path: root/gdb/exceptions.c

/* Exception (throw catch) mechanism, for GDB, the GNU debugger.

   Copyright (C) 1986, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
   1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008,
   2009, 2010, 2011 Free Software Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT 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
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include "defs.h"
#include "exceptions.h"
#include "breakpoint.h"
#include "target.h"
#include "inferior.h"
#include "annotate.h"
#include "ui-out.h"
#include "gdb_assert.h"
#include "gdb_string.h"
#include "serial.h"
#include "gdbthread.h"

const struct gdb_exception exception_none = { 0, GDB_NO_ERROR, NULL };

/* Possible catcher states.  */
enum catcher_state {
  /* Initial state, a new catcher has just been created.  */
  CATCHER_CREATED,
  /* The catch code is running.  */
  CATCHER_RUNNING,
  CATCHER_RUNNING_1,
  /* The catch code threw an exception.  */
  CATCHER_ABORTING
};

/* Possible catcher actions.  */
enum catcher_action {
  CATCH_ITER,
  CATCH_ITER_1,
  CATCH_THROWING
};

struct catcher
{
  enum catcher_state state;
  /* Jump buffer pointing back at the exception handler.  */
  EXCEPTIONS_SIGJMP_BUF buf;
  /* Status buffer belonging to the exception handler.  */
  volatile struct gdb_exception *exception;
  /* Saved/current state.  */
  int mask;
  struct cleanup *saved_cleanup_chain;
  /* Back link.  */
  struct catcher *prev;
};

/* Where to go for throw_exception().  */
static struct catcher *current_catcher;

/* Return length of current_catcher list.  */

static int
catcher_list_size (void)
{
  int size;
  struct catcher *catcher;

  for (size = 0, catcher = current_catcher;
       catcher != NULL;
       catcher = catcher->prev)
    ++size;

  return size;
}

EXCEPTIONS_SIGJMP_BUF *
exceptions_state_mc_init (volatile struct gdb_exception *exception,
			  return_mask mask)
{
  struct catcher *new_catcher = XZALLOC (struct catcher);

  /* Start with no exception, save it's address.  */
  exception->reason = 0;
  exception->error = GDB_NO_ERROR;
  exception->message = NULL;
  new_catcher->exception = exception;

  new_catcher->mask = mask;

  /* Prevent error/quit during FUNC from calling cleanups established
     prior to here.  */
  new_catcher->saved_cleanup_chain = save_cleanups ();

  /* Push this new catcher on the top.  */
  new_catcher->prev = current_catcher;
  current_catcher = new_catcher;
  new_catcher->state = CATCHER_CREATED;

  return &new_catcher->buf;
}

static void
catcher_pop (void)
{
  struct catcher *old_catcher = current_catcher;

  current_catcher = old_catcher->prev;

  /* Restore the cleanup chain, the error/quit messages, and the uiout
     builder, to their original states.  */

  restore_cleanups (old_catcher->saved_cleanup_chain);

  xfree (old_catcher);
}

/* Catcher state machine.  Returns non-zero if the m/c should be run
   again, zero if it should abort.  */

static int
exceptions_state_mc (enum catcher_action action)
{
  switch (current_catcher->state)
    {
    case CATCHER_CREATED:
      switch (action)
	{
	case CATCH_ITER:
	  /* Allow the code to run the catcher.  */
	  current_catcher->state = CATCHER_RUNNING;
	  return 1;
	default:
	  internal_error (__FILE__, __LINE__, _("bad state"));
	}
    case CATCHER_RUNNING:
      switch (action)
	{
	case CATCH_ITER:
	  /* No error/quit has occured.  Just clean up.  */
	  catcher_pop ();
	  return 0;
	case CATCH_ITER_1:
	  current_catcher->state = CATCHER_RUNNING_1;
	  return 1;
	case CATCH_THROWING:
	  current_catcher->state = CATCHER_ABORTING;
	  /* See also throw_exception.  */
	  return 1;
	default:
	  internal_error (__FILE__, __LINE__, _("bad switch"));
	}
    case CATCHER_RUNNING_1:
      switch (action)
	{
	case CATCH_ITER:
	  /* The did a "break" from the inner while loop.  */
	  catcher_pop ();
	  return 0;
	case CATCH_ITER_1:
	  current_catcher->state = CATCHER_RUNNING;
	  return 0;
	case CATCH_THROWING:
	  current_catcher->state = CATCHER_ABORTING;
	  /* See also throw_exception.  */
	  return 1;
	default:
	  internal_error (__FILE__, __LINE__, _("bad switch"));
	}
    case CATCHER_ABORTING:
      switch (action)
	{
	case CATCH_ITER:
	  {
	    struct gdb_exception exception = *current_catcher->exception;

	    if (current_catcher->mask & RETURN_MASK (exception.reason))
	      {
		/* Exit normally if this catcher can handle this
		   exception.  The caller analyses the func return
		   values.  */
		catcher_pop ();
		return 0;
	      }
	    /* The caller didn't request that the event be caught,
	       relay the event to the next containing
	       catch_errors().  */
	    catcher_pop ();
	    throw_exception (exception);
	  }
	default:
	  internal_error (__FILE__, __LINE__, _("bad state"));
	}
    default:
      internal_error (__FILE__, __LINE__, _("bad switch"));
    }
}

int
exceptions_state_mc_action_iter (void)
{
  return exceptions_state_mc (CATCH_ITER);
}

int
exceptions_state_mc_action_iter_1 (void)
{
  return exceptions_state_mc (CATCH_ITER_1);
}

/* Return EXCEPTION to the nearest containing catch_errors().  */

void
throw_exception (struct gdb_exception exception)
{
  quit_flag = 0;
  immediate_quit = 0;

  do_cleanups (ALL_CLEANUPS);

  /* Jump to the containing catch_errors() call, communicating REASON
     to that call via setjmp's return value.  Note that REASON can't
     be zero, by definition in defs.h.  */
  exceptions_state_mc (CATCH_THROWING);
  *current_catcher->exception = exception;
  EXCEPTIONS_SIGLONGJMP (current_catcher->buf, exception.reason);
}

void
deprecated_throw_reason (enum return_reason reason)
{
  struct gdb_exception exception;

  memset (&exception, 0, sizeof exception);

  exception.reason = reason;
  switch (reason)
    {
    case RETURN_QUIT:
      break;
    case RETURN_ERROR:
      exception.error = GENERIC_ERROR;
      break;
    default:
      internal_error (__FILE__, __LINE__, _("bad switch"));
    }
  
  throw_exception (exception);
}

static void
print_flush (void)
{
  struct serial *gdb_stdout_serial;

  if (deprecated_error_begin_hook)
    deprecated_error_begin_hook ();
  target_terminal_ours ();

  /* We want all output to appear now, before we print the error.  We
     have 3 levels of buffering we have to flush (it's possible that
     some of these should be changed to flush the lower-level ones
     too):  */

  /* 1.  The _filtered buffer.  */
  wrap_here ("");

  /* 2.  The stdio buffer.  */
  gdb_flush (gdb_stdout);
  gdb_flush (gdb_stderr);

  /* 3.  The system-level buffer.  */
  gdb_stdout_serial = serial_fdopen (1);
  if (gdb_stdout_serial)
    {
      serial_drain_output (gdb_stdout_serial);
      serial_un_fdopen (gdb_stdout_serial);
    }

  annotate_error_begin ();
}

static void
print_exception (struct ui_file *file, struct gdb_exception e)
{
  /* KLUGE: cagney/2005-01-13: Write the string out one line at a time
     as that way the MI's behavior is preserved.  */
  const char *start;
  const char *end;

  for (start = e.message; start != NULL; start = end)
    {
      end = strchr (start, '\n');
      if (end == NULL)
	fputs_filtered (start, file);
      else
	{
	  end++;
	  ui_file_write (file, start, end - start);
	}
    }					    
  fprintf_filtered (file, "\n");

  /* Now append the annotation.  */
  switch (e.reason)
    {
    case RETURN_QUIT:
      annotate_quit ();
      break;
    case RETURN_ERROR:
      /* Assume that these are all errors.  */
      annotate_error ();
      break;
    default:
      internal_error (__FILE__, __LINE__, _("Bad switch."));
    }
}

void
exception_print (struct ui_file *file, struct gdb_exception e)
{
  if (e.reason < 0 && e.message != NULL)
    {
      print_flush ();
      print_exception (file, e);
    }
}

void
exception_fprintf (struct ui_file *file, struct gdb_exception e,
		   const char *prefix, ...)
{
  if (e.reason < 0 && e.message != NULL)
    {
      va_list args;

      print_flush ();

      /* Print the prefix.  */
      va_start (args, prefix);
      vfprintf_filtered (file, prefix, args);
      va_end (args);

      print_exception (file, e);
    }
}

static void
print_any_exception (struct ui_file *file, const char *prefix,
		     struct gdb_exception e)
{
  if (e.reason < 0 && e.message != NULL)
    {
      target_terminal_ours ();
      wrap_here ("");		/* Force out any buffered output.  */
      gdb_flush (gdb_stdout);
      annotate_error_begin ();

      /* Print the prefix.  */
      if (prefix != NULL && prefix[0] != '\0')
	fputs_filtered (prefix, file);
      print_exception (file, e);
    }
}

/* A stack of exception messages.
   This is needed to handle nested calls to throw_it: we don't want to
   xfree space for a message before it's used.
   This can happen if we throw an exception during a cleanup:
   An outer TRY_CATCH may have an exception message it wants to print,
   but while doing cleanups further calls to throw_it are made.

   This is indexed by the size of the current_catcher list.
   It is a dynamically allocated array so that we don't care how deeply
   GDB nests its TRY_CATCHs.  */
static char **exception_messages;

/* The number of currently allocated entries in exception_messages.  */
static int exception_messages_size;

static void ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (3, 0)
throw_it (enum return_reason reason, enum errors error, const char *fmt,
	  va_list ap)
{
  struct gdb_exception e;
  char *new_message;
  int depth = catcher_list_size ();

  gdb_assert (depth > 0);

  /* Note: The new message may use an old message's text.  */
  new_message = xstrvprintf (fmt, ap);

  if (depth > exception_messages_size)
    {
      int old_size = exception_messages_size;

      exception_messages_size = depth + 10;
      exception_messages = (char **) xrealloc (exception_messages,
					       exception_messages_size
					       * sizeof (char *));
      memset (exception_messages + old_size, 0,
	      (exception_messages_size - old_size) * sizeof (char *));
    }

  xfree (exception_messages[depth - 1]);
  exception_messages[depth - 1] = new_message;

  /* Create the exception.  */
  e.reason = reason;
  e.error = error;
  e.message = new_message;

  /* Throw the exception.  */
  throw_exception (e);
}

void
throw_verror (enum errors error, const char *fmt, va_list ap)
{
  throw_it (RETURN_ERROR, error, fmt, ap);
}

void
throw_vfatal (const char *fmt, va_list ap)
{
  throw_it (RETURN_QUIT, GDB_NO_ERROR, fmt, ap);
}

void
throw_error (enum errors error, const char *fmt, ...)
{
  va_list args;

  va_start (args, fmt);
  throw_it (RETURN_ERROR, error, fmt, args);
  va_end (args);
}

/* Call FUNC(UIOUT, FUNC_ARGS) but wrapped within an exception
   handler.  If an exception (enum return_reason) is thrown using
   throw_exception() than all cleanups installed since
   catch_exceptions() was entered are invoked, the (-ve) exception
   value is then returned by catch_exceptions.  If FUNC() returns
   normally (with a positive or zero return value) then that value is
   returned by catch_exceptions().  It is an internal_error() for
   FUNC() to return a negative value.

   See exceptions.h for further usage details.

   Must not be called with immediate_quit in effect (bad things might
   happen, say we got a signal in the middle of a memcpy to quit_return).
   This is an OK restriction; with very few exceptions immediate_quit can
   be replaced by judicious use of QUIT.  */

/* MAYBE: cagney/1999-11-05: catch_errors() in conjunction with
   error() et al. could maintain a set of flags that indicate the
   current state of each of the longjmp buffers.  This would give the
   longjmp code the chance to detect a longjmp botch (before it gets
   to longjmperror()).  Prior to 1999-11-05 this wasn't possible as
   code also randomly used a SET_TOP_LEVEL macro that directly
   initialized the longjmp buffers.  */

int
catch_exceptions (struct ui_out *uiout,
		  catch_exceptions_ftype *func,
		  void *func_args,
		  return_mask mask)
{
  return catch_exceptions_with_msg (uiout, func, func_args, NULL, mask);
}

int
catch_exceptions_with_msg (struct ui_out *func_uiout,
		  	   catch_exceptions_ftype *func,
		  	   void *func_args,
			   char **gdberrmsg,
		  	   return_mask mask)
{
  volatile struct gdb_exception exception;
  volatile int val = 0;
  struct ui_out *saved_uiout;

  /* Save and override the global ``struct ui_out'' builder.  */
  saved_uiout = current_uiout;
  current_uiout = func_uiout;

  TRY_CATCH (exception, RETURN_MASK_ALL)
    {
      val = (*func) (current_uiout, func_args);
    }

  /* Restore the global builder.  */
  current_uiout = saved_uiout;

  if (exception.reason < 0 && (mask & RETURN_MASK (exception.reason)) == 0)
    {
      /* The caller didn't request that the event be caught.
	 Rethrow.  */
      throw_exception (exception);
    }

  print_any_exception (gdb_stderr, NULL, exception);
  gdb_assert (val >= 0);
  gdb_assert (exception.reason <= 0);
  if (exception.reason < 0)
    {
      /* If caller wants a copy of the low-level error message, make
	 one.  This is used in the case of a silent error whereby the
	 caller may optionally want to issue the message.  */
      if (gdberrmsg != NULL)
	{
	  if (exception.message != NULL)
	    *gdberrmsg = xstrdup (exception.message);
	  else
	    *gdberrmsg = NULL;
	}
      return exception.reason;
    }
  return val;
}

/* This function is superseded by catch_exceptions().  */

int
catch_errors (catch_errors_ftype *func, void *func_args, char *errstring,
	      return_mask mask)
{
  volatile int val = 0;
  volatile struct gdb_exception exception;
  struct ui_out *saved_uiout;

  /* Save the global ``struct ui_out'' builder.  */
  saved_uiout = current_uiout;

  TRY_CATCH (exception, RETURN_MASK_ALL)
    {
      val = func (func_args);
    }

  /* Restore the global builder.  */
  current_uiout = saved_uiout;

  if (exception.reason < 0 && (mask & RETURN_MASK (exception.reason)) == 0)
    {
      /* The caller didn't request that the event be caught.
	 Rethrow.  */
      throw_exception (exception);
    }

  print_any_exception (gdb_stderr, errstring, exception);
  if (exception.reason != 0)
    return 0;
  return val;
}

int
catch_command_errors (catch_command_errors_ftype * command,
		      char *arg, int from_tty, return_mask mask)
{
  volatile struct gdb_exception e;

  TRY_CATCH (e, mask)
    {
      command (arg, from_tty);
    }
  print_any_exception (gdb_stderr, NULL, e);
  if (e.reason < 0)
    return 0;
  return 1;
}