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 print_unreached = 1;
  23 static struct string_list *turn_off_names;
  24 static struct string_list *ignore_names;
  25
  26 static int empty_statement(struct statement *stmt)
  27 {
  28         if (!stmt)
  29                 return 0;
  30         if (stmt->type == STMT_EXPRESSION && !stmt->expression)
  31                 return 1;
  32         return 0;
  33 }
  34
  35 static int is_last_stmt(struct statement *cur_stmt)
  36 {
  37         struct symbol *fn = get_base_type(cur_func_sym);
  38         struct statement *stmt;
  39
  40         if (!fn)
  41                 return 0;
  42         stmt = fn->stmt;
  43         if (!stmt)
  44                 stmt = fn->inline_stmt;
  45         if (!stmt || stmt->type != STMT_COMPOUND)
  46                 return 0;
  47         stmt = last_ptr_list((struct ptr_list *)stmt->stmts);
  48         if (stmt == cur_stmt)
  49                 return 1;
  50         return 0;
  51 }
  52
  53 static void print_unreached_initializers(struct symbol_list *sym_list)
  54 {
  55         struct symbol *sym;
  56
  57         FOR_EACH_PTR(sym_list, sym) {
  58                 if (sym->initializer)
  59                         sm_msg("info: '%s' is not actually initialized (unreached code).",
  60                                 (sym->ident ? sym->ident->name : "this variable"));
  61         } END_FOR_EACH_PTR(sym);
  62 }
  63
  64 static int is_ignored_macro(struct statement *stmt)
  65 {
  66         char *name;
  67         char *tmp;
  68
  69         name = get_macro_name(stmt->pos);
  70         if (!name)
  71                 return 0;
  72
  73         FOR_EACH_PTR(ignore_names, tmp) {
  74                 if (strcmp(tmp, name) == 0)
  75                         return 1;
  76         } END_FOR_EACH_PTR(tmp);
  77
  78         return 0;
  79 }
  80
  81 static void unreachable_stmt(struct statement *stmt)
  82 {
  83
  84         if (__inline_fn)
  85                 return;
  86
  87         if (!__path_is_null()) {
  88                 print_unreached = 1;
  89                 return;
  90         }
  91         if (!print_unreached)
  92                 return;
  93
  94         switch (stmt->type) {
  95         case STMT_COMPOUND: /* after a switch before a case stmt */
  96         case STMT_RANGE:
  97         case STMT_CASE:
  98         case STMT_LABEL:
  99                 return;
 100         case STMT_DECLARATION: /* switch (x) { int a; case foo: ... */
 101                 print_unreached_initializers(stmt->declaration);
 102                 return;
 103         case STMT_RETURN: /* gcc complains if you don't have a return statement */
 104                 if (is_last_stmt(stmt))
 105                         return;
 106                 break;
 107         case STMT_GOTO:
 108                 /* people put extra breaks inside switch statements */
 109                 if (stmt->goto_label && stmt->goto_label->type == SYM_NODE &&
 110                     strcmp(stmt->goto_label->ident->name, "break") == 0)
 111                         return;
 112                 break;
 113         default:
 114                 break;
 115         }
 116         if (empty_statement(stmt))
 117                 return;
 118         if (is_ignored_macro(stmt))
 119                 return;
 120         if (!option_spammy)
 121                 return;
 122         sm_msg("info: ignoring unreachable code.");
 123         print_unreached = 0;
 124 }
 125
 126 static int is_turn_off(char *name)
 127 {
 128         char *tmp;
 129
 130         if (!name)
 131                 return 0;
 132
 133         FOR_EACH_PTR(turn_off_names, tmp) {
 134                 if (strcmp(tmp, name) == 0)
 135                         return 1;
 136         } END_FOR_EACH_PTR(tmp);
 137
 138         return 0;
 139 }
 140
 141 static char *get_function_name(struct statement *stmt)
 142 {
 143         struct expression *expr;
 144
 145         if (stmt->type != STMT_EXPRESSION)
 146                 return NULL;
 147         expr = stmt->expression;
 148         if (!expr || expr->type != EXPR_CALL)
 149                 return NULL;
 150         if (expr->fn->type != EXPR_SYMBOL || !expr->fn->symbol_name)
 151                 return NULL;
 152         return expr->fn->symbol_name->name;
 153 }
 154
 155 static void turn_off_unreachable(struct statement *stmt)
 156 {
 157         char *name;
 158
 159         name = get_macro_name(stmt->pos);
 160         if (is_turn_off(name)) {
 161                 print_unreached = 0;
 162                 return;
 163         }
 164
 165         if (stmt->type == STMT_IF &&
 166             known_condition_true(stmt->if_conditional) &&  __path_is_null()) {
 167                 print_unreached = 0;
 168                 return;
 169         }
 170
 171         name = get_function_name(stmt);
 172         if (is_turn_off(name))
 173                 print_unreached = 0;
 174 }
 175
 176 static void register_turn_off_macros(void)
 177 {
 178         struct token *token;
 179         char *macro;
 180         char name[256];
 181
 182         if (option_project == PROJ_NONE)
 183                 strcpy(name, "unreachable.turn_off");
 184         else
 185                 snprintf(name, 256, "%s.unreachable.turn_off", option_project_str);
 186
 187         token = get_tokens_file(name);
 188         if (!token)
 189                 return;
 190         if (token_type(token) != TOKEN_STREAMBEGIN)
 191                 return;
 192         token = token->next;
 193         while (token_type(token) != TOKEN_STREAMEND) {
 194                 if (token_type(token) != TOKEN_IDENT)
 195                         return;
 196                 macro = alloc_string(show_ident(token->ident));
 197                 add_ptr_list(&turn_off_names, macro);
 198                 token = token->next;
 199         }
 200         clear_token_alloc();
 201 }
 202
 203 static void register_ignored_macros(void)
 204 {
 205         struct token *token;
 206         char *macro;
 207         char name[256];
 208
 209         if (option_project == PROJ_NONE)
 210                 strcpy(name, "unreachable.ignore");
 211         else
 212                 snprintf(name, 256, "%s.unreachable.ignore", option_project_str);
 213
 214         token = get_tokens_file(name);
 215         if (!token)
 216                 return;
 217         if (token_type(token) != TOKEN_STREAMBEGIN)
 218                 return;
 219         token = token->next;
 220         while (token_type(token) != TOKEN_STREAMEND) {
 221                 if (token_type(token) != TOKEN_IDENT)
 222                         return;
 223                 macro = alloc_string(show_ident(token->ident));
 224                 add_ptr_list(&ignore_names, macro);
 225                 token = token->next;
 226         }
 227         clear_token_alloc();
 228 }
 229
 230 void check_unreachable(int id)
 231 {
 232         my_id = id;
 233
 234         register_turn_off_macros();
 235         register_ignored_macros();
 236         add_hook(&unreachable_stmt, STMT_HOOK);
 237         add_hook(&turn_off_unreachable, STMT_HOOK_AFTER);
 238 }