1 /* Language-level data type conversion for GNU C++.
2 Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
3 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
4 2011 Free Software Foundation, Inc.
5 Hacked by Michael Tiemann (tiemann@cygnus.com)
6
7 This file is part of GCC.
8
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)
12 any later version.
13
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.
18
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/>. */
22
23
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. */
28
29 #include "config.h"
30 #include "system.h"
31 #include "coretypes.h"
32 #include "tm.h"
33 #include "tree.h"
34 #include "flags.h"
35 #include "cp-tree.h"
36 #include "intl.h"
37 #include "convert.h"
38 #include "decl.h"
39 #include "target.h"
40
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);
46
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.
50
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.
54
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.
63
64 C++: in multiple-inheritance, converting between pointers may involve
65 adjusting them by a delta stored within the class definition. */
66
67 /* Subroutines of `convert'. */
68
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
72 else convert blindly
73 else if converting class, pass off to build_type_conversion
74 else try C-style pointer conversion. */
75
76 static tree
cp_convert_to_pointer(tree type,tree expr)77 cp_convert_to_pointer (tree type, tree expr)
78 {
79 tree intype = TREE_TYPE (expr);
80 enum tree_code form;
81 tree rval;
82 if (intype == error_mark_node)
83 return error_mark_node;
84
85 if (MAYBE_CLASS_TYPE_P (intype))
86 {
87 intype = complete_type (intype);
88 if (!COMPLETE_TYPE_P (intype))
89 {
90 error ("can%'t convert from incomplete type %qT to %qT",
91 intype, type);
92 return error_mark_node;
93 }
94
95 rval = build_type_conversion (type, expr);
96 if (rval)
97 {
98 if (rval == error_mark_node)
99 error ("conversion of %qE from %qT to %qT is ambiguous",
100 expr, intype, type);
101 return rval;
102 }
103 }
104
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))))
109 {
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);
116 }
117
118 if (expr == error_mark_node)
119 return error_mark_node;
120
121 form = TREE_CODE (intype);
122
123 if (POINTER_TYPE_P (intype))
124 {
125 intype = TYPE_MAIN_VARIANT (intype);
126
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)
133 {
134 enum tree_code code = PLUS_EXPR;
135 tree binfo;
136 tree intype_class;
137 tree type_class;
138 bool same_p;
139
140 intype_class = TREE_TYPE (intype);
141 type_class = TREE_TYPE (type);
142
143 same_p = same_type_p (TYPE_MAIN_VARIANT (intype_class),
144 TYPE_MAIN_VARIANT (type_class));
145 binfo = NULL_TREE;
146 /* Try derived to base conversion. */
147 if (!same_p)
148 binfo = lookup_base (intype_class, type_class, ba_check, NULL);
149 if (!same_p && !binfo)
150 {
151 /* Try base to derived conversion. */
152 binfo = lookup_base (type_class, intype_class, ba_check, NULL);
153 code = MINUS_EXPR;
154 }
155 if (binfo == error_mark_node)
156 return error_mark_node;
157 if (binfo || same_p)
158 {
159 if (binfo)
160 expr = build_base_path (code, expr, binfo, 0,
161 tf_warning_or_error);
162 /* Add any qualifier conversions. */
163 return build_nop (type, expr);
164 }
165 }
166
167 if (TYPE_PTRMEMFUNC_P (type))
168 {
169 error ("cannot convert %qE from type %qT to type %qT",
170 expr, intype, type);
171 return error_mark_node;
172 }
173
174 return build_nop (type, expr);
175 }
176 else if ((TYPE_PTRMEM_P (type) && TYPE_PTRMEM_P (intype))
177 || (TYPE_PTRMEMFUNC_P (type) && TYPE_PTRMEMFUNC_P (intype)))
178 return convert_ptrmem (type, expr, /*allow_inverse_p=*/false,
179 /*c_cast_p=*/false, tf_warning_or_error);
180 else if (TYPE_PTRMEMFUNC_P (intype))
181 {
182 if (!warn_pmf2ptr)
183 {
184 if (TREE_CODE (expr) == PTRMEM_CST)
185 return cp_convert_to_pointer (type,
186 PTRMEM_CST_MEMBER (expr));
187 else if (TREE_CODE (expr) == OFFSET_REF)
188 {
189 tree object = TREE_OPERAND (expr, 0);
190 return get_member_function_from_ptrfunc (&object,
191 TREE_OPERAND (expr, 1));
192 }
193 }
194 error ("cannot convert %qE from type %qT to type %qT",
195 expr, intype, type);
196 return error_mark_node;
197 }
198
199 if (null_ptr_cst_p (expr))
200 {
201 tree val;
202
203 if (c_inhibit_evaluation_warnings == 0
204 && !NULLPTR_TYPE_P (TREE_TYPE (expr)))
205 warning (OPT_Wzero_as_null_pointer_constant,
206 "zero as null pointer constant");
207
208 if (TYPE_PTRMEMFUNC_P (type))
209 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), expr, 0,
210 /*c_cast_p=*/false, tf_warning_or_error);
211
212 /* A NULL pointer-to-data-member is represented by -1, not by
213 zero. */
214 val = (TYPE_PTRMEM_P (type)
215 ? build_int_cst_type (type, -1)
216 : build_int_cst (type, 0));
217
218 return (TREE_SIDE_EFFECTS (expr)
219 ? build2 (COMPOUND_EXPR, type, expr, val) : val);
220 }
221 else if (TYPE_PTR_TO_MEMBER_P (type) && INTEGRAL_CODE_P (form))
222 {
223 error ("invalid conversion from %qT to %qT", intype, type);
224 return error_mark_node;
225 }
226
227 if (INTEGRAL_CODE_P (form))
228 {
229 if (TYPE_PRECISION (intype) == POINTER_SIZE)
230 return build1 (CONVERT_EXPR, type, expr);
231 expr = cp_convert (c_common_type_for_size (POINTER_SIZE, 0), expr);
232 /* Modes may be different but sizes should be the same. There
233 is supposed to be some integral type that is the same width
234 as a pointer. */
235 gcc_assert (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (expr)))
236 == GET_MODE_SIZE (TYPE_MODE (type)));
237
238 return convert_to_pointer (type, expr);
239 }
240
241 if (type_unknown_p (expr))
242 return instantiate_type (type, expr, tf_warning_or_error);
243
244 error ("cannot convert %qE from type %qT to type %qT",
245 expr, intype, type);
246 return error_mark_node;
247 }
248
249 /* Like convert, except permit conversions to take place which
250 are not normally allowed due to access restrictions
251 (such as conversion from sub-type to private super-type). */
252
253 static tree
convert_to_pointer_force(tree type,tree expr)254 convert_to_pointer_force (tree type, tree expr)
255 {
256 tree intype = TREE_TYPE (expr);
257 enum tree_code form = TREE_CODE (intype);
258
259 if (form == POINTER_TYPE)
260 {
261 intype = TYPE_MAIN_VARIANT (intype);
262
263 if (TYPE_MAIN_VARIANT (type) != intype
264 && TREE_CODE (TREE_TYPE (type)) == RECORD_TYPE
265 && MAYBE_CLASS_TYPE_P (TREE_TYPE (type))
266 && MAYBE_CLASS_TYPE_P (TREE_TYPE (intype))
267 && TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE)
268 {
269 enum tree_code code = PLUS_EXPR;
270 tree binfo;
271
272 binfo = lookup_base (TREE_TYPE (intype), TREE_TYPE (type),
273 ba_unique, NULL);
274 if (!binfo)
275 {
276 binfo = lookup_base (TREE_TYPE (type), TREE_TYPE (intype),
277 ba_unique, NULL);
278 code = MINUS_EXPR;
279 }
280 if (binfo == error_mark_node)
281 return error_mark_node;
282 if (binfo)
283 {
284 expr = build_base_path (code, expr, binfo, 0,
285 tf_warning_or_error);
286 if (expr == error_mark_node)
287 return error_mark_node;
288 /* Add any qualifier conversions. */
289 if (!same_type_p (TREE_TYPE (TREE_TYPE (expr)),
290 TREE_TYPE (type)))
291 expr = build_nop (type, expr);
292 return expr;
293 }
294 }
295 }
296
297 return cp_convert_to_pointer (type, expr);
298 }
299
300 /* We are passing something to a function which requires a reference.
301 The type we are interested in is in TYPE. The initial
302 value we have to begin with is in ARG.
303
304 FLAGS controls how we manage access checking.
305 DIRECT_BIND in FLAGS controls how any temporaries are generated.
306 If DIRECT_BIND is set, DECL is the reference we're binding to. */
307
308 static tree
build_up_reference(tree type,tree arg,int flags,tree decl)309 build_up_reference (tree type, tree arg, int flags, tree decl)
310 {
311 tree rval;
312 tree argtype = TREE_TYPE (arg);
313 tree target_type = TREE_TYPE (type);
314
315 gcc_assert (TREE_CODE (type) == REFERENCE_TYPE);
316
317 if ((flags & DIRECT_BIND) && ! real_lvalue_p (arg))
318 {
319 /* Create a new temporary variable. We can't just use a TARGET_EXPR
320 here because it needs to live as long as DECL. */
321 tree targ = arg;
322
323 arg = make_temporary_var_for_ref_to_temp (decl, target_type);
324
325 /* Process the initializer for the declaration. */
326 DECL_INITIAL (arg) = targ;
327 cp_finish_decl (arg, targ, /*init_const_expr_p=*/false, NULL_TREE,
328 LOOKUP_ONLYCONVERTING|DIRECT_BIND);
329 }
330 else if (!(flags & DIRECT_BIND) && ! lvalue_p (arg))
331 return get_target_expr (arg);
332
333 /* If we had a way to wrap this up, and say, if we ever needed its
334 address, transform all occurrences of the register, into a memory
335 reference we could win better. */
336 rval = cp_build_addr_expr (arg, tf_warning_or_error);
337 if (rval == error_mark_node)
338 return error_mark_node;
339
340 if ((flags & LOOKUP_PROTECT)
341 && TYPE_MAIN_VARIANT (argtype) != TYPE_MAIN_VARIANT (target_type)
342 && MAYBE_CLASS_TYPE_P (argtype)
343 && MAYBE_CLASS_TYPE_P (target_type))
344 {
345 /* We go through lookup_base for the access control. */
346 tree binfo = lookup_base (argtype, target_type, ba_check, NULL);
347 if (binfo == error_mark_node)
348 return error_mark_node;
349 if (binfo == NULL_TREE)
350 return error_not_base_type (target_type, argtype);
351 rval = build_base_path (PLUS_EXPR, rval, binfo, 1,
352 tf_warning_or_error);
353 }
354 else
355 rval
356 = convert_to_pointer_force (build_pointer_type (target_type), rval);
357 return build_nop (type, rval);
358 }
359
360 /* Subroutine of convert_to_reference. REFTYPE is the target reference type.
361 INTYPE is the original rvalue type and DECL is an optional _DECL node
362 for diagnostics.
363
364 [dcl.init.ref] says that if an rvalue is used to
365 initialize a reference, then the reference must be to a
366 non-volatile const type. */
367
368 static void
warn_ref_binding(tree reftype,tree intype,tree decl)369 warn_ref_binding (tree reftype, tree intype, tree decl)
370 {
371 tree ttl = TREE_TYPE (reftype);
372
373 if (!CP_TYPE_CONST_NON_VOLATILE_P (ttl))
374 {
375 const char *msg;
376
377 if (CP_TYPE_VOLATILE_P (ttl) && decl)
378 msg = G_("initialization of volatile reference type %q#T from "
379 "rvalue of type %qT");
380 else if (CP_TYPE_VOLATILE_P (ttl))
381 msg = G_("conversion to volatile reference type %q#T "
382 "from rvalue of type %qT");
383 else if (decl)
384 msg = G_("initialization of non-const reference type %q#T from "
385 "rvalue of type %qT");
386 else
387 msg = G_("conversion to non-const reference type %q#T from "
388 "rvalue of type %qT");
389
390 permerror (input_location, msg, reftype, intype);
391 }
392 }
393
394 /* For C++: Only need to do one-level references, but cannot
395 get tripped up on signed/unsigned differences.
396
397 DECL is either NULL_TREE or the _DECL node for a reference that is being
398 initialized. It can be error_mark_node if we don't know the _DECL but
399 we know it's an initialization. */
400
401 tree
convert_to_reference(tree reftype,tree expr,int convtype,int flags,tree decl)402 convert_to_reference (tree reftype, tree expr, int convtype,
403 int flags, tree decl)
404 {
405 tree type = TYPE_MAIN_VARIANT (TREE_TYPE (reftype));
406 tree intype;
407 tree rval = NULL_TREE;
408 tree rval_as_conversion = NULL_TREE;
409 bool can_convert_intype_to_type;
410
411 if (TREE_CODE (type) == FUNCTION_TYPE
412 && TREE_TYPE (expr) == unknown_type_node)
413 expr = instantiate_type (type, expr,
414 (flags & LOOKUP_COMPLAIN)
415 ? tf_warning_or_error : tf_none);
416
417 if (expr == error_mark_node)
418 return error_mark_node;
419
420 intype = TREE_TYPE (expr);
421
422 gcc_assert (TREE_CODE (intype) != REFERENCE_TYPE);
423 gcc_assert (TREE_CODE (reftype) == REFERENCE_TYPE);
424
425 intype = TYPE_MAIN_VARIANT (intype);
426
427 can_convert_intype_to_type = can_convert (type, intype);
428 if (!can_convert_intype_to_type
429 && (convtype & CONV_IMPLICIT) && MAYBE_CLASS_TYPE_P (intype)
430 && ! (flags & LOOKUP_NO_CONVERSION))
431 {
432 /* Look for a user-defined conversion to lvalue that we can use. */
433
434 rval_as_conversion
435 = build_type_conversion (reftype, expr);
436
437 if (rval_as_conversion && rval_as_conversion != error_mark_node
438 && real_lvalue_p (rval_as_conversion))
439 {
440 expr = rval_as_conversion;
441 rval_as_conversion = NULL_TREE;
442 intype = type;
443 can_convert_intype_to_type = 1;
444 }
445 }
446
447 if (((convtype & CONV_STATIC) && can_convert (intype, type))
448 || ((convtype & CONV_IMPLICIT) && can_convert_intype_to_type))
449 {
450 if (flags & LOOKUP_COMPLAIN)
451 {
452 tree ttl = TREE_TYPE (reftype);
453 tree ttr = lvalue_type (expr);
454
455 if (! real_lvalue_p (expr))
456 warn_ref_binding (reftype, intype, decl);
457
458 if (! (convtype & CONV_CONST)
459 && !at_least_as_qualified_p (ttl, ttr))
460 permerror (input_location, "conversion from %qT to %qT discards qualifiers",
461 ttr, reftype);
462 }
463
464 return build_up_reference (reftype, expr, flags, decl);
465 }
466 else if ((convtype & CONV_REINTERPRET) && lvalue_p (expr))
467 {
468 /* When casting an lvalue to a reference type, just convert into
469 a pointer to the new type and deference it. This is allowed
470 by San Diego WP section 5.2.9 paragraph 12, though perhaps it
471 should be done directly (jason). (int &)ri ---> *(int*)&ri */
472
473 /* B* bp; A& ar = (A&)bp; is valid, but it's probably not what they
474 meant. */
475 if (TREE_CODE (intype) == POINTER_TYPE
476 && (comptypes (TREE_TYPE (intype), type,
477 COMPARE_BASE | COMPARE_DERIVED)))
478 warning (0, "casting %qT to %qT does not dereference pointer",
479 intype, reftype);
480
481 rval = cp_build_addr_expr (expr, tf_warning_or_error);
482 if (rval != error_mark_node)
483 rval = convert_force (build_pointer_type (TREE_TYPE (reftype)),
484 rval, 0);
485 if (rval != error_mark_node)
486 rval = build1 (NOP_EXPR, reftype, rval);
487 }
488 else
489 {
490 rval = convert_for_initialization (NULL_TREE, type, expr, flags,
491 ICR_CONVERTING, 0, 0,
492 tf_warning_or_error);
493 if (rval == NULL_TREE || rval == error_mark_node)
494 return rval;
495 warn_ref_binding (reftype, intype, decl);
496 rval = build_up_reference (reftype, rval, flags, decl);
497 }
498
499 if (rval)
500 {
501 /* If we found a way to convert earlier, then use it. */
502 return rval;
503 }
504
505 if (flags & LOOKUP_COMPLAIN)
506 error ("cannot convert type %qT to type %qT", intype, reftype);
507
508 return error_mark_node;
509 }
510
511 /* We are using a reference VAL for its value. Bash that reference all the
512 way down to its lowest form. */
513
514 tree
convert_from_reference(tree val)515 convert_from_reference (tree val)
516 {
517 if (TREE_TYPE (val)
518 && TREE_CODE (TREE_TYPE (val)) == REFERENCE_TYPE)
519 {
520 tree t = TREE_TYPE (TREE_TYPE (val));
521 tree ref = build1 (INDIRECT_REF, t, val);
522
523 mark_exp_read (val);
524 /* We *must* set TREE_READONLY when dereferencing a pointer to const,
525 so that we get the proper error message if the result is used
526 to assign to. Also, &* is supposed to be a no-op. */
527 TREE_READONLY (ref) = CP_TYPE_CONST_P (t);
528 TREE_THIS_VOLATILE (ref) = CP_TYPE_VOLATILE_P (t);
529 TREE_SIDE_EFFECTS (ref)
530 = (TREE_THIS_VOLATILE (ref) || TREE_SIDE_EFFECTS (val));
531 val = ref;
532 }
533
534 return val;
535 }
536
537 /* Really perform an lvalue-to-rvalue conversion, including copying an
538 argument of class type into a temporary. */
539
540 tree
force_rvalue(tree expr,tsubst_flags_t complain)541 force_rvalue (tree expr, tsubst_flags_t complain)
542 {
543 tree type = TREE_TYPE (expr);
544 if (MAYBE_CLASS_TYPE_P (type) && TREE_CODE (expr) != TARGET_EXPR)
545 {
546 VEC(tree,gc) *args = make_tree_vector_single (expr);
547 expr = build_special_member_call (NULL_TREE, complete_ctor_identifier,
548 &args, type, LOOKUP_NORMAL, complain);
549 release_tree_vector (args);
550 expr = build_cplus_new (type, expr, complain);
551 }
552 else
553 expr = decay_conversion (expr);
554
555 return expr;
556 }
557
558
559 /* If EXPR and ORIG are INTEGER_CSTs, return a version of EXPR that has
560 TREE_OVERFLOW set only if it is set in ORIG. Otherwise, return EXPR
561 unchanged. */
562
563 static tree
ignore_overflows(tree expr,tree orig)564 ignore_overflows (tree expr, tree orig)
565 {
566 if (TREE_CODE (expr) == INTEGER_CST
567 && TREE_CODE (orig) == INTEGER_CST
568 && TREE_OVERFLOW (expr) != TREE_OVERFLOW (orig))
569 {
570 gcc_assert (!TREE_OVERFLOW (orig));
571 /* Ensure constant sharing. */
572 expr = build_int_cst_wide (TREE_TYPE (expr),
573 TREE_INT_CST_LOW (expr),
574 TREE_INT_CST_HIGH (expr));
575 }
576 return expr;
577 }
578
579 /* Fold away simple conversions, but make sure TREE_OVERFLOW is set
580 properly. */
581
582 tree
cp_fold_convert(tree type,tree expr)583 cp_fold_convert (tree type, tree expr)
584 {
585 tree conv = fold_convert (type, expr);
586 conv = ignore_overflows (conv, expr);
587 return conv;
588 }
589
590 /* C++ conversions, preference to static cast conversions. */
591
592 tree
cp_convert(tree type,tree expr)593 cp_convert (tree type, tree expr)
594 {
595 return ocp_convert (type, expr, CONV_OLD_CONVERT, LOOKUP_NORMAL);
596 }
597
598 /* C++ equivalent of convert_and_check but using cp_convert as the
599 conversion function.
600
601 Convert EXPR to TYPE, warning about conversion problems with constants.
602 Invoke this function on every expression that is converted implicitly,
603 i.e. because of language rules and not because of an explicit cast. */
604
605 tree
cp_convert_and_check(tree type,tree expr)606 cp_convert_and_check (tree type, tree expr)
607 {
608 tree result;
609
610 if (TREE_TYPE (expr) == type)
611 return expr;
612
613 result = cp_convert (type, expr);
614
615 if (c_inhibit_evaluation_warnings == 0
616 && !TREE_OVERFLOW_P (expr)
617 && result != error_mark_node)
618 warnings_for_convert_and_check (type, expr, result);
619
620 return result;
621 }
622
623 /* Conversion...
624
625 FLAGS indicates how we should behave. */
626
627 tree
ocp_convert(tree type,tree expr,int convtype,int flags)628 ocp_convert (tree type, tree expr, int convtype, int flags)
629 {
630 tree e = expr;
631 enum tree_code code = TREE_CODE (type);
632 const char *invalid_conv_diag;
633 tree e1;
634
635 if (error_operand_p (e) || type == error_mark_node)
636 return error_mark_node;
637
638 complete_type (type);
639 complete_type (TREE_TYPE (expr));
640
641 if ((invalid_conv_diag
642 = targetm.invalid_conversion (TREE_TYPE (expr), type)))
643 {
644 error (invalid_conv_diag);
645 return error_mark_node;
646 }
647
648 /* FIXME remove when moving to c_fully_fold model. */
649 /* FIXME do we still need this test? */
650 if (!CLASS_TYPE_P (type))
651 e = integral_constant_value (e);
652 if (error_operand_p (e))
653 return error_mark_node;
654
655 if (MAYBE_CLASS_TYPE_P (type) && (convtype & CONV_FORCE_TEMP))
656 /* We need a new temporary; don't take this shortcut. */;
657 else if (same_type_ignoring_top_level_qualifiers_p (type, TREE_TYPE (e)))
658 {
659 if (same_type_p (type, TREE_TYPE (e)))
660 /* The call to fold will not always remove the NOP_EXPR as
661 might be expected, since if one of the types is a typedef;
662 the comparison in fold is just equality of pointers, not a
663 call to comptypes. We don't call fold in this case because
664 that can result in infinite recursion; fold will call
665 convert, which will call ocp_convert, etc. */
666 return e;
667 /* For complex data types, we need to perform componentwise
668 conversion. */
669 else if (TREE_CODE (type) == COMPLEX_TYPE)
670 return fold_if_not_in_template (convert_to_complex (type, e));
671 else if (TREE_CODE (e) == TARGET_EXPR)
672 {
673 /* Don't build a NOP_EXPR of class type. Instead, change the
674 type of the temporary. */
675 TREE_TYPE (e) = TREE_TYPE (TARGET_EXPR_SLOT (e)) = type;
676 return e;
677 }
678 else
679 {
680 /* We shouldn't be treating objects of ADDRESSABLE type as
681 rvalues. */
682 gcc_assert (!TREE_ADDRESSABLE (type));
683 return fold_if_not_in_template (build_nop (type, e));
684 }
685 }
686
687 e1 = targetm.convert_to_type (type, e);
688 if (e1)
689 return e1;
690
691 if (code == VOID_TYPE && (convtype & CONV_STATIC))
692 {
693 e = convert_to_void (e, ICV_CAST, tf_warning_or_error);
694 return e;
695 }
696
697 if (INTEGRAL_CODE_P (code))
698 {
699 tree intype = TREE_TYPE (e);
700 tree converted;
701
702 if (TREE_CODE (type) == ENUMERAL_TYPE)
703 {
704 /* enum = enum, enum = int, enum = float, (enum)pointer are all
705 errors. */
706 if (((INTEGRAL_OR_ENUMERATION_TYPE_P (intype)
707 || TREE_CODE (intype) == REAL_TYPE)
708 && ! (convtype & CONV_STATIC))
709 || TREE_CODE (intype) == POINTER_TYPE)
710 {
711 if (flags & LOOKUP_COMPLAIN)
712 permerror (input_location, "conversion from %q#T to %q#T", intype, type);
713
714 if (!flag_permissive)
715 return error_mark_node;
716 }
717
718 /* [expr.static.cast]
719
720 8. A value of integral or enumeration type can be explicitly
721 converted to an enumeration type. The value is unchanged if
722 the original value is within the range of the enumeration
723 values. Otherwise, the resulting enumeration value is
724 unspecified. */
725 if (TREE_CODE (expr) == INTEGER_CST
726 && !int_fits_type_p (expr, ENUM_UNDERLYING_TYPE (type)))
727 warning (OPT_Wconversion,
728 "the result of the conversion is unspecified because "
729 "%qE is outside the range of type %qT",
730 expr, type);
731 }
732 if (MAYBE_CLASS_TYPE_P (intype))
733 {
734 tree rval;
735 rval = build_type_conversion (type, e);
736 if (rval)
737 return rval;
738 if (flags & LOOKUP_COMPLAIN)
739 error ("%q#T used where a %qT was expected", intype, type);
740 return error_mark_node;
741 }
742 if (code == BOOLEAN_TYPE)
743 {
744 /* We can't implicitly convert a scoped enum to bool, so convert
745 to the underlying type first. */
746 if (SCOPED_ENUM_P (intype) && (convtype & CONV_STATIC))
747 e = build_nop (ENUM_UNDERLYING_TYPE (intype), e);
748 return cp_truthvalue_conversion (e);
749 }
750
751 converted = fold_if_not_in_template (convert_to_integer (type, e));
752
753 /* Ignore any integer overflow caused by the conversion. */
754 return ignore_overflows (converted, e);
755 }
756 if (NULLPTR_TYPE_P (type) && e && null_ptr_cst_p (e))
757 return nullptr_node;
758 if (POINTER_TYPE_P (type) || TYPE_PTR_TO_MEMBER_P (type))
759 return fold_if_not_in_template (cp_convert_to_pointer (type, e));
760 if (code == VECTOR_TYPE)
761 {
762 tree in_vtype = TREE_TYPE (e);
763 if (MAYBE_CLASS_TYPE_P (in_vtype))
764 {
765 tree ret_val;
766 ret_val = build_type_conversion (type, e);
767 if (ret_val)
768 return ret_val;
769 if (flags & LOOKUP_COMPLAIN)
770 error ("%q#T used where a %qT was expected", in_vtype, type);
771 return error_mark_node;
772 }
773 return fold_if_not_in_template (convert_to_vector (type, e));
774 }
775 if (code == REAL_TYPE || code == COMPLEX_TYPE)
776 {
777 if (MAYBE_CLASS_TYPE_P (TREE_TYPE (e)))
778 {
779 tree rval;
780 rval = build_type_conversion (type, e);
781 if (rval)
782 return rval;
783 else
784 if (flags & LOOKUP_COMPLAIN)
785 error ("%q#T used where a floating point value was expected",
786 TREE_TYPE (e));
787 }
788 if (code == REAL_TYPE)
789 return fold_if_not_in_template (convert_to_real (type, e));
790 else if (code == COMPLEX_TYPE)
791 return fold_if_not_in_template (convert_to_complex (type, e));
792 }
793
794 /* New C++ semantics: since assignment is now based on
795 memberwise copying, if the rhs type is derived from the
796 lhs type, then we may still do a conversion. */
797 if (RECORD_OR_UNION_CODE_P (code))
798 {
799 tree dtype = TREE_TYPE (e);
800 tree ctor = NULL_TREE;
801
802 dtype = TYPE_MAIN_VARIANT (dtype);
803
804 /* Conversion between aggregate types. New C++ semantics allow
805 objects of derived type to be cast to objects of base type.
806 Old semantics only allowed this between pointers.
807
808 There may be some ambiguity between using a constructor
809 vs. using a type conversion operator when both apply. */
810
811 ctor = e;
812
813 if (abstract_virtuals_error (NULL_TREE, type))
814 return error_mark_node;
815
816 if (BRACE_ENCLOSED_INITIALIZER_P (ctor))
817 ctor = perform_implicit_conversion (type, ctor, tf_warning_or_error);
818 else if ((flags & LOOKUP_ONLYCONVERTING)
819 && ! (CLASS_TYPE_P (dtype) && DERIVED_FROM_P (type, dtype)))
820 /* For copy-initialization, first we create a temp of the proper type
821 with a user-defined conversion sequence, then we direct-initialize
822 the target with the temp (see [dcl.init]). */
823 ctor = build_user_type_conversion (type, ctor, flags);
824 else
825 {
826 VEC(tree,gc) *ctor_vec = make_tree_vector_single (ctor);
827 ctor = build_special_member_call (NULL_TREE,
828 complete_ctor_identifier,
829 &ctor_vec,
830 type, flags,
831 tf_warning_or_error);
832 release_tree_vector (ctor_vec);
833 }
834 if (ctor)
835 return build_cplus_new (type, ctor, tf_warning_or_error);
836 }
837
838 if (flags & LOOKUP_COMPLAIN)
839 {
840 /* If the conversion failed and expr was an invalid use of pointer to
841 member function, try to report a meaningful error. */
842 if (invalid_nonstatic_memfn_p (expr, tf_warning_or_error))
843 /* We displayed the error message. */;
844 else
845 error ("conversion from %qT to non-scalar type %qT requested",
846 TREE_TYPE (expr), type);
847 }
848 return error_mark_node;
849 }
850
851 /* When an expression is used in a void context, its value is discarded and
852 no lvalue-rvalue and similar conversions happen [expr.static.cast/4,
853 stmt.expr/1, expr.comma/1]. This permits dereferencing an incomplete type
854 in a void context. The C++ standard does not define what an `access' to an
855 object is, but there is reason to believe that it is the lvalue to rvalue
856 conversion -- if it were not, `*&*p = 1' would violate [expr]/4 in that it
857 accesses `*p' not to calculate the value to be stored. But, dcl.type.cv/8
858 indicates that volatile semantics should be the same between C and C++
859 where ever possible. C leaves it implementation defined as to what
860 constitutes an access to a volatile. So, we interpret `*vp' as a read of
861 the volatile object `vp' points to, unless that is an incomplete type. For
862 volatile references we do not do this interpretation, because that would
863 make it impossible to ignore the reference return value from functions. We
864 issue warnings in the confusing cases.
865
866 The IMPLICIT is ICV_CAST when the user is explicitly converting an expression
867 to void via a cast. If an expression is being implicitly converted, IMPLICIT
868 indicates the context of the implicit conversion. */
869
870 tree
convert_to_void(tree expr,impl_conv_void implicit,tsubst_flags_t complain)871 convert_to_void (tree expr, impl_conv_void implicit, tsubst_flags_t complain)
872 {
873 if (expr == error_mark_node
874 || TREE_TYPE (expr) == error_mark_node)
875 return error_mark_node;
876
877 if (implicit == ICV_CAST)
878 mark_exp_read (expr);
879 else
880 {
881 tree exprv = expr;
882
883 while (TREE_CODE (exprv) == COMPOUND_EXPR)
884 exprv = TREE_OPERAND (exprv, 1);
885 if (DECL_P (exprv)
886 || handled_component_p (exprv)
887 || TREE_CODE (exprv) == INDIRECT_REF)
888 /* Expr is not being 'used' here, otherwise we whould have
889 called mark_{rl}value_use use here, which would have in turn
890 called mark_exp_read. Rather, we call mark_exp_read directly
891 to avoid some warnings when
892 -Wunused-but-set-{variable,parameter} is in effect. */
893 mark_exp_read (exprv);
894 }
895
896 if (!TREE_TYPE (expr))
897 return expr;
898 if (invalid_nonstatic_memfn_p (expr, complain))
899 return error_mark_node;
900 if (TREE_CODE (expr) == PSEUDO_DTOR_EXPR)
901 {
902 if (complain & tf_error)
903 error ("pseudo-destructor is not called");
904 return error_mark_node;
905 }
906 if (VOID_TYPE_P (TREE_TYPE (expr)))
907 return expr;
908 switch (TREE_CODE (expr))
909 {
910 case COND_EXPR:
911 {
912 /* The two parts of a cond expr might be separate lvalues. */
913 tree op1 = TREE_OPERAND (expr,1);
914 tree op2 = TREE_OPERAND (expr,2);
915 bool side_effects = ((op1 && TREE_SIDE_EFFECTS (op1))
916 || TREE_SIDE_EFFECTS (op2));
917 tree new_op1, new_op2;
918 new_op1 = NULL_TREE;
919 if (implicit != ICV_CAST && !side_effects)
920 {
921 if (op1)
922 new_op1 = convert_to_void (op1, ICV_SECOND_OF_COND, complain);
923 new_op2 = convert_to_void (op2, ICV_THIRD_OF_COND, complain);
924 }
925 else
926 {
927 if (op1)
928 new_op1 = convert_to_void (op1, ICV_CAST, complain);
929 new_op2 = convert_to_void (op2, ICV_CAST, complain);
930 }
931
932 expr = build3 (COND_EXPR, TREE_TYPE (new_op2),
933 TREE_OPERAND (expr, 0), new_op1, new_op2);
934 break;
935 }
936
937 case COMPOUND_EXPR:
938 {
939 /* The second part of a compound expr contains the value. */
940 tree op1 = TREE_OPERAND (expr,1);
941 tree new_op1;
942 if (implicit != ICV_CAST && !TREE_NO_WARNING (expr))
943 new_op1 = convert_to_void (op1, ICV_RIGHT_OF_COMMA, complain);
944 else
945 new_op1 = convert_to_void (op1, ICV_CAST, complain);
946
947 if (new_op1 != op1)
948 {
949 tree t = build2 (COMPOUND_EXPR, TREE_TYPE (new_op1),
950 TREE_OPERAND (expr, 0), new_op1);
951 expr = t;
952 }
953
954 break;
955 }
956
957 case NON_LVALUE_EXPR:
958 case NOP_EXPR:
959 /* These have already decayed to rvalue. */
960 break;
961
962 case CALL_EXPR: /* We have a special meaning for volatile void fn(). */
963 break;
964
965 case INDIRECT_REF:
966 {
967 tree type = TREE_TYPE (expr);
968 int is_reference = TREE_CODE (TREE_TYPE (TREE_OPERAND (expr, 0)))
969 == REFERENCE_TYPE;
970 int is_volatile = TYPE_VOLATILE (type);
971 int is_complete = COMPLETE_TYPE_P (complete_type (type));
972
973 /* Can't load the value if we don't know the type. */
974 if (is_volatile && !is_complete)
975 {
976 if (complain & tf_warning)
977 switch (implicit)
978 {
979 case ICV_CAST:
980 warning (0, "conversion to void will not access "
981 "object of incomplete type %qT", type);
982 break;
983 case ICV_SECOND_OF_COND:
984 warning (0, "indirection will not access object of "
985 "incomplete type %qT in second operand "
986 "of conditional expression", type);
987 break;
988 case ICV_THIRD_OF_COND:
989 warning (0, "indirection will not access object of "
990 "incomplete type %qT in third operand "
991 "of conditional expression", type);
992 break;
993 case ICV_RIGHT_OF_COMMA:
994 warning (0, "indirection will not access object of "
995 "incomplete type %qT in right operand of "
996 "comma operator", type);
997 break;
998 case ICV_LEFT_OF_COMMA:
999 warning (0, "indirection will not access object of "
1000 "incomplete type %qT in left operand of "
1001 "comma operator", type);
1002 break;
1003 case ICV_STATEMENT:
1004 warning (0, "indirection will not access object of "
1005 "incomplete type %qT in statement", type);
1006 break;
1007 case ICV_THIRD_IN_FOR:
1008 warning (0, "indirection will not access object of "
1009 "incomplete type %qT in for increment "
1010 "expression", type);
1011 break;
1012 default:
1013 gcc_unreachable ();
1014 }
1015 }
1016 /* Don't load the value if this is an implicit dereference, or if
1017 the type needs to be handled by ctors/dtors. */
1018 else if (is_volatile && is_reference)
1019 {
1020 if (complain & tf_warning)
1021 switch (implicit)
1022 {
1023 case ICV_CAST:
1024 warning (0, "conversion to void will not access "
1025 "object of type %qT", type);
1026 break;
1027 case ICV_SECOND_OF_COND:
1028 warning (0, "implicit dereference will not access object "
1029 "of type %qT in second operand of "
1030 "conditional expression", type);
1031 break;
1032 case ICV_THIRD_OF_COND:
1033 warning (0, "implicit dereference will not access object "
1034 "of type %qT in third operand of "
1035 "conditional expression", type);
1036 break;
1037 case ICV_RIGHT_OF_COMMA:
1038 warning (0, "implicit dereference will not access object "
1039 "of type %qT in right operand of "
1040 "comma operator", type);
1041 break;
1042 case ICV_LEFT_OF_COMMA:
1043 warning (0, "implicit dereference will not access object "
1044 "of type %qT in left operand of comma operator",
1045 type);
1046 break;
1047 case ICV_STATEMENT:
1048 warning (0, "implicit dereference will not access object "
1049 "of type %qT in statement", type);
1050 break;
1051 case ICV_THIRD_IN_FOR:
1052 warning (0, "implicit dereference will not access object "
1053 "of type %qT in for increment expression",
1054 type);
1055 break;
1056 default:
1057 gcc_unreachable ();
1058 }
1059 }
1060 else if (is_volatile && TREE_ADDRESSABLE (type))
1061 {
1062 if (complain & tf_warning)
1063 switch (implicit)
1064 {
1065 case ICV_CAST:
1066 warning (0, "conversion to void will not access "
1067 "object of non-trivially-copyable type %qT",
1068 type);
1069 break;
1070 case ICV_SECOND_OF_COND:
1071 warning (0, "indirection will not access object of "
1072 "non-trivially-copyable type %qT in second "
1073 "operand of conditional expression", type);
1074 break;
1075 case ICV_THIRD_OF_COND:
1076 warning (0, "indirection will not access object of "
1077 "non-trivially-copyable type %qT in third "
1078 "operand of conditional expression", type);
1079 break;
1080 case ICV_RIGHT_OF_COMMA:
1081 warning (0, "indirection will not access object of "
1082 "non-trivially-copyable type %qT in right "
1083 "operand of comma operator", type);
1084 break;
1085 case ICV_LEFT_OF_COMMA:
1086 warning (0, "indirection will not access object of "
1087 "non-trivially-copyable type %qT in left "
1088 "operand of comma operator", type);
1089 break;
1090 case ICV_STATEMENT:
1091 warning (0, "indirection will not access object of "
1092 "non-trivially-copyable type %qT in statement",
1093 type);
1094 break;
1095 case ICV_THIRD_IN_FOR:
1096 warning (0, "indirection will not access object of "
1097 "non-trivially-copyable type %qT in for "
1098 "increment expression", type);
1099 break;
1100 default:
1101 gcc_unreachable ();
1102 }
1103 }
1104 if (is_reference || !is_volatile || !is_complete || TREE_ADDRESSABLE (type))
1105 {
1106 /* Emit a warning (if enabled) when the "effect-less" INDIRECT_REF
1107 operation is stripped off. Note that we don't warn about
1108 - an expression with TREE_NO_WARNING set. (For an example of
1109 such expressions, see build_over_call in call.c.)
1110 - automatic dereferencing of references, since the user cannot
1111 control it. (See also warn_if_unused_value() in stmt.c.) */
1112 if (warn_unused_value
1113 && implicit != ICV_CAST
1114 && (complain & tf_warning)
1115 && !TREE_NO_WARNING (expr)
1116 && !is_reference)
1117 warning (OPT_Wunused_value, "value computed is not used");
1118 expr = TREE_OPERAND (expr, 0);
1119 }
1120
1121 break;
1122 }
1123
1124 case VAR_DECL:
1125 {
1126 /* External variables might be incomplete. */
1127 tree type = TREE_TYPE (expr);
1128 int is_complete = COMPLETE_TYPE_P (complete_type (type));
1129
1130 if (TYPE_VOLATILE (type) && !is_complete && (complain & tf_warning))
1131 switch (implicit)
1132 {
1133 case ICV_CAST:
1134 warning (0, "conversion to void will not access "
1135 "object %qE of incomplete type %qT", expr, type);
1136 break;
1137 case ICV_SECOND_OF_COND:
1138 warning (0, "variable %qE of incomplete type %qT will not "
1139 "be accessed in second operand of "
1140 "conditional expression", expr, type);
1141 break;
1142 case ICV_THIRD_OF_COND:
1143 warning (0, "variable %qE of incomplete type %qT will not "
1144 "be accessed in third operand of "
1145 "conditional expression", expr, type);
1146 break;
1147 case ICV_RIGHT_OF_COMMA:
1148 warning (0, "variable %qE of incomplete type %qT will not "
1149 "be accessed in right operand of comma operator",
1150 expr, type);
1151 break;
1152 case ICV_LEFT_OF_COMMA:
1153 warning (0, "variable %qE of incomplete type %qT will not "
1154 "be accessed in left operand of comma operator",
1155 expr, type);
1156 break;
1157 case ICV_STATEMENT:
1158 warning (0, "variable %qE of incomplete type %qT will not "
1159 "be accessed in statement", expr, type);
1160 break;
1161 case ICV_THIRD_IN_FOR:
1162 warning (0, "variable %qE of incomplete type %qT will not "
1163 "be accessed in for increment expression",
1164 expr, type);
1165 break;
1166 default:
1167 gcc_unreachable ();
1168 }
1169
1170 break;
1171 }
1172
1173 case TARGET_EXPR:
1174 /* Don't bother with the temporary object returned from a function if
1175 we don't use it and don't need to destroy it. We'll still
1176 allocate space for it in expand_call or declare_return_variable,
1177 but we don't need to track it through all the tree phases. */
1178 if (TARGET_EXPR_IMPLICIT_P (expr)
1179 && TYPE_HAS_TRIVIAL_DESTRUCTOR (TREE_TYPE (expr)))
1180 {
1181 tree init = TARGET_EXPR_INITIAL (expr);
1182 if (TREE_CODE (init) == AGGR_INIT_EXPR
1183 && !AGGR_INIT_VIA_CTOR_P (init))
1184 {
1185 tree fn = AGGR_INIT_EXPR_FN (init);
1186 expr = build_call_array_loc (input_location,
1187 TREE_TYPE (TREE_TYPE (TREE_TYPE (fn))),
1188 fn,
1189 aggr_init_expr_nargs (init),
1190 AGGR_INIT_EXPR_ARGP (init));
1191 }
1192 }
1193 break;
1194
1195 default:;
1196 }
1197 expr = resolve_nondeduced_context (expr);
1198 {
1199 tree probe = expr;
1200
1201 if (TREE_CODE (probe) == ADDR_EXPR)
1202 probe = TREE_OPERAND (expr, 0);
1203 if (type_unknown_p (probe))
1204 {
1205 /* [over.over] enumerates the places where we can take the address
1206 of an overloaded function, and this is not one of them. */
1207 if (complain & tf_error)
1208 switch (implicit)
1209 {
1210 case ICV_CAST:
1211 error ("conversion to void "
1212 "cannot resolve address of overloaded function");
1213 break;
1214 case ICV_SECOND_OF_COND:
1215 error ("second operand of conditional expression "
1216 "cannot resolve address of overloaded function");
1217 break;
1218 case ICV_THIRD_OF_COND:
1219 error ("third operand of conditional expression "
1220 "cannot resolve address of overloaded function");
1221 break;
1222 case ICV_RIGHT_OF_COMMA:
1223 error ("right operand of comma operator "
1224 "cannot resolve address of overloaded function");
1225 break;
1226 case ICV_LEFT_OF_COMMA:
1227 error ("left operand of comma operator "
1228 "cannot resolve address of overloaded function");
1229 break;
1230 case ICV_STATEMENT:
1231 error ("statement "
1232 "cannot resolve address of overloaded function");
1233 break;
1234 case ICV_THIRD_IN_FOR:
1235 error ("for increment expression "
1236 "cannot resolve address of overloaded function");
1237 break;
1238 }
1239 else
1240 return error_mark_node;
1241 expr = void_zero_node;
1242 }
1243 else if (implicit != ICV_CAST && probe == expr && is_overloaded_fn (probe))
1244 {
1245 /* Only warn when there is no &. */
1246 if (complain & tf_warning)
1247 switch (implicit)
1248 {
1249 case ICV_SECOND_OF_COND:
1250 warning (OPT_Waddress,
1251 "second operand of conditional expression "
1252 "is a reference, not call, to function %qE", expr);
1253 break;
1254 case ICV_THIRD_OF_COND:
1255 warning (OPT_Waddress,
1256 "third operand of conditional expression "
1257 "is a reference, not call, to function %qE", expr);
1258 break;
1259 case ICV_RIGHT_OF_COMMA:
1260 warning (OPT_Waddress,
1261 "right operand of comma operator "
1262 "is a reference, not call, to function %qE", expr);
1263 break;
1264 case ICV_LEFT_OF_COMMA:
1265 warning (OPT_Waddress,
1266 "left operand of comma operator "
1267 "is a reference, not call, to function %qE", expr);
1268 break;
1269 case ICV_STATEMENT:
1270 warning (OPT_Waddress,
1271 "statement is a reference, not call, to function %qE",
1272 expr);
1273 break;
1274 case ICV_THIRD_IN_FOR:
1275 warning (OPT_Waddress,
1276 "for increment expression "
1277 "is a reference, not call, to function %qE", expr);
1278 break;
1279 default:
1280 gcc_unreachable ();
1281 }
1282
1283 if (TREE_CODE (expr) == COMPONENT_REF)
1284 expr = TREE_OPERAND (expr, 0);
1285 }
1286 }
1287
1288 if (expr != error_mark_node && !VOID_TYPE_P (TREE_TYPE (expr)))
1289 {
1290 if (implicit != ICV_CAST
1291 && warn_unused_value
1292 && !TREE_NO_WARNING (expr)
1293 && !processing_template_decl)
1294 {
1295 /* The middle end does not warn about expressions that have
1296 been explicitly cast to void, so we must do so here. */
1297 if (!TREE_SIDE_EFFECTS (expr)) {
1298 if (complain & tf_warning)
1299 switch (implicit)
1300 {
1301 case ICV_SECOND_OF_COND:
1302 warning (OPT_Wunused_value,
1303 "second operand of conditional expression has no effect");
1304 break;
1305 case ICV_THIRD_OF_COND:
1306 warning (OPT_Wunused_value,
1307 "third operand of conditional expression has no effect");
1308 break;
1309 case ICV_RIGHT_OF_COMMA:
1310 warning (OPT_Wunused_value,
1311 "right operand of comma operator has no effect");
1312 break;
1313 case ICV_LEFT_OF_COMMA:
1314 warning (OPT_Wunused_value,
1315 "left operand of comma operator has no effect");
1316 break;
1317 case ICV_STATEMENT:
1318 warning (OPT_Wunused_value,
1319 "statement has no effect");
1320 break;
1321 case ICV_THIRD_IN_FOR:
1322 warning (OPT_Wunused_value,
1323 "for increment expression has no effect");
1324 break;
1325 default:
1326 gcc_unreachable ();
1327 }
1328 }
1329 else
1330 {
1331 tree e;
1332 enum tree_code code;
1333 enum tree_code_class tclass;
1334
1335 e = expr;
1336 /* We might like to warn about (say) "(int) f()", as the
1337 cast has no effect, but the compiler itself will
1338 generate implicit conversions under some
1339 circumstances. (For example a block copy will be
1340 turned into a call to "__builtin_memcpy", with a
1341 conversion of the return value to an appropriate
1342 type.) So, to avoid false positives, we strip
1343 conversions. Do not use STRIP_NOPs because it will
1344 not strip conversions to "void", as that is not a
1345 mode-preserving conversion. */
1346 while (TREE_CODE (e) == NOP_EXPR)
1347 e = TREE_OPERAND (e, 0);
1348
1349 code = TREE_CODE (e);
1350 tclass = TREE_CODE_CLASS (code);
1351 if ((tclass == tcc_comparison
1352 || tclass == tcc_unary
1353 || (tclass == tcc_binary
1354 && !(code == MODIFY_EXPR
1355 || code == INIT_EXPR
1356 || code == PREDECREMENT_EXPR
1357 || code == PREINCREMENT_EXPR
1358 || code == POSTDECREMENT_EXPR
1359 || code == POSTINCREMENT_EXPR)))
1360 && (complain & tf_warning))
1361 warning (OPT_Wunused_value, "value computed is not used");
1362 }
1363 }
1364 expr = build1 (CONVERT_EXPR, void_type_node, expr);
1365 }
1366 if (! TREE_SIDE_EFFECTS (expr))
1367 expr = void_zero_node;
1368 return expr;
1369 }
1370
1371 /* Create an expression whose value is that of EXPR,
1372 converted to type TYPE. The TREE_TYPE of the value
1373 is always TYPE. This function implements all reasonable
1374 conversions; callers should filter out those that are
1375 not permitted by the language being compiled.
1376
1377 Most of this routine is from build_reinterpret_cast.
1378
1379 The back end cannot call cp_convert (what was convert) because
1380 conversions to/from basetypes may involve memory references
1381 (vbases) and adding or subtracting small values (multiple
1382 inheritance), but it calls convert from the constant folding code
1383 on subtrees of already built trees after it has ripped them apart.
1384
1385 Also, if we ever support range variables, we'll probably also have to
1386 do a little bit more work. */
1387
1388 tree
convert(tree type,tree expr)1389 convert (tree type, tree expr)
1390 {
1391 tree intype;
1392
1393 if (type == error_mark_node || expr == error_mark_node)
1394 return error_mark_node;
1395
1396 intype = TREE_TYPE (expr);
1397
1398 if (POINTER_TYPE_P (type) && POINTER_TYPE_P (intype))
1399 return fold_if_not_in_template (build_nop (type, expr));
1400
1401 return ocp_convert (type, expr, CONV_OLD_CONVERT,
1402 LOOKUP_NORMAL|LOOKUP_NO_CONVERSION);
1403 }
1404
1405 /* Like cp_convert, except permit conversions to take place which
1406 are not normally allowed due to access restrictions
1407 (such as conversion from sub-type to private super-type). */
1408
1409 tree
convert_force(tree type,tree expr,int convtype)1410 convert_force (tree type, tree expr, int convtype)
1411 {
1412 tree e = expr;
1413 enum tree_code code = TREE_CODE (type);
1414
1415 if (code == REFERENCE_TYPE)
1416 return (fold_if_not_in_template
1417 (convert_to_reference (type, e, CONV_C_CAST, LOOKUP_COMPLAIN,
1418 NULL_TREE)));
1419
1420 if (code == POINTER_TYPE)
1421 return fold_if_not_in_template (convert_to_pointer_force (type, e));
1422
1423 /* From typeck.c convert_for_assignment */
1424 if (((TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE && TREE_CODE (e) == ADDR_EXPR
1425 && TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE
1426 && TREE_CODE (TREE_TYPE (TREE_TYPE (e))) == METHOD_TYPE)
1427 || integer_zerop (e)
1428 || TYPE_PTRMEMFUNC_P (TREE_TYPE (e)))
1429 && TYPE_PTRMEMFUNC_P (type))
1430 /* compatible pointer to member functions. */
1431 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), e, 1,
1432 /*c_cast_p=*/1, tf_warning_or_error);
1433
1434 return ocp_convert (type, e, CONV_C_CAST|convtype, LOOKUP_NORMAL);
1435 }
1436
1437 /* Convert an aggregate EXPR to type XTYPE. If a conversion
1438 exists, return the attempted conversion. This may
1439 return ERROR_MARK_NODE if the conversion is not
1440 allowed (references private members, etc).
1441 If no conversion exists, NULL_TREE is returned.
1442
1443 FIXME: Ambiguity checking is wrong. Should choose one by the implicit
1444 object parameter, or by the second standard conversion sequence if
1445 that doesn't do it. This will probably wait for an overloading rewrite.
1446 (jason 8/9/95) */
1447
1448 static tree
build_type_conversion(tree xtype,tree expr)1449 build_type_conversion (tree xtype, tree expr)
1450 {
1451 /* C++: check to see if we can convert this aggregate type
1452 into the required type. */
1453 return build_user_type_conversion (xtype, expr, LOOKUP_NORMAL);
1454 }
1455
1456 /* Convert the given EXPR to one of a group of types suitable for use in an
1457 expression. DESIRES is a combination of various WANT_* flags (q.v.)
1458 which indicates which types are suitable. If COMPLAIN is true, complain
1459 about ambiguity; otherwise, the caller will deal with it. */
1460
1461 tree
build_expr_type_conversion(int desires,tree expr,bool complain)1462 build_expr_type_conversion (int desires, tree expr, bool complain)
1463 {
1464 tree basetype = TREE_TYPE (expr);
1465 tree conv = NULL_TREE;
1466 tree winner = NULL_TREE;
1467
1468 if (expr == null_node
1469 && (desires & WANT_INT)
1470 && !(desires & WANT_NULL))
1471 warning_at (input_location, OPT_Wconversion_null,
1472 "converting NULL to non-pointer type");
1473
1474 basetype = TREE_TYPE (expr);
1475
1476 if (basetype == error_mark_node)
1477 return error_mark_node;
1478
1479 if (! MAYBE_CLASS_TYPE_P (basetype))
1480 switch (TREE_CODE (basetype))
1481 {
1482 case INTEGER_TYPE:
1483 if ((desires & WANT_NULL) && null_ptr_cst_p (expr))
1484 return expr;
1485 /* else fall through... */
1486
1487 case BOOLEAN_TYPE:
1488 return (desires & WANT_INT) ? expr : NULL_TREE;
1489 case ENUMERAL_TYPE:
1490 return (desires & WANT_ENUM) ? expr : NULL_TREE;
1491 case REAL_TYPE:
1492 return (desires & WANT_FLOAT) ? expr : NULL_TREE;
1493 case POINTER_TYPE:
1494 return (desires & WANT_POINTER) ? expr : NULL_TREE;
1495
1496 case FUNCTION_TYPE:
1497 case ARRAY_TYPE:
1498 return (desires & WANT_POINTER) ? decay_conversion (expr)
1499 : NULL_TREE;
1500
1501 case COMPLEX_TYPE:
1502 case VECTOR_TYPE:
1503 if ((desires & WANT_VECTOR_OR_COMPLEX) == 0)
1504 return NULL_TREE;
1505 switch (TREE_CODE (TREE_TYPE (basetype)))
1506 {
1507 case INTEGER_TYPE:
1508 case BOOLEAN_TYPE:
1509 return (desires & WANT_INT) ? expr : NULL_TREE;
1510 case ENUMERAL_TYPE:
1511 return (desires & WANT_ENUM) ? expr : NULL_TREE;
1512 case REAL_TYPE:
1513 return (desires & WANT_FLOAT) ? expr : NULL_TREE;
1514 default:
1515 return NULL_TREE;
1516 }
1517
1518 default:
1519 return NULL_TREE;
1520 }
1521
1522 /* The code for conversions from class type is currently only used for
1523 delete expressions. Other expressions are handled by build_new_op. */
1524 if (!complete_type_or_maybe_complain (basetype, expr, complain))
1525 return error_mark_node;
1526 if (!TYPE_HAS_CONVERSION (basetype))
1527 return NULL_TREE;
1528
1529 for (conv = lookup_conversions (basetype); conv; conv = TREE_CHAIN (conv))
1530 {
1531 int win = 0;
1532 tree candidate;
1533 tree cand = TREE_VALUE (conv);
1534 cand = OVL_CURRENT (cand);
1535
1536 if (winner && winner == cand)
1537 continue;
1538
1539 if (DECL_NONCONVERTING_P (cand))
1540 continue;
1541
1542 candidate = non_reference (TREE_TYPE (TREE_TYPE (cand)));
1543
1544 switch (TREE_CODE (candidate))
1545 {
1546 case BOOLEAN_TYPE:
1547 case INTEGER_TYPE:
1548 win = (desires & WANT_INT); break;
1549 case ENUMERAL_TYPE:
1550 win = (desires & WANT_ENUM); break;
1551 case REAL_TYPE:
1552 win = (desires & WANT_FLOAT); break;
1553 case POINTER_TYPE:
1554 win = (desires & WANT_POINTER); break;
1555
1556 case COMPLEX_TYPE:
1557 case VECTOR_TYPE:
1558 if ((desires & WANT_VECTOR_OR_COMPLEX) == 0)
1559 break;
1560 switch (TREE_CODE (TREE_TYPE (candidate)))
1561 {
1562 case BOOLEAN_TYPE:
1563 case INTEGER_TYPE:
1564 win = (desires & WANT_INT); break;
1565 case ENUMERAL_TYPE:
1566 win = (desires & WANT_ENUM); break;
1567 case REAL_TYPE:
1568 win = (desires & WANT_FLOAT); break;
1569 default:
1570 break;
1571 }
1572 break;
1573
1574 default:
1575 /* A wildcard could be instantiated to match any desired
1576 type, but we can't deduce the template argument. */
1577 if (WILDCARD_TYPE_P (candidate))
1578 win = true;
1579 break;
1580 }
1581
1582 if (win)
1583 {
1584 if (TREE_CODE (cand) == TEMPLATE_DECL)
1585 {
1586 if (complain)
1587 error ("default type conversion can't deduce template"
1588 " argument for %qD", cand);
1589 return error_mark_node;
1590 }
1591
1592 if (winner)
1593 {
1594 if (complain)
1595 {
1596 error ("ambiguous default type conversion from %qT",
1597 basetype);
1598 error (" candidate conversions include %qD and %qD",
1599 winner, cand);
1600 }
1601 return error_mark_node;
1602 }
1603 else
1604 winner = cand;
1605 }
1606 }
1607
1608 if (winner)
1609 {
1610 tree type = non_reference (TREE_TYPE (TREE_TYPE (winner)));
1611 return build_user_type_conversion (type, expr, LOOKUP_NORMAL);
1612 }
1613
1614 return NULL_TREE;
1615 }
1616
1617 /* Implements integral promotion (4.1) and float->double promotion. */
1618
1619 tree
type_promotes_to(tree type)1620 type_promotes_to (tree type)
1621 {
1622 tree promoted_type;
1623
1624 if (type == error_mark_node)
1625 return error_mark_node;
1626
1627 type = TYPE_MAIN_VARIANT (type);
1628
1629 /* Check for promotions of target-defined types first. */
1630 promoted_type = targetm.promoted_type (type);
1631 if (promoted_type)
1632 return promoted_type;
1633
1634 /* bool always promotes to int (not unsigned), even if it's the same
1635 size. */
1636 if (TREE_CODE (type) == BOOLEAN_TYPE)
1637 type = integer_type_node;
1638
1639 /* Scoped enums don't promote, but pretend they do for backward ABI bug
1640 compatibility wrt varargs. */
1641 else if (SCOPED_ENUM_P (type) && abi_version_at_least (6))
1642 ;
1643
1644 /* Normally convert enums to int, but convert wide enums to something
1645 wider. */
1646 else if (TREE_CODE (type) == ENUMERAL_TYPE
1647 || type == char16_type_node
1648 || type == char32_type_node
1649 || type == wchar_type_node)
1650 {
1651 int precision = MAX (TYPE_PRECISION (type),
1652 TYPE_PRECISION (integer_type_node));
1653 tree totype = c_common_type_for_size (precision, 0);
1654 if (SCOPED_ENUM_P (type))
1655 warning (OPT_Wabi, "scoped enum %qT will not promote to an integral "
1656 "type in a future version of GCC", type);
1657 if (TREE_CODE (type) == ENUMERAL_TYPE)
1658 type = ENUM_UNDERLYING_TYPE (type);
1659 if (TYPE_UNSIGNED (type)
1660 && ! int_fits_type_p (TYPE_MAX_VALUE (type), totype))
1661 type = c_common_type_for_size (precision, 1);
1662 else
1663 type = totype;
1664 }
1665 else if (c_promoting_integer_type_p (type))
1666 {
1667 /* Retain unsignedness if really not getting bigger. */
1668 if (TYPE_UNSIGNED (type)
1669 && TYPE_PRECISION (type) == TYPE_PRECISION (integer_type_node))
1670 type = unsigned_type_node;
1671 else
1672 type = integer_type_node;
1673 }
1674 else if (type == float_type_node)
1675 type = double_type_node;
1676
1677 return type;
1678 }
1679
1680 /* The routines below this point are carefully written to conform to
1681 the standard. They use the same terminology, and follow the rules
1682 closely. Although they are used only in pt.c at the moment, they
1683 should presumably be used everywhere in the future. */
1684
1685 /* Attempt to perform qualification conversions on EXPR to convert it
1686 to TYPE. Return the resulting expression, or error_mark_node if
1687 the conversion was impossible. */
1688
1689 tree
perform_qualification_conversions(tree type,tree expr)1690 perform_qualification_conversions (tree type, tree expr)
1691 {
1692 tree expr_type;
1693
1694 expr_type = TREE_TYPE (expr);
1695
1696 if (same_type_p (type, expr_type))
1697 return expr;
1698 else if (TYPE_PTR_P (type) && TYPE_PTR_P (expr_type)
1699 && comp_ptr_ttypes (TREE_TYPE (type), TREE_TYPE (expr_type)))
1700 return build_nop (type, expr);
1701 else if (TYPE_PTR_TO_MEMBER_P (type)
1702 && TYPE_PTR_TO_MEMBER_P (expr_type)
1703 && same_type_p (TYPE_PTRMEM_CLASS_TYPE (type),
1704 TYPE_PTRMEM_CLASS_TYPE (expr_type))
1705 && comp_ptr_ttypes (TYPE_PTRMEM_POINTED_TO_TYPE (type),
1706 TYPE_PTRMEM_POINTED_TO_TYPE (expr_type)))
1707 return build_nop (type, expr);
1708 else
1709 return error_mark_node;
1710 }
1711