gcc/c/c-convert.c

   1 /* Language-level data type conversion for GNU C.
   2    Copyright (C) 1987-2016 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
  35 /* Change of width--truncation and extension of integers or reals--
  36    is represented with NOP_EXPR.  Proper functioning of many things
  37    assumes that no other conversions can be NOP_EXPRs.
  38
  39    Conversion between integer and pointer is represented with CONVERT_EXPR.
  40    Converting integer to real uses FLOAT_EXPR
  41    and real to integer uses FIX_TRUNC_EXPR.
  42
  43    Here is a list of all the functions that assume that widening and
  44    narrowing is always done with a NOP_EXPR:
  45      In convert.c, convert_to_integer.
  46      In c-typeck.c, build_binary_op (boolean ops), and
  47         c_common_truthvalue_conversion.
  48      In expr.c: expand_expr, for operands of a MULT_EXPR.
  49      In fold-const.c: fold.
  50      In tree.c: get_narrower and get_unwidened.  */
  51 \f
  52 /* Subroutines of `convert'.  */
  53
  54
  55 \f
  56 /* Create an expression whose value is that of EXPR,
  57    converted to type TYPE.  The TREE_TYPE of the value
  58    is always TYPE.  This function implements all reasonable
  59    conversions; callers should filter out those that are
  60    not permitted by the language being compiled.  */
  61
  62 tree
  63 convert (tree type, tree expr)
  64 {
  65   tree e = expr;
  66   enum tree_code code = TREE_CODE (type);
  67   const char *invalid_conv_diag;
  68   tree ret;
  69   location_t loc = EXPR_LOCATION (expr);
  70
  71   if (type == error_mark_node
  72       || error_operand_p (expr))
  73     return error_mark_node;
  74
  75   if ((invalid_conv_diag
  76        = targetm.invalid_conversion (TREE_TYPE (expr), type)))
  77     {
  78       error (invalid_conv_diag);
  79       return error_mark_node;
  80     }
  81
  82   if (type == TREE_TYPE (expr))
  83     return expr;
  84   ret = targetm.convert_to_type (type, expr);
  85   if (ret)
  86       return ret;
  87
  88   STRIP_TYPE_NOPS (e);
  89
  90   if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr))
  91       && (TREE_CODE (TREE_TYPE (expr)) != COMPLEX_TYPE
  92           || TREE_CODE (e) == COMPLEX_EXPR))
  93     return fold_convert_loc (loc, type, expr);
  94   if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
  95     return error_mark_node;
  96   if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
  97     {
  98       error ("void value not ignored as it ought to be");
  99       return error_mark_node;
 100     }
 101
 102   switch (code)
 103     {
 104     case VOID_TYPE:
 105       return fold_convert_loc (loc, type, e);
 106
 107     case INTEGER_TYPE:
 108     case ENUMERAL_TYPE:
 109       if (flag_sanitize & SANITIZE_FLOAT_CAST
 110           && TREE_CODE (TREE_TYPE (expr)) == REAL_TYPE
 111           && COMPLETE_TYPE_P (type)
 112           && do_ubsan_in_current_function ())
 113         {
 114           tree arg;
 115           if (in_late_binary_op)
 116             {
 117               expr = save_expr (expr);
 118               arg = expr;
 119             }
 120           else
 121             {
 122               expr = c_save_expr (expr);
 123               arg = c_fully_fold (expr, false, NULL);
 124             }
 125           tree check = ubsan_instrument_float_cast (loc, type, expr, arg);
 126           expr = fold_build1 (FIX_TRUNC_EXPR, type, expr);
 127           if (check == NULL)
 128             return expr;
 129           return fold_build2 (COMPOUND_EXPR, TREE_TYPE (expr), check, expr);
 130         }
 131       ret = convert_to_integer (type, e);
 132       goto maybe_fold;
 133
 134     case BOOLEAN_TYPE:
 135       return fold_convert_loc
 136         (loc, type, c_objc_common_truthvalue_conversion (input_location, expr));
 137
 138     case POINTER_TYPE:
 139     case REFERENCE_TYPE:
 140       ret = convert_to_pointer (type, e);
 141       goto maybe_fold;
 142
 143     case REAL_TYPE:
 144       ret = convert_to_real (type, e);
 145       goto maybe_fold;
 146
 147     case FIXED_POINT_TYPE:
 148       ret = convert_to_fixed (type, e);
 149       goto maybe_fold;
 150
 151     case COMPLEX_TYPE:
 152       /* If converting from COMPLEX_TYPE to a different COMPLEX_TYPE
 153          and e is not COMPLEX_EXPR, convert_to_complex uses save_expr,
 154          but for the C FE c_save_expr needs to be called instead.  */
 155       if (TREE_CODE (TREE_TYPE (e)) == COMPLEX_TYPE)
 156         {
 157           if (TREE_CODE (e) != COMPLEX_EXPR)
 158             {
 159               tree subtype = TREE_TYPE (type);
 160               tree elt_type = TREE_TYPE (TREE_TYPE (e));
 161
 162               if (in_late_binary_op)
 163                 e = save_expr (e);
 164               else
 165                 e = c_save_expr (e);
 166               ret
 167                 = fold_build2_loc (loc, COMPLEX_EXPR, type,
 168                                    convert (subtype,
 169                                             fold_build1 (REALPART_EXPR,
 170                                                          elt_type, e)),
 171                                    convert (subtype,
 172                                             fold_build1 (IMAGPART_EXPR,
 173                                                          elt_type, e)));
 174               goto maybe_fold;
 175             }
 176         }
 177       ret = convert_to_complex (type, e);
 178       goto maybe_fold;
 179
 180     case VECTOR_TYPE:
 181       ret = convert_to_vector (type, e);
 182       goto maybe_fold;
 183
 184     case RECORD_TYPE:
 185     case UNION_TYPE:
 186       if (lang_hooks.types_compatible_p (type, TREE_TYPE (expr)))
 187         return e;
 188       break;
 189
 190     default:
 191       break;
 192
 193     maybe_fold:
 194       if (TREE_CODE (ret) != C_MAYBE_CONST_EXPR)
 195         ret = fold (ret);
 196       return ret;
 197     }
 198
 199   error ("conversion to non-scalar type requested");
 200   return error_mark_node;
 201 }