1 /* Handle exceptional things in C++.
2 Copyright (C) 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
3 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
4 Contributed by Michael Tiemann <tiemann@cygnus.com>
5 Rewritten by Mike Stump <mrs@cygnus.com>, based upon an
6 initial re-implementation courtesy Tad Hunt.
7
8 This file is part of GCC.
9
10 GCC is free software; you can redistribute it and/or modify
11 it under the terms of the GNU General Public License as published by
12 the Free Software Foundation; either version 2, or (at your option)
13 any later version.
14
15 GCC is distributed in the hope that it will be useful,
16 but WITHOUT ANY WARRANTY; without even the implied warranty of
17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 GNU General Public License for more details.
19
20 You should have received a copy of the GNU General Public License
21 along with GCC; see the file COPYING. If not, write to
22 the Free Software Foundation, 59 Temple Place - Suite 330,
23 Boston, MA 02111-1307, USA. */
24
25
26 #include "config.h"
27 #include "system.h"
28 #include "coretypes.h"
29 #include "tm.h"
30 #include "tree.h"
31 #include "rtl.h"
32 #include "expr.h"
33 #include "libfuncs.h"
34 #include "cp-tree.h"
35 #include "flags.h"
36 #include "output.h"
37 #include "except.h"
38 #include "toplev.h"
39 #include "tree-inline.h"
40
41 static void push_eh_cleanup (tree);
42 static tree prepare_eh_type (tree);
43 static tree build_eh_type_type (tree);
44 static tree do_begin_catch (void);
45 static int dtor_nothrow (tree);
46 static tree do_end_catch (tree);
47 static bool decl_is_java_type (tree decl, int err);
48 static void initialize_handler_parm (tree, tree);
49 static tree do_allocate_exception (tree);
50 static tree wrap_cleanups_r (tree *, int *, void *);
51 static int complete_ptr_ref_or_void_ptr_p (tree, tree);
52 static bool is_admissible_throw_operand (tree);
53 static int can_convert_eh (tree, tree);
54 static void check_handlers_1 (tree, tree);
55 static tree cp_protect_cleanup_actions (void);
56
57 /* Sets up all the global eh stuff that needs to be initialized at the
58 start of compilation. */
59
60 void
init_exception_processing(void)61 init_exception_processing (void)
62 {
63 tree tmp;
64
65 /* void std::terminate (); */
66 push_namespace (std_identifier);
67 tmp = build_function_type (void_type_node, void_list_node);
68 terminate_node = build_cp_library_fn_ptr ("terminate", tmp);
69 TREE_THIS_VOLATILE (terminate_node) = 1;
70 TREE_NOTHROW (terminate_node) = 1;
71 pop_namespace ();
72
73 /* void __cxa_call_unexpected(void *); */
74 tmp = tree_cons (NULL_TREE, ptr_type_node, void_list_node);
75 tmp = build_function_type (void_type_node, tmp);
76 call_unexpected_node
77 = push_throw_library_fn (get_identifier ("__cxa_call_unexpected"), tmp);
78
79 eh_personality_libfunc = init_one_libfunc (USING_SJLJ_EXCEPTIONS
80 ? "__gxx_personality_sj0"
81 : "__gxx_personality_v0");
82
83 lang_eh_runtime_type = build_eh_type_type;
84 lang_protect_cleanup_actions = &cp_protect_cleanup_actions;
85 }
86
87 /* Returns an expression to be executed if an unhandled exception is
88 propagated out of a cleanup region. */
89
90 static tree
cp_protect_cleanup_actions(void)91 cp_protect_cleanup_actions (void)
92 {
93 /* [except.terminate]
94
95 When the destruction of an object during stack unwinding exits
96 using an exception ... void terminate(); is called. */
97 return build_call (terminate_node, NULL_TREE);
98 }
99
100 static tree
prepare_eh_type(tree type)101 prepare_eh_type (tree type)
102 {
103 if (type == NULL_TREE)
104 return type;
105 if (type == error_mark_node)
106 return error_mark_node;
107
108 /* peel back references, so they match. */
109 type = non_reference (type);
110
111 /* Peel off cv qualifiers. */
112 type = TYPE_MAIN_VARIANT (type);
113
114 return type;
115 }
116
117 /* Return the type info for TYPE as used by EH machinery. */
118 tree
eh_type_info(tree type)119 eh_type_info (tree type)
120 {
121 tree exp;
122
123 if (type == NULL_TREE || type == error_mark_node)
124 return type;
125
126 if (decl_is_java_type (type, 0))
127 exp = build_java_class_ref (TREE_TYPE (type));
128 else
129 exp = get_tinfo_decl (type);
130
131 return exp;
132 }
133
134 /* Build the address of a typeinfo decl for use in the runtime
135 matching field of the exception model. */
136
137 static tree
build_eh_type_type(tree type)138 build_eh_type_type (tree type)
139 {
140 tree exp = eh_type_info (type);
141
142 if (!exp)
143 return NULL;
144
145 mark_used (exp);
146
147 return build1 (ADDR_EXPR, ptr_type_node, exp);
148 }
149
150 tree
build_exc_ptr(void)151 build_exc_ptr (void)
152 {
153 return build (EXC_PTR_EXPR, ptr_type_node);
154 }
155
156 /* Build up a call to __cxa_begin_catch, to tell the runtime that the
157 exception has been handled. */
158
159 static tree
do_begin_catch(void)160 do_begin_catch (void)
161 {
162 tree fn;
163
164 fn = get_identifier ("__cxa_begin_catch");
165 if (!get_global_value_if_present (fn, &fn))
166 {
167 /* Declare void* __cxa_begin_catch (void *). */
168 tree tmp = tree_cons (NULL_TREE, ptr_type_node, void_list_node);
169 fn = push_library_fn (fn, build_function_type (ptr_type_node, tmp));
170 }
171
172 return build_function_call (fn, tree_cons (NULL_TREE, build_exc_ptr (),
173 NULL_TREE));
174 }
175
176 /* Returns nonzero if cleaning up an exception of type TYPE (which can be
177 NULL_TREE for a ... handler) will not throw an exception. */
178
179 static int
dtor_nothrow(tree type)180 dtor_nothrow (tree type)
181 {
182 if (type == NULL_TREE)
183 return 0;
184
185 if (! TYPE_HAS_DESTRUCTOR (type))
186 return 1;
187
188 return TREE_NOTHROW (CLASSTYPE_DESTRUCTORS (type));
189 }
190
191 /* Build up a call to __cxa_end_catch, to destroy the exception object
192 for the current catch block if no others are currently using it. */
193
194 static tree
do_end_catch(tree type)195 do_end_catch (tree type)
196 {
197 tree fn, cleanup;
198
199 fn = get_identifier ("__cxa_end_catch");
200 if (!get_global_value_if_present (fn, &fn))
201 {
202 /* Declare void __cxa_end_catch (). */
203 fn = push_void_library_fn (fn, void_list_node);
204 /* This can throw if the destructor for the exception throws. */
205 TREE_NOTHROW (fn) = 0;
206 }
207
208 cleanup = build_function_call (fn, NULL_TREE);
209 TREE_NOTHROW (cleanup) = dtor_nothrow (type);
210
211 return cleanup;
212 }
213
214 /* This routine creates the cleanup for the current exception. */
215
216 static void
push_eh_cleanup(tree type)217 push_eh_cleanup (tree type)
218 {
219 finish_decl_cleanup (NULL_TREE, do_end_catch (type));
220 }
221
222 /* Return nonzero value if DECL is a Java type suitable for catch or
223 throw. */
224
225 static bool
decl_is_java_type(tree decl,int err)226 decl_is_java_type (tree decl, int err)
227 {
228 bool r = (TREE_CODE (decl) == POINTER_TYPE
229 && TREE_CODE (TREE_TYPE (decl)) == RECORD_TYPE
230 && TYPE_FOR_JAVA (TREE_TYPE (decl)));
231
232 if (err)
233 {
234 if (TREE_CODE (decl) == REFERENCE_TYPE
235 && TREE_CODE (TREE_TYPE (decl)) == RECORD_TYPE
236 && TYPE_FOR_JAVA (TREE_TYPE (decl)))
237 {
238 /* Can't throw a reference. */
239 error ("type `%T' is disallowed in Java `throw' or `catch'",
240 decl);
241 }
242
243 if (r)
244 {
245 tree jthrow_node
246 = IDENTIFIER_GLOBAL_VALUE (get_identifier ("jthrowable"));
247
248 if (jthrow_node == NULL_TREE)
249 fatal_error
250 ("call to Java `catch' or `throw' with `jthrowable' undefined");
251
252 jthrow_node = TREE_TYPE (TREE_TYPE (jthrow_node));
253
254 if (! DERIVED_FROM_P (jthrow_node, TREE_TYPE (decl)))
255 {
256 /* Thrown object must be a Throwable. */
257 error ("type `%T' is not derived from `java::lang::Throwable'",
258 TREE_TYPE (decl));
259 }
260 }
261 }
262
263 return r;
264 }
265
266 /* Select the personality routine to be used for exception handling,
267 or issue an error if we need two different ones in the same
268 translation unit.
269 ??? At present eh_personality_libfunc is set to
270 __gxx_personality_(sj|v)0 in init_exception_processing - should it
271 be done here instead? */
272 void
choose_personality_routine(enum languages lang)273 choose_personality_routine (enum languages lang)
274 {
275 static enum {
276 chose_none,
277 chose_cpp,
278 chose_java,
279 gave_error
280 } state;
281
282 switch (state)
283 {
284 case gave_error:
285 return;
286
287 case chose_cpp:
288 if (lang != lang_cplusplus)
289 goto give_error;
290 return;
291
292 case chose_java:
293 if (lang != lang_java)
294 goto give_error;
295 return;
296
297 case chose_none:
298 ; /* Proceed to language selection. */
299 }
300
301 switch (lang)
302 {
303 case lang_cplusplus:
304 state = chose_cpp;
305 break;
306
307 case lang_java:
308 state = chose_java;
309 eh_personality_libfunc = init_one_libfunc (USING_SJLJ_EXCEPTIONS
310 ? "__gcj_personality_sj0"
311 : "__gcj_personality_v0");
312 break;
313
314 default:
315 abort ();
316 }
317 return;
318
319 give_error:
320 error ("mixing C++ and Java catches in a single translation unit");
321 state = gave_error;
322 }
323
324 /* Initialize the catch parameter DECL. */
325
326 static void
initialize_handler_parm(tree decl,tree exp)327 initialize_handler_parm (tree decl, tree exp)
328 {
329 tree init;
330 tree init_type;
331
332 /* Make sure we mark the catch param as used, otherwise we'll get a
333 warning about an unused ((anonymous)). */
334 TREE_USED (decl) = 1;
335
336 /* Figure out the type that the initializer is. Pointers are returned
337 adjusted by value from __cxa_begin_catch. Others are returned by
338 reference. */
339 init_type = TREE_TYPE (decl);
340 if (! TYPE_PTR_P (init_type)
341 && TREE_CODE (init_type) != REFERENCE_TYPE)
342 init_type = build_reference_type (init_type);
343
344 choose_personality_routine (decl_is_java_type (init_type, 0)
345 ? lang_java : lang_cplusplus);
346
347 /* Since pointers are passed by value, initialize a reference to
348 pointer catch parm with the address of the temporary. */
349 if (TREE_CODE (init_type) == REFERENCE_TYPE
350 && TYPE_PTR_P (TREE_TYPE (init_type)))
351 exp = build_unary_op (ADDR_EXPR, exp, 1);
352
353 exp = ocp_convert (init_type, exp, CONV_IMPLICIT|CONV_FORCE_TEMP, 0);
354
355 init = convert_from_reference (exp);
356
357 /* If the constructor for the catch parm exits via an exception, we
358 must call terminate. See eh23.C. */
359 if (TYPE_NEEDS_CONSTRUCTING (TREE_TYPE (decl)))
360 {
361 /* Generate the copy constructor call directly so we can wrap it.
362 See also expand_default_init. */
363 init = ocp_convert (TREE_TYPE (decl), init,
364 CONV_IMPLICIT|CONV_FORCE_TEMP, 0);
365 init = build1 (MUST_NOT_THROW_EXPR, TREE_TYPE (init), init);
366 }
367
368 /* Let `cp_finish_decl' know that this initializer is ok. */
369 DECL_INITIAL (decl) = error_mark_node;
370 decl = pushdecl (decl);
371
372 start_decl_1 (decl);
373 cp_finish_decl (decl, init, NULL_TREE,
374 LOOKUP_ONLYCONVERTING|DIRECT_BIND);
375 }
376
377 /* Call this to start a catch block. DECL is the catch parameter. */
378
379 tree
expand_start_catch_block(tree decl)380 expand_start_catch_block (tree decl)
381 {
382 tree exp = NULL_TREE;
383 tree type;
384 bool is_java;
385
386 if (! doing_eh (1))
387 return NULL_TREE;
388
389 /* Make sure this declaration is reasonable. */
390 if (decl && !complete_ptr_ref_or_void_ptr_p (TREE_TYPE (decl), NULL_TREE))
391 decl = NULL_TREE;
392
393 if (decl)
394 type = prepare_eh_type (TREE_TYPE (decl));
395 else
396 type = NULL_TREE;
397
398 is_java = false;
399 if (decl)
400 {
401 tree init;
402
403 if (decl_is_java_type (type, 1))
404 {
405 /* Java only passes object via pointer and doesn't require
406 adjusting. The java object is immediately before the
407 generic exception header. */
408 init = build_exc_ptr ();
409 init = build1 (NOP_EXPR, build_pointer_type (type), init);
410 init = build (MINUS_EXPR, TREE_TYPE (init), init,
411 TYPE_SIZE_UNIT (TREE_TYPE (init)));
412 init = build_indirect_ref (init, NULL);
413 is_java = true;
414 }
415 else
416 {
417 /* C++ requires that we call __cxa_begin_catch to get the
418 pointer to the actual object. */
419 init = do_begin_catch ();
420 }
421
422 exp = create_temporary_var (ptr_type_node);
423 DECL_REGISTER (exp) = 1;
424 cp_finish_decl (exp, init, NULL_TREE, LOOKUP_ONLYCONVERTING);
425 finish_expr_stmt (build_modify_expr (exp, INIT_EXPR, init));
426 }
427 else
428 finish_expr_stmt (do_begin_catch ());
429
430 /* C++ requires that we call __cxa_end_catch at the end of
431 processing the exception. */
432 if (! is_java)
433 push_eh_cleanup (type);
434
435 if (decl)
436 initialize_handler_parm (decl, exp);
437
438 return type;
439 }
440
441
442 /* Call this to end a catch block. Its responsible for emitting the
443 code to handle jumping back to the correct place, and for emitting
444 the label to jump to if this catch block didn't match. */
445
446 void
expand_end_catch_block(void)447 expand_end_catch_block (void)
448 {
449 if (! doing_eh (1))
450 return;
451
452 /* The exception being handled is rethrown if control reaches the end of
453 a handler of the function-try-block of a constructor or destructor. */
454 if (in_function_try_handler
455 && (DECL_CONSTRUCTOR_P (current_function_decl)
456 || DECL_DESTRUCTOR_P (current_function_decl)))
457 finish_expr_stmt (build_throw (NULL_TREE));
458 }
459
460 tree
begin_eh_spec_block(void)461 begin_eh_spec_block (void)
462 {
463 tree r = build_stmt (EH_SPEC_BLOCK, NULL_TREE, NULL_TREE);
464 add_stmt (r);
465 return r;
466 }
467
468 void
finish_eh_spec_block(tree raw_raises,tree eh_spec_block)469 finish_eh_spec_block (tree raw_raises, tree eh_spec_block)
470 {
471 tree raises;
472
473 RECHAIN_STMTS (eh_spec_block, EH_SPEC_STMTS (eh_spec_block));
474
475 /* Strip cv quals, etc, from the specification types. */
476 for (raises = NULL_TREE;
477 raw_raises && TREE_VALUE (raw_raises);
478 raw_raises = TREE_CHAIN (raw_raises))
479 {
480 tree type = prepare_eh_type (TREE_VALUE (raw_raises));
481 tree tinfo = eh_type_info (type);
482
483 mark_used (tinfo);
484 raises = tree_cons (NULL_TREE, type, raises);
485 }
486
487 EH_SPEC_RAISES (eh_spec_block) = raises;
488 }
489
490 /* Return a pointer to a buffer for an exception object of type TYPE. */
491
492 static tree
do_allocate_exception(tree type)493 do_allocate_exception (tree type)
494 {
495 tree fn;
496
497 fn = get_identifier ("__cxa_allocate_exception");
498 if (!get_global_value_if_present (fn, &fn))
499 {
500 /* Declare void *__cxa_allocate_exception(size_t). */
501 tree tmp = tree_cons (NULL_TREE, size_type_node, void_list_node);
502 fn = push_library_fn (fn, build_function_type (ptr_type_node, tmp));
503 }
504
505 return build_function_call (fn, tree_cons (NULL_TREE, size_in_bytes (type),
506 NULL_TREE));
507 }
508
509 /* Call __cxa_free_exception from a cleanup. This is never invoked
510 directly, but see the comment for stabilize_throw_expr. */
511
512 static tree
do_free_exception(tree ptr)513 do_free_exception (tree ptr)
514 {
515 tree fn;
516
517 fn = get_identifier ("__cxa_free_exception");
518 if (!get_global_value_if_present (fn, &fn))
519 {
520 /* Declare void __cxa_free_exception (void *). */
521 fn = push_void_library_fn (fn, tree_cons (NULL_TREE, ptr_type_node,
522 void_list_node));
523 }
524
525 return build_function_call (fn, tree_cons (NULL_TREE, ptr, NULL_TREE));
526 }
527
528 /* Wrap all cleanups for TARGET_EXPRs in MUST_NOT_THROW_EXPR.
529 Called from build_throw via walk_tree_without_duplicates. */
530
531 static tree
wrap_cleanups_r(tree * tp,int * walk_subtrees ATTRIBUTE_UNUSED,void * data ATTRIBUTE_UNUSED)532 wrap_cleanups_r (tree *tp, int *walk_subtrees ATTRIBUTE_UNUSED,
533 void *data ATTRIBUTE_UNUSED)
534 {
535 tree exp = *tp;
536 tree cleanup;
537
538 /* Don't walk into types. */
539 if (TYPE_P (exp))
540 {
541 *walk_subtrees = 0;
542 return NULL_TREE;
543 }
544 if (TREE_CODE (exp) != TARGET_EXPR)
545 return NULL_TREE;
546
547 cleanup = TARGET_EXPR_CLEANUP (exp);
548 if (cleanup)
549 {
550 cleanup = build1 (MUST_NOT_THROW_EXPR, void_type_node, cleanup);
551 TARGET_EXPR_CLEANUP (exp) = cleanup;
552 }
553
554 /* Keep iterating. */
555 return NULL_TREE;
556 }
557
558 /* Build a throw expression. */
559
560 tree
build_throw(tree exp)561 build_throw (tree exp)
562 {
563 tree fn;
564
565 if (exp == error_mark_node)
566 return exp;
567
568 if (processing_template_decl)
569 {
570 current_function_returns_abnormally = 1;
571 return build_min (THROW_EXPR, void_type_node, exp);
572 }
573
574 if (exp == null_node)
575 warning ("throwing NULL, which has integral, not pointer type");
576
577 if (exp != NULL_TREE)
578 {
579 if (!is_admissible_throw_operand (exp))
580 return error_mark_node;
581 }
582
583 if (! doing_eh (1))
584 return error_mark_node;
585
586 if (exp && decl_is_java_type (TREE_TYPE (exp), 1))
587 {
588 tree fn = get_identifier ("_Jv_Throw");
589 if (!get_global_value_if_present (fn, &fn))
590 {
591 /* Declare void _Jv_Throw (void *). */
592 tree tmp = tree_cons (NULL_TREE, ptr_type_node, void_list_node);
593 tmp = build_function_type (ptr_type_node, tmp);
594 fn = push_throw_library_fn (fn, tmp);
595 }
596 else if (really_overloaded_fn (fn))
597 {
598 error ("`%D' should never be overloaded", fn);
599 return error_mark_node;
600 }
601 fn = OVL_CURRENT (fn);
602 exp = build_function_call (fn, tree_cons (NULL_TREE, exp, NULL_TREE));
603 }
604 else if (exp)
605 {
606 tree throw_type;
607 tree cleanup;
608 tree object, ptr;
609 tree tmp;
610 tree temp_expr, allocate_expr;
611 bool elided;
612
613 /* The CLEANUP_TYPE is the internal type of a destructor. */
614 if (!cleanup_type)
615 {
616 tmp = void_list_node;
617 tmp = tree_cons (NULL_TREE, ptr_type_node, tmp);
618 tmp = build_function_type (void_type_node, tmp);
619 cleanup_type = build_pointer_type (tmp);
620 }
621
622 fn = get_identifier ("__cxa_throw");
623 if (!get_global_value_if_present (fn, &fn))
624 {
625 /* Declare void __cxa_throw (void*, void*, void (*)(void*)). */
626 /* ??? Second argument is supposed to be "std::type_info*". */
627 tmp = void_list_node;
628 tmp = tree_cons (NULL_TREE, cleanup_type, tmp);
629 tmp = tree_cons (NULL_TREE, ptr_type_node, tmp);
630 tmp = tree_cons (NULL_TREE, ptr_type_node, tmp);
631 tmp = build_function_type (void_type_node, tmp);
632 fn = push_throw_library_fn (fn, tmp);
633 }
634
635 /* throw expression */
636 /* First, decay it. */
637 exp = decay_conversion (exp);
638
639 /* OK, this is kind of wacky. The standard says that we call
640 terminate when the exception handling mechanism, after
641 completing evaluation of the expression to be thrown but
642 before the exception is caught (_except.throw_), calls a
643 user function that exits via an uncaught exception.
644
645 So we have to protect the actual initialization of the
646 exception object with terminate(), but evaluate the
647 expression first. Since there could be temps in the
648 expression, we need to handle that, too. We also expand
649 the call to __cxa_allocate_exception first (which doesn't
650 matter, since it can't throw). */
651
652 /* Allocate the space for the exception. */
653 allocate_expr = do_allocate_exception (TREE_TYPE (exp));
654 allocate_expr = get_target_expr (allocate_expr);
655 ptr = TARGET_EXPR_SLOT (allocate_expr);
656 object = build1 (NOP_EXPR, build_pointer_type (TREE_TYPE (exp)), ptr);
657 object = build_indirect_ref (object, NULL);
658
659 elided = (TREE_CODE (exp) == TARGET_EXPR);
660
661 /* And initialize the exception object. */
662 exp = build_init (object, exp, LOOKUP_ONLYCONVERTING);
663 if (exp == error_mark_node)
664 {
665 error (" in thrown expression");
666 return error_mark_node;
667 }
668
669 /* Pre-evaluate the thrown expression first, since if we allocated
670 the space first we would have to deal with cleaning it up if
671 evaluating this expression throws.
672
673 The case where EXP the initializer is a call to a constructor or a
674 function returning a class is a bit of a grey area in the
675 standard; it's unclear whether or not it should be allowed to
676 throw. We used to say no, as that allowed us to optimize this
677 case without worrying about deallocating the exception object if
678 it does. But that conflicted with expectations (PR 13944) and the
679 EDG compiler; now we wrap the initialization in a TRY_CATCH_EXPR
680 to call do_free_exception rather than in a MUST_NOT_THROW_EXPR,
681 for this case only.
682
683 Note that we don't check the return value from stabilize_init
684 because it will only return false in cases where elided is true,
685 and therefore we don't need to work around the failure to
686 preevaluate. */
687 temp_expr = NULL_TREE;
688 stabilize_init (exp, &temp_expr);
689
690 if (elided)
691 exp = build (TRY_CATCH_EXPR, void_type_node, exp,
692 do_free_exception (ptr));
693 else
694 exp = build1 (MUST_NOT_THROW_EXPR, void_type_node, exp);
695
696 /* Prepend the allocation. */
697 exp = build (COMPOUND_EXPR, TREE_TYPE (exp), allocate_expr, exp);
698 if (temp_expr)
699 {
700 /* Prepend the calculation of the throw expression. Also, force
701 any cleanups from the expression to be evaluated here so that
702 we don't have to do them during unwinding. But first wrap
703 them in MUST_NOT_THROW_EXPR, since they are run after the
704 exception object is initialized. */
705 walk_tree_without_duplicates (&temp_expr, wrap_cleanups_r, 0);
706 exp = build (COMPOUND_EXPR, TREE_TYPE (exp), temp_expr, exp);
707 exp = build1 (CLEANUP_POINT_EXPR, TREE_TYPE (exp), exp);
708 }
709
710 throw_type = build_eh_type_type (prepare_eh_type (TREE_TYPE (object)));
711
712 if (TYPE_HAS_DESTRUCTOR (TREE_TYPE (object)))
713 {
714 cleanup = lookup_fnfields (TYPE_BINFO (TREE_TYPE (object)),
715 complete_dtor_identifier, 0);
716 cleanup = BASELINK_FUNCTIONS (cleanup);
717 mark_used (cleanup);
718 cxx_mark_addressable (cleanup);
719 /* Pretend it's a normal function. */
720 cleanup = build1 (ADDR_EXPR, cleanup_type, cleanup);
721 }
722 else
723 {
724 cleanup = build_int_2 (0, 0);
725 TREE_TYPE (cleanup) = cleanup_type;
726 }
727
728 tmp = tree_cons (NULL_TREE, cleanup, NULL_TREE);
729 tmp = tree_cons (NULL_TREE, throw_type, tmp);
730 tmp = tree_cons (NULL_TREE, ptr, tmp);
731 /* ??? Indicate that this function call throws throw_type. */
732 tmp = build_function_call (fn, tmp);
733
734 /* Tack on the initialization stuff. */
735 exp = build (COMPOUND_EXPR, TREE_TYPE (tmp), exp, tmp);
736 }
737 else
738 {
739 /* Rethrow current exception. */
740
741 tree fn = get_identifier ("__cxa_rethrow");
742 if (!get_global_value_if_present (fn, &fn))
743 {
744 /* Declare void __cxa_rethrow (void). */
745 fn = push_throw_library_fn
746 (fn, build_function_type (void_type_node, void_list_node));
747 }
748
749 /* ??? Indicate that this function call allows exceptions of the type
750 of the enclosing catch block (if known). */
751 exp = build_function_call (fn, NULL_TREE);
752 }
753
754 exp = build1 (THROW_EXPR, void_type_node, exp);
755
756 return exp;
757 }
758
759 /* Make sure TYPE is complete, pointer to complete, reference to
760 complete, or pointer to cv void. Issue diagnostic on failure.
761 Return the zero on failure and nonzero on success. FROM can be
762 the expr or decl from whence TYPE came, if available. */
763
764 static int
complete_ptr_ref_or_void_ptr_p(tree type,tree from)765 complete_ptr_ref_or_void_ptr_p (tree type, tree from)
766 {
767 int is_ptr;
768
769 /* Check complete. */
770 type = complete_type_or_else (type, from);
771 if (!type)
772 return 0;
773
774 /* Or a pointer or ref to one, or cv void *. */
775 is_ptr = TREE_CODE (type) == POINTER_TYPE;
776 if (is_ptr || TREE_CODE (type) == REFERENCE_TYPE)
777 {
778 tree core = TREE_TYPE (type);
779
780 if (is_ptr && VOID_TYPE_P (core))
781 /* OK */;
782 else if (!complete_type_or_else (core, from))
783 return 0;
784 }
785 return 1;
786 }
787
788 /* Return truth-value if EXPRESSION is admissible in throw-expression,
789 i.e. if it is not of incomplete type or a pointer/reference to such
790 a type or of an abstract class type. */
791
792 static bool
is_admissible_throw_operand(tree expr)793 is_admissible_throw_operand (tree expr)
794 {
795 tree type = TREE_TYPE (expr);
796
797 /* 15.1/4 [...] The type of the throw-expression shall not be an
798 incomplete type, or a pointer or a reference to an incomplete
799 type, other than void*, const void*, volatile void*, or
800 const volatile void*. Except for these restriction and the
801 restrictions on type matching mentioned in 15.3, the operand
802 of throw is treated exactly as a function argument in a call
803 (5.2.2) or the operand of a return statement. */
804 if (!complete_ptr_ref_or_void_ptr_p (type, expr))
805 return false;
806
807 /* 10.4/3 An abstract class shall not be used as a parameter type,
808 as a function return type or as type of an explicit
809 conversion. */
810 else if (CLASS_TYPE_P (type) && CLASSTYPE_PURE_VIRTUALS (type))
811 {
812 error ("expression '%E' of abstract class type '%T' cannot be used in throw-expression", expr, type);
813 return false;
814 }
815
816 return true;
817 }
818
819 /* Returns nonzero if FN is a declaration of a standard C library
820 function which is known not to throw.
821
822 [lib.res.on.exception.handling]: None of the functions from the
823 Standard C library shall report an error by throwing an
824 exception, unless it calls a program-supplied function that
825 throws an exception. */
826
827 #include "cfns.h"
828
829 int
nothrow_libfn_p(tree fn)830 nothrow_libfn_p (tree fn)
831 {
832 tree id;
833
834 if (TREE_PUBLIC (fn)
835 && DECL_EXTERNAL (fn)
836 && DECL_NAMESPACE_SCOPE_P (fn)
837 && DECL_EXTERN_C_P (fn))
838 /* OK */;
839 else
840 /* Can't be a C library function. */
841 return 0;
842
843 id = DECL_ASSEMBLER_NAME (fn);
844 return !!libc_name_p (IDENTIFIER_POINTER (id), IDENTIFIER_LENGTH (id));
845 }
846
847 /* Returns nonzero if an exception of type FROM will be caught by a
848 handler for type TO, as per [except.handle]. */
849
850 static int
can_convert_eh(tree to,tree from)851 can_convert_eh (tree to, tree from)
852 {
853 to = non_reference (to);
854 from = non_reference (from);
855
856 if (TREE_CODE (to) == POINTER_TYPE && TREE_CODE (from) == POINTER_TYPE)
857 {
858 to = TREE_TYPE (to);
859 from = TREE_TYPE (from);
860
861 if (! at_least_as_qualified_p (to, from))
862 return 0;
863
864 if (TREE_CODE (to) == VOID_TYPE)
865 return 1;
866
867 /* Else fall through. */
868 }
869
870 if (CLASS_TYPE_P (to) && CLASS_TYPE_P (from)
871 && PUBLICLY_UNIQUELY_DERIVED_P (to, from))
872 return 1;
873
874 return 0;
875 }
876
877 /* Check whether any of HANDLERS are shadowed by another handler accepting
878 TYPE. Note that the shadowing may not be complete; even if an exception
879 of type B would be caught by a handler for A, there could be a derived
880 class C for which A is an ambiguous base but B is not, so the handler
881 for B would catch an exception of type C. */
882
883 static void
check_handlers_1(tree master,tree handlers)884 check_handlers_1 (tree master, tree handlers)
885 {
886 tree type = TREE_TYPE (master);
887 tree handler;
888
889 for (handler = handlers; handler; handler = TREE_CHAIN (handler))
890 if (TREE_TYPE (handler)
891 && can_convert_eh (type, TREE_TYPE (handler)))
892 {
893 input_line = STMT_LINENO (handler);
894 warning ("exception of type `%T' will be caught",
895 TREE_TYPE (handler));
896 input_line = STMT_LINENO (master);
897 warning (" by earlier handler for `%T'", type);
898 break;
899 }
900 }
901
902 /* Given a chain of HANDLERs, make sure that they're OK. */
903
904 void
check_handlers(tree handlers)905 check_handlers (tree handlers)
906 {
907 tree handler;
908 int save_line = input_line;
909
910 for (handler = handlers; handler; handler = TREE_CHAIN (handler))
911 {
912 if (TREE_CHAIN (handler) == NULL_TREE)
913 /* No more handlers; nothing to shadow. */;
914 else if (TREE_TYPE (handler) == NULL_TREE)
915 {
916 input_line = STMT_LINENO (handler);
917 pedwarn
918 ("`...' handler must be the last handler for its try block");
919 }
920 else
921 check_handlers_1 (handler, TREE_CHAIN (handler));
922 }
923 input_line = save_line;
924 }
925