decl.c

gcc-2.95.3 Linux下最常用的C编译器

}

/* Exit a binding level.
   Pop the level off, and restore the state of the identifier-decl mappings
   that were in effect when this level was entered.

   If KEEP == 1, this level had explicit declarations, so
   and create a "block" (a BLOCK node) for the level
   to record its declarations and subblocks for symbol table output.

   If FUNCTIONBODY is nonzero, this level is the body of a function,
   so create a block as if KEEP were set and also clear out all
   label names.

   If REVERSE is nonzero, reverse the order of decls before putting
   them into the BLOCK.  */

tree
poplevel (keep, reverse, functionbody)
     int keep;
     int reverse;
     int functionbody;
{
  register tree link;
  /* The chain of decls was accumulated in reverse order.
     Put it into forward order, just for cleanliness.  */
  tree decls;
  int tmp = functionbody;
  int real_functionbody = current_binding_level->keep == 2
    ? ((functionbody = 0), tmp) : functionbody;
  tree tags = functionbody >= 0 ? current_binding_level->tags : 0;
  tree subblocks = functionbody >= 0 ? current_binding_level->blocks : 0;
  tree block = NULL_TREE;
  tree decl;
  int block_previously_created;
  int leaving_for_scope;

  if (current_binding_level->parm_flag == 2)
    return poplevel_class ();

  my_friendly_assert (!current_binding_level->class_shadowed,
		      19990414);

  /* We used to use KEEP == 2 to indicate that the new block should go
     at the beginning of the list of blocks at this binding level,
     rather than the end.  This hack is no longer used.  */
  my_friendly_assert (keep == 0 || keep == 1, 0);

  GNU_xref_end_scope ((HOST_WIDE_INT) current_binding_level,
		      (HOST_WIDE_INT) current_binding_level->level_chain,
		      current_binding_level->parm_flag,
		      current_binding_level->keep);

  if (current_binding_level->keep == 1)
    keep = 1;

  /* Get the decls in the order they were written.
     Usually current_binding_level->names is in reverse order.
     But parameter decls were previously put in forward order.  */

  if (reverse)
    current_binding_level->names
      = decls = nreverse (current_binding_level->names);
  else
    decls = current_binding_level->names;

  /* Output any nested inline functions within this block
     if they weren't already output.  */

  for (decl = decls; decl; decl = TREE_CHAIN (decl))
    if (TREE_CODE (decl) == FUNCTION_DECL
	&& ! TREE_ASM_WRITTEN (decl)
	&& DECL_INITIAL (decl) != NULL_TREE
	&& TREE_ADDRESSABLE (decl)
	&& decl_function_context (decl) == current_function_decl)
      {
	/* If this decl was copied from a file-scope decl
	   on account of a block-scope extern decl,
	   propagate TREE_ADDRESSABLE to the file-scope decl.  */
	if (DECL_ABSTRACT_ORIGIN (decl) != NULL_TREE)
	  TREE_ADDRESSABLE (DECL_ABSTRACT_ORIGIN (decl)) = 1;
	else
	  {
	    push_function_context ();
	    output_inline_function (decl);
	    pop_function_context ();
	  }
      }

  /* If there were any declarations or structure tags in that level,
     or if this level is a function body,
     create a BLOCK to record them for the life of this function.  */

  block = NULL_TREE;
  block_previously_created = (current_binding_level->this_block != NULL_TREE);
  if (block_previously_created)
    block = current_binding_level->this_block;
  else if (keep == 1 || functionbody)
    block = make_node (BLOCK);
  if (block != NULL_TREE)
    {
      if (block_previously_created)
	{
	  if (decls || tags || subblocks)
	    {
	      if (BLOCK_VARS (block) || BLOCK_TYPE_TAGS (block))
		warning ("internal compiler error: debugging info corrupted");

	      BLOCK_VARS (block) = decls;
	      BLOCK_TYPE_TAGS (block) = tags;

	      /* We can have previous subblocks and new subblocks when
		 doing fixup_gotos with complex cleanups.  We chain the new
		 subblocks onto the end of any pre-existing subblocks.  */
	      BLOCK_SUBBLOCKS (block) = chainon (BLOCK_SUBBLOCKS (block),
						 subblocks);
	    }
	  /* If we created the block earlier on, and we are just
	     diddling it now, then it already should have a proper
	     BLOCK_END_NOTE value associated with it.  */
	}
      else
	{
	  BLOCK_VARS (block) = decls;
	  BLOCK_TYPE_TAGS (block) = tags;
	  BLOCK_SUBBLOCKS (block) = subblocks;
	  /* Otherwise, for a new block, install a new BLOCK_END_NOTE
	     value.  */ 
	  remember_end_note (block);
	}
    }

  /* In each subblock, record that this is its superior.  */

  if (keep >= 0)
    for (link = subblocks; link; link = TREE_CHAIN (link))
      BLOCK_SUPERCONTEXT (link) = block;

  /* We still support the old for-scope rules, whereby the variables
     in a for-init statement were in scope after the for-statement
     ended.  We only use the new rules in flag_new_for_scope is
     nonzero.  */
  leaving_for_scope 
    = current_binding_level->is_for_scope && flag_new_for_scope == 1;

  /* Remove declarations for all the DECLs in this level.  */
  for (link = decls; link; link = TREE_CHAIN (link))
    {
      if (leaving_for_scope && TREE_CODE (link) == VAR_DECL)
	{
	  tree outer_binding 
	    = TREE_CHAIN (IDENTIFIER_BINDING (DECL_NAME (link)));
	  tree ns_binding;

	  if (!outer_binding)
	    ns_binding = IDENTIFIER_NAMESPACE_VALUE (DECL_NAME (link));
	  else
	    ns_binding = NULL_TREE;

	  if (outer_binding 
	      && (BINDING_LEVEL (outer_binding) 
		  == current_binding_level->level_chain))
	    /* We have something like:
	       
	         int i;
	         for (int i; ;);
		 
	       and we are leaving the `for' scope.  There's no reason to
	       keep the binding of the inner `i' in this case.  */
	    pop_binding (DECL_NAME (link), link);
	  else if ((outer_binding 
		    && (TREE_CODE (BINDING_VALUE (outer_binding)) 
			== TYPE_DECL))
		   || (ns_binding 
		       && TREE_CODE (ns_binding) == TYPE_DECL))
	    /* Here, we have something like:

		 typedef int I;

		 void f () {
		   for (int I; ;);
		 }

	       We must pop the for-scope binding so we know what's a
	       type and what isn't.  */
	    pop_binding (DECL_NAME (link), link);
	  else
	    {
	      /* Mark this VAR_DECL as dead so that we can tell we left it
		 there only for backward compatibility.  */
	      DECL_DEAD_FOR_LOCAL (link) = 1;
	      
	      /* Keep track of what should of have happenned when we
		 popped the binding.  */
	      if (outer_binding && BINDING_VALUE (outer_binding))
		DECL_SHADOWED_FOR_VAR (link) 
		  = BINDING_VALUE (outer_binding);

	      /* Add it to the list of dead variables in the next
		 outermost binding to that we can remove these when we
		 leave that binding.  */
	      current_binding_level->level_chain->dead_vars_from_for
		= tree_cons (NULL_TREE, link,
			     current_binding_level->level_chain->
			     dead_vars_from_for);

	      /* Although we don't pop the CPLUS_BINDING, we do clear
		 its BINDING_LEVEL since the level is going away now.  */
	      BINDING_LEVEL (IDENTIFIER_BINDING (DECL_NAME (link)))
		= 0;
	    }
	}
      else 
	{
	  /* Remove the binding.  */
	  decl = link;
	  if (TREE_CODE (decl) == TREE_LIST)
	    decl = TREE_VALUE (decl);
	  if (TREE_CODE_CLASS (TREE_CODE (decl)) == 'd')
	    pop_binding (DECL_NAME (decl), decl);
	  else if (TREE_CODE (decl) == OVERLOAD)
	    pop_binding (DECL_NAME (OVL_FUNCTION (decl)), decl);
	  else 
	    my_friendly_abort (0);
	}
    }

  /* Remove declarations for any `for' variables from inner scopes
     that we kept around.  */
  for (link = current_binding_level->dead_vars_from_for;
       link; link = TREE_CHAIN (link))
    pop_binding (DECL_NAME (TREE_VALUE (link)), TREE_VALUE (link));

  /* Restore the IDENTIFIER_TYPE_VALUEs.  */
  for (link = current_binding_level->type_shadowed;
       link; link = TREE_CHAIN (link))
    SET_IDENTIFIER_TYPE_VALUE (TREE_PURPOSE (link), TREE_VALUE (link));
  
  /* There may be OVERLOADs (wrapped in TREE_LISTs) on the BLOCK_VARs
     list if a `using' declaration put them there.  The debugging
     back-ends won't understand OVERLOAD, so we remove them here.
     Because the BLOCK_VARS are (temporarily) shared with
     CURRENT_BINDING_LEVEL->NAMES we must do this fixup after we have
     popped all the bindings.  */
  if (block)
    {
      tree* d;

      for (d = &BLOCK_VARS (block); *d; )
	{
	  if (TREE_CODE (*d) == TREE_LIST)
	    *d = TREE_CHAIN (*d);
	  else
	    d = &TREE_CHAIN (*d);
	}
    }

  /* If the level being exited is the top level of a function,
     check over all the labels.  */

  if (functionbody)
    {
      /* If this is the top level block of a function,
         the vars are the function's parameters.
         Don't leave them in the BLOCK because they are
         found in the FUNCTION_DECL instead.  */

      BLOCK_VARS (block) = 0;

      /* Clear out the definitions of all label names,
	 since their scopes end here.  */

      for (link = named_labels; link; link = TREE_CHAIN (link))
	{
	  register tree label = TREE_VALUE (link);

	  if (DECL_INITIAL (label) == NULL_TREE)
	    {
	      cp_error_at ("label `%D' used but not defined", label);
	      /* Avoid crashing later.  */
	      define_label (input_filename, 1, DECL_NAME (label));
	    }
	  else if (warn_unused && !TREE_USED (label))
	    cp_warning_at ("label `%D' defined but not used", label);
	  SET_IDENTIFIER_LABEL_VALUE (DECL_NAME (label), NULL_TREE);

          /* Put the labels into the "variables" of the
             top-level block, so debugger can see them.  */
          TREE_CHAIN (label) = BLOCK_VARS (block);
          BLOCK_VARS (block) = label;
	}

      named_labels = NULL_TREE;
    }

  /* Any uses of undefined labels now operate under constraints
     of next binding contour.  */
  {
    struct binding_level *level_chain;
    level_chain = current_binding_level->level_chain;
    if (level_chain)
      {
	struct named_label_list *labels;
	for (labels = named_label_uses; labels; labels = labels->next)
	  if (labels->binding_level == current_binding_level)
	    {
	      labels->binding_level = level_chain;
	      labels->names_in_scope = level_chain->names;
	    }
      }
  }

  tmp = current_binding_level->keep;

  pop_binding_level ();
  if (functionbody)
    DECL_INITIAL (current_function_decl) = block;
  else if (block)
    {
      if (!block_previously_created)
        current_binding_level->blocks
          = chainon (current_binding_level->blocks, block);
    }
  /* If we did not make a block for the level just exited,
     any blocks made for inner levels
     (since they cannot be recorded as subblocks in that level)
     must be carried forward so they will later become subblocks
     of something else.  */
  else if (subblocks)
    current_binding_level->blocks
      = chainon (current_binding_level->blocks, subblocks);

  /* Take care of compiler's internal binding structures.  */
  if (tmp == 2)
    {
      expand_end_bindings (getdecls (), keep, 1);
      /* Each and every BLOCK node created here in `poplevel' is important
	 (e.g. for proper debugging information) so if we created one
	 earlier, mark it as "used".  */
      if (block)
	TREE_USED (block) = 1;
      block = poplevel (keep, reverse, real_functionbody);
    }

  /* Each and every BLOCK node created here in `poplevel' is important
     (e.g. for proper debugging information) so if we created one
     earlier, mark it as "used".  */
  if (block)
    TREE_USED (block) = 1;
  return block;
}

/* Delete the node BLOCK from the current binding level.
   This is used for the block inside a stmt expr ({...})
   so that the block can be reinserted where appropriate.  */

void
delete_block (block)
     tree block;
{
  tree t;
  if (current_binding_level->blocks == block)
    current_binding_level->blocks = TREE_CHAIN (block);
  for (t = current_binding_level->blocks; t;)
    {
      if (TREE_CHAIN (t) == block)
	TREE_CHAIN (t) = TREE_CHAIN (block);
      else
	t = TREE_CHAIN (t);
    }
  TREE_CHAIN (block) = NULL_TREE;
  /* Clear TREE_USED which is always set by poplevel.
     The flag is set again if insert_block is called.  */
  TREE_USED (block) = 0;
}

/* Insert BLOCK at the end of the list of subblocks of the
   current binding level.  This is used when a BIND_EXPR is expanded,
   to handle the BLOCK node inside the BIND_EXPR.  */

void
insert_block (block)
     tree block;
{
  TREE_USED (block) = 1;
  current_binding_level->blocks
    = chainon (current_binding_level->blocks, block);
}

/* Set the BLOCK node for the innermost scope
   (the one we are currently in).  */

void
set_block (block)
    register tree block;
{
  current_binding_level->this_block = block;
}

/* Do a pushlevel for class declarations.  */

void
pushlevel_class ()
{
  register struct binding_level *newlevel;

  /* Reuse or create a struct for this binding level.  */
#if defined(DEBUG_CP_BINDING_LEVELS)
  if (0)
#else /* !defined(DEBUG_CP_BINDING_LEVELS) */
  if (free_binding_level)
#endif /* !defined(DEBUG_CP_BINDING_LEVELS) */
    {
      newlevel = free_binding_level;
      free_binding_level = free_binding_level->level_chain;
    }
  else
    newlevel = make_binding_level ();

#if defined(DEBUG_CP_BINDING_LEVELS)
  is_class_level = 1;
#endif /* defined(DEBUG_CP_BINDING_LEVELS) */

  push_binding_level (newlevel, 0, 0);

  decl_stack = push_decl_level (decl_stack, &decl_obstack);
  class_binding_level = current_binding_level;
  class_binding_level->parm_flag = 2;
}

/* ...and a poplevel for class declarations.  */

static tree
poplevel_class ()
{
  register struct binding_level *level = class_binding_level;
  tree shadowed;

  my_friendly_assert (level != 0, 354);