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 Free Software Foundation, Inc.
4 Hacked by Michael Tiemann (tiemann@cygnus.com)
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 2, or (at your option)
13 GCC is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING. If not, write to
20 the Free Software Foundation, 59 Temple Place - Suite 330,
21 Boston, MA 02111-1307, USA. */
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"
40 static tree cp_convert_to_pointer (tree, tree, bool);
41 static tree convert_to_pointer_force (tree, tree);
42 static tree build_up_reference (tree, tree, int, tree);
43 static void warn_ref_binding (tree, tree, tree);
45 /* Change of width--truncation and extension of integers or reals--
46 is represented with NOP_EXPR. Proper functioning of many things
47 assumes that no other conversions can be NOP_EXPRs.
49 Conversion between integer and pointer is represented with CONVERT_EXPR.
50 Converting integer to real uses FLOAT_EXPR
51 and real to integer uses FIX_TRUNC_EXPR.
53 Here is a list of all the functions that assume that widening and
54 narrowing is always done with a NOP_EXPR:
55 In convert.c, convert_to_integer.
56 In c-typeck.c, build_binary_op_nodefault (boolean ops),
57 and c_common_truthvalue_conversion.
58 In expr.c: expand_expr, for operands of a MULT_EXPR.
59 In fold-const.c: fold.
60 In tree.c: get_narrower and get_unwidened.
62 C++: in multiple-inheritance, converting between pointers may involve
63 adjusting them by a delta stored within the class definition. */
65 /* Subroutines of `convert'. */
67 /* if converting pointer to pointer
68 if dealing with classes, check for derived->base or vice versa
69 else if dealing with method pointers, delegate
71 else if converting class, pass off to build_type_conversion
72 else try C-style pointer conversion. If FORCE is true then allow
73 conversions via virtual bases (these are permitted by reinterpret_cast,
74 but not static_cast). */
77 cp_convert_to_pointer (tree type, tree expr, bool force)
79 tree intype = TREE_TYPE (expr);
82 if (intype == error_mark_node)
83 return error_mark_node;
85 if (IS_AGGR_TYPE (intype))
87 intype = complete_type (intype);
88 if (!COMPLETE_TYPE_P (intype))
90 error ("can't convert from incomplete type `%T' to `%T'",
92 return error_mark_node;
95 rval = build_type_conversion (type, expr);
98 if (rval == error_mark_node)
99 error ("conversion of `%E' from `%T' to `%T' 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 && IS_AGGR_TYPE (TREE_TYPE (type))
131 && IS_AGGR_TYPE (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 `%E' from type `%T' to type `%T'",
170 return error_mark_node;
173 return build_nop (type, expr);
175 else if (TYPE_PTRMEM_P (type) && TYPE_PTRMEM_P (intype))
180 enum tree_code code = PLUS_EXPR;
183 b1 = TYPE_PTRMEM_CLASS_TYPE (type);
184 b2 = TYPE_PTRMEM_CLASS_TYPE (intype);
185 binfo = lookup_base (b1, b2, ba_check, &bk);
188 binfo = lookup_base (b2, b1, ba_check, &bk);
191 if (binfo == error_mark_node)
192 return error_mark_node;
194 if (bk == bk_via_virtual)
197 warning ("pointer to member cast from `%T' to `%T' is via virtual base",
201 error ("pointer to member cast from `%T' to `%T' is via virtual base",
203 return error_mark_node;
205 /* This is a reinterpret cast, whose result is unspecified.
206 We choose to do nothing. */
207 return build1 (NOP_EXPR, type, expr);
210 if (TREE_CODE (expr) == PTRMEM_CST)
211 expr = cplus_expand_constant (expr);
213 if (binfo && !integer_zerop (BINFO_OFFSET (binfo)))
214 expr = size_binop (code,
215 build_nop (sizetype, expr),
216 BINFO_OFFSET (binfo));
217 return build_nop (type, expr);
219 else if (TYPE_PTRMEMFUNC_P (type) && TYPE_PTRMEMFUNC_P (intype))
220 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), expr, 0,
222 else if (TYPE_PTRMEMFUNC_P (intype))
226 if (TREE_CODE (expr) == PTRMEM_CST)
227 return cp_convert_to_pointer (type,
228 PTRMEM_CST_MEMBER (expr),
230 else if (TREE_CODE (expr) == OFFSET_REF)
232 tree object = TREE_OPERAND (expr, 0);
233 return get_member_function_from_ptrfunc (&object,
234 TREE_OPERAND (expr, 1));
237 error ("cannot convert `%E' from type `%T' to type `%T'",
239 return error_mark_node;
242 if (integer_zerop (expr))
244 if (TYPE_PTRMEMFUNC_P (type))
245 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), expr, 0,
248 if (TYPE_PTRMEM_P (type))
250 /* A NULL pointer-to-member is represented by -1, not by
252 expr = build_int_cst (type, -1);
253 /* Fix up the representation of -1 if appropriate. */
254 expr = force_fit_type (expr, 0, false, false);
257 expr = build_int_cst (type, 0);
261 else if (TYPE_PTR_TO_MEMBER_P (type) && INTEGRAL_CODE_P (form))
263 error ("invalid conversion from '%T' to '%T'", intype, type);
264 return error_mark_node;
267 if (INTEGRAL_CODE_P (form))
269 if (TYPE_PRECISION (intype) == POINTER_SIZE)
270 return build1 (CONVERT_EXPR, type, expr);
271 expr = cp_convert (c_common_type_for_size (POINTER_SIZE, 0), expr);
272 /* Modes may be different but sizes should be the same. There
273 is supposed to be some integral type that is the same width
275 gcc_assert (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (expr)))
276 == GET_MODE_SIZE (TYPE_MODE (type)));
278 return convert_to_pointer (type, expr);
281 if (type_unknown_p (expr))
282 return instantiate_type (type, expr, tf_error | tf_warning);
284 error ("cannot convert `%E' from type `%T' to type `%T'",
286 return error_mark_node;
289 /* Like convert, except permit conversions to take place which
290 are not normally allowed due to access restrictions
291 (such as conversion from sub-type to private super-type). */
294 convert_to_pointer_force (tree type, tree expr)
296 tree intype = TREE_TYPE (expr);
297 enum tree_code form = TREE_CODE (intype);
299 if (form == POINTER_TYPE)
301 intype = TYPE_MAIN_VARIANT (intype);
303 if (TYPE_MAIN_VARIANT (type) != intype
304 && TREE_CODE (TREE_TYPE (type)) == RECORD_TYPE
305 && IS_AGGR_TYPE (TREE_TYPE (type))
306 && IS_AGGR_TYPE (TREE_TYPE (intype))
307 && TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE)
309 enum tree_code code = PLUS_EXPR;
312 binfo = lookup_base (TREE_TYPE (intype), TREE_TYPE (type),
316 binfo = lookup_base (TREE_TYPE (type), TREE_TYPE (intype),
320 if (binfo == error_mark_node)
321 return error_mark_node;
324 expr = build_base_path (code, expr, binfo, 0);
325 if (expr == error_mark_node)
326 return error_mark_node;
327 /* Add any qualifier conversions. */
328 if (!same_type_p (TREE_TYPE (TREE_TYPE (expr)),
330 expr = build_nop (type, expr);
336 return cp_convert_to_pointer (type, expr, true);
339 /* We are passing something to a function which requires a reference.
340 The type we are interested in is in TYPE. The initial
341 value we have to begin with is in ARG.
343 FLAGS controls how we manage access checking.
344 DIRECT_BIND in FLAGS controls how any temporaries are generated.
345 If DIRECT_BIND is set, DECL is the reference we're binding to. */
348 build_up_reference (tree type, tree arg, int flags, tree decl)
351 tree argtype = TREE_TYPE (arg);
352 tree target_type = TREE_TYPE (type);
354 gcc_assert (TREE_CODE (type) == REFERENCE_TYPE);
356 if ((flags & DIRECT_BIND) && ! real_lvalue_p (arg))
358 /* Create a new temporary variable. We can't just use a TARGET_EXPR
359 here because it needs to live as long as DECL. */
362 arg = make_temporary_var_for_ref_to_temp (decl, TREE_TYPE (arg));
364 /* Process the initializer for the declaration. */
365 DECL_INITIAL (arg) = targ;
366 cp_finish_decl (arg, targ, NULL_TREE,
367 LOOKUP_ONLYCONVERTING|DIRECT_BIND);
369 else if (!(flags & DIRECT_BIND) && ! lvalue_p (arg))
370 return get_target_expr (arg);
372 /* If we had a way to wrap this up, and say, if we ever needed its
373 address, transform all occurrences of the register, into a memory
374 reference we could win better. */
375 rval = build_unary_op (ADDR_EXPR, arg, 1);
376 if (rval == error_mark_node)
377 return error_mark_node;
379 if ((flags & LOOKUP_PROTECT)
380 && TYPE_MAIN_VARIANT (argtype) != TYPE_MAIN_VARIANT (target_type)
381 && IS_AGGR_TYPE (argtype)
382 && IS_AGGR_TYPE (target_type))
384 /* We go through lookup_base for the access control. */
385 tree binfo = lookup_base (argtype, target_type, ba_check, NULL);
386 if (binfo == error_mark_node)
387 return error_mark_node;
388 if (binfo == NULL_TREE)
389 return error_not_base_type (target_type, argtype);
390 rval = build_base_path (PLUS_EXPR, rval, binfo, 1);
394 = convert_to_pointer_force (build_pointer_type (target_type), rval);
395 return build_nop (type, rval);
398 /* Subroutine of convert_to_reference. REFTYPE is the target reference type.
399 INTYPE is the original rvalue type and DECL is an optional _DECL node
402 [dcl.init.ref] says that if an rvalue is used to
403 initialize a reference, then the reference must be to a
404 non-volatile const type. */
407 warn_ref_binding (tree reftype, tree intype, tree decl)
409 tree ttl = TREE_TYPE (reftype);
411 if (!CP_TYPE_CONST_NON_VOLATILE_P (ttl))
415 if (CP_TYPE_VOLATILE_P (ttl) && decl)
416 msg = "initialization of volatile reference type `%#T' from rvalue of type `%T'";
417 else if (CP_TYPE_VOLATILE_P (ttl))
418 msg = "conversion to volatile reference type `%#T' from rvalue of type `%T'";
420 msg = "initialization of non-const reference type `%#T' from rvalue of type `%T'";
422 msg = "conversion to non-const reference type `%#T' from rvalue of type `%T'";
424 pedwarn (msg, reftype, intype);
428 /* For C++: Only need to do one-level references, but cannot
429 get tripped up on signed/unsigned differences.
431 DECL is either NULL_TREE or the _DECL node for a reference that is being
432 initialized. It can be error_mark_node if we don't know the _DECL but
433 we know it's an initialization. */
436 convert_to_reference (tree reftype, tree expr, int convtype,
437 int flags, tree decl)
439 tree type = TYPE_MAIN_VARIANT (TREE_TYPE (reftype));
441 tree rval = NULL_TREE;
442 tree rval_as_conversion = NULL_TREE;
443 bool can_convert_intype_to_type;
445 if (TREE_CODE (type) == FUNCTION_TYPE
446 && TREE_TYPE (expr) == unknown_type_node)
447 expr = instantiate_type (type, expr,
448 (flags & LOOKUP_COMPLAIN)
449 ? tf_error | tf_warning : tf_none);
451 expr = convert_from_reference (expr);
453 if (expr == error_mark_node)
454 return error_mark_node;
456 intype = TREE_TYPE (expr);
458 gcc_assert (TREE_CODE (intype) != REFERENCE_TYPE);
460 intype = TYPE_MAIN_VARIANT (intype);
462 can_convert_intype_to_type = can_convert (type, intype);
463 if (!can_convert_intype_to_type
464 && (convtype & CONV_IMPLICIT) && IS_AGGR_TYPE (intype)
465 && ! (flags & LOOKUP_NO_CONVERSION))
467 /* Look for a user-defined conversion to lvalue that we can use. */
470 = build_type_conversion (reftype, expr);
472 if (rval_as_conversion && rval_as_conversion != error_mark_node
473 && real_lvalue_p (rval_as_conversion))
475 expr = rval_as_conversion;
476 rval_as_conversion = NULL_TREE;
478 can_convert_intype_to_type = 1;
482 if (((convtype & CONV_STATIC) && can_convert (intype, type))
483 || ((convtype & CONV_IMPLICIT) && can_convert_intype_to_type))
485 if (flags & LOOKUP_COMPLAIN)
487 tree ttl = TREE_TYPE (reftype);
488 tree ttr = lvalue_type (expr);
490 if (! real_lvalue_p (expr))
491 warn_ref_binding (reftype, intype, decl);
493 if (! (convtype & CONV_CONST)
494 && !at_least_as_qualified_p (ttl, ttr))
495 pedwarn ("conversion from `%T' to `%T' discards qualifiers",
499 return build_up_reference (reftype, expr, flags, decl);
501 else if ((convtype & CONV_REINTERPRET) && lvalue_p (expr))
503 /* When casting an lvalue to a reference type, just convert into
504 a pointer to the new type and deference it. This is allowed
505 by San Diego WP section 5.2.9 paragraph 12, though perhaps it
506 should be done directly (jason). (int &)ri ---> *(int*)&ri */
508 /* B* bp; A& ar = (A&)bp; is valid, but it's probably not what they
510 if (TREE_CODE (intype) == POINTER_TYPE
511 && (comptypes (TREE_TYPE (intype), type,
512 COMPARE_BASE | COMPARE_DERIVED)))
513 warning ("casting `%T' to `%T' does not dereference pointer",
516 rval = build_unary_op (ADDR_EXPR, expr, 0);
517 if (rval != error_mark_node)
518 rval = convert_force (build_pointer_type (TREE_TYPE (reftype)),
520 if (rval != error_mark_node)
521 rval = build1 (NOP_EXPR, reftype, rval);
525 rval = convert_for_initialization (NULL_TREE, type, expr, flags,
527 if (rval == NULL_TREE || rval == error_mark_node)
529 warn_ref_binding (reftype, intype, decl);
530 rval = build_up_reference (reftype, rval, flags, decl);
535 /* If we found a way to convert earlier, then use it. */
539 if (flags & LOOKUP_COMPLAIN)
540 error ("cannot convert type `%T' to type `%T'", intype, reftype);
542 return error_mark_node;
545 /* We are using a reference VAL for its value. Bash that reference all the
546 way down to its lowest form. */
549 convert_from_reference (tree val)
551 if (TREE_CODE (TREE_TYPE (val)) == REFERENCE_TYPE)
552 return build_indirect_ref (val, NULL);
556 /* Implicitly convert the lvalue EXPR to another lvalue of type TOTYPE,
557 preserving cv-qualification. */
560 convert_lvalue (tree totype, tree expr)
562 totype = cp_build_qualified_type (totype, TYPE_QUALS (TREE_TYPE (expr)));
563 totype = build_reference_type (totype);
564 expr = convert_to_reference (totype, expr, CONV_IMPLICIT, LOOKUP_NORMAL,
566 return convert_from_reference (expr);
569 /* Really perform an lvalue-to-rvalue conversion, including copying an
570 argument of class type into a temporary. */
573 force_rvalue (tree expr)
575 if (IS_AGGR_TYPE (TREE_TYPE (expr)) && TREE_CODE (expr) != TARGET_EXPR)
576 expr = ocp_convert (TREE_TYPE (expr), expr,
577 CONV_IMPLICIT|CONV_FORCE_TEMP, LOOKUP_NORMAL);
579 expr = decay_conversion (expr);
584 /* C++ conversions, preference to static cast conversions. */
587 cp_convert (tree type, tree expr)
589 return ocp_convert (type, expr, CONV_OLD_CONVERT, LOOKUP_NORMAL);
594 FLAGS indicates how we should behave. */
597 ocp_convert (tree type, tree expr, int convtype, int flags)
600 enum tree_code code = TREE_CODE (type);
602 if (error_operand_p (e) || type == error_mark_node)
603 return error_mark_node;
605 complete_type (type);
606 complete_type (TREE_TYPE (expr));
608 e = decl_constant_value (e);
610 if (IS_AGGR_TYPE (type) && (convtype & CONV_FORCE_TEMP)
611 /* Some internal structures (vtable_entry_type, sigtbl_ptr_type)
612 don't go through finish_struct, so they don't have the synthesized
613 constructors. So don't force a temporary. */
614 && TYPE_HAS_CONSTRUCTOR (type))
615 /* We need a new temporary; don't take this shortcut. */;
616 else if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (e)))
618 if (same_type_p (type, TREE_TYPE (e)))
619 /* The call to fold will not always remove the NOP_EXPR as
620 might be expected, since if one of the types is a typedef;
621 the comparison in fold is just equality of pointers, not a
622 call to comptypes. We don't call fold in this case because
623 that can result in infinite recursion; fold will call
624 convert, which will call ocp_convert, etc. */
626 /* For complex data types, we need to perform componentwise
628 else if (TREE_CODE (type) == COMPLEX_TYPE)
629 return fold_if_not_in_template (convert_to_complex (type, e));
630 else if (TREE_CODE (e) == TARGET_EXPR)
632 /* Don't build a NOP_EXPR of class type. Instead, change the
633 type of the temporary. Only allow this for cv-qual changes,
635 gcc_assert (same_type_p (TYPE_MAIN_VARIANT (TREE_TYPE (e)),
636 TYPE_MAIN_VARIANT (type)));
637 TREE_TYPE (e) = TREE_TYPE (TARGET_EXPR_SLOT (e)) = type;
642 /* We shouldn't be treating objects of ADDRESSABLE type as
644 gcc_assert (!TREE_ADDRESSABLE (type));
645 return fold_if_not_in_template (build_nop (type, e));
649 if (code == VOID_TYPE && (convtype & CONV_STATIC))
651 e = convert_to_void (e, /*implicit=*/NULL);
655 if (INTEGRAL_CODE_P (code))
657 tree intype = TREE_TYPE (e);
658 /* enum = enum, enum = int, enum = float, (enum)pointer are all
660 if (TREE_CODE (type) == ENUMERAL_TYPE
661 && ((ARITHMETIC_TYPE_P (intype) && ! (convtype & CONV_STATIC))
662 || (TREE_CODE (intype) == POINTER_TYPE)))
664 pedwarn ("conversion from `%#T' to `%#T'", intype, type);
666 if (flag_pedantic_errors)
667 return error_mark_node;
669 if (IS_AGGR_TYPE (intype))
672 rval = build_type_conversion (type, e);
675 if (flags & LOOKUP_COMPLAIN)
676 error ("`%#T' used where a `%T' was expected", intype, type);
677 return error_mark_node;
679 if (code == BOOLEAN_TYPE)
680 return cp_truthvalue_conversion (e);
682 return fold_if_not_in_template (convert_to_integer (type, e));
684 if (POINTER_TYPE_P (type) || TYPE_PTR_TO_MEMBER_P (type))
685 return fold_if_not_in_template (cp_convert_to_pointer (type, e, false));
686 if (code == VECTOR_TYPE)
688 tree in_vtype = TREE_TYPE (e);
689 if (IS_AGGR_TYPE (in_vtype))
692 ret_val = build_type_conversion (type, e);
695 if (flags & LOOKUP_COMPLAIN)
696 error ("`%#T' used where a `%T' was expected", in_vtype, type);
697 return error_mark_node;
699 return fold_if_not_in_template (convert_to_vector (type, e));
701 if (code == REAL_TYPE || code == COMPLEX_TYPE)
703 if (IS_AGGR_TYPE (TREE_TYPE (e)))
706 rval = build_type_conversion (type, e);
710 if (flags & LOOKUP_COMPLAIN)
711 error ("`%#T' used where a floating point value was expected",
714 if (code == REAL_TYPE)
715 return fold_if_not_in_template (convert_to_real (type, e));
716 else if (code == COMPLEX_TYPE)
717 return fold_if_not_in_template (convert_to_complex (type, e));
720 /* New C++ semantics: since assignment is now based on
721 memberwise copying, if the rhs type is derived from the
722 lhs type, then we may still do a conversion. */
723 if (IS_AGGR_TYPE_CODE (code))
725 tree dtype = TREE_TYPE (e);
726 tree ctor = NULL_TREE;
728 dtype = TYPE_MAIN_VARIANT (dtype);
730 /* Conversion between aggregate types. New C++ semantics allow
731 objects of derived type to be cast to objects of base type.
732 Old semantics only allowed this between pointers.
734 There may be some ambiguity between using a constructor
735 vs. using a type conversion operator when both apply. */
739 if (abstract_virtuals_error (NULL_TREE, type))
740 return error_mark_node;
742 if ((flags & LOOKUP_ONLYCONVERTING)
743 && ! (IS_AGGR_TYPE (dtype) && DERIVED_FROM_P (type, dtype)))
744 /* For copy-initialization, first we create a temp of the proper type
745 with a user-defined conversion sequence, then we direct-initialize
746 the target with the temp (see [dcl.init]). */
747 ctor = build_user_type_conversion (type, ctor, flags);
749 ctor = build_special_member_call (NULL_TREE,
750 complete_ctor_identifier,
751 build_tree_list (NULL_TREE, ctor),
754 return build_cplus_new (type, ctor);
757 if (flags & LOOKUP_COMPLAIN)
758 error ("conversion from `%T' to non-scalar type `%T' requested",
759 TREE_TYPE (expr), type);
760 return error_mark_node;
763 /* When an expression is used in a void context, its value is discarded and
764 no lvalue-rvalue and similar conversions happen [expr.static.cast/4,
765 stmt.expr/1, expr.comma/1]. This permits dereferencing an incomplete type
766 in a void context. The C++ standard does not define what an `access' to an
767 object is, but there is reason to believe that it is the lvalue to rvalue
768 conversion -- if it were not, `*&*p = 1' would violate [expr]/4 in that it
769 accesses `*p' not to calculate the value to be stored. But, dcl.type.cv/8
770 indicates that volatile semantics should be the same between C and C++
771 where ever possible. C leaves it implementation defined as to what
772 constitutes an access to a volatile. So, we interpret `*vp' as a read of
773 the volatile object `vp' points to, unless that is an incomplete type. For
774 volatile references we do not do this interpretation, because that would
775 make it impossible to ignore the reference return value from functions. We
776 issue warnings in the confusing cases.
778 IMPLICIT is tells us the context of an implicit void conversion. */
781 convert_to_void (tree expr, const char *implicit)
783 if (expr == error_mark_node
784 || TREE_TYPE (expr) == error_mark_node)
785 return error_mark_node;
786 if (!TREE_TYPE (expr))
788 if (invalid_nonstatic_memfn_p (expr))
789 return error_mark_node;
790 if (VOID_TYPE_P (TREE_TYPE (expr)))
792 switch (TREE_CODE (expr))
796 /* The two parts of a cond expr might be separate lvalues. */
797 tree op1 = TREE_OPERAND (expr,1);
798 tree op2 = TREE_OPERAND (expr,2);
799 tree new_op1 = convert_to_void
800 (op1, (implicit && !TREE_SIDE_EFFECTS (op2)
801 ? "second operand of conditional" : NULL));
802 tree new_op2 = convert_to_void
803 (op2, (implicit && !TREE_SIDE_EFFECTS (op1)
804 ? "third operand of conditional" : NULL));
806 expr = build3 (COND_EXPR, TREE_TYPE (new_op1),
807 TREE_OPERAND (expr, 0), new_op1, new_op2);
813 /* The second part of a compound expr contains the value. */
814 tree op1 = TREE_OPERAND (expr,1);
815 tree new_op1 = convert_to_void
816 (op1, (implicit && !TREE_NO_WARNING (expr)
817 ? "right-hand operand of comma" : NULL));
821 tree t = build2 (COMPOUND_EXPR, TREE_TYPE (new_op1),
822 TREE_OPERAND (expr, 0), new_op1);
829 case NON_LVALUE_EXPR:
831 /* These have already decayed to rvalue. */
834 case CALL_EXPR: /* We have a special meaning for volatile void fn(). */
839 tree type = TREE_TYPE (expr);
840 int is_reference = TREE_CODE (TREE_TYPE (TREE_OPERAND (expr, 0)))
842 int is_volatile = TYPE_VOLATILE (type);
843 int is_complete = COMPLETE_TYPE_P (complete_type (type));
845 if (is_volatile && !is_complete)
846 warning ("object of incomplete type `%T' will not be accessed in %s",
847 type, implicit ? implicit : "void context");
848 else if (is_reference && is_volatile)
849 warning ("object of type `%T' will not be accessed in %s",
850 TREE_TYPE (TREE_OPERAND (expr, 0)),
851 implicit ? implicit : "void context");
852 if (is_reference || !is_volatile || !is_complete)
853 expr = TREE_OPERAND (expr, 0);
860 /* External variables might be incomplete. */
861 tree type = TREE_TYPE (expr);
862 int is_complete = COMPLETE_TYPE_P (complete_type (type));
864 if (TYPE_VOLATILE (type) && !is_complete)
865 warning ("object `%E' of incomplete type `%T' will not be accessed in %s",
866 expr, type, implicit ? implicit : "void context");
875 if (TREE_CODE (probe) == ADDR_EXPR)
876 probe = TREE_OPERAND (expr, 0);
877 if (type_unknown_p (probe))
879 /* [over.over] enumerates the places where we can take the address
880 of an overloaded function, and this is not one of them. */
881 pedwarn ("%s cannot resolve address of overloaded function",
882 implicit ? implicit : "void cast");
883 expr = void_zero_node;
885 else if (implicit && probe == expr && is_overloaded_fn (probe))
886 /* Only warn when there is no &. */
887 warning ("%s is a reference, not call, to function `%E'",
891 if (expr != error_mark_node && !VOID_TYPE_P (TREE_TYPE (expr)))
893 if (implicit && warn_unused_value
894 && !TREE_SIDE_EFFECTS (expr) && !TREE_NO_WARNING (expr))
895 warning ("%s has no effect", implicit);
896 expr = build1 (CONVERT_EXPR, void_type_node, expr);
901 /* Create an expression whose value is that of EXPR,
902 converted to type TYPE. The TREE_TYPE of the value
903 is always TYPE. This function implements all reasonable
904 conversions; callers should filter out those that are
905 not permitted by the language being compiled.
907 Most of this routine is from build_reinterpret_cast.
909 The backend cannot call cp_convert (what was convert) because
910 conversions to/from basetypes may involve memory references
911 (vbases) and adding or subtracting small values (multiple
912 inheritance), but it calls convert from the constant folding code
913 on subtrees of already built trees after it has ripped them apart.
915 Also, if we ever support range variables, we'll probably also have to
916 do a little bit more work. */
919 convert (tree type, tree expr)
923 if (type == error_mark_node || expr == error_mark_node)
924 return error_mark_node;
926 intype = TREE_TYPE (expr);
928 if (POINTER_TYPE_P (type) && POINTER_TYPE_P (intype))
930 expr = decl_constant_value (expr);
931 return fold_if_not_in_template (build_nop (type, expr));
934 return ocp_convert (type, expr, CONV_OLD_CONVERT,
935 LOOKUP_NORMAL|LOOKUP_NO_CONVERSION);
938 /* Like cp_convert, except permit conversions to take place which
939 are not normally allowed due to access restrictions
940 (such as conversion from sub-type to private super-type). */
943 convert_force (tree type, tree expr, int convtype)
946 enum tree_code code = TREE_CODE (type);
948 if (code == REFERENCE_TYPE)
949 return (fold_if_not_in_template
950 (convert_to_reference (type, e, CONV_C_CAST, LOOKUP_COMPLAIN,
952 else if (TREE_CODE (TREE_TYPE (e)) == REFERENCE_TYPE)
953 e = convert_from_reference (e);
955 if (code == POINTER_TYPE)
956 return fold_if_not_in_template (convert_to_pointer_force (type, e));
958 /* From typeck.c convert_for_assignment */
959 if (((TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE && TREE_CODE (e) == ADDR_EXPR
960 && TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE
961 && TREE_CODE (TREE_TYPE (TREE_TYPE (e))) == METHOD_TYPE)
963 || TYPE_PTRMEMFUNC_P (TREE_TYPE (e)))
964 && TYPE_PTRMEMFUNC_P (type))
965 /* compatible pointer to member functions. */
966 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), e, 1,
969 return ocp_convert (type, e, CONV_C_CAST|convtype, LOOKUP_NORMAL);
972 /* Convert an aggregate EXPR to type XTYPE. If a conversion
973 exists, return the attempted conversion. This may
974 return ERROR_MARK_NODE if the conversion is not
975 allowed (references private members, etc).
976 If no conversion exists, NULL_TREE is returned.
978 FIXME: Ambiguity checking is wrong. Should choose one by the implicit
979 object parameter, or by the second standard conversion sequence if
980 that doesn't do it. This will probably wait for an overloading rewrite.
984 build_type_conversion (tree xtype, tree expr)
986 /* C++: check to see if we can convert this aggregate type
987 into the required type. */
988 return build_user_type_conversion (xtype, expr, LOOKUP_NORMAL);
991 /* Convert the given EXPR to one of a group of types suitable for use in an
992 expression. DESIRES is a combination of various WANT_* flags (q.v.)
993 which indicates which types are suitable. If COMPLAIN is true, complain
994 about ambiguity; otherwise, the caller will deal with it. */
997 build_expr_type_conversion (int desires, tree expr, bool complain)
999 tree basetype = TREE_TYPE (expr);
1000 tree conv = NULL_TREE;
1001 tree winner = NULL_TREE;
1003 if (expr == null_node
1004 && (desires & WANT_INT)
1005 && !(desires & WANT_NULL))
1006 warning ("converting NULL to non-pointer type");
1008 expr = convert_from_reference (expr);
1009 basetype = TREE_TYPE (expr);
1011 if (basetype == error_mark_node)
1012 return error_mark_node;
1014 if (! IS_AGGR_TYPE (basetype))
1015 switch (TREE_CODE (basetype))
1018 if ((desires & WANT_NULL) && null_ptr_cst_p (expr))
1020 /* else fall through... */
1023 return (desires & WANT_INT) ? expr : NULL_TREE;
1025 return (desires & WANT_ENUM) ? expr : NULL_TREE;
1027 return (desires & WANT_FLOAT) ? expr : NULL_TREE;
1029 return (desires & WANT_POINTER) ? expr : NULL_TREE;
1033 return (desires & WANT_POINTER) ? decay_conversion (expr)
1039 /* The code for conversions from class type is currently only used for
1040 delete expressions. Other expressions are handled by build_new_op. */
1041 if (!complete_type_or_else (basetype, expr))
1042 return error_mark_node;
1043 if (!TYPE_HAS_CONVERSION (basetype))
1046 for (conv = lookup_conversions (basetype); conv; conv = TREE_CHAIN (conv))
1050 tree cand = TREE_VALUE (conv);
1052 if (winner && winner == cand)
1055 candidate = non_reference (TREE_TYPE (TREE_TYPE (cand)));
1057 switch (TREE_CODE (candidate))
1061 win = (desires & WANT_INT); break;
1063 win = (desires & WANT_ENUM); break;
1065 win = (desires & WANT_FLOAT); break;
1067 win = (desires & WANT_POINTER); break;
1079 error ("ambiguous default type conversion from `%T'",
1081 error (" candidate conversions include `%D' and `%D'",
1084 return error_mark_node;
1093 tree type = non_reference (TREE_TYPE (TREE_TYPE (winner)));
1094 return build_user_type_conversion (type, expr, LOOKUP_NORMAL);
1100 /* Implements integral promotion (4.1) and float->double promotion. */
1103 type_promotes_to (tree type)
1105 if (type == error_mark_node)
1106 return error_mark_node;
1108 type = TYPE_MAIN_VARIANT (type);
1110 /* bool always promotes to int (not unsigned), even if it's the same
1112 if (type == boolean_type_node)
1113 type = integer_type_node;
1115 /* Normally convert enums to int, but convert wide enums to something
1117 else if (TREE_CODE (type) == ENUMERAL_TYPE
1118 || type == wchar_type_node)
1120 int precision = MAX (TYPE_PRECISION (type),
1121 TYPE_PRECISION (integer_type_node));
1122 tree totype = c_common_type_for_size (precision, 0);
1123 if (TYPE_UNSIGNED (type)
1124 && ! int_fits_type_p (TYPE_MAX_VALUE (type), totype))
1125 type = c_common_type_for_size (precision, 1);
1129 else if (c_promoting_integer_type_p (type))
1131 /* Retain unsignedness if really not getting bigger. */
1132 if (TYPE_UNSIGNED (type)
1133 && TYPE_PRECISION (type) == TYPE_PRECISION (integer_type_node))
1134 type = unsigned_type_node;
1136 type = integer_type_node;
1138 else if (type == float_type_node)
1139 type = double_type_node;
1144 /* The routines below this point are carefully written to conform to
1145 the standard. They use the same terminology, and follow the rules
1146 closely. Although they are used only in pt.c at the moment, they
1147 should presumably be used everywhere in the future. */
1149 /* Attempt to perform qualification conversions on EXPR to convert it
1150 to TYPE. Return the resulting expression, or error_mark_node if
1151 the conversion was impossible. */
1154 perform_qualification_conversions (tree type, tree expr)
1158 expr_type = TREE_TYPE (expr);
1160 if (TYPE_PTR_P (type) && TYPE_PTR_P (expr_type)
1161 && comp_ptr_ttypes (TREE_TYPE (type), TREE_TYPE (expr_type)))
1162 return build_nop (type, expr);
1163 else if (TYPE_PTR_TO_MEMBER_P (type)
1164 && TYPE_PTR_TO_MEMBER_P (expr_type)
1165 && same_type_p (TYPE_PTRMEM_CLASS_TYPE (type),
1166 TYPE_PTRMEM_CLASS_TYPE (expr_type))
1167 && comp_ptr_ttypes (TYPE_PTRMEM_POINTED_TO_TYPE (type),
1168 TYPE_PTRMEM_POINTED_TO_TYPE (expr_type)))
1169 return build_nop (type, expr);
1171 return error_mark_node;