exception.cc

GCC编译器源代码

// Functions for Exception Support for -*- C++ -*-
// Copyright (C) 1994, 1995, 1996 Free Software Foundation

// This file is part of GNU CC.

// GNU CC 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 2, or (at your option)
// any later version.

// GNU CC 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 GNU CC; see the 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 library with other files,
// some of which are compiled with GCC, to produce an executable,
// this library does not by itself cause the resulting executable
// to be covered by the GNU General Public License.
// This exception does not however invalidate any other reasons why
// the executable file might be covered by the GNU General Public License.

#pragma implementation "exception"

#include "typeinfo"
#include "exception"

/* Define terminate, unexpected, set_terminate, set_unexpected as
   well as the default terminate func and default unexpected func.  */

extern terminate_handler __terminate_func __attribute__((__noreturn__));

void
terminate ()
{
  __terminate_func ();
}

void
__default_unexpected ()
{
  terminate ();
}

static unexpected_handler __unexpected_func = __default_unexpected;

terminate_handler
set_terminate (terminate_handler func)
{
  terminate_handler old = __terminate_func;

  __terminate_func = func;
  return old;
}

unexpected_handler
set_unexpected (unexpected_handler func)
{
  unexpected_handler old = __unexpected_func;

  __unexpected_func = func;
  return old;
}

void
unexpected ()
{
  __unexpected_func ();
}

/* C++-specific state about the current exception.
   This must match init_exception_processing().

   Note that handlers and caught are not redundant; when rethrown, an
   exception can have multiple active handlers and still be considered
   uncaught.  */

struct cp_eh_info
{
  void *value;
  void *type;
  void (*cleanup)(void *, int);
  bool caught;
  cp_eh_info *next;
  long handlers;
};

/* Language-specific EH info pointer, defined in libgcc2.  */

extern cp_eh_info *__eh_info;  // actually void*

/* Is P the type_info node for a pointer of some kind?  */

extern bool __is_pointer (void *);

/* Compiler hook to return a pointer to the info for the current exception.
   Used by get_eh_info ().  */

extern "C" cp_eh_info *
__cp_exception_info (void)
{
  return __eh_info;
}

/* Compiler hook to push a new exception onto the stack.
   Used by expand_throw().  */

extern "C" void
__cp_push_exception (void *value, void *type, void (*cleanup)(void *, int))
{
  cp_eh_info *p = new cp_eh_info;
  p->value = value;
  p->type = type;
  p->cleanup = cleanup;
  p->handlers = 0;
  p->caught = false;
  p->next = __eh_info;
  __eh_info = p;
}

/* Compiler hook to pop an exception that has been finalized.  Used by
   push_eh_cleanup().  P is the info for the exception caught by the
   current catch block, and HANDLER determines if we've been called from
   an exception handler; if so, we avoid destroying the object on rethrow.  */

extern "C" void
__cp_pop_exception (cp_eh_info *p, bool handler)
{
  cp_eh_info **q = &__eh_info;

  --p->handlers;

  if (p->handlers > 0 || (handler && p == *q))
    return;

  for (; *q; q = &((*q)->next))
    if (*q == p)
      break;

  if (! *q)
    terminate ();

  *q = p->next;

  if (p->cleanup)
    /* 3 is a magic value for destructors; see build_delete().  */
    p->cleanup (p->value, 3);
  else if (__is_pointer (p->type))
    /* do nothing; pointers are passed directly in p->value.  */;
  else
    delete p->value;

  delete p;
}

extern "C" void
__uncatch_exception (void)
{
  cp_eh_info *p = __cp_exception_info ();
  if (p)
    p->caught = false;
  /* otherwise __throw will call terminate(); don't crash here.  */
}

extern "C" void
__throw_bad_cast (void)
{
  throw bad_cast ();
}

extern "C" void
__throw_bad_typeid (void)
{
  throw bad_typeid ();
}

/* Has the current exception been caught?  */

bool
uncaught_exception ()
{
  cp_eh_info *p = __cp_exception_info ();
  return p && ! p->caught;
}

const char * exception::
what () const
{
  return typeid (*this).name ();
}