1 /* Language-level data type conversion for GNU C++.
2 Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
3 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
4 Free Software Foundation, Inc.
5 Hacked by Michael Tiemann (tiemann@cygnus.com)
7 This file is part of GCC.
9 GCC is free software; you can redistribute it and/or modify
10 it under the terms of the GNU General Public License as published by
11 the Free Software Foundation; either version 3, or (at your option)
14 GCC is distributed in the hope that it will be useful,
15 but WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License for more details.
19 You should have received a copy of the GNU General Public License
20 along with GCC; see the file COPYING3. If not see
21 <http://www.gnu.org/licenses/>. */
24 /* This file contains the functions for converting C++ expressions
25 to different data types. The only entry point is `convert'.
26 Every language front end must have a `convert' function
27 but what kind of conversions it does will depend on the language. */
31 #include "coretypes.h"
41 static tree cp_convert_to_pointer (tree, tree);
42 static tree convert_to_pointer_force (tree, tree);
43 static tree build_type_conversion (tree, tree);
44 static tree build_up_reference (tree, tree, int, tree);
45 static void warn_ref_binding (tree, tree, tree);
47 /* Change of width--truncation and extension of integers or reals--
48 is represented with NOP_EXPR. Proper functioning of many things
49 assumes that no other conversions can be NOP_EXPRs.
51 Conversion between integer and pointer is represented with CONVERT_EXPR.
52 Converting integer to real uses FLOAT_EXPR
53 and real to integer uses FIX_TRUNC_EXPR.
55 Here is a list of all the functions that assume that widening and
56 narrowing is always done with a NOP_EXPR:
57 In convert.c, convert_to_integer.
58 In c-typeck.c, build_binary_op_nodefault (boolean ops),
59 and c_common_truthvalue_conversion.
60 In expr.c: expand_expr, for operands of a MULT_EXPR.
61 In fold-const.c: fold.
62 In tree.c: get_narrower and get_unwidened.
64 C++: in multiple-inheritance, converting between pointers may involve
65 adjusting them by a delta stored within the class definition. */
67 /* Subroutines of `convert'. */
69 /* if converting pointer to pointer
70 if dealing with classes, check for derived->base or vice versa
71 else if dealing with method pointers, delegate
73 else if converting class, pass off to build_type_conversion
74 else try C-style pointer conversion. */
77 cp_convert_to_pointer (tree type, tree expr)
79 tree intype = TREE_TYPE (expr);
82 if (intype == error_mark_node)
83 return error_mark_node;
85 if (MAYBE_CLASS_TYPE_P (intype))
87 intype = complete_type (intype);
88 if (!COMPLETE_TYPE_P (intype))
90 error ("can't convert from incomplete type %qT to %qT",
92 return error_mark_node;
95 rval = build_type_conversion (type, expr);
98 if (rval == error_mark_node)
99 error ("conversion of %qE from %qT to %qT is ambiguous",
105 /* Handle anachronistic conversions from (::*)() to cv void* or (*)(). */
106 if (TREE_CODE (type) == POINTER_TYPE
107 && (TREE_CODE (TREE_TYPE (type)) == FUNCTION_TYPE
108 || VOID_TYPE_P (TREE_TYPE (type))))
110 if (TYPE_PTRMEMFUNC_P (intype)
111 || TREE_CODE (intype) == METHOD_TYPE)
112 return convert_member_func_to_ptr (type, expr);
113 if (TREE_CODE (TREE_TYPE (expr)) == POINTER_TYPE)
114 return build_nop (type, expr);
115 intype = TREE_TYPE (expr);
118 if (expr == error_mark_node)
119 return error_mark_node;
121 form = TREE_CODE (intype);
123 if (POINTER_TYPE_P (intype))
125 intype = TYPE_MAIN_VARIANT (intype);
127 if (TYPE_MAIN_VARIANT (type) != intype
128 && TREE_CODE (type) == POINTER_TYPE
129 && TREE_CODE (TREE_TYPE (type)) == RECORD_TYPE
130 && MAYBE_CLASS_TYPE_P (TREE_TYPE (type))
131 && MAYBE_CLASS_TYPE_P (TREE_TYPE (intype))
132 && TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE)
134 enum tree_code code = PLUS_EXPR;
140 intype_class = TREE_TYPE (intype);
141 type_class = TREE_TYPE (type);
143 same_p = same_type_p (TYPE_MAIN_VARIANT (intype_class),
144 TYPE_MAIN_VARIANT (type_class));
146 /* Try derived to base conversion. */
148 binfo = lookup_base (intype_class, type_class, ba_check, NULL);
149 if (!same_p && !binfo)
151 /* Try base to derived conversion. */
152 binfo = lookup_base (type_class, intype_class, ba_check, NULL);
155 if (binfo == error_mark_node)
156 return error_mark_node;
160 expr = build_base_path (code, expr, binfo, 0);
161 /* Add any qualifier conversions. */
162 return build_nop (type, expr);
166 if (TYPE_PTRMEMFUNC_P (type))
168 error ("cannot convert %qE from type %qT to type %qT",
170 return error_mark_node;
173 return build_nop (type, expr);
175 else if ((TYPE_PTRMEM_P (type) && TYPE_PTRMEM_P (intype))
176 || (TYPE_PTRMEMFUNC_P (type) && TYPE_PTRMEMFUNC_P (intype)))
177 return convert_ptrmem (type, expr, /*allow_inverse_p=*/false,
179 else if (TYPE_PTRMEMFUNC_P (intype))
183 if (TREE_CODE (expr) == PTRMEM_CST)
184 return cp_convert_to_pointer (type,
185 PTRMEM_CST_MEMBER (expr));
186 else if (TREE_CODE (expr) == OFFSET_REF)
188 tree object = TREE_OPERAND (expr, 0);
189 return get_member_function_from_ptrfunc (&object,
190 TREE_OPERAND (expr, 1));
193 error ("cannot convert %qE from type %qT to type %qT",
195 return error_mark_node;
198 if (integer_zerop (expr))
200 if (TYPE_PTRMEMFUNC_P (type))
201 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), expr, 0,
204 if (TYPE_PTRMEM_P (type))
206 /* A NULL pointer-to-member is represented by -1, not by
208 expr = build_int_cst_type (type, -1);
211 expr = build_int_cst (type, 0);
215 else if (TYPE_PTR_TO_MEMBER_P (type) && INTEGRAL_CODE_P (form))
217 error ("invalid conversion from %qT to %qT", intype, type);
218 return error_mark_node;
221 if (INTEGRAL_CODE_P (form))
223 if (TYPE_PRECISION (intype) == POINTER_SIZE)
224 return build1 (CONVERT_EXPR, type, expr);
225 expr = cp_convert (c_common_type_for_size (POINTER_SIZE, 0), expr);
226 /* Modes may be different but sizes should be the same. There
227 is supposed to be some integral type that is the same width
229 gcc_assert (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (expr)))
230 == GET_MODE_SIZE (TYPE_MODE (type)));
232 return convert_to_pointer (type, expr);
235 if (type_unknown_p (expr))
236 return instantiate_type (type, expr, tf_warning_or_error);
238 error ("cannot convert %qE from type %qT to type %qT",
240 return error_mark_node;
243 /* Like convert, except permit conversions to take place which
244 are not normally allowed due to access restrictions
245 (such as conversion from sub-type to private super-type). */
248 convert_to_pointer_force (tree type, tree expr)
250 tree intype = TREE_TYPE (expr);
251 enum tree_code form = TREE_CODE (intype);
253 if (form == POINTER_TYPE)
255 intype = TYPE_MAIN_VARIANT (intype);
257 if (TYPE_MAIN_VARIANT (type) != intype
258 && TREE_CODE (TREE_TYPE (type)) == RECORD_TYPE
259 && MAYBE_CLASS_TYPE_P (TREE_TYPE (type))
260 && MAYBE_CLASS_TYPE_P (TREE_TYPE (intype))
261 && TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE)
263 enum tree_code code = PLUS_EXPR;
266 binfo = lookup_base (TREE_TYPE (intype), TREE_TYPE (type),
270 binfo = lookup_base (TREE_TYPE (type), TREE_TYPE (intype),
274 if (binfo == error_mark_node)
275 return error_mark_node;
278 expr = build_base_path (code, expr, binfo, 0);
279 if (expr == error_mark_node)
280 return error_mark_node;
281 /* Add any qualifier conversions. */
282 if (!same_type_p (TREE_TYPE (TREE_TYPE (expr)),
284 expr = build_nop (type, expr);
290 return cp_convert_to_pointer (type, expr);
293 /* We are passing something to a function which requires a reference.
294 The type we are interested in is in TYPE. The initial
295 value we have to begin with is in ARG.
297 FLAGS controls how we manage access checking.
298 DIRECT_BIND in FLAGS controls how any temporaries are generated.
299 If DIRECT_BIND is set, DECL is the reference we're binding to. */
302 build_up_reference (tree type, tree arg, int flags, tree decl)
305 tree argtype = TREE_TYPE (arg);
306 tree target_type = TREE_TYPE (type);
308 gcc_assert (TREE_CODE (type) == REFERENCE_TYPE);
310 if ((flags & DIRECT_BIND) && ! real_lvalue_p (arg))
312 /* Create a new temporary variable. We can't just use a TARGET_EXPR
313 here because it needs to live as long as DECL. */
316 arg = make_temporary_var_for_ref_to_temp (decl, TREE_TYPE (arg));
318 /* Process the initializer for the declaration. */
319 DECL_INITIAL (arg) = targ;
320 cp_finish_decl (arg, targ, /*init_const_expr_p=*/false, NULL_TREE,
321 LOOKUP_ONLYCONVERTING|DIRECT_BIND);
323 else if (!(flags & DIRECT_BIND) && ! lvalue_p (arg))
324 return get_target_expr (arg);
326 /* If we had a way to wrap this up, and say, if we ever needed its
327 address, transform all occurrences of the register, into a memory
328 reference we could win better. */
329 rval = cp_build_unary_op (ADDR_EXPR, arg, 1, tf_warning_or_error);
330 if (rval == error_mark_node)
331 return error_mark_node;
333 if ((flags & LOOKUP_PROTECT)
334 && TYPE_MAIN_VARIANT (argtype) != TYPE_MAIN_VARIANT (target_type)
335 && MAYBE_CLASS_TYPE_P (argtype)
336 && MAYBE_CLASS_TYPE_P (target_type))
338 /* We go through lookup_base for the access control. */
339 tree binfo = lookup_base (argtype, target_type, ba_check, NULL);
340 if (binfo == error_mark_node)
341 return error_mark_node;
342 if (binfo == NULL_TREE)
343 return error_not_base_type (target_type, argtype);
344 rval = build_base_path (PLUS_EXPR, rval, binfo, 1);
348 = convert_to_pointer_force (build_pointer_type (target_type), rval);
349 return build_nop (type, rval);
352 /* Subroutine of convert_to_reference. REFTYPE is the target reference type.
353 INTYPE is the original rvalue type and DECL is an optional _DECL node
356 [dcl.init.ref] says that if an rvalue is used to
357 initialize a reference, then the reference must be to a
358 non-volatile const type. */
361 warn_ref_binding (tree reftype, tree intype, tree decl)
363 tree ttl = TREE_TYPE (reftype);
365 if (!CP_TYPE_CONST_NON_VOLATILE_P (ttl))
369 if (CP_TYPE_VOLATILE_P (ttl) && decl)
370 msg = "initialization of volatile reference type %q#T from"
371 " rvalue of type %qT";
372 else if (CP_TYPE_VOLATILE_P (ttl))
373 msg = "conversion to volatile reference type %q#T "
374 " from rvalue of type %qT";
376 msg = "initialization of non-const reference type %q#T from"
377 " rvalue of type %qT";
379 msg = "conversion to non-const reference type %q#T from"
380 " rvalue of type %qT";
382 permerror (input_location, msg, reftype, intype);
386 /* For C++: Only need to do one-level references, but cannot
387 get tripped up on signed/unsigned differences.
389 DECL is either NULL_TREE or the _DECL node for a reference that is being
390 initialized. It can be error_mark_node if we don't know the _DECL but
391 we know it's an initialization. */
394 convert_to_reference (tree reftype, tree expr, int convtype,
395 int flags, tree decl)
397 tree type = TYPE_MAIN_VARIANT (TREE_TYPE (reftype));
399 tree rval = NULL_TREE;
400 tree rval_as_conversion = NULL_TREE;
401 bool can_convert_intype_to_type;
403 if (TREE_CODE (type) == FUNCTION_TYPE
404 && TREE_TYPE (expr) == unknown_type_node)
405 expr = instantiate_type (type, expr,
406 (flags & LOOKUP_COMPLAIN)
407 ? tf_warning_or_error : tf_none);
409 if (expr == error_mark_node)
410 return error_mark_node;
412 intype = TREE_TYPE (expr);
414 gcc_assert (TREE_CODE (intype) != REFERENCE_TYPE);
415 gcc_assert (TREE_CODE (reftype) == REFERENCE_TYPE);
417 intype = TYPE_MAIN_VARIANT (intype);
419 can_convert_intype_to_type = can_convert (type, intype);
420 if (!can_convert_intype_to_type
421 && (convtype & CONV_IMPLICIT) && MAYBE_CLASS_TYPE_P (intype)
422 && ! (flags & LOOKUP_NO_CONVERSION))
424 /* Look for a user-defined conversion to lvalue that we can use. */
427 = build_type_conversion (reftype, expr);
429 if (rval_as_conversion && rval_as_conversion != error_mark_node
430 && real_lvalue_p (rval_as_conversion))
432 expr = rval_as_conversion;
433 rval_as_conversion = NULL_TREE;
435 can_convert_intype_to_type = 1;
439 if (((convtype & CONV_STATIC) && can_convert (intype, type))
440 || ((convtype & CONV_IMPLICIT) && can_convert_intype_to_type))
442 if (flags & LOOKUP_COMPLAIN)
444 tree ttl = TREE_TYPE (reftype);
445 tree ttr = lvalue_type (expr);
447 if (! real_lvalue_p (expr))
448 warn_ref_binding (reftype, intype, decl);
450 if (! (convtype & CONV_CONST)
451 && !at_least_as_qualified_p (ttl, ttr))
452 permerror (input_location, "conversion from %qT to %qT discards qualifiers",
456 return build_up_reference (reftype, expr, flags, decl);
458 else if ((convtype & CONV_REINTERPRET) && lvalue_p (expr))
460 /* When casting an lvalue to a reference type, just convert into
461 a pointer to the new type and deference it. This is allowed
462 by San Diego WP section 5.2.9 paragraph 12, though perhaps it
463 should be done directly (jason). (int &)ri ---> *(int*)&ri */
465 /* B* bp; A& ar = (A&)bp; is valid, but it's probably not what they
467 if (TREE_CODE (intype) == POINTER_TYPE
468 && (comptypes (TREE_TYPE (intype), type,
469 COMPARE_BASE | COMPARE_DERIVED)))
470 warning (0, "casting %qT to %qT does not dereference pointer",
473 rval = cp_build_unary_op (ADDR_EXPR, expr, 0, tf_warning_or_error);
474 if (rval != error_mark_node)
475 rval = convert_force (build_pointer_type (TREE_TYPE (reftype)),
477 if (rval != error_mark_node)
478 rval = build1 (NOP_EXPR, reftype, rval);
482 rval = convert_for_initialization (NULL_TREE, type, expr, flags,
484 tf_warning_or_error);
485 if (rval == NULL_TREE || rval == error_mark_node)
487 warn_ref_binding (reftype, intype, decl);
488 rval = build_up_reference (reftype, rval, flags, decl);
493 /* If we found a way to convert earlier, then use it. */
497 if (flags & LOOKUP_COMPLAIN)
498 error ("cannot convert type %qT to type %qT", intype, reftype);
500 return error_mark_node;
503 /* We are using a reference VAL for its value. Bash that reference all the
504 way down to its lowest form. */
507 convert_from_reference (tree val)
509 if (TREE_CODE (TREE_TYPE (val)) == REFERENCE_TYPE)
511 tree t = TREE_TYPE (TREE_TYPE (val));
512 tree ref = build1 (INDIRECT_REF, t, val);
514 /* We *must* set TREE_READONLY when dereferencing a pointer to const,
515 so that we get the proper error message if the result is used
516 to assign to. Also, &* is supposed to be a no-op. */
517 TREE_READONLY (ref) = CP_TYPE_CONST_P (t);
518 TREE_THIS_VOLATILE (ref) = CP_TYPE_VOLATILE_P (t);
519 TREE_SIDE_EFFECTS (ref)
520 = (TREE_THIS_VOLATILE (ref) || TREE_SIDE_EFFECTS (val));
521 REFERENCE_REF_P (ref) = 1;
528 /* Really perform an lvalue-to-rvalue conversion, including copying an
529 argument of class type into a temporary. */
532 force_rvalue (tree expr)
534 if (MAYBE_CLASS_TYPE_P (TREE_TYPE (expr)) && TREE_CODE (expr) != TARGET_EXPR)
535 expr = ocp_convert (TREE_TYPE (expr), expr,
536 CONV_IMPLICIT|CONV_FORCE_TEMP, LOOKUP_NORMAL);
538 expr = decay_conversion (expr);
544 /* Fold away simple conversions, but make sure the result is an rvalue. */
547 cp_fold_convert (tree type, tree expr)
549 return rvalue (fold_convert (type, expr));
552 /* C++ conversions, preference to static cast conversions. */
555 cp_convert (tree type, tree expr)
557 return ocp_convert (type, expr, CONV_OLD_CONVERT, LOOKUP_NORMAL);
560 /* C++ equivalent of convert_and_check but using cp_convert as the
563 Convert EXPR to TYPE, warning about conversion problems with constants.
564 Invoke this function on every expression that is converted implicitly,
565 i.e. because of language rules and not because of an explicit cast. */
568 cp_convert_and_check (tree type, tree expr)
572 if (TREE_TYPE (expr) == type)
575 result = cp_convert (type, expr);
577 if (c_inhibit_evaluation_warnings == 0
578 && !TREE_OVERFLOW_P (expr)
579 && result != error_mark_node)
580 warnings_for_convert_and_check (type, expr, result);
587 FLAGS indicates how we should behave. */
590 ocp_convert (tree type, tree expr, int convtype, int flags)
593 enum tree_code code = TREE_CODE (type);
594 const char *invalid_conv_diag;
597 if (error_operand_p (e) || type == error_mark_node)
598 return error_mark_node;
600 complete_type (type);
601 complete_type (TREE_TYPE (expr));
603 if ((invalid_conv_diag
604 = targetm.invalid_conversion (TREE_TYPE (expr), type)))
606 error (invalid_conv_diag);
607 return error_mark_node;
610 e = integral_constant_value (e);
612 if (MAYBE_CLASS_TYPE_P (type) && (convtype & CONV_FORCE_TEMP))
613 /* We need a new temporary; don't take this shortcut. */;
614 else if (same_type_ignoring_top_level_qualifiers_p (type, TREE_TYPE (e)))
616 if (same_type_p (type, TREE_TYPE (e)))
617 /* The call to fold will not always remove the NOP_EXPR as
618 might be expected, since if one of the types is a typedef;
619 the comparison in fold is just equality of pointers, not a
620 call to comptypes. We don't call fold in this case because
621 that can result in infinite recursion; fold will call
622 convert, which will call ocp_convert, etc. */
624 /* For complex data types, we need to perform componentwise
626 else if (TREE_CODE (type) == COMPLEX_TYPE)
627 return fold_if_not_in_template (convert_to_complex (type, e));
628 else if (TREE_CODE (e) == TARGET_EXPR)
630 /* Don't build a NOP_EXPR of class type. Instead, change the
631 type of the temporary. */
632 TREE_TYPE (e) = TREE_TYPE (TARGET_EXPR_SLOT (e)) = type;
637 /* We shouldn't be treating objects of ADDRESSABLE type as
639 gcc_assert (!TREE_ADDRESSABLE (type));
640 return fold_if_not_in_template (build_nop (type, e));
644 e1 = targetm.convert_to_type (type, e);
648 if (code == VOID_TYPE && (convtype & CONV_STATIC))
650 e = convert_to_void (e, /*implicit=*/NULL, tf_warning_or_error);
654 if (INTEGRAL_CODE_P (code))
656 tree intype = TREE_TYPE (e);
658 if (TREE_CODE (type) == ENUMERAL_TYPE)
660 /* enum = enum, enum = int, enum = float, (enum)pointer are all
662 if (((INTEGRAL_OR_ENUMERATION_TYPE_P (intype)
663 || TREE_CODE (intype) == REAL_TYPE)
664 && ! (convtype & CONV_STATIC))
665 || TREE_CODE (intype) == POINTER_TYPE)
667 if (flags & LOOKUP_COMPLAIN)
668 permerror (input_location, "conversion from %q#T to %q#T", intype, type);
670 if (!flag_permissive)
671 return error_mark_node;
674 /* [expr.static.cast]
676 8. A value of integral or enumeration type can be explicitly
677 converted to an enumeration type. The value is unchanged if
678 the original value is within the range of the enumeration
679 values. Otherwise, the resulting enumeration value is
681 if (TREE_CODE (expr) == INTEGER_CST && !int_fits_type_p (expr, type))
682 warning (OPT_Wconversion,
683 "the result of the conversion is unspecified because "
684 "%qE is outside the range of type %qT",
687 if (MAYBE_CLASS_TYPE_P (intype))
690 rval = build_type_conversion (type, e);
693 if (flags & LOOKUP_COMPLAIN)
694 error ("%q#T used where a %qT was expected", intype, type);
695 return error_mark_node;
697 if (code == BOOLEAN_TYPE)
698 return cp_truthvalue_conversion (e);
700 return fold_if_not_in_template (convert_to_integer (type, e));
702 if (POINTER_TYPE_P (type) || TYPE_PTR_TO_MEMBER_P (type))
703 return fold_if_not_in_template (cp_convert_to_pointer (type, e));
704 if (code == VECTOR_TYPE)
706 tree in_vtype = TREE_TYPE (e);
707 if (MAYBE_CLASS_TYPE_P (in_vtype))
710 ret_val = build_type_conversion (type, e);
713 if (flags & LOOKUP_COMPLAIN)
714 error ("%q#T used where a %qT was expected", in_vtype, type);
715 return error_mark_node;
717 return fold_if_not_in_template (convert_to_vector (type, e));
719 if (code == REAL_TYPE || code == COMPLEX_TYPE)
721 if (MAYBE_CLASS_TYPE_P (TREE_TYPE (e)))
724 rval = build_type_conversion (type, e);
728 if (flags & LOOKUP_COMPLAIN)
729 error ("%q#T used where a floating point value was expected",
732 if (code == REAL_TYPE)
733 return fold_if_not_in_template (convert_to_real (type, e));
734 else if (code == COMPLEX_TYPE)
735 return fold_if_not_in_template (convert_to_complex (type, e));
738 /* New C++ semantics: since assignment is now based on
739 memberwise copying, if the rhs type is derived from the
740 lhs type, then we may still do a conversion. */
741 if (RECORD_OR_UNION_CODE_P (code))
743 tree dtype = TREE_TYPE (e);
744 tree ctor = NULL_TREE;
746 dtype = TYPE_MAIN_VARIANT (dtype);
748 /* Conversion between aggregate types. New C++ semantics allow
749 objects of derived type to be cast to objects of base type.
750 Old semantics only allowed this between pointers.
752 There may be some ambiguity between using a constructor
753 vs. using a type conversion operator when both apply. */
757 if (abstract_virtuals_error (NULL_TREE, type))
758 return error_mark_node;
760 if (BRACE_ENCLOSED_INITIALIZER_P (ctor))
761 ctor = perform_implicit_conversion (type, ctor, tf_warning_or_error);
762 else if ((flags & LOOKUP_ONLYCONVERTING)
763 && ! (CLASS_TYPE_P (dtype) && DERIVED_FROM_P (type, dtype)))
764 /* For copy-initialization, first we create a temp of the proper type
765 with a user-defined conversion sequence, then we direct-initialize
766 the target with the temp (see [dcl.init]). */
767 ctor = build_user_type_conversion (type, ctor, flags);
770 VEC(tree,gc) *ctor_vec = make_tree_vector_single (ctor);
771 ctor = build_special_member_call (NULL_TREE,
772 complete_ctor_identifier,
775 tf_warning_or_error);
776 release_tree_vector (ctor_vec);
779 return build_cplus_new (type, ctor);
782 if (flags & LOOKUP_COMPLAIN)
784 /* If the conversion failed and expr was an invalid use of pointer to
785 member function, try to report a meaningful error. */
786 if (invalid_nonstatic_memfn_p (expr, tf_warning_or_error))
787 /* We displayed the error message. */;
789 error ("conversion from %qT to non-scalar type %qT requested",
790 TREE_TYPE (expr), type);
792 return error_mark_node;
795 /* When an expression is used in a void context, its value is discarded and
796 no lvalue-rvalue and similar conversions happen [expr.static.cast/4,
797 stmt.expr/1, expr.comma/1]. This permits dereferencing an incomplete type
798 in a void context. The C++ standard does not define what an `access' to an
799 object is, but there is reason to believe that it is the lvalue to rvalue
800 conversion -- if it were not, `*&*p = 1' would violate [expr]/4 in that it
801 accesses `*p' not to calculate the value to be stored. But, dcl.type.cv/8
802 indicates that volatile semantics should be the same between C and C++
803 where ever possible. C leaves it implementation defined as to what
804 constitutes an access to a volatile. So, we interpret `*vp' as a read of
805 the volatile object `vp' points to, unless that is an incomplete type. For
806 volatile references we do not do this interpretation, because that would
807 make it impossible to ignore the reference return value from functions. We
808 issue warnings in the confusing cases.
810 IMPLICIT is non-NULL iff an expression is being implicitly converted; it
811 is NULL when the user is explicitly converting an expression to void via
812 a cast. When non-NULL, IMPLICIT is a string indicating the context of
813 the implicit conversion. */
816 convert_to_void (tree expr, const char *implicit, tsubst_flags_t complain)
818 if (expr == error_mark_node
819 || TREE_TYPE (expr) == error_mark_node)
820 return error_mark_node;
821 if (!TREE_TYPE (expr))
823 if (invalid_nonstatic_memfn_p (expr, complain))
824 return error_mark_node;
825 if (TREE_CODE (expr) == PSEUDO_DTOR_EXPR)
827 if (complain & tf_error)
828 error ("pseudo-destructor is not called");
829 return error_mark_node;
831 if (VOID_TYPE_P (TREE_TYPE (expr)))
833 switch (TREE_CODE (expr))
837 /* The two parts of a cond expr might be separate lvalues. */
838 tree op1 = TREE_OPERAND (expr,1);
839 tree op2 = TREE_OPERAND (expr,2);
840 bool side_effects = TREE_SIDE_EFFECTS (op1) || TREE_SIDE_EFFECTS (op2);
841 tree new_op1 = convert_to_void
842 (op1, (implicit && !side_effects
843 ? "second operand of conditional" : NULL), complain);
844 tree new_op2 = convert_to_void
845 (op2, (implicit && !side_effects
846 ? "third operand of conditional" : NULL), complain);
848 expr = build3 (COND_EXPR, TREE_TYPE (new_op1),
849 TREE_OPERAND (expr, 0), new_op1, new_op2);
855 /* The second part of a compound expr contains the value. */
856 tree op1 = TREE_OPERAND (expr,1);
857 tree new_op1 = convert_to_void
858 (op1, (implicit && !TREE_NO_WARNING (expr)
859 ? "right-hand operand of comma" : NULL), complain);
863 tree t = build2 (COMPOUND_EXPR, TREE_TYPE (new_op1),
864 TREE_OPERAND (expr, 0), new_op1);
871 case NON_LVALUE_EXPR:
873 /* These have already decayed to rvalue. */
876 case CALL_EXPR: /* We have a special meaning for volatile void fn(). */
881 tree type = TREE_TYPE (expr);
882 int is_reference = TREE_CODE (TREE_TYPE (TREE_OPERAND (expr, 0)))
884 int is_volatile = TYPE_VOLATILE (type);
885 int is_complete = COMPLETE_TYPE_P (complete_type (type));
887 /* Can't load the value if we don't know the type. */
888 if (is_volatile && !is_complete)
890 if (complain & tf_warning)
891 warning (0, "object of incomplete type %qT will not be accessed in %s",
892 type, implicit ? implicit : "void context");
894 /* Don't load the value if this is an implicit dereference, or if
895 the type needs to be handled by ctors/dtors. */
896 else if (is_volatile && (is_reference || TREE_ADDRESSABLE (type)))
898 if (complain & tf_warning)
899 warning (0, "object of type %qT will not be accessed in %s",
900 TREE_TYPE (TREE_OPERAND (expr, 0)),
901 implicit ? implicit : "void context");
903 if (is_reference || !is_volatile || !is_complete || TREE_ADDRESSABLE (type))
905 /* Emit a warning (if enabled) when the "effect-less" INDIRECT_REF
906 operation is stripped off. Note that we don't warn about
907 - an expression with TREE_NO_WARNING set. (For an example of
908 such expressions, see build_over_call in call.c.)
909 - automatic dereferencing of references, since the user cannot
910 control it. (See also warn_if_unused_value() in stmt.c.) */
911 if (warn_unused_value
913 && (complain & tf_warning)
914 && !TREE_NO_WARNING (expr)
916 warning (OPT_Wunused_value, "value computed is not used");
917 expr = TREE_OPERAND (expr, 0);
925 /* External variables might be incomplete. */
926 tree type = TREE_TYPE (expr);
927 int is_complete = COMPLETE_TYPE_P (complete_type (type));
929 if (TYPE_VOLATILE (type) && !is_complete && (complain & tf_warning))
930 warning (0, "object %qE of incomplete type %qT will not be accessed in %s",
931 expr, type, implicit ? implicit : "void context");
936 /* Don't bother with the temporary object returned from a function if
937 we don't use it and don't need to destroy it. We'll still
938 allocate space for it in expand_call or declare_return_variable,
939 but we don't need to track it through all the tree phases. */
940 if (TARGET_EXPR_IMPLICIT_P (expr)
941 && TYPE_HAS_TRIVIAL_DESTRUCTOR (TREE_TYPE (expr)))
943 tree init = TARGET_EXPR_INITIAL (expr);
944 if (TREE_CODE (init) == AGGR_INIT_EXPR
945 && !AGGR_INIT_VIA_CTOR_P (init))
947 tree fn = AGGR_INIT_EXPR_FN (init);
948 expr = build_call_array_loc (input_location,
949 TREE_TYPE (TREE_TYPE (TREE_TYPE (fn))),
951 aggr_init_expr_nargs (init),
952 AGGR_INIT_EXPR_ARGP (init));
962 if (TREE_CODE (probe) == ADDR_EXPR)
963 probe = TREE_OPERAND (expr, 0);
964 if (type_unknown_p (probe))
966 /* [over.over] enumerates the places where we can take the address
967 of an overloaded function, and this is not one of them. */
968 if (complain & tf_error)
969 error ("%s cannot resolve address of overloaded function",
970 implicit ? implicit : "void cast");
972 return error_mark_node;
973 expr = void_zero_node;
975 else if (implicit && probe == expr && is_overloaded_fn (probe))
977 /* Only warn when there is no &. */
978 if (complain & tf_warning)
979 warning (OPT_Waddress, "%s is a reference, not call, to function %qE",
981 if (TREE_CODE (expr) == COMPONENT_REF)
982 expr = TREE_OPERAND (expr, 0);
986 if (expr != error_mark_node && !VOID_TYPE_P (TREE_TYPE (expr)))
990 && !TREE_NO_WARNING (expr)
991 && !processing_template_decl)
993 /* The middle end does not warn about expressions that have
994 been explicitly cast to void, so we must do so here. */
995 if (!TREE_SIDE_EFFECTS (expr)) {
996 if (complain & tf_warning)
997 warning (OPT_Wunused_value, "%s has no effect", implicit);
1002 enum tree_code code;
1003 enum tree_code_class tclass;
1006 /* We might like to warn about (say) "(int) f()", as the
1007 cast has no effect, but the compiler itself will
1008 generate implicit conversions under some
1009 circumstances. (For example a block copy will be
1010 turned into a call to "__builtin_memcpy", with a
1011 conversion of the return value to an appropriate
1012 type.) So, to avoid false positives, we strip
1013 conversions. Do not use STRIP_NOPs because it will
1014 not strip conversions to "void", as that is not a
1015 mode-preserving conversion. */
1016 while (TREE_CODE (e) == NOP_EXPR)
1017 e = TREE_OPERAND (e, 0);
1019 code = TREE_CODE (e);
1020 tclass = TREE_CODE_CLASS (code);
1021 if ((tclass == tcc_comparison
1022 || tclass == tcc_unary
1023 || (tclass == tcc_binary
1024 && !(code == MODIFY_EXPR
1025 || code == INIT_EXPR
1026 || code == PREDECREMENT_EXPR
1027 || code == PREINCREMENT_EXPR
1028 || code == POSTDECREMENT_EXPR
1029 || code == POSTINCREMENT_EXPR)))
1030 && (complain & tf_warning))
1031 warning (OPT_Wunused_value, "value computed is not used");
1034 expr = build1 (CONVERT_EXPR, void_type_node, expr);
1036 if (! TREE_SIDE_EFFECTS (expr))
1037 expr = void_zero_node;
1041 /* Create an expression whose value is that of EXPR,
1042 converted to type TYPE. The TREE_TYPE of the value
1043 is always TYPE. This function implements all reasonable
1044 conversions; callers should filter out those that are
1045 not permitted by the language being compiled.
1047 Most of this routine is from build_reinterpret_cast.
1049 The back end cannot call cp_convert (what was convert) because
1050 conversions to/from basetypes may involve memory references
1051 (vbases) and adding or subtracting small values (multiple
1052 inheritance), but it calls convert from the constant folding code
1053 on subtrees of already built trees after it has ripped them apart.
1055 Also, if we ever support range variables, we'll probably also have to
1056 do a little bit more work. */
1059 convert (tree type, tree expr)
1063 if (type == error_mark_node || expr == error_mark_node)
1064 return error_mark_node;
1066 intype = TREE_TYPE (expr);
1068 if (POINTER_TYPE_P (type) && POINTER_TYPE_P (intype))
1069 return fold_if_not_in_template (build_nop (type, expr));
1071 return ocp_convert (type, expr, CONV_OLD_CONVERT,
1072 LOOKUP_NORMAL|LOOKUP_NO_CONVERSION);
1075 /* Like cp_convert, except permit conversions to take place which
1076 are not normally allowed due to access restrictions
1077 (such as conversion from sub-type to private super-type). */
1080 convert_force (tree type, tree expr, int convtype)
1083 enum tree_code code = TREE_CODE (type);
1085 if (code == REFERENCE_TYPE)
1086 return (fold_if_not_in_template
1087 (convert_to_reference (type, e, CONV_C_CAST, LOOKUP_COMPLAIN,
1090 if (code == POINTER_TYPE)
1091 return fold_if_not_in_template (convert_to_pointer_force (type, e));
1093 /* From typeck.c convert_for_assignment */
1094 if (((TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE && TREE_CODE (e) == ADDR_EXPR
1095 && TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE
1096 && TREE_CODE (TREE_TYPE (TREE_TYPE (e))) == METHOD_TYPE)
1097 || integer_zerop (e)
1098 || TYPE_PTRMEMFUNC_P (TREE_TYPE (e)))
1099 && TYPE_PTRMEMFUNC_P (type))
1100 /* compatible pointer to member functions. */
1101 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), e, 1,
1104 return ocp_convert (type, e, CONV_C_CAST|convtype, LOOKUP_NORMAL);
1107 /* Convert an aggregate EXPR to type XTYPE. If a conversion
1108 exists, return the attempted conversion. This may
1109 return ERROR_MARK_NODE if the conversion is not
1110 allowed (references private members, etc).
1111 If no conversion exists, NULL_TREE is returned.
1113 FIXME: Ambiguity checking is wrong. Should choose one by the implicit
1114 object parameter, or by the second standard conversion sequence if
1115 that doesn't do it. This will probably wait for an overloading rewrite.
1119 build_type_conversion (tree xtype, tree expr)
1121 /* C++: check to see if we can convert this aggregate type
1122 into the required type. */
1123 return build_user_type_conversion (xtype, expr, LOOKUP_NORMAL);
1126 /* Convert the given EXPR to one of a group of types suitable for use in an
1127 expression. DESIRES is a combination of various WANT_* flags (q.v.)
1128 which indicates which types are suitable. If COMPLAIN is true, complain
1129 about ambiguity; otherwise, the caller will deal with it. */
1132 build_expr_type_conversion (int desires, tree expr, bool complain)
1134 tree basetype = TREE_TYPE (expr);
1135 tree conv = NULL_TREE;
1136 tree winner = NULL_TREE;
1138 if (expr == null_node
1139 && (desires & WANT_INT)
1140 && !(desires & WANT_NULL))
1141 warning (OPT_Wconversion, "converting NULL to non-pointer type");
1143 basetype = TREE_TYPE (expr);
1145 if (basetype == error_mark_node)
1146 return error_mark_node;
1148 if (! MAYBE_CLASS_TYPE_P (basetype))
1149 switch (TREE_CODE (basetype))
1152 if ((desires & WANT_NULL) && null_ptr_cst_p (expr))
1154 /* else fall through... */
1157 return (desires & WANT_INT) ? expr : NULL_TREE;
1159 return (desires & WANT_ENUM) ? expr : NULL_TREE;
1161 return (desires & WANT_FLOAT) ? expr : NULL_TREE;
1163 return (desires & WANT_POINTER) ? expr : NULL_TREE;
1167 return (desires & WANT_POINTER) ? decay_conversion (expr)
1171 if ((desires & WANT_VECTOR) == 0)
1173 switch (TREE_CODE (TREE_TYPE (basetype)))
1177 return (desires & WANT_INT) ? expr : NULL_TREE;
1179 return (desires & WANT_ENUM) ? expr : NULL_TREE;
1181 return (desires & WANT_FLOAT) ? expr : NULL_TREE;
1190 /* The code for conversions from class type is currently only used for
1191 delete expressions. Other expressions are handled by build_new_op. */
1192 if (!complete_type_or_else (basetype, expr))
1193 return error_mark_node;
1194 if (!TYPE_HAS_CONVERSION (basetype))
1197 for (conv = lookup_conversions (basetype); conv; conv = TREE_CHAIN (conv))
1201 tree cand = TREE_VALUE (conv);
1203 if (winner && winner == cand)
1206 if (DECL_NONCONVERTING_P (cand))
1209 candidate = non_reference (TREE_TYPE (TREE_TYPE (cand)));
1211 switch (TREE_CODE (candidate))
1215 win = (desires & WANT_INT); break;
1217 win = (desires & WANT_ENUM); break;
1219 win = (desires & WANT_FLOAT); break;
1221 win = (desires & WANT_POINTER); break;
1224 if ((desires & WANT_VECTOR) == 0)
1226 switch (TREE_CODE (TREE_TYPE (candidate)))
1230 win = (desires & WANT_INT); break;
1232 win = (desires & WANT_ENUM); break;
1234 win = (desires & WANT_FLOAT); break;
1250 error ("ambiguous default type conversion from %qT",
1252 error (" candidate conversions include %qD and %qD",
1255 return error_mark_node;
1264 tree type = non_reference (TREE_TYPE (TREE_TYPE (winner)));
1265 return build_user_type_conversion (type, expr, LOOKUP_NORMAL);
1271 /* Implements integral promotion (4.1) and float->double promotion. */
1274 type_promotes_to (tree type)
1278 if (type == error_mark_node)
1279 return error_mark_node;
1281 type = TYPE_MAIN_VARIANT (type);
1283 /* Check for promotions of target-defined types first. */
1284 promoted_type = targetm.promoted_type (type);
1286 return promoted_type;
1288 /* bool always promotes to int (not unsigned), even if it's the same
1290 if (type == boolean_type_node)
1291 type = integer_type_node;
1293 /* Normally convert enums to int, but convert wide enums to something
1295 else if (TREE_CODE (type) == ENUMERAL_TYPE
1296 || type == char16_type_node
1297 || type == char32_type_node
1298 || type == wchar_type_node)
1300 int precision = MAX (TYPE_PRECISION (type),
1301 TYPE_PRECISION (integer_type_node));
1302 tree totype = c_common_type_for_size (precision, 0);
1303 if (TYPE_UNSIGNED (type)
1304 && ! int_fits_type_p (TYPE_MAX_VALUE (type), totype))
1305 type = c_common_type_for_size (precision, 1);
1309 else if (c_promoting_integer_type_p (type))
1311 /* Retain unsignedness if really not getting bigger. */
1312 if (TYPE_UNSIGNED (type)
1313 && TYPE_PRECISION (type) == TYPE_PRECISION (integer_type_node))
1314 type = unsigned_type_node;
1316 type = integer_type_node;
1318 else if (type == float_type_node)
1319 type = double_type_node;
1324 /* The routines below this point are carefully written to conform to
1325 the standard. They use the same terminology, and follow the rules
1326 closely. Although they are used only in pt.c at the moment, they
1327 should presumably be used everywhere in the future. */
1329 /* Attempt to perform qualification conversions on EXPR to convert it
1330 to TYPE. Return the resulting expression, or error_mark_node if
1331 the conversion was impossible. */
1334 perform_qualification_conversions (tree type, tree expr)
1338 expr_type = TREE_TYPE (expr);
1340 if (same_type_p (type, expr_type))
1342 else if (TYPE_PTR_P (type) && TYPE_PTR_P (expr_type)
1343 && comp_ptr_ttypes (TREE_TYPE (type), TREE_TYPE (expr_type)))
1344 return build_nop (type, expr);
1345 else if (TYPE_PTR_TO_MEMBER_P (type)
1346 && TYPE_PTR_TO_MEMBER_P (expr_type)
1347 && same_type_p (TYPE_PTRMEM_CLASS_TYPE (type),
1348 TYPE_PTRMEM_CLASS_TYPE (expr_type))
1349 && comp_ptr_ttypes (TYPE_PTRMEM_POINTED_TO_TYPE (type),
1350 TYPE_PTRMEM_POINTED_TO_TYPE (expr_type)))
1351 return build_nop (type, expr);
1353 return error_mark_node;