gcc/c/c-convert.c

   1 /* Language-level data type conversion for GNU C.
   2    Copyright (C) 1987-2020 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 "stringpool.h"
  35 #include "attribs.h"
  36 #include "asan.h"
  37
  38 /* Change of width--truncation and extension of integers or reals--
  39    is represented with NOP_EXPR.  Proper functioning of many things
  40    assumes that no other conversions can be NOP_EXPRs.
  41
  42    Conversion between integer and pointer is represented with CONVERT_EXPR.
  43    Converting integer to real uses FLOAT_EXPR
  44    and real to integer uses FIX_TRUNC_EXPR.
  45
  46    Here is a list of all the functions that assume that widening and
  47    narrowing is always done with a NOP_EXPR:
  48      In convert.c, convert_to_integer.
  49      In c-typeck.c, build_binary_op (boolean ops), and
  50         c_common_truthvalue_conversion.
  51      In expr.c: expand_expr, for operands of a MULT_EXPR.
  52      In fold-const.c: fold.
  53      In tree.c: get_narrower and get_unwidened.  */
  54 \f
  55 /* Subroutines of `convert'.  */
  56
  57
  58 \f
  59 /* Create an expression whose value is that of EXPR,
  60    converted to type TYPE.  The TREE_TYPE of the value
  61    is always TYPE.  This function implements all reasonable
  62    conversions; callers should filter out those that are
  63    not permitted by the language being compiled.  */
  64
  65 tree
  66 convert (tree type, tree expr)
  67 {
  68   tree e = expr;
  69   enum tree_code code = TREE_CODE (type);
  70   const char *invalid_conv_diag;
  71   tree ret;
  72   location_t loc = EXPR_LOCATION (expr);
  73
  74   if (type == error_mark_node
  75       || error_operand_p (expr))
  76     return error_mark_node;
  77
  78   if ((invalid_conv_diag
  79        = targetm.invalid_conversion (TREE_TYPE (expr), type)))
  80     {
  81       error (invalid_conv_diag);
  82       return error_mark_node;
  83     }
  84
  85   if (type == TREE_TYPE (expr))
  86     return expr;
  87   ret = targetm.convert_to_type (type, expr);
  88   if (ret)
  89       return ret;
  90
  91   STRIP_TYPE_NOPS (e);
  92
  93   if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr))
  94       && (TREE_CODE (TREE_TYPE (expr)) != COMPLEX_TYPE
  95           || TREE_CODE (e) == COMPLEX_EXPR))
  96     return fold_convert_loc (loc, type, expr);
  97   if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
  98     return error_mark_node;
  99   if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
 100     {
 101       error ("void value not ignored as it ought to be");
 102       return error_mark_node;
 103     }
 104
 105   switch (code)
 106     {
 107     case VOID_TYPE:
 108       return fold_convert_loc (loc, type, e);
 109
 110     case INTEGER_TYPE:
 111     case ENUMERAL_TYPE:
 112       if (sanitize_flags_p (SANITIZE_FLOAT_CAST)
 113           && current_function_decl != NULL_TREE
 114           && TREE_CODE (TREE_TYPE (expr)) == REAL_TYPE
 115           && COMPLETE_TYPE_P (type))
 116         {
 117           expr = save_expr (expr);
 118           expr = c_fully_fold (expr, false, NULL);
 119           tree check = ubsan_instrument_float_cast (loc, type, expr);
 120           expr = fold_build1 (FIX_TRUNC_EXPR, type, expr);
 121           if (check == NULL_TREE)
 122             return expr;
 123           return fold_build2 (COMPOUND_EXPR, TREE_TYPE (expr), check, expr);
 124         }
 125       ret = convert_to_integer (type, e);
 126       goto maybe_fold;
 127
 128     case BOOLEAN_TYPE:
 129       return fold_convert_loc
 130         (loc, type, c_objc_common_truthvalue_conversion (input_location, expr));
 131
 132     case POINTER_TYPE:
 133     case REFERENCE_TYPE:
 134       ret = convert_to_pointer (type, e);
 135       goto maybe_fold;
 136
 137     case REAL_TYPE:
 138       ret = convert_to_real (type, e);
 139       goto maybe_fold;
 140
 141     case FIXED_POINT_TYPE:
 142       ret = convert_to_fixed (type, e);
 143       goto maybe_fold;
 144
 145     case COMPLEX_TYPE:
 146       ret = convert_to_complex (type, e);
 147       goto maybe_fold;
 148
 149     case VECTOR_TYPE:
 150       if (gnu_vector_type_p (type)
 151           || gnu_vector_type_p (TREE_TYPE (e))
 152           /* Allow conversions between compatible non-GNU vector types
 153              when -flax-vector-conversions is passed.  The whole purpose
 154              of the option is to bend the normal type rules and accept
 155              nonconforming code.  */
 156           || (flag_lax_vector_conversions
 157               && VECTOR_TYPE_P (TREE_TYPE (e))
 158               && vector_types_convertible_p (type, TREE_TYPE (e), false)))
 159         {
 160           ret = convert_to_vector (type, e);
 161           goto maybe_fold;
 162         }
 163       break;
 164
 165     case RECORD_TYPE:
 166     case UNION_TYPE:
 167       if (lang_hooks.types_compatible_p (type, TREE_TYPE (expr)))
 168         return e;
 169       break;
 170
 171     default:
 172       break;
 173
 174     maybe_fold:
 175       if (TREE_CODE (ret) != C_MAYBE_CONST_EXPR)
 176         ret = fold (ret);
 177       return ret;
 178     }
 179
 180   error ("conversion to non-scalar type requested");
 181   return error_mark_node;
 182 }