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)
510 && TREE_CODE (TREE_TYPE (val)) == REFERENCE_TYPE)
512 tree t = TREE_TYPE (TREE_TYPE (val));
513 tree ref = build1 (INDIRECT_REF, t, val);
515 /* We *must* set TREE_READONLY when dereferencing a pointer to const,
516 so that we get the proper error message if the result is used
517 to assign to. Also, &* is supposed to be a no-op. */
518 TREE_READONLY (ref) = CP_TYPE_CONST_P (t);
519 TREE_THIS_VOLATILE (ref) = CP_TYPE_VOLATILE_P (t);
520 TREE_SIDE_EFFECTS (ref)
521 = (TREE_THIS_VOLATILE (ref) || TREE_SIDE_EFFECTS (val));
522 REFERENCE_REF_P (ref) = 1;
529 /* Really perform an lvalue-to-rvalue conversion, including copying an
530 argument of class type into a temporary. */
533 force_rvalue (tree expr)
535 if (MAYBE_CLASS_TYPE_P (TREE_TYPE (expr)) && TREE_CODE (expr) != TARGET_EXPR)
536 expr = ocp_convert (TREE_TYPE (expr), expr,
537 CONV_IMPLICIT|CONV_FORCE_TEMP, LOOKUP_NORMAL);
539 expr = decay_conversion (expr);
545 /* Fold away simple conversions, but make sure the result is an rvalue. */
548 cp_fold_convert (tree type, tree expr)
550 return rvalue (fold_convert (type, expr));
553 /* C++ conversions, preference to static cast conversions. */
556 cp_convert (tree type, tree expr)
558 return ocp_convert (type, expr, CONV_OLD_CONVERT, LOOKUP_NORMAL);
561 /* C++ equivalent of convert_and_check but using cp_convert as the
564 Convert EXPR to TYPE, warning about conversion problems with constants.
565 Invoke this function on every expression that is converted implicitly,
566 i.e. because of language rules and not because of an explicit cast. */
569 cp_convert_and_check (tree type, tree expr)
573 if (TREE_TYPE (expr) == type)
576 result = cp_convert (type, expr);
578 if (c_inhibit_evaluation_warnings == 0
579 && !TREE_OVERFLOW_P (expr)
580 && result != error_mark_node)
581 warnings_for_convert_and_check (type, expr, result);
588 FLAGS indicates how we should behave. */
591 ocp_convert (tree type, tree expr, int convtype, int flags)
594 enum tree_code code = TREE_CODE (type);
595 const char *invalid_conv_diag;
598 if (error_operand_p (e) || type == error_mark_node)
599 return error_mark_node;
601 complete_type (type);
602 complete_type (TREE_TYPE (expr));
604 if ((invalid_conv_diag
605 = targetm.invalid_conversion (TREE_TYPE (expr), type)))
607 error (invalid_conv_diag);
608 return error_mark_node;
611 e = integral_constant_value (e);
613 if (MAYBE_CLASS_TYPE_P (type) && (convtype & CONV_FORCE_TEMP))
614 /* We need a new temporary; don't take this shortcut. */;
615 else if (same_type_ignoring_top_level_qualifiers_p (type, TREE_TYPE (e)))
617 if (same_type_p (type, TREE_TYPE (e)))
618 /* The call to fold will not always remove the NOP_EXPR as
619 might be expected, since if one of the types is a typedef;
620 the comparison in fold is just equality of pointers, not a
621 call to comptypes. We don't call fold in this case because
622 that can result in infinite recursion; fold will call
623 convert, which will call ocp_convert, etc. */
625 /* For complex data types, we need to perform componentwise
627 else if (TREE_CODE (type) == COMPLEX_TYPE)
628 return fold_if_not_in_template (convert_to_complex (type, e));
629 else if (TREE_CODE (e) == TARGET_EXPR)
631 /* Don't build a NOP_EXPR of class type. Instead, change the
632 type of the temporary. */
633 TREE_TYPE (e) = TREE_TYPE (TARGET_EXPR_SLOT (e)) = type;
638 /* We shouldn't be treating objects of ADDRESSABLE type as
640 gcc_assert (!TREE_ADDRESSABLE (type));
641 return fold_if_not_in_template (build_nop (type, e));
645 e1 = targetm.convert_to_type (type, e);
649 if (code == VOID_TYPE && (convtype & CONV_STATIC))
651 e = convert_to_void (e, /*implicit=*/NULL, tf_warning_or_error);
655 if (INTEGRAL_CODE_P (code))
657 tree intype = TREE_TYPE (e);
659 if (TREE_CODE (type) == ENUMERAL_TYPE)
661 /* enum = enum, enum = int, enum = float, (enum)pointer are all
663 if (((INTEGRAL_OR_ENUMERATION_TYPE_P (intype)
664 || TREE_CODE (intype) == REAL_TYPE)
665 && ! (convtype & CONV_STATIC))
666 || TREE_CODE (intype) == POINTER_TYPE)
668 if (flags & LOOKUP_COMPLAIN)
669 permerror (input_location, "conversion from %q#T to %q#T", intype, type);
671 if (!flag_permissive)
672 return error_mark_node;
675 /* [expr.static.cast]
677 8. A value of integral or enumeration type can be explicitly
678 converted to an enumeration type. The value is unchanged if
679 the original value is within the range of the enumeration
680 values. Otherwise, the resulting enumeration value is
682 if (TREE_CODE (expr) == INTEGER_CST && !int_fits_type_p (expr, type))
683 warning (OPT_Wconversion,
684 "the result of the conversion is unspecified because "
685 "%qE is outside the range of type %qT",
688 if (MAYBE_CLASS_TYPE_P (intype))
691 rval = build_type_conversion (type, e);
694 if (flags & LOOKUP_COMPLAIN)
695 error ("%q#T used where a %qT was expected", intype, type);
696 return error_mark_node;
698 if (code == BOOLEAN_TYPE)
699 return cp_truthvalue_conversion (e);
701 return fold_if_not_in_template (convert_to_integer (type, e));
703 if (POINTER_TYPE_P (type) || TYPE_PTR_TO_MEMBER_P (type))
704 return fold_if_not_in_template (cp_convert_to_pointer (type, e));
705 if (code == VECTOR_TYPE)
707 tree in_vtype = TREE_TYPE (e);
708 if (MAYBE_CLASS_TYPE_P (in_vtype))
711 ret_val = build_type_conversion (type, e);
714 if (flags & LOOKUP_COMPLAIN)
715 error ("%q#T used where a %qT was expected", in_vtype, type);
716 return error_mark_node;
718 return fold_if_not_in_template (convert_to_vector (type, e));
720 if (code == REAL_TYPE || code == COMPLEX_TYPE)
722 if (MAYBE_CLASS_TYPE_P (TREE_TYPE (e)))
725 rval = build_type_conversion (type, e);
729 if (flags & LOOKUP_COMPLAIN)
730 error ("%q#T used where a floating point value was expected",
733 if (code == REAL_TYPE)
734 return fold_if_not_in_template (convert_to_real (type, e));
735 else if (code == COMPLEX_TYPE)
736 return fold_if_not_in_template (convert_to_complex (type, e));
739 /* New C++ semantics: since assignment is now based on
740 memberwise copying, if the rhs type is derived from the
741 lhs type, then we may still do a conversion. */
742 if (RECORD_OR_UNION_CODE_P (code))
744 tree dtype = TREE_TYPE (e);
745 tree ctor = NULL_TREE;
747 dtype = TYPE_MAIN_VARIANT (dtype);
749 /* Conversion between aggregate types. New C++ semantics allow
750 objects of derived type to be cast to objects of base type.
751 Old semantics only allowed this between pointers.
753 There may be some ambiguity between using a constructor
754 vs. using a type conversion operator when both apply. */
758 if (abstract_virtuals_error (NULL_TREE, type))
759 return error_mark_node;
761 if (BRACE_ENCLOSED_INITIALIZER_P (ctor))
762 ctor = perform_implicit_conversion (type, ctor, tf_warning_or_error);
763 else if ((flags & LOOKUP_ONLYCONVERTING)
764 && ! (CLASS_TYPE_P (dtype) && DERIVED_FROM_P (type, dtype)))
765 /* For copy-initialization, first we create a temp of the proper type
766 with a user-defined conversion sequence, then we direct-initialize
767 the target with the temp (see [dcl.init]). */
768 ctor = build_user_type_conversion (type, ctor, flags);
771 VEC(tree,gc) *ctor_vec = make_tree_vector_single (ctor);
772 ctor = build_special_member_call (NULL_TREE,
773 complete_ctor_identifier,
776 tf_warning_or_error);
777 release_tree_vector (ctor_vec);
780 return build_cplus_new (type, ctor);
783 if (flags & LOOKUP_COMPLAIN)
785 /* If the conversion failed and expr was an invalid use of pointer to
786 member function, try to report a meaningful error. */
787 if (invalid_nonstatic_memfn_p (expr, tf_warning_or_error))
788 /* We displayed the error message. */;
790 error ("conversion from %qT to non-scalar type %qT requested",
791 TREE_TYPE (expr), type);
793 return error_mark_node;
796 /* When an expression is used in a void context, its value is discarded and
797 no lvalue-rvalue and similar conversions happen [expr.static.cast/4,
798 stmt.expr/1, expr.comma/1]. This permits dereferencing an incomplete type
799 in a void context. The C++ standard does not define what an `access' to an
800 object is, but there is reason to believe that it is the lvalue to rvalue
801 conversion -- if it were not, `*&*p = 1' would violate [expr]/4 in that it
802 accesses `*p' not to calculate the value to be stored. But, dcl.type.cv/8
803 indicates that volatile semantics should be the same between C and C++
804 where ever possible. C leaves it implementation defined as to what
805 constitutes an access to a volatile. So, we interpret `*vp' as a read of
806 the volatile object `vp' points to, unless that is an incomplete type. For
807 volatile references we do not do this interpretation, because that would
808 make it impossible to ignore the reference return value from functions. We
809 issue warnings in the confusing cases.
811 IMPLICIT is non-NULL iff an expression is being implicitly converted; it
812 is NULL when the user is explicitly converting an expression to void via
813 a cast. When non-NULL, IMPLICIT is a string indicating the context of
814 the implicit conversion. */
817 convert_to_void (tree expr, const char *implicit, tsubst_flags_t complain)
819 if (expr == error_mark_node
820 || TREE_TYPE (expr) == error_mark_node)
821 return error_mark_node;
822 if (!TREE_TYPE (expr))
824 if (invalid_nonstatic_memfn_p (expr, complain))
825 return error_mark_node;
826 if (TREE_CODE (expr) == PSEUDO_DTOR_EXPR)
828 if (complain & tf_error)
829 error ("pseudo-destructor is not called");
830 return error_mark_node;
832 if (VOID_TYPE_P (TREE_TYPE (expr)))
834 switch (TREE_CODE (expr))
838 /* The two parts of a cond expr might be separate lvalues. */
839 tree op1 = TREE_OPERAND (expr,1);
840 tree op2 = TREE_OPERAND (expr,2);
841 bool side_effects = TREE_SIDE_EFFECTS (op1) || TREE_SIDE_EFFECTS (op2);
842 tree new_op1 = convert_to_void
843 (op1, (implicit && !side_effects
844 ? "second operand of conditional" : NULL), complain);
845 tree new_op2 = convert_to_void
846 (op2, (implicit && !side_effects
847 ? "third operand of conditional" : NULL), complain);
849 expr = build3 (COND_EXPR, TREE_TYPE (new_op1),
850 TREE_OPERAND (expr, 0), new_op1, new_op2);
856 /* The second part of a compound expr contains the value. */
857 tree op1 = TREE_OPERAND (expr,1);
858 tree new_op1 = convert_to_void
859 (op1, (implicit && !TREE_NO_WARNING (expr)
860 ? "right-hand operand of comma" : NULL), complain);
864 tree t = build2 (COMPOUND_EXPR, TREE_TYPE (new_op1),
865 TREE_OPERAND (expr, 0), new_op1);
872 case NON_LVALUE_EXPR:
874 /* These have already decayed to rvalue. */
877 case CALL_EXPR: /* We have a special meaning for volatile void fn(). */
882 tree type = TREE_TYPE (expr);
883 int is_reference = TREE_CODE (TREE_TYPE (TREE_OPERAND (expr, 0)))
885 int is_volatile = TYPE_VOLATILE (type);
886 int is_complete = COMPLETE_TYPE_P (complete_type (type));
888 /* Can't load the value if we don't know the type. */
889 if (is_volatile && !is_complete)
891 if (complain & tf_warning)
892 warning (0, "object of incomplete type %qT will not be accessed in %s",
893 type, implicit ? implicit : "void context");
895 /* Don't load the value if this is an implicit dereference, or if
896 the type needs to be handled by ctors/dtors. */
897 else if (is_volatile && (is_reference || TREE_ADDRESSABLE (type)))
899 if (complain & tf_warning)
900 warning (0, "object of type %qT will not be accessed in %s",
901 TREE_TYPE (TREE_OPERAND (expr, 0)),
902 implicit ? implicit : "void context");
904 if (is_reference || !is_volatile || !is_complete || TREE_ADDRESSABLE (type))
906 /* Emit a warning (if enabled) when the "effect-less" INDIRECT_REF
907 operation is stripped off. Note that we don't warn about
908 - an expression with TREE_NO_WARNING set. (For an example of
909 such expressions, see build_over_call in call.c.)
910 - automatic dereferencing of references, since the user cannot
911 control it. (See also warn_if_unused_value() in stmt.c.) */
912 if (warn_unused_value
914 && (complain & tf_warning)
915 && !TREE_NO_WARNING (expr)
917 warning (OPT_Wunused_value, "value computed is not used");
918 expr = TREE_OPERAND (expr, 0);
926 /* External variables might be incomplete. */
927 tree type = TREE_TYPE (expr);
928 int is_complete = COMPLETE_TYPE_P (complete_type (type));
930 if (TYPE_VOLATILE (type) && !is_complete && (complain & tf_warning))
931 warning (0, "object %qE of incomplete type %qT will not be accessed in %s",
932 expr, type, implicit ? implicit : "void context");
937 /* Don't bother with the temporary object returned from a function if
938 we don't use it and don't need to destroy it. We'll still
939 allocate space for it in expand_call or declare_return_variable,
940 but we don't need to track it through all the tree phases. */
941 if (TARGET_EXPR_IMPLICIT_P (expr)
942 && TYPE_HAS_TRIVIAL_DESTRUCTOR (TREE_TYPE (expr)))
944 tree init = TARGET_EXPR_INITIAL (expr);
945 if (TREE_CODE (init) == AGGR_INIT_EXPR
946 && !AGGR_INIT_VIA_CTOR_P (init))
948 tree fn = AGGR_INIT_EXPR_FN (init);
949 expr = build_call_array_loc (input_location,
950 TREE_TYPE (TREE_TYPE (TREE_TYPE (fn))),
952 aggr_init_expr_nargs (init),
953 AGGR_INIT_EXPR_ARGP (init));
960 expr = resolve_nondeduced_context (expr);
964 if (TREE_CODE (probe) == ADDR_EXPR)
965 probe = TREE_OPERAND (expr, 0);
966 if (type_unknown_p (probe))
968 /* [over.over] enumerates the places where we can take the address
969 of an overloaded function, and this is not one of them. */
970 if (complain & tf_error)
971 error ("%s cannot resolve address of overloaded function",
972 implicit ? implicit : "void cast");
974 return error_mark_node;
975 expr = void_zero_node;
977 else if (implicit && probe == expr && is_overloaded_fn (probe))
979 /* Only warn when there is no &. */
980 if (complain & tf_warning)
981 warning (OPT_Waddress, "%s is a reference, not call, to function %qE",
983 if (TREE_CODE (expr) == COMPONENT_REF)
984 expr = TREE_OPERAND (expr, 0);
988 if (expr != error_mark_node && !VOID_TYPE_P (TREE_TYPE (expr)))
992 && !TREE_NO_WARNING (expr)
993 && !processing_template_decl)
995 /* The middle end does not warn about expressions that have
996 been explicitly cast to void, so we must do so here. */
997 if (!TREE_SIDE_EFFECTS (expr)) {
998 if (complain & tf_warning)
999 warning (OPT_Wunused_value, "%s has no effect", implicit);
1004 enum tree_code code;
1005 enum tree_code_class tclass;
1008 /* We might like to warn about (say) "(int) f()", as the
1009 cast has no effect, but the compiler itself will
1010 generate implicit conversions under some
1011 circumstances. (For example a block copy will be
1012 turned into a call to "__builtin_memcpy", with a
1013 conversion of the return value to an appropriate
1014 type.) So, to avoid false positives, we strip
1015 conversions. Do not use STRIP_NOPs because it will
1016 not strip conversions to "void", as that is not a
1017 mode-preserving conversion. */
1018 while (TREE_CODE (e) == NOP_EXPR)
1019 e = TREE_OPERAND (e, 0);
1021 code = TREE_CODE (e);
1022 tclass = TREE_CODE_CLASS (code);
1023 if ((tclass == tcc_comparison
1024 || tclass == tcc_unary
1025 || (tclass == tcc_binary
1026 && !(code == MODIFY_EXPR
1027 || code == INIT_EXPR
1028 || code == PREDECREMENT_EXPR
1029 || code == PREINCREMENT_EXPR
1030 || code == POSTDECREMENT_EXPR
1031 || code == POSTINCREMENT_EXPR)))
1032 && (complain & tf_warning))
1033 warning (OPT_Wunused_value, "value computed is not used");
1036 expr = build1 (CONVERT_EXPR, void_type_node, expr);
1038 if (! TREE_SIDE_EFFECTS (expr))
1039 expr = void_zero_node;
1043 /* Create an expression whose value is that of EXPR,
1044 converted to type TYPE. The TREE_TYPE of the value
1045 is always TYPE. This function implements all reasonable
1046 conversions; callers should filter out those that are
1047 not permitted by the language being compiled.
1049 Most of this routine is from build_reinterpret_cast.
1051 The back end cannot call cp_convert (what was convert) because
1052 conversions to/from basetypes may involve memory references
1053 (vbases) and adding or subtracting small values (multiple
1054 inheritance), but it calls convert from the constant folding code
1055 on subtrees of already built trees after it has ripped them apart.
1057 Also, if we ever support range variables, we'll probably also have to
1058 do a little bit more work. */
1061 convert (tree type, tree expr)
1065 if (type == error_mark_node || expr == error_mark_node)
1066 return error_mark_node;
1068 intype = TREE_TYPE (expr);
1070 if (POINTER_TYPE_P (type) && POINTER_TYPE_P (intype))
1071 return fold_if_not_in_template (build_nop (type, expr));
1073 return ocp_convert (type, expr, CONV_OLD_CONVERT,
1074 LOOKUP_NORMAL|LOOKUP_NO_CONVERSION);
1077 /* Like cp_convert, except permit conversions to take place which
1078 are not normally allowed due to access restrictions
1079 (such as conversion from sub-type to private super-type). */
1082 convert_force (tree type, tree expr, int convtype)
1085 enum tree_code code = TREE_CODE (type);
1087 if (code == REFERENCE_TYPE)
1088 return (fold_if_not_in_template
1089 (convert_to_reference (type, e, CONV_C_CAST, LOOKUP_COMPLAIN,
1092 if (code == POINTER_TYPE)
1093 return fold_if_not_in_template (convert_to_pointer_force (type, e));
1095 /* From typeck.c convert_for_assignment */
1096 if (((TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE && TREE_CODE (e) == ADDR_EXPR
1097 && TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE
1098 && TREE_CODE (TREE_TYPE (TREE_TYPE (e))) == METHOD_TYPE)
1099 || integer_zerop (e)
1100 || TYPE_PTRMEMFUNC_P (TREE_TYPE (e)))
1101 && TYPE_PTRMEMFUNC_P (type))
1102 /* compatible pointer to member functions. */
1103 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), e, 1,
1106 return ocp_convert (type, e, CONV_C_CAST|convtype, LOOKUP_NORMAL);
1109 /* Convert an aggregate EXPR to type XTYPE. If a conversion
1110 exists, return the attempted conversion. This may
1111 return ERROR_MARK_NODE if the conversion is not
1112 allowed (references private members, etc).
1113 If no conversion exists, NULL_TREE is returned.
1115 FIXME: Ambiguity checking is wrong. Should choose one by the implicit
1116 object parameter, or by the second standard conversion sequence if
1117 that doesn't do it. This will probably wait for an overloading rewrite.
1121 build_type_conversion (tree xtype, tree expr)
1123 /* C++: check to see if we can convert this aggregate type
1124 into the required type. */
1125 return build_user_type_conversion (xtype, expr, LOOKUP_NORMAL);
1128 /* Convert the given EXPR to one of a group of types suitable for use in an
1129 expression. DESIRES is a combination of various WANT_* flags (q.v.)
1130 which indicates which types are suitable. If COMPLAIN is true, complain
1131 about ambiguity; otherwise, the caller will deal with it. */
1134 build_expr_type_conversion (int desires, tree expr, bool complain)
1136 tree basetype = TREE_TYPE (expr);
1137 tree conv = NULL_TREE;
1138 tree winner = NULL_TREE;
1140 if (expr == null_node
1141 && (desires & WANT_INT)
1142 && !(desires & WANT_NULL))
1143 warning (OPT_Wconversion, "converting NULL to non-pointer type");
1145 basetype = TREE_TYPE (expr);
1147 if (basetype == error_mark_node)
1148 return error_mark_node;
1150 if (! MAYBE_CLASS_TYPE_P (basetype))
1151 switch (TREE_CODE (basetype))
1154 if ((desires & WANT_NULL) && null_ptr_cst_p (expr))
1156 /* else fall through... */
1159 return (desires & WANT_INT) ? expr : NULL_TREE;
1161 return (desires & WANT_ENUM) ? expr : NULL_TREE;
1163 return (desires & WANT_FLOAT) ? expr : NULL_TREE;
1165 return (desires & WANT_POINTER) ? expr : NULL_TREE;
1169 return (desires & WANT_POINTER) ? decay_conversion (expr)
1173 if ((desires & WANT_VECTOR) == 0)
1175 switch (TREE_CODE (TREE_TYPE (basetype)))
1179 return (desires & WANT_INT) ? expr : NULL_TREE;
1181 return (desires & WANT_ENUM) ? expr : NULL_TREE;
1183 return (desires & WANT_FLOAT) ? expr : NULL_TREE;
1192 /* The code for conversions from class type is currently only used for
1193 delete expressions. Other expressions are handled by build_new_op. */
1194 if (!complete_type_or_else (basetype, expr))
1195 return error_mark_node;
1196 if (!TYPE_HAS_CONVERSION (basetype))
1199 for (conv = lookup_conversions (basetype, /*lookup_template_convs_p=*/true);
1201 conv = TREE_CHAIN (conv))
1205 tree cand = TREE_VALUE (conv);
1206 cand = OVL_CURRENT (cand);
1208 if (winner && winner == cand)
1211 if (DECL_NONCONVERTING_P (cand))
1214 candidate = non_reference (TREE_TYPE (TREE_TYPE (cand)));
1216 switch (TREE_CODE (candidate))
1220 win = (desires & WANT_INT); break;
1222 win = (desires & WANT_ENUM); break;
1224 win = (desires & WANT_FLOAT); break;
1226 win = (desires & WANT_POINTER); break;
1229 if ((desires & WANT_VECTOR) == 0)
1231 switch (TREE_CODE (TREE_TYPE (candidate)))
1235 win = (desires & WANT_INT); break;
1237 win = (desires & WANT_ENUM); break;
1239 win = (desires & WANT_FLOAT); break;
1255 error ("ambiguous default type conversion from %qT",
1257 error (" candidate conversions include %qD and %qD",
1260 return error_mark_node;
1269 tree type = non_reference (TREE_TYPE (TREE_TYPE (winner)));
1270 return build_user_type_conversion (type, expr, LOOKUP_NORMAL);
1276 /* Implements integral promotion (4.1) and float->double promotion. */
1279 type_promotes_to (tree type)
1283 if (type == error_mark_node)
1284 return error_mark_node;
1286 type = TYPE_MAIN_VARIANT (type);
1288 /* Check for promotions of target-defined types first. */
1289 promoted_type = targetm.promoted_type (type);
1291 return promoted_type;
1293 /* bool always promotes to int (not unsigned), even if it's the same
1295 if (TREE_CODE (type) == BOOLEAN_TYPE)
1296 type = integer_type_node;
1298 /* Normally convert enums to int, but convert wide enums to something
1300 else if (TREE_CODE (type) == ENUMERAL_TYPE
1301 || type == char16_type_node
1302 || type == char32_type_node
1303 || type == wchar_type_node)
1305 int precision = MAX (TYPE_PRECISION (type),
1306 TYPE_PRECISION (integer_type_node));
1307 tree totype = c_common_type_for_size (precision, 0);
1308 if (TYPE_UNSIGNED (type)
1309 && ! int_fits_type_p (TYPE_MAX_VALUE (type), totype))
1310 type = c_common_type_for_size (precision, 1);
1314 else if (c_promoting_integer_type_p (type))
1316 /* Retain unsignedness if really not getting bigger. */
1317 if (TYPE_UNSIGNED (type)
1318 && TYPE_PRECISION (type) == TYPE_PRECISION (integer_type_node))
1319 type = unsigned_type_node;
1321 type = integer_type_node;
1323 else if (type == float_type_node)
1324 type = double_type_node;
1329 /* The routines below this point are carefully written to conform to
1330 the standard. They use the same terminology, and follow the rules
1331 closely. Although they are used only in pt.c at the moment, they
1332 should presumably be used everywhere in the future. */
1334 /* Attempt to perform qualification conversions on EXPR to convert it
1335 to TYPE. Return the resulting expression, or error_mark_node if
1336 the conversion was impossible. */
1339 perform_qualification_conversions (tree type, tree expr)
1343 expr_type = TREE_TYPE (expr);
1345 if (same_type_p (type, expr_type))
1347 else if (TYPE_PTR_P (type) && TYPE_PTR_P (expr_type)
1348 && comp_ptr_ttypes (TREE_TYPE (type), TREE_TYPE (expr_type)))
1349 return build_nop (type, expr);
1350 else if (TYPE_PTR_TO_MEMBER_P (type)
1351 && TYPE_PTR_TO_MEMBER_P (expr_type)
1352 && same_type_p (TYPE_PTRMEM_CLASS_TYPE (type),
1353 TYPE_PTRMEM_CLASS_TYPE (expr_type))
1354 && comp_ptr_ttypes (TYPE_PTRMEM_POINTED_TO_TYPE (type),
1355 TYPE_PTRMEM_POINTED_TO_TYPE (expr_type)))
1356 return build_nop (type, expr);
1358 return error_mark_node;