/****************************************************************************
 *                                                                          *
 *                         GNAT COMPILER COMPONENTS                         *
 *                                                                          *
 *                                 I N I T                                  *
 *                                                                          *
 *                            $Revision: 1.7 $
 *                                                                          *
 *                          C Implementation File                           *
 *                                                                          *
 *          Copyright (C) 1992-2001 Free Software Foundation, Inc.          *
 *                                                                          *
 * GNAT is free software;  you can  redistribute it  and/or modify it under *
 * terms of the  GNU General Public License as published  by the Free Soft- *
 * ware  Foundation;  either version 2,  or (at your option) any later ver- *
 * sion.  GNAT is distributed in the hope that it will be useful, but WITH- *
 * OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY *
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License *
 * for  more details.  You should have  received  a copy of the GNU General *
 * Public License  distributed with GNAT;  see file COPYING.  If not, write *
 * to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, *
 * MA 02111-1307, USA.                                                      *
 *                                                                          *
 * As a  special  exception,  if you  link  this file  with other  files to *
 * produce an executable,  this file does not by itself cause the resulting *
 * executable to be covered by the GNU General Public License. This except- *
 * ion does not  however invalidate  any other reasons  why the  executable *
 * file might be covered by the  GNU Public License.                        *
 *                                                                          *
 * GNAT was originally developed  by the GNAT team at  New York University. *
 * It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). *
 *                                                                          *
 ****************************************************************************/

/*  This unit contains initialization circuits that are system dependent. A
    major part of the functionality involved involves stack overflow checking.
    The GCC backend generates probe instructions to test for stack overflow.
    For details on the exact approach used to generate these probes, see the
    "Using and Porting GCC" manual, in particular the "Stack Checking" section
    and the subsection "Specifying How Stack Checking is Done". The handlers
    installed by this file are used to handle resulting signals that come
    from these probes failing (i.e. touching protected pages) */

/* The following include is here to meet the published VxWorks requirement
   that the __vxworks header appear before any other include. */
#ifdef __vxworks
#include "vxWorks.h"
#endif

#ifdef IN_RTS
#include "tconfig.h"
#include "tsystem.h"
#include <sys/stat.h>
#else
#include "config.h"
#include "system.h"
#endif

#include "adaint.h"
#include "raise.h"

extern void __gnat_raise_program_error (const char *, int);

/* Addresses of exception data blocks for predefined exceptions. */
extern struct Exception_Data constraint_error;
extern struct Exception_Data numeric_error;
extern struct Exception_Data program_error;
extern struct Exception_Data storage_error;
extern struct Exception_Data tasking_error;
extern struct Exception_Data _abort_signal;

#define Lock_Task system__soft_links__lock_task
extern void (*Lock_Task) PARAMS ((void));

#define Unlock_Task system__soft_links__unlock_task
extern void (*Unlock_Task) PARAMS ((void));

#define Get_Machine_State_Addr \
                      system__soft_links__get_machine_state_addr
extern struct Machine_State *(*Get_Machine_State_Addr) PARAMS ((void));

#define Check_Abort_Status     \
                      system__soft_links__check_abort_status
extern int    (*Check_Abort_Status) PARAMS ((void));

#define Raise_From_Signal_Handler \
                      ada__exceptions__raise_from_signal_handler
extern void   Raise_From_Signal_Handler PARAMS ((struct Exception_Data *,
						const char *));

#define Propagate_Signal_Exception \
                      __gnat_propagate_sig_exc
extern void   Propagate_Signal_Exception
	PARAMS ((struct Machine_State *, struct Exception_Data *, const char *));

/* Copies of global values computed by the binder */
int  __gl_main_priority            = -1;
int  __gl_time_slice_val           = -1;
char __gl_wc_encoding              = 'n';
char __gl_locking_policy           = ' ';
char __gl_queuing_policy           = ' ';
char __gl_task_dispatching_policy  = ' ';
int  __gl_unreserve_all_interrupts = 0;
int  __gl_exception_tracebacks     = 0;

/* Indication of whether synchronous signal handler has already been 
   installed by a previous call to adainit */
int  __gnat_handler_installed      = 0;

/* HAVE_GNAT_INIT_FLOAT must be set on every targets where a __gnat_init_float
   is defined. If this is not set them a void implementation will be defined
   at the end of this unit. */
#undef HAVE_GNAT_INIT_FLOAT

/**********************/
/* __gnat_set_globals */
/**********************/

/* This routine is called from the binder generated main program.  It copies
   the values for global quantities computed by the binder into the following
   global locations. The reason that we go through this copy, rather than just
   define the global locations in the binder generated file, is that they are
   referenced from the runtime, which may be in a shared library, and the
   binder file is not in the shared library. Global references across library
   boundaries like this are not handled correctly in all systems.  */

void
__gnat_set_globals (main_priority, time_slice_val, wc_encoding, locking_policy,
		    queuing_policy, task_dispatching_policy, adafinal_ptr,
		    unreserve_all_interrupts, exception_tracebacks)
     int main_priority;
     int time_slice_val;
     int wc_encoding;
     int locking_policy, queuing_policy, task_dispatching_policy;
     void (*adafinal_ptr) PARAMS ((void)) ATTRIBUTE_UNUSED;
     int unreserve_all_interrupts, exception_tracebacks;
{
  static int already_called = 0;

  /* If this procedure has been already called once, check that the
     arguments in this call are consistent with the ones in the previous
     calls. Otherwise, raise a Program_Error exception.

     We do not check for consistency of the wide character encoding
     method. This default affects only Wide_Text_IO where no explicit
     coding method is given, and there is no particular reason to let
     this default be affected by the source representation of a library
     in any case. 

     The value of main_priority is meaningful only when we are invoked
     from the main program elaboration routine of an Ada application.
     Checking the consistency of this parameter should therefore not be
     done. Since it is assured that the main program elaboration will
     always invoke this procedure before any library elaboration
     routine, only the value of main_priority during the first call
     should be taken into account and all the subsequent ones should be
     ignored. Note that the case where the main program is not written
     in Ada is also properly handled, since the default value will then
     be used for this parameter.

     For identical reasons, the consistency of time_slice_val should not
     be checked. */

  if (already_called)
    {
      if (__gl_locking_policy           != locking_policy ||
          __gl_queuing_policy           != queuing_policy ||
          __gl_task_dispatching_policy  != task_dispatching_policy ||
          __gl_unreserve_all_interrupts != unreserve_all_interrupts ||
          __gl_exception_tracebacks     != exception_tracebacks)
        {
	  __gnat_raise_program_error (__FILE__, __LINE__);
	}
      return;
    }
  already_called = 1;

  __gl_main_priority            = main_priority;
  __gl_time_slice_val           = time_slice_val;
  __gl_wc_encoding              = wc_encoding;
  __gl_locking_policy           = locking_policy;
  __gl_queuing_policy           = queuing_policy;
  __gl_task_dispatching_policy  = task_dispatching_policy;
  __gl_unreserve_all_interrupts = unreserve_all_interrupts;
  __gl_exception_tracebacks     = exception_tracebacks;
}

/*********************/
/* __gnat_initialize */
/*********************/

/* __gnat_initialize is called at the start of execution of an Ada program
   (the call is generated by the binder). The standard routine does nothing
   at all; the intention is that this be replaced by system specific
   code where initialization is required. */

/***********************************/
/* __gnat_initialize (AIX version) */
/***********************************/

#if defined (_AIX)

/* AiX doesn't have SA_NODEFER */

#define SA_NODEFER 0

#include <sys/time.h>

/* AiX doesn't have nanosleep, but provides nsleep instead */

extern int nanosleep PARAMS ((struct timestruc_t *, struct timestruc_t *));
static void __gnat_error_handler PARAMS ((int));

int
nanosleep (Rqtp, Rmtp)
     struct timestruc_t *Rqtp, *Rmtp;
{
  return nsleep (Rqtp, Rmtp);
}

#include <signal.h>

static void
__gnat_error_handler (sig)
     int sig;
{
  struct Exception_Data *exception;
  const char *msg;

  switch (sig)
    {
    case SIGSEGV:
      /* FIXME: we need to detect the case of a *real* SIGSEGV */
      exception = &storage_error;
      msg = "stack overflow or erroneous memory access";
      break;

    case SIGBUS:
      exception = &constraint_error;
      msg = "SIGBUS";
      break;

    case SIGFPE:
      exception = &constraint_error;
      msg = "SIGFPE";
      break;

    default:
      exception = &program_error;
      msg = "unhandled signal";
    }

  Raise_From_Signal_Handler (exception, msg);
}

void
__gnat_install_handler ()
{
  struct sigaction act;

  /* Set up signal handler to map synchronous signals to appropriate
     exceptions.  Make sure that the handler isn't interrupted by another
     signal that might cause a scheduling event! */

  act.sa_handler = __gnat_error_handler;
  act.sa_flags = SA_NODEFER | SA_RESTART;
  (void) sigemptyset (&act.sa_mask);

  (void) sigaction (SIGABRT, &act, NULL);
  (void) sigaction (SIGFPE,  &act, NULL);

  if (__gl_unreserve_all_interrupts == 0) 
    {
      (void) sigaction (SIGILL,  &act, NULL);
      (void) sigaction (SIGSEGV, &act, NULL);
      (void) sigaction (SIGBUS,  &act, NULL);
    }
  __gnat_handler_installed = 1;
}

void
__gnat_initialize ()
{
}

/****************************************/
/* __gnat_initialize (Dec Unix version) */
/****************************************/

#elif defined(__alpha__) && defined(__osf__) && ! defined(__alpha_vxworks)

/* Note: it seems that __osf__ is defined for the Alpha VXWorks case. Not
   clear that this is reasonable, but in any case we have to be sure to
   exclude this case in the above test.  */

#include <signal.h>
#include <sys/siginfo.h>

static void __gnat_error_handler PARAMS ((int, siginfo_t *,
					  struct sigcontext *));
extern char *__gnat_get_code_loc PARAMS ((struct sigcontext *));
extern void __gnat_enter_handler PARAMS ((struct sigcontext *, char *));
extern size_t __gnat_machine_state_length PARAMS ((void));

extern long exc_lookup_gp PARAMS ((char *));
extern void exc_resume PARAMS ((struct sigcontext *));

static void
__gnat_error_handler (sig, sip, context)
     int sig;
     siginfo_t *sip;
     struct sigcontext *context;
{
  struct Exception_Data *exception;
  static int recurse = 0;
  struct sigcontext *mstate;
  const char *msg;

  /* If this was an explicit signal from a "kill", just resignal it.  */
  if (SI_FROMUSER (sip))
    {
      signal (sig, SIG_DFL);
      kill (getpid(), sig);
    }

  /* Otherwise, treat it as something we handle.  */
  switch (sig)
    {
    case SIGSEGV:
      /* If the problem was permissions, this is a constraint error.
	 Likewise if the failing address isn't maximally aligned or if
	 we've recursed.

	 ??? Using a static variable here isn't task-safe, but it's
	 much too hard to do anything else and we're just determining
	 which exception to raise.  */
      if (sip->si_code == SEGV_ACCERR
	  || (((long) sip->si_addr) & 3) != 0
	  || recurse)
	{
	  exception = &constraint_error;
	  msg = "SIGSEGV";
	}
      else
	{
	  /* See if the page before the faulting page is accessible.  Do that
	     by trying to access it.  We'd like to simply try to access
	     4096 + the faulting address, but it's not guaranteed to be
	     the actual address, just to be on the same page.  */
	  recurse++;
	  ((volatile char *)
	   ((long) sip->si_addr & - getpagesize ()))[getpagesize ()];
	  msg = "stack overflow (or erroneous memory access)";
	  exception = &storage_error;
	}
      break;

    case SIGBUS:
      exception = &program_error;
      msg = "SIGBUS";
      break;

    case SIGFPE:
      exception = &constraint_error;
      msg = "SIGFPE";
      break;

    default:
      exception = &program_error;
      msg = "unhandled signal";
    }

  recurse = 0;
  mstate = (struct sigcontext *) (*Get_Machine_State_Addr) ();
  if (mstate != 0)
    *mstate = *context;

  Raise_From_Signal_Handler (exception, (char *) msg);
}

void
__gnat_install_handler ()
{
  struct sigaction act;

  /* Setup signal handler to map synchronous signals to appropriate
     exceptions. Make sure that the handler isn't interrupted by another
     signal that might cause a scheduling event! */

  act.sa_handler = (void (*) PARAMS ((int))) __gnat_error_handler;
  act.sa_flags = SA_ONSTACK | SA_RESTART | SA_NODEFER | SA_SIGINFO;
  (void) sigemptyset (&act.sa_mask);

  (void) sigaction (SIGABRT, &act, NULL);
  (void) sigaction (SIGFPE,  &act, NULL);

  if (__gl_unreserve_all_interrupts == 0)
    {
      (void) sigaction (SIGILL,  &act, NULL);
      (void) sigaction (SIGSEGV, &act, NULL);
      (void) sigaction (SIGBUS,  &act, NULL);
    }

  __gnat_handler_installed = 1;
}

void
__gnat_initialize ()
{
}

/* Routines called by 5amastop.adb.  */

#define SC_GP 29

char *
__gnat_get_code_loc (context)
     struct sigcontext *context;
{
  return (char *) context->sc_pc;
}

void
__gnat_enter_handler (context, pc)
     struct sigcontext *context;
     char *pc;
{
  context->sc_pc = (long) pc;
  context->sc_regs[SC_GP] = exc_lookup_gp (pc);
  exc_resume (context);
}

size_t
__gnat_machine_state_length ()
{
  return sizeof (struct sigcontext);
}

/***********************************/
/* __gnat_initialize (HPUX version) */
/***********************************/

#elif defined (hpux)

#include <signal.h>

static void __gnat_error_handler PARAMS ((int));

static void
__gnat_error_handler (sig)
     int sig;
{
  struct Exception_Data *exception;
  char *msg;

  switch (sig)
    {
    case SIGSEGV:
      /* FIXME: we need to detect the case of a *real* SIGSEGV */
      exception = &storage_error;
      msg = "stack overflow or erroneous memory access";
      break;

    case SIGBUS:
      exception = &constraint_error;
      msg = "SIGBUS";
      break;

    case SIGFPE:
      exception = &constraint_error;
      msg = "SIGFPE";
      break;

    default:
      exception = &program_error;
      msg = "unhandled signal";
    }

  Raise_From_Signal_Handler (exception, msg);
}

void
__gnat_install_handler ()
{
  struct sigaction act;

  /* Set up signal handler to map synchronous signals to appropriate
     exceptions.  Make sure that the handler isn't interrupted by another
     signal that might cause a scheduling event! Also setup an alternate
     stack region for the handler execution so that stack overflows can be
     handled properly, avoiding a SEGV generation from stack usage by the
     handler itself. */

  static char handler_stack [SIGSTKSZ];

  stack_t stack;

  stack.ss_sp    = handler_stack;
  stack.ss_size  = SIGSTKSZ;
  stack.ss_flags = 0;

  (void) sigaltstack (&stack, NULL);

  act.sa_handler = __gnat_error_handler;
  act.sa_flags = SA_NODEFER | SA_RESTART | SA_ONSTACK;
  (void) sigemptyset (&act.sa_mask);

  (void) sigaction (SIGABRT, &act, NULL);
  (void) sigaction (SIGFPE,  &act, NULL);

  if (__gl_unreserve_all_interrupts == 0)
    {
      (void) sigaction (SIGILL,  &act, NULL);
      (void) sigaction (SIGSEGV, &act, NULL);
      (void) sigaction (SIGBUS,  &act, NULL);
    }
  __gnat_handler_installed = 1;
}

void
__gnat_initialize ()
{
}

/*************************************/
/* __gnat_initialize (GNU/Linux version) */
/*************************************/

#elif defined (linux) && defined (i386) && !defined (__RT__)

#include <signal.h>
#include <asm/sigcontext.h>

/* GNU/Linux, which uses glibc, does not define NULL in included
   header files */

#if !defined (NULL)
#define NULL ((void *) 0)
#endif

struct Machine_State
{
  unsigned long eip;
  unsigned long ebx;
  unsigned long esp;
  unsigned long ebp;
  unsigned long esi;
  unsigned long edi;
};

static void __gnat_error_handler PARAMS ((int));

static void
__gnat_error_handler (sig)
     int sig;
{
  struct Exception_Data *exception;
  const char *msg;
  static int recurse = 0;

  struct sigcontext *info
    = (struct sigcontext *) (((char *) &sig) + sizeof (int));

  /* The Linux kernel does not document how to get the machine state in a
     signal handler, but in fact the necessary data is in a sigcontext_struct
     value that is on the stack immediately above the signal number
     parameter, and the above messing accesses this value on the stack. */

  struct Machine_State *mstate;

  switch (sig)
    {
    case SIGSEGV:
      /* If the problem was permissions, this is a constraint error.
       Likewise if the failing address isn't maximally aligned or if
       we've recursed.

       ??? Using a static variable here isn't task-safe, but it's
       much too hard to do anything else and we're just determining
       which exception to raise.  */
      if (recurse)
      {
        exception = &constraint_error;
        msg = "SIGSEGV";
      }
      else
      {
        /* Here we would like a discrimination test to see whether the
           page before the faulting address is accessible. Unfortunately
           Linux seems to have no way of giving us the faulting address.

           In versions of a-init.c before 1.95, we had a test of the page
           before the stack pointer using:

            recurse++;
             ((volatile char *)
              ((long) info->esp_at_signal & - getpagesize ()))[getpagesize ()];

           but that's wrong, since it tests the stack pointer location, and
           the current stack probe code does not move the stack pointer
           until all probes succeed.

           For now we simply do not attempt any discrimination at all. Note
           that this is quite acceptable, since a "real" SIGSEGV can only
           occur as the result of an erroneous program */

        msg = "stack overflow (or erroneous memory access)";
        exception = &storage_error;
      }
      break;

    case SIGBUS:
      exception = &constraint_error;
      msg = "SIGBUS";
      break;

    case SIGFPE:
      exception = &constraint_error;
      msg = "SIGFPE";
      break;

    default:
      exception = &program_error;
      msg = "unhandled signal";
    }

  mstate = (*Get_Machine_State_Addr)();
  if (mstate)
    {
      mstate->eip = info->eip;
      mstate->ebx = info->ebx;
      mstate->esp = info->esp_at_signal;
      mstate->ebp = info->ebp;
      mstate->esi = info->esi;
      mstate->edi = info->edi;
    }

  recurse = 0;
  Raise_From_Signal_Handler (exception, msg);
}

void
__gnat_install_handler ()
{
  struct sigaction act;

  /* Set up signal handler to map synchronous signals to appropriate
     exceptions.  Make sure that the handler isn't interrupted by another
     signal that might cause a scheduling event! */

  act.sa_handler = __gnat_error_handler;
  act.sa_flags = SA_NODEFER | SA_RESTART;
  (void) sigemptyset (&act.sa_mask);

  (void) sigaction (SIGABRT, &act, NULL);
  (void) sigaction (SIGFPE,  &act, NULL);

  if (__gl_unreserve_all_interrupts == 0)
    {
      (void) sigaction (SIGILL,  &act, NULL);
      (void) sigaction (SIGSEGV, &act, NULL);
      (void) sigaction (SIGBUS,  &act, NULL);
    }
  __gnat_handler_installed = 1;
}

void
__gnat_initialize ()
{
}

/******************************************/
/* __gnat_initialize (NT-mingw32 version) */
/******************************************/

#elif defined (__MINGW32__)
#include <windows.h>

static LONG __gnat_error_handler PARAMS ((PEXCEPTION_POINTERS));

/* __gnat_initialize (mingw32).  */

static LONG
__gnat_error_handler (info)
     PEXCEPTION_POINTERS info;
{
  static int recurse;
  struct Exception_Data *exception;
  char *msg;

  switch (info->ExceptionRecord->ExceptionCode)
    {
    case EXCEPTION_ACCESS_VIOLATION:
      /* If the failing address isn't maximally-aligned or if we've
	 recursed, this is a program error.  */
      if ((info->ExceptionRecord->ExceptionInformation[1] & 3) != 0
	  || recurse)
	{
	  exception = &program_error;
	  msg = "EXCEPTION_ACCESS_VIOLATION";
	}
      else
	{
	  /* See if the page before the faulting page is accessible.  Do that
	     by trying to access it. */
	  recurse++;
	  * ((volatile char *) (info->ExceptionRecord->ExceptionInformation[1]
				+ 4096));
	  exception = &storage_error;
	  msg = "stack overflow (or erroneous memory access)";
	}
      break;

    case EXCEPTION_ARRAY_BOUNDS_EXCEEDED:
      exception = &constraint_error;
      msg = "EXCEPTION_ARRAY_BOUNDS_EXCEEDED";
      break;

    case EXCEPTION_DATATYPE_MISALIGNMENT:
      exception = &constraint_error;
      msg = "EXCEPTION_DATATYPE_MISALIGNMENT";
      break;

    case EXCEPTION_FLT_DENORMAL_OPERAND:
      exception = &constraint_error;
      msg = "EXCEPTION_FLT_DENORMAL_OPERAND";
      break;

    case EXCEPTION_FLT_DIVIDE_BY_ZERO:
      exception = &constraint_error;
      msg = "EXCEPTION_FLT_DENORMAL_OPERAND";
      break;

    case EXCEPTION_FLT_INVALID_OPERATION:
      exception = &constraint_error;
      msg = "EXCEPTION_FLT_INVALID_OPERATION";
      break;

    case EXCEPTION_FLT_OVERFLOW:
      exception = &constraint_error;
      msg = "EXCEPTION_FLT_OVERFLOW";
      break;

    case EXCEPTION_FLT_STACK_CHECK:
      exception = &program_error;
      msg = "EXCEPTION_FLT_STACK_CHECK";
      break;

    case EXCEPTION_FLT_UNDERFLOW:
      exception = &constraint_error;
      msg = "EXCEPTION_FLT_UNDERFLOW";
      break;

    case EXCEPTION_INT_DIVIDE_BY_ZERO:
      exception = &constraint_error;
      msg = "EXCEPTION_INT_DIVIDE_BY_ZERO";
      break;

    case EXCEPTION_INT_OVERFLOW:
      exception = &constraint_error;
      msg = "EXCEPTION_INT_OVERFLOW";
      break;

    case EXCEPTION_INVALID_DISPOSITION:
      exception = &program_error;
      msg = "EXCEPTION_INVALID_DISPOSITION";
      break;

    case EXCEPTION_NONCONTINUABLE_EXCEPTION:
      exception = &program_error;
      msg = "EXCEPTION_NONCONTINUABLE_EXCEPTION";
      break;

    case EXCEPTION_PRIV_INSTRUCTION:
      exception = &program_error;
      msg = "EXCEPTION_PRIV_INSTRUCTION";
      break;

    case EXCEPTION_SINGLE_STEP:
      exception = &program_error;
      msg = "EXCEPTION_SINGLE_STEP";
      break;

    case EXCEPTION_STACK_OVERFLOW:
      exception = &storage_error;
      msg = "EXCEPTION_STACK_OVERFLOW";
      break;

   default:
      exception = &program_error;
      msg = "unhandled signal";
    }

  recurse = 0;
  Raise_From_Signal_Handler (exception, msg);
}

void
__gnat_install_handler ()
{
  SetUnhandledExceptionFilter (__gnat_error_handler);
  __gnat_handler_installed = 1;
}

void
__gnat_initialize ()
{

   /* Initialize floating-point coprocessor. This call is needed because
      the MS libraries default to 64-bit precision instead of 80-bit
      precision, and we require the full precision for proper operation,
      given that we have set Max_Digits etc with this in mind */

   __gnat_init_float ();

   /* initialize a lock for a process handle list - see a-adaint.c for the
      implementation of __gnat_portable_no_block_spawn, __gnat_portable_wait */
   __gnat_plist_init();
}

/**************************************/
/* __gnat_initialize (Interix version) */
/**************************************/

#elif defined (__INTERIX)

#include <signal.h>

static void __gnat_error_handler PARAMS ((int));

static void
__gnat_error_handler (sig)
     int sig;
{
  struct Exception_Data *exception;
  char *msg;

  switch (sig)
    {
    case SIGSEGV:
      exception = &storage_error;
      msg = "stack overflow or erroneous memory access";
      break;

    case SIGBUS:
      exception = &constraint_error;
      msg = "SIGBUS";
      break;

    case SIGFPE:
      exception = &constraint_error;
      msg = "SIGFPE";
      break;

    default:
      exception = &program_error;
      msg = "unhandled signal";
    }

  Raise_From_Signal_Handler (exception, msg);
}

void
__gnat_install_handler ()
{
  struct sigaction act;

  /* Set up signal handler to map synchronous signals to appropriate
     exceptions.  Make sure that the handler isn't interrupted by another
     signal that might cause a scheduling event! */

  act.sa_handler = __gnat_error_handler;
  act.sa_flags = 0;
  (void) sigemptyset (&act.sa_mask);

  /* Handlers for signals besides SIGSEGV cause c974013 to hang */
/*  (void) sigaction (SIGILL,  &act, NULL); */
/*  (void) sigaction (SIGABRT, &act, NULL); */
/*  (void) sigaction (SIGFPE,  &act, NULL); */
/*  (void) sigaction (SIGBUS,  &act, NULL); */
  if (__gl_unreserve_all_interrupts == 0)
    {
      (void) sigaction (SIGSEGV, &act, NULL);
    }
  __gnat_handler_installed = 1;
}

void
__gnat_initialize ()
{
   __gnat_init_float ();
}

/**************************************/
/* __gnat_initialize (LynxOS version) */
/**************************************/

#elif defined (__Lynx__)

void
__gnat_initialize ()
{
   __gnat_init_float ();
}

/*********************************/
/* __gnat_install_handler (Lynx) */
/*********************************/

void
__gnat_install_handler ()
{
  __gnat_handler_installed = 1;
}

/****************************/
/* __gnat_initialize (OS/2) */
/****************************/

#elif defined (__EMX__) /* OS/2 dependent initialization */

void
__gnat_initialize ()
{
}

/*********************************/
/* __gnat_install_handler (OS/2) */
/*********************************/

void
__gnat_install_handler ()
{
  __gnat_handler_installed = 1;
}

/***********************************/
/* __gnat_initialize (SGI version) */
/***********************************/

#elif defined (sgi)

#include <signal.h>
#include <siginfo.h>

#ifndef NULL
#define NULL 0
#endif

#define SIGADAABORT 48
#define SIGNAL_STACK_SIZE 4096
#define SIGNAL_STACK_ALIGNMENT 64

struct Machine_State
{
  sigcontext_t context;
};

static void __gnat_error_handler PARAMS ((int, int, sigcontext_t *));

static void
__gnat_error_handler (sig, code, sc)
     int sig;
     int code;
     sigcontext_t *sc;
{
  struct Machine_State  *mstate;
  struct Exception_Data *exception;
  char *msg;

  int i;

  switch (sig)
    {
    case SIGSEGV:
      if (code == EFAULT)
	{
	  exception = &program_error;
	  msg = "SIGSEGV: (Invalid virtual address)";
	}
      else if (code == ENXIO)
	{
	  exception = &program_error;
	  msg = "SIGSEGV: (Read beyond mapped object)";
	}
      else if (code == ENOSPC)
	{
	  exception = &program_error; /* ??? storage_error ??? */
	  msg = "SIGSEGV: (Autogrow for file failed)";
	}
      else if (code == EACCES)
	{
	  /* ??? Re-add smarts to further verify that we launched
		 the stack into a guard page, not an attempt to
		 write to .text or something */
	  exception = &storage_error;
	  msg = "SIGSEGV: (stack overflow or erroneous memory access)";
	}
      else
	{
	  /* Just in case the OS guys did it to us again.  Sometimes
	     they fail to document all of the valid codes that are
	     passed to signal handlers, just in case someone depends
	     on knowing all the codes */
	  exception = &program_error;
	  msg = "SIGSEGV: (Undocumented reason)";
	}
      break;

    case SIGBUS:
      /* Map all bus errors to Program_Error.  */
      exception = &program_error;
      msg = "SIGBUS";
      break;

    case SIGFPE:
      /* Map all fpe errors to Constraint_Error.  */
      exception = &constraint_error;
      msg = "SIGFPE";
      break;

    case SIGADAABORT:
      if ((*Check_Abort_Status) ())
	{
	  exception = &_abort_signal;
	  msg = "";
	}
      else
	return;

      break;

    default:
      /* Everything else is a Program_Error. */
      exception = &program_error;
      msg = "unhandled signal";
    }

  mstate = (*Get_Machine_State_Addr)();
  if (mstate != 0)
    memcpy ((void *) mstate, (const void *) sc, sizeof (sigcontext_t));

  Raise_From_Signal_Handler (exception, msg);

}

void
__gnat_install_handler ()
{
  stack_t ss;
  struct sigaction act;

  /* Setup signal handler to map synchronous signals to appropriate
     exceptions.  Make sure that the handler isn't interrupted by another
     signal that might cause a scheduling event! */

  act.sa_handler = __gnat_error_handler;
  act.sa_flags = SA_NODEFER + SA_RESTART;
  (void) sigfillset (&act.sa_mask);
  (void) sigemptyset (&act.sa_mask);

  (void) sigaction (SIGABRT, &act, NULL);
  (void) sigaction (SIGFPE,  &act, NULL);

  if (__gl_unreserve_all_interrupts == 0)
    {
      (void) sigaction (SIGILL,  &act, NULL);
      (void) sigaction (SIGSEGV, &act, NULL);
      (void) sigaction (SIGBUS,  &act, NULL);
    }
  (void) sigaction (SIGADAABORT,  &act, NULL);
  __gnat_handler_installed = 1;
}

void
__gnat_initialize ()
{
}

/*************************************************/
/* __gnat_initialize (Solaris and SunOS version) */
/*************************************************/

#elif defined (sun) && defined (__SVR4) && !defined (__vxworks)

#include <signal.h>
#include <siginfo.h>

static void __gnat_error_handler PARAMS ((int, siginfo_t *));

static void
__gnat_error_handler (sig, sip)
     int sig;
     siginfo_t *sip;
{
  struct Exception_Data *exception;
  static int recurse = 0;
  char *msg;

  /* If this was an explicit signal from a "kill", just resignal it.  */
  if (SI_FROMUSER (sip))
    {
      signal (sig, SIG_DFL);
      kill (getpid(), sig);
    }

  /* Otherwise, treat it as something we handle.  */
  switch (sig)
    {
    case SIGSEGV:
      /* If the problem was permissions, this is a constraint error.
	 Likewise if the failing address isn't maximally aligned or if
	 we've recursed.

	 ??? Using a static variable here isn't task-safe, but it's
	 much too hard to do anything else and we're just determining
	 which exception to raise.  */
      if (sip->si_code == SEGV_ACCERR
	  || (((long) sip->si_addr) & 3) != 0
	  || recurse)
	{
	  exception = &constraint_error;
	  msg = "SIGSEGV";
	}
      else
	{
	  /* See if the page before the faulting page is accessible.  Do that
	     by trying to access it.  We'd like to simply try to access
	     4096 + the faulting address, but it's not guaranteed to be
	     the actual address, just to be on the same page.  */
	  recurse++;
	  ((volatile char *)
	   ((long) sip->si_addr & - getpagesize ()))[getpagesize ()];
	  exception = &storage_error;
	  msg = "stack overflow (or erroneous memory access)";
	}
      break;

    case SIGBUS:
      exception = &program_error;
      msg = "SIGBUS";
      break;

    case SIGFPE:
      exception = &constraint_error;
      msg = "SIGFPE";
      break;

    default:
      exception = &program_error;
      msg = "unhandled signal";
    }

  recurse = 0;

  Raise_From_Signal_Handler (exception, msg);
}

void
__gnat_install_handler ()
{
  struct sigaction act;

  /* Set up signal handler to map synchronous signals to appropriate
     exceptions.  Make sure that the handler isn't interrupted by another
     signal that might cause a scheduling event! */

  act.sa_handler = __gnat_error_handler;
  act.sa_flags = SA_NODEFER | SA_RESTART | SA_SIGINFO;
  (void) sigemptyset (&act.sa_mask);

  (void) sigaction (SIGABRT, &act, NULL);

  if (__gl_unreserve_all_interrupts == 0)
    {
      (void) sigaction (SIGFPE,  &act, NULL);
      (void) sigaction (SIGSEGV, &act, NULL);
      (void) sigaction (SIGBUS,  &act, NULL);
    }
  __gnat_handler_installed = 1;
}

void
__gnat_initialize ()
{
}

/***********************************/
/* __gnat_initialize (SNI version) */
/***********************************/

#elif defined (__sni__)

/* SNI needs special defines and includes */

#define _XOPEN_SOURCE
#define _POSIX_SOURCE
#include <signal.h>

extern size_t __gnat_getpagesize PARAMS ((void));
static void __gnat_error_handler PARAMS ((int));

/* The run time needs this function which is a #define in SNI */

size_t
__gnat_getpagesize ()
{
  return getpagesize ();
}

static void
__gnat_error_handler (sig)
     int sig;
{
  struct Exception_Data *exception;
  char *msg;

  switch (sig)
    {
    case SIGSEGV:
      /* FIXME: we need to detect the case of a *real* SIGSEGV */
      exception = &storage_error;
      msg = "stack overflow or erroneous memory access";
      break;

    case SIGBUS:
      exception = &constraint_error;
      msg = "SIGBUS";
      break;

    case SIGFPE:
      exception = &constraint_error;
      msg = "SIGFPE";
      break;

    default:
      exception = &program_error;
      msg = "unhandled signal";
    }

  Raise_From_Signal_Handler (exception, msg);
}

void
__gnat_install_handler ()
{
  struct sigaction act;

  /* Set up signal handler to map synchronous signals to appropriate
     exceptions.  Make sure that the handler isn't interrupted by another
     signal that might cause a scheduling event! */

  act.sa_handler = __gnat_error_handler;
  act.sa_flags = SA_NODEFER | SA_RESTART;
  (void) sigemptyset (&act.sa_mask);

  (void) sigaction (SIGABRT, &act, NULL);
  (void) sigaction (SIGFPE,  &act, NULL);

  if (__gl_unreserve_all_interrupts == 0)
    {
      (void) sigaction (SIGILL,  &act, NULL);
      (void) sigaction (SIGSEGV, &act, NULL);
      (void) sigaction (SIGBUS,  &act, NULL);
    }
  __gnat_handler_installed = 1;
}

void
__gnat_initialize ()
{
}

/***********************************/
/* __gnat_initialize (VMS version) */
/***********************************/

#elif defined (VMS)

/* The prehandler actually gets control first on a condition. It swaps the
   stack pointer and calls the handler (__gnat_error_handler). */
extern long __gnat_error_prehandler ();

extern char *__gnat_error_prehandler_stack;   /* Alternate signal stack */

/* Conditions that don't have an Ada exception counterpart must raise
   Non_Ada_Error.  Since this is defined in s-auxdec, it should only be
   referenced by user programs, not the compiler or tools. Hence the
   #ifdef IN_RTS. */

#ifdef IN_RTS
#define Non_Ada_Error system__aux_dec__non_ada_error
extern struct Exception_Data Non_Ada_Error;

#define Coded_Exception system__vms_exception_table__coded_exception
extern struct Exception_Data *Coded_Exception (int);
#endif

/* Define macro symbols for the VMS conditions that become Ada exceptions.
   Most of these are also defined in the header file ssdef.h which has not
   yet been converted to be recoginized by Gnu C. Some, which couldn't be
   located, are assigned names based on the DEC test suite tests which
   raise them. */

#define SS$_ACCVIO            12
#define SS$_DEBUG           1132
#define SS$_INTDIV          1156
#define SS$_HPARITH         1284
#define SS$_STKOVF          1364
#define SS$_RESIGNAL        2328
#define MTH$_FLOOVEMAT   1475268       /* Some ACVC_21 CXA tests */
#define SS$_CE24VRU      3253636       /* Write to unopened file */
#define SS$_C980VTE      3246436       /* AST requests time slice */
#define CMA$_EXIT_THREAD 4227492
#define CMA$_EXCCOPLOS   4228108
#define CMA$_ALERTED     4227460

struct descriptor_s {unsigned short len, mbz; char *adr; };

static long __gnat_error_handler PARAMS ((int *, void *));

static long
__gnat_error_handler (sigargs, mechargs)
     int *sigargs;
     void *mechargs;
{
  struct Exception_Data *exception = 0;
  char *msg = "";
  char message [256];
  long prvhnd;
  struct descriptor_s msgdesc;
  int msg_flag = 0x000f; /* 1 bit for each of the four message parts */
  unsigned short outlen;
  char curr_icb [544];
  long curr_invo_handle;
  long *mstate;

  /* Resignaled conditions aren't effected by by pragma Import_Exception */

  switch (sigargs[1])
  {

    case CMA$_EXIT_THREAD:
      return SS$_RESIGNAL;

    case SS$_DEBUG: /* Gdb attach, resignal to merge activate gdbstub. */
      return SS$_RESIGNAL;

    case 1409786: /* Nickerson bug #33 ??? */
      return SS$_RESIGNAL;

    case 1381050: /* Nickerson bug #33 ??? */
      return SS$_RESIGNAL;

    case 11829410: /* Resignalled as Use_Error for CE10VRC */
      return SS$_RESIGNAL;

  }

#ifdef IN_RTS
  /* See if it's an imported exception. Mask off severity bits. */
  exception = Coded_Exception (sigargs [1] & 0xfffffff8);
  if (exception)
    {
      msgdesc.len = 256;
      msgdesc.mbz = 0;
      msgdesc.adr = message;
      SYS$GETMSG (sigargs[1], &outlen, &msgdesc, msg_flag, 0);
      message [outlen] = 0;
      msg = message;

      exception->Name_Length = 19;
      /* The full name really should be get sys$getmsg returns. ??? */
      exception->Full_Name = "IMPORTED_EXCEPTION";
      exception->Import_Code = sigargs [1] & 0xfffffff8;
    }
#endif

  if (exception == 0)
    switch (sigargs[1])
      {
      case SS$_ACCVIO:
        if (sigargs[3] == 0)
	  {
	    exception = &constraint_error;
	    msg = "access zero";
	  }
	else
	  {
	    exception = &storage_error;
	    msg = "stack overflow (or erroneous memory access)";
	  }
	break;

      case SS$_STKOVF:
	exception = &storage_error;
	msg = "stack overflow";
	break;

      case SS$_INTDIV:
	exception = &constraint_error;
	msg = "division by zero";
	break;

      case SS$_HPARITH:
#ifndef IN_RTS
	return SS$_RESIGNAL; /* toplev.c handles for compiler */
#else
	{
	  exception = &constraint_error;
	  msg = "arithmetic error";
	}
#endif
	break;

      case MTH$_FLOOVEMAT:
	exception = &constraint_error;
	msg = "floating overflow in math library";
	break;

      case SS$_CE24VRU:
	exception = &constraint_error;
	msg = "";
	break;

      case SS$_C980VTE:
	exception = &program_error;
	msg = "";
	break;

      default:
#ifndef IN_RTS
	exception = &program_error;
#else
	/* User programs expect Non_Ada_Error to be raised, reference
	   DEC Ada test CXCONDHAN. */
	exception = &Non_Ada_Error;
#endif
	msgdesc.len = 256;
	msgdesc.mbz = 0;
	msgdesc.adr = message;
	SYS$GETMSG (sigargs[1], &outlen, &msgdesc, msg_flag, 0);
	message [outlen] = 0;
	msg = message;
	break;
      }

  mstate = (long *) (*Get_Machine_State_Addr) ();
  if (mstate != 0)
    {
      LIB$GET_CURR_INVO_CONTEXT (&curr_icb);
      LIB$GET_PREV_INVO_CONTEXT (&curr_icb);
      LIB$GET_PREV_INVO_CONTEXT (&curr_icb);
      curr_invo_handle = LIB$GET_INVO_HANDLE (&curr_icb);
      *mstate = curr_invo_handle;
    }
  Raise_From_Signal_Handler (exception, msg);
}

void
__gnat_install_handler ()
{
  long prvhnd;
  char *c;

  c = (char *) malloc (2049);

  __gnat_error_prehandler_stack = &c[2048];

  /* __gnat_error_prehandler is an assembly function.  */
  SYS$SETEXV (1, __gnat_error_prehandler, 3, &prvhnd);
  __gnat_handler_installed = 1;
}

void
__gnat_initialize()
{
}

/***************************************/
/* __gnat_initialize (VXWorks version) */
/***************************************/

#elif defined(__vxworks)

#include <signal.h>
#include <taskLib.h>
#include <intLib.h>
#include <iv.h>

static void __gnat_init_handler PARAMS ((int));
extern int __gnat_inum_to_ivec PARAMS ((int));
static void __gnat_error_handler PARAMS ((int, int, struct sigcontext *));

static void
__gnat_int_handler (interr)
      int interr;
{
  /* Note that we should use something like Raise_From_Int_Handler here, but
     for now Raise_From_Signal_Handler will do the job. ??? */

  Raise_From_Signal_Handler (&storage_error, "stack overflow");
}

/* Used for stack-checking on VxWorks. Must be task-local in
   tasking programs */

void *__gnat_stack_limit = NULL;

#ifndef __alpha_vxworks

/* getpid is used by s-parint.adb, but is not defined by VxWorks, except
   on Alpha VxWorks */

extern long getpid PARAMS ((void));

long
getpid ()
{
  return taskIdSelf ();
}
#endif

/* This is needed by the GNAT run time to handle Vxworks interrupts */
int
__gnat_inum_to_ivec (num)
     int num;
{
  return INUM_TO_IVEC (num);
}

static void
__gnat_error_handler (sig, code, sc)
     int sig;
     int code;
     struct sigcontext *sc;
{
  struct Exception_Data *exception;
  sigset_t mask;
  int result;
  char *msg;

  /* VxWorks will always mask out the signal during the signal handler and
     will reenable it on a longjmp.  GNAT does not generate a longjmp to
     return from a signal handler so the signal will still be masked unless
     we unmask it. */
  (void) sigprocmask (SIG_SETMASK, NULL, &mask);
  sigdelset (&mask, sig);
  (void) sigprocmask (SIG_SETMASK, &mask, NULL);

  /* VxWorks will suspend the task when it gets a hardware exception.  We
     take the liberty of resuming the task for the application. */
  if (taskIsSuspended (taskIdSelf ()) != 0)
    (void) taskResume (taskIdSelf ());

  switch (sig)
    {
    case SIGFPE:
      exception = &constraint_error;
      msg = "SIGFPE";
      break;
    case SIGILL:
      exception = &constraint_error;
      msg = "SIGILL";
      break;
    case SIGSEGV:
      exception = &program_error;
      msg = "SIGSEGV";
      break;
    case SIGBUS:
      exception = &program_error;
      msg = "SIGBUS";
      break;
    default:
      exception = &program_error;
      msg = "unhandled signal";
    }

  Raise_From_Signal_Handler (exception, msg);
}

void
__gnat_install_handler ()
{
  struct sigaction act;

  /* Setup signal handler to map synchronous signals to appropriate
     exceptions.  Make sure that the handler isn't interrupted by another
     signal that might cause a scheduling event! */

  act.sa_handler = __gnat_error_handler;
  act.sa_flags = SA_SIGINFO | SA_ONSTACK;
  (void) sigemptyset (&act.sa_mask);

  (void) sigaction (SIGFPE,  &act, NULL);

  if (__gl_unreserve_all_interrupts == 0)
    {
      (void) sigaction (SIGILL,  &act, NULL);
      (void) sigaction (SIGSEGV, &act, NULL);
      (void) sigaction (SIGBUS,  &act, NULL);
    }
  __gnat_handler_installed = 1;
}

#define HAVE_GNAT_INIT_FLOAT

void
__gnat_init_float ()
{
#if defined (_ARCH_PPC) && !defined (_SOFT_FLOAT)
  /* Disable overflow/underflow exceptions on the PPC processor, this is needed
      to get correct Ada semantic */
  asm ("mtfsb0 25");
  asm ("mtfsb0 26");
#endif
}

void
__gnat_initialize ()
{
  TASK_DESC pTaskDesc;

  if (taskInfoGet (taskIdSelf (), &pTaskDesc) != OK)
    printErr ("Cannot get task info");

  __gnat_stack_limit = (void *) pTaskDesc.td_pStackLimit;

  __gnat_init_float ();

#ifdef __mips_vxworks
#if 0
  /* For now remove this handler, since it is causing interferences with gdb */

  /* Connect the overflow trap directly to the __gnat_int_handler routine
   as it is not converted to a signal by VxWorks. */

  intConnect (INUM_TO_IVEC (IV_TRAP_VEC), &__gnat_int_handler, IV_TRAP_VEC);
#endif
#endif
}

#else

/* For all other versions of GNAT, the initialize routine and handler
   installation do nothing */

/***************************************/
/* __gnat_initialize (default version) */
/***************************************/

void
__gnat_initialize ()
{
}

/********************************************/
/* __gnat_install_handler (default version) */
/********************************************/

void
__gnat_install_handler ()
{
  __gnat_handler_installed = 1;
}

#endif

/*********************/
/* __gnat_init_float */
/*********************/

/* This routine is called as each process thread is created, for possible
   initialization of the FP processor. This version is used under INTERIX,
   WIN32 and could be used under OS/2 */

#if defined (_WIN32) || defined (__INTERIX) || defined (__EMX__) \
  || defined (__Lynx__)

#define HAVE_GNAT_INIT_FLOAT

void
__gnat_init_float ()
{
#if defined (__i386__) || defined (i386)

  /* This is used to properly initialize the FPU on an x86 for each
     process thread. */

  asm ("finit");

#endif  /* Defined __i386__ */
}
#endif

#ifndef HAVE_GNAT_INIT_FLOAT

/* All targets without a specific __gnat_init_float will use an empty one */
void
__gnat_init_float ()
{
}
#endif