gcc/c/c-convert.c

   1 /* Language-level data type conversion for GNU C.
   2    Copyright (C) 1987-2015 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 "tm.h"
  30 #include "hash-set.h"
  31 #include "vec.h"
  32 #include "symtab.h"
  33 #include "input.h"
  34 #include "alias.h"
  35 #include "double-int.h"
  36 #include "machmode.h"
  37 #include "inchash.h"
  38 #include "tree.h"
  39 #include "flags.h"
  40 #include "convert.h"
  41 #include "c-family/c-common.h"
  42 #include "c-tree.h"
  43 #include "langhooks.h"
  44 #include "target.h"
  45 #include "ubsan.h"
  46
  47 /* Change of width--truncation and extension of integers or reals--
  48    is represented with NOP_EXPR.  Proper functioning of many things
  49    assumes that no other conversions can be NOP_EXPRs.
  50
  51    Conversion between integer and pointer is represented with CONVERT_EXPR.
  52    Converting integer to real uses FLOAT_EXPR
  53    and real to integer uses FIX_TRUNC_EXPR.
  54
  55    Here is a list of all the functions that assume that widening and
  56    narrowing is always done with a NOP_EXPR:
  57      In convert.c, convert_to_integer.
  58      In c-typeck.c, build_binary_op (boolean ops), and
  59         c_common_truthvalue_conversion.
  60      In expr.c: expand_expr, for operands of a MULT_EXPR.
  61      In fold-const.c: fold.
  62      In tree.c: get_narrower and get_unwidened.  */
  63 \f
  64 /* Subroutines of `convert'.  */
  65
  66
  67 \f
  68 /* Create an expression whose value is that of EXPR,
  69    converted to type TYPE.  The TREE_TYPE of the value
  70    is always TYPE.  This function implements all reasonable
  71    conversions; callers should filter out those that are
  72    not permitted by the language being compiled.  */
  73
  74 tree
  75 convert (tree type, tree expr)
  76 {
  77   tree e = expr;
  78   enum tree_code code = TREE_CODE (type);
  79   const char *invalid_conv_diag;
  80   tree ret;
  81   location_t loc = EXPR_LOCATION (expr);
  82
  83   if (type == error_mark_node
  84       || error_operand_p (expr))
  85     return error_mark_node;
  86
  87   if ((invalid_conv_diag
  88        = targetm.invalid_conversion (TREE_TYPE (expr), type)))
  89     {
  90       error (invalid_conv_diag);
  91       return error_mark_node;
  92     }
  93
  94   if (type == TREE_TYPE (expr))
  95     return expr;
  96   ret = targetm.convert_to_type (type, expr);
  97   if (ret)
  98       return ret;
  99
 100   STRIP_TYPE_NOPS (e);
 101
 102   if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr))
 103       && (TREE_CODE (TREE_TYPE (expr)) != COMPLEX_TYPE
 104           || TREE_CODE (e) == COMPLEX_EXPR))
 105     return fold_convert_loc (loc, type, expr);
 106   if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
 107     return error_mark_node;
 108   if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
 109     {
 110       error ("void value not ignored as it ought to be");
 111       return error_mark_node;
 112     }
 113
 114   switch (code)
 115     {
 116     case VOID_TYPE:
 117       return fold_convert_loc (loc, type, e);
 118
 119     case INTEGER_TYPE:
 120     case ENUMERAL_TYPE:
 121       if (flag_sanitize & SANITIZE_FLOAT_CAST
 122           && TREE_CODE (TREE_TYPE (expr)) == REAL_TYPE
 123           && COMPLETE_TYPE_P (type)
 124           && current_function_decl != NULL_TREE
 125           && !lookup_attribute ("no_sanitize_undefined",
 126                                 DECL_ATTRIBUTES (current_function_decl)))
 127         {
 128           tree arg;
 129           if (in_late_binary_op)
 130             {
 131               expr = save_expr (expr);
 132               arg = expr;
 133             }
 134           else
 135             {
 136               expr = c_save_expr (expr);
 137               arg = c_fully_fold (expr, false, NULL);
 138             }
 139           tree check = ubsan_instrument_float_cast (loc, type, expr, arg);
 140           expr = fold_build1 (FIX_TRUNC_EXPR, type, expr);
 141           if (check == NULL)
 142             return expr;
 143           return fold_build2 (COMPOUND_EXPR, TREE_TYPE (expr), check, expr);
 144         }
 145       ret = convert_to_integer (type, e);
 146       goto maybe_fold;
 147
 148     case BOOLEAN_TYPE:
 149       return fold_convert_loc
 150         (loc, type, c_objc_common_truthvalue_conversion (input_location, expr));
 151
 152     case POINTER_TYPE:
 153     case REFERENCE_TYPE:
 154       ret = convert_to_pointer (type, e);
 155       goto maybe_fold;
 156
 157     case REAL_TYPE:
 158       ret = convert_to_real (type, e);
 159       goto maybe_fold;
 160
 161     case FIXED_POINT_TYPE:
 162       ret = convert_to_fixed (type, e);
 163       goto maybe_fold;
 164
 165     case COMPLEX_TYPE:
 166       /* If converting from COMPLEX_TYPE to a different COMPLEX_TYPE
 167          and e is not COMPLEX_EXPR, convert_to_complex uses save_expr,
 168          but for the C FE c_save_expr needs to be called instead.  */
 169       if (TREE_CODE (TREE_TYPE (e)) == COMPLEX_TYPE)
 170         {
 171           if (TREE_CODE (e) != COMPLEX_EXPR)
 172             {
 173               tree subtype = TREE_TYPE (type);
 174               tree elt_type = TREE_TYPE (TREE_TYPE (e));
 175
 176               if (in_late_binary_op)
 177                 e = save_expr (e);
 178               else
 179                 e = c_save_expr (e);
 180               ret
 181                 = fold_build2_loc (loc, COMPLEX_EXPR, type,
 182                                    convert (subtype,
 183                                             fold_build1 (REALPART_EXPR,
 184                                                          elt_type, e)),
 185                                    convert (subtype,
 186                                             fold_build1 (IMAGPART_EXPR,
 187                                                          elt_type, e)));
 188               goto maybe_fold;
 189             }
 190         }
 191       ret = convert_to_complex (type, e);
 192       goto maybe_fold;
 193
 194     case VECTOR_TYPE:
 195       ret = convert_to_vector (type, e);
 196       goto maybe_fold;
 197
 198     case RECORD_TYPE:
 199     case UNION_TYPE:
 200       if (lang_hooks.types_compatible_p (type, TREE_TYPE (expr)))
 201         return e;
 202       break;
 203
 204     default:
 205       break;
 206
 207     maybe_fold:
 208       if (TREE_CODE (ret) != C_MAYBE_CONST_EXPR)
 209         ret = fold (ret);
 210       return ret;
 211     }
 212
 213   error ("conversion to non-scalar type requested");
 214   return error_mark_node;
 215 }