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 (null_ptr_cst_p (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,
484 ICR_CONVERTING, 0, 0,
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);
838 || handled_component_p (exprv)
839 || TREE_CODE (exprv) == INDIRECT_REF)
840 /* Expr is not being 'used' here, otherwise we whould have
841 called mark_{rl}value_use use here, which would have in turn
842 called mark_exp_read. Rather, we call mark_exp_read directly
843 to avoid some warnings when
844 -Wunused-but-set-{variable,parameter} is in effect. */
845 mark_exp_read (exprv);
848 if (!TREE_TYPE (expr))
850 if (invalid_nonstatic_memfn_p (expr, complain))
851 return error_mark_node;
852 if (TREE_CODE (expr) == PSEUDO_DTOR_EXPR)
854 if (complain & tf_error)
855 error ("pseudo-destructor is not called");
856 return error_mark_node;
858 if (VOID_TYPE_P (TREE_TYPE (expr)))
860 switch (TREE_CODE (expr))
864 /* The two parts of a cond expr might be separate lvalues. */
865 tree op1 = TREE_OPERAND (expr,1);
866 tree op2 = TREE_OPERAND (expr,2);
867 bool side_effects = TREE_SIDE_EFFECTS (op1) || TREE_SIDE_EFFECTS (op2);
868 tree new_op1 = convert_to_void
869 (op1, (implicit && !side_effects
870 ? "second operand of conditional" : NULL), complain);
871 tree new_op2 = convert_to_void
872 (op2, (implicit && !side_effects
873 ? "third operand of conditional" : NULL), complain);
875 expr = build3 (COND_EXPR, TREE_TYPE (new_op1),
876 TREE_OPERAND (expr, 0), new_op1, new_op2);
882 /* The second part of a compound expr contains the value. */
883 tree op1 = TREE_OPERAND (expr,1);
884 tree new_op1 = convert_to_void
885 (op1, (implicit && !TREE_NO_WARNING (expr)
886 ? "right-hand operand of comma" : NULL), complain);
890 tree t = build2 (COMPOUND_EXPR, TREE_TYPE (new_op1),
891 TREE_OPERAND (expr, 0), new_op1);
898 case NON_LVALUE_EXPR:
900 /* These have already decayed to rvalue. */
903 case CALL_EXPR: /* We have a special meaning for volatile void fn(). */
908 tree type = TREE_TYPE (expr);
909 int is_reference = TREE_CODE (TREE_TYPE (TREE_OPERAND (expr, 0)))
911 int is_volatile = TYPE_VOLATILE (type);
912 int is_complete = COMPLETE_TYPE_P (complete_type (type));
914 /* Can't load the value if we don't know the type. */
915 if (is_volatile && !is_complete)
917 if (complain & tf_warning)
918 warning (0, "object of incomplete type %qT will not be accessed in %s",
919 type, implicit ? implicit : "void context");
921 /* Don't load the value if this is an implicit dereference, or if
922 the type needs to be handled by ctors/dtors. */
923 else if (is_volatile && (is_reference || TREE_ADDRESSABLE (type)))
925 if (complain & tf_warning)
926 warning (0, "object of type %qT will not be accessed in %s",
927 TREE_TYPE (TREE_OPERAND (expr, 0)),
928 implicit ? implicit : "void context");
930 if (is_reference || !is_volatile || !is_complete || TREE_ADDRESSABLE (type))
932 /* Emit a warning (if enabled) when the "effect-less" INDIRECT_REF
933 operation is stripped off. Note that we don't warn about
934 - an expression with TREE_NO_WARNING set. (For an example of
935 such expressions, see build_over_call in call.c.)
936 - automatic dereferencing of references, since the user cannot
937 control it. (See also warn_if_unused_value() in stmt.c.) */
938 if (warn_unused_value
940 && (complain & tf_warning)
941 && !TREE_NO_WARNING (expr)
943 warning (OPT_Wunused_value, "value computed is not used");
944 expr = TREE_OPERAND (expr, 0);
952 /* External variables might be incomplete. */
953 tree type = TREE_TYPE (expr);
954 int is_complete = COMPLETE_TYPE_P (complete_type (type));
956 if (TYPE_VOLATILE (type) && !is_complete && (complain & tf_warning))
957 warning (0, "object %qE of incomplete type %qT will not be accessed in %s",
958 expr, type, implicit ? implicit : "void context");
963 /* Don't bother with the temporary object returned from a function if
964 we don't use it and don't need to destroy it. We'll still
965 allocate space for it in expand_call or declare_return_variable,
966 but we don't need to track it through all the tree phases. */
967 if (TARGET_EXPR_IMPLICIT_P (expr)
968 && TYPE_HAS_TRIVIAL_DESTRUCTOR (TREE_TYPE (expr)))
970 tree init = TARGET_EXPR_INITIAL (expr);
971 if (TREE_CODE (init) == AGGR_INIT_EXPR
972 && !AGGR_INIT_VIA_CTOR_P (init))
974 tree fn = AGGR_INIT_EXPR_FN (init);
975 expr = build_call_array_loc (input_location,
976 TREE_TYPE (TREE_TYPE (TREE_TYPE (fn))),
978 aggr_init_expr_nargs (init),
979 AGGR_INIT_EXPR_ARGP (init));
986 expr = resolve_nondeduced_context (expr);
990 if (TREE_CODE (probe) == ADDR_EXPR)
991 probe = TREE_OPERAND (expr, 0);
992 if (type_unknown_p (probe))
994 /* [over.over] enumerates the places where we can take the address
995 of an overloaded function, and this is not one of them. */
996 if (complain & tf_error)
997 error ("%s cannot resolve address of overloaded function",
998 implicit ? implicit : "void cast");
1000 return error_mark_node;
1001 expr = void_zero_node;
1003 else if (implicit && probe == expr && is_overloaded_fn (probe))
1005 /* Only warn when there is no &. */
1006 if (complain & tf_warning)
1007 warning (OPT_Waddress, "%s is a reference, not call, to function %qE",
1009 if (TREE_CODE (expr) == COMPONENT_REF)
1010 expr = TREE_OPERAND (expr, 0);
1014 if (expr != error_mark_node && !VOID_TYPE_P (TREE_TYPE (expr)))
1017 && warn_unused_value
1018 && !TREE_NO_WARNING (expr)
1019 && !processing_template_decl)
1021 /* The middle end does not warn about expressions that have
1022 been explicitly cast to void, so we must do so here. */
1023 if (!TREE_SIDE_EFFECTS (expr)) {
1024 if (complain & tf_warning)
1025 warning (OPT_Wunused_value, "%s has no effect", implicit);
1030 enum tree_code code;
1031 enum tree_code_class tclass;
1034 /* We might like to warn about (say) "(int) f()", as the
1035 cast has no effect, but the compiler itself will
1036 generate implicit conversions under some
1037 circumstances. (For example a block copy will be
1038 turned into a call to "__builtin_memcpy", with a
1039 conversion of the return value to an appropriate
1040 type.) So, to avoid false positives, we strip
1041 conversions. Do not use STRIP_NOPs because it will
1042 not strip conversions to "void", as that is not a
1043 mode-preserving conversion. */
1044 while (TREE_CODE (e) == NOP_EXPR)
1045 e = TREE_OPERAND (e, 0);
1047 code = TREE_CODE (e);
1048 tclass = TREE_CODE_CLASS (code);
1049 if ((tclass == tcc_comparison
1050 || tclass == tcc_unary
1051 || (tclass == tcc_binary
1052 && !(code == MODIFY_EXPR
1053 || code == INIT_EXPR
1054 || code == PREDECREMENT_EXPR
1055 || code == PREINCREMENT_EXPR
1056 || code == POSTDECREMENT_EXPR
1057 || code == POSTINCREMENT_EXPR)))
1058 && (complain & tf_warning))
1059 warning (OPT_Wunused_value, "value computed is not used");
1062 expr = build1 (CONVERT_EXPR, void_type_node, expr);
1064 if (! TREE_SIDE_EFFECTS (expr))
1065 expr = void_zero_node;
1069 /* Create an expression whose value is that of EXPR,
1070 converted to type TYPE. The TREE_TYPE of the value
1071 is always TYPE. This function implements all reasonable
1072 conversions; callers should filter out those that are
1073 not permitted by the language being compiled.
1075 Most of this routine is from build_reinterpret_cast.
1077 The back end cannot call cp_convert (what was convert) because
1078 conversions to/from basetypes may involve memory references
1079 (vbases) and adding or subtracting small values (multiple
1080 inheritance), but it calls convert from the constant folding code
1081 on subtrees of already built trees after it has ripped them apart.
1083 Also, if we ever support range variables, we'll probably also have to
1084 do a little bit more work. */
1087 convert (tree type, tree expr)
1091 if (type == error_mark_node || expr == error_mark_node)
1092 return error_mark_node;
1094 intype = TREE_TYPE (expr);
1096 if (POINTER_TYPE_P (type) && POINTER_TYPE_P (intype))
1097 return fold_if_not_in_template (build_nop (type, expr));
1099 return ocp_convert (type, expr, CONV_OLD_CONVERT,
1100 LOOKUP_NORMAL|LOOKUP_NO_CONVERSION);
1103 /* Like cp_convert, except permit conversions to take place which
1104 are not normally allowed due to access restrictions
1105 (such as conversion from sub-type to private super-type). */
1108 convert_force (tree type, tree expr, int convtype)
1111 enum tree_code code = TREE_CODE (type);
1113 if (code == REFERENCE_TYPE)
1114 return (fold_if_not_in_template
1115 (convert_to_reference (type, e, CONV_C_CAST, LOOKUP_COMPLAIN,
1118 if (code == POINTER_TYPE)
1119 return fold_if_not_in_template (convert_to_pointer_force (type, e));
1121 /* From typeck.c convert_for_assignment */
1122 if (((TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE && TREE_CODE (e) == ADDR_EXPR
1123 && TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE
1124 && TREE_CODE (TREE_TYPE (TREE_TYPE (e))) == METHOD_TYPE)
1125 || integer_zerop (e)
1126 || TYPE_PTRMEMFUNC_P (TREE_TYPE (e)))
1127 && TYPE_PTRMEMFUNC_P (type))
1128 /* compatible pointer to member functions. */
1129 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), e, 1,
1132 return ocp_convert (type, e, CONV_C_CAST|convtype, LOOKUP_NORMAL);
1135 /* Convert an aggregate EXPR to type XTYPE. If a conversion
1136 exists, return the attempted conversion. This may
1137 return ERROR_MARK_NODE if the conversion is not
1138 allowed (references private members, etc).
1139 If no conversion exists, NULL_TREE is returned.
1141 FIXME: Ambiguity checking is wrong. Should choose one by the implicit
1142 object parameter, or by the second standard conversion sequence if
1143 that doesn't do it. This will probably wait for an overloading rewrite.
1147 build_type_conversion (tree xtype, tree expr)
1149 /* C++: check to see if we can convert this aggregate type
1150 into the required type. */
1151 return build_user_type_conversion (xtype, expr, LOOKUP_NORMAL);
1154 /* Convert the given EXPR to one of a group of types suitable for use in an
1155 expression. DESIRES is a combination of various WANT_* flags (q.v.)
1156 which indicates which types are suitable. If COMPLAIN is true, complain
1157 about ambiguity; otherwise, the caller will deal with it. */
1160 build_expr_type_conversion (int desires, tree expr, bool complain)
1162 tree basetype = TREE_TYPE (expr);
1163 tree conv = NULL_TREE;
1164 tree winner = NULL_TREE;
1166 if (expr == null_node
1167 && (desires & WANT_INT)
1168 && !(desires & WANT_NULL))
1169 warning_at (input_location, OPT_Wconversion_null,
1170 "converting NULL to non-pointer type");
1172 basetype = TREE_TYPE (expr);
1174 if (basetype == error_mark_node)
1175 return error_mark_node;
1177 if (! MAYBE_CLASS_TYPE_P (basetype))
1178 switch (TREE_CODE (basetype))
1181 if ((desires & WANT_NULL) && null_ptr_cst_p (expr))
1183 /* else fall through... */
1186 return (desires & WANT_INT) ? expr : NULL_TREE;
1188 return (desires & WANT_ENUM) ? expr : NULL_TREE;
1190 return (desires & WANT_FLOAT) ? expr : NULL_TREE;
1192 return (desires & WANT_POINTER) ? expr : NULL_TREE;
1196 return (desires & WANT_POINTER) ? decay_conversion (expr)
1201 if ((desires & WANT_VECTOR_OR_COMPLEX) == 0)
1203 switch (TREE_CODE (TREE_TYPE (basetype)))
1207 return (desires & WANT_INT) ? expr : NULL_TREE;
1209 return (desires & WANT_ENUM) ? expr : NULL_TREE;
1211 return (desires & WANT_FLOAT) ? expr : NULL_TREE;
1220 /* The code for conversions from class type is currently only used for
1221 delete expressions. Other expressions are handled by build_new_op. */
1222 if (!complete_type_or_else (basetype, expr))
1223 return error_mark_node;
1224 if (!TYPE_HAS_CONVERSION (basetype))
1227 for (conv = lookup_conversions (basetype, /*lookup_template_convs_p=*/true);
1229 conv = TREE_CHAIN (conv))
1233 tree cand = TREE_VALUE (conv);
1234 cand = OVL_CURRENT (cand);
1236 if (winner && winner == cand)
1239 if (DECL_NONCONVERTING_P (cand))
1242 candidate = non_reference (TREE_TYPE (TREE_TYPE (cand)));
1244 switch (TREE_CODE (candidate))
1248 win = (desires & WANT_INT); break;
1250 win = (desires & WANT_ENUM); break;
1252 win = (desires & WANT_FLOAT); break;
1254 win = (desires & WANT_POINTER); break;
1258 if ((desires & WANT_VECTOR_OR_COMPLEX) == 0)
1260 switch (TREE_CODE (TREE_TYPE (candidate)))
1264 win = (desires & WANT_INT); break;
1266 win = (desires & WANT_ENUM); break;
1268 win = (desires & WANT_FLOAT); break;
1284 error ("ambiguous default type conversion from %qT",
1286 error (" candidate conversions include %qD and %qD",
1289 return error_mark_node;
1298 tree type = non_reference (TREE_TYPE (TREE_TYPE (winner)));
1299 return build_user_type_conversion (type, expr, LOOKUP_NORMAL);
1305 /* Implements integral promotion (4.1) and float->double promotion. */
1308 type_promotes_to (tree type)
1312 if (type == error_mark_node)
1313 return error_mark_node;
1315 type = TYPE_MAIN_VARIANT (type);
1317 /* Check for promotions of target-defined types first. */
1318 promoted_type = targetm.promoted_type (type);
1320 return promoted_type;
1322 /* bool always promotes to int (not unsigned), even if it's the same
1324 if (TREE_CODE (type) == BOOLEAN_TYPE)
1325 type = integer_type_node;
1327 /* Normally convert enums to int, but convert wide enums to something
1329 else if (TREE_CODE (type) == ENUMERAL_TYPE
1330 || type == char16_type_node
1331 || type == char32_type_node
1332 || type == wchar_type_node)
1334 int precision = MAX (TYPE_PRECISION (type),
1335 TYPE_PRECISION (integer_type_node));
1336 tree totype = c_common_type_for_size (precision, 0);
1337 if (TREE_CODE (type) == ENUMERAL_TYPE)
1338 type = ENUM_UNDERLYING_TYPE (type);
1339 if (TYPE_UNSIGNED (type)
1340 && ! int_fits_type_p (TYPE_MAX_VALUE (type), totype))
1341 type = c_common_type_for_size (precision, 1);
1345 else if (c_promoting_integer_type_p (type))
1347 /* Retain unsignedness if really not getting bigger. */
1348 if (TYPE_UNSIGNED (type)
1349 && TYPE_PRECISION (type) == TYPE_PRECISION (integer_type_node))
1350 type = unsigned_type_node;
1352 type = integer_type_node;
1354 else if (type == float_type_node)
1355 type = double_type_node;
1360 /* The routines below this point are carefully written to conform to
1361 the standard. They use the same terminology, and follow the rules
1362 closely. Although they are used only in pt.c at the moment, they
1363 should presumably be used everywhere in the future. */
1365 /* Attempt to perform qualification conversions on EXPR to convert it
1366 to TYPE. Return the resulting expression, or error_mark_node if
1367 the conversion was impossible. */
1370 perform_qualification_conversions (tree type, tree expr)
1374 expr_type = TREE_TYPE (expr);
1376 if (same_type_p (type, expr_type))
1378 else if (TYPE_PTR_P (type) && TYPE_PTR_P (expr_type)
1379 && comp_ptr_ttypes (TREE_TYPE (type), TREE_TYPE (expr_type)))
1380 return build_nop (type, expr);
1381 else if (TYPE_PTR_TO_MEMBER_P (type)
1382 && TYPE_PTR_TO_MEMBER_P (expr_type)
1383 && same_type_p (TYPE_PTRMEM_CLASS_TYPE (type),
1384 TYPE_PTRMEM_CLASS_TYPE (expr_type))
1385 && comp_ptr_ttypes (TYPE_PTRMEM_POINTED_TO_TYPE (type),
1386 TYPE_PTRMEM_POINTED_TO_TYPE (expr_type)))
1387 return build_nop (type, expr);
1389 return error_mark_node;