1 /* Language-level data type conversion for GNU C++.
2 Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
3 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008
4 Free Software Foundation, Inc.
5 Hacked by Michael Tiemann (tiemann@cygnus.com)
7 This file is part of GCC.
9 GCC is free software; you can redistribute it and/or modify
10 it under the terms of the GNU General Public License as published by
11 the Free Software Foundation; either version 3, or (at your option)
14 GCC is distributed in the hope that it will be useful,
15 but WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License for more details.
19 You should have received a copy of the GNU General Public License
20 along with GCC; see the file COPYING3. If not see
21 <http://www.gnu.org/licenses/>. */
24 /* This file contains the functions for converting C++ expressions
25 to different data types. The only entry point is `convert'.
26 Every language front end must have a `convert' function
27 but what kind of conversions it does will depend on the language. */
31 #include "coretypes.h"
41 static tree cp_convert_to_pointer (tree, tree);
42 static tree convert_to_pointer_force (tree, tree);
43 static tree build_type_conversion (tree, tree);
44 static tree build_up_reference (tree, tree, int, tree);
45 static void warn_ref_binding (tree, tree, tree);
47 /* Change of width--truncation and extension of integers or reals--
48 is represented with NOP_EXPR. Proper functioning of many things
49 assumes that no other conversions can be NOP_EXPRs.
51 Conversion between integer and pointer is represented with CONVERT_EXPR.
52 Converting integer to real uses FLOAT_EXPR
53 and real to integer uses FIX_TRUNC_EXPR.
55 Here is a list of all the functions that assume that widening and
56 narrowing is always done with a NOP_EXPR:
57 In convert.c, convert_to_integer.
58 In c-typeck.c, build_binary_op_nodefault (boolean ops),
59 and c_common_truthvalue_conversion.
60 In expr.c: expand_expr, for operands of a MULT_EXPR.
61 In fold-const.c: fold.
62 In tree.c: get_narrower and get_unwidened.
64 C++: in multiple-inheritance, converting between pointers may involve
65 adjusting them by a delta stored within the class definition. */
67 /* Subroutines of `convert'. */
69 /* if converting pointer to pointer
70 if dealing with classes, check for derived->base or vice versa
71 else if dealing with method pointers, delegate
73 else if converting class, pass off to build_type_conversion
74 else try C-style pointer conversion. */
77 cp_convert_to_pointer (tree type, tree expr)
79 tree intype = TREE_TYPE (expr);
82 if (intype == error_mark_node)
83 return error_mark_node;
85 if (MAYBE_CLASS_TYPE_P (intype))
87 intype = complete_type (intype);
88 if (!COMPLETE_TYPE_P (intype))
90 error ("can't convert from incomplete type %qT to %qT",
92 return error_mark_node;
95 rval = build_type_conversion (type, expr);
98 if (rval == error_mark_node)
99 error ("conversion of %qE from %qT to %qT is ambiguous",
105 /* Handle anachronistic conversions from (::*)() to cv void* or (*)(). */
106 if (TREE_CODE (type) == POINTER_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);
113 if (TREE_CODE (TREE_TYPE (expr)) == POINTER_TYPE)
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
128 && TREE_CODE (type) == POINTER_TYPE
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, NULL);
149 if (!same_p && !binfo)
151 /* Try base to derived conversion. */
152 binfo = lookup_base (type_class, intype_class, ba_check, NULL);
155 if (binfo == error_mark_node)
156 return error_mark_node;
160 expr = build_base_path (code, expr, binfo, 0);
161 /* Add any qualifier conversions. */
162 return build_nop (type, expr);
166 if (TYPE_PTRMEMFUNC_P (type))
168 error ("cannot convert %qE from type %qT to type %qT",
170 return error_mark_node;
173 return build_nop (type, expr);
175 else if ((TYPE_PTRMEM_P (type) && TYPE_PTRMEM_P (intype))
176 || (TYPE_PTRMEMFUNC_P (type) && TYPE_PTRMEMFUNC_P (intype)))
177 return convert_ptrmem (type, expr, /*allow_inverse_p=*/false,
179 else if (TYPE_PTRMEMFUNC_P (intype))
183 if (TREE_CODE (expr) == PTRMEM_CST)
184 return cp_convert_to_pointer (type,
185 PTRMEM_CST_MEMBER (expr));
186 else if (TREE_CODE (expr) == OFFSET_REF)
188 tree object = TREE_OPERAND (expr, 0);
189 return get_member_function_from_ptrfunc (&object,
190 TREE_OPERAND (expr, 1));
193 error ("cannot convert %qE from type %qT to type %qT",
195 return error_mark_node;
198 if (integer_zerop (expr))
200 if (TYPE_PTRMEMFUNC_P (type))
201 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), expr, 0,
204 if (TYPE_PTRMEM_P (type))
206 /* A NULL pointer-to-member is represented by -1, not by
208 expr = build_int_cst_type (type, -1);
211 expr = build_int_cst (type, 0);
215 else if (TYPE_PTR_TO_MEMBER_P (type) && INTEGRAL_CODE_P (form))
217 error ("invalid conversion from %qT to %qT", intype, type);
218 return error_mark_node;
221 if (INTEGRAL_CODE_P (form))
223 if (TYPE_PRECISION (intype) == POINTER_SIZE)
224 return build1 (CONVERT_EXPR, type, expr);
225 expr = cp_convert (c_common_type_for_size (POINTER_SIZE, 0), expr);
226 /* Modes may be different but sizes should be the same. There
227 is supposed to be some integral type that is the same width
229 gcc_assert (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (expr)))
230 == GET_MODE_SIZE (TYPE_MODE (type)));
232 return convert_to_pointer (type, expr);
235 if (type_unknown_p (expr))
236 return instantiate_type (type, expr, tf_warning_or_error);
238 error ("cannot convert %qE from type %qT to type %qT",
240 return error_mark_node;
243 /* Like convert, except permit conversions to take place which
244 are not normally allowed due to access restrictions
245 (such as conversion from sub-type to private super-type). */
248 convert_to_pointer_force (tree type, tree expr)
250 tree intype = TREE_TYPE (expr);
251 enum tree_code form = TREE_CODE (intype);
253 if (form == POINTER_TYPE)
255 intype = TYPE_MAIN_VARIANT (intype);
257 if (TYPE_MAIN_VARIANT (type) != intype
258 && TREE_CODE (TREE_TYPE (type)) == RECORD_TYPE
259 && MAYBE_CLASS_TYPE_P (TREE_TYPE (type))
260 && MAYBE_CLASS_TYPE_P (TREE_TYPE (intype))
261 && TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE)
263 enum tree_code code = PLUS_EXPR;
266 binfo = lookup_base (TREE_TYPE (intype), TREE_TYPE (type),
270 binfo = lookup_base (TREE_TYPE (type), TREE_TYPE (intype),
274 if (binfo == error_mark_node)
275 return error_mark_node;
278 expr = build_base_path (code, expr, binfo, 0);
279 if (expr == error_mark_node)
280 return error_mark_node;
281 /* Add any qualifier conversions. */
282 if (!same_type_p (TREE_TYPE (TREE_TYPE (expr)),
284 expr = build_nop (type, expr);
290 return cp_convert_to_pointer (type, expr);
293 /* We are passing something to a function which requires a reference.
294 The type we are interested in is in TYPE. The initial
295 value we have to begin with is in ARG.
297 FLAGS controls how we manage access checking.
298 DIRECT_BIND in FLAGS controls how any temporaries are generated.
299 If DIRECT_BIND is set, DECL is the reference we're binding to. */
302 build_up_reference (tree type, tree arg, int flags, tree decl)
305 tree argtype = TREE_TYPE (arg);
306 tree target_type = TREE_TYPE (type);
308 gcc_assert (TREE_CODE (type) == REFERENCE_TYPE);
310 if ((flags & DIRECT_BIND) && ! real_lvalue_p (arg))
312 /* Create a new temporary variable. We can't just use a TARGET_EXPR
313 here because it needs to live as long as DECL. */
316 arg = make_temporary_var_for_ref_to_temp (decl, TREE_TYPE (arg));
318 /* Process the initializer for the declaration. */
319 DECL_INITIAL (arg) = targ;
320 cp_finish_decl (arg, targ, /*init_const_expr_p=*/false, NULL_TREE,
321 LOOKUP_ONLYCONVERTING|DIRECT_BIND);
323 else if (!(flags & DIRECT_BIND) && ! lvalue_p (arg))
324 return get_target_expr (arg);
326 /* If we had a way to wrap this up, and say, if we ever needed its
327 address, transform all occurrences of the register, into a memory
328 reference we could win better. */
329 rval = cp_build_unary_op (ADDR_EXPR, arg, 1, tf_warning_or_error);
330 if (rval == error_mark_node)
331 return error_mark_node;
333 if ((flags & LOOKUP_PROTECT)
334 && TYPE_MAIN_VARIANT (argtype) != TYPE_MAIN_VARIANT (target_type)
335 && MAYBE_CLASS_TYPE_P (argtype)
336 && MAYBE_CLASS_TYPE_P (target_type))
338 /* We go through lookup_base for the access control. */
339 tree binfo = lookup_base (argtype, target_type, ba_check, NULL);
340 if (binfo == error_mark_node)
341 return error_mark_node;
342 if (binfo == NULL_TREE)
343 return error_not_base_type (target_type, argtype);
344 rval = build_base_path (PLUS_EXPR, rval, binfo, 1);
348 = convert_to_pointer_force (build_pointer_type (target_type), rval);
349 return build_nop (type, rval);
352 /* Subroutine of convert_to_reference. REFTYPE is the target reference type.
353 INTYPE is the original rvalue type and DECL is an optional _DECL node
356 [dcl.init.ref] says that if an rvalue is used to
357 initialize a reference, then the reference must be to a
358 non-volatile const type. */
361 warn_ref_binding (tree reftype, tree intype, tree decl)
363 tree ttl = TREE_TYPE (reftype);
365 if (!CP_TYPE_CONST_NON_VOLATILE_P (ttl))
369 if (CP_TYPE_VOLATILE_P (ttl) && decl)
370 msg = "initialization of volatile reference type %q#T from"
371 " rvalue of type %qT";
372 else if (CP_TYPE_VOLATILE_P (ttl))
373 msg = "conversion to volatile reference type %q#T "
374 " from rvalue of type %qT";
376 msg = "initialization of non-const reference type %q#T from"
377 " rvalue of type %qT";
379 msg = "conversion to non-const reference type %q#T from"
380 " rvalue of type %qT";
382 permerror (input_location, msg, reftype, intype);
386 /* For C++: Only need to do one-level references, but cannot
387 get tripped up on signed/unsigned differences.
389 DECL is either NULL_TREE or the _DECL node for a reference that is being
390 initialized. It can be error_mark_node if we don't know the _DECL but
391 we know it's an initialization. */
394 convert_to_reference (tree reftype, tree expr, int convtype,
395 int flags, tree decl)
397 tree type = TYPE_MAIN_VARIANT (TREE_TYPE (reftype));
399 tree rval = NULL_TREE;
400 tree rval_as_conversion = NULL_TREE;
401 bool can_convert_intype_to_type;
403 if (TREE_CODE (type) == FUNCTION_TYPE
404 && TREE_TYPE (expr) == unknown_type_node)
405 expr = instantiate_type (type, expr,
406 (flags & LOOKUP_COMPLAIN)
407 ? tf_warning_or_error : tf_none);
409 if (expr == error_mark_node)
410 return error_mark_node;
412 intype = TREE_TYPE (expr);
414 gcc_assert (TREE_CODE (intype) != REFERENCE_TYPE);
415 gcc_assert (TREE_CODE (reftype) == REFERENCE_TYPE);
417 intype = TYPE_MAIN_VARIANT (intype);
419 can_convert_intype_to_type = can_convert (type, intype);
420 if (!can_convert_intype_to_type
421 && (convtype & CONV_IMPLICIT) && MAYBE_CLASS_TYPE_P (intype)
422 && ! (flags & LOOKUP_NO_CONVERSION))
424 /* Look for a user-defined conversion to lvalue that we can use. */
427 = build_type_conversion (reftype, expr);
429 if (rval_as_conversion && rval_as_conversion != error_mark_node
430 && real_lvalue_p (rval_as_conversion))
432 expr = rval_as_conversion;
433 rval_as_conversion = NULL_TREE;
435 can_convert_intype_to_type = 1;
439 if (((convtype & CONV_STATIC) && can_convert (intype, type))
440 || ((convtype & CONV_IMPLICIT) && can_convert_intype_to_type))
442 if (flags & LOOKUP_COMPLAIN)
444 tree ttl = TREE_TYPE (reftype);
445 tree ttr = lvalue_type (expr);
447 if (! real_lvalue_p (expr))
448 warn_ref_binding (reftype, intype, decl);
450 if (! (convtype & CONV_CONST)
451 && !at_least_as_qualified_p (ttl, ttr))
452 permerror (input_location, "conversion from %qT to %qT discards qualifiers",
456 return build_up_reference (reftype, expr, flags, decl);
458 else if ((convtype & CONV_REINTERPRET) && lvalue_p (expr))
460 /* When casting an lvalue to a reference type, just convert into
461 a pointer to the new type and deference it. This is allowed
462 by San Diego WP section 5.2.9 paragraph 12, though perhaps it
463 should be done directly (jason). (int &)ri ---> *(int*)&ri */
465 /* B* bp; A& ar = (A&)bp; is valid, but it's probably not what they
467 if (TREE_CODE (intype) == POINTER_TYPE
468 && (comptypes (TREE_TYPE (intype), type,
469 COMPARE_BASE | COMPARE_DERIVED)))
470 warning (0, "casting %qT to %qT does not dereference pointer",
473 rval = cp_build_unary_op (ADDR_EXPR, expr, 0, tf_warning_or_error);
474 if (rval != error_mark_node)
475 rval = convert_force (build_pointer_type (TREE_TYPE (reftype)),
477 if (rval != error_mark_node)
478 rval = build1 (NOP_EXPR, reftype, rval);
482 rval = convert_for_initialization (NULL_TREE, type, expr, flags,
484 tf_warning_or_error);
485 if (rval == NULL_TREE || rval == error_mark_node)
487 warn_ref_binding (reftype, intype, decl);
488 rval = build_up_reference (reftype, rval, flags, decl);
493 /* If we found a way to convert earlier, then use it. */
497 if (flags & LOOKUP_COMPLAIN)
498 error ("cannot convert type %qT to type %qT", intype, reftype);
500 return error_mark_node;
503 /* We are using a reference VAL for its value. Bash that reference all the
504 way down to its lowest form. */
507 convert_from_reference (tree val)
509 if (TREE_CODE (TREE_TYPE (val)) == REFERENCE_TYPE)
511 tree t = canonical_type_variant (TREE_TYPE (TREE_TYPE (val)));
512 tree ref = build1 (INDIRECT_REF, t, val);
514 /* We *must* set TREE_READONLY when dereferencing a pointer to const,
515 so that we get the proper error message if the result is used
516 to assign to. Also, &* is supposed to be a no-op. */
517 TREE_READONLY (ref) = CP_TYPE_CONST_P (t);
518 TREE_THIS_VOLATILE (ref) = CP_TYPE_VOLATILE_P (t);
519 TREE_SIDE_EFFECTS (ref)
520 = (TREE_THIS_VOLATILE (ref) || TREE_SIDE_EFFECTS (val));
521 REFERENCE_REF_P (ref) = 1;
528 /* Really perform an lvalue-to-rvalue conversion, including copying an
529 argument of class type into a temporary. */
532 force_rvalue (tree expr)
534 if (MAYBE_CLASS_TYPE_P (TREE_TYPE (expr)) && TREE_CODE (expr) != TARGET_EXPR)
535 expr = ocp_convert (TREE_TYPE (expr), expr,
536 CONV_IMPLICIT|CONV_FORCE_TEMP, LOOKUP_NORMAL);
538 expr = decay_conversion (expr);
543 /* C++ conversions, preference to static cast conversions. */
546 cp_convert (tree type, tree expr)
548 return ocp_convert (type, expr, CONV_OLD_CONVERT, LOOKUP_NORMAL);
551 /* C++ equivalent of convert_and_check but using cp_convert as the
554 Convert EXPR to TYPE, warning about conversion problems with constants.
555 Invoke this function on every expression that is converted implicitly,
556 i.e. because of language rules and not because of an explicit cast. */
559 cp_convert_and_check (tree type, tree expr)
563 if (TREE_TYPE (expr) == type)
566 result = cp_convert (type, expr);
568 if (!skip_evaluation && !TREE_OVERFLOW_P (expr) && result != error_mark_node)
569 warnings_for_convert_and_check (type, expr, result);
576 FLAGS indicates how we should behave. */
579 ocp_convert (tree type, tree expr, int convtype, int flags)
582 enum tree_code code = TREE_CODE (type);
583 const char *invalid_conv_diag;
585 if (error_operand_p (e) || type == error_mark_node)
586 return error_mark_node;
588 complete_type (type);
589 complete_type (TREE_TYPE (expr));
591 if ((invalid_conv_diag
592 = targetm.invalid_conversion (TREE_TYPE (expr), type)))
594 error (invalid_conv_diag);
595 return error_mark_node;
598 e = integral_constant_value (e);
600 if (MAYBE_CLASS_TYPE_P (type) && (convtype & CONV_FORCE_TEMP))
601 /* We need a new temporary; don't take this shortcut. */;
602 else if (same_type_ignoring_top_level_qualifiers_p (type, TREE_TYPE (e)))
604 if (same_type_p (type, TREE_TYPE (e)))
605 /* The call to fold will not always remove the NOP_EXPR as
606 might be expected, since if one of the types is a typedef;
607 the comparison in fold is just equality of pointers, not a
608 call to comptypes. We don't call fold in this case because
609 that can result in infinite recursion; fold will call
610 convert, which will call ocp_convert, etc. */
612 /* For complex data types, we need to perform componentwise
614 else if (TREE_CODE (type) == COMPLEX_TYPE)
615 return fold_if_not_in_template (convert_to_complex (type, e));
616 else if (TREE_CODE (e) == TARGET_EXPR)
618 /* Don't build a NOP_EXPR of class type. Instead, change the
619 type of the temporary. */
620 TREE_TYPE (e) = TREE_TYPE (TARGET_EXPR_SLOT (e)) = type;
625 /* We shouldn't be treating objects of ADDRESSABLE type as
627 gcc_assert (!TREE_ADDRESSABLE (type));
628 return fold_if_not_in_template (build_nop (type, e));
632 if (code == VOID_TYPE && (convtype & CONV_STATIC))
634 e = convert_to_void (e, /*implicit=*/NULL, tf_warning_or_error);
638 if (INTEGRAL_CODE_P (code))
640 tree intype = TREE_TYPE (e);
642 if (TREE_CODE (type) == ENUMERAL_TYPE)
644 /* enum = enum, enum = int, enum = float, (enum)pointer are all
646 if (((INTEGRAL_OR_ENUMERATION_TYPE_P (intype)
647 || TREE_CODE (intype) == REAL_TYPE)
648 && ! (convtype & CONV_STATIC))
649 || TREE_CODE (intype) == POINTER_TYPE)
651 if (flags & LOOKUP_COMPLAIN)
652 permerror (input_location, "conversion from %q#T to %q#T", intype, type);
654 if (!flag_permissive)
655 return error_mark_node;
658 /* [expr.static.cast]
660 8. A value of integral or enumeration type can be explicitly
661 converted to an enumeration type. The value is unchanged if
662 the original value is within the range of the enumeration
663 values. Otherwise, the resulting enumeration value is
665 if (TREE_CODE (expr) == INTEGER_CST && !int_fits_type_p (expr, type))
666 warning (OPT_Wconversion,
667 "the result of the conversion is unspecified because "
668 "%qE is outside the range of type %qT",
671 if (MAYBE_CLASS_TYPE_P (intype))
674 rval = build_type_conversion (type, e);
677 if (flags & LOOKUP_COMPLAIN)
678 error ("%q#T used where a %qT was expected", intype, type);
679 return error_mark_node;
681 if (code == BOOLEAN_TYPE)
682 return cp_truthvalue_conversion (e);
684 return fold_if_not_in_template (convert_to_integer (type, e));
686 if (POINTER_TYPE_P (type) || TYPE_PTR_TO_MEMBER_P (type))
687 return fold_if_not_in_template (cp_convert_to_pointer (type, e));
688 if (code == VECTOR_TYPE)
690 tree in_vtype = TREE_TYPE (e);
691 if (MAYBE_CLASS_TYPE_P (in_vtype))
694 ret_val = build_type_conversion (type, e);
697 if (flags & LOOKUP_COMPLAIN)
698 error ("%q#T used where a %qT was expected", in_vtype, type);
699 return error_mark_node;
701 return fold_if_not_in_template (convert_to_vector (type, e));
703 if (code == REAL_TYPE || code == COMPLEX_TYPE)
705 if (MAYBE_CLASS_TYPE_P (TREE_TYPE (e)))
708 rval = build_type_conversion (type, e);
712 if (flags & LOOKUP_COMPLAIN)
713 error ("%q#T used where a floating point value was expected",
716 if (code == REAL_TYPE)
717 return fold_if_not_in_template (convert_to_real (type, e));
718 else if (code == COMPLEX_TYPE)
719 return fold_if_not_in_template (convert_to_complex (type, e));
722 /* New C++ semantics: since assignment is now based on
723 memberwise copying, if the rhs type is derived from the
724 lhs type, then we may still do a conversion. */
725 if (RECORD_OR_UNION_CODE_P (code))
727 tree dtype = TREE_TYPE (e);
728 tree ctor = NULL_TREE;
730 dtype = TYPE_MAIN_VARIANT (dtype);
732 /* Conversion between aggregate types. New C++ semantics allow
733 objects of derived type to be cast to objects of base type.
734 Old semantics only allowed this between pointers.
736 There may be some ambiguity between using a constructor
737 vs. using a type conversion operator when both apply. */
741 if (abstract_virtuals_error (NULL_TREE, type))
742 return error_mark_node;
744 if (BRACE_ENCLOSED_INITIALIZER_P (ctor))
745 ctor = perform_implicit_conversion (type, ctor, tf_warning_or_error);
746 else if ((flags & LOOKUP_ONLYCONVERTING)
747 && ! (CLASS_TYPE_P (dtype) && DERIVED_FROM_P (type, dtype)))
748 /* For copy-initialization, first we create a temp of the proper type
749 with a user-defined conversion sequence, then we direct-initialize
750 the target with the temp (see [dcl.init]). */
751 ctor = build_user_type_conversion (type, ctor, flags);
753 ctor = build_special_member_call (NULL_TREE,
754 complete_ctor_identifier,
755 build_tree_list (NULL_TREE, ctor),
757 tf_warning_or_error);
759 return build_cplus_new (type, ctor);
762 if (flags & LOOKUP_COMPLAIN)
764 /* If the conversion failed and expr was an invalid use of pointer to
765 member function, try to report a meaningful error. */
766 if (invalid_nonstatic_memfn_p (expr, tf_warning_or_error))
767 /* We displayed the error message. */;
769 error ("conversion from %qT to non-scalar type %qT requested",
770 TREE_TYPE (expr), type);
772 return error_mark_node;
775 /* When an expression is used in a void context, its value is discarded and
776 no lvalue-rvalue and similar conversions happen [expr.static.cast/4,
777 stmt.expr/1, expr.comma/1]. This permits dereferencing an incomplete type
778 in a void context. The C++ standard does not define what an `access' to an
779 object is, but there is reason to believe that it is the lvalue to rvalue
780 conversion -- if it were not, `*&*p = 1' would violate [expr]/4 in that it
781 accesses `*p' not to calculate the value to be stored. But, dcl.type.cv/8
782 indicates that volatile semantics should be the same between C and C++
783 where ever possible. C leaves it implementation defined as to what
784 constitutes an access to a volatile. So, we interpret `*vp' as a read of
785 the volatile object `vp' points to, unless that is an incomplete type. For
786 volatile references we do not do this interpretation, because that would
787 make it impossible to ignore the reference return value from functions. We
788 issue warnings in the confusing cases.
790 IMPLICIT is tells us the context of an implicit void conversion. */
793 convert_to_void (tree expr, const char *implicit, tsubst_flags_t complain)
795 if (expr == error_mark_node
796 || TREE_TYPE (expr) == error_mark_node)
797 return error_mark_node;
798 if (!TREE_TYPE (expr))
800 if (invalid_nonstatic_memfn_p (expr, complain))
801 return error_mark_node;
802 if (TREE_CODE (expr) == PSEUDO_DTOR_EXPR)
804 if (complain & tf_error)
805 error ("pseudo-destructor is not called");
806 return error_mark_node;
808 if (VOID_TYPE_P (TREE_TYPE (expr)))
810 switch (TREE_CODE (expr))
814 /* The two parts of a cond expr might be separate lvalues. */
815 tree op1 = TREE_OPERAND (expr,1);
816 tree op2 = TREE_OPERAND (expr,2);
817 tree new_op1 = convert_to_void
818 (op1, (implicit && !TREE_SIDE_EFFECTS (op2)
819 ? "second operand of conditional" : NULL), complain);
820 tree new_op2 = convert_to_void
821 (op2, (implicit && !TREE_SIDE_EFFECTS (op1)
822 ? "third operand of conditional" : NULL), complain);
824 expr = build3 (COND_EXPR, TREE_TYPE (new_op1),
825 TREE_OPERAND (expr, 0), new_op1, new_op2);
831 /* The second part of a compound expr contains the value. */
832 tree op1 = TREE_OPERAND (expr,1);
833 tree new_op1 = convert_to_void
834 (op1, (implicit && !TREE_NO_WARNING (expr)
835 ? "right-hand operand of comma" : NULL), complain);
839 tree t = build2 (COMPOUND_EXPR, TREE_TYPE (new_op1),
840 TREE_OPERAND (expr, 0), new_op1);
847 case NON_LVALUE_EXPR:
849 /* These have already decayed to rvalue. */
852 case CALL_EXPR: /* We have a special meaning for volatile void fn(). */
857 tree type = TREE_TYPE (expr);
858 int is_reference = TREE_CODE (TREE_TYPE (TREE_OPERAND (expr, 0)))
860 int is_volatile = TYPE_VOLATILE (type);
861 int is_complete = COMPLETE_TYPE_P (complete_type (type));
863 /* Can't load the value if we don't know the type. */
864 if (is_volatile && !is_complete)
866 if (complain & tf_warning)
867 warning (0, "object of incomplete type %qT will not be accessed in %s",
868 type, implicit ? implicit : "void context");
870 /* Don't load the value if this is an implicit dereference, or if
871 the type needs to be handled by ctors/dtors. */
872 else if (is_volatile && (is_reference || TREE_ADDRESSABLE (type)))
874 if (complain & tf_warning)
875 warning (0, "object of type %qT will not be accessed in %s",
876 TREE_TYPE (TREE_OPERAND (expr, 0)),
877 implicit ? implicit : "void context");
879 if (is_reference || !is_volatile || !is_complete || TREE_ADDRESSABLE (type))
880 expr = TREE_OPERAND (expr, 0);
887 /* External variables might be incomplete. */
888 tree type = TREE_TYPE (expr);
889 int is_complete = COMPLETE_TYPE_P (complete_type (type));
891 if (TYPE_VOLATILE (type) && !is_complete && (complain & tf_warning))
892 warning (0, "object %qE of incomplete type %qT will not be accessed in %s",
893 expr, type, implicit ? implicit : "void context");
898 /* Don't bother with the temporary object returned from a function if
899 we don't use it and don't need to destroy it. We'll still
900 allocate space for it in expand_call or declare_return_variable,
901 but we don't need to track it through all the tree phases. */
902 if (TARGET_EXPR_IMPLICIT_P (expr)
903 && TYPE_HAS_TRIVIAL_DESTRUCTOR (TREE_TYPE (expr)))
905 tree init = TARGET_EXPR_INITIAL (expr);
906 if (TREE_CODE (init) == AGGR_INIT_EXPR
907 && !AGGR_INIT_VIA_CTOR_P (init))
909 tree fn = AGGR_INIT_EXPR_FN (init);
910 expr = build_call_array (TREE_TYPE (TREE_TYPE (TREE_TYPE (fn))),
912 aggr_init_expr_nargs (init),
913 AGGR_INIT_EXPR_ARGP (init));
923 if (TREE_CODE (probe) == ADDR_EXPR)
924 probe = TREE_OPERAND (expr, 0);
925 if (type_unknown_p (probe))
927 /* [over.over] enumerates the places where we can take the address
928 of an overloaded function, and this is not one of them. */
929 if (complain & tf_error)
930 error ("%s cannot resolve address of overloaded function",
931 implicit ? implicit : "void cast");
933 return error_mark_node;
934 expr = void_zero_node;
936 else if (implicit && probe == expr && is_overloaded_fn (probe))
938 /* Only warn when there is no &. */
939 if (complain & tf_warning)
940 warning (OPT_Waddress, "%s is a reference, not call, to function %qE",
942 if (TREE_CODE (expr) == COMPONENT_REF)
943 expr = TREE_OPERAND (expr, 0);
947 if (expr != error_mark_node && !VOID_TYPE_P (TREE_TYPE (expr)))
951 && !TREE_NO_WARNING (expr)
952 && !processing_template_decl)
954 /* The middle end does not warn about expressions that have
955 been explicitly cast to void, so we must do so here. */
956 if (!TREE_SIDE_EFFECTS (expr)) {
957 if (complain & tf_warning)
958 warning (OPT_Wunused_value, "%s has no effect", implicit);
964 enum tree_code_class tclass;
967 /* We might like to warn about (say) "(int) f()", as the
968 cast has no effect, but the compiler itself will
969 generate implicit conversions under some
970 circumstances. (For example a block copy will be
971 turned into a call to "__builtin_memcpy", with a
972 conversion of the return value to an appropriate
973 type.) So, to avoid false positives, we strip
974 conversions. Do not use STRIP_NOPs because it will
975 not strip conversions to "void", as that is not a
976 mode-preserving conversion. */
977 while (TREE_CODE (e) == NOP_EXPR)
978 e = TREE_OPERAND (e, 0);
980 code = TREE_CODE (e);
981 tclass = TREE_CODE_CLASS (code);
982 if ((tclass == tcc_comparison
983 || tclass == tcc_unary
984 || (tclass == tcc_binary
985 && !(code == MODIFY_EXPR
987 || code == PREDECREMENT_EXPR
988 || code == PREINCREMENT_EXPR
989 || code == POSTDECREMENT_EXPR
990 || code == POSTINCREMENT_EXPR)))
991 && (complain & tf_warning))
992 warning (OPT_Wunused_value, "value computed is not used");
995 expr = build1 (CONVERT_EXPR, void_type_node, expr);
997 if (! TREE_SIDE_EFFECTS (expr))
998 expr = void_zero_node;
1002 /* Create an expression whose value is that of EXPR,
1003 converted to type TYPE. The TREE_TYPE of the value
1004 is always TYPE. This function implements all reasonable
1005 conversions; callers should filter out those that are
1006 not permitted by the language being compiled.
1008 Most of this routine is from build_reinterpret_cast.
1010 The back end cannot call cp_convert (what was convert) because
1011 conversions to/from basetypes may involve memory references
1012 (vbases) and adding or subtracting small values (multiple
1013 inheritance), but it calls convert from the constant folding code
1014 on subtrees of already built trees after it has ripped them apart.
1016 Also, if we ever support range variables, we'll probably also have to
1017 do a little bit more work. */
1020 convert (tree type, tree expr)
1024 if (type == error_mark_node || expr == error_mark_node)
1025 return error_mark_node;
1027 intype = TREE_TYPE (expr);
1029 if (POINTER_TYPE_P (type) && POINTER_TYPE_P (intype))
1030 return fold_if_not_in_template (build_nop (type, expr));
1032 return ocp_convert (type, expr, CONV_OLD_CONVERT,
1033 LOOKUP_NORMAL|LOOKUP_NO_CONVERSION);
1036 /* Like cp_convert, except permit conversions to take place which
1037 are not normally allowed due to access restrictions
1038 (such as conversion from sub-type to private super-type). */
1041 convert_force (tree type, tree expr, int convtype)
1044 enum tree_code code = TREE_CODE (type);
1046 if (code == REFERENCE_TYPE)
1047 return (fold_if_not_in_template
1048 (convert_to_reference (type, e, CONV_C_CAST, LOOKUP_COMPLAIN,
1051 if (code == POINTER_TYPE)
1052 return fold_if_not_in_template (convert_to_pointer_force (type, e));
1054 /* From typeck.c convert_for_assignment */
1055 if (((TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE && TREE_CODE (e) == ADDR_EXPR
1056 && TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE
1057 && TREE_CODE (TREE_TYPE (TREE_TYPE (e))) == METHOD_TYPE)
1058 || integer_zerop (e)
1059 || TYPE_PTRMEMFUNC_P (TREE_TYPE (e)))
1060 && TYPE_PTRMEMFUNC_P (type))
1061 /* compatible pointer to member functions. */
1062 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), e, 1,
1065 return ocp_convert (type, e, CONV_C_CAST|convtype, LOOKUP_NORMAL);
1068 /* Convert an aggregate EXPR to type XTYPE. If a conversion
1069 exists, return the attempted conversion. This may
1070 return ERROR_MARK_NODE if the conversion is not
1071 allowed (references private members, etc).
1072 If no conversion exists, NULL_TREE is returned.
1074 FIXME: Ambiguity checking is wrong. Should choose one by the implicit
1075 object parameter, or by the second standard conversion sequence if
1076 that doesn't do it. This will probably wait for an overloading rewrite.
1080 build_type_conversion (tree xtype, tree expr)
1082 /* C++: check to see if we can convert this aggregate type
1083 into the required type. */
1084 return build_user_type_conversion (xtype, expr, LOOKUP_NORMAL);
1087 /* Convert the given EXPR to one of a group of types suitable for use in an
1088 expression. DESIRES is a combination of various WANT_* flags (q.v.)
1089 which indicates which types are suitable. If COMPLAIN is true, complain
1090 about ambiguity; otherwise, the caller will deal with it. */
1093 build_expr_type_conversion (int desires, tree expr, bool complain)
1095 tree basetype = TREE_TYPE (expr);
1096 tree conv = NULL_TREE;
1097 tree winner = NULL_TREE;
1099 if (expr == null_node
1100 && (desires & WANT_INT)
1101 && !(desires & WANT_NULL))
1102 warning (OPT_Wconversion, "converting NULL to non-pointer type");
1104 basetype = TREE_TYPE (expr);
1106 if (basetype == error_mark_node)
1107 return error_mark_node;
1109 if (! MAYBE_CLASS_TYPE_P (basetype))
1110 switch (TREE_CODE (basetype))
1113 if ((desires & WANT_NULL) && null_ptr_cst_p (expr))
1115 /* else fall through... */
1118 return (desires & WANT_INT) ? expr : NULL_TREE;
1120 return (desires & WANT_ENUM) ? expr : NULL_TREE;
1122 return (desires & WANT_FLOAT) ? expr : NULL_TREE;
1124 return (desires & WANT_POINTER) ? expr : NULL_TREE;
1128 return (desires & WANT_POINTER) ? decay_conversion (expr)
1132 if ((desires & WANT_VECTOR) == 0)
1134 switch (TREE_CODE (TREE_TYPE (basetype)))
1138 return (desires & WANT_INT) ? expr : NULL_TREE;
1140 return (desires & WANT_ENUM) ? expr : NULL_TREE;
1142 return (desires & WANT_FLOAT) ? expr : NULL_TREE;
1151 /* The code for conversions from class type is currently only used for
1152 delete expressions. Other expressions are handled by build_new_op. */
1153 if (!complete_type_or_else (basetype, expr))
1154 return error_mark_node;
1155 if (!TYPE_HAS_CONVERSION (basetype))
1158 for (conv = lookup_conversions (basetype); conv; conv = TREE_CHAIN (conv))
1162 tree cand = TREE_VALUE (conv);
1164 if (winner && winner == cand)
1167 candidate = non_reference (TREE_TYPE (TREE_TYPE (cand)));
1169 switch (TREE_CODE (candidate))
1173 win = (desires & WANT_INT); break;
1175 win = (desires & WANT_ENUM); break;
1177 win = (desires & WANT_FLOAT); break;
1179 win = (desires & WANT_POINTER); break;
1182 if ((desires & WANT_VECTOR) == 0)
1184 switch (TREE_CODE (TREE_TYPE (candidate)))
1188 win = (desires & WANT_INT); break;
1190 win = (desires & WANT_ENUM); break;
1192 win = (desires & WANT_FLOAT); break;
1208 error ("ambiguous default type conversion from %qT",
1210 error (" candidate conversions include %qD and %qD",
1213 return error_mark_node;
1222 tree type = non_reference (TREE_TYPE (TREE_TYPE (winner)));
1223 return build_user_type_conversion (type, expr, LOOKUP_NORMAL);
1229 /* Implements integral promotion (4.1) and float->double promotion. */
1232 type_promotes_to (tree type)
1234 if (type == error_mark_node)
1235 return error_mark_node;
1237 type = TYPE_MAIN_VARIANT (type);
1239 /* bool always promotes to int (not unsigned), even if it's the same
1241 if (type == boolean_type_node)
1242 type = integer_type_node;
1244 /* Normally convert enums to int, but convert wide enums to something
1246 else if (TREE_CODE (type) == ENUMERAL_TYPE
1247 || type == char16_type_node
1248 || type == char32_type_node
1249 || type == wchar_type_node)
1251 int precision = MAX (TYPE_PRECISION (type),
1252 TYPE_PRECISION (integer_type_node));
1253 tree totype = c_common_type_for_size (precision, 0);
1254 if (TYPE_UNSIGNED (type)
1255 && ! int_fits_type_p (TYPE_MAX_VALUE (type), totype))
1256 type = c_common_type_for_size (precision, 1);
1260 else if (c_promoting_integer_type_p (type))
1262 /* Retain unsignedness if really not getting bigger. */
1263 if (TYPE_UNSIGNED (type)
1264 && TYPE_PRECISION (type) == TYPE_PRECISION (integer_type_node))
1265 type = unsigned_type_node;
1267 type = integer_type_node;
1269 else if (type == float_type_node)
1270 type = double_type_node;
1275 /* The routines below this point are carefully written to conform to
1276 the standard. They use the same terminology, and follow the rules
1277 closely. Although they are used only in pt.c at the moment, they
1278 should presumably be used everywhere in the future. */
1280 /* Attempt to perform qualification conversions on EXPR to convert it
1281 to TYPE. Return the resulting expression, or error_mark_node if
1282 the conversion was impossible. */
1285 perform_qualification_conversions (tree type, tree expr)
1289 expr_type = TREE_TYPE (expr);
1291 if (same_type_p (type, expr_type))
1293 else if (TYPE_PTR_P (type) && TYPE_PTR_P (expr_type)
1294 && comp_ptr_ttypes (TREE_TYPE (type), TREE_TYPE (expr_type)))
1295 return build_nop (type, expr);
1296 else if (TYPE_PTR_TO_MEMBER_P (type)
1297 && TYPE_PTR_TO_MEMBER_P (expr_type)
1298 && same_type_p (TYPE_PTRMEM_CLASS_TYPE (type),
1299 TYPE_PTRMEM_CLASS_TYPE (expr_type))
1300 && comp_ptr_ttypes (TYPE_PTRMEM_POINTED_TO_TYPE (type),
1301 TYPE_PTRMEM_POINTED_TO_TYPE (expr_type)))
1302 return build_nop (type, expr);
1304 return error_mark_node;