except.c

gcc-2.95.3 Linux下最常用的C编译器

  decl = decay_conversion (decl);

  fn = get_identifier ("__check_eh_spec");
  if (IDENTIFIER_GLOBAL_VALUE (fn))
    fn = IDENTIFIER_GLOBAL_VALUE (fn);
  else
    {
      push_obstacks_nochange ();
      end_temporary_allocation ();

      tmp = tree_cons
	(NULL_TREE, integer_type_node, tree_cons
	 (NULL_TREE, TREE_TYPE (decl), void_list_node));
      tmp = build_function_type	(void_type_node, tmp);
  
      fn = build_lang_decl (FUNCTION_DECL, fn, tmp);
      DECL_EXTERNAL (fn) = 1;
      TREE_PUBLIC (fn) = 1;
      DECL_ARTIFICIAL (fn) = 1;
      TREE_THIS_VOLATILE (fn) = 1;
      pushdecl_top_level (fn);
      make_function_rtl (fn);
      pop_obstacks ();
    }

  mark_used (fn);
  tmp = expr_tree_cons (NULL_TREE, build_int_2 (count, 0), expr_tree_cons
			(NULL_TREE, decl, NULL_TREE));
  tmp = build_call (fn, TREE_TYPE (TREE_TYPE (fn)), tmp);
  expand_expr (tmp, const0_rtx, VOIDmode, EXPAND_NORMAL);

  expand_end_catch_block ();
  expand_end_all_catch ();
}

/* This is called to expand all the toplevel exception handling
   finalization for a function.  It should only be called once per
   function.  */

void
expand_exception_blocks ()
{
  do_pending_stack_adjust ();
  push_to_sequence (catch_clauses);
  expand_leftover_cleanups ();
  do_pending_stack_adjust ();
  catch_clauses = get_insns ();
  end_sequence ();

  /* Do this after we expand leftover cleanups, so that the
     expand_eh_region_end that expand_end_eh_spec does will match the
     right expand_eh_region_start, and make sure it comes out before
     the terminate protected region.  */
  if (TYPE_RAISES_EXCEPTIONS (TREE_TYPE (current_function_decl)))
    {
     expand_end_eh_spec (TYPE_RAISES_EXCEPTIONS (TREE_TYPE (current_function_decl)));
     do_pending_stack_adjust ();
     push_to_sequence (catch_clauses);
     expand_leftover_cleanups ();
     do_pending_stack_adjust ();
     catch_clauses = get_insns ();
     end_sequence ();
    }

  if (catch_clauses)
    {
      rtx funcend = gen_label_rtx ();
      emit_jump (funcend);

      /* We cannot protect n regions this way if we must flow into the
	 EH region through the top of the region, as we have to with
	 the setjmp/longjmp approach.  */
      if (exceptions_via_longjmp == 0)
	expand_eh_region_start ();

      emit_insns (catch_clauses);
      catch_clauses = NULL_RTX;

      if (exceptions_via_longjmp == 0)
	expand_eh_region_end (build_terminate_handler ());

      expand_leftover_cleanups ();

      emit_label (funcend);
    }
}

tree
start_anon_func ()
{
  static int counter = 0;
  int old_interface_unknown = interface_unknown;
  char name[32];
  tree params;
  tree t;

  push_cp_function_context (NULL_TREE);
  push_to_top_level ();

  /* No need to mangle this.  */
  push_lang_context (lang_name_c);

  interface_unknown = 1;

  params = void_list_node;
  /* tcf stands for throw clean function.  */
  sprintf (name, "__tcf_%d", counter++);
  t = make_call_declarator (get_identifier (name), params, NULL_TREE,
			    NULL_TREE);
  start_function (decl_tree_cons (NULL_TREE, get_identifier ("static"),
				  void_list_node),
		  t, NULL_TREE, 0);
  store_parm_decls ();
  pushlevel (0);
  clear_last_expr ();
  push_momentary ();
  expand_start_bindings (0);
  emit_line_note (input_filename, lineno);

  interface_unknown = old_interface_unknown;

  pop_lang_context ();

  return current_function_decl;
}

void
end_anon_func ()
{
  expand_end_bindings (getdecls (), 1, 0);
  poplevel (1, 0, 0);
  pop_momentary ();

  finish_function (lineno, 0, 0);

  pop_from_top_level ();
  pop_cp_function_context (NULL_TREE);
}

/* Return a pointer to a buffer for an exception object of type TYPE.  */

static tree
alloc_eh_object (type)
     tree type;
{
  tree fn, exp;

  fn = get_identifier ("__eh_alloc");
  if (IDENTIFIER_GLOBAL_VALUE (fn))
    fn = IDENTIFIER_GLOBAL_VALUE (fn);
  else
    {
      /* Declare __eh_alloc (size_t), as defined in exception.cc.  */
      tree tmp;
      push_obstacks_nochange ();
      end_temporary_allocation ();
      tmp = tree_cons (NULL_TREE, sizetype, void_list_node);
      fn = build_lang_decl (FUNCTION_DECL, fn,
			    build_function_type (ptr_type_node, tmp));
      DECL_EXTERNAL (fn) = 1;
      TREE_PUBLIC (fn) = 1;
      DECL_ARTIFICIAL (fn) = 1;
      pushdecl_top_level (fn);
      make_function_rtl (fn);
      pop_obstacks ();
    }

  mark_used (fn);
  exp = build_function_call (fn, expr_tree_cons
			     (NULL_TREE, size_in_bytes (type), NULL_TREE));
  exp = build1 (NOP_EXPR, build_pointer_type (type), exp);
  return exp;
}

/* Expand a throw statement.  This follows the following
   algorithm:

	1. Allocate space to save the current PC onto the stack.
	2. Generate and emit a label and save its address into the
		newly allocated stack space since we can't save the pc directly.
	3. If this is the first call to throw in this function:
		generate a label for the throw block
	4. jump to the throw block label.  */

void
expand_throw (exp)
     tree exp;
{
  tree fn;
  static tree cleanup_type;

  if (! doing_eh (1))
    return;

  if (exp)
    {
      tree throw_type;
      tree cleanup = NULL_TREE, e;

      /* throw expression */
      /* First, decay it.  */
      exp = decay_conversion (exp);

      /* cleanup_type is void (*)(void *, int),
	 the internal type of a destructor. */
      if (cleanup_type == NULL_TREE)
	{
	  push_obstacks_nochange ();
	  end_temporary_allocation ();
	  cleanup_type = build_pointer_type
	    (build_function_type
	     (void_type_node, tree_cons
	      (NULL_TREE, ptr_type_node, tree_cons
	       (NULL_TREE, integer_type_node, void_list_node))));
	  pop_obstacks ();
	}

      if (TYPE_PTR_P (TREE_TYPE (exp)))
	throw_type = build_eh_type (exp);
      else
	{
	  tree object, ptr;

	  /* OK, this is kind of wacky.  The WP says that we call
	     terminate

	     when the exception handling mechanism, after completing
	     evaluation of the expression to be thrown but before the
	     exception is caught (_except.throw_), calls a user function
	     that exits via an uncaught exception.

	     So we have to protect the actual initialization of the
	     exception object with terminate(), but evaluate the expression
	     first.  We also expand the call to __eh_alloc
	     first.  Since there could be temps in the expression, we need
	     to handle that, too.  */

	  expand_start_target_temps ();

#if 0
	  /* Unfortunately, this doesn't work.  */
	  preexpand_calls (exp);
#else
	  /* Store the throw expression into a temp.  This can be less
	     efficient than storing it into the allocated space directly, but
	     oh well.  To do this efficiently we would need to insinuate
	     ourselves into expand_call.  */
	  if (TREE_SIDE_EFFECTS (exp))
	    {
	      tree temp = build_decl (VAR_DECL, NULL_TREE, TREE_TYPE (exp));
	      DECL_ARTIFICIAL (temp) = 1;
	      DECL_RTL (temp) = assign_temp (TREE_TYPE (exp), 2, 0, 1);
	      DECL_INITIAL (temp) = exp;
	      cp_finish_decl (temp, exp, NULL_TREE, 0, LOOKUP_ONLYCONVERTING);
	      exp = temp;
	    }
#endif

	  /* Allocate the space for the exception.  */
	  ptr = save_expr (alloc_eh_object (TREE_TYPE (exp)));
	  expand_expr (ptr, const0_rtx, VOIDmode, 0);

	  expand_eh_region_start ();

	  object = build_indirect_ref (ptr, NULL_PTR);
	  exp = build_modify_expr (object, INIT_EXPR, exp);

	  if (exp == error_mark_node)
	    error ("  in thrown expression");

	  expand_expr (exp, const0_rtx, VOIDmode, 0);
	  expand_eh_region_end (build_terminate_handler ());
	  expand_end_target_temps ();

	  throw_type = build_eh_type (object);

	  if (TYPE_HAS_DESTRUCTOR (TREE_TYPE (object)))
	    {
	      cleanup = lookup_fnfields (TYPE_BINFO (TREE_TYPE (object)),
					 dtor_identifier, 0);
	      cleanup = TREE_VALUE (cleanup);
	      mark_used (cleanup);
	      mark_addressable (cleanup);
	      /* Pretend it's a normal function.  */
	      cleanup = build1 (ADDR_EXPR, cleanup_type, cleanup);
	    }

	  exp = ptr;
	}

      /* Cast EXP to `void *' so that it will match the prototype for
	 __cp_push_exception.  */
      exp = convert (ptr_type_node, exp);

      if (cleanup == NULL_TREE)
	{
	  cleanup = build_int_2 (0, 0);
	  TREE_TYPE (cleanup) = cleanup_type;
	}

      fn = get_identifier ("__cp_push_exception");
      if (IDENTIFIER_GLOBAL_VALUE (fn))
	fn = IDENTIFIER_GLOBAL_VALUE (fn);
      else
	{
	  /* Declare __cp_push_exception (void*, void*, void (*)(void*, int)),
	     as defined in exception.cc.  */
	  tree tmp;
	  push_obstacks_nochange ();
	  end_temporary_allocation ();
	  tmp = tree_cons
	    (NULL_TREE, ptr_type_node, tree_cons
	     (NULL_TREE, ptr_type_node, tree_cons
	      (NULL_TREE, cleanup_type, void_list_node)));
	  fn = build_lang_decl (FUNCTION_DECL, fn,
				build_function_type (void_type_node, tmp));
	  DECL_EXTERNAL (fn) = 1;
	  TREE_PUBLIC (fn) = 1;
	  DECL_ARTIFICIAL (fn) = 1;
	  pushdecl_top_level (fn);
	  make_function_rtl (fn);
	  pop_obstacks ();
	}

      mark_used (fn);
      e = expr_tree_cons (NULL_TREE, exp, expr_tree_cons
			  (NULL_TREE, throw_type, expr_tree_cons
			   (NULL_TREE, cleanup, NULL_TREE)));
      e = build_function_call (fn, e);
      expand_expr (e, const0_rtx, VOIDmode, 0);
    }
  else
    {
      /* rethrow current exception; note that it's no longer caught.  */

      tree fn = get_identifier ("__uncatch_exception");
      if (IDENTIFIER_GLOBAL_VALUE (fn))
	fn = IDENTIFIER_GLOBAL_VALUE (fn);
      else
	{
	  /* Declare void __uncatch_exception (void)
	     as defined in exception.cc. */
	  push_obstacks_nochange ();
	  end_temporary_allocation ();
	  fn = build_lang_decl (FUNCTION_DECL, fn,
				build_function_type (void_type_node,
						     void_list_node));
	  DECL_EXTERNAL (fn) = 1;
	  TREE_PUBLIC (fn) = 1;
	  DECL_ARTIFICIAL (fn) = 1;
	  pushdecl_top_level (fn);
	  make_function_rtl (fn);
	  pop_obstacks ();
	}

      mark_used (fn);
      exp = build_function_call (fn, NULL_TREE);
      expand_expr (exp, const0_rtx, VOIDmode, EXPAND_NORMAL);
    }

  expand_internal_throw ();
}

/* Build a throw expression.  */

tree
build_throw (e)
     tree e;
{
  if (e == error_mark_node)
    return e;

  if (processing_template_decl)
    return build_min (THROW_EXPR, void_type_node, e);

  if (e == null_node)
    cp_warning ("throwing NULL, which has integral, not pointer type");

  e = build1 (THROW_EXPR, void_type_node, e);
  TREE_SIDE_EFFECTS (e) = 1;
  TREE_USED (e) = 1;

  return e;
}