check_all_func_returns.c

   1 /*
   2  * Copyright 2018 Joyent, Inc.
   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 /*
  19  * Like lint of old, check that every return value from every function is used.
  20  * Casting to (void) will silence this check.
  21  */
  22
  23 #include "smatch.h"
  24 #include "smatch_slist.h"
  25
  26 static void check_func_return(struct expression *expr)
  27 {
  28         struct symbol *sym = get_real_base_type(get_type(expr->fn));
  29         const char *func = expr_to_str(expr->fn);
  30         struct statement *stmt;
  31
  32         if (sym == NULL) {
  33                 sm_error("unknown type for func '%s'", func);
  34                 return;
  35         }
  36
  37         if (expr->type != EXPR_CALL) {
  38                 sm_error("func '%s' is not a call site", func);
  39                 return;
  40         }
  41
  42         /*
  43          * There is never any need to check these returns.
  44          */
  45         if (strcmp(func, "memcpy") == 0 ||
  46             strcmp(func, "memmove") == 0 ||
  47             strcmp(func, "memset") == 0)
  48                 return;
  49
  50         /*
  51          * Closer to a policy here, but there seems very few cases where it's
  52          * useful to check the return value of the standard printf() family
  53          * outputting to stdout or stderr.
  54          */
  55         if (strcmp(func, "printf") == 0 || strcmp(func, "vprintf") == 0)
  56                 return;
  57
  58         if (strcmp(func, "fprintf") == 0 || strcmp(func, "vfprintf") == 0) {
  59                 const char *arg0 = expr_to_str(get_argument_from_call_expr(expr->args, 0));
  60
  61                 if (arg0 != NULL &&
  62                     (strcmp(arg0, "(&__iob[1])") == 0 ||
  63                     strcmp(arg0, "(&__iob[2])") == 0))
  64                         return;
  65         }
  66
  67         /*
  68          * Either we got the return type already (direct call),
  69          * or we need to go one further (function pointer call)
  70          */
  71         if (sym == &void_ctype || (sym->type == SYM_FN &&
  72                 get_real_base_type(sym) == &void_ctype))
  73                 return;
  74
  75         stmt = last_ptr_list((struct ptr_list *)big_statement_stack);
  76
  77         if (stmt && stmt->type == STMT_EXPRESSION && stmt->expression == expr)
  78                 sm_error("unchecked function return '%s'", expr_to_str(expr->fn));
  79 }
  80
  81 void check_all_func_returns(int id)
  82 {
  83         if (option_project != PROJ_ILLUMOS_KERNEL &&
  84             option_project != PROJ_ILLUMOS_USER)
  85                 return;
  86
  87         add_hook(&check_func_return, FUNCTION_CALL_HOOK);
  88 }