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, 2009
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 = 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 (c_inhibit_evaluation_warnings == 0
569 && !TREE_OVERFLOW_P (expr)
570 && result != error_mark_node)
571 warnings_for_convert_and_check (type, expr, result);
578 FLAGS indicates how we should behave. */
581 ocp_convert (tree type, tree expr, int convtype, int flags)
584 enum tree_code code = TREE_CODE (type);
585 const char *invalid_conv_diag;
588 if (error_operand_p (e) || type == error_mark_node)
589 return error_mark_node;
591 complete_type (type);
592 complete_type (TREE_TYPE (expr));
594 if ((invalid_conv_diag
595 = targetm.invalid_conversion (TREE_TYPE (expr), type)))
597 error (invalid_conv_diag);
598 return error_mark_node;
601 e = integral_constant_value (e);
603 if (MAYBE_CLASS_TYPE_P (type) && (convtype & CONV_FORCE_TEMP))
604 /* We need a new temporary; don't take this shortcut. */;
605 else if (same_type_ignoring_top_level_qualifiers_p (type, TREE_TYPE (e)))
607 if (same_type_p (type, TREE_TYPE (e)))
608 /* The call to fold will not always remove the NOP_EXPR as
609 might be expected, since if one of the types is a typedef;
610 the comparison in fold is just equality of pointers, not a
611 call to comptypes. We don't call fold in this case because
612 that can result in infinite recursion; fold will call
613 convert, which will call ocp_convert, etc. */
615 /* For complex data types, we need to perform componentwise
617 else if (TREE_CODE (type) == COMPLEX_TYPE)
618 return fold_if_not_in_template (convert_to_complex (type, e));
619 else if (TREE_CODE (e) == TARGET_EXPR)
621 /* Don't build a NOP_EXPR of class type. Instead, change the
622 type of the temporary. */
623 TREE_TYPE (e) = TREE_TYPE (TARGET_EXPR_SLOT (e)) = type;
628 /* We shouldn't be treating objects of ADDRESSABLE type as
630 gcc_assert (!TREE_ADDRESSABLE (type));
631 return fold_if_not_in_template (build_nop (type, e));
635 e1 = targetm.convert_to_type (type, e);
639 if (code == VOID_TYPE && (convtype & CONV_STATIC))
641 e = convert_to_void (e, /*implicit=*/NULL, tf_warning_or_error);
645 if (INTEGRAL_CODE_P (code))
647 tree intype = TREE_TYPE (e);
649 if (TREE_CODE (type) == ENUMERAL_TYPE)
651 /* enum = enum, enum = int, enum = float, (enum)pointer are all
653 if (((INTEGRAL_OR_ENUMERATION_TYPE_P (intype)
654 || TREE_CODE (intype) == REAL_TYPE)
655 && ! (convtype & CONV_STATIC))
656 || TREE_CODE (intype) == POINTER_TYPE)
658 if (flags & LOOKUP_COMPLAIN)
659 permerror (input_location, "conversion from %q#T to %q#T", intype, type);
661 if (!flag_permissive)
662 return error_mark_node;
665 /* [expr.static.cast]
667 8. A value of integral or enumeration type can be explicitly
668 converted to an enumeration type. The value is unchanged if
669 the original value is within the range of the enumeration
670 values. Otherwise, the resulting enumeration value is
672 if (TREE_CODE (expr) == INTEGER_CST && !int_fits_type_p (expr, type))
673 warning (OPT_Wconversion,
674 "the result of the conversion is unspecified because "
675 "%qE is outside the range of type %qT",
678 if (MAYBE_CLASS_TYPE_P (intype))
681 rval = build_type_conversion (type, e);
684 if (flags & LOOKUP_COMPLAIN)
685 error ("%q#T used where a %qT was expected", intype, type);
686 return error_mark_node;
688 if (code == BOOLEAN_TYPE)
689 return cp_truthvalue_conversion (e);
691 return fold_if_not_in_template (convert_to_integer (type, e));
693 if (POINTER_TYPE_P (type) || TYPE_PTR_TO_MEMBER_P (type))
694 return fold_if_not_in_template (cp_convert_to_pointer (type, e));
695 if (code == VECTOR_TYPE)
697 tree in_vtype = TREE_TYPE (e);
698 if (MAYBE_CLASS_TYPE_P (in_vtype))
701 ret_val = build_type_conversion (type, e);
704 if (flags & LOOKUP_COMPLAIN)
705 error ("%q#T used where a %qT was expected", in_vtype, type);
706 return error_mark_node;
708 return fold_if_not_in_template (convert_to_vector (type, e));
710 if (code == REAL_TYPE || code == COMPLEX_TYPE)
712 if (MAYBE_CLASS_TYPE_P (TREE_TYPE (e)))
715 rval = build_type_conversion (type, e);
719 if (flags & LOOKUP_COMPLAIN)
720 error ("%q#T used where a floating point value was expected",
723 if (code == REAL_TYPE)
724 return fold_if_not_in_template (convert_to_real (type, e));
725 else if (code == COMPLEX_TYPE)
726 return fold_if_not_in_template (convert_to_complex (type, e));
729 /* New C++ semantics: since assignment is now based on
730 memberwise copying, if the rhs type is derived from the
731 lhs type, then we may still do a conversion. */
732 if (RECORD_OR_UNION_CODE_P (code))
734 tree dtype = TREE_TYPE (e);
735 tree ctor = NULL_TREE;
737 dtype = TYPE_MAIN_VARIANT (dtype);
739 /* Conversion between aggregate types. New C++ semantics allow
740 objects of derived type to be cast to objects of base type.
741 Old semantics only allowed this between pointers.
743 There may be some ambiguity between using a constructor
744 vs. using a type conversion operator when both apply. */
748 if (abstract_virtuals_error (NULL_TREE, type))
749 return error_mark_node;
751 if (BRACE_ENCLOSED_INITIALIZER_P (ctor))
752 ctor = perform_implicit_conversion (type, ctor, tf_warning_or_error);
753 else if ((flags & LOOKUP_ONLYCONVERTING)
754 && ! (CLASS_TYPE_P (dtype) && DERIVED_FROM_P (type, dtype)))
755 /* For copy-initialization, first we create a temp of the proper type
756 with a user-defined conversion sequence, then we direct-initialize
757 the target with the temp (see [dcl.init]). */
758 ctor = build_user_type_conversion (type, ctor, flags);
761 VEC(tree,gc) *ctor_vec = make_tree_vector_single (ctor);
762 ctor = build_special_member_call (NULL_TREE,
763 complete_ctor_identifier,
766 tf_warning_or_error);
767 release_tree_vector (ctor_vec);
770 return build_cplus_new (type, ctor);
773 if (flags & LOOKUP_COMPLAIN)
775 /* If the conversion failed and expr was an invalid use of pointer to
776 member function, try to report a meaningful error. */
777 if (invalid_nonstatic_memfn_p (expr, tf_warning_or_error))
778 /* We displayed the error message. */;
780 error ("conversion from %qT to non-scalar type %qT requested",
781 TREE_TYPE (expr), type);
783 return error_mark_node;
786 /* When an expression is used in a void context, its value is discarded and
787 no lvalue-rvalue and similar conversions happen [expr.static.cast/4,
788 stmt.expr/1, expr.comma/1]. This permits dereferencing an incomplete type
789 in a void context. The C++ standard does not define what an `access' to an
790 object is, but there is reason to believe that it is the lvalue to rvalue
791 conversion -- if it were not, `*&*p = 1' would violate [expr]/4 in that it
792 accesses `*p' not to calculate the value to be stored. But, dcl.type.cv/8
793 indicates that volatile semantics should be the same between C and C++
794 where ever possible. C leaves it implementation defined as to what
795 constitutes an access to a volatile. So, we interpret `*vp' as a read of
796 the volatile object `vp' points to, unless that is an incomplete type. For
797 volatile references we do not do this interpretation, because that would
798 make it impossible to ignore the reference return value from functions. We
799 issue warnings in the confusing cases.
801 IMPLICIT is non-NULL iff an expression is being implicitly converted; it
802 is NULL when the user is explicitly converting an expression to void via
803 a cast. When non-NULL, IMPLICIT is a string indicating the context of
804 the implicit conversion. */
807 convert_to_void (tree expr, const char *implicit, tsubst_flags_t complain)
809 if (expr == error_mark_node
810 || TREE_TYPE (expr) == error_mark_node)
811 return error_mark_node;
812 if (!TREE_TYPE (expr))
814 if (invalid_nonstatic_memfn_p (expr, complain))
815 return error_mark_node;
816 if (TREE_CODE (expr) == PSEUDO_DTOR_EXPR)
818 if (complain & tf_error)
819 error ("pseudo-destructor is not called");
820 return error_mark_node;
822 if (VOID_TYPE_P (TREE_TYPE (expr)))
824 switch (TREE_CODE (expr))
828 /* The two parts of a cond expr might be separate lvalues. */
829 tree op1 = TREE_OPERAND (expr,1);
830 tree op2 = TREE_OPERAND (expr,2);
831 tree new_op1 = convert_to_void
832 (op1, (implicit && !TREE_SIDE_EFFECTS (op2)
833 ? "second operand of conditional" : NULL), complain);
834 tree new_op2 = convert_to_void
835 (op2, (implicit && !TREE_SIDE_EFFECTS (op1)
836 ? "third operand of conditional" : NULL), complain);
838 expr = build3 (COND_EXPR, TREE_TYPE (new_op1),
839 TREE_OPERAND (expr, 0), new_op1, new_op2);
845 /* The second part of a compound expr contains the value. */
846 tree op1 = TREE_OPERAND (expr,1);
847 tree new_op1 = convert_to_void
848 (op1, (implicit && !TREE_NO_WARNING (expr)
849 ? "right-hand operand of comma" : NULL), complain);
853 tree t = build2 (COMPOUND_EXPR, TREE_TYPE (new_op1),
854 TREE_OPERAND (expr, 0), new_op1);
861 case NON_LVALUE_EXPR:
863 /* These have already decayed to rvalue. */
866 case CALL_EXPR: /* We have a special meaning for volatile void fn(). */
871 tree type = TREE_TYPE (expr);
872 int is_reference = TREE_CODE (TREE_TYPE (TREE_OPERAND (expr, 0)))
874 int is_volatile = TYPE_VOLATILE (type);
875 int is_complete = COMPLETE_TYPE_P (complete_type (type));
877 /* Can't load the value if we don't know the type. */
878 if (is_volatile && !is_complete)
880 if (complain & tf_warning)
881 warning (0, "object of incomplete type %qT will not be accessed in %s",
882 type, implicit ? implicit : "void context");
884 /* Don't load the value if this is an implicit dereference, or if
885 the type needs to be handled by ctors/dtors. */
886 else if (is_volatile && (is_reference || TREE_ADDRESSABLE (type)))
888 if (complain & tf_warning)
889 warning (0, "object of type %qT will not be accessed in %s",
890 TREE_TYPE (TREE_OPERAND (expr, 0)),
891 implicit ? implicit : "void context");
893 if (is_reference || !is_volatile || !is_complete || TREE_ADDRESSABLE (type))
895 /* Emit a warning (if enabled) when the "effect-less" INDIRECT_REF
896 operation is stripped off. Note that we don't warn about
897 - an expression with TREE_NO_WARNING set. (For an example of
898 such expressions, see build_over_call in call.c.)
899 - automatic dereferencing of references, since the user cannot
900 control it. (See also warn_if_unused_value() in stmt.c.) */
901 if (warn_unused_value
903 && (complain & tf_warning)
904 && !TREE_NO_WARNING (expr)
906 warning (OPT_Wunused_value, "value computed is not used");
907 expr = TREE_OPERAND (expr, 0);
915 /* External variables might be incomplete. */
916 tree type = TREE_TYPE (expr);
917 int is_complete = COMPLETE_TYPE_P (complete_type (type));
919 if (TYPE_VOLATILE (type) && !is_complete && (complain & tf_warning))
920 warning (0, "object %qE of incomplete type %qT will not be accessed in %s",
921 expr, type, implicit ? implicit : "void context");
926 /* Don't bother with the temporary object returned from a function if
927 we don't use it and don't need to destroy it. We'll still
928 allocate space for it in expand_call or declare_return_variable,
929 but we don't need to track it through all the tree phases. */
930 if (TARGET_EXPR_IMPLICIT_P (expr)
931 && TYPE_HAS_TRIVIAL_DESTRUCTOR (TREE_TYPE (expr)))
933 tree init = TARGET_EXPR_INITIAL (expr);
934 if (TREE_CODE (init) == AGGR_INIT_EXPR
935 && !AGGR_INIT_VIA_CTOR_P (init))
937 tree fn = AGGR_INIT_EXPR_FN (init);
938 expr = build_call_array (TREE_TYPE (TREE_TYPE (TREE_TYPE (fn))),
940 aggr_init_expr_nargs (init),
941 AGGR_INIT_EXPR_ARGP (init));
951 if (TREE_CODE (probe) == ADDR_EXPR)
952 probe = TREE_OPERAND (expr, 0);
953 if (type_unknown_p (probe))
955 /* [over.over] enumerates the places where we can take the address
956 of an overloaded function, and this is not one of them. */
957 if (complain & tf_error)
958 error ("%s cannot resolve address of overloaded function",
959 implicit ? implicit : "void cast");
961 return error_mark_node;
962 expr = void_zero_node;
964 else if (implicit && probe == expr && is_overloaded_fn (probe))
966 /* Only warn when there is no &. */
967 if (complain & tf_warning)
968 warning (OPT_Waddress, "%s is a reference, not call, to function %qE",
970 if (TREE_CODE (expr) == COMPONENT_REF)
971 expr = TREE_OPERAND (expr, 0);
975 if (expr != error_mark_node && !VOID_TYPE_P (TREE_TYPE (expr)))
979 && !TREE_NO_WARNING (expr)
980 && !processing_template_decl)
982 /* The middle end does not warn about expressions that have
983 been explicitly cast to void, so we must do so here. */
984 if (!TREE_SIDE_EFFECTS (expr)) {
985 if (complain & tf_warning)
986 warning (OPT_Wunused_value, "%s has no effect", implicit);
992 enum tree_code_class tclass;
995 /* We might like to warn about (say) "(int) f()", as the
996 cast has no effect, but the compiler itself will
997 generate implicit conversions under some
998 circumstances. (For example a block copy will be
999 turned into a call to "__builtin_memcpy", with a
1000 conversion of the return value to an appropriate
1001 type.) So, to avoid false positives, we strip
1002 conversions. Do not use STRIP_NOPs because it will
1003 not strip conversions to "void", as that is not a
1004 mode-preserving conversion. */
1005 while (TREE_CODE (e) == NOP_EXPR)
1006 e = TREE_OPERAND (e, 0);
1008 code = TREE_CODE (e);
1009 tclass = TREE_CODE_CLASS (code);
1010 if ((tclass == tcc_comparison
1011 || tclass == tcc_unary
1012 || (tclass == tcc_binary
1013 && !(code == MODIFY_EXPR
1014 || code == INIT_EXPR
1015 || code == PREDECREMENT_EXPR
1016 || code == PREINCREMENT_EXPR
1017 || code == POSTDECREMENT_EXPR
1018 || code == POSTINCREMENT_EXPR)))
1019 && (complain & tf_warning))
1020 warning (OPT_Wunused_value, "value computed is not used");
1023 expr = build1 (CONVERT_EXPR, void_type_node, expr);
1025 if (! TREE_SIDE_EFFECTS (expr))
1026 expr = void_zero_node;
1030 /* Create an expression whose value is that of EXPR,
1031 converted to type TYPE. The TREE_TYPE of the value
1032 is always TYPE. This function implements all reasonable
1033 conversions; callers should filter out those that are
1034 not permitted by the language being compiled.
1036 Most of this routine is from build_reinterpret_cast.
1038 The back end cannot call cp_convert (what was convert) because
1039 conversions to/from basetypes may involve memory references
1040 (vbases) and adding or subtracting small values (multiple
1041 inheritance), but it calls convert from the constant folding code
1042 on subtrees of already built trees after it has ripped them apart.
1044 Also, if we ever support range variables, we'll probably also have to
1045 do a little bit more work. */
1048 convert (tree type, tree expr)
1052 if (type == error_mark_node || expr == error_mark_node)
1053 return error_mark_node;
1055 intype = TREE_TYPE (expr);
1057 if (POINTER_TYPE_P (type) && POINTER_TYPE_P (intype))
1058 return fold_if_not_in_template (build_nop (type, expr));
1060 return ocp_convert (type, expr, CONV_OLD_CONVERT,
1061 LOOKUP_NORMAL|LOOKUP_NO_CONVERSION);
1064 /* Like cp_convert, except permit conversions to take place which
1065 are not normally allowed due to access restrictions
1066 (such as conversion from sub-type to private super-type). */
1069 convert_force (tree type, tree expr, int convtype)
1072 enum tree_code code = TREE_CODE (type);
1074 if (code == REFERENCE_TYPE)
1075 return (fold_if_not_in_template
1076 (convert_to_reference (type, e, CONV_C_CAST, LOOKUP_COMPLAIN,
1079 if (code == POINTER_TYPE)
1080 return fold_if_not_in_template (convert_to_pointer_force (type, e));
1082 /* From typeck.c convert_for_assignment */
1083 if (((TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE && TREE_CODE (e) == ADDR_EXPR
1084 && TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE
1085 && TREE_CODE (TREE_TYPE (TREE_TYPE (e))) == METHOD_TYPE)
1086 || integer_zerop (e)
1087 || TYPE_PTRMEMFUNC_P (TREE_TYPE (e)))
1088 && TYPE_PTRMEMFUNC_P (type))
1089 /* compatible pointer to member functions. */
1090 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), e, 1,
1093 return ocp_convert (type, e, CONV_C_CAST|convtype, LOOKUP_NORMAL);
1096 /* Convert an aggregate EXPR to type XTYPE. If a conversion
1097 exists, return the attempted conversion. This may
1098 return ERROR_MARK_NODE if the conversion is not
1099 allowed (references private members, etc).
1100 If no conversion exists, NULL_TREE is returned.
1102 FIXME: Ambiguity checking is wrong. Should choose one by the implicit
1103 object parameter, or by the second standard conversion sequence if
1104 that doesn't do it. This will probably wait for an overloading rewrite.
1108 build_type_conversion (tree xtype, tree expr)
1110 /* C++: check to see if we can convert this aggregate type
1111 into the required type. */
1112 return build_user_type_conversion (xtype, expr, LOOKUP_NORMAL);
1115 /* Convert the given EXPR to one of a group of types suitable for use in an
1116 expression. DESIRES is a combination of various WANT_* flags (q.v.)
1117 which indicates which types are suitable. If COMPLAIN is true, complain
1118 about ambiguity; otherwise, the caller will deal with it. */
1121 build_expr_type_conversion (int desires, tree expr, bool complain)
1123 tree basetype = TREE_TYPE (expr);
1124 tree conv = NULL_TREE;
1125 tree winner = NULL_TREE;
1127 if (expr == null_node
1128 && (desires & WANT_INT)
1129 && !(desires & WANT_NULL))
1130 warning (OPT_Wconversion, "converting NULL to non-pointer type");
1132 basetype = TREE_TYPE (expr);
1134 if (basetype == error_mark_node)
1135 return error_mark_node;
1137 if (! MAYBE_CLASS_TYPE_P (basetype))
1138 switch (TREE_CODE (basetype))
1141 if ((desires & WANT_NULL) && null_ptr_cst_p (expr))
1143 /* else fall through... */
1146 return (desires & WANT_INT) ? expr : NULL_TREE;
1148 return (desires & WANT_ENUM) ? expr : NULL_TREE;
1150 return (desires & WANT_FLOAT) ? expr : NULL_TREE;
1152 return (desires & WANT_POINTER) ? expr : NULL_TREE;
1156 return (desires & WANT_POINTER) ? decay_conversion (expr)
1160 if ((desires & WANT_VECTOR) == 0)
1162 switch (TREE_CODE (TREE_TYPE (basetype)))
1166 return (desires & WANT_INT) ? expr : NULL_TREE;
1168 return (desires & WANT_ENUM) ? expr : NULL_TREE;
1170 return (desires & WANT_FLOAT) ? expr : NULL_TREE;
1179 /* The code for conversions from class type is currently only used for
1180 delete expressions. Other expressions are handled by build_new_op. */
1181 if (!complete_type_or_else (basetype, expr))
1182 return error_mark_node;
1183 if (!TYPE_HAS_CONVERSION (basetype))
1186 for (conv = lookup_conversions (basetype); conv; conv = TREE_CHAIN (conv))
1190 tree cand = TREE_VALUE (conv);
1192 if (winner && winner == cand)
1195 if (DECL_NONCONVERTING_P (cand))
1198 candidate = non_reference (TREE_TYPE (TREE_TYPE (cand)));
1200 switch (TREE_CODE (candidate))
1204 win = (desires & WANT_INT); break;
1206 win = (desires & WANT_ENUM); break;
1208 win = (desires & WANT_FLOAT); break;
1210 win = (desires & WANT_POINTER); break;
1213 if ((desires & WANT_VECTOR) == 0)
1215 switch (TREE_CODE (TREE_TYPE (candidate)))
1219 win = (desires & WANT_INT); break;
1221 win = (desires & WANT_ENUM); break;
1223 win = (desires & WANT_FLOAT); break;
1239 error ("ambiguous default type conversion from %qT",
1241 error (" candidate conversions include %qD and %qD",
1244 return error_mark_node;
1253 tree type = non_reference (TREE_TYPE (TREE_TYPE (winner)));
1254 return build_user_type_conversion (type, expr, LOOKUP_NORMAL);
1260 /* Implements integral promotion (4.1) and float->double promotion. */
1263 type_promotes_to (tree type)
1267 if (type == error_mark_node)
1268 return error_mark_node;
1270 type = TYPE_MAIN_VARIANT (type);
1272 /* Check for promotions of target-defined types first. */
1273 promoted_type = targetm.promoted_type (type);
1275 return promoted_type;
1277 /* bool always promotes to int (not unsigned), even if it's the same
1279 if (type == boolean_type_node)
1280 type = integer_type_node;
1282 /* Normally convert enums to int, but convert wide enums to something
1284 else if (TREE_CODE (type) == ENUMERAL_TYPE
1285 || type == char16_type_node
1286 || type == char32_type_node
1287 || type == wchar_type_node)
1289 int precision = MAX (TYPE_PRECISION (type),
1290 TYPE_PRECISION (integer_type_node));
1291 tree totype = c_common_type_for_size (precision, 0);
1292 if (TYPE_UNSIGNED (type)
1293 && ! int_fits_type_p (TYPE_MAX_VALUE (type), totype))
1294 type = c_common_type_for_size (precision, 1);
1298 else if (c_promoting_integer_type_p (type))
1300 /* Retain unsignedness if really not getting bigger. */
1301 if (TYPE_UNSIGNED (type)
1302 && TYPE_PRECISION (type) == TYPE_PRECISION (integer_type_node))
1303 type = unsigned_type_node;
1305 type = integer_type_node;
1307 else if (type == float_type_node)
1308 type = double_type_node;
1313 /* The routines below this point are carefully written to conform to
1314 the standard. They use the same terminology, and follow the rules
1315 closely. Although they are used only in pt.c at the moment, they
1316 should presumably be used everywhere in the future. */
1318 /* Attempt to perform qualification conversions on EXPR to convert it
1319 to TYPE. Return the resulting expression, or error_mark_node if
1320 the conversion was impossible. */
1323 perform_qualification_conversions (tree type, tree expr)
1327 expr_type = TREE_TYPE (expr);
1329 if (same_type_p (type, expr_type))
1331 else if (TYPE_PTR_P (type) && TYPE_PTR_P (expr_type)
1332 && comp_ptr_ttypes (TREE_TYPE (type), TREE_TYPE (expr_type)))
1333 return build_nop (type, expr);
1334 else if (TYPE_PTR_TO_MEMBER_P (type)
1335 && TYPE_PTR_TO_MEMBER_P (expr_type)
1336 && same_type_p (TYPE_PTRMEM_CLASS_TYPE (type),
1337 TYPE_PTRMEM_CLASS_TYPE (expr_type))
1338 && comp_ptr_ttypes (TYPE_PTRMEM_POINTED_TO_TYPE (type),
1339 TYPE_PTRMEM_POINTED_TO_TYPE (expr_type)))
1340 return build_nop (type, expr);
1342 return error_mark_node;