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 "tree-upc.h"
  40 #include "flags.h"
  41 #include "convert.h"
  42 #include "c-family/c-common.h"
  43 #include "c-family/c-upc.h"
  44 #include "c-tree.h"
  45 #include "langhooks.h"
  46 #include "target.h"
  47 #include "ubsan.h"
  48
  49 /* Change of width--truncation and extension of integers or reals--
  50    is represented with NOP_EXPR.  Proper functioning of many things
  51    assumes that no other conversions can be NOP_EXPRs.
  52
  53    Conversion between integer and pointer is represented with CONVERT_EXPR.
  54    Converting integer to real uses FLOAT_EXPR
  55    and real to integer uses FIX_TRUNC_EXPR.
  56
  57    Here is a list of all the functions that assume that widening and
  58    narrowing is always done with a NOP_EXPR:
  59      In convert.c, convert_to_integer.
  60      In c-typeck.c, build_binary_op (boolean ops), and
  61         c_common_truthvalue_conversion.
  62      In expr.c: expand_expr, for operands of a MULT_EXPR.
  63      In fold-const.c: fold.
  64      In tree.c: get_narrower and get_unwidened.  */
  65 \f
  66 /* Subroutines of `convert'.  */
  67
  68
  69 \f
  70 /* Create an expression whose value is that of EXPR,
  71    converted to type TYPE.  The TREE_TYPE of the value
  72    is always TYPE.  This function implements all reasonable
  73    conversions; callers should filter out those that are
  74    not permitted by the language being compiled.  */
  75
  76 tree
  77 convert (tree type, tree expr)
  78 {
  79   tree e = expr;
  80   enum tree_code code = TREE_CODE (type);
  81   const char *invalid_conv_diag;
  82   tree ret;
  83   location_t loc = EXPR_LOCATION (expr);
  84
  85   if (type == error_mark_node
  86       || error_operand_p (expr))
  87     return error_mark_node;
  88
  89   if ((invalid_conv_diag
  90        = targetm.invalid_conversion (TREE_TYPE (expr), type)))
  91     {
  92       error (invalid_conv_diag);
  93       return error_mark_node;
  94     }
  95
  96   if (type == TREE_TYPE (expr))
  97     return expr;
  98   ret = targetm.convert_to_type (type, expr);
  99   if (ret)
 100       return ret;
 101
 102   STRIP_TYPE_NOPS (e);
 103
 104   /* Drop 'shared' qualifier when considering conversions
 105      of expression values.  */
 106   if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr))
 107       && upc_shared_type_p (type))
 108     return fold_convert_loc (loc, build_upc_unshared_type(type), expr);
 109
 110   if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr))
 111       && (TREE_CODE (TREE_TYPE (expr)) != COMPLEX_TYPE
 112           || TREE_CODE (e) == COMPLEX_EXPR))
 113     return fold_convert_loc (loc, type, expr);
 114   if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
 115     return error_mark_node;
 116   if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
 117     {
 118       error ("void value not ignored as it ought to be");
 119       return error_mark_node;
 120     }
 121
 122   switch (code)
 123     {
 124     case VOID_TYPE:
 125       return fold_convert_loc (loc, type, e);
 126
 127     case INTEGER_TYPE:
 128     case ENUMERAL_TYPE:
 129       if (flag_sanitize & SANITIZE_FLOAT_CAST
 130           && TREE_CODE (TREE_TYPE (expr)) == REAL_TYPE
 131           && COMPLETE_TYPE_P (type)
 132           && current_function_decl != NULL_TREE
 133           && !lookup_attribute ("no_sanitize_undefined",
 134                                 DECL_ATTRIBUTES (current_function_decl)))
 135         {
 136           tree arg;
 137           if (in_late_binary_op)
 138             {
 139               expr = save_expr (expr);
 140               arg = expr;
 141             }
 142           else
 143             {
 144               expr = c_save_expr (expr);
 145               arg = c_fully_fold (expr, false, NULL);
 146             }
 147           tree check = ubsan_instrument_float_cast (loc, type, expr, arg);
 148           expr = fold_build1 (FIX_TRUNC_EXPR, type, expr);
 149           if (check == NULL)
 150             return expr;
 151           return fold_build2 (COMPOUND_EXPR, TREE_TYPE (expr), check, expr);
 152         }
 153       ret = convert_to_integer (type, e);
 154       goto maybe_fold;
 155
 156     case BOOLEAN_TYPE:
 157       return fold_convert_loc
 158         (loc, type, c_objc_common_truthvalue_conversion (input_location, expr));
 159
 160     case POINTER_TYPE:
 161     case REFERENCE_TYPE:
 162       ret = convert_to_pointer (type, e);
 163       goto maybe_fold;
 164
 165     case REAL_TYPE:
 166       ret = convert_to_real (type, e);
 167       goto maybe_fold;
 168
 169     case FIXED_POINT_TYPE:
 170       ret = convert_to_fixed (type, e);
 171       goto maybe_fold;
 172
 173     case COMPLEX_TYPE:
 174       /* If converting from COMPLEX_TYPE to a different COMPLEX_TYPE
 175          and e is not COMPLEX_EXPR, convert_to_complex uses save_expr,
 176          but for the C FE c_save_expr needs to be called instead.  */
 177       if (TREE_CODE (TREE_TYPE (e)) == COMPLEX_TYPE)
 178         {
 179           if (TREE_CODE (e) != COMPLEX_EXPR)
 180             {
 181               tree subtype = TREE_TYPE (type);
 182               tree elt_type = TREE_TYPE (TREE_TYPE (e));
 183
 184               if (in_late_binary_op)
 185                 e = save_expr (e);
 186               else
 187                 e = c_save_expr (e);
 188               ret
 189                 = fold_build2_loc (loc, COMPLEX_EXPR, type,
 190                                    convert (subtype,
 191                                             fold_build1 (REALPART_EXPR,
 192                                                          elt_type, e)),
 193                                    convert (subtype,
 194                                             fold_build1 (IMAGPART_EXPR,
 195                                                          elt_type, e)));
 196               goto maybe_fold;
 197             }
 198         }
 199       ret = convert_to_complex (type, e);
 200       goto maybe_fold;
 201
 202     case VECTOR_TYPE:
 203       ret = convert_to_vector (type, e);
 204       goto maybe_fold;
 205
 206     case RECORD_TYPE:
 207     case UNION_TYPE:
 208       if (lang_hooks.types_compatible_p (type, TREE_TYPE (expr)))
 209         return e;
 210       break;
 211
 212     default:
 213       break;
 214
 215     maybe_fold:
 216       if (TREE_CODE (ret) != C_MAYBE_CONST_EXPR)
 217         ret = fold (ret);
 218       return ret;
 219     }
 220
 221   error ("conversion to non-scalar type requested");
 222   return error_mark_node;
 223 }