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 Free Software Foundation, Inc.
4 Hacked by Michael Tiemann (tiemann@cygnus.com)
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 2, or (at your option)
13 GCC is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING. If not, write to
20 the Free Software Foundation, 51 Franklin Street, Fifth Floor,
21 Boston, MA 02110-1301, USA. */
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
, bool);
42 static tree
convert_to_pointer_force (tree
, tree
);
43 static tree
build_up_reference (tree
, tree
, int, tree
);
44 static void warn_ref_binding (tree
, tree
, tree
);
46 /* Change of width--truncation and extension of integers or reals--
47 is represented with NOP_EXPR. Proper functioning of many things
48 assumes that no other conversions can be NOP_EXPRs.
50 Conversion between integer and pointer is represented with CONVERT_EXPR.
51 Converting integer to real uses FLOAT_EXPR
52 and real to integer uses FIX_TRUNC_EXPR.
54 Here is a list of all the functions that assume that widening and
55 narrowing is always done with a NOP_EXPR:
56 In convert.c, convert_to_integer.
57 In c-typeck.c, build_binary_op_nodefault (boolean ops),
58 and c_common_truthvalue_conversion.
59 In expr.c: expand_expr, for operands of a MULT_EXPR.
60 In fold-const.c: fold.
61 In tree.c: get_narrower and get_unwidened.
63 C++: in multiple-inheritance, converting between pointers may involve
64 adjusting them by a delta stored within the class definition. */
66 /* Subroutines of `convert'. */
68 /* if converting pointer to pointer
69 if dealing with classes, check for derived->base or vice versa
70 else if dealing with method pointers, delegate
72 else if converting class, pass off to build_type_conversion
73 else try C-style pointer conversion. If FORCE is true then allow
74 conversions via virtual bases (these are permitted by reinterpret_cast,
75 but not static_cast). */
78 cp_convert_to_pointer (tree type
, tree expr
, bool force
)
80 tree intype
= TREE_TYPE (expr
);
83 if (intype
== error_mark_node
)
84 return error_mark_node
;
86 if (IS_AGGR_TYPE (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 && IS_AGGR_TYPE (TREE_TYPE (type
))
132 && IS_AGGR_TYPE (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
))
181 enum tree_code code
= PLUS_EXPR
;
184 b1
= TYPE_PTRMEM_CLASS_TYPE (type
);
185 b2
= TYPE_PTRMEM_CLASS_TYPE (intype
);
186 binfo
= lookup_base (b1
, b2
, ba_check
, &bk
);
189 binfo
= lookup_base (b2
, b1
, ba_check
, &bk
);
192 if (binfo
== error_mark_node
)
193 return error_mark_node
;
195 if (bk
== bk_via_virtual
)
198 warning (0, "pointer to member cast from %qT to %qT is via"
199 " virtual base", intype
, type
);
202 error ("pointer to member cast from %qT to %qT is"
203 " via virtual base", intype
, type
);
204 return error_mark_node
;
206 /* This is a reinterpret cast, whose result is unspecified.
207 We choose to do nothing. */
208 return build1 (NOP_EXPR
, type
, expr
);
211 if (TREE_CODE (expr
) == PTRMEM_CST
)
212 expr
= cplus_expand_constant (expr
);
214 if (binfo
&& !integer_zerop (BINFO_OFFSET (binfo
)))
215 expr
= size_binop (code
,
216 build_nop (sizetype
, expr
),
217 BINFO_OFFSET (binfo
));
218 return build_nop (type
, expr
);
220 else if (TYPE_PTRMEMFUNC_P (type
) && TYPE_PTRMEMFUNC_P (intype
))
221 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type
), expr
, 0,
223 else if (TYPE_PTRMEMFUNC_P (intype
))
227 if (TREE_CODE (expr
) == PTRMEM_CST
)
228 return cp_convert_to_pointer (type
,
229 PTRMEM_CST_MEMBER (expr
),
231 else if (TREE_CODE (expr
) == OFFSET_REF
)
233 tree object
= TREE_OPERAND (expr
, 0);
234 return get_member_function_from_ptrfunc (&object
,
235 TREE_OPERAND (expr
, 1));
238 error ("cannot convert %qE from type %qT to type %qT",
240 return error_mark_node
;
243 if (integer_zerop (expr
))
245 if (TYPE_PTRMEMFUNC_P (type
))
246 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type
), expr
, 0,
249 if (TYPE_PTRMEM_P (type
))
251 /* A NULL pointer-to-member is represented by -1, not by
253 expr
= build_int_cst (type
, -1);
254 /* Fix up the representation of -1 if appropriate. */
255 expr
= force_fit_type (expr
, 0, false, false);
258 expr
= build_int_cst (type
, 0);
262 else if (TYPE_PTR_TO_MEMBER_P (type
) && INTEGRAL_CODE_P (form
))
264 error ("invalid conversion from %qT to %qT", intype
, type
);
265 return error_mark_node
;
268 if (INTEGRAL_CODE_P (form
))
270 if (TYPE_PRECISION (intype
) == POINTER_SIZE
)
271 return build1 (CONVERT_EXPR
, type
, expr
);
272 expr
= cp_convert (c_common_type_for_size (POINTER_SIZE
, 0), expr
);
273 /* Modes may be different but sizes should be the same. There
274 is supposed to be some integral type that is the same width
276 gcc_assert (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (expr
)))
277 == GET_MODE_SIZE (TYPE_MODE (type
)));
279 return convert_to_pointer (type
, expr
);
282 if (type_unknown_p (expr
))
283 return instantiate_type (type
, expr
, tf_error
| tf_warning
);
285 error ("cannot convert %qE from type %qT to type %qT",
287 return error_mark_node
;
290 /* Like convert, except permit conversions to take place which
291 are not normally allowed due to access restrictions
292 (such as conversion from sub-type to private super-type). */
295 convert_to_pointer_force (tree type
, tree expr
)
297 tree intype
= TREE_TYPE (expr
);
298 enum tree_code form
= TREE_CODE (intype
);
300 if (form
== POINTER_TYPE
)
302 intype
= TYPE_MAIN_VARIANT (intype
);
304 if (TYPE_MAIN_VARIANT (type
) != intype
305 && TREE_CODE (TREE_TYPE (type
)) == RECORD_TYPE
306 && IS_AGGR_TYPE (TREE_TYPE (type
))
307 && IS_AGGR_TYPE (TREE_TYPE (intype
))
308 && TREE_CODE (TREE_TYPE (intype
)) == RECORD_TYPE
)
310 enum tree_code code
= PLUS_EXPR
;
313 binfo
= lookup_base (TREE_TYPE (intype
), TREE_TYPE (type
),
317 binfo
= lookup_base (TREE_TYPE (type
), TREE_TYPE (intype
),
321 if (binfo
== error_mark_node
)
322 return error_mark_node
;
325 expr
= build_base_path (code
, expr
, binfo
, 0);
326 if (expr
== error_mark_node
)
327 return error_mark_node
;
328 /* Add any qualifier conversions. */
329 if (!same_type_p (TREE_TYPE (TREE_TYPE (expr
)),
331 expr
= build_nop (type
, expr
);
337 return cp_convert_to_pointer (type
, expr
, true);
340 /* We are passing something to a function which requires a reference.
341 The type we are interested in is in TYPE. The initial
342 value we have to begin with is in ARG.
344 FLAGS controls how we manage access checking.
345 DIRECT_BIND in FLAGS controls how any temporaries are generated.
346 If DIRECT_BIND is set, DECL is the reference we're binding to. */
349 build_up_reference (tree type
, tree arg
, int flags
, tree decl
)
352 tree argtype
= TREE_TYPE (arg
);
353 tree target_type
= TREE_TYPE (type
);
355 gcc_assert (TREE_CODE (type
) == REFERENCE_TYPE
);
357 if ((flags
& DIRECT_BIND
) && ! real_lvalue_p (arg
))
359 /* Create a new temporary variable. We can't just use a TARGET_EXPR
360 here because it needs to live as long as DECL. */
363 arg
= make_temporary_var_for_ref_to_temp (decl
, TREE_TYPE (arg
));
365 /* Process the initializer for the declaration. */
366 DECL_INITIAL (arg
) = targ
;
367 cp_finish_decl (arg
, targ
, NULL_TREE
,
368 LOOKUP_ONLYCONVERTING
|DIRECT_BIND
);
370 else if (!(flags
& DIRECT_BIND
) && ! lvalue_p (arg
))
371 return get_target_expr (arg
);
373 /* If we had a way to wrap this up, and say, if we ever needed its
374 address, transform all occurrences of the register, into a memory
375 reference we could win better. */
376 rval
= build_unary_op (ADDR_EXPR
, arg
, 1);
377 if (rval
== error_mark_node
)
378 return error_mark_node
;
380 if ((flags
& LOOKUP_PROTECT
)
381 && TYPE_MAIN_VARIANT (argtype
) != TYPE_MAIN_VARIANT (target_type
)
382 && IS_AGGR_TYPE (argtype
)
383 && IS_AGGR_TYPE (target_type
))
385 /* We go through lookup_base for the access control. */
386 tree binfo
= lookup_base (argtype
, target_type
, ba_check
, NULL
);
387 if (binfo
== error_mark_node
)
388 return error_mark_node
;
389 if (binfo
== NULL_TREE
)
390 return error_not_base_type (target_type
, argtype
);
391 rval
= build_base_path (PLUS_EXPR
, rval
, binfo
, 1);
395 = convert_to_pointer_force (build_pointer_type (target_type
), rval
);
396 return build_nop (type
, rval
);
399 /* Subroutine of convert_to_reference. REFTYPE is the target reference type.
400 INTYPE is the original rvalue type and DECL is an optional _DECL node
403 [dcl.init.ref] says that if an rvalue is used to
404 initialize a reference, then the reference must be to a
405 non-volatile const type. */
408 warn_ref_binding (tree reftype
, tree intype
, tree decl
)
410 tree ttl
= TREE_TYPE (reftype
);
412 if (!CP_TYPE_CONST_NON_VOLATILE_P (ttl
))
416 if (CP_TYPE_VOLATILE_P (ttl
) && decl
)
417 msg
= "initialization of volatile reference type %q#T from"
418 " rvalue of type %qT";
419 else if (CP_TYPE_VOLATILE_P (ttl
))
420 msg
= "conversion to volatile reference type %q#T "
421 " from rvalue of type %qT";
423 msg
= "initialization of non-const reference type %q#T from"
424 " rvalue of type %qT";
426 msg
= "conversion to non-const reference type %q#T from"
427 " rvalue of type %qT";
429 pedwarn (msg
, reftype
, intype
);
433 /* For C++: Only need to do one-level references, but cannot
434 get tripped up on signed/unsigned differences.
436 DECL is either NULL_TREE or the _DECL node for a reference that is being
437 initialized. It can be error_mark_node if we don't know the _DECL but
438 we know it's an initialization. */
441 convert_to_reference (tree reftype
, tree expr
, int convtype
,
442 int flags
, tree decl
)
444 tree type
= TYPE_MAIN_VARIANT (TREE_TYPE (reftype
));
446 tree rval
= NULL_TREE
;
447 tree rval_as_conversion
= NULL_TREE
;
448 bool can_convert_intype_to_type
;
450 if (TREE_CODE (type
) == FUNCTION_TYPE
451 && TREE_TYPE (expr
) == unknown_type_node
)
452 expr
= instantiate_type (type
, expr
,
453 (flags
& LOOKUP_COMPLAIN
)
454 ? tf_error
| tf_warning
: tf_none
);
456 if (expr
== error_mark_node
)
457 return error_mark_node
;
459 intype
= TREE_TYPE (expr
);
461 gcc_assert (TREE_CODE (intype
) != REFERENCE_TYPE
);
463 intype
= TYPE_MAIN_VARIANT (intype
);
465 can_convert_intype_to_type
= can_convert (type
, intype
);
466 if (!can_convert_intype_to_type
467 && (convtype
& CONV_IMPLICIT
) && IS_AGGR_TYPE (intype
)
468 && ! (flags
& LOOKUP_NO_CONVERSION
))
470 /* Look for a user-defined conversion to lvalue that we can use. */
473 = build_type_conversion (reftype
, expr
);
475 if (rval_as_conversion
&& rval_as_conversion
!= error_mark_node
476 && real_lvalue_p (rval_as_conversion
))
478 expr
= rval_as_conversion
;
479 rval_as_conversion
= NULL_TREE
;
481 can_convert_intype_to_type
= 1;
485 if (((convtype
& CONV_STATIC
) && can_convert (intype
, type
))
486 || ((convtype
& CONV_IMPLICIT
) && can_convert_intype_to_type
))
488 if (flags
& LOOKUP_COMPLAIN
)
490 tree ttl
= TREE_TYPE (reftype
);
491 tree ttr
= lvalue_type (expr
);
493 if (! real_lvalue_p (expr
))
494 warn_ref_binding (reftype
, intype
, decl
);
496 if (! (convtype
& CONV_CONST
)
497 && !at_least_as_qualified_p (ttl
, ttr
))
498 pedwarn ("conversion from %qT to %qT discards qualifiers",
502 return build_up_reference (reftype
, expr
, flags
, decl
);
504 else if ((convtype
& CONV_REINTERPRET
) && lvalue_p (expr
))
506 /* When casting an lvalue to a reference type, just convert into
507 a pointer to the new type and deference it. This is allowed
508 by San Diego WP section 5.2.9 paragraph 12, though perhaps it
509 should be done directly (jason). (int &)ri ---> *(int*)&ri */
511 /* B* bp; A& ar = (A&)bp; is valid, but it's probably not what they
513 if (TREE_CODE (intype
) == POINTER_TYPE
514 && (comptypes (TREE_TYPE (intype
), type
,
515 COMPARE_BASE
| COMPARE_DERIVED
)))
516 warning (0, "casting %qT to %qT does not dereference pointer",
519 rval
= build_unary_op (ADDR_EXPR
, expr
, 0);
520 if (rval
!= error_mark_node
)
521 rval
= convert_force (build_pointer_type (TREE_TYPE (reftype
)),
523 if (rval
!= error_mark_node
)
524 rval
= build1 (NOP_EXPR
, reftype
, rval
);
528 rval
= convert_for_initialization (NULL_TREE
, type
, expr
, flags
,
530 if (rval
== NULL_TREE
|| rval
== error_mark_node
)
532 warn_ref_binding (reftype
, intype
, decl
);
533 rval
= build_up_reference (reftype
, rval
, flags
, decl
);
538 /* If we found a way to convert earlier, then use it. */
542 if (flags
& LOOKUP_COMPLAIN
)
543 error ("cannot convert type %qT to type %qT", intype
, reftype
);
545 return error_mark_node
;
548 /* We are using a reference VAL for its value. Bash that reference all the
549 way down to its lowest form. */
552 convert_from_reference (tree val
)
554 if (TREE_CODE (TREE_TYPE (val
)) == REFERENCE_TYPE
)
556 tree t
= canonical_type_variant (TREE_TYPE (TREE_TYPE (val
)));
557 tree ref
= build1 (INDIRECT_REF
, t
, val
);
559 /* We *must* set TREE_READONLY when dereferencing a pointer to const,
560 so that we get the proper error message if the result is used
561 to assign to. Also, &* is supposed to be a no-op. */
562 TREE_READONLY (ref
) = CP_TYPE_CONST_P (t
);
563 TREE_THIS_VOLATILE (ref
) = CP_TYPE_VOLATILE_P (t
);
564 TREE_SIDE_EFFECTS (ref
)
565 = (TREE_THIS_VOLATILE (ref
) || TREE_SIDE_EFFECTS (val
));
566 REFERENCE_REF_P (ref
) = 1;
573 /* Really perform an lvalue-to-rvalue conversion, including copying an
574 argument of class type into a temporary. */
577 force_rvalue (tree expr
)
579 if (IS_AGGR_TYPE (TREE_TYPE (expr
)) && TREE_CODE (expr
) != TARGET_EXPR
)
580 expr
= ocp_convert (TREE_TYPE (expr
), expr
,
581 CONV_IMPLICIT
|CONV_FORCE_TEMP
, LOOKUP_NORMAL
);
583 expr
= decay_conversion (expr
);
588 /* C++ conversions, preference to static cast conversions. */
591 cp_convert (tree type
, tree expr
)
593 return ocp_convert (type
, expr
, CONV_OLD_CONVERT
, LOOKUP_NORMAL
);
598 FLAGS indicates how we should behave. */
601 ocp_convert (tree type
, tree expr
, int convtype
, int flags
)
604 enum tree_code code
= TREE_CODE (type
);
605 const char *invalid_conv_diag
;
607 if (error_operand_p (e
) || type
== error_mark_node
)
608 return error_mark_node
;
610 complete_type (type
);
611 complete_type (TREE_TYPE (expr
));
613 if ((invalid_conv_diag
614 = targetm
.invalid_conversion (TREE_TYPE (expr
), type
)))
616 error (invalid_conv_diag
);
617 return error_mark_node
;
620 e
= integral_constant_value (e
);
622 if (IS_AGGR_TYPE (type
) && (convtype
& CONV_FORCE_TEMP
)
623 /* Some internal structures (vtable_entry_type, sigtbl_ptr_type)
624 don't go through finish_struct, so they don't have the synthesized
625 constructors. So don't force a temporary. */
626 && TYPE_HAS_CONSTRUCTOR (type
))
627 /* We need a new temporary; don't take this shortcut. */;
628 else if (TYPE_MAIN_VARIANT (type
) == TYPE_MAIN_VARIANT (TREE_TYPE (e
)))
630 if (same_type_p (type
, TREE_TYPE (e
)))
631 /* The call to fold will not always remove the NOP_EXPR as
632 might be expected, since if one of the types is a typedef;
633 the comparison in fold is just equality of pointers, not a
634 call to comptypes. We don't call fold in this case because
635 that can result in infinite recursion; fold will call
636 convert, which will call ocp_convert, etc. */
638 /* For complex data types, we need to perform componentwise
640 else if (TREE_CODE (type
) == COMPLEX_TYPE
)
641 return fold_if_not_in_template (convert_to_complex (type
, e
));
642 else if (TREE_CODE (e
) == TARGET_EXPR
)
644 /* Don't build a NOP_EXPR of class type. Instead, change the
645 type of the temporary. Only allow this for cv-qual changes,
647 gcc_assert (same_type_p (TYPE_MAIN_VARIANT (TREE_TYPE (e
)),
648 TYPE_MAIN_VARIANT (type
)));
649 TREE_TYPE (e
) = TREE_TYPE (TARGET_EXPR_SLOT (e
)) = type
;
654 /* We shouldn't be treating objects of ADDRESSABLE type as
656 gcc_assert (!TREE_ADDRESSABLE (type
));
657 return fold_if_not_in_template (build_nop (type
, e
));
661 if (code
== VOID_TYPE
&& (convtype
& CONV_STATIC
))
663 e
= convert_to_void (e
, /*implicit=*/NULL
);
667 if (INTEGRAL_CODE_P (code
))
669 tree intype
= TREE_TYPE (e
);
670 /* enum = enum, enum = int, enum = float, (enum)pointer are all
672 if (TREE_CODE (type
) == ENUMERAL_TYPE
673 && (((INTEGRAL_OR_ENUMERATION_TYPE_P (intype
)
674 || TREE_CODE (intype
) == REAL_TYPE
)
675 && ! (convtype
& CONV_STATIC
))
676 || TREE_CODE (intype
) == POINTER_TYPE
))
678 if (flags
& LOOKUP_COMPLAIN
)
679 pedwarn ("conversion from %q#T to %q#T", intype
, type
);
681 if (flag_pedantic_errors
)
682 return error_mark_node
;
684 if (IS_AGGR_TYPE (intype
))
687 rval
= build_type_conversion (type
, e
);
690 if (flags
& LOOKUP_COMPLAIN
)
691 error ("%q#T used where a %qT was expected", intype
, type
);
692 return error_mark_node
;
694 if (code
== BOOLEAN_TYPE
)
695 return cp_truthvalue_conversion (e
);
697 return fold_if_not_in_template (convert_to_integer (type
, e
));
699 if (POINTER_TYPE_P (type
) || TYPE_PTR_TO_MEMBER_P (type
))
700 return fold_if_not_in_template (cp_convert_to_pointer (type
, e
, false));
701 if (code
== VECTOR_TYPE
)
703 tree in_vtype
= TREE_TYPE (e
);
704 if (IS_AGGR_TYPE (in_vtype
))
707 ret_val
= build_type_conversion (type
, e
);
710 if (flags
& LOOKUP_COMPLAIN
)
711 error ("%q#T used where a %qT was expected", in_vtype
, type
);
712 return error_mark_node
;
714 return fold_if_not_in_template (convert_to_vector (type
, e
));
716 if (code
== REAL_TYPE
|| code
== COMPLEX_TYPE
)
718 if (IS_AGGR_TYPE (TREE_TYPE (e
)))
721 rval
= build_type_conversion (type
, e
);
725 if (flags
& LOOKUP_COMPLAIN
)
726 error ("%q#T used where a floating point value was expected",
729 if (code
== REAL_TYPE
)
730 return fold_if_not_in_template (convert_to_real (type
, e
));
731 else if (code
== COMPLEX_TYPE
)
732 return fold_if_not_in_template (convert_to_complex (type
, e
));
735 /* New C++ semantics: since assignment is now based on
736 memberwise copying, if the rhs type is derived from the
737 lhs type, then we may still do a conversion. */
738 if (IS_AGGR_TYPE_CODE (code
))
740 tree dtype
= TREE_TYPE (e
);
741 tree ctor
= NULL_TREE
;
743 dtype
= TYPE_MAIN_VARIANT (dtype
);
745 /* Conversion between aggregate types. New C++ semantics allow
746 objects of derived type to be cast to objects of base type.
747 Old semantics only allowed this between pointers.
749 There may be some ambiguity between using a constructor
750 vs. using a type conversion operator when both apply. */
754 if (abstract_virtuals_error (NULL_TREE
, type
))
755 return error_mark_node
;
757 if ((flags
& LOOKUP_ONLYCONVERTING
)
758 && ! (IS_AGGR_TYPE (dtype
) && DERIVED_FROM_P (type
, dtype
)))
759 /* For copy-initialization, first we create a temp of the proper type
760 with a user-defined conversion sequence, then we direct-initialize
761 the target with the temp (see [dcl.init]). */
762 ctor
= build_user_type_conversion (type
, ctor
, flags
);
764 ctor
= build_special_member_call (NULL_TREE
,
765 complete_ctor_identifier
,
766 build_tree_list (NULL_TREE
, ctor
),
769 return build_cplus_new (type
, ctor
);
772 if (flags
& LOOKUP_COMPLAIN
)
773 error ("conversion from %qT to non-scalar type %qT requested",
774 TREE_TYPE (expr
), type
);
775 return error_mark_node
;
778 /* When an expression is used in a void context, its value is discarded and
779 no lvalue-rvalue and similar conversions happen [expr.static.cast/4,
780 stmt.expr/1, expr.comma/1]. This permits dereferencing an incomplete type
781 in a void context. The C++ standard does not define what an `access' to an
782 object is, but there is reason to believe that it is the lvalue to rvalue
783 conversion -- if it were not, `*&*p = 1' would violate [expr]/4 in that it
784 accesses `*p' not to calculate the value to be stored. But, dcl.type.cv/8
785 indicates that volatile semantics should be the same between C and C++
786 where ever possible. C leaves it implementation defined as to what
787 constitutes an access to a volatile. So, we interpret `*vp' as a read of
788 the volatile object `vp' points to, unless that is an incomplete type. For
789 volatile references we do not do this interpretation, because that would
790 make it impossible to ignore the reference return value from functions. We
791 issue warnings in the confusing cases.
793 IMPLICIT is tells us the context of an implicit void conversion. */
796 convert_to_void (tree expr
, const char *implicit
)
798 if (expr
== error_mark_node
799 || TREE_TYPE (expr
) == error_mark_node
)
800 return error_mark_node
;
801 if (!TREE_TYPE (expr
))
803 if (invalid_nonstatic_memfn_p (expr
))
804 return error_mark_node
;
805 if (TREE_CODE (expr
) == PSEUDO_DTOR_EXPR
)
807 error ("pseudo-destructor is not called");
808 return error_mark_node
;
810 if (VOID_TYPE_P (TREE_TYPE (expr
)))
812 switch (TREE_CODE (expr
))
816 /* The two parts of a cond expr might be separate lvalues. */
817 tree op1
= TREE_OPERAND (expr
,1);
818 tree op2
= TREE_OPERAND (expr
,2);
819 tree new_op1
= convert_to_void
820 (op1
, (implicit
&& !TREE_SIDE_EFFECTS (op2
)
821 ? "second operand of conditional" : NULL
));
822 tree new_op2
= convert_to_void
823 (op2
, (implicit
&& !TREE_SIDE_EFFECTS (op1
)
824 ? "third operand of conditional" : NULL
));
826 expr
= build3 (COND_EXPR
, TREE_TYPE (new_op1
),
827 TREE_OPERAND (expr
, 0), new_op1
, new_op2
);
833 /* The second part of a compound expr contains the value. */
834 tree op1
= TREE_OPERAND (expr
,1);
835 tree new_op1
= convert_to_void
836 (op1
, (implicit
&& !TREE_NO_WARNING (expr
)
837 ? "right-hand operand of comma" : NULL
));
841 tree t
= build2 (COMPOUND_EXPR
, TREE_TYPE (new_op1
),
842 TREE_OPERAND (expr
, 0), new_op1
);
849 case NON_LVALUE_EXPR
:
851 /* These have already decayed to rvalue. */
854 case CALL_EXPR
: /* We have a special meaning for volatile void fn(). */
859 tree type
= TREE_TYPE (expr
);
860 int is_reference
= TREE_CODE (TREE_TYPE (TREE_OPERAND (expr
, 0)))
862 int is_volatile
= TYPE_VOLATILE (type
);
863 int is_complete
= COMPLETE_TYPE_P (complete_type (type
));
865 if (is_volatile
&& !is_complete
)
866 warning (0, "object of incomplete type %qT will not be accessed in %s",
867 type
, implicit
? implicit
: "void context");
868 else if (is_reference
&& is_volatile
)
869 warning (0, "object of type %qT will not be accessed in %s",
870 TREE_TYPE (TREE_OPERAND (expr
, 0)),
871 implicit
? implicit
: "void context");
872 if (is_reference
|| !is_volatile
|| !is_complete
)
873 expr
= TREE_OPERAND (expr
, 0);
880 /* External variables might be incomplete. */
881 tree type
= TREE_TYPE (expr
);
882 int is_complete
= COMPLETE_TYPE_P (complete_type (type
));
884 if (TYPE_VOLATILE (type
) && !is_complete
)
885 warning (0, "object %qE of incomplete type %qT will not be accessed in %s",
886 expr
, type
, implicit
? implicit
: "void context");
895 if (TREE_CODE (probe
) == ADDR_EXPR
)
896 probe
= TREE_OPERAND (expr
, 0);
897 if (type_unknown_p (probe
))
899 /* [over.over] enumerates the places where we can take the address
900 of an overloaded function, and this is not one of them. */
901 pedwarn ("%s cannot resolve address of overloaded function",
902 implicit
? implicit
: "void cast");
903 expr
= void_zero_node
;
905 else if (implicit
&& probe
== expr
&& is_overloaded_fn (probe
))
906 /* Only warn when there is no &. */
907 warning (0, "%s is a reference, not call, to function %qE",
911 if (expr
!= error_mark_node
&& !VOID_TYPE_P (TREE_TYPE (expr
)))
915 && !TREE_NO_WARNING (expr
)
916 && !processing_template_decl
)
918 /* The middle end does not warn about expressions that have
919 been explicitly cast to void, so we must do so here. */
920 if (!TREE_SIDE_EFFECTS (expr
))
921 warning (0, "%s has no effect", implicit
);
926 enum tree_code_class
class;
929 /* We might like to warn about (say) "(int) f()", as the
930 cast has no effect, but the compiler itself will
931 generate implicit conversions under some
932 circumstances. (For example a block copy will be
933 turned into a call to "__builtin_memcpy", with a
934 conversion of the return value to an appropriate
935 type.) So, to avoid false positives, we strip
936 conversions. Do not use STRIP_NOPs because it will
937 not strip conversions to "void", as that is not a
938 mode-preserving conversion. */
939 while (TREE_CODE (e
) == NOP_EXPR
)
940 e
= TREE_OPERAND (e
, 0);
942 code
= TREE_CODE (e
);
943 class = TREE_CODE_CLASS (code
);
944 if (class == tcc_comparison
945 || class == tcc_unary
946 || (class == tcc_binary
947 && !(code
== MODIFY_EXPR
949 || code
== PREDECREMENT_EXPR
950 || code
== PREINCREMENT_EXPR
951 || code
== POSTDECREMENT_EXPR
952 || code
== POSTINCREMENT_EXPR
)))
953 warning (0, "value computed is not used");
956 expr
= build1 (CONVERT_EXPR
, void_type_node
, expr
);
961 /* Create an expression whose value is that of EXPR,
962 converted to type TYPE. The TREE_TYPE of the value
963 is always TYPE. This function implements all reasonable
964 conversions; callers should filter out those that are
965 not permitted by the language being compiled.
967 Most of this routine is from build_reinterpret_cast.
969 The backend cannot call cp_convert (what was convert) because
970 conversions to/from basetypes may involve memory references
971 (vbases) and adding or subtracting small values (multiple
972 inheritance), but it calls convert from the constant folding code
973 on subtrees of already built trees after it has ripped them apart.
975 Also, if we ever support range variables, we'll probably also have to
976 do a little bit more work. */
979 convert (tree type
, tree expr
)
983 if (type
== error_mark_node
|| expr
== error_mark_node
)
984 return error_mark_node
;
986 intype
= TREE_TYPE (expr
);
988 if (POINTER_TYPE_P (type
) && POINTER_TYPE_P (intype
))
989 return fold_if_not_in_template (build_nop (type
, expr
));
991 return ocp_convert (type
, expr
, CONV_OLD_CONVERT
,
992 LOOKUP_NORMAL
|LOOKUP_NO_CONVERSION
);
995 /* Like cp_convert, except permit conversions to take place which
996 are not normally allowed due to access restrictions
997 (such as conversion from sub-type to private super-type). */
1000 convert_force (tree type
, tree expr
, int convtype
)
1003 enum tree_code code
= TREE_CODE (type
);
1005 if (code
== REFERENCE_TYPE
)
1006 return (fold_if_not_in_template
1007 (convert_to_reference (type
, e
, CONV_C_CAST
, LOOKUP_COMPLAIN
,
1010 if (code
== POINTER_TYPE
)
1011 return fold_if_not_in_template (convert_to_pointer_force (type
, e
));
1013 /* From typeck.c convert_for_assignment */
1014 if (((TREE_CODE (TREE_TYPE (e
)) == POINTER_TYPE
&& TREE_CODE (e
) == ADDR_EXPR
1015 && TREE_CODE (TREE_TYPE (e
)) == POINTER_TYPE
1016 && TREE_CODE (TREE_TYPE (TREE_TYPE (e
))) == METHOD_TYPE
)
1017 || integer_zerop (e
)
1018 || TYPE_PTRMEMFUNC_P (TREE_TYPE (e
)))
1019 && TYPE_PTRMEMFUNC_P (type
))
1020 /* compatible pointer to member functions. */
1021 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type
), e
, 1,
1024 return ocp_convert (type
, e
, CONV_C_CAST
|convtype
, LOOKUP_NORMAL
);
1027 /* Convert an aggregate EXPR to type XTYPE. If a conversion
1028 exists, return the attempted conversion. This may
1029 return ERROR_MARK_NODE if the conversion is not
1030 allowed (references private members, etc).
1031 If no conversion exists, NULL_TREE is returned.
1033 FIXME: Ambiguity checking is wrong. Should choose one by the implicit
1034 object parameter, or by the second standard conversion sequence if
1035 that doesn't do it. This will probably wait for an overloading rewrite.
1039 build_type_conversion (tree xtype
, tree expr
)
1041 /* C++: check to see if we can convert this aggregate type
1042 into the required type. */
1043 return build_user_type_conversion (xtype
, expr
, LOOKUP_NORMAL
);
1046 /* Convert the given EXPR to one of a group of types suitable for use in an
1047 expression. DESIRES is a combination of various WANT_* flags (q.v.)
1048 which indicates which types are suitable. If COMPLAIN is true, complain
1049 about ambiguity; otherwise, the caller will deal with it. */
1052 build_expr_type_conversion (int desires
, tree expr
, bool complain
)
1054 tree basetype
= TREE_TYPE (expr
);
1055 tree conv
= NULL_TREE
;
1056 tree winner
= NULL_TREE
;
1058 if (expr
== null_node
1059 && (desires
& WANT_INT
)
1060 && !(desires
& WANT_NULL
))
1061 warning (0, "converting NULL to non-pointer type");
1063 basetype
= TREE_TYPE (expr
);
1065 if (basetype
== error_mark_node
)
1066 return error_mark_node
;
1068 if (! IS_AGGR_TYPE (basetype
))
1069 switch (TREE_CODE (basetype
))
1072 if ((desires
& WANT_NULL
) && null_ptr_cst_p (expr
))
1074 /* else fall through... */
1078 return (desires
& WANT_INT
) ? expr
: NULL_TREE
;
1080 return (desires
& WANT_ENUM
) ? expr
: NULL_TREE
;
1082 return (desires
& WANT_FLOAT
) ? expr
: NULL_TREE
;
1084 return (desires
& WANT_POINTER
) ? expr
: NULL_TREE
;
1088 return (desires
& WANT_POINTER
) ? decay_conversion (expr
)
1094 /* The code for conversions from class type is currently only used for
1095 delete expressions. Other expressions are handled by build_new_op. */
1096 if (!complete_type_or_else (basetype
, expr
))
1097 return error_mark_node
;
1098 if (!TYPE_HAS_CONVERSION (basetype
))
1101 for (conv
= lookup_conversions (basetype
); conv
; conv
= TREE_CHAIN (conv
))
1105 tree cand
= TREE_VALUE (conv
);
1107 if (winner
&& winner
== cand
)
1110 candidate
= non_reference (TREE_TYPE (TREE_TYPE (cand
)));
1112 switch (TREE_CODE (candidate
))
1116 win
= (desires
& WANT_INT
); break;
1118 win
= (desires
& WANT_ENUM
); break;
1120 win
= (desires
& WANT_FLOAT
); break;
1122 win
= (desires
& WANT_POINTER
); break;
1134 error ("ambiguous default type conversion from %qT",
1136 error (" candidate conversions include %qD and %qD",
1139 return error_mark_node
;
1148 tree type
= non_reference (TREE_TYPE (TREE_TYPE (winner
)));
1149 return build_user_type_conversion (type
, expr
, LOOKUP_NORMAL
);
1155 /* Implements integral promotion (4.1) and float->double promotion. */
1158 type_promotes_to (tree type
)
1160 if (type
== error_mark_node
)
1161 return error_mark_node
;
1163 type
= TYPE_MAIN_VARIANT (type
);
1165 /* bool always promotes to int (not unsigned), even if it's the same
1167 if (type
== boolean_type_node
)
1168 type
= integer_type_node
;
1170 /* Normally convert enums to int, but convert wide enums to something
1172 else if (TREE_CODE (type
) == ENUMERAL_TYPE
1173 || type
== wchar_type_node
)
1175 int precision
= MAX (TYPE_PRECISION (type
),
1176 TYPE_PRECISION (integer_type_node
));
1177 tree totype
= c_common_type_for_size (precision
, 0);
1178 if (TYPE_UNSIGNED (type
)
1179 && ! int_fits_type_p (TYPE_MAX_VALUE (type
), totype
))
1180 type
= c_common_type_for_size (precision
, 1);
1184 else if (c_promoting_integer_type_p (type
))
1186 /* Retain unsignedness if really not getting bigger. */
1187 if (TYPE_UNSIGNED (type
)
1188 && TYPE_PRECISION (type
) == TYPE_PRECISION (integer_type_node
))
1189 type
= unsigned_type_node
;
1191 type
= integer_type_node
;
1193 else if (type
== float_type_node
)
1194 type
= double_type_node
;
1199 /* The routines below this point are carefully written to conform to
1200 the standard. They use the same terminology, and follow the rules
1201 closely. Although they are used only in pt.c at the moment, they
1202 should presumably be used everywhere in the future. */
1204 /* Attempt to perform qualification conversions on EXPR to convert it
1205 to TYPE. Return the resulting expression, or error_mark_node if
1206 the conversion was impossible. */
1209 perform_qualification_conversions (tree type
, tree expr
)
1213 expr_type
= TREE_TYPE (expr
);
1215 if (same_type_p (type
, expr_type
))
1217 else if (TYPE_PTR_P (type
) && TYPE_PTR_P (expr_type
)
1218 && comp_ptr_ttypes (TREE_TYPE (type
), TREE_TYPE (expr_type
)))
1219 return build_nop (type
, expr
);
1220 else if (TYPE_PTR_TO_MEMBER_P (type
)
1221 && TYPE_PTR_TO_MEMBER_P (expr_type
)
1222 && same_type_p (TYPE_PTRMEM_CLASS_TYPE (type
),
1223 TYPE_PTRMEM_CLASS_TYPE (expr_type
))
1224 && comp_ptr_ttypes (TYPE_PTRMEM_POINTED_TO_TYPE (type
),
1225 TYPE_PTRMEM_POINTED_TO_TYPE (expr_type
)))
1226 return build_nop (type
, expr
);
1228 return error_mark_node
;