1/* Language-level data type conversion for GNU C.
2   Copyright (C) 1987-2020 Free Software Foundation, Inc.
3
4This file is part of GCC.
5
6GCC is free software; you can redistribute it and/or modify it under
7the terms of the GNU General Public License as published by the Free
8Software Foundation; either version 3, or (at your option) any later
9version.
10
11GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12WARRANTY; without even the implied warranty of MERCHANTABILITY or
13FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14for more details.
15
16You should have received a copy of the GNU General Public License
17along 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
55/* Subroutines of `convert'.  */
56
57
58
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
65tree
66convert (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}
183