSIG
                  || signal_stop[stop_signal])
                break;
              /* If not going to stop, give terminal back
                 if we took it away.  */
              else if (printed)
                terminal_inferior ();
            }

          /* Handle cases caused by hitting a breakpoint.  */

          if (!random_signal
              && (stop_breakpoint || stop_step_resume_break))
            {
              /* Does a breakpoint want us to stop?  */
              if (stop_breakpoint && stop_breakpoint != -1)
                {
                  /* 0x1000000 is set in stop_breakpoint as returned by
                     breakpoint_status_p to indicate a silent breakpoint.  */
                  if (stop_breakpoint > 0 && stop_breakpoint & 0x1000000)
                    {
                      stop_breakpoint &= ~0x1000000;
                      stop_print_frame = 0;
                    }
                  break;
                }
              /* But if we have hit the step-resumption breakpoint,
                 remove it.  It has done its job getting us here.  */
              if (stop_step_resume_break
                  && (step_frame == 0 || stop_frame == step_frame))
                {
                  remove_step_breakpoint ();
                  step_resume_break_address = 0;
                }
              /* Otherwise, must remove breakpoints and single-step
                 to get us past the one we hit.  */
              else
                {
                  remove_breakpoints ();
                  remove_step_breakpoint ();
                  breakpoints_inserted = 0;
                  another_trap = 1;
                }

              /* We come here if we hit a breakpoint but should not
                 stop for it.  Possibly we also were stepping
                 and should stop for that.  So fall through and
                 test for stepping.  But, if not stepping,
                 do not stop.  */
            }

          /* If this is the breakpoint at the end of a stack dummy,
             just stop silently.  */
          if (stop_sp INNER_THAN stop_pc && stop_pc INNER_THAN stop_frame)
            {
              stop_print_frame = 0;
              stop_stack_dummy = 1;
#ifdef HP9K320
              trap_expected_after_continue = 1;
#endif
              break;
            }

          if (step_resume_break_address)
            /* Having a step-resume breakpoint overrides anything
               else having to do with stepping commands until
               that breakpoint is reached.  */
            ;
          /* If stepping through a line, keep going if still within it.  */
          else if (!random_signal
                   && step_range_end
                   && stop_pc >= step_range_start
                   && stop_pc < step_range_end)
            {
              /* Don't step through the return from a function
                 unless that is the first instruction stepped through.  */
              if (ABOUT_TO_RETURN (stop_pc))
                {
                  stop_step = 1;
                  break;
                }
            }

          /* We stepped out of the stepping range.  See if that was due
             to a subroutine call that we should proceed to the end of.  */
          else if (!random_signal && step_range_end)
            {
              newfun = find_pc_function (stop_pc);
              newmisc = -1;
              if (newfun)
                {
                  newfun_pc = BLOCK_START (SYMBOL_BLOCK_VALUE (newfun))
                    + FUNCTION_START_OFFSET;
                }
              else
                {
                  newmisc = find_pc_misc_function (stop_pc);
                  if (newmisc >= 0)
                    newfun_pc = misc_function_vector[newmisc].address
                      + FUNCTION_START_OFFSET;
                  else newfun_pc = 0;
                }
              if (stop_pc == newfun_pc
                  && (step_over_calls > 0 || (step_over_calls && newfun == 0)))
                {
                  /* A subroutine call has happened.  */
                  /* Set a special breakpoint after the return */
                  step_resume_break_address = SAVED_PC_AFTER_CALL (stop_frame);
                  step_resume_break_duplicate
                    = breakpoint_here_p (step_resume_break_address);
                  if (breakpoints_inserted)
                    insert_step_breakpoint ();
                }
              /* Subroutine call with source code we should not step over.
                 Do step to the first line of code in it.  */
              else if (stop_pc == newfun_pc && step_over_calls)
                {
                  SKIP_PROLOGUE (newfun_pc);
                  sal = find_pc_line (newfun_pc, 0);
                  /* Use the step_resume_break to step until
                     the end of the prologue, even if that involves jumps
                     (as it seems to on the vax under 4.2).  */
                  /* If the prologue ends in the middle of a source line,
                     continue to the end of that source line.
                     Otherwise, just go to end of prologue.  */
                  if (sal.end && sal.pc != newfun_pc)
                    newfun_pc = sal.end;

                  if (newfun_pc == stop_pc)
                    /* We are already there: stop now.  */
                    stop_step = 1;
                  else
                    /* Put the step-breakpoint there and go until there.  */
                    {
                      step_resume_break_address = newfun_pc;

                      step_resume_break_duplicate
                        = breakpoint_here_p (step_resume_break_address);
                      if (breakpoints_inserted)
                        insert_step_breakpoint ();
                      /* Do not specify what the fp should be when we stop
                         since on some machines the prologue
                         is where the new fp value is established.  */
                      step_frame = 0;
                      /* And make sure stepping stops right away then.  */
                      step_range_end = step_range_start;
                    }
                }
              /* No subroutince call; stop now.  */
              else
                {
                  stop_step = 1;
                  break;
                }
            }
        }

      /* Save the pc before execution, to compare with pc after stop.  */
      prev_pc = read_pc ();

      /* If we did not do break;, it means we should keep
         running the inferior and not return to debugger.  */

      /* If trap_expected is 2, it means continue once more
         and insert breakpoints at the next trap.
         If trap_expected is 1 and the signal was SIGSEGV, it means
         the shell is doing some memory allocation--just resume it
         with SIGSEGV.
         Otherwise insert breakpoints now, and possibly single step.  */

      if (trap_expected > 1)
        {
          trap_expected--;
          running_in_shell = 1;
          resume (0, 0);
        }
      else if (running_in_shell && stop_signal == SIGSEGV)
        {
          resume (0, SIGSEGV);
        }
      else
        {
          /* Here, we are not awaiting another exec to get
             the program we really want to debug.
             Insert breakpoints now, unless we are trying
             to one-proceed past a breakpoint.  */
          running_in_shell = 0;
          if (!breakpoints_inserted && !another_trap)
            {
              insert_step_breakpoint ();
              breakpoints_failed = insert_breakpoints ();
              if (breakpoints_failed)
                break;
              breakpoints_inserted = 1;
            }

          trap_expected = another_trap;

          if (stop_signal == SIGTRAP)
            stop_signal = 0;

          resume ((step_range_end && !step_resume_break_address)
                  || trap_expected,
                  stop_signal);
        }
    }
}
\f
/* Here to return control to GDB when the inferior stops for real.
   Print appropriate messages, remove breakpoints, give terminal our modes.

   RUNNING_IN_SHELL nonzero means the shell got a signal before
   exec'ing the program we wanted to run.
   STOP_PRINT_FRAME nonzero means print the executing frame
   (pc, function, args, file, line number and line text).
   BREAKPOINTS_FAILED nonzero means stop was due to error
   attempting to insert breakpoints.  */

static void
normal_stop ()
{
  if (breakpoints_failed)
    {
      terminal_ours_for_output ();
      print_sys_errmsg ("ptrace", breakpoints_failed);
      printf ("Stopped; cannot insert breakpoints.\n\
The same program may be running in another process.\n");
    }

  if (inferior_pid)
    remove_step_breakpoint ();

  if (inferior_pid && breakpoints_inserted)
    if (remove_breakpoints ())
      {
        terminal_ours_for_output ();
        printf ("Cannot remove breakpoints because program is no longer writable.\n\
It must be running in another process.\n\
Further execution is probably impossible.\n");
      }

  breakpoints_inserted = 0;

  /* Delete the breakpoint we stopped at, if it wants to be deleted.
     Delete any breakpoint that is to be deleted at the next stop.  */

  breakpoint_auto_delete (stop_breakpoint);

  /* If an auto-display called a function and that got a signal,
     delete that auto-display to avoid an infinite recursion.  */

  delete_current_display ();

  if (step_multi && stop_step)
    return;

  terminal_ours ();

  if (running_in_shell)
    {
      if (stop_signal == SIGSEGV)
        {
          char *exec_file = (char *) get_exec_file (1);

          if (access (exec_file, X_OK) != 0)
            printf ("The file \"%s\" is not executable.\n", exec_file);
          else
            printf ("\
You have just encountered a bug in \"sh\".  GDB starts your program\n\
by running \"sh\" with a command to exec your program.\n\
This is so that \"sh\" will process wildcards and I/O redirection.\n\
This time, \"sh\" crashed.\n\
\n\
One known bug in \"sh\" bites when the environment takes up a lot of space.\n\
Try \"info env\" to see the environment; then use \"unset-env\" to kill\n\
some variables whose values are large; then do \"run\" again.\n\
\n\
If that works, you might want to put those \"unset-env\" commands\n\
into a \".gdbinit\" file in this directory so they will happen every time.\n");
        }
      /* Don't confuse user with his program's symbols on sh's data.  */
      stop_print_frame = 0;
    }

  if (inferior_pid == 0)
    return;

  /* Select innermost stack frame except on return from a stack dummy routine,
     or if the program has exited.  */
  if (!stop_stack_dummy)
    {
      select_frame (stop_frame, 0);

      if (stop_print_frame)
        {
          if (stop_breakpoint > 0)
            printf ("\nBpt %d, ", stop_breakpoint);
          print_sel_frame (stop_step
                           && step_frame == stop_frame
                           && step_start_function == find_pc_function (stop_pc));
          /* Display the auto-display expressions.  */
          do_displays ();
        }
    }

  /* Save the function value return registers
     We might be about to restore their previous contents.  */
  read_register_bytes (0, stop_registers, REGISTER_BYTES);

  if (stop_stack_dummy)
    {
      /* Pop the empty frame that contains the stack dummy.  */
      POP_FRAME;
      select_frame (read_register (FP_REGNUM), 0);
    }
}
\f
static void
insert_step_breakpoint ()
{
  if (step_resume_break_address && !step_resume_break_duplicate)
    {
      read_memory (step_resume_break_address,
                   step_resume_break_shadow, sizeof break_insn);
      write_memory (step_resume_break_address,
                    break_insn, sizeof break_insn);
    }
}

static void
remove_step_breakpoint ()
{
  if (step_resume_break_address && !step_resume_break_duplicate)
    write_memory (step_resume_break_address, step_resume_break_shadow,
                  sizeof break_insn);
}
\f
/* Specify how various signals in the inferior should be handled.  */

static void
handle_command (args, from_tty)
     char *args;
     int from_tty;
{
  register char *p = args;
  int signum;
  register int digits, wordlen;

  if (!args)
    error_no_arg ("signal to handle");

  while (*p)
    {
      /* Find the end of the next word in the args.  */
      for (wordlen = 0; p[wordlen] && p[wordlen] != ' ' && p[wordlen] != '\t';
           wordlen++);
      for (digits = 0; p[digits] >= '0' && p[digits] <= '9'; digits++);

      /* If it is all digits, it is signal number to operate on.  */
      if (digits == wordlen)
        {
          signum = atoi (p);
          if (signum == SIGTRAP || signum == SIGINT)
            {
              if (!query ("Signal %d is used by the debugger.\nAre you sure you want to change it? ", signum))
                error ("Not confirmed.");
            }
        }
      else if (signum == 0)
        error ("First argument is not a signal number.");

      /* Else, if already got a signal number, look for flag words
         saying what to do for it.  */
      else if (!strncmp (p, "stop", wordlen))
        {
          signal_stop[signum] = 1;
          signal_print[signum] = 1;
        }
      else if (wordlen >= 2 && !strncmp (p, "print", wordlen))
        signal_print[signum] = 1;
      else if (wordlen >= 2 && !strncmp (p, "pass", wordlen))
        signal_program[signum] = 1;
      else if (!strncmp (p, "ignore", wordlen))
        signal_program[signum] = 0;
      else if (wordlen >= 3 && !strncmp (p, "nostop", wordlen))
        signal_stop[signum] = 0;
      else if (wordlen >= 4 && !strncmp (p, "noprint", wordlen))
        {
          signal_print[signum] = 0;
          signal_stop[signum] = 0;
        }
      else if (wordlen >= 4 && !strncmp (p, "nopass", wordlen))
        signal_program[signum] = 0;
      else if (wordlen >= 3 && !strncmp (p, "noignore", wordlen))
        signal_program[signum] = 1;
      /* Not a number and not a recognized flag word => complain.  */
      else
        {
          p[wordlen] = 0;
          error ("Unrecognized flag word: \"%s\".", p);
        }

      /* Find start of next word.  */
      p += wordlen;
      while (*p == ' ' || *p == '\t') p++;
    }

  if (from_tty)
    {
      /* Show the results.  */
      printf ("Number\tStop\tPrint\tPass to program\tDescription\n");
      printf ("%d\t", signum);
      printf ("%s\t", signal_stop[signum] ? "Yes" : "No");
      printf ("%s\t", signal_print[signum] ? "Yes" : "No");
      printf ("%s\t\t", signal_program[signum] ? "Yes" : "No");
      printf ("%s\n", sys_siglist[signum]);
    }
}

/* Print current contents of the tables set by the handle command.  */

static void
signals_info (signum_exp)
     char *signum_exp;
{
  register int i;
  printf ("Number\tStop\tPrint\tPass to program\tDescription\n");

  if (signum_exp)
    {
      i = parse_and_eval_address (signum_exp);
      printf ("%d\t", i);
      printf ("%s\t", signal_stop[i] ? "Yes" : "No");
      printf ("%s\t", signal_print[i] ? "Yes" : "No");
      printf ("%s\t\t", signal_program[i] ? "Yes" : "No");
      printf ("%s\n", sys_siglist[i]);
      return;
    }

  printf ("\n");
  for (i = 0; i < NSIG; i++)
    {
      QUIT;
      if (i > 0 && i % 16 == 0)
        {
          printf ("[Type Return to see more]");
          fflush (stdout);
          read_line ();
        }
      printf ("%d\t", i);
      printf ("%s\t", signal_stop[i] ? "Yes" : "No");
      printf ("%s\t", signal_print[i] ? "Yes" : "No");
      printf ("%s\t\t", signal_program[i] ? "Yes" : "No");
      printf ("%s\n", sys_siglist[i]);
    }

  printf ("\nUse the \"handle\" command to change these tables.\n");
}
\f
static
initialize ()
{
  register int i;

  add_info ("signals", signals_info,
            "What debugger does when program gets various signals.\n\
Specify a signal number as argument to print info on that signal only.");

  add_com ("handle", class_run, handle_command,
           "Specify how to handle a signal.\n\
Args are signal number followed by flags.\n\
Flags allowed are \"stop\", \"print\", \"pass\",\n\
 \"nostop\", \"noprint\" or \"nopass\".\n\
Print means print a message if this signal happens.\n\
Stop means reenter debugger if this signal happens (implies print).\n\
Pass means let program see this signal; otherwise program doesn't know.\n\
Pass and Stop may be combined.");

  for (i = 0; i < NSIG; i++)
    {
      signal_stop[i] = 1;
      signal_print[i] = 1;
      signal_program[i] = 1;
    }

  /* Signals caused by debugger's own actions
     should not be given to the program afterwards.  */
  signal_program[SIGTRAP] = 0;
  signal_program[SIGINT] = 0;

  /* Signals that are not errors should not normally enter the debugger.  */
#ifdef SIGALRM
  signal_stop[SIGALRM] = 0;
  signal_print[SIGALRM] = 0;
#endif /* SIGALRM */
#ifdef SIGVTALRM
  signal_stop[SIGVTALRM] = 0;
  signal_print[SIGVTALRM] = 0;
#endif /* SIGVTALRM */
#ifdef SIGPROF
  signal_stop[SIGPROF] = 0;
  signal_print[SIGPROF] = 0;
#endif /* SIGPROF */
#ifdef SIGCHLD
  signal_stop[SIGCHLD] = 0;
  signal_print[SIGCHLD] = 0;
#endif /* SIGCHLD */
#ifdef SIGCLD
  signal_stop[SIGCLD] = 0;
  signal_print[SIGCLD] = 0;
#endif /* SIGCLD */
#ifdef SIGIO
  signal_stop[SIGIO] = 0;
  signal_print[SIGIO] = 0;
#endif /* SIGIO */
#ifdef SIGURG
  signal_stop[SIGURG] = 0;
  signal_print[SIGURG] = 0;
#endif /* SIGURG */
}

END_FILE