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, 2010
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"
42 static tree cp_convert_to_pointer (tree, tree);
43 static tree convert_to_pointer_force (tree, tree);
44 static tree build_type_conversion (tree, tree);
45 static tree build_up_reference (tree, tree, int, tree);
46 static void warn_ref_binding (tree, tree, tree);
48 /* Change of width--truncation and extension of integers or reals--
49 is represented with NOP_EXPR. Proper functioning of many things
50 assumes that no other conversions can be NOP_EXPRs.
52 Conversion between integer and pointer is represented with CONVERT_EXPR.
53 Converting integer to real uses FLOAT_EXPR
54 and real to integer uses FIX_TRUNC_EXPR.
56 Here is a list of all the functions that assume that widening and
57 narrowing is always done with a NOP_EXPR:
58 In convert.c, convert_to_integer.
59 In c-typeck.c, build_binary_op_nodefault (boolean ops),
60 and c_common_truthvalue_conversion.
61 In expr.c: expand_expr, for operands of a MULT_EXPR.
62 In fold-const.c: fold.
63 In tree.c: get_narrower and get_unwidened.
65 C++: in multiple-inheritance, converting between pointers may involve
66 adjusting them by a delta stored within the class definition. */
68 /* Subroutines of `convert'. */
70 /* if converting pointer to pointer
71 if dealing with classes, check for derived->base or vice versa
72 else if dealing with method pointers, delegate
74 else if converting class, pass off to build_type_conversion
75 else try C-style pointer conversion. */
78 cp_convert_to_pointer (tree type, tree expr)
80 tree intype = TREE_TYPE (expr);
83 if (intype == error_mark_node)
84 return error_mark_node;
86 if (MAYBE_CLASS_TYPE_P (intype))
88 intype = complete_type (intype);
89 if (!COMPLETE_TYPE_P (intype))
91 error ("can't convert from incomplete type %qT to %qT",
93 return error_mark_node;
96 rval = build_type_conversion (type, expr);
99 if (rval == error_mark_node)
100 error ("conversion of %qE from %qT to %qT is ambiguous",
106 /* Handle anachronistic conversions from (::*)() to cv void* or (*)(). */
107 if (TREE_CODE (type) == POINTER_TYPE
108 && (TREE_CODE (TREE_TYPE (type)) == FUNCTION_TYPE
109 || VOID_TYPE_P (TREE_TYPE (type))))
111 if (TYPE_PTRMEMFUNC_P (intype)
112 || TREE_CODE (intype) == METHOD_TYPE)
113 return convert_member_func_to_ptr (type, expr);
114 if (TREE_CODE (TREE_TYPE (expr)) == POINTER_TYPE)
115 return build_nop (type, expr);
116 intype = TREE_TYPE (expr);
119 if (expr == error_mark_node)
120 return error_mark_node;
122 form = TREE_CODE (intype);
124 if (POINTER_TYPE_P (intype))
126 intype = TYPE_MAIN_VARIANT (intype);
128 if (TYPE_MAIN_VARIANT (type) != intype
129 && TREE_CODE (type) == POINTER_TYPE
130 && TREE_CODE (TREE_TYPE (type)) == RECORD_TYPE
131 && MAYBE_CLASS_TYPE_P (TREE_TYPE (type))
132 && MAYBE_CLASS_TYPE_P (TREE_TYPE (intype))
133 && TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE)
135 enum tree_code code = PLUS_EXPR;
141 intype_class = TREE_TYPE (intype);
142 type_class = TREE_TYPE (type);
144 same_p = same_type_p (TYPE_MAIN_VARIANT (intype_class),
145 TYPE_MAIN_VARIANT (type_class));
147 /* Try derived to base conversion. */
149 binfo = lookup_base (intype_class, type_class, ba_check, NULL);
150 if (!same_p && !binfo)
152 /* Try base to derived conversion. */
153 binfo = lookup_base (type_class, intype_class, ba_check, NULL);
156 if (binfo == error_mark_node)
157 return error_mark_node;
161 expr = build_base_path (code, expr, binfo, 0);
162 /* Add any qualifier conversions. */
163 return build_nop (type, expr);
167 if (TYPE_PTRMEMFUNC_P (type))
169 error ("cannot convert %qE from type %qT to type %qT",
171 return error_mark_node;
174 return build_nop (type, expr);
176 else if ((TYPE_PTRMEM_P (type) && TYPE_PTRMEM_P (intype))
177 || (TYPE_PTRMEMFUNC_P (type) && TYPE_PTRMEMFUNC_P (intype)))
178 return convert_ptrmem (type, expr, /*allow_inverse_p=*/false,
180 else if (TYPE_PTRMEMFUNC_P (intype))
184 if (TREE_CODE (expr) == PTRMEM_CST)
185 return cp_convert_to_pointer (type,
186 PTRMEM_CST_MEMBER (expr));
187 else if (TREE_CODE (expr) == OFFSET_REF)
189 tree object = TREE_OPERAND (expr, 0);
190 return get_member_function_from_ptrfunc (&object,
191 TREE_OPERAND (expr, 1));
194 error ("cannot convert %qE from type %qT to type %qT",
196 return error_mark_node;
199 if (integer_zerop (expr))
201 if (TYPE_PTRMEMFUNC_P (type))
202 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), expr, 0,
205 if (TYPE_PTRMEM_P (type))
207 /* A NULL pointer-to-member is represented by -1, not by
209 expr = build_int_cst_type (type, -1);
212 expr = build_int_cst (type, 0);
216 else if (TYPE_PTR_TO_MEMBER_P (type) && INTEGRAL_CODE_P (form))
218 error ("invalid conversion from %qT to %qT", intype, type);
219 return error_mark_node;
222 if (INTEGRAL_CODE_P (form))
224 if (TYPE_PRECISION (intype) == POINTER_SIZE)
225 return build1 (CONVERT_EXPR, type, expr);
226 expr = cp_convert (c_common_type_for_size (POINTER_SIZE, 0), expr);
227 /* Modes may be different but sizes should be the same. There
228 is supposed to be some integral type that is the same width
230 gcc_assert (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (expr)))
231 == GET_MODE_SIZE (TYPE_MODE (type)));
233 return convert_to_pointer (type, expr);
236 if (type_unknown_p (expr))
237 return instantiate_type (type, expr, tf_warning_or_error);
239 error ("cannot convert %qE from type %qT to type %qT",
241 return error_mark_node;
244 /* Like convert, except permit conversions to take place which
245 are not normally allowed due to access restrictions
246 (such as conversion from sub-type to private super-type). */
249 convert_to_pointer_force (tree type, tree expr)
251 tree intype = TREE_TYPE (expr);
252 enum tree_code form = TREE_CODE (intype);
254 if (form == POINTER_TYPE)
256 intype = TYPE_MAIN_VARIANT (intype);
258 if (TYPE_MAIN_VARIANT (type) != intype
259 && TREE_CODE (TREE_TYPE (type)) == RECORD_TYPE
260 && MAYBE_CLASS_TYPE_P (TREE_TYPE (type))
261 && MAYBE_CLASS_TYPE_P (TREE_TYPE (intype))
262 && TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE)
264 enum tree_code code = PLUS_EXPR;
267 binfo = lookup_base (TREE_TYPE (intype), TREE_TYPE (type),
271 binfo = lookup_base (TREE_TYPE (type), TREE_TYPE (intype),
275 if (binfo == error_mark_node)
276 return error_mark_node;
279 expr = build_base_path (code, expr, binfo, 0);
280 if (expr == error_mark_node)
281 return error_mark_node;
282 /* Add any qualifier conversions. */
283 if (!same_type_p (TREE_TYPE (TREE_TYPE (expr)),
285 expr = build_nop (type, expr);
291 return cp_convert_to_pointer (type, expr);
294 /* We are passing something to a function which requires a reference.
295 The type we are interested in is in TYPE. The initial
296 value we have to begin with is in ARG.
298 FLAGS controls how we manage access checking.
299 DIRECT_BIND in FLAGS controls how any temporaries are generated.
300 If DIRECT_BIND is set, DECL is the reference we're binding to. */
303 build_up_reference (tree type, tree arg, int flags, tree decl)
306 tree argtype = TREE_TYPE (arg);
307 tree target_type = TREE_TYPE (type);
309 gcc_assert (TREE_CODE (type) == REFERENCE_TYPE);
311 if ((flags & DIRECT_BIND) && ! real_lvalue_p (arg))
313 /* Create a new temporary variable. We can't just use a TARGET_EXPR
314 here because it needs to live as long as DECL. */
317 arg = make_temporary_var_for_ref_to_temp (decl, TREE_TYPE (arg));
319 /* Process the initializer for the declaration. */
320 DECL_INITIAL (arg) = targ;
321 cp_finish_decl (arg, targ, /*init_const_expr_p=*/false, NULL_TREE,
322 LOOKUP_ONLYCONVERTING|DIRECT_BIND);
324 else if (!(flags & DIRECT_BIND) && ! lvalue_p (arg))
325 return get_target_expr (arg);
327 /* If we had a way to wrap this up, and say, if we ever needed its
328 address, transform all occurrences of the register, into a memory
329 reference we could win better. */
330 rval = cp_build_unary_op (ADDR_EXPR, arg, 1, tf_warning_or_error);
331 if (rval == error_mark_node)
332 return error_mark_node;
334 if ((flags & LOOKUP_PROTECT)
335 && TYPE_MAIN_VARIANT (argtype) != TYPE_MAIN_VARIANT (target_type)
336 && MAYBE_CLASS_TYPE_P (argtype)
337 && MAYBE_CLASS_TYPE_P (target_type))
339 /* We go through lookup_base for the access control. */
340 tree binfo = lookup_base (argtype, target_type, ba_check, NULL);
341 if (binfo == error_mark_node)
342 return error_mark_node;
343 if (binfo == NULL_TREE)
344 return error_not_base_type (target_type, argtype);
345 rval = build_base_path (PLUS_EXPR, rval, binfo, 1);
349 = convert_to_pointer_force (build_pointer_type (target_type), rval);
350 return build_nop (type, rval);
353 /* Subroutine of convert_to_reference. REFTYPE is the target reference type.
354 INTYPE is the original rvalue type and DECL is an optional _DECL node
357 [dcl.init.ref] says that if an rvalue is used to
358 initialize a reference, then the reference must be to a
359 non-volatile const type. */
362 warn_ref_binding (tree reftype, tree intype, tree decl)
364 tree ttl = TREE_TYPE (reftype);
366 if (!CP_TYPE_CONST_NON_VOLATILE_P (ttl))
370 if (CP_TYPE_VOLATILE_P (ttl) && decl)
371 msg = G_("initialization of volatile reference type %q#T from "
372 "rvalue of type %qT");
373 else if (CP_TYPE_VOLATILE_P (ttl))
374 msg = G_("conversion to volatile reference type %q#T "
375 "from rvalue of type %qT");
377 msg = G_("initialization of non-const reference type %q#T from "
378 "rvalue of type %qT");
380 msg = G_("conversion to non-const reference type %q#T from "
381 "rvalue of type %qT");
383 permerror (input_location, msg, reftype, intype);
387 /* For C++: Only need to do one-level references, but cannot
388 get tripped up on signed/unsigned differences.
390 DECL is either NULL_TREE or the _DECL node for a reference that is being
391 initialized. It can be error_mark_node if we don't know the _DECL but
392 we know it's an initialization. */
395 convert_to_reference (tree reftype, tree expr, int convtype,
396 int flags, tree decl)
398 tree type = TYPE_MAIN_VARIANT (TREE_TYPE (reftype));
400 tree rval = NULL_TREE;
401 tree rval_as_conversion = NULL_TREE;
402 bool can_convert_intype_to_type;
404 if (TREE_CODE (type) == FUNCTION_TYPE
405 && TREE_TYPE (expr) == unknown_type_node)
406 expr = instantiate_type (type, expr,
407 (flags & LOOKUP_COMPLAIN)
408 ? tf_warning_or_error : tf_none);
410 if (expr == error_mark_node)
411 return error_mark_node;
413 intype = TREE_TYPE (expr);
415 gcc_assert (TREE_CODE (intype) != REFERENCE_TYPE);
416 gcc_assert (TREE_CODE (reftype) == REFERENCE_TYPE);
418 intype = TYPE_MAIN_VARIANT (intype);
420 can_convert_intype_to_type = can_convert (type, intype);
421 if (!can_convert_intype_to_type
422 && (convtype & CONV_IMPLICIT) && MAYBE_CLASS_TYPE_P (intype)
423 && ! (flags & LOOKUP_NO_CONVERSION))
425 /* Look for a user-defined conversion to lvalue that we can use. */
428 = build_type_conversion (reftype, expr);
430 if (rval_as_conversion && rval_as_conversion != error_mark_node
431 && real_lvalue_p (rval_as_conversion))
433 expr = rval_as_conversion;
434 rval_as_conversion = NULL_TREE;
436 can_convert_intype_to_type = 1;
440 if (((convtype & CONV_STATIC) && can_convert (intype, type))
441 || ((convtype & CONV_IMPLICIT) && can_convert_intype_to_type))
443 if (flags & LOOKUP_COMPLAIN)
445 tree ttl = TREE_TYPE (reftype);
446 tree ttr = lvalue_type (expr);
448 if (! real_lvalue_p (expr))
449 warn_ref_binding (reftype, intype, decl);
451 if (! (convtype & CONV_CONST)
452 && !at_least_as_qualified_p (ttl, ttr))
453 permerror (input_location, "conversion from %qT to %qT discards qualifiers",
457 return build_up_reference (reftype, expr, flags, decl);
459 else if ((convtype & CONV_REINTERPRET) && lvalue_p (expr))
461 /* When casting an lvalue to a reference type, just convert into
462 a pointer to the new type and deference it. This is allowed
463 by San Diego WP section 5.2.9 paragraph 12, though perhaps it
464 should be done directly (jason). (int &)ri ---> *(int*)&ri */
466 /* B* bp; A& ar = (A&)bp; is valid, but it's probably not what they
468 if (TREE_CODE (intype) == POINTER_TYPE
469 && (comptypes (TREE_TYPE (intype), type,
470 COMPARE_BASE | COMPARE_DERIVED)))
471 warning (0, "casting %qT to %qT does not dereference pointer",
474 rval = cp_build_unary_op (ADDR_EXPR, expr, 0, tf_warning_or_error);
475 if (rval != error_mark_node)
476 rval = convert_force (build_pointer_type (TREE_TYPE (reftype)),
478 if (rval != error_mark_node)
479 rval = build1 (NOP_EXPR, reftype, rval);
483 rval = convert_for_initialization (NULL_TREE, type, expr, flags,
485 tf_warning_or_error);
486 if (rval == NULL_TREE || rval == error_mark_node)
488 warn_ref_binding (reftype, intype, decl);
489 rval = build_up_reference (reftype, rval, flags, decl);
494 /* If we found a way to convert earlier, then use it. */
498 if (flags & LOOKUP_COMPLAIN)
499 error ("cannot convert type %qT to type %qT", intype, reftype);
501 return error_mark_node;
504 /* We are using a reference VAL for its value. Bash that reference all the
505 way down to its lowest form. */
508 convert_from_reference (tree val)
511 && TREE_CODE (TREE_TYPE (val)) == REFERENCE_TYPE)
513 tree t = TREE_TYPE (TREE_TYPE (val));
514 tree ref = build1 (INDIRECT_REF, t, val);
516 /* We *must* set TREE_READONLY when dereferencing a pointer to const,
517 so that we get the proper error message if the result is used
518 to assign to. Also, &* is supposed to be a no-op. */
519 TREE_READONLY (ref) = CP_TYPE_CONST_P (t);
520 TREE_THIS_VOLATILE (ref) = CP_TYPE_VOLATILE_P (t);
521 TREE_SIDE_EFFECTS (ref)
522 = (TREE_THIS_VOLATILE (ref) || TREE_SIDE_EFFECTS (val));
523 REFERENCE_REF_P (ref) = 1;
530 /* Really perform an lvalue-to-rvalue conversion, including copying an
531 argument of class type into a temporary. */
534 force_rvalue (tree expr)
536 if (MAYBE_CLASS_TYPE_P (TREE_TYPE (expr)) && TREE_CODE (expr) != TARGET_EXPR)
537 expr = ocp_convert (TREE_TYPE (expr), expr,
538 CONV_IMPLICIT|CONV_FORCE_TEMP, LOOKUP_NORMAL);
540 expr = decay_conversion (expr);
546 /* Fold away simple conversions, but make sure the result is an rvalue. */
549 cp_fold_convert (tree type, tree expr)
551 return rvalue (fold_convert (type, expr));
554 /* C++ conversions, preference to static cast conversions. */
557 cp_convert (tree type, tree expr)
559 return ocp_convert (type, expr, CONV_OLD_CONVERT, LOOKUP_NORMAL);
562 /* C++ equivalent of convert_and_check but using cp_convert as the
565 Convert EXPR to TYPE, warning about conversion problems with constants.
566 Invoke this function on every expression that is converted implicitly,
567 i.e. because of language rules and not because of an explicit cast. */
570 cp_convert_and_check (tree type, tree expr)
574 if (TREE_TYPE (expr) == type)
577 result = cp_convert (type, expr);
579 if (c_inhibit_evaluation_warnings == 0
580 && !TREE_OVERFLOW_P (expr)
581 && result != error_mark_node)
582 warnings_for_convert_and_check (type, expr, result);
589 FLAGS indicates how we should behave. */
592 ocp_convert (tree type, tree expr, int convtype, int flags)
595 enum tree_code code = TREE_CODE (type);
596 const char *invalid_conv_diag;
599 if (error_operand_p (e) || type == error_mark_node)
600 return error_mark_node;
602 complete_type (type);
603 complete_type (TREE_TYPE (expr));
605 if ((invalid_conv_diag
606 = targetm.invalid_conversion (TREE_TYPE (expr), type)))
608 error (invalid_conv_diag);
609 return error_mark_node;
612 e = integral_constant_value (e);
613 if (error_operand_p (e))
614 return error_mark_node;
616 if (MAYBE_CLASS_TYPE_P (type) && (convtype & CONV_FORCE_TEMP))
617 /* We need a new temporary; don't take this shortcut. */;
618 else if (same_type_ignoring_top_level_qualifiers_p (type, TREE_TYPE (e)))
620 if (same_type_p (type, TREE_TYPE (e)))
621 /* The call to fold will not always remove the NOP_EXPR as
622 might be expected, since if one of the types is a typedef;
623 the comparison in fold is just equality of pointers, not a
624 call to comptypes. We don't call fold in this case because
625 that can result in infinite recursion; fold will call
626 convert, which will call ocp_convert, etc. */
628 /* For complex data types, we need to perform componentwise
630 else if (TREE_CODE (type) == COMPLEX_TYPE)
631 return fold_if_not_in_template (convert_to_complex (type, e));
632 else if (TREE_CODE (e) == TARGET_EXPR)
634 /* Don't build a NOP_EXPR of class type. Instead, change the
635 type of the temporary. */
636 TREE_TYPE (e) = TREE_TYPE (TARGET_EXPR_SLOT (e)) = type;
641 /* We shouldn't be treating objects of ADDRESSABLE type as
643 gcc_assert (!TREE_ADDRESSABLE (type));
644 return fold_if_not_in_template (build_nop (type, e));
648 e1 = targetm.convert_to_type (type, e);
652 if (code == VOID_TYPE && (convtype & CONV_STATIC))
654 e = convert_to_void (e, /*implicit=*/NULL, tf_warning_or_error);
658 if (INTEGRAL_CODE_P (code))
660 tree intype = TREE_TYPE (e);
662 if (TREE_CODE (type) == ENUMERAL_TYPE)
664 /* enum = enum, enum = int, enum = float, (enum)pointer are all
666 if (((INTEGRAL_OR_ENUMERATION_TYPE_P (intype)
667 || TREE_CODE (intype) == REAL_TYPE)
668 && ! (convtype & CONV_STATIC))
669 || TREE_CODE (intype) == POINTER_TYPE)
671 if (flags & LOOKUP_COMPLAIN)
672 permerror (input_location, "conversion from %q#T to %q#T", intype, type);
674 if (!flag_permissive)
675 return error_mark_node;
678 /* [expr.static.cast]
680 8. A value of integral or enumeration type can be explicitly
681 converted to an enumeration type. The value is unchanged if
682 the original value is within the range of the enumeration
683 values. Otherwise, the resulting enumeration value is
685 if (TREE_CODE (expr) == INTEGER_CST
686 && !int_fits_type_p (expr, ENUM_UNDERLYING_TYPE (type)))
687 warning (OPT_Wconversion,
688 "the result of the conversion is unspecified because "
689 "%qE is outside the range of type %qT",
692 if (MAYBE_CLASS_TYPE_P (intype))
695 rval = build_type_conversion (type, e);
698 if (flags & LOOKUP_COMPLAIN)
699 error ("%q#T used where a %qT was expected", intype, type);
700 return error_mark_node;
702 if (code == BOOLEAN_TYPE)
703 return cp_truthvalue_conversion (e);
705 return fold_if_not_in_template (convert_to_integer (type, e));
707 if (NULLPTR_TYPE_P (type) && e && null_ptr_cst_p (e))
709 if (POINTER_TYPE_P (type) || TYPE_PTR_TO_MEMBER_P (type))
710 return fold_if_not_in_template (cp_convert_to_pointer (type, e));
711 if (code == VECTOR_TYPE)
713 tree in_vtype = TREE_TYPE (e);
714 if (MAYBE_CLASS_TYPE_P (in_vtype))
717 ret_val = build_type_conversion (type, e);
720 if (flags & LOOKUP_COMPLAIN)
721 error ("%q#T used where a %qT was expected", in_vtype, type);
722 return error_mark_node;
724 return fold_if_not_in_template (convert_to_vector (type, e));
726 if (code == REAL_TYPE || code == COMPLEX_TYPE)
728 if (MAYBE_CLASS_TYPE_P (TREE_TYPE (e)))
731 rval = build_type_conversion (type, e);
735 if (flags & LOOKUP_COMPLAIN)
736 error ("%q#T used where a floating point value was expected",
739 if (code == REAL_TYPE)
740 return fold_if_not_in_template (convert_to_real (type, e));
741 else if (code == COMPLEX_TYPE)
742 return fold_if_not_in_template (convert_to_complex (type, e));
745 /* New C++ semantics: since assignment is now based on
746 memberwise copying, if the rhs type is derived from the
747 lhs type, then we may still do a conversion. */
748 if (RECORD_OR_UNION_CODE_P (code))
750 tree dtype = TREE_TYPE (e);
751 tree ctor = NULL_TREE;
753 dtype = TYPE_MAIN_VARIANT (dtype);
755 /* Conversion between aggregate types. New C++ semantics allow
756 objects of derived type to be cast to objects of base type.
757 Old semantics only allowed this between pointers.
759 There may be some ambiguity between using a constructor
760 vs. using a type conversion operator when both apply. */
764 if (abstract_virtuals_error (NULL_TREE, type))
765 return error_mark_node;
767 if (BRACE_ENCLOSED_INITIALIZER_P (ctor))
768 ctor = perform_implicit_conversion (type, ctor, tf_warning_or_error);
769 else if ((flags & LOOKUP_ONLYCONVERTING)
770 && ! (CLASS_TYPE_P (dtype) && DERIVED_FROM_P (type, dtype)))
771 /* For copy-initialization, first we create a temp of the proper type
772 with a user-defined conversion sequence, then we direct-initialize
773 the target with the temp (see [dcl.init]). */
774 ctor = build_user_type_conversion (type, ctor, flags);
777 VEC(tree,gc) *ctor_vec = make_tree_vector_single (ctor);
778 ctor = build_special_member_call (NULL_TREE,
779 complete_ctor_identifier,
782 tf_warning_or_error);
783 release_tree_vector (ctor_vec);
786 return build_cplus_new (type, ctor);
789 if (flags & LOOKUP_COMPLAIN)
791 /* If the conversion failed and expr was an invalid use of pointer to
792 member function, try to report a meaningful error. */
793 if (invalid_nonstatic_memfn_p (expr, tf_warning_or_error))
794 /* We displayed the error message. */;
796 error ("conversion from %qT to non-scalar type %qT requested",
797 TREE_TYPE (expr), type);
799 return error_mark_node;
802 /* When an expression is used in a void context, its value is discarded and
803 no lvalue-rvalue and similar conversions happen [expr.static.cast/4,
804 stmt.expr/1, expr.comma/1]. This permits dereferencing an incomplete type
805 in a void context. The C++ standard does not define what an `access' to an
806 object is, but there is reason to believe that it is the lvalue to rvalue
807 conversion -- if it were not, `*&*p = 1' would violate [expr]/4 in that it
808 accesses `*p' not to calculate the value to be stored. But, dcl.type.cv/8
809 indicates that volatile semantics should be the same between C and C++
810 where ever possible. C leaves it implementation defined as to what
811 constitutes an access to a volatile. So, we interpret `*vp' as a read of
812 the volatile object `vp' points to, unless that is an incomplete type. For
813 volatile references we do not do this interpretation, because that would
814 make it impossible to ignore the reference return value from functions. We
815 issue warnings in the confusing cases.
817 IMPLICIT is non-NULL iff an expression is being implicitly converted; it
818 is NULL when the user is explicitly converting an expression to void via
819 a cast. When non-NULL, IMPLICIT is a string indicating the context of
820 the implicit conversion. */
823 convert_to_void (tree expr, const char *implicit, tsubst_flags_t complain)
825 if (expr == error_mark_node
826 || TREE_TYPE (expr) == error_mark_node)
827 return error_mark_node;
829 if (implicit == NULL)
830 mark_exp_read (expr);
835 while (TREE_CODE (exprv) == COMPOUND_EXPR)
836 exprv = TREE_OPERAND (exprv, 1);
837 if (DECL_P (exprv) || handled_component_p (exprv))
838 /* Expr is not being 'used' here, otherwise we whould have
839 called mark_{rl}value_use use here, which would have in turn
840 called mark_exp_read. Rather, we call mark_exp_read directly
841 to avoid some warnings when
842 -Wunused-but-set-{variable,parameter} is in effect. */
843 mark_exp_read (exprv);
846 if (!TREE_TYPE (expr))
848 if (invalid_nonstatic_memfn_p (expr, complain))
849 return error_mark_node;
850 if (TREE_CODE (expr) == PSEUDO_DTOR_EXPR)
852 if (complain & tf_error)
853 error ("pseudo-destructor is not called");
854 return error_mark_node;
856 if (VOID_TYPE_P (TREE_TYPE (expr)))
858 switch (TREE_CODE (expr))
862 /* The two parts of a cond expr might be separate lvalues. */
863 tree op1 = TREE_OPERAND (expr,1);
864 tree op2 = TREE_OPERAND (expr,2);
865 bool side_effects = TREE_SIDE_EFFECTS (op1) || TREE_SIDE_EFFECTS (op2);
866 tree new_op1 = convert_to_void
867 (op1, (implicit && !side_effects
868 ? "second operand of conditional" : NULL), complain);
869 tree new_op2 = convert_to_void
870 (op2, (implicit && !side_effects
871 ? "third operand of conditional" : NULL), complain);
873 expr = build3 (COND_EXPR, TREE_TYPE (new_op1),
874 TREE_OPERAND (expr, 0), new_op1, new_op2);
880 /* The second part of a compound expr contains the value. */
881 tree op1 = TREE_OPERAND (expr,1);
882 tree new_op1 = convert_to_void
883 (op1, (implicit && !TREE_NO_WARNING (expr)
884 ? "right-hand operand of comma" : NULL), complain);
888 tree t = build2 (COMPOUND_EXPR, TREE_TYPE (new_op1),
889 TREE_OPERAND (expr, 0), new_op1);
896 case NON_LVALUE_EXPR:
898 /* These have already decayed to rvalue. */
901 case CALL_EXPR: /* We have a special meaning for volatile void fn(). */
906 tree type = TREE_TYPE (expr);
907 int is_reference = TREE_CODE (TREE_TYPE (TREE_OPERAND (expr, 0)))
909 int is_volatile = TYPE_VOLATILE (type);
910 int is_complete = COMPLETE_TYPE_P (complete_type (type));
912 /* Can't load the value if we don't know the type. */
913 if (is_volatile && !is_complete)
915 if (complain & tf_warning)
916 warning (0, "object of incomplete type %qT will not be accessed in %s",
917 type, implicit ? implicit : "void context");
919 /* Don't load the value if this is an implicit dereference, or if
920 the type needs to be handled by ctors/dtors. */
921 else if (is_volatile && (is_reference || TREE_ADDRESSABLE (type)))
923 if (complain & tf_warning)
924 warning (0, "object of type %qT will not be accessed in %s",
925 TREE_TYPE (TREE_OPERAND (expr, 0)),
926 implicit ? implicit : "void context");
928 if (is_reference || !is_volatile || !is_complete || TREE_ADDRESSABLE (type))
930 /* Emit a warning (if enabled) when the "effect-less" INDIRECT_REF
931 operation is stripped off. Note that we don't warn about
932 - an expression with TREE_NO_WARNING set. (For an example of
933 such expressions, see build_over_call in call.c.)
934 - automatic dereferencing of references, since the user cannot
935 control it. (See also warn_if_unused_value() in stmt.c.) */
936 if (warn_unused_value
938 && (complain & tf_warning)
939 && !TREE_NO_WARNING (expr)
941 warning (OPT_Wunused_value, "value computed is not used");
942 expr = TREE_OPERAND (expr, 0);
950 /* External variables might be incomplete. */
951 tree type = TREE_TYPE (expr);
952 int is_complete = COMPLETE_TYPE_P (complete_type (type));
954 if (TYPE_VOLATILE (type) && !is_complete && (complain & tf_warning))
955 warning (0, "object %qE of incomplete type %qT will not be accessed in %s",
956 expr, type, implicit ? implicit : "void context");
961 /* Don't bother with the temporary object returned from a function if
962 we don't use it and don't need to destroy it. We'll still
963 allocate space for it in expand_call or declare_return_variable,
964 but we don't need to track it through all the tree phases. */
965 if (TARGET_EXPR_IMPLICIT_P (expr)
966 && TYPE_HAS_TRIVIAL_DESTRUCTOR (TREE_TYPE (expr)))
968 tree init = TARGET_EXPR_INITIAL (expr);
969 if (TREE_CODE (init) == AGGR_INIT_EXPR
970 && !AGGR_INIT_VIA_CTOR_P (init))
972 tree fn = AGGR_INIT_EXPR_FN (init);
973 expr = build_call_array_loc (input_location,
974 TREE_TYPE (TREE_TYPE (TREE_TYPE (fn))),
976 aggr_init_expr_nargs (init),
977 AGGR_INIT_EXPR_ARGP (init));
984 expr = resolve_nondeduced_context (expr);
988 if (TREE_CODE (probe) == ADDR_EXPR)
989 probe = TREE_OPERAND (expr, 0);
990 if (type_unknown_p (probe))
992 /* [over.over] enumerates the places where we can take the address
993 of an overloaded function, and this is not one of them. */
994 if (complain & tf_error)
995 error ("%s cannot resolve address of overloaded function",
996 implicit ? implicit : "void cast");
998 return error_mark_node;
999 expr = void_zero_node;
1001 else if (implicit && probe == expr && is_overloaded_fn (probe))
1003 /* Only warn when there is no &. */
1004 if (complain & tf_warning)
1005 warning (OPT_Waddress, "%s is a reference, not call, to function %qE",
1007 if (TREE_CODE (expr) == COMPONENT_REF)
1008 expr = TREE_OPERAND (expr, 0);
1012 if (expr != error_mark_node && !VOID_TYPE_P (TREE_TYPE (expr)))
1015 && warn_unused_value
1016 && !TREE_NO_WARNING (expr)
1017 && !processing_template_decl)
1019 /* The middle end does not warn about expressions that have
1020 been explicitly cast to void, so we must do so here. */
1021 if (!TREE_SIDE_EFFECTS (expr)) {
1022 if (complain & tf_warning)
1023 warning (OPT_Wunused_value, "%s has no effect", implicit);
1028 enum tree_code code;
1029 enum tree_code_class tclass;
1032 /* We might like to warn about (say) "(int) f()", as the
1033 cast has no effect, but the compiler itself will
1034 generate implicit conversions under some
1035 circumstances. (For example a block copy will be
1036 turned into a call to "__builtin_memcpy", with a
1037 conversion of the return value to an appropriate
1038 type.) So, to avoid false positives, we strip
1039 conversions. Do not use STRIP_NOPs because it will
1040 not strip conversions to "void", as that is not a
1041 mode-preserving conversion. */
1042 while (TREE_CODE (e) == NOP_EXPR)
1043 e = TREE_OPERAND (e, 0);
1045 code = TREE_CODE (e);
1046 tclass = TREE_CODE_CLASS (code);
1047 if ((tclass == tcc_comparison
1048 || tclass == tcc_unary
1049 || (tclass == tcc_binary
1050 && !(code == MODIFY_EXPR
1051 || code == INIT_EXPR
1052 || code == PREDECREMENT_EXPR
1053 || code == PREINCREMENT_EXPR
1054 || code == POSTDECREMENT_EXPR
1055 || code == POSTINCREMENT_EXPR)))
1056 && (complain & tf_warning))
1057 warning (OPT_Wunused_value, "value computed is not used");
1060 expr = build1 (CONVERT_EXPR, void_type_node, expr);
1062 if (! TREE_SIDE_EFFECTS (expr))
1063 expr = void_zero_node;
1067 /* Create an expression whose value is that of EXPR,
1068 converted to type TYPE. The TREE_TYPE of the value
1069 is always TYPE. This function implements all reasonable
1070 conversions; callers should filter out those that are
1071 not permitted by the language being compiled.
1073 Most of this routine is from build_reinterpret_cast.
1075 The back end cannot call cp_convert (what was convert) because
1076 conversions to/from basetypes may involve memory references
1077 (vbases) and adding or subtracting small values (multiple
1078 inheritance), but it calls convert from the constant folding code
1079 on subtrees of already built trees after it has ripped them apart.
1081 Also, if we ever support range variables, we'll probably also have to
1082 do a little bit more work. */
1085 convert (tree type, tree expr)
1089 if (type == error_mark_node || expr == error_mark_node)
1090 return error_mark_node;
1092 intype = TREE_TYPE (expr);
1094 if (POINTER_TYPE_P (type) && POINTER_TYPE_P (intype))
1095 return fold_if_not_in_template (build_nop (type, expr));
1097 return ocp_convert (type, expr, CONV_OLD_CONVERT,
1098 LOOKUP_NORMAL|LOOKUP_NO_CONVERSION);
1101 /* Like cp_convert, except permit conversions to take place which
1102 are not normally allowed due to access restrictions
1103 (such as conversion from sub-type to private super-type). */
1106 convert_force (tree type, tree expr, int convtype)
1109 enum tree_code code = TREE_CODE (type);
1111 if (code == REFERENCE_TYPE)
1112 return (fold_if_not_in_template
1113 (convert_to_reference (type, e, CONV_C_CAST, LOOKUP_COMPLAIN,
1116 if (code == POINTER_TYPE)
1117 return fold_if_not_in_template (convert_to_pointer_force (type, e));
1119 /* From typeck.c convert_for_assignment */
1120 if (((TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE && TREE_CODE (e) == ADDR_EXPR
1121 && TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE
1122 && TREE_CODE (TREE_TYPE (TREE_TYPE (e))) == METHOD_TYPE)
1123 || integer_zerop (e)
1124 || TYPE_PTRMEMFUNC_P (TREE_TYPE (e)))
1125 && TYPE_PTRMEMFUNC_P (type))
1126 /* compatible pointer to member functions. */
1127 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), e, 1,
1130 return ocp_convert (type, e, CONV_C_CAST|convtype, LOOKUP_NORMAL);
1133 /* Convert an aggregate EXPR to type XTYPE. If a conversion
1134 exists, return the attempted conversion. This may
1135 return ERROR_MARK_NODE if the conversion is not
1136 allowed (references private members, etc).
1137 If no conversion exists, NULL_TREE is returned.
1139 FIXME: Ambiguity checking is wrong. Should choose one by the implicit
1140 object parameter, or by the second standard conversion sequence if
1141 that doesn't do it. This will probably wait for an overloading rewrite.
1145 build_type_conversion (tree xtype, tree expr)
1147 /* C++: check to see if we can convert this aggregate type
1148 into the required type. */
1149 return build_user_type_conversion (xtype, expr, LOOKUP_NORMAL);
1152 /* Convert the given EXPR to one of a group of types suitable for use in an
1153 expression. DESIRES is a combination of various WANT_* flags (q.v.)
1154 which indicates which types are suitable. If COMPLAIN is true, complain
1155 about ambiguity; otherwise, the caller will deal with it. */
1158 build_expr_type_conversion (int desires, tree expr, bool complain)
1160 tree basetype = TREE_TYPE (expr);
1161 tree conv = NULL_TREE;
1162 tree winner = NULL_TREE;
1164 if (expr == null_node
1165 && (desires & WANT_INT)
1166 && !(desires & WANT_NULL))
1167 warning_at (input_location, OPT_Wconversion_null,
1168 "converting NULL to non-pointer type");
1170 basetype = TREE_TYPE (expr);
1172 if (basetype == error_mark_node)
1173 return error_mark_node;
1175 if (! MAYBE_CLASS_TYPE_P (basetype))
1176 switch (TREE_CODE (basetype))
1179 if ((desires & WANT_NULL) && null_ptr_cst_p (expr))
1181 /* else fall through... */
1184 return (desires & WANT_INT) ? expr : NULL_TREE;
1186 return (desires & WANT_ENUM) ? expr : NULL_TREE;
1188 return (desires & WANT_FLOAT) ? expr : NULL_TREE;
1190 return (desires & WANT_POINTER) ? expr : NULL_TREE;
1194 return (desires & WANT_POINTER) ? decay_conversion (expr)
1199 if ((desires & WANT_VECTOR_OR_COMPLEX) == 0)
1201 switch (TREE_CODE (TREE_TYPE (basetype)))
1205 return (desires & WANT_INT) ? expr : NULL_TREE;
1207 return (desires & WANT_ENUM) ? expr : NULL_TREE;
1209 return (desires & WANT_FLOAT) ? expr : NULL_TREE;
1218 /* The code for conversions from class type is currently only used for
1219 delete expressions. Other expressions are handled by build_new_op. */
1220 if (!complete_type_or_else (basetype, expr))
1221 return error_mark_node;
1222 if (!TYPE_HAS_CONVERSION (basetype))
1225 for (conv = lookup_conversions (basetype, /*lookup_template_convs_p=*/true);
1227 conv = TREE_CHAIN (conv))
1231 tree cand = TREE_VALUE (conv);
1232 cand = OVL_CURRENT (cand);
1234 if (winner && winner == cand)
1237 if (DECL_NONCONVERTING_P (cand))
1240 candidate = non_reference (TREE_TYPE (TREE_TYPE (cand)));
1242 switch (TREE_CODE (candidate))
1246 win = (desires & WANT_INT); break;
1248 win = (desires & WANT_ENUM); break;
1250 win = (desires & WANT_FLOAT); break;
1252 win = (desires & WANT_POINTER); break;
1256 if ((desires & WANT_VECTOR_OR_COMPLEX) == 0)
1258 switch (TREE_CODE (TREE_TYPE (candidate)))
1262 win = (desires & WANT_INT); break;
1264 win = (desires & WANT_ENUM); break;
1266 win = (desires & WANT_FLOAT); break;
1282 error ("ambiguous default type conversion from %qT",
1284 error (" candidate conversions include %qD and %qD",
1287 return error_mark_node;
1296 tree type = non_reference (TREE_TYPE (TREE_TYPE (winner)));
1297 return build_user_type_conversion (type, expr, LOOKUP_NORMAL);
1303 /* Implements integral promotion (4.1) and float->double promotion. */
1306 type_promotes_to (tree type)
1310 if (type == error_mark_node)
1311 return error_mark_node;
1313 type = TYPE_MAIN_VARIANT (type);
1315 /* Check for promotions of target-defined types first. */
1316 promoted_type = targetm.promoted_type (type);
1318 return promoted_type;
1320 /* bool always promotes to int (not unsigned), even if it's the same
1322 if (TREE_CODE (type) == BOOLEAN_TYPE)
1323 type = integer_type_node;
1325 /* Normally convert enums to int, but convert wide enums to something
1327 else if (TREE_CODE (type) == ENUMERAL_TYPE
1328 || type == char16_type_node
1329 || type == char32_type_node
1330 || type == wchar_type_node)
1332 int precision = MAX (TYPE_PRECISION (type),
1333 TYPE_PRECISION (integer_type_node));
1334 tree totype = c_common_type_for_size (precision, 0);
1335 if (TREE_CODE (type) == ENUMERAL_TYPE)
1336 type = ENUM_UNDERLYING_TYPE (type);
1337 if (TYPE_UNSIGNED (type)
1338 && ! int_fits_type_p (TYPE_MAX_VALUE (type), totype))
1339 type = c_common_type_for_size (precision, 1);
1343 else if (c_promoting_integer_type_p (type))
1345 /* Retain unsignedness if really not getting bigger. */
1346 if (TYPE_UNSIGNED (type)
1347 && TYPE_PRECISION (type) == TYPE_PRECISION (integer_type_node))
1348 type = unsigned_type_node;
1350 type = integer_type_node;
1352 else if (type == float_type_node)
1353 type = double_type_node;
1358 /* The routines below this point are carefully written to conform to
1359 the standard. They use the same terminology, and follow the rules
1360 closely. Although they are used only in pt.c at the moment, they
1361 should presumably be used everywhere in the future. */
1363 /* Attempt to perform qualification conversions on EXPR to convert it
1364 to TYPE. Return the resulting expression, or error_mark_node if
1365 the conversion was impossible. */
1368 perform_qualification_conversions (tree type, tree expr)
1372 expr_type = TREE_TYPE (expr);
1374 if (same_type_p (type, expr_type))
1376 else if (TYPE_PTR_P (type) && TYPE_PTR_P (expr_type)
1377 && comp_ptr_ttypes (TREE_TYPE (type), TREE_TYPE (expr_type)))
1378 return build_nop (type, expr);
1379 else if (TYPE_PTR_TO_MEMBER_P (type)
1380 && TYPE_PTR_TO_MEMBER_P (expr_type)
1381 && same_type_p (TYPE_PTRMEM_CLASS_TYPE (type),
1382 TYPE_PTRMEM_CLASS_TYPE (expr_type))
1383 && comp_ptr_ttypes (TYPE_PTRMEM_POINTED_TO_TYPE (type),
1384 TYPE_PTRMEM_POINTED_TO_TYPE (expr_type)))
1385 return build_nop (type, expr);
1387 return error_mark_node;