gcc/c/c-convert.c

   1 /* Language-level data type conversion for GNU C.
   2    Copyright (C) 1987-2017 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 3, or (at your option) any later
   9 version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING3.  If not see
  18 <http://www.gnu.org/licenses/>.  */
  19
  20
  21 /* This file contains the functions for converting C expressions
  22    to different data types.  The only entry point is `convert'.
  23    Every language front end must have a `convert' function
  24    but what kind of conversions it does will depend on the language.  */
  25
  26 #include "config.h"
  27 #include "system.h"
  28 #include "coretypes.h"
  29 #include "target.h"
  30 #include "c-tree.h"
  31 #include "convert.h"
  32 #include "langhooks.h"
  33 #include "ubsan.h"
  34 #include "asan.h"
  35
  36 /* Change of width--truncation and extension of integers or reals--
  37    is represented with NOP_EXPR.  Proper functioning of many things
  38    assumes that no other conversions can be NOP_EXPRs.
  39
  40    Conversion between integer and pointer is represented with CONVERT_EXPR.
  41    Converting integer to real uses FLOAT_EXPR
  42    and real to integer uses FIX_TRUNC_EXPR.
  43
  44    Here is a list of all the functions that assume that widening and
  45    narrowing is always done with a NOP_EXPR:
  46      In convert.c, convert_to_integer.
  47      In c-typeck.c, build_binary_op (boolean ops), and
  48         c_common_truthvalue_conversion.
  49      In expr.c: expand_expr, for operands of a MULT_EXPR.
  50      In fold-const.c: fold.
  51      In tree.c: get_narrower and get_unwidened.  */
  52 \f
  53 /* Subroutines of `convert'.  */
  54
  55
  56 \f
  57 /* Create an expression whose value is that of EXPR,
  58    converted to type TYPE.  The TREE_TYPE of the value
  59    is always TYPE.  This function implements all reasonable
  60    conversions; callers should filter out those that are
  61    not permitted by the language being compiled.  */
  62
  63 tree
  64 convert (tree type, tree expr)
  65 {
  66   tree e = expr;
  67   enum tree_code code = TREE_CODE (type);
  68   const char *invalid_conv_diag;
  69   tree ret;
  70   location_t loc = EXPR_LOCATION (expr);
  71
  72   if (type == error_mark_node
  73       || error_operand_p (expr))
  74     return error_mark_node;
  75
  76   if ((invalid_conv_diag
  77        = targetm.invalid_conversion (TREE_TYPE (expr), type)))
  78     {
  79       error (invalid_conv_diag);
  80       return error_mark_node;
  81     }
  82
  83   if (type == TREE_TYPE (expr))
  84     return expr;
  85   ret = targetm.convert_to_type (type, expr);
  86   if (ret)
  87       return ret;
  88
  89   STRIP_TYPE_NOPS (e);
  90
  91   if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr))
  92       && (TREE_CODE (TREE_TYPE (expr)) != COMPLEX_TYPE
  93           || TREE_CODE (e) == COMPLEX_EXPR))
  94     return fold_convert_loc (loc, type, expr);
  95   if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
  96     return error_mark_node;
  97   if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
  98     {
  99       error ("void value not ignored as it ought to be");
 100       return error_mark_node;
 101     }
 102
 103   switch (code)
 104     {
 105     case VOID_TYPE:
 106       return fold_convert_loc (loc, type, e);
 107
 108     case INTEGER_TYPE:
 109     case ENUMERAL_TYPE:
 110       if (sanitize_flags_p (SANITIZE_FLOAT_CAST)
 111           && TREE_CODE (TREE_TYPE (expr)) == REAL_TYPE
 112           && COMPLETE_TYPE_P (type))
 113         {
 114           expr = save_expr (expr);
 115           tree check = ubsan_instrument_float_cast (loc, type, expr);
 116           expr = fold_build1 (FIX_TRUNC_EXPR, type, expr);
 117           if (check == NULL_TREE)
 118             return expr;
 119           return fold_build2 (COMPOUND_EXPR, TREE_TYPE (expr), check, expr);
 120         }
 121       ret = convert_to_integer (type, e);
 122       goto maybe_fold;
 123
 124     case BOOLEAN_TYPE:
 125       return fold_convert_loc
 126         (loc, type, c_objc_common_truthvalue_conversion (input_location, expr));
 127
 128     case POINTER_TYPE:
 129     case REFERENCE_TYPE:
 130       ret = convert_to_pointer (type, e);
 131       goto maybe_fold;
 132
 133     case REAL_TYPE:
 134       ret = convert_to_real (type, e);
 135       goto maybe_fold;
 136
 137     case FIXED_POINT_TYPE:
 138       ret = convert_to_fixed (type, e);
 139       goto maybe_fold;
 140
 141     case COMPLEX_TYPE:
 142       ret = convert_to_complex (type, e);
 143       goto maybe_fold;
 144
 145     case VECTOR_TYPE:
 146       ret = convert_to_vector (type, e);
 147       goto maybe_fold;
 148
 149     case RECORD_TYPE:
 150     case UNION_TYPE:
 151       if (lang_hooks.types_compatible_p (type, TREE_TYPE (expr)))
 152         return e;
 153       break;
 154
 155     default:
 156       break;
 157
 158     maybe_fold:
 159       if (TREE_CODE (ret) != C_MAYBE_CONST_EXPR)
 160         ret = fold (ret);
 161       return ret;
 162     }
 163
 164   error ("conversion to non-scalar type requested");
 165   return error_mark_node;
 166 }