check-init.c

gcc-2.95.3 Linux下最常用的C编译器

}

/* Check for (un)initialized local variables in EXP.
*/

static void
check_init (exp, before)
     tree exp;
     words before;
{
  tree tmp;
 again:
  switch (TREE_CODE (exp))
    {
    case VAR_DECL:
      if (! FIELD_STATIC (exp) && DECL_NAME (exp) != NULL_TREE)
	{
	  int index = DECL_BIT_INDEX (exp);
	  if (index >= 0 && ! SET_P (before, index))
	    {
#if 1
	      parse_error_context (wfl,
				   "Variable `%s' may not have been initialized"
				   , IDENTIFIER_POINTER (DECL_NAME (exp)));
#else
	      error_with_decl (exp, "variable may be used uninitialized");
#endif
	      /* Suppress further errors. */
	      DECL_BIT_INDEX (exp) = -1;
	    }
	}
      break;
    case MODIFY_EXPR:
      tmp = TREE_OPERAND (exp, 0);
      if (TREE_CODE (tmp) == VAR_DECL && ! FIELD_STATIC (tmp))
	{
	  int index;
	  check_init (TREE_OPERAND (exp, 1), before);
	  index = DECL_BIT_INDEX (tmp);
	  if (index >= 0)
	    SET_BIT (before, index);
	  /* Minor optimization.  See comment for start_current_locals. */
	  if (index >= start_current_locals
	      && index == num_current_locals - 1)
	    {
	      num_current_locals--;
	      DECL_BIT_INDEX (tmp) = -1;
	    }
	 break;
       }
     else
       goto binop;
    case BLOCK:
      if (BLOCK_EXPR_BODY (exp))
	{
	  tree decl = BLOCK_EXPR_DECLS (exp);
	  int words_needed;
	  word* tmp;
	  int i;
	  int save_start_current_locals = start_current_locals;
	  int save_num_current_words = num_current_words;
	  start_current_locals = num_current_locals;
	  for (;  decl != NULL_TREE;  decl = TREE_CHAIN (decl))
	    {
	      DECL_BIT_INDEX (decl) = num_current_locals++;
	    }
	  words_needed = WORDS_NEEDED (num_current_locals);
	  if (words_needed > num_current_words)
	    {
	      tmp = ALLOC_WORDS (words_needed);
	      COPY (tmp, before);
	      num_current_words = words_needed;
	    }
	  else
	    tmp = before;
	  for (i = start_current_locals;  i < num_current_locals;  i++)
	    CLEAR_BIT (tmp, i);
	  check_init (BLOCK_EXPR_BODY (exp), tmp);
	  num_current_locals = start_current_locals;
	  start_current_locals = save_start_current_locals;
	  if (tmp != before)
	    {
	      num_current_words = save_num_current_words;
	      COPY (before, tmp);
	      FREE_WORDS (tmp);
	    }
	}
      break;
    case LOOP_EXPR:
      {
	struct alternatives alt;
	BEGIN_ALTERNATIVES (before, alt);
	alt.block = exp;
	check_init (TREE_OPERAND (exp, 0), before);
	done_alternative (before, &alt);
	END_ALTERNATIVES (before, alt);
	return;
      }
    case EXIT_EXPR:
      {
	struct alternatives *alt = alternatives;
	words tmp = ALLOC_WORDS (2 * num_current_words);
	words when_true = tmp;
	words when_false = tmp + num_current_words;
#ifdef ENABLE_CHECKING
	if (TREE_CODE (alt->block) != LOOP_EXPR)
	  fatal ("internal error in check-init:  EXIT_EXPR not in LOOP_EXPR");
#endif
	check_bool_init (TREE_OPERAND (exp, 0), before, when_false, when_true);
	done_alternative (when_true, alt);
	COPY (before, when_false);
	FREE_WORDS (tmp);
	return;
      }
    case LABELED_BLOCK_EXPR:
      {
	struct alternatives alt;
	BEGIN_ALTERNATIVES (before, alt);
	alt.block = exp;
	if (LABELED_BLOCK_BODY (exp))
	  check_init (LABELED_BLOCK_BODY (exp), before);
	done_alternative (before, &alt);
	END_ALTERNATIVES (before, alt);
	return;
      }
    case EXIT_BLOCK_EXPR:
      {
	tree block = TREE_OPERAND (exp, 0);
	struct alternatives *alt = alternatives;
	while (alt->block != block)
	  alt = alt->outer;
	done_alternative (before, alt);
	SET_ALL (before);
	return;
      }
    case SWITCH_EXPR:
      {
	struct alternatives alt;
	check_init (TREE_OPERAND (exp, 0), before);
	BEGIN_ALTERNATIVES (before, alt);
	alt.saved = ALLOC_WORDS (num_current_words);
	COPY (alt.saved, before);
	alt.block = exp;
	check_init (TREE_OPERAND (exp, 1), before);
	done_alternative (before, &alt);
	FREE_WORDS (alt.saved);
	END_ALTERNATIVES (before, alt);
	return;
      }
    case CASE_EXPR:
    case DEFAULT_EXPR:
      {
	int i;
	struct alternatives *alt = alternatives;
	while (TREE_CODE (alt->block) != SWITCH_EXPR)
	  alt = alt->outer;
	COPYN (before, alt->saved, WORDS_NEEDED (alt->num_locals));
	for (i = alt->num_locals;  i < num_current_locals;  i++)
	  CLEAR_BIT (before, i);
	break;
      }

    case CLEANUP_POINT_EXPR:
      {
	struct alternatives alt;
	BEGIN_ALTERNATIVES (before, alt);
	CLEAR_ALL (alt.combined);
	check_init (TREE_OPERAND (exp, 0), before); 
	UNION (alt.combined, alt.combined, before);
	END_ALTERNATIVES (before, alt);
      }
      return;
    case WITH_CLEANUP_EXPR:
      {
	struct alternatives *alt = alternatives;	
#ifdef ENABLE_CHECKING
	if (TREE_CODE (alt->block) != CLEANUP_POINT_EXPR)
	  fatal ("internal error in check-init:  WITH_CLEANUP_EXPR not in CLEANUP_POINT_EXPR");
#endif
	check_init (TREE_OPERAND (exp, 0), before);
	UNION (alt->combined, alt->combined, before);
	check_init (TREE_OPERAND (exp, 2), alt->combined);
	return;
      }

    case TRY_EXPR:
      {
	tree try_clause = TREE_OPERAND (exp, 0);
	tree clause = TREE_OPERAND (exp, 1);
	words save = ALLOC_WORDS (num_current_words);
	words tmp = ALLOC_WORDS (num_current_words);
	struct alternatives alt;
	BEGIN_ALTERNATIVES (before, alt);
	COPY (save, before);
	COPY (tmp, save);
	check_init (try_clause, tmp);
	done_alternative (tmp, &alt);
	for ( ; clause != NULL_TREE;  clause = TREE_CHAIN (clause))
	  {
	    tree catch_clause = TREE_OPERAND (clause, 0);
	    COPY (tmp, save);
	    check_init (catch_clause, tmp);
	    done_alternative (tmp, &alt);
	  }
	FREE_WORDS (tmp);
	FREE_WORDS (save);
	END_ALTERNATIVES (before, alt);
      }
    return;

    case TRY_FINALLY_EXPR:
      {
	words tmp = ALLOC_WORDS (num_current_words);
	COPY (tmp, before);
	check_init (TREE_OPERAND (exp, 0), tmp);
	check_init (TREE_OPERAND (exp, 1), before);
	FREE_WORDS (tmp);
      }
      return;

    case RETURN_EXPR:
    case THROW_EXPR:
      if (TREE_OPERAND (exp, 0))
	check_init (TREE_OPERAND (exp, 0), before);
      goto never_continues;

    case ERROR_MARK:
    never_continues:
      SET_ALL (before);
      return;
      
    case COND_EXPR:
    case TRUTH_ANDIF_EXPR:
    case TRUTH_ORIF_EXPR:
      {
	words tmp = ALLOC_WORDS (2 * num_current_words);
	words when_true = tmp;
	words when_false = tmp + num_current_words;
	check_bool_init (exp, before, when_false, when_true);
	INTERSECT (before, when_false, when_true);
	FREE_WORDS (tmp);
      }
      break;
    case UNARY_PLUS_EXPR:
    case NEGATE_EXPR:
    case TRUTH_AND_EXPR:
    case TRUTH_OR_EXPR:
    case TRUTH_XOR_EXPR:
    case TRUTH_NOT_EXPR:
    case BIT_NOT_EXPR:
    case CONVERT_EXPR:
    case COMPONENT_REF:
    case NOP_EXPR:
    case FLOAT_EXPR:
    case FIX_TRUNC_EXPR:
    case INDIRECT_REF:
    case ADDR_EXPR:
    case SAVE_EXPR:
    case PREDECREMENT_EXPR:
    case PREINCREMENT_EXPR:
    case POSTDECREMENT_EXPR:
    case POSTINCREMENT_EXPR:
    case NON_LVALUE_EXPR:
    case INSTANCEOF_EXPR:
      /* Avoid needless recursion. */
      exp = TREE_OPERAND (exp, 0);
      goto again;

    case COMPOUND_EXPR:
    case PLUS_EXPR:
    case MINUS_EXPR:
    case MULT_EXPR:
    case TRUNC_DIV_EXPR:
    case TRUNC_MOD_EXPR:
    case RDIV_EXPR:
    case LSHIFT_EXPR:
    case RSHIFT_EXPR:
    case URSHIFT_EXPR:
    case BIT_AND_EXPR:
    case BIT_XOR_EXPR:
    case BIT_IOR_EXPR:
    case EQ_EXPR: 
    case NE_EXPR:
    case GT_EXPR:
    case GE_EXPR:
    case LT_EXPR:
    case LE_EXPR:
    case ARRAY_REF:
    binop:
      check_init (TREE_OPERAND (exp, 0), before);
      /* Avoid needless recursion, especially for COMPOUND_EXPR. */
      exp = TREE_OPERAND (exp, 1);
      goto again;

    case PARM_DECL:
    case RESULT_DECL:
    case FUNCTION_DECL:
    case INTEGER_CST:
    case REAL_CST:
    case STRING_CST:
      break;

    case NEW_CLASS_EXPR:
    case CALL_EXPR:
      {
	tree func = TREE_OPERAND (exp, 0);
	tree x = TREE_OPERAND (exp, 1);
	if (TREE_CODE (func) == ADDR_EXPR)
	  func = TREE_OPERAND (func, 0);
	check_init (func, before);

	for ( ;  x != NULL_TREE;  x = TREE_CHAIN (x))
	  check_init (TREE_VALUE (x), before);
	if (func == throw_node)
	  goto never_continues;
      }
      break;

    case NEW_ARRAY_INIT:
      {
	tree x = CONSTRUCTOR_ELTS (TREE_OPERAND (exp, 0));
	for ( ;  x != NULL_TREE;  x = TREE_CHAIN (x))
	  check_init (TREE_VALUE (x), before);
      }
      break;

    case EXPR_WITH_FILE_LOCATION:
      {
	char *saved_input_filename = input_filename;
	tree saved_wfl = wfl;
	tree body = EXPR_WFL_NODE (exp);
	int saved_lineno = lineno;
	if (body == empty_stmt_node)
	  break;
	wfl = exp;
	input_filename = EXPR_WFL_FILENAME (exp);
	lineno = EXPR_WFL_LINENO (exp);
	check_init (body, before);
	input_filename = saved_input_filename;
	lineno = saved_lineno;
	wfl = saved_wfl;
      }
      break;
      
    default:
      fatal ("internal error in check-init: tree code not implemented: %s",
	    tree_code_name [(int) TREE_CODE (exp)]);
    }
}

void
check_for_initialization (body)
     tree body;
{
  word before = 0;
  check_init (body, &before);
}