except.c

gcc库的原代码,对编程有很大帮助.

    return NULL_RTX;
  }

  /* These are saved for the exception table.  */
  push_rtl_perm ();
  entry->start_label = gen_label_rtx ();
  entry->end_label = gen_label_rtx ();
  entry->exception_handler_label = gen_label_rtx ();
  pop_rtl_from_perm ();

  LABEL_PRESERVE_P (entry->start_label) = 1;
  LABEL_PRESERVE_P (entry->end_label) = 1;
  LABEL_PRESERVE_P (entry->exception_handler_label) = 1;

  entry->finalization = NULL_TREE;
  entry->context = current_function_decl;

  node->entry = entry;
  node->chain = stack->top;
  stack->top = node;

  enqueue_eh_entry (&eh_table_output_queue, copy_eh_entry (entry));

  return entry->start_label;
}

static struct ehEntry *
pop_eh_entry (stack)
     struct ehStack *stack;
{
  struct ehNode *tempnode;
  struct ehEntry *tempentry;

  if (stack && (tempnode = stack->top)) {
    tempentry = tempnode->entry;
    stack->top = stack->top->chain;
    free (tempnode);

    return tempentry;
  }

  return NULL;
}

static struct ehEntry *
copy_eh_entry (entry)
     struct ehEntry *entry;
{
  struct ehEntry *newentry;

  newentry = (struct ehEntry*)xmalloc (sizeof (struct ehEntry));
  memcpy ((void*)newentry, (void*)entry, sizeof (struct ehEntry));

  return newentry;
}

static void
enqueue_eh_entry (queue, entry)
     struct ehQueue *queue;
     struct ehEntry *entry;
{
  struct ehNode *node = (struct ehNode*)xmalloc (sizeof (struct ehNode));

  node->entry = entry;
  node->chain = NULL;

  if (queue->head == NULL)
    {
      queue->head = node;
    }
  else
    {
      queue->tail->chain = node;
    }
  queue->tail = node;
}

static struct ehEntry *
dequeue_eh_entry (queue)
     struct ehQueue *queue;
{
  struct ehNode *tempnode;
  struct ehEntry *tempentry;

  if (queue->head == NULL)
    return NULL;

  tempnode = queue->head;
  queue->head = queue->head->chain;

  tempentry = tempnode->entry;
  free (tempnode);

  return tempentry;
}

static void
new_eh_queue (queue)
     struct ehQueue *queue;
{
  queue->head = queue->tail = NULL;
}

static void
new_eh_stack (stack)
     struct ehStack *stack;
{
  stack->top = NULL;
}

/* cheesyness to save some typing. returns the return value rtx */
rtx
do_function_call (func, params, return_type)
     tree func, params, return_type;
{
  tree func_call;
  func_call = build_function_call (func, params);
  expand_call (func_call, NULL_RTX, 0);
  if (return_type != NULL_TREE)
    return hard_function_value (return_type, func_call);
  return NULL_RTX;
}

static void
expand_internal_throw (pc)
     rtx pc;
{
  tree params;

  emit_move_insn (DECL_RTL (saved_pc), pc);
#ifdef JUMP_TO_THROW
  emit_indirect_jump (gen_rtx (SYMBOL_REF, Pmode, "__throw"));
#else
  do_function_call (Throw, NULL_TREE, NULL_TREE);
#endif
  throw_used = 1;
}

/* ========================================================================= */

void
lang_interim_eh (finalization)
     tree finalization;
{
  if (finalization)
    end_protect (finalization);
  else
    start_protect ();
}

extern tree auto_function PROTO((tree, tree, enum built_in_function));

/* sets up all the global eh stuff that needs to be initialized at the
   start of compilation.

   This includes:
		- Setting up all the function call trees
		- Initializing the ehqueue
		- Initializing the eh_table_output_queue
		- Initializing the ehstack
*/

void
init_exception_processing ()
{
  extern tree define_function ();
  tree unexpected_fndecl, terminate_fndecl;
  tree set_unexpected_fndecl, set_terminate_fndecl;
  tree catch_match_fndecl;
  tree find_first_exception_match_fndecl;
  tree unwind_fndecl;
  tree declspecs;
  tree d;

  /* void (*)() */
  tree PFV = build_pointer_type (build_function_type
				 (void_type_node, void_list_node));

  /* arg list for the build_function_type call for set_terminate () and
     set_unexpected () */
  tree pfvlist = tree_cons (NULL_TREE, PFV, void_list_node);

  /* void (*pfvtype (void (*) ()))() */
  tree pfvtype = build_function_type (PFV, pfvlist);

  /* void vtype () */
  tree vtype = build_function_type (void_type_node, void_list_node);
  
  set_terminate_fndecl = auto_function (get_identifier ("set_terminate"),
					pfvtype, NOT_BUILT_IN);
  set_unexpected_fndecl = auto_function (get_identifier ("set_unexpected"),
					 pfvtype, NOT_BUILT_IN);
  unexpected_fndecl = auto_function (get_identifier ("unexpected"),
				     vtype, NOT_BUILT_IN);
  terminate_fndecl = auto_function (get_identifier ("terminate"),
				    vtype, NOT_BUILT_IN);

  interim_eh_hook = lang_interim_eh;

  push_lang_context (lang_name_c);

  catch_match_fndecl =
    define_function (flag_rtti
		     ? "__throw_type_match_rtti"
		     : "__throw_type_match",
		     build_function_type (ptr_type_node,
					  tree_cons (NULL_TREE, ptr_type_node,
						     tree_cons (NULL_TREE, ptr_type_node,
								tree_cons (NULL_TREE, ptr_type_node,
									   void_list_node)))),
		     NOT_BUILT_IN,
		     pushdecl,
		     0);
  find_first_exception_match_fndecl =
    define_function ("__find_first_exception_table_match",
		     build_function_type (ptr_type_node,
					  tree_cons (NULL_TREE, ptr_type_node,
						     void_list_node)),
		     NOT_BUILT_IN,
		     pushdecl,
		     0);
  unwind_fndecl =
    define_function ("__unwind_function",
		     build_function_type (void_type_node,
					  tree_cons (NULL_TREE, ptr_type_node,
						     void_list_node)),
		     NOT_BUILT_IN,
		     pushdecl,
		     0);
  throw_fndecl =
    define_function ("__throw",
		     build_function_type (void_type_node, void_list_node),
		     NOT_BUILT_IN,
		     pushdecl,
		     0);
  DECL_EXTERNAL (throw_fndecl) = 0;
  TREE_PUBLIC (throw_fndecl) = 0;

  Unexpected = default_conversion (unexpected_fndecl);
  Terminate = default_conversion (terminate_fndecl);
  SetTerminate = default_conversion (set_terminate_fndecl);
  SetUnexpected = default_conversion (set_unexpected_fndecl);
  CatchMatch = default_conversion (catch_match_fndecl);
  FirstExceptionMatch = default_conversion (find_first_exception_match_fndecl);
  Unwind = default_conversion (unwind_fndecl);
  Throw = default_conversion (throw_fndecl);
  BuiltinReturnAddress = default_conversion (builtin_return_address_fndecl);

  TerminateFunctionCall = build_function_call (Terminate, NULL_TREE);

  pop_lang_context ();

  new_eh_queue (&ehqueue);
  new_eh_queue (&eh_table_output_queue);
  new_eh_stack (&ehstack);

  declspecs = tree_cons (NULL_TREE, get_identifier ("void"), NULL_TREE);
  d = build_parse_node (INDIRECT_REF, get_identifier ("__eh_pc"));
  d = start_decl (d, declspecs, 0, NULL_TREE);
  DECL_COMMON (d) = 1;
  cp_finish_decl (d, NULL_TREE, NULL_TREE, 0, 0);
  saved_pc = lookup_name (get_identifier ("__eh_pc"), 0);

  declspecs = tree_cons (NULL_TREE, get_identifier ("void"), NULL_TREE);
  d = build_parse_node (INDIRECT_REF, get_identifier ("__eh_type"));
  d = start_decl (d, declspecs, 0, NULL_TREE);
  DECL_COMMON (d) = 1;
  cp_finish_decl (d, NULL_TREE, NULL_TREE, 0, 0);
  saved_throw_type = lookup_name (get_identifier ("__eh_type"), 0);

  declspecs = tree_cons (NULL_TREE, get_identifier ("void"), NULL_TREE);
  d = build_parse_node (INDIRECT_REF, get_identifier ("__eh_value"));
  d = start_decl (d, declspecs, 0, NULL_TREE);
  DECL_COMMON (d) = 1;
  cp_finish_decl (d, NULL_TREE, NULL_TREE, 0, 0);
  saved_throw_value = lookup_name (get_identifier ("__eh_value"), 0);
}

/* call this to begin a block of unwind protection (ie: when an object is
   constructed) */
void
start_protect ()
{
  if (! doing_eh (0))
    return;

  emit_label (push_eh_entry (&ehstack));
}
   
/* call this to end a block of unwind protection.  the finalization tree is
   the finalization which needs to be run in order to cleanly unwind through
   this level of protection. (ie: call this when a scope is exited)*/
void
end_protect (finalization)
     tree finalization;
{
  struct ehEntry *entry;

  if (! doing_eh (0))
    return;

  entry = pop_eh_entry (&ehstack);

  emit_label (entry->end_label);
  /* Put in something that takes up space, as otherwise the end
     address for the EH region could have the exact same address as
     the outer region, causing us to miss the fact that resuming
     exception handling with this PC value would be inside the outer
     region.  */
  emit_insn (gen_nop ());

  entry->finalization = finalization;

  enqueue_eh_entry (&ehqueue, entry);
}

/* call this on start of a try block. */
void
expand_start_try_stmts ()
{
  if (! doing_eh (1))
    return;

  start_protect ();
}

void
expand_end_try_stmts ()
{
  end_protect (integer_zero_node);
}


/* call this to start processing of all the catch blocks. */
void
expand_start_all_catch ()
{
  struct ehEntry *entry;
  rtx label;

  if (! doing_eh (1))
    return;

  emit_line_note (input_filename, lineno);
  label = gen_label_rtx ();

  /* The label for the exception handling block we will save.  This is
     Lresume, in the documention.  */
  emit_label (label);
  
  /* Put in something that takes up space, as otherwise the end
     address for the EH region could have the exact same address as
     the outer region, causing us to miss the fact that resuming
     exception handling with this PC value would be inside the outer
     region.  */
  emit_insn (gen_nop ());

  push_label_entry (&caught_return_label_stack, label);

  /* Start a new sequence for all the catch blocks.  We will add this
     to the gloabl sequence catch_clauses, when we have completed all
     the handlers in this handler-seq.  */
  start_sequence ();

  while (1)
    {
      entry = dequeue_eh_entry (&ehqueue);
      emit_label (entry->exception_handler_label);

      expand_expr (entry->finalization, const0_rtx, VOIDmode, 0);

      /* When we get down to the matching entry, stop.  */
      if (entry->finalization == integer_zero_node)
	break;

      /* The below can be optimized away, and we could just fall into the
	 next EH handler, if we are certain they are nested.  */
      /* Code to throw out to outer context, if we fall off end of the
	 handler.  */
      expand_internal_throw (gen_rtx (LABEL_REF,
				      Pmode,
				      entry->end_label));
      free (entry);
    }
}

/* call this to end processing of all the catch blocks. */
void
expand_end_all_catch ()
{
  rtx new_catch_clause;

  if (! doing_eh (1))
    return;

  /* Code to throw out to outer context, if we fall off end of catch
     handlers.  This is rethrow (Lresume, same id, same obj); in the
     documentation.  */
  expand_internal_throw (gen_rtx (LABEL_REF,
				  Pmode,
				  top_label_entry (&caught_return_label_stack)));

  /* Now we have the complete catch sequence.  */
  new_catch_clause = get_insns ();
  end_sequence ();
  
  /* this level of catch blocks is done, so set up the successful catch jump
     label for the next layer of catch blocks. */
  pop_label_entry (&caught_return_label_stack);

  /* Add the new sequence of catchs to the main one for this
     function.  */
  push_to_sequence (catch_clauses);
  emit_insns (new_catch_clause);
  catch_clauses = get_insns ();
  end_sequence ();
  
  /* Here we fall through into the continuation code.  */
}

/* Build a type value for use at runtime for a type that is matched
   against by the exception handling system.  */
static tree