1 /* Language-level data type conversion for GNU C++.
2 Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
3 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
4 Free Software Foundation, Inc.
5 Hacked by Michael Tiemann (tiemann@cygnus.com)
7 This file is part of GCC.
9 GCC is free software; you can redistribute it and/or modify
10 it under the terms of the GNU General Public License as published by
11 the Free Software Foundation; either version 3, or (at your option)
14 GCC is distributed in the hope that it will be useful,
15 but WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License for more details.
19 You should have received a copy of the GNU General Public License
20 along with GCC; see the file COPYING3. If not see
21 <http://www.gnu.org/licenses/>. */
24 /* This file contains the functions for converting C++ expressions
25 to different data types. The only entry point is `convert'.
26 Every language front end must have a `convert' function
27 but what kind of conversions it does will depend on the language. */
31 #include "coretypes.h"
41 static tree cp_convert_to_pointer (tree, tree);
42 static tree convert_to_pointer_force (tree, tree);
43 static tree build_type_conversion (tree, tree);
44 static tree build_up_reference (tree, tree, int, tree);
45 static void warn_ref_binding (tree, tree, tree);
47 /* Change of width--truncation and extension of integers or reals--
48 is represented with NOP_EXPR. Proper functioning of many things
49 assumes that no other conversions can be NOP_EXPRs.
51 Conversion between integer and pointer is represented with CONVERT_EXPR.
52 Converting integer to real uses FLOAT_EXPR
53 and real to integer uses FIX_TRUNC_EXPR.
55 Here is a list of all the functions that assume that widening and
56 narrowing is always done with a NOP_EXPR:
57 In convert.c, convert_to_integer.
58 In c-typeck.c, build_binary_op_nodefault (boolean ops),
59 and c_common_truthvalue_conversion.
60 In expr.c: expand_expr, for operands of a MULT_EXPR.
61 In fold-const.c: fold.
62 In tree.c: get_narrower and get_unwidened.
64 C++: in multiple-inheritance, converting between pointers may involve
65 adjusting them by a delta stored within the class definition. */
67 /* Subroutines of `convert'. */
69 /* if converting pointer to pointer
70 if dealing with classes, check for derived->base or vice versa
71 else if dealing with method pointers, delegate
73 else if converting class, pass off to build_type_conversion
74 else try C-style pointer conversion. */
77 cp_convert_to_pointer (tree type, tree expr)
79 tree intype = TREE_TYPE (expr);
82 if (intype == error_mark_node)
83 return error_mark_node;
85 if (MAYBE_CLASS_TYPE_P (intype))
87 intype = complete_type (intype);
88 if (!COMPLETE_TYPE_P (intype))
90 error ("can't convert from incomplete type %qT to %qT",
92 return error_mark_node;
95 rval = build_type_conversion (type, expr);
98 if (rval == error_mark_node)
99 error ("conversion of %qE from %qT to %qT is ambiguous",
105 /* Handle anachronistic conversions from (::*)() to cv void* or (*)(). */
106 if (TREE_CODE (type) == POINTER_TYPE
107 && (TREE_CODE (TREE_TYPE (type)) == FUNCTION_TYPE
108 || VOID_TYPE_P (TREE_TYPE (type))))
110 if (TYPE_PTRMEMFUNC_P (intype)
111 || TREE_CODE (intype) == METHOD_TYPE)
112 return convert_member_func_to_ptr (type, expr);
113 if (TREE_CODE (TREE_TYPE (expr)) == POINTER_TYPE)
114 return build_nop (type, expr);
115 intype = TREE_TYPE (expr);
118 if (expr == error_mark_node)
119 return error_mark_node;
121 form = TREE_CODE (intype);
123 if (POINTER_TYPE_P (intype))
125 intype = TYPE_MAIN_VARIANT (intype);
127 if (TYPE_MAIN_VARIANT (type) != intype
128 && TREE_CODE (type) == POINTER_TYPE
129 && TREE_CODE (TREE_TYPE (type)) == RECORD_TYPE
130 && MAYBE_CLASS_TYPE_P (TREE_TYPE (type))
131 && MAYBE_CLASS_TYPE_P (TREE_TYPE (intype))
132 && TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE)
134 enum tree_code code = PLUS_EXPR;
140 intype_class = TREE_TYPE (intype);
141 type_class = TREE_TYPE (type);
143 same_p = same_type_p (TYPE_MAIN_VARIANT (intype_class),
144 TYPE_MAIN_VARIANT (type_class));
146 /* Try derived to base conversion. */
148 binfo = lookup_base (intype_class, type_class, ba_check, NULL);
149 if (!same_p && !binfo)
151 /* Try base to derived conversion. */
152 binfo = lookup_base (type_class, intype_class, ba_check, NULL);
155 if (binfo == error_mark_node)
156 return error_mark_node;
160 expr = build_base_path (code, expr, binfo, 0);
161 /* Add any qualifier conversions. */
162 return build_nop (type, expr);
166 if (TYPE_PTRMEMFUNC_P (type))
168 error ("cannot convert %qE from type %qT to type %qT",
170 return error_mark_node;
173 return build_nop (type, expr);
175 else if ((TYPE_PTRMEM_P (type) && TYPE_PTRMEM_P (intype))
176 || (TYPE_PTRMEMFUNC_P (type) && TYPE_PTRMEMFUNC_P (intype)))
177 return convert_ptrmem (type, expr, /*allow_inverse_p=*/false,
179 else if (TYPE_PTRMEMFUNC_P (intype))
183 if (TREE_CODE (expr) == PTRMEM_CST)
184 return cp_convert_to_pointer (type,
185 PTRMEM_CST_MEMBER (expr));
186 else if (TREE_CODE (expr) == OFFSET_REF)
188 tree object = TREE_OPERAND (expr, 0);
189 return get_member_function_from_ptrfunc (&object,
190 TREE_OPERAND (expr, 1));
193 error ("cannot convert %qE from type %qT to type %qT",
195 return error_mark_node;
198 if (integer_zerop (expr))
200 if (TYPE_PTRMEMFUNC_P (type))
201 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), expr, 0,
204 if (TYPE_PTRMEM_P (type))
206 /* A NULL pointer-to-member is represented by -1, not by
208 expr = build_int_cst_type (type, -1);
211 expr = build_int_cst (type, 0);
215 else if (TYPE_PTR_TO_MEMBER_P (type) && INTEGRAL_CODE_P (form))
217 error ("invalid conversion from %qT to %qT", intype, type);
218 return error_mark_node;
221 if (INTEGRAL_CODE_P (form))
223 if (TYPE_PRECISION (intype) == POINTER_SIZE)
224 return build1 (CONVERT_EXPR, type, expr);
225 expr = cp_convert (c_common_type_for_size (POINTER_SIZE, 0), expr);
226 /* Modes may be different but sizes should be the same. There
227 is supposed to be some integral type that is the same width
229 gcc_assert (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (expr)))
230 == GET_MODE_SIZE (TYPE_MODE (type)));
232 return convert_to_pointer (type, expr);
235 if (type_unknown_p (expr))
236 return instantiate_type (type, expr, tf_warning_or_error);
238 error ("cannot convert %qE from type %qT to type %qT",
240 return error_mark_node;
243 /* Like convert, except permit conversions to take place which
244 are not normally allowed due to access restrictions
245 (such as conversion from sub-type to private super-type). */
248 convert_to_pointer_force (tree type, tree expr)
250 tree intype = TREE_TYPE (expr);
251 enum tree_code form = TREE_CODE (intype);
253 if (form == POINTER_TYPE)
255 intype = TYPE_MAIN_VARIANT (intype);
257 if (TYPE_MAIN_VARIANT (type) != intype
258 && TREE_CODE (TREE_TYPE (type)) == RECORD_TYPE
259 && MAYBE_CLASS_TYPE_P (TREE_TYPE (type))
260 && MAYBE_CLASS_TYPE_P (TREE_TYPE (intype))
261 && TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE)
263 enum tree_code code = PLUS_EXPR;
266 binfo = lookup_base (TREE_TYPE (intype), TREE_TYPE (type),
270 binfo = lookup_base (TREE_TYPE (type), TREE_TYPE (intype),
274 if (binfo == error_mark_node)
275 return error_mark_node;
278 expr = build_base_path (code, expr, binfo, 0);
279 if (expr == error_mark_node)
280 return error_mark_node;
281 /* Add any qualifier conversions. */
282 if (!same_type_p (TREE_TYPE (TREE_TYPE (expr)),
284 expr = build_nop (type, expr);
290 return cp_convert_to_pointer (type, expr);
293 /* We are passing something to a function which requires a reference.
294 The type we are interested in is in TYPE. The initial
295 value we have to begin with is in ARG.
297 FLAGS controls how we manage access checking.
298 DIRECT_BIND in FLAGS controls how any temporaries are generated.
299 If DIRECT_BIND is set, DECL is the reference we're binding to. */
302 build_up_reference (tree type, tree arg, int flags, tree decl)
305 tree argtype = TREE_TYPE (arg);
306 tree target_type = TREE_TYPE (type);
308 gcc_assert (TREE_CODE (type) == REFERENCE_TYPE);
310 if ((flags & DIRECT_BIND) && ! real_lvalue_p (arg))
312 /* Create a new temporary variable. We can't just use a TARGET_EXPR
313 here because it needs to live as long as DECL. */
316 arg = make_temporary_var_for_ref_to_temp (decl, TREE_TYPE (arg));
318 /* Process the initializer for the declaration. */
319 DECL_INITIAL (arg) = targ;
320 cp_finish_decl (arg, targ, /*init_const_expr_p=*/false, NULL_TREE,
321 LOOKUP_ONLYCONVERTING|DIRECT_BIND);
323 else if (!(flags & DIRECT_BIND) && ! lvalue_p (arg))
324 return get_target_expr (arg);
326 /* If we had a way to wrap this up, and say, if we ever needed its
327 address, transform all occurrences of the register, into a memory
328 reference we could win better. */
329 rval = cp_build_unary_op (ADDR_EXPR, arg, 1, tf_warning_or_error);
330 if (rval == error_mark_node)
331 return error_mark_node;
333 if ((flags & LOOKUP_PROTECT)
334 && TYPE_MAIN_VARIANT (argtype) != TYPE_MAIN_VARIANT (target_type)
335 && MAYBE_CLASS_TYPE_P (argtype)
336 && MAYBE_CLASS_TYPE_P (target_type))
338 /* We go through lookup_base for the access control. */
339 tree binfo = lookup_base (argtype, target_type, ba_check, NULL);
340 if (binfo == error_mark_node)
341 return error_mark_node;
342 if (binfo == NULL_TREE)
343 return error_not_base_type (target_type, argtype);
344 rval = build_base_path (PLUS_EXPR, rval, binfo, 1);
348 = convert_to_pointer_force (build_pointer_type (target_type), rval);
349 return build_nop (type, rval);
352 /* Subroutine of convert_to_reference. REFTYPE is the target reference type.
353 INTYPE is the original rvalue type and DECL is an optional _DECL node
356 [dcl.init.ref] says that if an rvalue is used to
357 initialize a reference, then the reference must be to a
358 non-volatile const type. */
361 warn_ref_binding (tree reftype, tree intype, tree decl)
363 tree ttl = TREE_TYPE (reftype);
365 if (!CP_TYPE_CONST_NON_VOLATILE_P (ttl))
369 if (CP_TYPE_VOLATILE_P (ttl) && decl)
370 msg = "initialization of volatile reference type %q#T from"
371 " rvalue of type %qT";
372 else if (CP_TYPE_VOLATILE_P (ttl))
373 msg = "conversion to volatile reference type %q#T "
374 " from rvalue of type %qT";
376 msg = "initialization of non-const reference type %q#T from"
377 " rvalue of type %qT";
379 msg = "conversion to non-const reference type %q#T from"
380 " rvalue of type %qT";
382 permerror (input_location, msg, reftype, intype);
386 /* For C++: Only need to do one-level references, but cannot
387 get tripped up on signed/unsigned differences.
389 DECL is either NULL_TREE or the _DECL node for a reference that is being
390 initialized. It can be error_mark_node if we don't know the _DECL but
391 we know it's an initialization. */
394 convert_to_reference (tree reftype, tree expr, int convtype,
395 int flags, tree decl)
397 tree type = TYPE_MAIN_VARIANT (TREE_TYPE (reftype));
399 tree rval = NULL_TREE;
400 tree rval_as_conversion = NULL_TREE;
401 bool can_convert_intype_to_type;
403 if (TREE_CODE (type) == FUNCTION_TYPE
404 && TREE_TYPE (expr) == unknown_type_node)
405 expr = instantiate_type (type, expr,
406 (flags & LOOKUP_COMPLAIN)
407 ? tf_warning_or_error : tf_none);
409 if (expr == error_mark_node)
410 return error_mark_node;
412 intype = TREE_TYPE (expr);
414 gcc_assert (TREE_CODE (intype) != REFERENCE_TYPE);
415 gcc_assert (TREE_CODE (reftype) == REFERENCE_TYPE);
417 intype = TYPE_MAIN_VARIANT (intype);
419 can_convert_intype_to_type = can_convert (type, intype);
420 if (!can_convert_intype_to_type
421 && (convtype & CONV_IMPLICIT) && MAYBE_CLASS_TYPE_P (intype)
422 && ! (flags & LOOKUP_NO_CONVERSION))
424 /* Look for a user-defined conversion to lvalue that we can use. */
427 = build_type_conversion (reftype, expr);
429 if (rval_as_conversion && rval_as_conversion != error_mark_node
430 && real_lvalue_p (rval_as_conversion))
432 expr = rval_as_conversion;
433 rval_as_conversion = NULL_TREE;
435 can_convert_intype_to_type = 1;
439 if (((convtype & CONV_STATIC) && can_convert (intype, type))
440 || ((convtype & CONV_IMPLICIT) && can_convert_intype_to_type))
442 if (flags & LOOKUP_COMPLAIN)
444 tree ttl = TREE_TYPE (reftype);
445 tree ttr = lvalue_type (expr);
447 if (! real_lvalue_p (expr))
448 warn_ref_binding (reftype, intype, decl);
450 if (! (convtype & CONV_CONST)
451 && !at_least_as_qualified_p (ttl, ttr))
452 permerror (input_location, "conversion from %qT to %qT discards qualifiers",
456 return build_up_reference (reftype, expr, flags, decl);
458 else if ((convtype & CONV_REINTERPRET) && lvalue_p (expr))
460 /* When casting an lvalue to a reference type, just convert into
461 a pointer to the new type and deference it. This is allowed
462 by San Diego WP section 5.2.9 paragraph 12, though perhaps it
463 should be done directly (jason). (int &)ri ---> *(int*)&ri */
465 /* B* bp; A& ar = (A&)bp; is valid, but it's probably not what they
467 if (TREE_CODE (intype) == POINTER_TYPE
468 && (comptypes (TREE_TYPE (intype), type,
469 COMPARE_BASE | COMPARE_DERIVED)))
470 warning (0, "casting %qT to %qT does not dereference pointer",
473 rval = cp_build_unary_op (ADDR_EXPR, expr, 0, tf_warning_or_error);
474 if (rval != error_mark_node)
475 rval = convert_force (build_pointer_type (TREE_TYPE (reftype)),
477 if (rval != error_mark_node)
478 rval = build1 (NOP_EXPR, reftype, rval);
482 rval = convert_for_initialization (NULL_TREE, type, expr, flags,
484 tf_warning_or_error);
485 if (rval == NULL_TREE || rval == error_mark_node)
487 warn_ref_binding (reftype, intype, decl);
488 rval = build_up_reference (reftype, rval, flags, decl);
493 /* If we found a way to convert earlier, then use it. */
497 if (flags & LOOKUP_COMPLAIN)
498 error ("cannot convert type %qT to type %qT", intype, reftype);
500 return error_mark_node;
503 /* We are using a reference VAL for its value. Bash that reference all the
504 way down to its lowest form. */
507 convert_from_reference (tree val)
509 if (TREE_CODE (TREE_TYPE (val)) == REFERENCE_TYPE)
511 tree t = TREE_TYPE (TREE_TYPE (val));
512 tree ref = build1 (INDIRECT_REF, t, val);
514 /* We *must* set TREE_READONLY when dereferencing a pointer to const,
515 so that we get the proper error message if the result is used
516 to assign to. Also, &* is supposed to be a no-op. */
517 TREE_READONLY (ref) = CP_TYPE_CONST_P (t);
518 TREE_THIS_VOLATILE (ref) = CP_TYPE_VOLATILE_P (t);
519 TREE_SIDE_EFFECTS (ref)
520 = (TREE_THIS_VOLATILE (ref) || TREE_SIDE_EFFECTS (val));
521 REFERENCE_REF_P (ref) = 1;
528 /* Really perform an lvalue-to-rvalue conversion, including copying an
529 argument of class type into a temporary. */
532 force_rvalue (tree expr)
534 if (MAYBE_CLASS_TYPE_P (TREE_TYPE (expr)) && TREE_CODE (expr) != TARGET_EXPR)
535 expr = ocp_convert (TREE_TYPE (expr), expr,
536 CONV_IMPLICIT|CONV_FORCE_TEMP, LOOKUP_NORMAL);
538 expr = decay_conversion (expr);
543 /* C++ conversions, preference to static cast conversions. */
546 cp_convert (tree type, tree expr)
548 return ocp_convert (type, expr, CONV_OLD_CONVERT, LOOKUP_NORMAL);
551 /* C++ equivalent of convert_and_check but using cp_convert as the
554 Convert EXPR to TYPE, warning about conversion problems with constants.
555 Invoke this function on every expression that is converted implicitly,
556 i.e. because of language rules and not because of an explicit cast. */
559 cp_convert_and_check (tree type, tree expr)
563 if (TREE_TYPE (expr) == type)
566 result = cp_convert (type, expr);
568 if (!skip_evaluation && !TREE_OVERFLOW_P (expr) && result != error_mark_node)
569 warnings_for_convert_and_check (type, expr, result);
576 FLAGS indicates how we should behave. */
579 ocp_convert (tree type, tree expr, int convtype, int flags)
582 enum tree_code code = TREE_CODE (type);
583 const char *invalid_conv_diag;
586 if (error_operand_p (e) || type == error_mark_node)
587 return error_mark_node;
589 complete_type (type);
590 complete_type (TREE_TYPE (expr));
592 if ((invalid_conv_diag
593 = targetm.invalid_conversion (TREE_TYPE (expr), type)))
595 error (invalid_conv_diag);
596 return error_mark_node;
599 e = integral_constant_value (e);
601 if (MAYBE_CLASS_TYPE_P (type) && (convtype & CONV_FORCE_TEMP))
602 /* We need a new temporary; don't take this shortcut. */;
603 else if (same_type_ignoring_top_level_qualifiers_p (type, TREE_TYPE (e)))
605 if (same_type_p (type, TREE_TYPE (e)))
606 /* The call to fold will not always remove the NOP_EXPR as
607 might be expected, since if one of the types is a typedef;
608 the comparison in fold is just equality of pointers, not a
609 call to comptypes. We don't call fold in this case because
610 that can result in infinite recursion; fold will call
611 convert, which will call ocp_convert, etc. */
613 /* For complex data types, we need to perform componentwise
615 else if (TREE_CODE (type) == COMPLEX_TYPE)
616 return fold_if_not_in_template (convert_to_complex (type, e));
617 else if (TREE_CODE (e) == TARGET_EXPR)
619 /* Don't build a NOP_EXPR of class type. Instead, change the
620 type of the temporary. */
621 TREE_TYPE (e) = TREE_TYPE (TARGET_EXPR_SLOT (e)) = type;
626 /* We shouldn't be treating objects of ADDRESSABLE type as
628 gcc_assert (!TREE_ADDRESSABLE (type));
629 return fold_if_not_in_template (build_nop (type, e));
633 e1 = targetm.convert_to_type (type, e);
637 if (code == VOID_TYPE && (convtype & CONV_STATIC))
639 e = convert_to_void (e, /*implicit=*/NULL, tf_warning_or_error);
643 if (INTEGRAL_CODE_P (code))
645 tree intype = TREE_TYPE (e);
647 if (TREE_CODE (type) == ENUMERAL_TYPE)
649 /* enum = enum, enum = int, enum = float, (enum)pointer are all
651 if (((INTEGRAL_OR_ENUMERATION_TYPE_P (intype)
652 || TREE_CODE (intype) == REAL_TYPE)
653 && ! (convtype & CONV_STATIC))
654 || TREE_CODE (intype) == POINTER_TYPE)
656 if (flags & LOOKUP_COMPLAIN)
657 permerror (input_location, "conversion from %q#T to %q#T", intype, type);
659 if (!flag_permissive)
660 return error_mark_node;
663 /* [expr.static.cast]
665 8. A value of integral or enumeration type can be explicitly
666 converted to an enumeration type. The value is unchanged if
667 the original value is within the range of the enumeration
668 values. Otherwise, the resulting enumeration value is
670 if (TREE_CODE (expr) == INTEGER_CST && !int_fits_type_p (expr, type))
671 warning (OPT_Wconversion,
672 "the result of the conversion is unspecified because "
673 "%qE is outside the range of type %qT",
676 if (MAYBE_CLASS_TYPE_P (intype))
679 rval = build_type_conversion (type, e);
682 if (flags & LOOKUP_COMPLAIN)
683 error ("%q#T used where a %qT was expected", intype, type);
684 return error_mark_node;
686 if (code == BOOLEAN_TYPE)
687 return cp_truthvalue_conversion (e);
689 return fold_if_not_in_template (convert_to_integer (type, e));
691 if (POINTER_TYPE_P (type) || TYPE_PTR_TO_MEMBER_P (type))
692 return fold_if_not_in_template (cp_convert_to_pointer (type, e));
693 if (code == VECTOR_TYPE)
695 tree in_vtype = TREE_TYPE (e);
696 if (MAYBE_CLASS_TYPE_P (in_vtype))
699 ret_val = build_type_conversion (type, e);
702 if (flags & LOOKUP_COMPLAIN)
703 error ("%q#T used where a %qT was expected", in_vtype, type);
704 return error_mark_node;
706 return fold_if_not_in_template (convert_to_vector (type, e));
708 if (code == REAL_TYPE || code == COMPLEX_TYPE)
710 if (MAYBE_CLASS_TYPE_P (TREE_TYPE (e)))
713 rval = build_type_conversion (type, e);
717 if (flags & LOOKUP_COMPLAIN)
718 error ("%q#T used where a floating point value was expected",
721 if (code == REAL_TYPE)
722 return fold_if_not_in_template (convert_to_real (type, e));
723 else if (code == COMPLEX_TYPE)
724 return fold_if_not_in_template (convert_to_complex (type, e));
727 /* New C++ semantics: since assignment is now based on
728 memberwise copying, if the rhs type is derived from the
729 lhs type, then we may still do a conversion. */
730 if (RECORD_OR_UNION_CODE_P (code))
732 tree dtype = TREE_TYPE (e);
733 tree ctor = NULL_TREE;
735 dtype = TYPE_MAIN_VARIANT (dtype);
737 /* Conversion between aggregate types. New C++ semantics allow
738 objects of derived type to be cast to objects of base type.
739 Old semantics only allowed this between pointers.
741 There may be some ambiguity between using a constructor
742 vs. using a type conversion operator when both apply. */
746 if (abstract_virtuals_error (NULL_TREE, type))
747 return error_mark_node;
749 if (BRACE_ENCLOSED_INITIALIZER_P (ctor))
750 ctor = perform_implicit_conversion (type, ctor, tf_warning_or_error);
751 else if ((flags & LOOKUP_ONLYCONVERTING)
752 && ! (CLASS_TYPE_P (dtype) && DERIVED_FROM_P (type, dtype)))
753 /* For copy-initialization, first we create a temp of the proper type
754 with a user-defined conversion sequence, then we direct-initialize
755 the target with the temp (see [dcl.init]). */
756 ctor = build_user_type_conversion (type, ctor, flags);
759 VEC(tree,gc) *ctor_vec = make_tree_vector_single (ctor);
760 ctor = build_special_member_call (NULL_TREE,
761 complete_ctor_identifier,
764 tf_warning_or_error);
765 release_tree_vector (ctor_vec);
768 return build_cplus_new (type, ctor);
771 if (flags & LOOKUP_COMPLAIN)
773 /* If the conversion failed and expr was an invalid use of pointer to
774 member function, try to report a meaningful error. */
775 if (invalid_nonstatic_memfn_p (expr, tf_warning_or_error))
776 /* We displayed the error message. */;
778 error ("conversion from %qT to non-scalar type %qT requested",
779 TREE_TYPE (expr), type);
781 return error_mark_node;
784 /* When an expression is used in a void context, its value is discarded and
785 no lvalue-rvalue and similar conversions happen [expr.static.cast/4,
786 stmt.expr/1, expr.comma/1]. This permits dereferencing an incomplete type
787 in a void context. The C++ standard does not define what an `access' to an
788 object is, but there is reason to believe that it is the lvalue to rvalue
789 conversion -- if it were not, `*&*p = 1' would violate [expr]/4 in that it
790 accesses `*p' not to calculate the value to be stored. But, dcl.type.cv/8
791 indicates that volatile semantics should be the same between C and C++
792 where ever possible. C leaves it implementation defined as to what
793 constitutes an access to a volatile. So, we interpret `*vp' as a read of
794 the volatile object `vp' points to, unless that is an incomplete type. For
795 volatile references we do not do this interpretation, because that would
796 make it impossible to ignore the reference return value from functions. We
797 issue warnings in the confusing cases.
799 IMPLICIT is non-NULL iff an expression is being implicitly converted; it
800 is NULL when the user is explicitly converting an expression to void via
801 a cast. When non-NULL, IMPLICIT is a string indicating the context of
802 the implicit conversion. */
805 convert_to_void (tree expr, const char *implicit, tsubst_flags_t complain)
807 if (expr == error_mark_node
808 || TREE_TYPE (expr) == error_mark_node)
809 return error_mark_node;
810 if (!TREE_TYPE (expr))
812 if (invalid_nonstatic_memfn_p (expr, complain))
813 return error_mark_node;
814 if (TREE_CODE (expr) == PSEUDO_DTOR_EXPR)
816 if (complain & tf_error)
817 error ("pseudo-destructor is not called");
818 return error_mark_node;
820 if (VOID_TYPE_P (TREE_TYPE (expr)))
822 switch (TREE_CODE (expr))
826 /* The two parts of a cond expr might be separate lvalues. */
827 tree op1 = TREE_OPERAND (expr,1);
828 tree op2 = TREE_OPERAND (expr,2);
829 tree new_op1 = convert_to_void
830 (op1, (implicit && !TREE_SIDE_EFFECTS (op2)
831 ? "second operand of conditional" : NULL), complain);
832 tree new_op2 = convert_to_void
833 (op2, (implicit && !TREE_SIDE_EFFECTS (op1)
834 ? "third operand of conditional" : NULL), complain);
836 expr = build3 (COND_EXPR, TREE_TYPE (new_op1),
837 TREE_OPERAND (expr, 0), new_op1, new_op2);
843 /* The second part of a compound expr contains the value. */
844 tree op1 = TREE_OPERAND (expr,1);
845 tree new_op1 = convert_to_void
846 (op1, (implicit && !TREE_NO_WARNING (expr)
847 ? "right-hand operand of comma" : NULL), complain);
851 tree t = build2 (COMPOUND_EXPR, TREE_TYPE (new_op1),
852 TREE_OPERAND (expr, 0), new_op1);
859 case NON_LVALUE_EXPR:
861 /* These have already decayed to rvalue. */
864 case CALL_EXPR: /* We have a special meaning for volatile void fn(). */
869 tree type = TREE_TYPE (expr);
870 int is_reference = TREE_CODE (TREE_TYPE (TREE_OPERAND (expr, 0)))
872 int is_volatile = TYPE_VOLATILE (type);
873 int is_complete = COMPLETE_TYPE_P (complete_type (type));
875 /* Can't load the value if we don't know the type. */
876 if (is_volatile && !is_complete)
878 if (complain & tf_warning)
879 warning (0, "object of incomplete type %qT will not be accessed in %s",
880 type, implicit ? implicit : "void context");
882 /* Don't load the value if this is an implicit dereference, or if
883 the type needs to be handled by ctors/dtors. */
884 else if (is_volatile && (is_reference || TREE_ADDRESSABLE (type)))
886 if (complain & tf_warning)
887 warning (0, "object of type %qT will not be accessed in %s",
888 TREE_TYPE (TREE_OPERAND (expr, 0)),
889 implicit ? implicit : "void context");
891 if (is_reference || !is_volatile || !is_complete || TREE_ADDRESSABLE (type))
893 /* Emit a warning (if enabled) when the "effect-less" INDIRECT_REF
894 operation is stripped off. Note that we don't warn about
895 - an expression with TREE_NO_WARNING set. (For an example of
896 such expressions, see build_over_call in call.c.)
897 - automatic dereferencing of references, since the user cannot
898 control it. (See also warn_if_unused_value() in stmt.c.) */
899 if (warn_unused_value
901 && (complain & tf_warning)
902 && !TREE_NO_WARNING (expr)
904 warning (OPT_Wunused_value, "value computed is not used");
905 expr = TREE_OPERAND (expr, 0);
913 /* External variables might be incomplete. */
914 tree type = TREE_TYPE (expr);
915 int is_complete = COMPLETE_TYPE_P (complete_type (type));
917 if (TYPE_VOLATILE (type) && !is_complete && (complain & tf_warning))
918 warning (0, "object %qE of incomplete type %qT will not be accessed in %s",
919 expr, type, implicit ? implicit : "void context");
924 /* Don't bother with the temporary object returned from a function if
925 we don't use it and don't need to destroy it. We'll still
926 allocate space for it in expand_call or declare_return_variable,
927 but we don't need to track it through all the tree phases. */
928 if (TARGET_EXPR_IMPLICIT_P (expr)
929 && TYPE_HAS_TRIVIAL_DESTRUCTOR (TREE_TYPE (expr)))
931 tree init = TARGET_EXPR_INITIAL (expr);
932 if (TREE_CODE (init) == AGGR_INIT_EXPR
933 && !AGGR_INIT_VIA_CTOR_P (init))
935 tree fn = AGGR_INIT_EXPR_FN (init);
936 expr = build_call_array (TREE_TYPE (TREE_TYPE (TREE_TYPE (fn))),
938 aggr_init_expr_nargs (init),
939 AGGR_INIT_EXPR_ARGP (init));
949 if (TREE_CODE (probe) == ADDR_EXPR)
950 probe = TREE_OPERAND (expr, 0);
951 if (type_unknown_p (probe))
953 /* [over.over] enumerates the places where we can take the address
954 of an overloaded function, and this is not one of them. */
955 if (complain & tf_error)
956 error ("%s cannot resolve address of overloaded function",
957 implicit ? implicit : "void cast");
959 return error_mark_node;
960 expr = void_zero_node;
962 else if (implicit && probe == expr && is_overloaded_fn (probe))
964 /* Only warn when there is no &. */
965 if (complain & tf_warning)
966 warning (OPT_Waddress, "%s is a reference, not call, to function %qE",
968 if (TREE_CODE (expr) == COMPONENT_REF)
969 expr = TREE_OPERAND (expr, 0);
973 if (expr != error_mark_node && !VOID_TYPE_P (TREE_TYPE (expr)))
977 && !TREE_NO_WARNING (expr)
978 && !processing_template_decl)
980 /* The middle end does not warn about expressions that have
981 been explicitly cast to void, so we must do so here. */
982 if (!TREE_SIDE_EFFECTS (expr)) {
983 if (complain & tf_warning)
984 warning (OPT_Wunused_value, "%s has no effect", implicit);
990 enum tree_code_class tclass;
993 /* We might like to warn about (say) "(int) f()", as the
994 cast has no effect, but the compiler itself will
995 generate implicit conversions under some
996 circumstances. (For example a block copy will be
997 turned into a call to "__builtin_memcpy", with a
998 conversion of the return value to an appropriate
999 type.) So, to avoid false positives, we strip
1000 conversions. Do not use STRIP_NOPs because it will
1001 not strip conversions to "void", as that is not a
1002 mode-preserving conversion. */
1003 while (TREE_CODE (e) == NOP_EXPR)
1004 e = TREE_OPERAND (e, 0);
1006 code = TREE_CODE (e);
1007 tclass = TREE_CODE_CLASS (code);
1008 if ((tclass == tcc_comparison
1009 || tclass == tcc_unary
1010 || (tclass == tcc_binary
1011 && !(code == MODIFY_EXPR
1012 || code == INIT_EXPR
1013 || code == PREDECREMENT_EXPR
1014 || code == PREINCREMENT_EXPR
1015 || code == POSTDECREMENT_EXPR
1016 || code == POSTINCREMENT_EXPR)))
1017 && (complain & tf_warning))
1018 warning (OPT_Wunused_value, "value computed is not used");
1021 expr = build1 (CONVERT_EXPR, void_type_node, expr);
1023 if (! TREE_SIDE_EFFECTS (expr))
1024 expr = void_zero_node;
1028 /* Create an expression whose value is that of EXPR,
1029 converted to type TYPE. The TREE_TYPE of the value
1030 is always TYPE. This function implements all reasonable
1031 conversions; callers should filter out those that are
1032 not permitted by the language being compiled.
1034 Most of this routine is from build_reinterpret_cast.
1036 The back end cannot call cp_convert (what was convert) because
1037 conversions to/from basetypes may involve memory references
1038 (vbases) and adding or subtracting small values (multiple
1039 inheritance), but it calls convert from the constant folding code
1040 on subtrees of already built trees after it has ripped them apart.
1042 Also, if we ever support range variables, we'll probably also have to
1043 do a little bit more work. */
1046 convert (tree type, tree expr)
1050 if (type == error_mark_node || expr == error_mark_node)
1051 return error_mark_node;
1053 intype = TREE_TYPE (expr);
1055 if (POINTER_TYPE_P (type) && POINTER_TYPE_P (intype))
1056 return fold_if_not_in_template (build_nop (type, expr));
1058 return ocp_convert (type, expr, CONV_OLD_CONVERT,
1059 LOOKUP_NORMAL|LOOKUP_NO_CONVERSION);
1062 /* Like cp_convert, except permit conversions to take place which
1063 are not normally allowed due to access restrictions
1064 (such as conversion from sub-type to private super-type). */
1067 convert_force (tree type, tree expr, int convtype)
1070 enum tree_code code = TREE_CODE (type);
1072 if (code == REFERENCE_TYPE)
1073 return (fold_if_not_in_template
1074 (convert_to_reference (type, e, CONV_C_CAST, LOOKUP_COMPLAIN,
1077 if (code == POINTER_TYPE)
1078 return fold_if_not_in_template (convert_to_pointer_force (type, e));
1080 /* From typeck.c convert_for_assignment */
1081 if (((TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE && TREE_CODE (e) == ADDR_EXPR
1082 && TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE
1083 && TREE_CODE (TREE_TYPE (TREE_TYPE (e))) == METHOD_TYPE)
1084 || integer_zerop (e)
1085 || TYPE_PTRMEMFUNC_P (TREE_TYPE (e)))
1086 && TYPE_PTRMEMFUNC_P (type))
1087 /* compatible pointer to member functions. */
1088 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), e, 1,
1091 return ocp_convert (type, e, CONV_C_CAST|convtype, LOOKUP_NORMAL);
1094 /* Convert an aggregate EXPR to type XTYPE. If a conversion
1095 exists, return the attempted conversion. This may
1096 return ERROR_MARK_NODE if the conversion is not
1097 allowed (references private members, etc).
1098 If no conversion exists, NULL_TREE is returned.
1100 FIXME: Ambiguity checking is wrong. Should choose one by the implicit
1101 object parameter, or by the second standard conversion sequence if
1102 that doesn't do it. This will probably wait for an overloading rewrite.
1106 build_type_conversion (tree xtype, tree expr)
1108 /* C++: check to see if we can convert this aggregate type
1109 into the required type. */
1110 return build_user_type_conversion (xtype, expr, LOOKUP_NORMAL);
1113 /* Convert the given EXPR to one of a group of types suitable for use in an
1114 expression. DESIRES is a combination of various WANT_* flags (q.v.)
1115 which indicates which types are suitable. If COMPLAIN is true, complain
1116 about ambiguity; otherwise, the caller will deal with it. */
1119 build_expr_type_conversion (int desires, tree expr, bool complain)
1121 tree basetype = TREE_TYPE (expr);
1122 tree conv = NULL_TREE;
1123 tree winner = NULL_TREE;
1125 if (expr == null_node
1126 && (desires & WANT_INT)
1127 && !(desires & WANT_NULL))
1128 warning (OPT_Wconversion, "converting NULL to non-pointer type");
1130 basetype = TREE_TYPE (expr);
1132 if (basetype == error_mark_node)
1133 return error_mark_node;
1135 if (! MAYBE_CLASS_TYPE_P (basetype))
1136 switch (TREE_CODE (basetype))
1139 if ((desires & WANT_NULL) && null_ptr_cst_p (expr))
1141 /* else fall through... */
1144 return (desires & WANT_INT) ? expr : NULL_TREE;
1146 return (desires & WANT_ENUM) ? expr : NULL_TREE;
1148 return (desires & WANT_FLOAT) ? expr : NULL_TREE;
1150 return (desires & WANT_POINTER) ? expr : NULL_TREE;
1154 return (desires & WANT_POINTER) ? decay_conversion (expr)
1158 if ((desires & WANT_VECTOR) == 0)
1160 switch (TREE_CODE (TREE_TYPE (basetype)))
1164 return (desires & WANT_INT) ? expr : NULL_TREE;
1166 return (desires & WANT_ENUM) ? expr : NULL_TREE;
1168 return (desires & WANT_FLOAT) ? expr : NULL_TREE;
1177 /* The code for conversions from class type is currently only used for
1178 delete expressions. Other expressions are handled by build_new_op. */
1179 if (!complete_type_or_else (basetype, expr))
1180 return error_mark_node;
1181 if (!TYPE_HAS_CONVERSION (basetype))
1184 for (conv = lookup_conversions (basetype); conv; conv = TREE_CHAIN (conv))
1188 tree cand = TREE_VALUE (conv);
1190 if (winner && winner == cand)
1193 if (DECL_NONCONVERTING_P (cand))
1196 candidate = non_reference (TREE_TYPE (TREE_TYPE (cand)));
1198 switch (TREE_CODE (candidate))
1202 win = (desires & WANT_INT); break;
1204 win = (desires & WANT_ENUM); break;
1206 win = (desires & WANT_FLOAT); break;
1208 win = (desires & WANT_POINTER); break;
1211 if ((desires & WANT_VECTOR) == 0)
1213 switch (TREE_CODE (TREE_TYPE (candidate)))
1217 win = (desires & WANT_INT); break;
1219 win = (desires & WANT_ENUM); break;
1221 win = (desires & WANT_FLOAT); break;
1237 error ("ambiguous default type conversion from %qT",
1239 error (" candidate conversions include %qD and %qD",
1242 return error_mark_node;
1251 tree type = non_reference (TREE_TYPE (TREE_TYPE (winner)));
1252 return build_user_type_conversion (type, expr, LOOKUP_NORMAL);
1258 /* Implements integral promotion (4.1) and float->double promotion. */
1261 type_promotes_to (tree type)
1265 if (type == error_mark_node)
1266 return error_mark_node;
1268 type = TYPE_MAIN_VARIANT (type);
1270 /* Check for promotions of target-defined types first. */
1271 promoted_type = targetm.promoted_type (type);
1273 return promoted_type;
1275 /* bool always promotes to int (not unsigned), even if it's the same
1277 if (type == boolean_type_node)
1278 type = integer_type_node;
1280 /* Normally convert enums to int, but convert wide enums to something
1282 else if (TREE_CODE (type) == ENUMERAL_TYPE
1283 || type == char16_type_node
1284 || type == char32_type_node
1285 || type == wchar_type_node)
1287 int precision = MAX (TYPE_PRECISION (type),
1288 TYPE_PRECISION (integer_type_node));
1289 tree totype = c_common_type_for_size (precision, 0);
1290 if (TYPE_UNSIGNED (type)
1291 && ! int_fits_type_p (TYPE_MAX_VALUE (type), totype))
1292 type = c_common_type_for_size (precision, 1);
1296 else if (c_promoting_integer_type_p (type))
1298 /* Retain unsignedness if really not getting bigger. */
1299 if (TYPE_UNSIGNED (type)
1300 && TYPE_PRECISION (type) == TYPE_PRECISION (integer_type_node))
1301 type = unsigned_type_node;
1303 type = integer_type_node;
1305 else if (type == float_type_node)
1306 type = double_type_node;
1311 /* The routines below this point are carefully written to conform to
1312 the standard. They use the same terminology, and follow the rules
1313 closely. Although they are used only in pt.c at the moment, they
1314 should presumably be used everywhere in the future. */
1316 /* Attempt to perform qualification conversions on EXPR to convert it
1317 to TYPE. Return the resulting expression, or error_mark_node if
1318 the conversion was impossible. */
1321 perform_qualification_conversions (tree type, tree expr)
1325 expr_type = TREE_TYPE (expr);
1327 if (same_type_p (type, expr_type))
1329 else if (TYPE_PTR_P (type) && TYPE_PTR_P (expr_type)
1330 && comp_ptr_ttypes (TREE_TYPE (type), TREE_TYPE (expr_type)))
1331 return build_nop (type, expr);
1332 else if (TYPE_PTR_TO_MEMBER_P (type)
1333 && TYPE_PTR_TO_MEMBER_P (expr_type)
1334 && same_type_p (TYPE_PTRMEM_CLASS_TYPE (type),
1335 TYPE_PTRMEM_CLASS_TYPE (expr_type))
1336 && comp_ptr_ttypes (TYPE_PTRMEM_POINTED_TO_TYPE (type),
1337 TYPE_PTRMEM_POINTED_TO_TYPE (expr_type)))
1338 return build_nop (type, expr);
1340 return error_mark_node;