1 /* Language-level data type conversion for GNU C++.
2 Copyright (C) 1987-2016 Free Software Foundation, Inc.
3 Hacked by Michael Tiemann (tiemann@cygnus.com)
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3, or (at your option)
12 GCC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
22 /* This file contains the functions for converting C++ expressions
23 to different data types. The only entry point is `convert'.
24 Every language front end must have a `convert' function
25 but what kind of conversions it does will depend on the language. */
29 #include "coretypes.h"
32 #include "stor-layout.h"
37 static tree convert_to_pointer_force (tree, tree, tsubst_flags_t);
38 static tree build_type_conversion (tree, tree);
39 static tree build_up_reference (tree, tree, int, tree, tsubst_flags_t);
40 static void diagnose_ref_binding (location_t, tree, tree, tree);
42 /* Change of width--truncation and extension of integers or reals--
43 is represented with NOP_EXPR. Proper functioning of many things
44 assumes that no other conversions can be NOP_EXPRs.
46 Conversion between integer and pointer is represented with CONVERT_EXPR.
47 Converting integer to real uses FLOAT_EXPR
48 and real to integer uses FIX_TRUNC_EXPR.
50 Here is a list of all the functions that assume that widening and
51 narrowing is always done with a NOP_EXPR:
52 In convert.c, convert_to_integer[_maybe_fold].
53 In c-typeck.c, build_binary_op_nodefault (boolean ops),
54 and c_common_truthvalue_conversion.
55 In expr.c: expand_expr, for operands of a MULT_EXPR.
56 In fold-const.c: fold.
57 In tree.c: get_narrower and get_unwidened.
59 C++: in multiple-inheritance, converting between pointers may involve
60 adjusting them by a delta stored within the class definition. */
62 /* Subroutines of `convert'. */
64 /* if converting pointer to pointer
65 if dealing with classes, check for derived->base or vice versa
66 else if dealing with method pointers, delegate
68 else if converting class, pass off to build_type_conversion
69 else try C-style pointer conversion. */
72 cp_convert_to_pointer (tree type, tree expr, bool dofold,
73 tsubst_flags_t complain)
75 tree intype = TREE_TYPE (expr);
78 location_t loc = EXPR_LOC_OR_LOC (expr, input_location);
80 if (intype == error_mark_node)
81 return error_mark_node;
83 if (MAYBE_CLASS_TYPE_P (intype))
85 intype = complete_type (intype);
86 if (!COMPLETE_TYPE_P (intype))
88 if (complain & tf_error)
89 error_at (loc, "can%'t convert from incomplete type %qT to %qT",
91 return error_mark_node;
94 rval = build_type_conversion (type, expr);
97 if ((complain & tf_error)
98 && rval == error_mark_node)
99 error_at (loc, "conversion of %qE from %qT to %qT is ambiguous",
105 /* Handle anachronistic conversions from (::*)() to cv void* or (*)(). */
106 if (TYPE_PTR_P (type)
107 && (TREE_CODE (TREE_TYPE (type)) == FUNCTION_TYPE
108 || VOID_TYPE_P (TREE_TYPE (type))))
110 if (TYPE_PTRMEMFUNC_P (intype)
111 || TREE_CODE (intype) == METHOD_TYPE)
112 return convert_member_func_to_ptr (type, expr, complain);
113 if (TYPE_PTR_P (TREE_TYPE (expr)))
114 return build_nop (type, expr);
115 intype = TREE_TYPE (expr);
118 if (expr == error_mark_node)
119 return error_mark_node;
121 form = TREE_CODE (intype);
123 if (POINTER_TYPE_P (intype))
125 intype = TYPE_MAIN_VARIANT (intype);
127 if (TYPE_MAIN_VARIANT (type) != intype
129 && TREE_CODE (TREE_TYPE (type)) == RECORD_TYPE
130 && MAYBE_CLASS_TYPE_P (TREE_TYPE (type))
131 && MAYBE_CLASS_TYPE_P (TREE_TYPE (intype))
132 && TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE)
134 enum tree_code code = PLUS_EXPR;
140 intype_class = TREE_TYPE (intype);
141 type_class = TREE_TYPE (type);
143 same_p = same_type_p (TYPE_MAIN_VARIANT (intype_class),
144 TYPE_MAIN_VARIANT (type_class));
146 /* Try derived to base conversion. */
148 binfo = lookup_base (intype_class, type_class, ba_check,
150 if (!same_p && !binfo)
152 /* Try base to derived conversion. */
153 binfo = lookup_base (type_class, intype_class, ba_check,
157 if (binfo == error_mark_node)
158 return error_mark_node;
162 expr = build_base_path (code, expr, binfo, 0, complain);
163 /* Add any qualifier conversions. */
164 return build_nop (type, expr);
168 if (TYPE_PTRMEMFUNC_P (type))
170 if (complain & tf_error)
171 error_at (loc, "cannot convert %qE from type %qT to type %qT",
173 return error_mark_node;
176 return build_nop (type, expr);
178 else if ((TYPE_PTRDATAMEM_P (type) && TYPE_PTRDATAMEM_P (intype))
179 || (TYPE_PTRMEMFUNC_P (type) && TYPE_PTRMEMFUNC_P (intype)))
180 return convert_ptrmem (type, expr, /*allow_inverse_p=*/false,
181 /*c_cast_p=*/false, complain);
182 else if (TYPE_PTRMEMFUNC_P (intype))
186 if (TREE_CODE (expr) == PTRMEM_CST)
187 return cp_convert_to_pointer (type, PTRMEM_CST_MEMBER (expr),
189 else if (TREE_CODE (expr) == OFFSET_REF)
191 tree object = TREE_OPERAND (expr, 0);
192 return get_member_function_from_ptrfunc (&object,
193 TREE_OPERAND (expr, 1),
197 if (complain & tf_error)
198 error_at (loc, "cannot convert %qE from type %qT to type %qT",
200 return error_mark_node;
203 if (null_ptr_cst_p (expr))
205 if (TYPE_PTRMEMFUNC_P (type))
206 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), expr, 0,
207 /*c_cast_p=*/false, complain);
209 if (complain & tf_warning)
210 maybe_warn_zero_as_null_pointer_constant (expr, loc);
212 /* A NULL pointer-to-data-member is represented by -1, not by
214 tree val = (TYPE_PTRDATAMEM_P (type)
215 ? build_int_cst_type (type, -1)
216 : build_int_cst (type, 0));
218 return (TREE_SIDE_EFFECTS (expr)
219 ? build2 (COMPOUND_EXPR, type, expr, val) : val);
221 else if (TYPE_PTRMEM_P (type) && INTEGRAL_CODE_P (form))
223 if (complain & tf_error)
224 error_at (loc, "invalid conversion from %qT to %qT", intype, type);
225 return error_mark_node;
228 if (INTEGRAL_CODE_P (form))
230 if (TYPE_PRECISION (intype) == POINTER_SIZE)
231 return build1 (CONVERT_EXPR, type, expr);
232 expr = cp_convert (c_common_type_for_size (POINTER_SIZE, 0), expr,
234 /* Modes may be different but sizes should be the same. There
235 is supposed to be some integral type that is the same width
237 gcc_assert (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (expr)))
238 == GET_MODE_SIZE (TYPE_MODE (type)));
240 return convert_to_pointer_maybe_fold (type, expr, dofold);
243 if (type_unknown_p (expr))
244 return instantiate_type (type, expr, complain);
246 if (complain & tf_error)
247 error_at (loc, "cannot convert %qE from type %qT to type %qT",
249 return error_mark_node;
252 /* Like convert, except permit conversions to take place which
253 are not normally allowed due to access restrictions
254 (such as conversion from sub-type to private super-type). */
257 convert_to_pointer_force (tree type, tree expr, tsubst_flags_t complain)
259 tree intype = TREE_TYPE (expr);
260 enum tree_code form = TREE_CODE (intype);
262 if (form == POINTER_TYPE)
264 intype = TYPE_MAIN_VARIANT (intype);
266 if (TYPE_MAIN_VARIANT (type) != intype
267 && TREE_CODE (TREE_TYPE (type)) == RECORD_TYPE
268 && MAYBE_CLASS_TYPE_P (TREE_TYPE (type))
269 && MAYBE_CLASS_TYPE_P (TREE_TYPE (intype))
270 && TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE)
272 enum tree_code code = PLUS_EXPR;
275 binfo = lookup_base (TREE_TYPE (intype), TREE_TYPE (type),
276 ba_unique, NULL, complain);
279 binfo = lookup_base (TREE_TYPE (type), TREE_TYPE (intype),
280 ba_unique, NULL, complain);
283 if (binfo == error_mark_node)
284 return error_mark_node;
287 expr = build_base_path (code, expr, binfo, 0, complain);
288 if (expr == error_mark_node)
289 return error_mark_node;
290 /* Add any qualifier conversions. */
291 if (!same_type_p (TREE_TYPE (TREE_TYPE (expr)),
293 expr = build_nop (type, expr);
299 return cp_convert_to_pointer (type, expr, /*fold*/false, complain);
302 /* We are passing something to a function which requires a reference.
303 The type we are interested in is in TYPE. The initial
304 value we have to begin with is in ARG.
306 FLAGS controls how we manage access checking.
307 DIRECT_BIND in FLAGS controls how any temporaries are generated.
308 If DIRECT_BIND is set, DECL is the reference we're binding to. */
311 build_up_reference (tree type, tree arg, int flags, tree decl,
312 tsubst_flags_t complain)
315 tree argtype = TREE_TYPE (arg);
316 tree target_type = TREE_TYPE (type);
318 gcc_assert (TREE_CODE (type) == REFERENCE_TYPE);
320 if ((flags & DIRECT_BIND) && ! lvalue_p (arg))
322 /* Create a new temporary variable. We can't just use a TARGET_EXPR
323 here because it needs to live as long as DECL. */
326 arg = make_temporary_var_for_ref_to_temp (decl, target_type);
328 /* Process the initializer for the declaration. */
329 DECL_INITIAL (arg) = targ;
330 cp_finish_decl (arg, targ, /*init_const_expr_p=*/false, NULL_TREE,
331 LOOKUP_ONLYCONVERTING|DIRECT_BIND);
333 else if (!(flags & DIRECT_BIND) && ! obvalue_p (arg))
334 return get_target_expr_sfinae (arg, complain);
336 /* If we had a way to wrap this up, and say, if we ever needed its
337 address, transform all occurrences of the register, into a memory
338 reference we could win better. */
339 rval = cp_build_addr_expr (arg, complain);
340 if (rval == error_mark_node)
341 return error_mark_node;
343 if ((flags & LOOKUP_PROTECT)
344 && TYPE_MAIN_VARIANT (argtype) != TYPE_MAIN_VARIANT (target_type)
345 && MAYBE_CLASS_TYPE_P (argtype)
346 && MAYBE_CLASS_TYPE_P (target_type))
348 /* We go through lookup_base for the access control. */
349 tree binfo = lookup_base (argtype, target_type, ba_check,
351 if (binfo == error_mark_node)
352 return error_mark_node;
353 if (binfo == NULL_TREE)
354 return error_not_base_type (target_type, argtype);
355 rval = build_base_path (PLUS_EXPR, rval, binfo, 1, complain);
359 = convert_to_pointer_force (build_pointer_type (target_type),
361 return build_nop (type, rval);
364 /* Subroutine of convert_to_reference. REFTYPE is the target reference type.
365 INTYPE is the original rvalue type and DECL is an optional _DECL node
368 [dcl.init.ref] says that if an rvalue is used to
369 initialize a reference, then the reference must be to a
370 non-volatile const type. */
373 diagnose_ref_binding (location_t loc, tree reftype, tree intype, tree decl)
375 tree ttl = TREE_TYPE (reftype);
377 if (!CP_TYPE_CONST_NON_VOLATILE_P (ttl))
381 if (CP_TYPE_VOLATILE_P (ttl) && decl)
382 msg = G_("initialization of volatile reference type %q#T from "
383 "rvalue of type %qT");
384 else if (CP_TYPE_VOLATILE_P (ttl))
385 msg = G_("conversion to volatile reference type %q#T "
386 "from rvalue of type %qT");
388 msg = G_("initialization of non-const reference type %q#T from "
389 "rvalue of type %qT");
391 msg = G_("conversion to non-const reference type %q#T from "
392 "rvalue of type %qT");
394 permerror (loc, msg, reftype, intype);
398 /* For C++: Only need to do one-level references, but cannot
399 get tripped up on signed/unsigned differences.
401 DECL is either NULL_TREE or the _DECL node for a reference that is being
402 initialized. It can be error_mark_node if we don't know the _DECL but
403 we know it's an initialization. */
406 convert_to_reference (tree reftype, tree expr, int convtype,
407 int flags, tree decl, tsubst_flags_t complain)
409 tree type = TYPE_MAIN_VARIANT (TREE_TYPE (reftype));
411 tree rval = NULL_TREE;
412 tree rval_as_conversion = NULL_TREE;
413 bool can_convert_intype_to_type;
414 location_t loc = EXPR_LOC_OR_LOC (expr, input_location);
416 if (TREE_CODE (type) == FUNCTION_TYPE
417 && TREE_TYPE (expr) == unknown_type_node)
418 expr = instantiate_type (type, expr, complain);
420 if (expr == error_mark_node)
421 return error_mark_node;
423 intype = TREE_TYPE (expr);
425 gcc_assert (TREE_CODE (intype) != REFERENCE_TYPE);
426 gcc_assert (TREE_CODE (reftype) == REFERENCE_TYPE);
428 intype = TYPE_MAIN_VARIANT (intype);
430 can_convert_intype_to_type = can_convert_standard (type, intype, complain);
432 if (!can_convert_intype_to_type
433 && (convtype & CONV_IMPLICIT) && MAYBE_CLASS_TYPE_P (intype)
434 && ! (flags & LOOKUP_NO_CONVERSION))
436 /* Look for a user-defined conversion to lvalue that we can use. */
439 = build_type_conversion (reftype, expr);
441 if (rval_as_conversion && rval_as_conversion != error_mark_node
442 && lvalue_p (rval_as_conversion))
444 expr = rval_as_conversion;
445 rval_as_conversion = NULL_TREE;
447 can_convert_intype_to_type = 1;
451 if (((convtype & CONV_STATIC)
452 && can_convert_standard (intype, type, complain))
453 || ((convtype & CONV_IMPLICIT) && can_convert_intype_to_type))
456 tree ttl = TREE_TYPE (reftype);
457 tree ttr = lvalue_type (expr);
459 if ((complain & tf_error)
460 && ! lvalue_p (expr))
461 diagnose_ref_binding (loc, reftype, intype, decl);
463 if (! (convtype & CONV_CONST)
464 && !at_least_as_qualified_p (ttl, ttr))
466 if (complain & tf_error)
467 permerror (loc, "conversion from %qT to %qT discards qualifiers",
470 return error_mark_node;
474 return build_up_reference (reftype, expr, flags, decl, complain);
476 else if ((convtype & CONV_REINTERPRET) && obvalue_p (expr))
478 /* When casting an lvalue to a reference type, just convert into
479 a pointer to the new type and deference it. This is allowed
480 by San Diego WP section 5.2.9 paragraph 12, though perhaps it
481 should be done directly (jason). (int &)ri ---> *(int*)&ri */
483 /* B* bp; A& ar = (A&)bp; is valid, but it's probably not what they
485 if ((complain & tf_warning)
486 && TYPE_PTR_P (intype)
487 && (comptypes (TREE_TYPE (intype), type,
488 COMPARE_BASE | COMPARE_DERIVED)))
489 warning_at (loc, 0, "casting %qT to %qT does not dereference pointer",
492 rval = cp_build_addr_expr (expr, complain);
493 if (rval != error_mark_node)
494 rval = convert_force (build_pointer_type (TREE_TYPE (reftype)),
496 if (rval != error_mark_node)
497 rval = build1 (NOP_EXPR, reftype, rval);
501 rval = convert_for_initialization (NULL_TREE, type, expr, flags,
502 ICR_CONVERTING, 0, 0, complain);
503 if (rval == NULL_TREE || rval == error_mark_node)
505 if (complain & tf_error)
506 diagnose_ref_binding (loc, reftype, intype, decl);
507 rval = build_up_reference (reftype, rval, flags, decl, complain);
512 /* If we found a way to convert earlier, then use it. */
516 if (complain & tf_error)
517 error_at (loc, "cannot convert type %qT to type %qT", intype, reftype);
519 return error_mark_node;
522 /* We are using a reference VAL for its value. Bash that reference all the
523 way down to its lowest form. */
526 convert_from_reference (tree val)
529 && TREE_CODE (TREE_TYPE (val)) == REFERENCE_TYPE)
531 tree t = TREE_TYPE (TREE_TYPE (val));
532 tree ref = build1 (INDIRECT_REF, t, val);
535 /* We *must* set TREE_READONLY when dereferencing a pointer to const,
536 so that we get the proper error message if the result is used
537 to assign to. Also, &* is supposed to be a no-op. */
538 TREE_READONLY (ref) = CP_TYPE_CONST_P (t);
539 TREE_THIS_VOLATILE (ref) = CP_TYPE_VOLATILE_P (t);
540 TREE_SIDE_EFFECTS (ref)
541 = (TREE_THIS_VOLATILE (ref) || TREE_SIDE_EFFECTS (val));
548 /* Really perform an lvalue-to-rvalue conversion, including copying an
549 argument of class type into a temporary. */
552 force_rvalue (tree expr, tsubst_flags_t complain)
554 tree type = TREE_TYPE (expr);
555 if (MAYBE_CLASS_TYPE_P (type) && TREE_CODE (expr) != TARGET_EXPR)
557 vec<tree, va_gc> *args = make_tree_vector_single (expr);
558 expr = build_special_member_call (NULL_TREE, complete_ctor_identifier,
559 &args, type, LOOKUP_NORMAL, complain);
560 release_tree_vector (args);
561 expr = build_cplus_new (type, expr, complain);
564 expr = decay_conversion (expr, complain);
570 /* If EXPR and ORIG are INTEGER_CSTs, return a version of EXPR that has
571 TREE_OVERFLOW set only if it is set in ORIG. Otherwise, return EXPR
575 ignore_overflows (tree expr, tree orig)
577 if (TREE_CODE (expr) == INTEGER_CST
578 && TREE_CODE (orig) == INTEGER_CST
579 && TREE_OVERFLOW (expr) != TREE_OVERFLOW (orig))
581 gcc_assert (!TREE_OVERFLOW (orig));
582 /* Ensure constant sharing. */
583 expr = wide_int_to_tree (TREE_TYPE (expr), expr);
588 /* Fold away simple conversions, but make sure TREE_OVERFLOW is set
592 cp_fold_convert (tree type, tree expr)
595 if (TREE_TYPE (expr) == type)
597 else if (TREE_CODE (expr) == PTRMEM_CST)
599 /* Avoid wrapping a PTRMEM_CST in NOP_EXPR. */
600 conv = copy_node (expr);
601 TREE_TYPE (conv) = type;
605 conv = fold_convert (type, expr);
606 conv = ignore_overflows (conv, expr);
611 /* C++ conversions, preference to static cast conversions. */
614 cp_convert (tree type, tree expr, tsubst_flags_t complain)
616 return ocp_convert (type, expr, CONV_OLD_CONVERT, LOOKUP_NORMAL, complain);
619 /* C++ equivalent of convert_and_check but using cp_convert as the
622 Convert EXPR to TYPE, warning about conversion problems with constants.
623 Invoke this function on every expression that is converted implicitly,
624 i.e. because of language rules and not because of an explicit cast. */
627 cp_convert_and_check (tree type, tree expr, tsubst_flags_t complain)
631 if (TREE_TYPE (expr) == type)
633 if (expr == error_mark_node)
635 result = cp_convert (type, expr, complain);
637 if ((complain & tf_warning)
638 && c_inhibit_evaluation_warnings == 0)
640 tree folded = cp_fully_fold (expr);
643 folded_result = result;
646 /* Avoid bogus -Wparentheses warnings. */
647 warning_sentinel w (warn_parentheses);
648 folded_result = cp_convert (type, folded, tf_none);
650 folded_result = fold_simple (folded_result);
651 if (!TREE_OVERFLOW_P (folded)
652 && folded_result != error_mark_node)
653 warnings_for_convert_and_check (EXPR_LOC_OR_LOC (expr, input_location),
654 type, folded, folded_result);
662 FLAGS indicates how we should behave. */
665 ocp_convert (tree type, tree expr, int convtype, int flags,
666 tsubst_flags_t complain)
669 enum tree_code code = TREE_CODE (type);
670 const char *invalid_conv_diag;
672 location_t loc = EXPR_LOC_OR_LOC (expr, input_location);
673 bool dofold = (convtype & CONV_FOLD);
675 if (error_operand_p (e) || type == error_mark_node)
676 return error_mark_node;
678 complete_type (type);
679 complete_type (TREE_TYPE (expr));
681 if ((invalid_conv_diag
682 = targetm.invalid_conversion (TREE_TYPE (expr), type)))
684 if (complain & tf_error)
685 error (invalid_conv_diag);
686 return error_mark_node;
689 /* FIXME remove when moving to c_fully_fold model. */
690 if (!CLASS_TYPE_P (type))
691 e = scalar_constant_value (e);
692 if (error_operand_p (e))
693 return error_mark_node;
695 if (MAYBE_CLASS_TYPE_P (type) && (convtype & CONV_FORCE_TEMP))
696 /* We need a new temporary; don't take this shortcut. */;
697 else if (same_type_ignoring_top_level_qualifiers_p (type, TREE_TYPE (e)))
699 if (same_type_p (type, TREE_TYPE (e)))
700 /* The call to fold will not always remove the NOP_EXPR as
701 might be expected, since if one of the types is a typedef;
702 the comparison in fold is just equality of pointers, not a
703 call to comptypes. We don't call fold in this case because
704 that can result in infinite recursion; fold will call
705 convert, which will call ocp_convert, etc. */
707 /* For complex data types, we need to perform componentwise
709 else if (TREE_CODE (type) == COMPLEX_TYPE)
710 return convert_to_complex_maybe_fold (type, e, dofold);
711 else if (VECTOR_TYPE_P (type))
712 return convert_to_vector (type, e);
713 else if (TREE_CODE (e) == TARGET_EXPR)
715 /* Don't build a NOP_EXPR of class type. Instead, change the
716 type of the temporary. */
717 TREE_TYPE (e) = TREE_TYPE (TARGET_EXPR_SLOT (e)) = type;
722 /* We shouldn't be treating objects of ADDRESSABLE type as
724 gcc_assert (!TREE_ADDRESSABLE (type));
725 return build_nop (type, e);
729 e1 = targetm.convert_to_type (type, e);
733 if (code == VOID_TYPE && (convtype & CONV_STATIC))
735 e = convert_to_void (e, ICV_CAST, complain);
739 if (INTEGRAL_CODE_P (code))
741 tree intype = TREE_TYPE (e);
744 if (TREE_CODE (type) == ENUMERAL_TYPE)
746 /* enum = enum, enum = int, enum = float, (enum)pointer are all
748 if (((INTEGRAL_OR_ENUMERATION_TYPE_P (intype)
749 || TREE_CODE (intype) == REAL_TYPE)
750 && ! (convtype & CONV_STATIC))
751 || TYPE_PTR_P (intype))
753 if (complain & tf_error)
754 permerror (loc, "conversion from %q#T to %q#T", intype, type);
756 return error_mark_node;
759 /* [expr.static.cast]
761 8. A value of integral or enumeration type can be explicitly
762 converted to an enumeration type. The value is unchanged if
763 the original value is within the range of the enumeration
764 values. Otherwise, the resulting enumeration value is
766 if ((complain & tf_warning)
767 && TREE_CODE (e) == INTEGER_CST
768 && ENUM_UNDERLYING_TYPE (type)
769 && !int_fits_type_p (e, ENUM_UNDERLYING_TYPE (type)))
770 warning_at (loc, OPT_Wconversion,
771 "the result of the conversion is unspecified because "
772 "%qE is outside the range of type %qT",
775 if (MAYBE_CLASS_TYPE_P (intype))
778 rval = build_type_conversion (type, e);
781 if (complain & tf_error)
782 error_at (loc, "%q#T used where a %qT was expected", intype, type);
783 return error_mark_node;
785 if (code == BOOLEAN_TYPE)
787 if (VOID_TYPE_P (intype))
789 if (complain & tf_error)
791 "could not convert %qE from %<void%> to %<bool%>",
793 return error_mark_node;
796 /* We can't implicitly convert a scoped enum to bool, so convert
797 to the underlying type first. */
798 if (SCOPED_ENUM_P (intype) && (convtype & CONV_STATIC))
799 e = build_nop (ENUM_UNDERLYING_TYPE (intype), e);
800 return cp_truthvalue_conversion (e);
803 converted = convert_to_integer_maybe_fold (type, e, dofold);
805 /* Ignore any integer overflow caused by the conversion. */
806 return ignore_overflows (converted, e);
808 if (NULLPTR_TYPE_P (type) && e && null_ptr_cst_p (e))
810 if (complain & tf_warning)
811 maybe_warn_zero_as_null_pointer_constant (e, loc);
814 if (POINTER_TYPE_P (type) || TYPE_PTRMEM_P (type))
815 return cp_convert_to_pointer (type, e, dofold, complain);
816 if (code == VECTOR_TYPE)
818 tree in_vtype = TREE_TYPE (e);
819 if (MAYBE_CLASS_TYPE_P (in_vtype))
822 ret_val = build_type_conversion (type, e);
825 if (complain & tf_error)
826 error_at (loc, "%q#T used where a %qT was expected",
828 return error_mark_node;
830 return convert_to_vector (type, e);
832 if (code == REAL_TYPE || code == COMPLEX_TYPE)
834 if (MAYBE_CLASS_TYPE_P (TREE_TYPE (e)))
837 rval = build_type_conversion (type, e);
840 else if (complain & tf_error)
842 "%q#T used where a floating point value was expected",
845 if (code == REAL_TYPE)
846 return convert_to_real_maybe_fold (type, e, dofold);
847 else if (code == COMPLEX_TYPE)
848 return convert_to_complex_maybe_fold (type, e, dofold);
851 /* New C++ semantics: since assignment is now based on
852 memberwise copying, if the rhs type is derived from the
853 lhs type, then we may still do a conversion. */
854 if (RECORD_OR_UNION_CODE_P (code))
856 tree dtype = TREE_TYPE (e);
857 tree ctor = NULL_TREE;
859 dtype = TYPE_MAIN_VARIANT (dtype);
861 /* Conversion between aggregate types. New C++ semantics allow
862 objects of derived type to be cast to objects of base type.
863 Old semantics only allowed this between pointers.
865 There may be some ambiguity between using a constructor
866 vs. using a type conversion operator when both apply. */
870 if (abstract_virtuals_error_sfinae (NULL_TREE, type, complain))
871 return error_mark_node;
873 if (BRACE_ENCLOSED_INITIALIZER_P (ctor))
874 ctor = perform_implicit_conversion (type, ctor, complain);
875 else if ((flags & LOOKUP_ONLYCONVERTING)
876 && ! (CLASS_TYPE_P (dtype) && DERIVED_FROM_P (type, dtype)))
877 /* For copy-initialization, first we create a temp of the proper type
878 with a user-defined conversion sequence, then we direct-initialize
879 the target with the temp (see [dcl.init]). */
880 ctor = build_user_type_conversion (type, ctor, flags, complain);
883 vec<tree, va_gc> *ctor_vec = make_tree_vector_single (ctor);
884 ctor = build_special_member_call (NULL_TREE,
885 complete_ctor_identifier,
887 type, flags, complain);
888 release_tree_vector (ctor_vec);
891 return build_cplus_new (type, ctor, complain);
894 if (complain & tf_error)
896 /* If the conversion failed and expr was an invalid use of pointer to
897 member function, try to report a meaningful error. */
898 if (invalid_nonstatic_memfn_p (loc, expr, complain))
899 /* We displayed the error message. */;
901 error_at (loc, "conversion from %qT to non-scalar type %qT requested",
902 TREE_TYPE (expr), type);
904 return error_mark_node;
907 /* If CALL is a call, return the callee; otherwise null. */
910 cp_get_callee (tree call)
912 if (call == NULL_TREE)
914 else if (TREE_CODE (call) == CALL_EXPR)
915 return CALL_EXPR_FN (call);
916 else if (TREE_CODE (call) == AGGR_INIT_EXPR)
917 return AGGR_INIT_EXPR_FN (call);
921 /* FN is the callee of a CALL_EXPR or AGGR_INIT_EXPR; return the FUNCTION_DECL
925 cp_get_fndecl_from_callee (tree fn)
929 if (TREE_CODE (fn) == FUNCTION_DECL)
931 tree type = TREE_TYPE (fn);
932 if (type == unknown_type_node)
934 gcc_assert (POINTER_TYPE_P (type));
935 fn = maybe_constant_init (fn);
937 if (TREE_CODE (fn) == ADDR_EXPR)
939 fn = TREE_OPERAND (fn, 0);
940 if (TREE_CODE (fn) == FUNCTION_DECL)
946 /* Like get_callee_fndecl, but handles AGGR_INIT_EXPR as well and uses the
947 constexpr machinery. */
950 cp_get_callee_fndecl (tree call)
952 return cp_get_fndecl_from_callee (cp_get_callee (call));
955 /* Subroutine of convert_to_void. Warn if we're discarding something with
956 attribute [[nodiscard]]. */
959 maybe_warn_nodiscard (tree expr, impl_conv_void implicit)
962 if (TREE_CODE (expr) == TARGET_EXPR)
963 call = TARGET_EXPR_INITIAL (expr);
964 location_t loc = EXPR_LOC_OR_LOC (call, input_location);
965 tree callee = cp_get_callee (call);
969 tree type = TREE_TYPE (callee);
970 if (TYPE_PTRMEMFUNC_P (type))
971 type = TYPE_PTRMEMFUNC_FN_TYPE (type);
972 if (POINTER_TYPE_P (type))
973 type = TREE_TYPE (type);
975 tree rettype = TREE_TYPE (type);
976 tree fn = cp_get_fndecl_from_callee (callee);
977 if (implicit != ICV_CAST && fn
978 && lookup_attribute ("nodiscard", DECL_ATTRIBUTES (fn)))
980 if (warning_at (loc, OPT_Wunused_result,
981 "ignoring return value of %qD, "
982 "declared with attribute nodiscard", fn))
983 inform (DECL_SOURCE_LOCATION (fn), "declared here");
985 else if (implicit != ICV_CAST
986 && lookup_attribute ("nodiscard", TYPE_ATTRIBUTES (rettype)))
988 if (warning_at (loc, OPT_Wunused_result,
989 "ignoring returned value of type %qT, "
990 "declared with attribute nodiscard", rettype))
993 inform (DECL_SOURCE_LOCATION (fn),
994 "in call to %qD, declared here", fn);
995 inform (DECL_SOURCE_LOCATION (TYPE_NAME (rettype)),
996 "%qT declared here", rettype);
999 else if (TREE_CODE (expr) == TARGET_EXPR
1000 && lookup_attribute ("warn_unused_result", TYPE_ATTRIBUTES (type)))
1002 /* The TARGET_EXPR confuses do_warn_unused_result into thinking that the
1003 result is used, so handle that case here. */
1006 if (warning_at (loc, OPT_Wunused_result,
1007 "ignoring return value of %qD, "
1008 "declared with attribute warn_unused_result",
1010 inform (DECL_SOURCE_LOCATION (fn), "declared here");
1013 warning_at (loc, OPT_Wunused_result,
1014 "ignoring return value of function "
1015 "declared with attribute warn_unused_result");
1019 /* When an expression is used in a void context, its value is discarded and
1020 no lvalue-rvalue and similar conversions happen [expr.static.cast/4,
1021 stmt.expr/1, expr.comma/1]. This permits dereferencing an incomplete type
1022 in a void context. The C++ standard does not define what an `access' to an
1023 object is, but there is reason to believe that it is the lvalue to rvalue
1024 conversion -- if it were not, `*&*p = 1' would violate [expr]/4 in that it
1025 accesses `*p' not to calculate the value to be stored. But, dcl.type.cv/8
1026 indicates that volatile semantics should be the same between C and C++
1027 where ever possible. C leaves it implementation defined as to what
1028 constitutes an access to a volatile. So, we interpret `*vp' as a read of
1029 the volatile object `vp' points to, unless that is an incomplete type. For
1030 volatile references we do not do this interpretation, because that would
1031 make it impossible to ignore the reference return value from functions. We
1032 issue warnings in the confusing cases.
1034 The IMPLICIT is ICV_CAST when the user is explicitly converting an expression
1035 to void via a cast. If an expression is being implicitly converted, IMPLICIT
1036 indicates the context of the implicit conversion. */
1039 convert_to_void (tree expr, impl_conv_void implicit, tsubst_flags_t complain)
1041 location_t loc = EXPR_LOC_OR_LOC (expr, input_location);
1043 if (expr == error_mark_node
1044 || TREE_TYPE (expr) == error_mark_node)
1045 return error_mark_node;
1047 if (implicit == ICV_CAST)
1048 mark_exp_read (expr);
1053 while (TREE_CODE (exprv) == COMPOUND_EXPR)
1054 exprv = TREE_OPERAND (exprv, 1);
1056 || handled_component_p (exprv)
1057 || INDIRECT_REF_P (exprv))
1058 /* Expr is not being 'used' here, otherwise we whould have
1059 called mark_{rl}value_use use here, which would have in turn
1060 called mark_exp_read. Rather, we call mark_exp_read directly
1061 to avoid some warnings when
1062 -Wunused-but-set-{variable,parameter} is in effect. */
1063 mark_exp_read (exprv);
1066 if (!TREE_TYPE (expr))
1068 if (invalid_nonstatic_memfn_p (loc, expr, complain))
1069 return error_mark_node;
1070 if (TREE_CODE (expr) == PSEUDO_DTOR_EXPR)
1072 if (complain & tf_error)
1073 error_at (loc, "pseudo-destructor is not called");
1074 return error_mark_node;
1076 if (VOID_TYPE_P (TREE_TYPE (expr)))
1078 switch (TREE_CODE (expr))
1082 /* The two parts of a cond expr might be separate lvalues. */
1083 tree op1 = TREE_OPERAND (expr,1);
1084 tree op2 = TREE_OPERAND (expr,2);
1085 bool side_effects = ((op1 && TREE_SIDE_EFFECTS (op1))
1086 || TREE_SIDE_EFFECTS (op2));
1087 tree new_op1, new_op2;
1088 new_op1 = NULL_TREE;
1089 if (implicit != ICV_CAST && !side_effects)
1092 new_op1 = convert_to_void (op1, ICV_SECOND_OF_COND, complain);
1093 new_op2 = convert_to_void (op2, ICV_THIRD_OF_COND, complain);
1098 new_op1 = convert_to_void (op1, ICV_CAST, complain);
1099 new_op2 = convert_to_void (op2, ICV_CAST, complain);
1102 expr = build3 (COND_EXPR, TREE_TYPE (new_op2),
1103 TREE_OPERAND (expr, 0), new_op1, new_op2);
1109 /* The second part of a compound expr contains the value. */
1110 tree op1 = TREE_OPERAND (expr,1);
1112 if (implicit != ICV_CAST && !TREE_NO_WARNING (expr))
1113 new_op1 = convert_to_void (op1, ICV_RIGHT_OF_COMMA, complain);
1115 new_op1 = convert_to_void (op1, ICV_CAST, complain);
1119 tree t = build2 (COMPOUND_EXPR, TREE_TYPE (new_op1),
1120 TREE_OPERAND (expr, 0), new_op1);
1127 case NON_LVALUE_EXPR:
1129 /* These have already decayed to rvalue. */
1132 case CALL_EXPR: /* We have a special meaning for volatile void fn(). */
1133 maybe_warn_nodiscard (expr, implicit);
1138 tree type = TREE_TYPE (expr);
1139 int is_reference = TREE_CODE (TREE_TYPE (TREE_OPERAND (expr, 0)))
1141 int is_volatile = TYPE_VOLATILE (type);
1142 int is_complete = COMPLETE_TYPE_P (complete_type (type));
1144 /* Can't load the value if we don't know the type. */
1145 if (is_volatile && !is_complete)
1147 if (complain & tf_warning)
1151 warning_at (loc, 0, "conversion to void will not access "
1152 "object of incomplete type %qT", type);
1154 case ICV_SECOND_OF_COND:
1155 warning_at (loc, 0, "indirection will not access object of "
1156 "incomplete type %qT in second operand "
1157 "of conditional expression", type);
1159 case ICV_THIRD_OF_COND:
1160 warning_at (loc, 0, "indirection will not access object of "
1161 "incomplete type %qT in third operand "
1162 "of conditional expression", type);
1164 case ICV_RIGHT_OF_COMMA:
1165 warning_at (loc, 0, "indirection will not access object of "
1166 "incomplete type %qT in right operand of "
1167 "comma operator", type);
1169 case ICV_LEFT_OF_COMMA:
1170 warning_at (loc, 0, "indirection will not access object of "
1171 "incomplete type %qT in left operand of "
1172 "comma operator", type);
1175 warning_at (loc, 0, "indirection will not access object of "
1176 "incomplete type %qT in statement", type);
1178 case ICV_THIRD_IN_FOR:
1179 warning_at (loc, 0, "indirection will not access object of "
1180 "incomplete type %qT in for increment "
1181 "expression", type);
1187 /* Don't load the value if this is an implicit dereference, or if
1188 the type needs to be handled by ctors/dtors. */
1189 else if (is_volatile && is_reference)
1191 if (complain & tf_warning)
1195 warning_at (loc, 0, "conversion to void will not access "
1196 "object of type %qT", type);
1198 case ICV_SECOND_OF_COND:
1199 warning_at (loc, 0, "implicit dereference will not access "
1200 "object of type %qT in second operand of "
1201 "conditional expression", type);
1203 case ICV_THIRD_OF_COND:
1204 warning_at (loc, 0, "implicit dereference will not access "
1205 "object of type %qT in third operand of "
1206 "conditional expression", type);
1208 case ICV_RIGHT_OF_COMMA:
1209 warning_at (loc, 0, "implicit dereference will not access "
1210 "object of type %qT in right operand of "
1211 "comma operator", type);
1213 case ICV_LEFT_OF_COMMA:
1214 warning_at (loc, 0, "implicit dereference will not access "
1215 "object of type %qT in left operand of comma "
1219 warning_at (loc, 0, "implicit dereference will not access "
1220 "object of type %qT in statement", type);
1222 case ICV_THIRD_IN_FOR:
1223 warning_at (loc, 0, "implicit dereference will not access "
1224 "object of type %qT in for increment expression",
1231 else if (is_volatile && TREE_ADDRESSABLE (type))
1233 if (complain & tf_warning)
1237 warning_at (loc, 0, "conversion to void will not access "
1238 "object of non-trivially-copyable type %qT",
1241 case ICV_SECOND_OF_COND:
1242 warning_at (loc, 0, "indirection will not access object of "
1243 "non-trivially-copyable type %qT in second "
1244 "operand of conditional expression", type);
1246 case ICV_THIRD_OF_COND:
1247 warning_at (loc, 0, "indirection will not access object of "
1248 "non-trivially-copyable type %qT in third "
1249 "operand of conditional expression", type);
1251 case ICV_RIGHT_OF_COMMA:
1252 warning_at (loc, 0, "indirection will not access object of "
1253 "non-trivially-copyable type %qT in right "
1254 "operand of comma operator", type);
1256 case ICV_LEFT_OF_COMMA:
1257 warning_at (loc, 0, "indirection will not access object of "
1258 "non-trivially-copyable type %qT in left "
1259 "operand of comma operator", type);
1262 warning_at (loc, 0, "indirection will not access object of "
1263 "non-trivially-copyable type %qT in statement",
1266 case ICV_THIRD_IN_FOR:
1267 warning_at (loc, 0, "indirection will not access object of "
1268 "non-trivially-copyable type %qT in for "
1269 "increment expression", type);
1275 if (is_reference || !is_volatile || !is_complete || TREE_ADDRESSABLE (type))
1277 /* Emit a warning (if enabled) when the "effect-less" INDIRECT_REF
1278 operation is stripped off. Note that we don't warn about
1279 - an expression with TREE_NO_WARNING set. (For an example of
1280 such expressions, see build_over_call in call.c.)
1281 - automatic dereferencing of references, since the user cannot
1282 control it. (See also warn_if_unused_value() in c-common.c.) */
1283 if (warn_unused_value
1284 && implicit != ICV_CAST
1285 && (complain & tf_warning)
1286 && !TREE_NO_WARNING (expr)
1288 warning_at (loc, OPT_Wunused_value, "value computed is not used");
1289 expr = TREE_OPERAND (expr, 0);
1297 /* External variables might be incomplete. */
1298 tree type = TREE_TYPE (expr);
1299 int is_complete = COMPLETE_TYPE_P (complete_type (type));
1301 if (TYPE_VOLATILE (type) && !is_complete && (complain & tf_warning))
1305 warning_at (loc, 0, "conversion to void will not access "
1306 "object %qE of incomplete type %qT", expr, type);
1308 case ICV_SECOND_OF_COND:
1309 warning_at (loc, 0, "variable %qE of incomplete type %qT will "
1310 "not be accessed in second operand of "
1311 "conditional expression", expr, type);
1313 case ICV_THIRD_OF_COND:
1314 warning_at (loc, 0, "variable %qE of incomplete type %qT will "
1315 "not be accessed in third operand of "
1316 "conditional expression", expr, type);
1318 case ICV_RIGHT_OF_COMMA:
1319 warning_at (loc, 0, "variable %qE of incomplete type %qT will "
1320 "not be accessed in right operand of comma operator",
1323 case ICV_LEFT_OF_COMMA:
1324 warning_at (loc, 0, "variable %qE of incomplete type %qT will "
1325 "not be accessed in left operand of comma operator",
1329 warning_at (loc, 0, "variable %qE of incomplete type %qT will "
1330 "not be accessed in statement", expr, type);
1332 case ICV_THIRD_IN_FOR:
1333 warning_at (loc, 0, "variable %qE of incomplete type %qT will "
1334 "not be accessed in for increment expression",
1345 /* Don't bother with the temporary object returned from a function if
1346 we don't use it, don't need to destroy it, and won't abort in
1347 assign_temp. We'll still
1348 allocate space for it in expand_call or declare_return_variable,
1349 but we don't need to track it through all the tree phases. */
1350 if (TARGET_EXPR_IMPLICIT_P (expr)
1351 && !TREE_ADDRESSABLE (TREE_TYPE (expr)))
1353 tree init = TARGET_EXPR_INITIAL (expr);
1354 if (TREE_CODE (init) == AGGR_INIT_EXPR
1355 && !AGGR_INIT_VIA_CTOR_P (init))
1357 tree fn = AGGR_INIT_EXPR_FN (init);
1358 expr = build_call_array_loc (input_location,
1359 TREE_TYPE (TREE_TYPE
1362 aggr_init_expr_nargs (init),
1363 AGGR_INIT_EXPR_ARGP (init));
1366 maybe_warn_nodiscard (expr, implicit);
1371 expr = resolve_nondeduced_context (expr, complain);
1375 if (TREE_CODE (probe) == ADDR_EXPR)
1376 probe = TREE_OPERAND (expr, 0);
1377 if (type_unknown_p (probe))
1379 /* [over.over] enumerates the places where we can take the address
1380 of an overloaded function, and this is not one of them. */
1381 if (complain & tf_error)
1385 error_at (loc, "conversion to void "
1386 "cannot resolve address of overloaded function");
1388 case ICV_SECOND_OF_COND:
1389 error_at (loc, "second operand of conditional expression "
1390 "cannot resolve address of overloaded function");
1392 case ICV_THIRD_OF_COND:
1393 error_at (loc, "third operand of conditional expression "
1394 "cannot resolve address of overloaded function");
1396 case ICV_RIGHT_OF_COMMA:
1397 error_at (loc, "right operand of comma operator "
1398 "cannot resolve address of overloaded function");
1400 case ICV_LEFT_OF_COMMA:
1401 error_at (loc, "left operand of comma operator "
1402 "cannot resolve address of overloaded function");
1405 error_at (loc, "statement "
1406 "cannot resolve address of overloaded function");
1408 case ICV_THIRD_IN_FOR:
1409 error_at (loc, "for increment expression "
1410 "cannot resolve address of overloaded function");
1414 return error_mark_node;
1417 else if (implicit != ICV_CAST && probe == expr && is_overloaded_fn (probe))
1419 /* Only warn when there is no &. */
1420 if (complain & tf_warning)
1423 case ICV_SECOND_OF_COND:
1424 warning_at (loc, OPT_Waddress,
1425 "second operand of conditional expression "
1426 "is a reference, not call, to function %qE", expr);
1428 case ICV_THIRD_OF_COND:
1429 warning_at (loc, OPT_Waddress,
1430 "third operand of conditional expression "
1431 "is a reference, not call, to function %qE", expr);
1433 case ICV_RIGHT_OF_COMMA:
1434 warning_at (loc, OPT_Waddress,
1435 "right operand of comma operator "
1436 "is a reference, not call, to function %qE", expr);
1438 case ICV_LEFT_OF_COMMA:
1439 warning_at (loc, OPT_Waddress,
1440 "left operand of comma operator "
1441 "is a reference, not call, to function %qE", expr);
1444 warning_at (loc, OPT_Waddress,
1445 "statement is a reference, not call, to function %qE",
1448 case ICV_THIRD_IN_FOR:
1449 warning_at (loc, OPT_Waddress,
1450 "for increment expression "
1451 "is a reference, not call, to function %qE", expr);
1457 if (TREE_CODE (expr) == COMPONENT_REF)
1458 expr = TREE_OPERAND (expr, 0);
1462 if (expr != error_mark_node && !VOID_TYPE_P (TREE_TYPE (expr)))
1464 if (implicit != ICV_CAST
1465 && warn_unused_value
1466 && !TREE_NO_WARNING (expr)
1467 && !processing_template_decl)
1469 /* The middle end does not warn about expressions that have
1470 been explicitly cast to void, so we must do so here. */
1471 if (!TREE_SIDE_EFFECTS (expr)) {
1472 if (complain & tf_warning)
1475 case ICV_SECOND_OF_COND:
1476 warning_at (loc, OPT_Wunused_value,
1477 "second operand of conditional expression "
1480 case ICV_THIRD_OF_COND:
1481 warning_at (loc, OPT_Wunused_value,
1482 "third operand of conditional expression "
1485 case ICV_RIGHT_OF_COMMA:
1486 warning_at (loc, OPT_Wunused_value,
1487 "right operand of comma operator has no effect");
1489 case ICV_LEFT_OF_COMMA:
1490 warning_at (loc, OPT_Wunused_value,
1491 "left operand of comma operator has no effect");
1494 warning_at (loc, OPT_Wunused_value,
1495 "statement has no effect");
1497 case ICV_THIRD_IN_FOR:
1498 warning_at (loc, OPT_Wunused_value,
1499 "for increment expression has no effect");
1508 enum tree_code code;
1509 enum tree_code_class tclass;
1512 /* We might like to warn about (say) "(int) f()", as the
1513 cast has no effect, but the compiler itself will
1514 generate implicit conversions under some
1515 circumstances. (For example a block copy will be
1516 turned into a call to "__builtin_memcpy", with a
1517 conversion of the return value to an appropriate
1518 type.) So, to avoid false positives, we strip
1519 conversions. Do not use STRIP_NOPs because it will
1520 not strip conversions to "void", as that is not a
1521 mode-preserving conversion. */
1522 while (TREE_CODE (e) == NOP_EXPR)
1523 e = TREE_OPERAND (e, 0);
1525 code = TREE_CODE (e);
1526 tclass = TREE_CODE_CLASS (code);
1527 if ((tclass == tcc_comparison
1528 || tclass == tcc_unary
1529 || (tclass == tcc_binary
1530 && !(code == MODIFY_EXPR
1531 || code == INIT_EXPR
1532 || code == PREDECREMENT_EXPR
1533 || code == PREINCREMENT_EXPR
1534 || code == POSTDECREMENT_EXPR
1535 || code == POSTINCREMENT_EXPR))
1536 || code == VEC_PERM_EXPR
1537 || code == VEC_COND_EXPR)
1538 && (complain & tf_warning))
1539 warning_at (loc, OPT_Wunused_value, "value computed is not used");
1542 expr = build1 (CONVERT_EXPR, void_type_node, expr);
1544 if (! TREE_SIDE_EFFECTS (expr))
1549 /* Create an expression whose value is that of EXPR,
1550 converted to type TYPE. The TREE_TYPE of the value
1551 is always TYPE. This function implements all reasonable
1552 conversions; callers should filter out those that are
1553 not permitted by the language being compiled.
1555 Most of this routine is from build_reinterpret_cast.
1557 The back end cannot call cp_convert (what was convert) because
1558 conversions to/from basetypes may involve memory references
1559 (vbases) and adding or subtracting small values (multiple
1560 inheritance), but it calls convert from the constant folding code
1561 on subtrees of already built trees after it has ripped them apart.
1563 Also, if we ever support range variables, we'll probably also have to
1564 do a little bit more work. */
1567 convert (tree type, tree expr)
1571 if (type == error_mark_node || expr == error_mark_node)
1572 return error_mark_node;
1574 intype = TREE_TYPE (expr);
1576 if (POINTER_TYPE_P (type) && POINTER_TYPE_P (intype))
1577 return build_nop (type, expr);
1579 return ocp_convert (type, expr, CONV_BACKEND_CONVERT,
1580 LOOKUP_NORMAL|LOOKUP_NO_CONVERSION,
1581 tf_warning_or_error);
1584 /* Like cp_convert, except permit conversions to take place which
1585 are not normally allowed due to access restrictions
1586 (such as conversion from sub-type to private super-type). */
1589 convert_force (tree type, tree expr, int convtype, tsubst_flags_t complain)
1592 enum tree_code code = TREE_CODE (type);
1594 if (code == REFERENCE_TYPE)
1595 return convert_to_reference (type, e, CONV_C_CAST, 0,
1596 NULL_TREE, complain);
1598 if (code == POINTER_TYPE)
1599 return convert_to_pointer_force (type, e, complain);
1601 /* From typeck.c convert_for_assignment */
1602 if (((TYPE_PTR_P (TREE_TYPE (e)) && TREE_CODE (e) == ADDR_EXPR
1603 && TREE_CODE (TREE_TYPE (TREE_TYPE (e))) == METHOD_TYPE)
1604 || integer_zerop (e)
1605 || TYPE_PTRMEMFUNC_P (TREE_TYPE (e)))
1606 && TYPE_PTRMEMFUNC_P (type))
1607 /* compatible pointer to member functions. */
1608 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), e, 1,
1609 /*c_cast_p=*/1, complain);
1611 return ocp_convert (type, e, CONV_C_CAST|convtype, LOOKUP_NORMAL, complain);
1614 /* Convert an aggregate EXPR to type XTYPE. If a conversion
1615 exists, return the attempted conversion. This may
1616 return ERROR_MARK_NODE if the conversion is not
1617 allowed (references private members, etc).
1618 If no conversion exists, NULL_TREE is returned.
1620 FIXME: Ambiguity checking is wrong. Should choose one by the implicit
1621 object parameter, or by the second standard conversion sequence if
1622 that doesn't do it. This will probably wait for an overloading rewrite.
1626 build_type_conversion (tree xtype, tree expr)
1628 /* C++: check to see if we can convert this aggregate type
1629 into the required type. */
1630 return build_user_type_conversion (xtype, expr, LOOKUP_NORMAL,
1631 tf_warning_or_error);
1634 /* Convert the given EXPR to one of a group of types suitable for use in an
1635 expression. DESIRES is a combination of various WANT_* flags (q.v.)
1636 which indicates which types are suitable. If COMPLAIN is true, complain
1637 about ambiguity; otherwise, the caller will deal with it. */
1640 build_expr_type_conversion (int desires, tree expr, bool complain)
1642 tree basetype = TREE_TYPE (expr);
1643 tree conv = NULL_TREE;
1644 tree winner = NULL_TREE;
1646 if (expr == null_node
1647 && (desires & WANT_INT)
1648 && !(desires & WANT_NULL))
1650 source_location loc =
1651 expansion_point_location_if_in_system_header (input_location);
1653 warning_at (loc, OPT_Wconversion_null,
1654 "converting NULL to non-pointer type");
1657 if (basetype == error_mark_node)
1658 return error_mark_node;
1660 if (! MAYBE_CLASS_TYPE_P (basetype))
1661 switch (TREE_CODE (basetype))
1664 if ((desires & WANT_NULL) && null_ptr_cst_p (expr))
1666 /* else fall through... */
1669 return (desires & WANT_INT) ? expr : NULL_TREE;
1671 return (desires & WANT_ENUM) ? expr : NULL_TREE;
1673 return (desires & WANT_FLOAT) ? expr : NULL_TREE;
1675 return (desires & WANT_POINTER) ? expr : NULL_TREE;
1679 return (desires & WANT_POINTER) ? decay_conversion (expr,
1680 tf_warning_or_error)
1685 if ((desires & WANT_VECTOR_OR_COMPLEX) == 0)
1687 switch (TREE_CODE (TREE_TYPE (basetype)))
1691 return (desires & WANT_INT) ? expr : NULL_TREE;
1693 return (desires & WANT_ENUM) ? expr : NULL_TREE;
1695 return (desires & WANT_FLOAT) ? expr : NULL_TREE;
1704 /* The code for conversions from class type is currently only used for
1705 delete expressions. Other expressions are handled by build_new_op. */
1706 if (!complete_type_or_maybe_complain (basetype, expr, complain))
1707 return error_mark_node;
1708 if (!TYPE_HAS_CONVERSION (basetype))
1711 for (conv = lookup_conversions (basetype); conv; conv = TREE_CHAIN (conv))
1715 tree cand = TREE_VALUE (conv);
1716 cand = OVL_CURRENT (cand);
1718 if (winner && winner == cand)
1721 if (DECL_NONCONVERTING_P (cand))
1724 candidate = non_reference (TREE_TYPE (TREE_TYPE (cand)));
1726 switch (TREE_CODE (candidate))
1730 win = (desires & WANT_INT); break;
1732 win = (desires & WANT_ENUM); break;
1734 win = (desires & WANT_FLOAT); break;
1736 win = (desires & WANT_POINTER); break;
1740 if ((desires & WANT_VECTOR_OR_COMPLEX) == 0)
1742 switch (TREE_CODE (TREE_TYPE (candidate)))
1746 win = (desires & WANT_INT); break;
1748 win = (desires & WANT_ENUM); break;
1750 win = (desires & WANT_FLOAT); break;
1757 /* A wildcard could be instantiated to match any desired
1758 type, but we can't deduce the template argument. */
1759 if (WILDCARD_TYPE_P (candidate))
1766 if (TREE_CODE (cand) == TEMPLATE_DECL)
1769 error ("default type conversion can't deduce template"
1770 " argument for %qD", cand);
1771 return error_mark_node;
1777 = non_reference (TREE_TYPE (TREE_TYPE (winner)));
1779 if (!same_type_ignoring_top_level_qualifiers_p (winner_type,
1784 error ("ambiguous default type conversion from %qT",
1786 inform (input_location,
1787 " candidate conversions include %qD and %qD",
1790 return error_mark_node;
1800 tree type = non_reference (TREE_TYPE (TREE_TYPE (winner)));
1801 return build_user_type_conversion (type, expr, LOOKUP_NORMAL,
1802 tf_warning_or_error);
1808 /* Implements integral promotion (4.1) and float->double promotion. */
1811 type_promotes_to (tree type)
1815 if (type == error_mark_node)
1816 return error_mark_node;
1818 type = TYPE_MAIN_VARIANT (type);
1820 /* Check for promotions of target-defined types first. */
1821 promoted_type = targetm.promoted_type (type);
1823 return promoted_type;
1825 /* bool always promotes to int (not unsigned), even if it's the same
1827 if (TREE_CODE (type) == BOOLEAN_TYPE)
1828 type = integer_type_node;
1830 /* Normally convert enums to int, but convert wide enums to something
1831 wider. Scoped enums don't promote, but pretend they do for backward
1832 ABI bug compatibility wrt varargs. */
1833 else if (TREE_CODE (type) == ENUMERAL_TYPE
1834 || type == char16_type_node
1835 || type == char32_type_node
1836 || type == wchar_type_node)
1838 int precision = MAX (TYPE_PRECISION (type),
1839 TYPE_PRECISION (integer_type_node));
1840 tree totype = c_common_type_for_size (precision, 0);
1842 if (TREE_CODE (prom) == ENUMERAL_TYPE)
1843 prom = ENUM_UNDERLYING_TYPE (prom);
1844 if (TYPE_UNSIGNED (prom)
1845 && ! int_fits_type_p (TYPE_MAX_VALUE (prom), totype))
1846 prom = c_common_type_for_size (precision, 1);
1849 if (SCOPED_ENUM_P (type))
1851 if (abi_version_crosses (6)
1852 && TYPE_MODE (prom) != TYPE_MODE (type))
1853 warning (OPT_Wabi, "scoped enum %qT passed through ... as "
1854 "%qT before -fabi-version=6, %qT after",
1855 type, prom, ENUM_UNDERLYING_TYPE (type));
1856 if (!abi_version_at_least (6))
1862 else if (c_promoting_integer_type_p (type))
1864 /* Retain unsignedness if really not getting bigger. */
1865 if (TYPE_UNSIGNED (type)
1866 && TYPE_PRECISION (type) == TYPE_PRECISION (integer_type_node))
1867 type = unsigned_type_node;
1869 type = integer_type_node;
1871 else if (type == float_type_node)
1872 type = double_type_node;
1877 /* The routines below this point are carefully written to conform to
1878 the standard. They use the same terminology, and follow the rules
1879 closely. Although they are used only in pt.c at the moment, they
1880 should presumably be used everywhere in the future. */
1882 /* Attempt to perform qualification conversions on EXPR to convert it
1883 to TYPE. Return the resulting expression, or error_mark_node if
1884 the conversion was impossible. */
1887 perform_qualification_conversions (tree type, tree expr)
1891 expr_type = TREE_TYPE (expr);
1893 if (same_type_p (type, expr_type))
1895 else if (TYPE_PTR_P (type) && TYPE_PTR_P (expr_type)
1896 && comp_ptr_ttypes (TREE_TYPE (type), TREE_TYPE (expr_type)))
1897 return build_nop (type, expr);
1898 else if (TYPE_PTRMEM_P (type) && TYPE_PTRMEM_P (expr_type)
1899 && same_type_p (TYPE_PTRMEM_CLASS_TYPE (type),
1900 TYPE_PTRMEM_CLASS_TYPE (expr_type))
1901 && comp_ptr_ttypes (TYPE_PTRMEM_POINTED_TO_TYPE (type),
1902 TYPE_PTRMEM_POINTED_TO_TYPE (expr_type)))
1903 return build_nop (type, expr);
1905 return error_mark_node;
1908 /* True iff T is a transaction-safe function type. */
1911 tx_safe_fn_type_p (tree t)
1913 if (TREE_CODE (t) != FUNCTION_TYPE
1914 && TREE_CODE (t) != METHOD_TYPE)
1916 return !!lookup_attribute ("transaction_safe", TYPE_ATTRIBUTES (t));
1919 /* Return the transaction-unsafe variant of transaction-safe function type
1923 tx_unsafe_fn_variant (tree t)
1925 gcc_assert (tx_safe_fn_type_p (t));
1926 tree attrs = remove_attribute ("transaction_safe",
1927 TYPE_ATTRIBUTES (t));
1928 return cp_build_type_attribute_variant (t, attrs);
1931 /* Return true iff FROM can convert to TO by a transaction-safety
1935 can_convert_tx_safety (tree to, tree from)
1937 return (flag_tm && tx_safe_fn_type_p (from)
1938 && same_type_p (to, tx_unsafe_fn_variant (from)));