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comparison gcc/cp/except.c @ 111:04ced10e8804

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gcc 7
author kono
date Fri, 27 Oct 2017 22:46:09 +0900
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children 84e7813d76e9
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68:561a7518be6b 111:04ced10e8804
1 /* Handle exceptional things in C++.
2 Copyright (C) 1989-2017 Free Software Foundation, Inc.
3 Contributed by Michael Tiemann <tiemann@cygnus.com>
4 Rewritten by Mike Stump <mrs@cygnus.com>, based upon an
5 initial re-implementation courtesy Tad Hunt.
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 #include "config.h"
25 #include "system.h"
26 #include "coretypes.h"
27 #include "cp-tree.h"
28 #include "stringpool.h"
29 #include "trans-mem.h"
30 #include "attribs.h"
31 #include "tree-iterator.h"
32
33 static void push_eh_cleanup (tree);
34 static tree prepare_eh_type (tree);
35 static tree do_begin_catch (void);
36 static int dtor_nothrow (tree);
37 static tree do_end_catch (tree);
38 static void initialize_handler_parm (tree, tree);
39 static tree do_allocate_exception (tree);
40 static tree wrap_cleanups_r (tree *, int *, void *);
41 static int complete_ptr_ref_or_void_ptr_p (tree, tree);
42 static bool is_admissible_throw_operand_or_catch_parameter (tree, bool);
43 static int can_convert_eh (tree, tree);
44
45 /* Sets up all the global eh stuff that needs to be initialized at the
46 start of compilation. */
47
48 void
49 init_exception_processing (void)
50 {
51 tree tmp;
52
53 /* void std::terminate (); */
54 push_namespace (std_identifier);
55 tmp = build_function_type_list (void_type_node, NULL_TREE);
56 terminate_fn = build_cp_library_fn_ptr ("terminate", tmp,
57 ECF_NOTHROW | ECF_NORETURN
58 | ECF_COLD);
59 gcc_checking_assert (TREE_THIS_VOLATILE (terminate_fn)
60 && TREE_NOTHROW (terminate_fn));
61 pop_namespace ();
62
63 /* void __cxa_call_unexpected(void *); */
64 tmp = build_function_type_list (void_type_node, ptr_type_node, NULL_TREE);
65 call_unexpected_fn
66 = push_throw_library_fn (get_identifier ("__cxa_call_unexpected"), tmp);
67 }
68
69 /* Returns an expression to be executed if an unhandled exception is
70 propagated out of a cleanup region. */
71
72 tree
73 cp_protect_cleanup_actions (void)
74 {
75 /* [except.terminate]
76
77 When the destruction of an object during stack unwinding exits
78 using an exception ... void terminate(); is called. */
79 return terminate_fn;
80 }
81
82 static tree
83 prepare_eh_type (tree type)
84 {
85 if (type == NULL_TREE)
86 return type;
87 if (type == error_mark_node)
88 return error_mark_node;
89
90 /* peel back references, so they match. */
91 type = non_reference (type);
92
93 /* Peel off cv qualifiers. */
94 type = TYPE_MAIN_VARIANT (type);
95
96 /* Functions and arrays decay to pointers. */
97 type = type_decays_to (type);
98
99 return type;
100 }
101
102 /* Return the type info for TYPE as used by EH machinery. */
103 tree
104 eh_type_info (tree type)
105 {
106 if (type == NULL_TREE || type == error_mark_node)
107 return type;
108
109 return get_tinfo_decl (type);
110 }
111
112 /* Build the address of a typeinfo decl for use in the runtime
113 matching field of the exception model. */
114
115 tree
116 build_eh_type_type (tree type)
117 {
118 tree exp = eh_type_info (type);
119
120 if (!exp)
121 return NULL;
122
123 mark_used (exp);
124
125 return convert (ptr_type_node, build_address (exp));
126 }
127
128 tree
129 build_exc_ptr (void)
130 {
131 return build_call_n (builtin_decl_explicit (BUILT_IN_EH_POINTER),
132 1, integer_zero_node);
133 }
134
135 /* Find or declare a function NAME, returning RTYPE, taking a single
136 parameter PTYPE, with an empty exception specification. ECF are the
137 library fn flags. If TM_ECF is non-zero, also find or create a
138 transaction variant and record it as a replacement, when flag_tm is
139 in effect.
140
141 Note that the C++ ABI document does not have a throw-specifier on
142 the routines declared below via this function. The declarations
143 are consistent with the actual implementations in libsupc++. */
144
145 static tree
146 declare_library_fn (const char *name, tree rtype, tree ptype,
147 int ecf, int tm_ecf)
148 {
149 tree ident = get_identifier (name);
150 tree res = get_global_binding (ident);
151 if (!res)
152 {
153 tree type = build_function_type_list (rtype, ptype, NULL_TREE);
154 tree except = ecf & ECF_NOTHROW ? empty_except_spec : NULL_TREE;
155 res = push_library_fn (ident, type, except, ecf);
156 if (tm_ecf && flag_tm)
157 {
158 char *tm_name = concat ("_ITM_", name + 2, NULL_TREE);
159 tree tm_ident = get_identifier (tm_name);
160 free (tm_name);
161 tree tm_fn = get_global_binding (tm_ident);
162 if (!tm_fn)
163 tm_fn = push_library_fn (tm_ident, type, except, ecf | tm_ecf);
164 record_tm_replacement (res, tm_fn);
165 }
166 }
167 return res;
168 }
169
170 /* Build up a call to __cxa_get_exception_ptr so that we can build a
171 copy constructor for the thrown object. */
172
173 static tree
174 do_get_exception_ptr (void)
175 {
176 if (!get_exception_ptr_fn)
177 /* Declare void* __cxa_get_exception_ptr (void *) throw(). */
178 get_exception_ptr_fn
179 = declare_library_fn ("__cxa_get_exception_ptr",
180 ptr_type_node, ptr_type_node,
181 ECF_NOTHROW | ECF_PURE | ECF_LEAF | ECF_TM_PURE,
182 0);
183
184 return cp_build_function_call_nary (get_exception_ptr_fn,
185 tf_warning_or_error,
186 build_exc_ptr (), NULL_TREE);
187 }
188
189 /* Build up a call to __cxa_begin_catch, to tell the runtime that the
190 exception has been handled. */
191
192 static tree
193 do_begin_catch (void)
194 {
195 if (!begin_catch_fn)
196 /* Declare void* __cxa_begin_catch (void *) throw(). */
197 begin_catch_fn
198 = declare_library_fn ("__cxa_begin_catch",
199 ptr_type_node, ptr_type_node, ECF_NOTHROW,
200 ECF_TM_PURE);
201
202 return cp_build_function_call_nary (begin_catch_fn, tf_warning_or_error,
203 build_exc_ptr (), NULL_TREE);
204 }
205
206 /* Returns nonzero if cleaning up an exception of type TYPE (which can be
207 NULL_TREE for a ... handler) will not throw an exception. */
208
209 static int
210 dtor_nothrow (tree type)
211 {
212 if (type == NULL_TREE || type == error_mark_node)
213 return 0;
214
215 if (TYPE_HAS_TRIVIAL_DESTRUCTOR (type))
216 return 1;
217
218 if (CLASSTYPE_LAZY_DESTRUCTOR (type))
219 lazily_declare_fn (sfk_destructor, type);
220
221 return TREE_NOTHROW (CLASSTYPE_DESTRUCTOR (type));
222 }
223
224 /* Build up a call to __cxa_end_catch, to destroy the exception object
225 for the current catch block if no others are currently using it. */
226
227 static tree
228 do_end_catch (tree type)
229 {
230 if (!end_catch_fn)
231 /* Declare void __cxa_end_catch ().
232 This can throw if the destructor for the exception throws. */
233 end_catch_fn
234 = declare_library_fn ("__cxa_end_catch", void_type_node,
235 NULL_TREE, 0, ECF_TM_PURE);
236
237 tree cleanup = cp_build_function_call_vec (end_catch_fn,
238 NULL, tf_warning_or_error);
239 TREE_NOTHROW (cleanup) = dtor_nothrow (type);
240
241 return cleanup;
242 }
243
244 /* This routine creates the cleanup for the current exception. */
245
246 static void
247 push_eh_cleanup (tree type)
248 {
249 finish_decl_cleanup (NULL_TREE, do_end_catch (type));
250 }
251
252 /* Wrap EXPR in a MUST_NOT_THROW_EXPR expressing that EXPR must
253 not throw any exceptions if COND is true. A condition of
254 NULL_TREE is treated as 'true'. */
255
256 tree
257 build_must_not_throw_expr (tree body, tree cond)
258 {
259 tree type = body ? TREE_TYPE (body) : void_type_node;
260
261 if (!flag_exceptions)
262 return body;
263
264 if (!cond)
265 /* OK, unconditional. */;
266 else
267 {
268 tree conv = NULL_TREE;
269 if (!type_dependent_expression_p (cond))
270 conv = perform_implicit_conversion_flags (boolean_type_node, cond,
271 tf_warning_or_error,
272 LOOKUP_NORMAL);
273 if (tree inst = instantiate_non_dependent_or_null (conv))
274 cond = cxx_constant_value (inst);
275 else
276 require_constant_expression (cond);
277 if (integer_zerop (cond))
278 return body;
279 else if (integer_onep (cond))
280 cond = NULL_TREE;
281 }
282
283 return build2 (MUST_NOT_THROW_EXPR, type, body, cond);
284 }
285
286
287 /* Initialize the catch parameter DECL. */
288
289 static void
290 initialize_handler_parm (tree decl, tree exp)
291 {
292 tree init;
293 tree init_type;
294
295 /* Make sure we mark the catch param as used, otherwise we'll get a
296 warning about an unused ((anonymous)). */
297 TREE_USED (decl) = 1;
298 DECL_READ_P (decl) = 1;
299
300 /* Figure out the type that the initializer is. Pointers are returned
301 adjusted by value from __cxa_begin_catch. Others are returned by
302 reference. */
303 init_type = TREE_TYPE (decl);
304 if (!POINTER_TYPE_P (init_type))
305 init_type = build_reference_type (init_type);
306
307 /* Since pointers are passed by value, initialize a reference to
308 pointer catch parm with the address of the temporary. */
309 if (TREE_CODE (init_type) == REFERENCE_TYPE
310 && TYPE_PTR_P (TREE_TYPE (init_type)))
311 exp = cp_build_addr_expr (exp, tf_warning_or_error);
312
313 exp = ocp_convert (init_type, exp, CONV_IMPLICIT|CONV_FORCE_TEMP, 0,
314 tf_warning_or_error);
315
316 init = convert_from_reference (exp);
317
318 /* If the constructor for the catch parm exits via an exception, we
319 must call terminate. See eh23.C. */
320 if (TYPE_NEEDS_CONSTRUCTING (TREE_TYPE (decl)))
321 {
322 /* Generate the copy constructor call directly so we can wrap it.
323 See also expand_default_init. */
324 init = ocp_convert (TREE_TYPE (decl), init,
325 CONV_IMPLICIT|CONV_FORCE_TEMP, 0,
326 tf_warning_or_error);
327 /* Force cleanups now to avoid nesting problems with the
328 MUST_NOT_THROW_EXPR. */
329 init = fold_build_cleanup_point_expr (TREE_TYPE (init), init);
330 init = build_must_not_throw_expr (init, NULL_TREE);
331 }
332
333 decl = pushdecl (decl);
334
335 start_decl_1 (decl, true);
336 cp_finish_decl (decl, init, /*init_const_expr_p=*/false, NULL_TREE,
337 LOOKUP_ONLYCONVERTING|DIRECT_BIND);
338 }
339
340
341 /* Routine to see if exception handling is turned on.
342 DO_WARN is nonzero if we want to inform the user that exception
343 handling is turned off.
344
345 This is used to ensure that -fexceptions has been specified if the
346 compiler tries to use any exception-specific functions. */
347
348 static inline int
349 doing_eh (void)
350 {
351 if (! flag_exceptions)
352 {
353 static int warned = 0;
354 if (! warned)
355 {
356 error ("exception handling disabled, use -fexceptions to enable");
357 warned = 1;
358 }
359 return 0;
360 }
361 return 1;
362 }
363
364 /* Call this to start a catch block. DECL is the catch parameter. */
365
366 tree
367 expand_start_catch_block (tree decl)
368 {
369 tree exp;
370 tree type, init;
371
372 if (! doing_eh ())
373 return NULL_TREE;
374
375 if (decl)
376 {
377 if (!is_admissible_throw_operand_or_catch_parameter (decl, false))
378 decl = error_mark_node;
379
380 type = prepare_eh_type (TREE_TYPE (decl));
381 mark_used (eh_type_info (type));
382 }
383 else
384 type = NULL_TREE;
385
386 /* Call __cxa_end_catch at the end of processing the exception. */
387 push_eh_cleanup (type);
388
389 init = do_begin_catch ();
390
391 /* If there's no decl at all, then all we need to do is make sure
392 to tell the runtime that we've begun handling the exception. */
393 if (decl == NULL || decl == error_mark_node || init == error_mark_node)
394 finish_expr_stmt (init);
395
396 /* If the C++ object needs constructing, we need to do that before
397 calling __cxa_begin_catch, so that std::uncaught_exception gets
398 the right value during the copy constructor. */
399 else if (flag_use_cxa_get_exception_ptr
400 && TYPE_NEEDS_CONSTRUCTING (TREE_TYPE (decl)))
401 {
402 exp = do_get_exception_ptr ();
403 initialize_handler_parm (decl, exp);
404 finish_expr_stmt (init);
405 }
406
407 /* Otherwise the type uses a bitwise copy, and we don't have to worry
408 about the value of std::uncaught_exception and therefore can do the
409 copy with the return value of __cxa_end_catch instead. */
410 else
411 {
412 tree init_type = type;
413
414 /* Pointers are passed by values, everything else by reference. */
415 if (!TYPE_PTR_P (type))
416 init_type = build_pointer_type (type);
417 if (init_type != TREE_TYPE (init))
418 init = build1 (NOP_EXPR, init_type, init);
419 exp = create_temporary_var (init_type);
420 cp_finish_decl (exp, init, /*init_const_expr=*/false,
421 NULL_TREE, LOOKUP_ONLYCONVERTING);
422 DECL_REGISTER (exp) = 1;
423 initialize_handler_parm (decl, exp);
424 }
425
426 return type;
427 }
428
429
430 /* Call this to end a catch block. Its responsible for emitting the
431 code to handle jumping back to the correct place, and for emitting
432 the label to jump to if this catch block didn't match. */
433
434 void
435 expand_end_catch_block (void)
436 {
437 if (! doing_eh ())
438 return;
439
440 /* The exception being handled is rethrown if control reaches the end of
441 a handler of the function-try-block of a constructor or destructor. */
442 if (in_function_try_handler
443 && (DECL_CONSTRUCTOR_P (current_function_decl)
444 || DECL_DESTRUCTOR_P (current_function_decl)))
445 {
446 tree rethrow = build_throw (NULL_TREE);
447 TREE_NO_WARNING (rethrow) = true;
448 finish_expr_stmt (rethrow);
449 }
450 }
451
452 tree
453 begin_eh_spec_block (void)
454 {
455 tree r;
456 location_t spec_location = DECL_SOURCE_LOCATION (current_function_decl);
457
458 /* A noexcept specification (or throw() with -fnothrow-opt) is a
459 MUST_NOT_THROW_EXPR. */
460 if (TYPE_NOEXCEPT_P (TREE_TYPE (current_function_decl)))
461 {
462 r = build_stmt (spec_location, MUST_NOT_THROW_EXPR,
463 NULL_TREE, NULL_TREE);
464 TREE_SIDE_EFFECTS (r) = 1;
465 }
466 else
467 r = build_stmt (spec_location, EH_SPEC_BLOCK, NULL_TREE, NULL_TREE);
468 add_stmt (r);
469 TREE_OPERAND (r, 0) = push_stmt_list ();
470 return r;
471 }
472
473 void
474 finish_eh_spec_block (tree raw_raises, tree eh_spec_block)
475 {
476 tree raises;
477
478 TREE_OPERAND (eh_spec_block, 0)
479 = pop_stmt_list (TREE_OPERAND (eh_spec_block, 0));
480
481 if (TREE_CODE (eh_spec_block) == MUST_NOT_THROW_EXPR)
482 return;
483
484 /* Strip cv quals, etc, from the specification types. */
485 for (raises = NULL_TREE;
486 raw_raises && TREE_VALUE (raw_raises);
487 raw_raises = TREE_CHAIN (raw_raises))
488 {
489 tree type = prepare_eh_type (TREE_VALUE (raw_raises));
490 tree tinfo = eh_type_info (type);
491
492 mark_used (tinfo);
493 raises = tree_cons (NULL_TREE, type, raises);
494 }
495
496 EH_SPEC_RAISES (eh_spec_block) = raises;
497 }
498
499 /* Return a pointer to a buffer for an exception object of type TYPE. */
500
501 static tree
502 do_allocate_exception (tree type)
503 {
504 if (!allocate_exception_fn)
505 /* Declare void *__cxa_allocate_exception(size_t) throw(). */
506 allocate_exception_fn
507 = declare_library_fn ("__cxa_allocate_exception",
508 ptr_type_node, size_type_node,
509 ECF_NOTHROW | ECF_MALLOC, ECF_TM_PURE);
510
511 return cp_build_function_call_nary (allocate_exception_fn,
512 tf_warning_or_error,
513 size_in_bytes (type), NULL_TREE);
514 }
515
516 /* Call __cxa_free_exception from a cleanup. This is never invoked
517 directly, but see the comment for stabilize_throw_expr. */
518
519 static tree
520 do_free_exception (tree ptr)
521 {
522 if (!free_exception_fn)
523 /* Declare void __cxa_free_exception (void *) throw(). */
524 free_exception_fn
525 = declare_library_fn ("__cxa_free_exception",
526 void_type_node, ptr_type_node,
527 ECF_NOTHROW | ECF_LEAF, ECF_TM_PURE);
528
529 return cp_build_function_call_nary (free_exception_fn,
530 tf_warning_or_error, ptr, NULL_TREE);
531 }
532
533 /* Wrap all cleanups for TARGET_EXPRs in MUST_NOT_THROW_EXPR.
534 Called from build_throw via walk_tree_without_duplicates. */
535
536 static tree
537 wrap_cleanups_r (tree *tp, int *walk_subtrees, void * /*data*/)
538 {
539 tree exp = *tp;
540 tree cleanup;
541
542 /* Don't walk into types. */
543 if (TYPE_P (exp))
544 {
545 *walk_subtrees = 0;
546 return NULL_TREE;
547 }
548 if (TREE_CODE (exp) != TARGET_EXPR)
549 return NULL_TREE;
550
551 cleanup = TARGET_EXPR_CLEANUP (exp);
552 if (cleanup)
553 {
554 cleanup = build2 (MUST_NOT_THROW_EXPR, void_type_node, cleanup,
555 NULL_TREE);
556 TARGET_EXPR_CLEANUP (exp) = cleanup;
557 }
558
559 /* Keep iterating. */
560 return NULL_TREE;
561 }
562
563 /* Build a throw expression. */
564
565 tree
566 build_throw (tree exp)
567 {
568 if (exp == error_mark_node)
569 return exp;
570
571 if (processing_template_decl)
572 {
573 if (cfun)
574 current_function_returns_abnormally = 1;
575 exp = build_min (THROW_EXPR, void_type_node, exp);
576 SET_EXPR_LOCATION (exp, input_location);
577 return exp;
578 }
579
580 if (exp == null_node)
581 warning (0, "throwing NULL, which has integral, not pointer type");
582
583 if (exp != NULL_TREE)
584 {
585 if (!is_admissible_throw_operand_or_catch_parameter (exp, true))
586 return error_mark_node;
587 }
588
589 if (! doing_eh ())
590 return error_mark_node;
591
592 if (exp)
593 {
594 tree throw_type;
595 tree temp_type;
596 tree cleanup;
597 tree object, ptr;
598 tree tmp;
599 tree allocate_expr;
600
601 /* The CLEANUP_TYPE is the internal type of a destructor. */
602 if (!cleanup_type)
603 {
604 tmp = build_function_type_list (void_type_node,
605 ptr_type_node, NULL_TREE);
606 cleanup_type = build_pointer_type (tmp);
607 }
608
609 if (!throw_fn)
610 {
611 tree name = get_identifier ("__cxa_throw");
612 throw_fn = get_global_binding (name);
613 if (!throw_fn)
614 {
615 /* Declare void __cxa_throw (void*, void*, void (*)(void*)). */
616 /* ??? Second argument is supposed to be "std::type_info*". */
617 tmp = build_function_type_list (void_type_node,
618 ptr_type_node, ptr_type_node,
619 cleanup_type, NULL_TREE);
620 throw_fn = push_throw_library_fn (name, tmp);
621
622 if (flag_tm)
623 {
624 tree itm_name = get_identifier ("_ITM_cxa_throw");
625 tree itm_fn = get_global_binding (itm_name);
626 if (!itm_fn)
627 itm_fn = push_throw_library_fn (itm_name, tmp);
628 apply_tm_attr (itm_fn, get_identifier ("transaction_pure"));
629 record_tm_replacement (throw_fn, itm_fn);
630 }
631 }
632 }
633
634 /* [except.throw]
635
636 A throw-expression initializes a temporary object, the type
637 of which is determined by removing any top-level
638 cv-qualifiers from the static type of the operand of throw
639 and adjusting the type from "array of T" or "function return
640 T" to "pointer to T" or "pointer to function returning T"
641 respectively. */
642 temp_type = is_bitfield_expr_with_lowered_type (exp);
643 if (!temp_type)
644 temp_type = cv_unqualified (type_decays_to (TREE_TYPE (exp)));
645
646 /* OK, this is kind of wacky. The standard says that we call
647 terminate when the exception handling mechanism, after
648 completing evaluation of the expression to be thrown but
649 before the exception is caught (_except.throw_), calls a
650 user function that exits via an uncaught exception.
651
652 So we have to protect the actual initialization of the
653 exception object with terminate(), but evaluate the
654 expression first. Since there could be temps in the
655 expression, we need to handle that, too. We also expand
656 the call to __cxa_allocate_exception first (which doesn't
657 matter, since it can't throw). */
658
659 /* Allocate the space for the exception. */
660 allocate_expr = do_allocate_exception (temp_type);
661 allocate_expr = get_target_expr (allocate_expr);
662 ptr = TARGET_EXPR_SLOT (allocate_expr);
663 TARGET_EXPR_CLEANUP (allocate_expr) = do_free_exception (ptr);
664 CLEANUP_EH_ONLY (allocate_expr) = 1;
665
666 object = build_nop (build_pointer_type (temp_type), ptr);
667 object = cp_build_indirect_ref (object, RO_NULL, tf_warning_or_error);
668
669 /* And initialize the exception object. */
670 if (CLASS_TYPE_P (temp_type))
671 {
672 int flags = LOOKUP_NORMAL | LOOKUP_ONLYCONVERTING;
673 vec<tree, va_gc> *exp_vec;
674 bool converted = false;
675
676 /* Under C++0x [12.8/16 class.copy], a thrown lvalue is sometimes
677 treated as an rvalue for the purposes of overload resolution
678 to favor move constructors over copy constructors. */
679 if (/* Must be a local, automatic variable. */
680 VAR_P (exp)
681 && DECL_CONTEXT (exp) == current_function_decl
682 && ! TREE_STATIC (exp)
683 /* The variable must not have the `volatile' qualifier. */
684 && !(cp_type_quals (TREE_TYPE (exp)) & TYPE_QUAL_VOLATILE))
685 {
686 tree moved = move (exp);
687 exp_vec = make_tree_vector_single (moved);
688 moved = (build_special_member_call
689 (object, complete_ctor_identifier, &exp_vec,
690 TREE_TYPE (object), flags|LOOKUP_PREFER_RVALUE,
691 tf_none));
692 release_tree_vector (exp_vec);
693 if (moved != error_mark_node)
694 {
695 exp = moved;
696 converted = true;
697 }
698 }
699
700 /* Call the copy constructor. */
701 if (!converted)
702 {
703 exp_vec = make_tree_vector_single (exp);
704 exp = (build_special_member_call
705 (object, complete_ctor_identifier, &exp_vec,
706 TREE_TYPE (object), flags, tf_warning_or_error));
707 release_tree_vector (exp_vec);
708 }
709
710 if (exp == error_mark_node)
711 {
712 error (" in thrown expression");
713 return error_mark_node;
714 }
715 }
716 else
717 {
718 tmp = decay_conversion (exp, tf_warning_or_error);
719 if (tmp == error_mark_node)
720 return error_mark_node;
721 exp = build2 (INIT_EXPR, temp_type, object, tmp);
722 }
723
724 /* Mark any cleanups from the initialization as MUST_NOT_THROW, since
725 they are run after the exception object is initialized. */
726 cp_walk_tree_without_duplicates (&exp, wrap_cleanups_r, 0);
727
728 /* Prepend the allocation. */
729 exp = build2 (COMPOUND_EXPR, TREE_TYPE (exp), allocate_expr, exp);
730
731 /* Force all the cleanups to be evaluated here so that we don't have
732 to do them during unwinding. */
733 exp = build1 (CLEANUP_POINT_EXPR, void_type_node, exp);
734
735 throw_type = build_eh_type_type (prepare_eh_type (TREE_TYPE (object)));
736
737 cleanup = NULL_TREE;
738 if (type_build_dtor_call (TREE_TYPE (object)))
739 {
740 tree dtor_fn = lookup_fnfields (TYPE_BINFO (TREE_TYPE (object)),
741 complete_dtor_identifier, 0);
742 dtor_fn = BASELINK_FUNCTIONS (dtor_fn);
743 mark_used (dtor_fn);
744 if (TYPE_HAS_NONTRIVIAL_DESTRUCTOR (TREE_TYPE (object)))
745 {
746 cxx_mark_addressable (dtor_fn);
747 /* Pretend it's a normal function. */
748 cleanup = build1 (ADDR_EXPR, cleanup_type, dtor_fn);
749 }
750 }
751 if (cleanup == NULL_TREE)
752 cleanup = build_int_cst (cleanup_type, 0);
753
754 /* ??? Indicate that this function call throws throw_type. */
755 tmp = cp_build_function_call_nary (throw_fn, tf_warning_or_error,
756 ptr, throw_type, cleanup, NULL_TREE);
757
758 /* Tack on the initialization stuff. */
759 exp = build2 (COMPOUND_EXPR, TREE_TYPE (tmp), exp, tmp);
760 }
761 else
762 {
763 /* Rethrow current exception. */
764 if (!rethrow_fn)
765 {
766 tree name = get_identifier ("__cxa_rethrow");
767 rethrow_fn = get_global_binding (name);
768 if (!rethrow_fn)
769 /* Declare void __cxa_rethrow (void). */
770 rethrow_fn = push_throw_library_fn
771 (name, build_function_type_list (void_type_node, NULL_TREE));
772
773 if (flag_tm)
774 apply_tm_attr (rethrow_fn, get_identifier ("transaction_pure"));
775 }
776
777 /* ??? Indicate that this function call allows exceptions of the type
778 of the enclosing catch block (if known). */
779 exp = cp_build_function_call_vec (rethrow_fn, NULL, tf_warning_or_error);
780 }
781
782 exp = build1 (THROW_EXPR, void_type_node, exp);
783 SET_EXPR_LOCATION (exp, input_location);
784
785 return exp;
786 }
787
788 /* Make sure TYPE is complete, pointer to complete, reference to
789 complete, or pointer to cv void. Issue diagnostic on failure.
790 Return the zero on failure and nonzero on success. FROM can be
791 the expr or decl from whence TYPE came, if available. */
792
793 static int
794 complete_ptr_ref_or_void_ptr_p (tree type, tree from)
795 {
796 int is_ptr;
797
798 /* Check complete. */
799 type = complete_type_or_else (type, from);
800 if (!type)
801 return 0;
802
803 /* Or a pointer or ref to one, or cv void *. */
804 is_ptr = TYPE_PTR_P (type);
805 if (is_ptr || TREE_CODE (type) == REFERENCE_TYPE)
806 {
807 tree core = TREE_TYPE (type);
808
809 if (is_ptr && VOID_TYPE_P (core))
810 /* OK */;
811 else if (!complete_type_or_else (core, from))
812 return 0;
813 }
814 return 1;
815 }
816
817 /* If IS_THROW is true return truth-value if T is an expression admissible
818 in throw-expression, i.e. if it is not of incomplete type or a pointer/
819 reference to such a type or of an abstract class type.
820 If IS_THROW is false, likewise for a catch parameter, same requirements
821 for its type plus rvalue reference type is also not admissible. */
822
823 static bool
824 is_admissible_throw_operand_or_catch_parameter (tree t, bool is_throw)
825 {
826 tree expr = is_throw ? t : NULL_TREE;
827 tree type = TREE_TYPE (t);
828
829 /* C++11 [except.handle] The exception-declaration shall not denote
830 an incomplete type, an abstract class type, or an rvalue reference
831 type. */
832
833 /* 15.1/4 [...] The type of the throw-expression shall not be an
834 incomplete type, or a pointer or a reference to an incomplete
835 type, other than void*, const void*, volatile void*, or
836 const volatile void*. Except for these restriction and the
837 restrictions on type matching mentioned in 15.3, the operand
838 of throw is treated exactly as a function argument in a call
839 (5.2.2) or the operand of a return statement. */
840 if (!complete_ptr_ref_or_void_ptr_p (type, expr))
841 return false;
842
843 /* 10.4/3 An abstract class shall not be used as a parameter type,
844 as a function return type or as type of an explicit
845 conversion. */
846 else if (abstract_virtuals_error (is_throw ? ACU_THROW : ACU_CATCH, type))
847 return false;
848 else if (!is_throw
849 && TREE_CODE (type) == REFERENCE_TYPE
850 && TYPE_REF_IS_RVALUE (type))
851 {
852 error ("cannot declare catch parameter to be of rvalue "
853 "reference type %qT", type);
854 return false;
855 }
856 else if (variably_modified_type_p (type, NULL_TREE))
857 {
858 if (is_throw)
859 error ("cannot throw expression of type %qT because it involves "
860 "types of variable size", type);
861 else
862 error ("cannot catch type %qT because it involves types of "
863 "variable size", type);
864 return false;
865 }
866
867 return true;
868 }
869
870 /* Returns nonzero if FN is a declaration of a standard C library
871 function which is known not to throw.
872
873 [lib.res.on.exception.handling]: None of the functions from the
874 Standard C library shall report an error by throwing an
875 exception, unless it calls a program-supplied function that
876 throws an exception. */
877
878 #include "cfns.h"
879
880 int
881 nothrow_libfn_p (const_tree fn)
882 {
883 tree id;
884
885 if (TREE_PUBLIC (fn)
886 && DECL_EXTERNAL (fn)
887 && DECL_NAMESPACE_SCOPE_P (fn)
888 && DECL_EXTERN_C_P (fn))
889 /* OK */;
890 else
891 /* Can't be a C library function. */
892 return 0;
893
894 /* Being a C library function, DECL_ASSEMBLER_NAME == DECL_NAME
895 unless the system headers are playing rename tricks, and if
896 they are, we don't want to be confused by them. */
897 id = DECL_NAME (fn);
898 const struct libc_name_struct *s
899 = libc_name::libc_name_p (IDENTIFIER_POINTER (id), IDENTIFIER_LENGTH (id));
900 if (s == NULL)
901 return 0;
902 switch (s->c_ver)
903 {
904 case 89: return 1;
905 case 99: return !flag_iso || flag_isoc99;
906 case 11: return !flag_iso || flag_isoc11;
907 default: gcc_unreachable ();
908 }
909 }
910
911 /* Returns nonzero if an exception of type FROM will be caught by a
912 handler for type TO, as per [except.handle]. */
913
914 static int
915 can_convert_eh (tree to, tree from)
916 {
917 to = non_reference (to);
918 from = non_reference (from);
919
920 if (TYPE_PTR_P (to) && TYPE_PTR_P (from))
921 {
922 to = TREE_TYPE (to);
923 from = TREE_TYPE (from);
924
925 if (! at_least_as_qualified_p (to, from))
926 return 0;
927
928 if (VOID_TYPE_P (to))
929 return 1;
930
931 /* Else fall through. */
932 }
933
934 if (CLASS_TYPE_P (to) && CLASS_TYPE_P (from)
935 && publicly_uniquely_derived_p (to, from))
936 return 1;
937
938 return 0;
939 }
940
941 /* Check whether any of the handlers in I are shadowed by another handler
942 accepting TYPE. Note that the shadowing may not be complete; even if
943 an exception of type B would be caught by a handler for A, there could
944 be a derived class C for which A is an ambiguous base but B is not, so
945 the handler for B would catch an exception of type C. */
946
947 static void
948 check_handlers_1 (tree master, tree_stmt_iterator i)
949 {
950 tree type = TREE_TYPE (master);
951
952 for (; !tsi_end_p (i); tsi_next (&i))
953 {
954 tree handler = tsi_stmt (i);
955 if (TREE_TYPE (handler) && can_convert_eh (type, TREE_TYPE (handler)))
956 {
957 warning_at (EXPR_LOCATION (handler), 0,
958 "exception of type %qT will be caught",
959 TREE_TYPE (handler));
960 warning_at (EXPR_LOCATION (master), 0,
961 " by earlier handler for %qT", type);
962 break;
963 }
964 }
965 }
966
967 /* Given a STATEMENT_LIST of HANDLERs, make sure that they're OK. */
968
969 void
970 check_handlers (tree handlers)
971 {
972 tree_stmt_iterator i;
973
974 /* If we don't have a STATEMENT_LIST, then we've just got one
975 handler, and thus nothing to warn about. */
976 if (TREE_CODE (handlers) != STATEMENT_LIST)
977 return;
978
979 i = tsi_start (handlers);
980 if (!tsi_end_p (i))
981 while (1)
982 {
983 tree handler = tsi_stmt (i);
984 tsi_next (&i);
985
986 /* No more handlers; nothing to shadow. */
987 if (tsi_end_p (i))
988 break;
989 if (TREE_TYPE (handler) == NULL_TREE)
990 permerror (EXPR_LOCATION (handler), "%<...%>"
991 " handler must be the last handler for its try block");
992 else
993 check_handlers_1 (handler, i);
994 }
995 }
996
997 /* walk_tree helper for finish_noexcept_expr. Returns non-null if the
998 expression *TP causes the noexcept operator to evaluate to false.
999
1000 5.3.7 [expr.noexcept]: The result of the noexcept operator is false if
1001 in a potentially-evaluated context the expression would contain
1002 * a potentially evaluated call to a function, member function,
1003 function pointer, or member function pointer that does not have a
1004 non-throwing exception-specification (15.4),
1005 * a potentially evaluated throw-expression (15.1),
1006 * a potentially evaluated dynamic_cast expression dynamic_cast<T>(v),
1007 where T is a reference type, that requires a run-time check (5.2.7), or
1008 * a potentially evaluated typeid expression (5.2.8) applied to a glvalue
1009 expression whose type is a polymorphic class type (10.3). */
1010
1011 static tree
1012 check_noexcept_r (tree *tp, int * /*walk_subtrees*/, void * /*data*/)
1013 {
1014 tree t = *tp;
1015 enum tree_code code = TREE_CODE (t);
1016 if ((code == CALL_EXPR && CALL_EXPR_FN (t))
1017 || code == AGGR_INIT_EXPR)
1018 {
1019 /* We can only use the exception specification of the called function
1020 for determining the value of a noexcept expression; we can't use
1021 TREE_NOTHROW, as it might have a different value in another
1022 translation unit, creating ODR problems.
1023
1024 We could use TREE_NOTHROW (t) for !TREE_PUBLIC fns, though... */
1025 tree fn = cp_get_callee (t);
1026 tree type = TREE_TYPE (fn);
1027 gcc_assert (POINTER_TYPE_P (type));
1028 type = TREE_TYPE (type);
1029
1030 STRIP_NOPS (fn);
1031 if (TREE_CODE (fn) == ADDR_EXPR)
1032 fn = TREE_OPERAND (fn, 0);
1033 if (TREE_CODE (fn) == FUNCTION_DECL)
1034 {
1035 /* We do use TREE_NOTHROW for ABI internals like __dynamic_cast,
1036 and for C library functions known not to throw. */
1037 if (DECL_EXTERN_C_P (fn)
1038 && (DECL_ARTIFICIAL (fn)
1039 || nothrow_libfn_p (fn)))
1040 return TREE_NOTHROW (fn) ? NULL_TREE : fn;
1041 /* A call to a constexpr function is noexcept if the call
1042 is a constant expression. */
1043 if (DECL_DECLARED_CONSTEXPR_P (fn)
1044 && is_sub_constant_expr (t))
1045 return NULL_TREE;
1046 }
1047 if (!TYPE_NOTHROW_P (type))
1048 return fn;
1049 }
1050
1051 return NULL_TREE;
1052 }
1053
1054 /* If a function that causes a noexcept-expression to be false isn't
1055 defined yet, remember it and check it for TREE_NOTHROW again at EOF. */
1056
1057 struct GTY(()) pending_noexcept {
1058 tree fn;
1059 location_t loc;
1060 };
1061 static GTY(()) vec<pending_noexcept, va_gc> *pending_noexcept_checks;
1062
1063 /* FN is a FUNCTION_DECL that caused a noexcept-expr to be false. Warn if
1064 it can't throw. */
1065
1066 static void
1067 maybe_noexcept_warning (tree fn)
1068 {
1069 if (TREE_NOTHROW (fn))
1070 {
1071 warning (OPT_Wnoexcept, "noexcept-expression evaluates to %<false%> "
1072 "because of a call to %qD", fn);
1073 warning_at (DECL_SOURCE_LOCATION (fn), OPT_Wnoexcept,
1074 "but %qD does not throw; perhaps "
1075 "it should be declared %<noexcept%>", fn);
1076 }
1077 }
1078
1079 /* Check any functions that weren't defined earlier when they caused a
1080 noexcept expression to evaluate to false. */
1081
1082 void
1083 perform_deferred_noexcept_checks (void)
1084 {
1085 int i;
1086 pending_noexcept *p;
1087 location_t saved_loc = input_location;
1088 FOR_EACH_VEC_SAFE_ELT (pending_noexcept_checks, i, p)
1089 {
1090 input_location = p->loc;
1091 maybe_noexcept_warning (p->fn);
1092 }
1093 input_location = saved_loc;
1094 }
1095
1096 /* Evaluate noexcept ( EXPR ). */
1097
1098 tree
1099 finish_noexcept_expr (tree expr, tsubst_flags_t complain)
1100 {
1101 if (expr == error_mark_node)
1102 return error_mark_node;
1103
1104 if (processing_template_decl)
1105 return build_min (NOEXCEPT_EXPR, boolean_type_node, expr);
1106
1107 return (expr_noexcept_p (expr, complain)
1108 ? boolean_true_node : boolean_false_node);
1109 }
1110
1111 /* Returns whether EXPR is noexcept, possibly warning if allowed by
1112 COMPLAIN. */
1113
1114 bool
1115 expr_noexcept_p (tree expr, tsubst_flags_t complain)
1116 {
1117 tree fn;
1118
1119 if (expr == error_mark_node)
1120 return false;
1121
1122 fn = cp_walk_tree_without_duplicates (&expr, check_noexcept_r, 0);
1123 if (fn)
1124 {
1125 if ((complain & tf_warning) && warn_noexcept
1126 && TREE_CODE (fn) == FUNCTION_DECL)
1127 {
1128 if (!DECL_INITIAL (fn))
1129 {
1130 /* Not defined yet; check again at EOF. */
1131 pending_noexcept p = {fn, input_location};
1132 vec_safe_push (pending_noexcept_checks, p);
1133 }
1134 else
1135 maybe_noexcept_warning (fn);
1136 }
1137 return false;
1138 }
1139 else
1140 return true;
1141 }
1142
1143 /* Return true iff SPEC is throw() or noexcept(true). */
1144
1145 bool
1146 nothrow_spec_p (const_tree spec)
1147 {
1148 gcc_assert (!DEFERRED_NOEXCEPT_SPEC_P (spec));
1149
1150 if (spec == empty_except_spec
1151 || spec == noexcept_true_spec)
1152 return true;
1153
1154 gcc_assert (!spec
1155 || TREE_VALUE (spec)
1156 || spec == noexcept_false_spec
1157 || TREE_PURPOSE (spec) == error_mark_node
1158 || processing_template_decl);
1159
1160 return false;
1161 }
1162
1163 /* For FUNCTION_TYPE or METHOD_TYPE, true if NODE is noexcept. This is the
1164 case for things declared noexcept(true) and, with -fnothrow-opt, for
1165 throw() functions. */
1166
1167 bool
1168 type_noexcept_p (const_tree type)
1169 {
1170 tree spec = TYPE_RAISES_EXCEPTIONS (type);
1171 gcc_assert (!DEFERRED_NOEXCEPT_SPEC_P (spec));
1172 if (flag_nothrow_opt)
1173 return nothrow_spec_p (spec);
1174 else
1175 return spec == noexcept_true_spec;
1176 }
1177
1178 /* For FUNCTION_TYPE or METHOD_TYPE, true if NODE can throw any type,
1179 i.e. no exception-specification or noexcept(false). */
1180
1181 bool
1182 type_throw_all_p (const_tree type)
1183 {
1184 tree spec = TYPE_RAISES_EXCEPTIONS (type);
1185 gcc_assert (!DEFERRED_NOEXCEPT_SPEC_P (spec));
1186 return spec == NULL_TREE || spec == noexcept_false_spec;
1187 }
1188
1189 /* Create a representation of the noexcept-specification with
1190 constant-expression of EXPR. COMPLAIN is as for tsubst. */
1191
1192 tree
1193 build_noexcept_spec (tree expr, int complain)
1194 {
1195 /* This isn't part of the signature, so don't bother trying to evaluate
1196 it until instantiation. */
1197 if (!processing_template_decl && TREE_CODE (expr) != DEFERRED_NOEXCEPT)
1198 {
1199 expr = perform_implicit_conversion_flags (boolean_type_node, expr,
1200 complain,
1201 LOOKUP_NORMAL);
1202 expr = cxx_constant_value (expr);
1203 }
1204 if (TREE_CODE (expr) == INTEGER_CST)
1205 {
1206 if (operand_equal_p (expr, boolean_true_node, 0))
1207 return noexcept_true_spec;
1208 else
1209 {
1210 gcc_checking_assert (operand_equal_p (expr, boolean_false_node, 0));
1211 return noexcept_false_spec;
1212 }
1213 }
1214 else if (expr == error_mark_node)
1215 return error_mark_node;
1216 else
1217 {
1218 gcc_assert (processing_template_decl
1219 || TREE_CODE (expr) == DEFERRED_NOEXCEPT);
1220 return build_tree_list (expr, NULL_TREE);
1221 }
1222 }
1223
1224 /* Returns a TRY_CATCH_EXPR that will put TRY_LIST and CATCH_LIST in the
1225 TRY and CATCH locations. CATCH_LIST must be a STATEMENT_LIST */
1226
1227 tree
1228 create_try_catch_expr (tree try_expr, tree catch_list)
1229 {
1230 location_t loc = EXPR_LOCATION (try_expr);
1231
1232 append_to_statement_list (do_begin_catch (), &catch_list);
1233 append_to_statement_list (build_throw (NULL_TREE), &catch_list);
1234 tree catch_tf_expr = build_stmt (loc, TRY_FINALLY_EXPR, catch_list,
1235 do_end_catch (NULL_TREE));
1236 catch_list = build2 (CATCH_EXPR, void_type_node, NULL_TREE,
1237 catch_tf_expr);
1238 tree try_catch_expr = build_stmt (loc, TRY_CATCH_EXPR, try_expr, catch_list);
1239 return try_catch_expr;
1240 }
1241
1242 #include "gt-cp-except.h"