/* Language-level data type conversion for GNU C.
Copyright (C) 1987-2022 Free Software Foundation, Inc.
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.
GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.
You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3. If not see
<http://www.gnu.org/licenses/>. */
/* This file contains the functions for converting C expressions
to different data types. The only entry point is `convert'.
Every language front end must have a `convert' function
but what kind of conversions it does will depend on the language. */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "target.h"
#include "c-tree.h"
#include "convert.h"
#include "langhooks.h"
#include "ubsan.h"
#include "stringpool.h"
#include "attribs.h"
#include "asan.h"
/* Change of width--truncation and extension of integers or reals--
is represented with NOP_EXPR. Proper functioning of many things
assumes that no other conversions can be NOP_EXPRs.
Conversion between integer and pointer is represented with CONVERT_EXPR.
Converting integer to real uses FLOAT_EXPR
and real to integer uses FIX_TRUNC_EXPR.
Here is a list of all the functions that assume that widening and
narrowing is always done with a NOP_EXPR:
In convert.cc, convert_to_integer.
In c-typeck.cc, build_binary_op (boolean ops), and
c_common_truthvalue_conversion.
In expr.cc: expand_expr, for operands of a MULT_EXPR.
In fold-const.cc: fold.
In tree.cc: get_narrower and get_unwidened. */
/* Subroutines of `convert'. */
/* Create an expression whose value is that of EXPR,
converted to type TYPE. The TREE_TYPE of the value
is always TYPE. This function implements all reasonable
conversions; callers should filter out those that are
not permitted by the language being compiled.
INIT_CONST is true if the conversion is for arithmetic types for a static
initializer and folding must apply accordingly (discarding floating-point
exceptions and assuming the default rounding mode is in effect). */
static tree
c_convert (tree type, tree expr, bool init_const)
{
tree e = expr;
enum tree_code code = TREE_CODE (type);
const char *invalid_conv_diag;
tree ret;
location_t loc = EXPR_LOCATION (expr);
if (type == error_mark_node
|| error_operand_p (expr))
return error_mark_node;
if ((invalid_conv_diag
= targetm.invalid_conversion (TREE_TYPE (expr), type)))
{
error (invalid_conv_diag);
return error_mark_node;
}
if (type == TREE_TYPE (expr))
return expr;
ret = targetm.convert_to_type (type, expr);
if (ret)
return ret;
STRIP_TYPE_NOPS (e);
if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr))
&& (TREE_CODE (TREE_TYPE (expr)) != COMPLEX_TYPE
|| TREE_CODE (e) == COMPLEX_EXPR))
return fold_convert_loc (loc, type, expr);
if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
return error_mark_node;
if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
{
error ("void value not ignored as it ought to be");
return error_mark_node;
}
switch (code)
{
case VOID_TYPE:
return fold_convert_loc (loc, type, e);
case INTEGER_TYPE:
case ENUMERAL_TYPE:
if (sanitize_flags_p (SANITIZE_FLOAT_CAST)
&& current_function_decl != NULL_TREE
&& TREE_CODE (TREE_TYPE (expr)) == REAL_TYPE
&& COMPLETE_TYPE_P (type))
{
expr = save_expr (expr);
expr = c_fully_fold (expr, init_const, NULL);
tree check = ubsan_instrument_float_cast (loc, type, expr);
expr = fold_build1 (FIX_TRUNC_EXPR, type, expr);
if (check == NULL_TREE)
return expr;
return fold_build2 (COMPOUND_EXPR, TREE_TYPE (expr), check, expr);
}
ret = convert_to_integer (type, e);
goto maybe_fold;
case BOOLEAN_TYPE:
return fold_convert_loc
(loc, type, c_objc_common_truthvalue_conversion (input_location, expr));
case POINTER_TYPE:
/* The type nullptr_t may be converted to a pointer type. The result is
a null pointer value. */
if (NULLPTR_TYPE_P (TREE_TYPE (e)))
{
/* To make sure that (void *)nullptr is not a null pointer constant,
build_c_cast will create an additional NOP_EXPR around the result
of this conversion. */
if (TREE_SIDE_EFFECTS (e))
ret = build2 (COMPOUND_EXPR, type, e, build_int_cst (type, 0));
else
ret = build_int_cst (type, 0);
goto maybe_fold;
}
gcc_fallthrough ();
case REFERENCE_TYPE:
ret = convert_to_pointer (type, e);
goto maybe_fold;
case REAL_TYPE:
ret = convert_to_real (type, e);
goto maybe_fold;
case FIXED_POINT_TYPE:
ret = convert_to_fixed (type, e);
goto maybe_fold;
case COMPLEX_TYPE:
ret = convert_to_complex (type, e);
goto maybe_fold;
case VECTOR_TYPE:
if (gnu_vector_type_p (type)
|| gnu_vector_type_p (TREE_TYPE (e))
/* Allow conversions between compatible non-GNU vector types
when -flax-vector-conversions is passed. The whole purpose
of the option is to bend the normal type rules and accept
nonconforming code. */
|| (flag_lax_vector_conversions
&& VECTOR_TYPE_P (TREE_TYPE (e))
&& vector_types_convertible_p (type, TREE_TYPE (e), false)))
{
ret = convert_to_vector (type, e);
goto maybe_fold;
}
break;
case RECORD_TYPE:
case UNION_TYPE:
if (lang_hooks.types_compatible_p (type, TREE_TYPE (expr)))
return e;
break;
default:
break;
maybe_fold:
if (TREE_CODE (ret) != C_MAYBE_CONST_EXPR)
ret = init_const ? fold_init (ret) : fold (ret);
return ret;
}
/* If we are converting to nullptr_t, don't say "non-scalar type" because
the nullptr_t type is a scalar type. Only nullptr_t shall be converted
to nullptr_t. */
if (code == NULLPTR_TYPE)
{
error ("conversion from %qT to %qT", TREE_TYPE (e), type);
inform (input_location, "only %qT can be converted to %qT", type, type);
}
else
error ("conversion to non-scalar type requested");
return error_mark_node;
}
/* Create an expression whose value is that of EXPR, converted to type TYPE.
The TREE_TYPE of the value is always TYPE. This function implements all
reasonable conversions; callers should filter out those that are not
permitted by the language being compiled. */
tree
convert (tree type, tree expr)
{
return c_convert (type, expr, false);
}
/* Create an expression whose value is that of EXPR, converted to type TYPE, in
a static initializer. The TREE_TYPE of the value is always TYPE. This
function implements all reasonable conversions; callers should filter out
those that are not permitted by the language being compiled. */
tree
convert_init (tree type, tree expr)
{
return c_convert (type, expr, true);
}