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