check_unreachable.c

   1 /*
   2  * Copyright (C) 2014 Oracle.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version 2
   7  * of the License, or (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
  16  */
  17
  18 #include "smatch.h"
  19
  20 static int my_id;
  21
  22 static int empty_statement(struct statement *stmt)
  23 {
  24         if (!stmt)
  25                 return 0;
  26         if (stmt->type == STMT_EXPRESSION && !stmt->expression)
  27                 return 1;
  28         return 0;
  29 }
  30
  31 static int is_last_stmt(struct statement *cur_stmt)
  32 {
  33         struct symbol *fn = get_base_type(cur_func_sym);
  34         struct statement *stmt;
  35
  36         if (!fn)
  37                 return 0;
  38         stmt = fn->stmt;
  39         if (!stmt)
  40                 stmt = fn->inline_stmt;
  41         if (!stmt || stmt->type != STMT_COMPOUND)
  42                 return 0;
  43         stmt = last_ptr_list((struct ptr_list *)stmt->stmts);
  44         if (stmt == cur_stmt)
  45                 return 1;
  46         return 0;
  47 }
  48
  49 static void print_unreached_initializers(struct symbol_list *sym_list)
  50 {
  51         struct symbol *sym;
  52
  53         FOR_EACH_PTR(sym_list, sym) {
  54                 if (sym->initializer)
  55                         sm_msg("info: '%s' is not actually initialized (unreached code).",
  56                                 (sym->ident ? sym->ident->name : "this variable"));
  57         } END_FOR_EACH_PTR(sym);
  58 }
  59
  60 static void print_unreached(struct statement *stmt)
  61 {
  62         static int print = 1;
  63
  64         if (__inline_fn)
  65                 return;
  66
  67         if (!__path_is_null()) {
  68                 print = 1;
  69                 return;
  70         }
  71         if (!print)
  72                 return;
  73
  74         switch (stmt->type) {
  75         case STMT_COMPOUND: /* after a switch before a case stmt */
  76         case STMT_RANGE:
  77         case STMT_CASE:
  78         case STMT_LABEL:
  79                 return;
  80         case STMT_DECLARATION: /* switch (x) { int a; case foo: ... */
  81                 print_unreached_initializers(stmt->declaration);
  82                 return;
  83         case STMT_RETURN: /* gcc complains if you don't have a return statement */
  84                 if (is_last_stmt(stmt))
  85                         return;
  86                 break;
  87         case STMT_GOTO:
  88                 /* people put extra breaks inside switch statements */
  89                 if (stmt->goto_label && stmt->goto_label->type == SYM_NODE &&
  90                     strcmp(stmt->goto_label->ident->name, "break") == 0)
  91                         return;
  92                 break;
  93         default:
  94                 break;
  95         }
  96         if (empty_statement(stmt))
  97                 return;
  98         if (!option_spammy)
  99                 return;
 100         sm_msg("info: ignoring unreachable code.");
 101         print = 0;
 102 }
 103
 104 void check_unreachable(int id)
 105 {
 106         my_id = id;
 107
 108         add_hook(&print_unreached, STMT_HOOK);
 109 }