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);
83 if (IS_AGGR_TYPE (intype))
85 intype = complete_type (intype);
86 if (!COMPLETE_TYPE_P (intype))
88 error ("can't convert from incomplete type `%T' to `%T'",
90 return error_mark_node;
93 rval = build_type_conversion (type, expr);
96 if (rval == error_mark_node)
97 error ("conversion of `%E' from `%T' to `%T' is ambiguous",
103 /* Handle anachronistic conversions from (::*)() to cv void* or (*)(). */
104 if (TREE_CODE (type) == POINTER_TYPE
105 && (TREE_CODE (TREE_TYPE (type)) == FUNCTION_TYPE
106 || VOID_TYPE_P (TREE_TYPE (type))))
108 /* Allow an implicit this pointer for pointer to member
110 if (TYPE_PTRMEMFUNC_P (intype))
112 if (pedantic || warn_pmf2ptr)
113 pedwarn ("converting from `%T' to `%T'", intype, type);
114 if (TREE_CODE (expr) == PTRMEM_CST)
115 expr = build_address (PTRMEM_CST_MEMBER (expr));
118 tree decl = maybe_dummy_object (TYPE_PTRMEM_CLASS_TYPE (intype),
120 decl = build_address (decl);
121 expr = get_member_function_from_ptrfunc (&decl, expr);
124 else if (TREE_CODE (TREE_TYPE (expr)) == METHOD_TYPE)
126 if (pedantic || warn_pmf2ptr)
127 pedwarn ("converting from `%T' to `%T'", intype, type);
128 expr = build_addr_func (expr);
130 if (TREE_CODE (TREE_TYPE (expr)) == POINTER_TYPE)
131 return build_nop (type, expr);
132 intype = TREE_TYPE (expr);
135 if (expr == error_mark_node)
136 return error_mark_node;
138 form = TREE_CODE (intype);
140 if (POINTER_TYPE_P (intype))
142 intype = TYPE_MAIN_VARIANT (intype);
144 if (TYPE_MAIN_VARIANT (type) != intype
145 && TREE_CODE (type) == POINTER_TYPE
146 && TREE_CODE (TREE_TYPE (type)) == RECORD_TYPE
147 && IS_AGGR_TYPE (TREE_TYPE (type))
148 && IS_AGGR_TYPE (TREE_TYPE (intype))
149 && TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE)
151 enum tree_code code = PLUS_EXPR;
157 intype_class = TREE_TYPE (intype);
158 type_class = TREE_TYPE (type);
160 same_p = same_type_p (TYPE_MAIN_VARIANT (intype_class),
161 TYPE_MAIN_VARIANT (type_class));
163 /* Try derived to base conversion. */
165 binfo = lookup_base (intype_class, type_class, ba_check, NULL);
166 if (!same_p && !binfo)
168 /* Try base to derived conversion. */
169 binfo = lookup_base (type_class, intype_class, ba_check, NULL);
172 if (binfo == error_mark_node)
173 return error_mark_node;
177 expr = build_base_path (code, expr, binfo, 0);
178 /* Add any qualifier conversions. */
179 return build_nop (type, expr);
183 if (TYPE_PTRMEMFUNC_P (type))
185 error ("cannot convert `%E' from type `%T' to type `%T'",
187 return error_mark_node;
190 return build_nop (type, expr);
192 else if (TYPE_PTRMEM_P (type) && TYPE_PTRMEM_P (intype))
197 enum tree_code code = PLUS_EXPR;
200 b1 = TYPE_PTRMEM_CLASS_TYPE (type);
201 b2 = TYPE_PTRMEM_CLASS_TYPE (intype);
202 binfo = lookup_base (b1, b2, ba_check, &bk);
205 binfo = lookup_base (b2, b1, ba_check, &bk);
208 if (binfo == error_mark_node)
209 return error_mark_node;
211 if (bk == bk_via_virtual)
214 warning ("pointer to member cast from `%T' to `%T' is via virtual base",
218 error ("pointer to member cast from `%T' to `%T' is via virtual base",
220 return error_mark_node;
222 /* This is a reinterpret cast, whose result is unspecified.
223 We choose to do nothing. */
224 return build1 (NOP_EXPR, type, expr);
227 if (TREE_CODE (expr) == PTRMEM_CST)
228 expr = cplus_expand_constant (expr);
230 if (binfo && !integer_zerop (BINFO_OFFSET (binfo)))
231 expr = size_binop (code,
232 build_nop (sizetype, expr),
233 BINFO_OFFSET (binfo));
234 return build_nop (type, expr);
236 else if (TYPE_PTRMEMFUNC_P (type) && TYPE_PTRMEMFUNC_P (intype))
237 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), expr, 0);
238 else if (TYPE_PTRMEMFUNC_P (intype))
242 if (TREE_CODE (expr) == PTRMEM_CST)
243 return cp_convert_to_pointer (type,
244 PTRMEM_CST_MEMBER (expr),
246 else if (TREE_CODE (expr) == OFFSET_REF)
248 tree object = TREE_OPERAND (expr, 0);
249 return get_member_function_from_ptrfunc (&object,
250 TREE_OPERAND (expr, 1));
253 error ("cannot convert `%E' from type `%T' to type `%T'",
255 return error_mark_node;
258 if (integer_zerop (expr))
260 if (TYPE_PTRMEMFUNC_P (type))
261 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), expr, 0);
263 if (TYPE_PTRMEM_P (type))
265 /* A NULL pointer-to-member is represented by -1, not by
267 expr = build_int_cst (type, -1);
268 /* Fix up the representation of -1 if appropriate. */
269 expr = force_fit_type (expr, 0, false, false);
272 expr = build_int_cst (type, 0);
276 else if (TYPE_PTR_TO_MEMBER_P (type) && INTEGRAL_CODE_P (form))
278 error ("invalid conversion from '%T' to '%T'", intype, type);
279 return error_mark_node;
282 if (INTEGRAL_CODE_P (form))
284 if (TYPE_PRECISION (intype) == POINTER_SIZE)
285 return build1 (CONVERT_EXPR, type, expr);
286 expr = cp_convert (c_common_type_for_size (POINTER_SIZE, 0), expr);
287 /* Modes may be different but sizes should be the same. */
288 if (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (expr)))
289 != GET_MODE_SIZE (TYPE_MODE (type)))
290 /* There is supposed to be some integral type
291 that is the same width as a pointer. */
293 return convert_to_pointer (type, expr);
296 if (type_unknown_p (expr))
297 return instantiate_type (type, expr, tf_error | tf_warning);
299 error ("cannot convert `%E' from type `%T' to type `%T'",
301 return error_mark_node;
304 /* Like convert, except permit conversions to take place which
305 are not normally allowed due to access restrictions
306 (such as conversion from sub-type to private super-type). */
309 convert_to_pointer_force (tree type, tree expr)
311 tree intype = TREE_TYPE (expr);
312 enum tree_code form = TREE_CODE (intype);
314 if (form == POINTER_TYPE)
316 intype = TYPE_MAIN_VARIANT (intype);
318 if (TYPE_MAIN_VARIANT (type) != intype
319 && TREE_CODE (TREE_TYPE (type)) == RECORD_TYPE
320 && IS_AGGR_TYPE (TREE_TYPE (type))
321 && IS_AGGR_TYPE (TREE_TYPE (intype))
322 && TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE)
324 enum tree_code code = PLUS_EXPR;
327 binfo = lookup_base (TREE_TYPE (intype), TREE_TYPE (type),
331 binfo = lookup_base (TREE_TYPE (type), TREE_TYPE (intype),
335 if (binfo == error_mark_node)
336 return error_mark_node;
339 expr = build_base_path (code, expr, binfo, 0);
340 if (expr == error_mark_node)
341 return error_mark_node;
342 /* Add any qualifier conversions. */
343 if (!same_type_p (TREE_TYPE (TREE_TYPE (expr)),
345 expr = build_nop (type, expr);
351 return cp_convert_to_pointer (type, expr, true);
354 /* We are passing something to a function which requires a reference.
355 The type we are interested in is in TYPE. The initial
356 value we have to begin with is in ARG.
358 FLAGS controls how we manage access checking.
359 DIRECT_BIND in FLAGS controls how any temporaries are generated.
360 If DIRECT_BIND is set, DECL is the reference we're binding to. */
363 build_up_reference (tree type, tree arg, int flags, tree decl)
366 tree argtype = TREE_TYPE (arg);
367 tree target_type = TREE_TYPE (type);
369 gcc_assert (TREE_CODE (type) == REFERENCE_TYPE);
371 if ((flags & DIRECT_BIND) && ! real_lvalue_p (arg))
373 /* Create a new temporary variable. We can't just use a TARGET_EXPR
374 here because it needs to live as long as DECL. */
377 arg = make_temporary_var_for_ref_to_temp (decl, TREE_TYPE (arg));
379 /* Process the initializer for the declaration. */
380 DECL_INITIAL (arg) = targ;
381 cp_finish_decl (arg, targ, NULL_TREE,
382 LOOKUP_ONLYCONVERTING|DIRECT_BIND);
384 else if (!(flags & DIRECT_BIND) && ! lvalue_p (arg))
385 return get_target_expr (arg);
387 /* If we had a way to wrap this up, and say, if we ever needed its
388 address, transform all occurrences of the register, into a memory
389 reference we could win better. */
390 rval = build_unary_op (ADDR_EXPR, arg, 1);
391 if (rval == error_mark_node)
392 return error_mark_node;
394 if ((flags & LOOKUP_PROTECT)
395 && TYPE_MAIN_VARIANT (argtype) != TYPE_MAIN_VARIANT (target_type)
396 && IS_AGGR_TYPE (argtype)
397 && IS_AGGR_TYPE (target_type))
399 /* We go through lookup_base for the access control. */
400 tree binfo = lookup_base (argtype, target_type, ba_check, NULL);
401 if (binfo == error_mark_node)
402 return error_mark_node;
403 if (binfo == NULL_TREE)
404 return error_not_base_type (target_type, argtype);
405 rval = build_base_path (PLUS_EXPR, rval, binfo, 1);
409 = convert_to_pointer_force (build_pointer_type (target_type), rval);
410 return build_nop (type, rval);
413 /* Subroutine of convert_to_reference. REFTYPE is the target reference type.
414 INTYPE is the original rvalue type and DECL is an optional _DECL node
417 [dcl.init.ref] says that if an rvalue is used to
418 initialize a reference, then the reference must be to a
419 non-volatile const type. */
422 warn_ref_binding (tree reftype, tree intype, tree decl)
424 tree ttl = TREE_TYPE (reftype);
426 if (!CP_TYPE_CONST_NON_VOLATILE_P (ttl))
430 if (CP_TYPE_VOLATILE_P (ttl) && decl)
431 msg = "initialization of volatile reference type `%#T' from rvalue of type `%T'";
432 else if (CP_TYPE_VOLATILE_P (ttl))
433 msg = "conversion to volatile reference type `%#T' from rvalue of type `%T'";
435 msg = "initialization of non-const reference type `%#T' from rvalue of type `%T'";
437 msg = "conversion to non-const reference type `%#T' from rvalue of type `%T'";
439 pedwarn (msg, reftype, intype);
443 /* For C++: Only need to do one-level references, but cannot
444 get tripped up on signed/unsigned differences.
446 DECL is either NULL_TREE or the _DECL node for a reference that is being
447 initialized. It can be error_mark_node if we don't know the _DECL but
448 we know it's an initialization. */
451 convert_to_reference (tree reftype, tree expr, int convtype,
452 int flags, tree decl)
454 tree type = TYPE_MAIN_VARIANT (TREE_TYPE (reftype));
456 tree rval = NULL_TREE;
457 tree rval_as_conversion = NULL_TREE;
458 bool can_convert_intype_to_type;
460 if (TREE_CODE (type) == FUNCTION_TYPE
461 && TREE_TYPE (expr) == unknown_type_node)
462 expr = instantiate_type (type, expr,
463 (flags & LOOKUP_COMPLAIN)
464 ? tf_error | tf_warning : tf_none);
466 expr = convert_from_reference (expr);
468 if (expr == error_mark_node)
469 return error_mark_node;
471 intype = TREE_TYPE (expr);
473 gcc_assert (TREE_CODE (intype) != REFERENCE_TYPE);
475 intype = TYPE_MAIN_VARIANT (intype);
477 can_convert_intype_to_type = can_convert (type, intype);
478 if (!can_convert_intype_to_type
479 && (convtype & CONV_IMPLICIT) && IS_AGGR_TYPE (intype)
480 && ! (flags & LOOKUP_NO_CONVERSION))
482 /* Look for a user-defined conversion to lvalue that we can use. */
485 = build_type_conversion (reftype, expr);
487 if (rval_as_conversion && rval_as_conversion != error_mark_node
488 && real_lvalue_p (rval_as_conversion))
490 expr = rval_as_conversion;
491 rval_as_conversion = NULL_TREE;
493 can_convert_intype_to_type = 1;
497 if (((convtype & CONV_STATIC) && can_convert (intype, type))
498 || ((convtype & CONV_IMPLICIT) && can_convert_intype_to_type))
500 if (flags & LOOKUP_COMPLAIN)
502 tree ttl = TREE_TYPE (reftype);
503 tree ttr = lvalue_type (expr);
505 if (! real_lvalue_p (expr))
506 warn_ref_binding (reftype, intype, decl);
508 if (! (convtype & CONV_CONST)
509 && !at_least_as_qualified_p (ttl, ttr))
510 pedwarn ("conversion from `%T' to `%T' discards qualifiers",
514 return build_up_reference (reftype, expr, flags, decl);
516 else if ((convtype & CONV_REINTERPRET) && lvalue_p (expr))
518 /* When casting an lvalue to a reference type, just convert into
519 a pointer to the new type and deference it. This is allowed
520 by San Diego WP section 5.2.9 paragraph 12, though perhaps it
521 should be done directly (jason). (int &)ri ---> *(int*)&ri */
523 /* B* bp; A& ar = (A&)bp; is valid, but it's probably not what they
525 if (TREE_CODE (intype) == POINTER_TYPE
526 && (comptypes (TREE_TYPE (intype), type,
527 COMPARE_BASE | COMPARE_DERIVED)))
528 warning ("casting `%T' to `%T' does not dereference pointer",
531 rval = build_unary_op (ADDR_EXPR, expr, 0);
532 if (rval != error_mark_node)
533 rval = convert_force (build_pointer_type (TREE_TYPE (reftype)),
535 if (rval != error_mark_node)
536 rval = build1 (NOP_EXPR, reftype, rval);
540 rval = convert_for_initialization (NULL_TREE, type, expr, flags,
542 if (rval == NULL_TREE || rval == error_mark_node)
544 warn_ref_binding (reftype, intype, decl);
545 rval = build_up_reference (reftype, rval, flags, decl);
550 /* If we found a way to convert earlier, then use it. */
554 if (flags & LOOKUP_COMPLAIN)
555 error ("cannot convert type `%T' to type `%T'", intype, reftype);
557 return error_mark_node;
560 /* We are using a reference VAL for its value. Bash that reference all the
561 way down to its lowest form. */
564 convert_from_reference (tree val)
566 if (TREE_CODE (TREE_TYPE (val)) == REFERENCE_TYPE)
567 return build_indirect_ref (val, NULL);
571 /* Implicitly convert the lvalue EXPR to another lvalue of type TOTYPE,
572 preserving cv-qualification. */
575 convert_lvalue (tree totype, tree expr)
577 totype = cp_build_qualified_type (totype, TYPE_QUALS (TREE_TYPE (expr)));
578 totype = build_reference_type (totype);
579 expr = convert_to_reference (totype, expr, CONV_IMPLICIT, LOOKUP_NORMAL,
581 return convert_from_reference (expr);
584 /* Really perform an lvalue-to-rvalue conversion, including copying an
585 argument of class type into a temporary. */
588 force_rvalue (tree expr)
590 if (IS_AGGR_TYPE (TREE_TYPE (expr)) && TREE_CODE (expr) != TARGET_EXPR)
591 expr = ocp_convert (TREE_TYPE (expr), expr,
592 CONV_IMPLICIT|CONV_FORCE_TEMP, LOOKUP_NORMAL);
594 expr = decay_conversion (expr);
599 /* C++ conversions, preference to static cast conversions. */
602 cp_convert (tree type, tree expr)
604 return ocp_convert (type, expr, CONV_OLD_CONVERT, LOOKUP_NORMAL);
609 FLAGS indicates how we should behave. */
612 ocp_convert (tree type, tree expr, int convtype, int flags)
615 enum tree_code code = TREE_CODE (type);
617 if (error_operand_p (e) || type == error_mark_node)
618 return error_mark_node;
620 complete_type (type);
621 complete_type (TREE_TYPE (expr));
623 e = decl_constant_value (e);
625 if (IS_AGGR_TYPE (type) && (convtype & CONV_FORCE_TEMP)
626 /* Some internal structures (vtable_entry_type, sigtbl_ptr_type)
627 don't go through finish_struct, so they don't have the synthesized
628 constructors. So don't force a temporary. */
629 && TYPE_HAS_CONSTRUCTOR (type))
630 /* We need a new temporary; don't take this shortcut. */;
631 else if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (e)))
633 if (same_type_p (type, TREE_TYPE (e)))
634 /* The call to fold will not always remove the NOP_EXPR as
635 might be expected, since if one of the types is a typedef;
636 the comparison in fold is just equality of pointers, not a
637 call to comptypes. We don't call fold in this case because
638 that can result in infinite recursion; fold will call
639 convert, which will call ocp_convert, etc. */
641 /* For complex data types, we need to perform componentwise
643 else if (TREE_CODE (type) == COMPLEX_TYPE)
644 return fold (convert_to_complex (type, e));
645 else if (TREE_CODE (e) == TARGET_EXPR)
647 /* Don't build a NOP_EXPR of class type. Instead, change the
648 type of the temporary. Only allow this for cv-qual changes,
650 if (!same_type_p (TYPE_MAIN_VARIANT (TREE_TYPE (e)),
651 TYPE_MAIN_VARIANT (type)))
653 TREE_TYPE (e) = TREE_TYPE (TARGET_EXPR_SLOT (e)) = type;
656 else if (TREE_ADDRESSABLE (type))
657 /* We shouldn't be treating objects of ADDRESSABLE type as rvalues. */
660 return fold (build1 (NOP_EXPR, type, e));
663 if (code == VOID_TYPE && (convtype & CONV_STATIC))
665 e = convert_to_void (e, /*implicit=*/NULL);
669 if (INTEGRAL_CODE_P (code))
671 tree intype = TREE_TYPE (e);
672 /* enum = enum, enum = int, enum = float, (enum)pointer are all
674 if (TREE_CODE (type) == ENUMERAL_TYPE
675 && ((ARITHMETIC_TYPE_P (intype) && ! (convtype & CONV_STATIC))
676 || (TREE_CODE (intype) == POINTER_TYPE)))
678 pedwarn ("conversion from `%#T' to `%#T'", intype, type);
680 if (flag_pedantic_errors)
681 return error_mark_node;
683 if (IS_AGGR_TYPE (intype))
686 rval = build_type_conversion (type, e);
689 if (flags & LOOKUP_COMPLAIN)
690 error ("`%#T' used where a `%T' was expected", intype, type);
691 return error_mark_node;
693 if (code == BOOLEAN_TYPE)
694 return cp_truthvalue_conversion (e);
696 return fold (convert_to_integer (type, e));
698 if (POINTER_TYPE_P (type) || TYPE_PTR_TO_MEMBER_P (type))
699 return fold (cp_convert_to_pointer (type, e, false));
700 if (code == VECTOR_TYPE)
701 return fold (convert_to_vector (type, e));
702 if (code == REAL_TYPE || code == COMPLEX_TYPE)
704 if (IS_AGGR_TYPE (TREE_TYPE (e)))
707 rval = build_type_conversion (type, e);
711 if (flags & LOOKUP_COMPLAIN)
712 error ("`%#T' used where a floating point value was expected",
715 if (code == REAL_TYPE)
716 return fold (convert_to_real (type, e));
717 else if (code == COMPLEX_TYPE)
718 return fold (convert_to_complex (type, e));
721 /* New C++ semantics: since assignment is now based on
722 memberwise copying, if the rhs type is derived from the
723 lhs type, then we may still do a conversion. */
724 if (IS_AGGR_TYPE_CODE (code))
726 tree dtype = TREE_TYPE (e);
727 tree ctor = NULL_TREE;
729 dtype = TYPE_MAIN_VARIANT (dtype);
731 /* Conversion between aggregate types. New C++ semantics allow
732 objects of derived type to be cast to objects of base type.
733 Old semantics only allowed this between pointers.
735 There may be some ambiguity between using a constructor
736 vs. using a type conversion operator when both apply. */
740 if (abstract_virtuals_error (NULL_TREE, type))
741 return error_mark_node;
743 if ((flags & LOOKUP_ONLYCONVERTING)
744 && ! (IS_AGGR_TYPE (dtype) && DERIVED_FROM_P (type, dtype)))
745 /* For copy-initialization, first we create a temp of the proper type
746 with a user-defined conversion sequence, then we direct-initialize
747 the target with the temp (see [dcl.init]). */
748 ctor = build_user_type_conversion (type, ctor, flags);
750 ctor = build_special_member_call (NULL_TREE,
751 complete_ctor_identifier,
752 build_tree_list (NULL_TREE, ctor),
755 return build_cplus_new (type, ctor);
758 if (flags & LOOKUP_COMPLAIN)
759 error ("conversion from `%T' to non-scalar type `%T' requested",
760 TREE_TYPE (expr), type);
761 return error_mark_node;
764 /* When an expression is used in a void context, its value is discarded and
765 no lvalue-rvalue and similar conversions happen [expr.static.cast/4,
766 stmt.expr/1, expr.comma/1]. This permits dereferencing an incomplete type
767 in a void context. The C++ standard does not define what an `access' to an
768 object is, but there is reason to believe that it is the lvalue to rvalue
769 conversion -- if it were not, `*&*p = 1' would violate [expr]/4 in that it
770 accesses `*p' not to calculate the value to be stored. But, dcl.type.cv/8
771 indicates that volatile semantics should be the same between C and C++
772 where ever possible. C leaves it implementation defined as to what
773 constitutes an access to a volatile. So, we interpret `*vp' as a read of
774 the volatile object `vp' points to, unless that is an incomplete type. For
775 volatile references we do not do this interpretation, because that would
776 make it impossible to ignore the reference return value from functions. We
777 issue warnings in the confusing cases.
779 IMPLICIT is tells us the context of an implicit void conversion. */
782 convert_to_void (tree expr, const char *implicit)
784 if (expr == error_mark_node
785 || TREE_TYPE (expr) == error_mark_node)
786 return error_mark_node;
787 if (!TREE_TYPE (expr))
789 if (invalid_nonstatic_memfn_p (expr))
790 return error_mark_node;
791 if (VOID_TYPE_P (TREE_TYPE (expr)))
793 switch (TREE_CODE (expr))
797 /* The two parts of a cond expr might be separate lvalues. */
798 tree op1 = TREE_OPERAND (expr,1);
799 tree op2 = TREE_OPERAND (expr,2);
800 tree new_op1 = convert_to_void
801 (op1, (implicit && !TREE_SIDE_EFFECTS (op2)
802 ? "second operand of conditional" : NULL));
803 tree new_op2 = convert_to_void
804 (op2, (implicit && !TREE_SIDE_EFFECTS (op1)
805 ? "third operand of conditional" : NULL));
807 expr = build3 (COND_EXPR, TREE_TYPE (new_op1),
808 TREE_OPERAND (expr, 0), new_op1, new_op2);
814 /* The second part of a compound expr contains the value. */
815 tree op1 = TREE_OPERAND (expr,1);
816 tree new_op1 = convert_to_void
817 (op1, (implicit && !TREE_NO_WARNING (expr)
818 ? "right-hand operand of comma" : NULL));
822 tree t = build2 (COMPOUND_EXPR, TREE_TYPE (new_op1),
823 TREE_OPERAND (expr, 0), new_op1);
830 case NON_LVALUE_EXPR:
832 /* These have already decayed to rvalue. */
835 case CALL_EXPR: /* We have a special meaning for volatile void fn(). */
840 tree type = TREE_TYPE (expr);
841 int is_reference = TREE_CODE (TREE_TYPE (TREE_OPERAND (expr, 0)))
843 int is_volatile = TYPE_VOLATILE (type);
844 int is_complete = COMPLETE_TYPE_P (complete_type (type));
846 if (is_volatile && !is_complete)
847 warning ("object of incomplete type `%T' will not be accessed in %s",
848 type, implicit ? implicit : "void context");
849 else if (is_reference && is_volatile)
850 warning ("object of type `%T' will not be accessed in %s",
851 TREE_TYPE (TREE_OPERAND (expr, 0)),
852 implicit ? implicit : "void context");
853 if (is_reference || !is_volatile || !is_complete)
854 expr = TREE_OPERAND (expr, 0);
861 /* External variables might be incomplete. */
862 tree type = TREE_TYPE (expr);
863 int is_complete = COMPLETE_TYPE_P (complete_type (type));
865 if (TYPE_VOLATILE (type) && !is_complete)
866 warning ("object `%E' of incomplete type `%T' will not be accessed in %s",
867 expr, type, implicit ? implicit : "void context");
876 if (TREE_CODE (probe) == ADDR_EXPR)
877 probe = TREE_OPERAND (expr, 0);
878 if (type_unknown_p (probe))
880 /* [over.over] enumerates the places where we can take the address
881 of an overloaded function, and this is not one of them. */
882 pedwarn ("%s cannot resolve address of overloaded function",
883 implicit ? implicit : "void cast");
884 expr = void_zero_node;
886 else if (implicit && probe == expr && is_overloaded_fn (probe))
887 /* Only warn when there is no &. */
888 warning ("%s is a reference, not call, to function `%E'",
892 if (expr != error_mark_node && !VOID_TYPE_P (TREE_TYPE (expr)))
894 if (implicit && warn_unused_value
895 && !TREE_SIDE_EFFECTS (expr) && !TREE_NO_WARNING (expr))
896 warning ("%s has no effect", implicit);
897 expr = build1 (CONVERT_EXPR, void_type_node, expr);
902 /* Create an expression whose value is that of EXPR,
903 converted to type TYPE. The TREE_TYPE of the value
904 is always TYPE. This function implements all reasonable
905 conversions; callers should filter out those that are
906 not permitted by the language being compiled.
908 Most of this routine is from build_reinterpret_cast.
910 The backend cannot call cp_convert (what was convert) because
911 conversions to/from basetypes may involve memory references
912 (vbases) and adding or subtracting small values (multiple
913 inheritance), but it calls convert from the constant folding code
914 on subtrees of already built trees after it has ripped them apart.
916 Also, if we ever support range variables, we'll probably also have to
917 do a little bit more work. */
920 convert (tree type, tree expr)
924 if (type == error_mark_node || expr == error_mark_node)
925 return error_mark_node;
927 intype = TREE_TYPE (expr);
929 if (POINTER_TYPE_P (type) && POINTER_TYPE_P (intype))
931 expr = decl_constant_value (expr);
932 return fold (build1 (NOP_EXPR, type, expr));
935 return ocp_convert (type, expr, CONV_OLD_CONVERT,
936 LOOKUP_NORMAL|LOOKUP_NO_CONVERSION);
939 /* Like cp_convert, except permit conversions to take place which
940 are not normally allowed due to access restrictions
941 (such as conversion from sub-type to private super-type). */
944 convert_force (tree type, tree expr, int convtype)
947 enum tree_code code = TREE_CODE (type);
949 if (code == REFERENCE_TYPE)
950 return fold (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 (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))
966 /* compatible pointer to member functions. */
967 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), e, 1);
970 return ocp_convert (type, e, CONV_C_CAST|convtype, LOOKUP_NORMAL);
973 /* Convert an aggregate EXPR to type XTYPE. If a conversion
974 exists, return the attempted conversion. This may
975 return ERROR_MARK_NODE if the conversion is not
976 allowed (references private members, etc).
977 If no conversion exists, NULL_TREE is returned.
979 FIXME: Ambiguity checking is wrong. Should choose one by the implicit
980 object parameter, or by the second standard conversion sequence if
981 that doesn't do it. This will probably wait for an overloading rewrite.
985 build_type_conversion (tree xtype, tree expr)
987 /* C++: check to see if we can convert this aggregate type
988 into the required type. */
989 return build_user_type_conversion (xtype, expr, LOOKUP_NORMAL);
992 /* Convert the given EXPR to one of a group of types suitable for use in an
993 expression. DESIRES is a combination of various WANT_* flags (q.v.)
994 which indicates which types are suitable. If COMPLAIN is true, complain
995 about ambiguity; otherwise, the caller will deal with it. */
998 build_expr_type_conversion (int desires, tree expr, bool complain)
1000 tree basetype = TREE_TYPE (expr);
1001 tree conv = NULL_TREE;
1002 tree winner = NULL_TREE;
1004 if (expr == null_node
1005 && (desires & WANT_INT)
1006 && !(desires & WANT_NULL))
1007 warning ("converting NULL to non-pointer type");
1009 expr = convert_from_reference (expr);
1010 basetype = TREE_TYPE (expr);
1012 if (basetype == error_mark_node)
1013 return error_mark_node;
1015 if (! IS_AGGR_TYPE (basetype))
1016 switch (TREE_CODE (basetype))
1019 if ((desires & WANT_NULL) && null_ptr_cst_p (expr))
1021 /* else fall through... */
1024 return (desires & WANT_INT) ? expr : NULL_TREE;
1026 return (desires & WANT_ENUM) ? expr : NULL_TREE;
1028 return (desires & WANT_FLOAT) ? expr : NULL_TREE;
1030 return (desires & WANT_POINTER) ? expr : NULL_TREE;
1034 return (desires & WANT_POINTER) ? decay_conversion (expr)
1040 /* The code for conversions from class type is currently only used for
1041 delete expressions. Other expressions are handled by build_new_op. */
1042 if (!complete_type_or_else (basetype, expr))
1043 return error_mark_node;
1044 if (!TYPE_HAS_CONVERSION (basetype))
1047 for (conv = lookup_conversions (basetype); conv; conv = TREE_CHAIN (conv))
1051 tree cand = TREE_VALUE (conv);
1053 if (winner && winner == cand)
1056 candidate = non_reference (TREE_TYPE (TREE_TYPE (cand)));
1058 switch (TREE_CODE (candidate))
1062 win = (desires & WANT_INT); break;
1064 win = (desires & WANT_ENUM); break;
1066 win = (desires & WANT_FLOAT); break;
1068 win = (desires & WANT_POINTER); break;
1080 error ("ambiguous default type conversion from `%T'",
1082 error (" candidate conversions include `%D' and `%D'",
1085 return error_mark_node;
1094 tree type = non_reference (TREE_TYPE (TREE_TYPE (winner)));
1095 return build_user_type_conversion (type, expr, LOOKUP_NORMAL);
1101 /* Implements integral promotion (4.1) and float->double promotion. */
1104 type_promotes_to (tree type)
1106 if (type == error_mark_node)
1107 return error_mark_node;
1109 type = TYPE_MAIN_VARIANT (type);
1111 /* bool always promotes to int (not unsigned), even if it's the same
1113 if (type == boolean_type_node)
1114 type = integer_type_node;
1116 /* Normally convert enums to int, but convert wide enums to something
1118 else if (TREE_CODE (type) == ENUMERAL_TYPE
1119 || type == wchar_type_node)
1121 int precision = MAX (TYPE_PRECISION (type),
1122 TYPE_PRECISION (integer_type_node));
1123 tree totype = c_common_type_for_size (precision, 0);
1124 if (TYPE_UNSIGNED (type)
1125 && ! int_fits_type_p (TYPE_MAX_VALUE (type), totype))
1126 type = c_common_type_for_size (precision, 1);
1130 else if (c_promoting_integer_type_p (type))
1132 /* Retain unsignedness if really not getting bigger. */
1133 if (TYPE_UNSIGNED (type)
1134 && TYPE_PRECISION (type) == TYPE_PRECISION (integer_type_node))
1135 type = unsigned_type_node;
1137 type = integer_type_node;
1139 else if (type == float_type_node)
1140 type = double_type_node;
1145 /* The routines below this point are carefully written to conform to
1146 the standard. They use the same terminology, and follow the rules
1147 closely. Although they are used only in pt.c at the moment, they
1148 should presumably be used everywhere in the future. */
1150 /* Attempt to perform qualification conversions on EXPR to convert it
1151 to TYPE. Return the resulting expression, or error_mark_node if
1152 the conversion was impossible. */
1155 perform_qualification_conversions (tree type, tree expr)
1159 expr_type = TREE_TYPE (expr);
1161 if (TYPE_PTR_P (type) && TYPE_PTR_P (expr_type)
1162 && comp_ptr_ttypes (TREE_TYPE (type), TREE_TYPE (expr_type)))
1163 return build_nop (type, expr);
1164 else if (TYPE_PTR_TO_MEMBER_P (type)
1165 && TYPE_PTR_TO_MEMBER_P (expr_type)
1166 && same_type_p (TYPE_PTRMEM_CLASS_TYPE (type),
1167 TYPE_PTRMEM_CLASS_TYPE (expr_type))
1168 && comp_ptr_ttypes (TYPE_PTRMEM_POINTED_TO_TYPE (type),
1169 TYPE_PTRMEM_POINTED_TO_TYPE (expr_type)))
1170 return build_nop (type, expr);
1172 return error_mark_node;