1 /* Handle exceptional things in C++.
2 Copyright (C) 1989-2023 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.
7 This file is part of GCC.
9 GCC is free software; you can redistribute it and/or modify
10 it under the terms of the GNU General Public License as published by
11 the Free Software Foundation; either version 3, or (at your option)
14 GCC is distributed in the hope that it will be useful,
15 but WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License for more details.
19 You should have received a copy of the GNU General Public License
20 along with GCC; see the file COPYING3. If not see
21 <http://www.gnu.org/licenses/>. */
26 #include "coretypes.h"
28 #include "stringpool.h"
29 #include "trans-mem.h"
31 #include "tree-iterator.h"
34 static void push_eh_cleanup (tree
);
35 static tree
prepare_eh_type (tree
);
36 static tree
do_begin_catch (void);
37 static int dtor_nothrow (tree
);
38 static tree
do_end_catch (tree
);
39 static void initialize_handler_parm (tree
, tree
);
40 static tree
do_allocate_exception (tree
);
41 static tree
wrap_cleanups_r (tree
*, int *, void *);
42 static int complete_ptr_ref_or_void_ptr_p (tree
, tree
);
43 static bool is_admissible_throw_operand_or_catch_parameter (tree
, bool);
45 /* Sets up all the global eh stuff that needs to be initialized at the
46 start of compilation. */
49 init_exception_processing (void)
53 /* void std::terminate (); */
54 push_nested_namespace (std_node
);
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
59 gcc_checking_assert (TREE_THIS_VOLATILE (terminate_fn
)
60 && TREE_NOTHROW (terminate_fn
));
61 pop_nested_namespace (std_node
);
63 /* void __cxa_call_unexpected(void *); */
64 tmp
= build_function_type_list (void_type_node
, ptr_type_node
, NULL_TREE
);
66 = push_throw_library_fn (get_identifier ("__cxa_call_unexpected"), tmp
);
68 = push_library_fn (get_identifier ("__cxa_call_terminate"), tmp
, NULL_TREE
,
69 ECF_NORETURN
| ECF_COLD
| ECF_NOTHROW
);
72 /* Returns an expression to be executed if an unhandled exception is
73 propagated out of a cleanup region. */
76 cp_protect_cleanup_actions (void)
80 When the destruction of an object during stack unwinding exits
81 using an exception ... void terminate(); is called. */
82 return call_terminate_fn
;
86 prepare_eh_type (tree type
)
88 if (type
== NULL_TREE
)
90 if (type
== error_mark_node
)
91 return error_mark_node
;
93 /* peel back references, so they match. */
94 type
= non_reference (type
);
96 /* Peel off cv qualifiers. */
97 type
= TYPE_MAIN_VARIANT (type
);
99 /* Functions and arrays decay to pointers. */
100 type
= type_decays_to (type
);
105 /* Return the type info for TYPE as used by EH machinery. */
107 eh_type_info (tree type
)
109 if (type
== NULL_TREE
|| type
== error_mark_node
)
112 return get_tinfo_decl (type
);
115 /* Build the address of a typeinfo decl for use in the runtime
116 matching field of the exception model. */
119 build_eh_type_type (tree type
)
121 tree exp
= eh_type_info (type
);
128 return convert (ptr_type_node
, build_address (exp
));
134 return build_call_n (builtin_decl_explicit (BUILT_IN_EH_POINTER
),
135 1, integer_zero_node
);
138 /* Declare an exception ABI entry point called NAME.
139 ECF are the library flags, RTYPE the return type and ARGS[NARGS]
140 the parameter types. We return the DECL -- which might be one
141 found via the symbol table pushing, if the user already declared
142 it. If we pushed a new decl, the user will see it. */
145 declare_library_fn_1 (const char *name
, int ecf
,
146 tree rtype
, int nargs
, tree args
[])
148 tree ident
= get_identifier (name
);
149 tree except
= ecf
& ECF_NOTHROW
? empty_except_spec
: NULL_TREE
;
151 /* Make a new decl. */
152 tree arg_list
= void_list_node
;
153 for (unsigned ix
= nargs
; ix
--;)
154 arg_list
= tree_cons (NULL_TREE
, args
[ix
], arg_list
);
155 tree fntype
= build_function_type (rtype
, arg_list
);
156 tree res
= push_library_fn (ident
, fntype
, except
, ecf
);
161 /* Find or declare a function NAME, returning RTYPE, taking a single
162 parameter PTYPE, with an empty exception specification. ECF are the
163 library fn flags. If TM_ECF is non-zero, also find or create a
164 transaction variant and record it as a replacement, when flag_tm is
167 Note that the C++ ABI document does not have a throw-specifier on
168 the routines declared below via this function. The declarations
169 are consistent with the actual implementations in libsupc++. */
172 declare_library_fn (const char *name
, tree rtype
, tree ptype
,
175 tree res
= declare_library_fn_1 (name
, ecf
, rtype
, ptype
? 1 : 0, &ptype
);
176 if (res
== error_mark_node
)
179 if (tm_ecf
&& flag_tm
)
181 char *tm_name
= concat ("_ITM_", name
+ 2, NULL_TREE
);
183 tree tm_fn
= declare_library_fn_1 (tm_name
, ecf
| tm_ecf
, rtype
,
184 ptype
? 1 : 0, &ptype
);
186 if (tm_fn
!= error_mark_node
)
187 record_tm_replacement (res
, tm_fn
);
193 /* Build up a call to __cxa_get_exception_ptr so that we can build a
194 copy constructor for the thrown object. */
197 do_get_exception_ptr (void)
199 if (!get_exception_ptr_fn
)
200 /* Declare void* __cxa_get_exception_ptr (void *) throw(). */
202 = declare_library_fn ("__cxa_get_exception_ptr",
203 ptr_type_node
, ptr_type_node
,
204 ECF_NOTHROW
| ECF_PURE
| ECF_LEAF
| ECF_TM_PURE
,
207 return cp_build_function_call_nary (get_exception_ptr_fn
,
209 build_exc_ptr (), NULL_TREE
);
212 /* Build up a call to __cxa_begin_catch, to tell the runtime that the
213 exception has been handled. */
216 do_begin_catch (void)
219 /* Declare void* __cxa_begin_catch (void *) throw(). */
221 = declare_library_fn ("__cxa_begin_catch",
222 ptr_type_node
, ptr_type_node
, ECF_NOTHROW
,
225 return cp_build_function_call_nary (begin_catch_fn
, tf_warning_or_error
,
226 build_exc_ptr (), NULL_TREE
);
229 /* Returns nonzero if cleaning up an exception of type TYPE (which can be
230 NULL_TREE for a ... handler) will not throw an exception. */
233 dtor_nothrow (tree type
)
235 if (type
== NULL_TREE
|| type
== error_mark_node
)
238 if (TYPE_HAS_TRIVIAL_DESTRUCTOR (type
))
241 if (CLASSTYPE_LAZY_DESTRUCTOR (type
))
242 lazily_declare_fn (sfk_destructor
, type
);
244 return TREE_NOTHROW (CLASSTYPE_DESTRUCTOR (type
));
247 /* Build up a call to __cxa_end_catch, to destroy the exception object
248 for the current catch block if no others are currently using it. */
251 do_end_catch (tree type
)
254 /* Declare void __cxa_end_catch ().
255 This can throw if the destructor for the exception throws. */
257 = declare_library_fn ("__cxa_end_catch", void_type_node
,
258 NULL_TREE
, 0, ECF_TM_PURE
);
260 tree cleanup
= cp_build_function_call_vec (end_catch_fn
,
261 NULL
, tf_warning_or_error
);
262 if (cleanup
!= error_mark_node
)
263 TREE_NOTHROW (cleanup
) = dtor_nothrow (type
);
268 /* This routine creates the cleanup for the current exception. */
271 push_eh_cleanup (tree type
)
273 finish_decl_cleanup (NULL_TREE
, do_end_catch (type
));
276 /* Wrap EXPR in a MUST_NOT_THROW_EXPR expressing that EXPR must
277 not throw any exceptions if COND is true. A condition of
278 NULL_TREE is treated as 'true'. */
281 build_must_not_throw_expr (tree body
, tree cond
)
283 tree type
= body
? TREE_TYPE (body
) : void_type_node
;
285 if (!flag_exceptions
)
289 /* OK, unconditional. */;
292 tree conv
= NULL_TREE
;
293 if (!type_dependent_expression_p (cond
))
294 conv
= perform_implicit_conversion_flags (boolean_type_node
, cond
,
297 if (tree inst
= instantiate_non_dependent_or_null (conv
))
298 cond
= cxx_constant_value (inst
);
300 require_constant_expression (cond
);
301 if (integer_zerop (cond
))
303 else if (integer_onep (cond
))
307 return build2 (MUST_NOT_THROW_EXPR
, type
, body
, cond
);
311 /* Initialize the catch parameter DECL. */
314 initialize_handler_parm (tree decl
, tree exp
)
319 /* Make sure we mark the catch param as used, otherwise we'll get a
320 warning about an unused ((anonymous)). */
321 TREE_USED (decl
) = 1;
322 DECL_READ_P (decl
) = 1;
324 /* Figure out the type that the initializer is. Pointers are returned
325 adjusted by value from __cxa_begin_catch. Others are returned by
327 init_type
= TREE_TYPE (decl
);
328 if (!INDIRECT_TYPE_P (init_type
))
329 init_type
= build_reference_type (init_type
);
331 /* Since pointers are passed by value, initialize a reference to
332 pointer catch parm with the address of the temporary. */
333 if (TYPE_REF_P (init_type
)
334 && TYPE_PTR_P (TREE_TYPE (init_type
)))
335 exp
= cp_build_addr_expr (exp
, tf_warning_or_error
);
337 exp
= ocp_convert (init_type
, exp
, CONV_IMPLICIT
|CONV_FORCE_TEMP
, 0,
338 tf_warning_or_error
);
340 init
= convert_from_reference (exp
);
342 /* If the constructor for the catch parm exits via an exception, we
343 must call terminate. See eh23.C. */
344 if (TYPE_NEEDS_CONSTRUCTING (TREE_TYPE (decl
)))
346 /* Generate the copy constructor call directly so we can wrap it.
347 See also expand_default_init. */
348 init
= ocp_convert (TREE_TYPE (decl
), init
,
349 CONV_IMPLICIT
|CONV_FORCE_TEMP
, 0,
350 tf_warning_or_error
);
351 /* Force cleanups now to avoid nesting problems with the
352 MUST_NOT_THROW_EXPR. */
353 init
= fold_build_cleanup_point_expr (TREE_TYPE (init
), init
);
354 init
= build_must_not_throw_expr (init
, NULL_TREE
);
357 decl
= pushdecl (decl
);
359 start_decl_1 (decl
, true);
360 cp_finish_decl (decl
, init
, /*init_const_expr_p=*/false, NULL_TREE
,
361 LOOKUP_ONLYCONVERTING
|DIRECT_BIND
);
365 /* Routine to see if exception handling is turned on.
366 DO_WARN is nonzero if we want to inform the user that exception
367 handling is turned off.
369 This is used to ensure that -fexceptions has been specified if the
370 compiler tries to use any exception-specific functions. */
375 if (! flag_exceptions
)
377 static int warned
= 0;
380 error ("exception handling disabled, use %<-fexceptions%> to enable");
388 /* Call this to start a catch block. DECL is the catch parameter. */
391 expand_start_catch_block (tree decl
)
401 if (!is_admissible_throw_operand_or_catch_parameter (decl
, false))
402 decl
= error_mark_node
;
404 type
= prepare_eh_type (TREE_TYPE (decl
));
405 mark_used (eh_type_info (type
));
410 /* Call __cxa_end_catch at the end of processing the exception. */
411 push_eh_cleanup (type
);
413 init
= do_begin_catch ();
415 /* If there's no decl at all, then all we need to do is make sure
416 to tell the runtime that we've begun handling the exception. */
417 if (decl
== NULL
|| decl
== error_mark_node
|| init
== error_mark_node
)
418 finish_expr_stmt (init
);
420 /* If the C++ object needs constructing, we need to do that before
421 calling __cxa_begin_catch, so that std::uncaught_exception gets
422 the right value during the copy constructor. */
423 else if (flag_use_cxa_get_exception_ptr
424 && TYPE_NEEDS_CONSTRUCTING (TREE_TYPE (decl
)))
426 exp
= do_get_exception_ptr ();
427 if (exp
!= error_mark_node
)
428 initialize_handler_parm (decl
, exp
);
429 finish_expr_stmt (init
);
432 /* Otherwise the type uses a bitwise copy, and we don't have to worry
433 about the value of std::uncaught_exception and therefore can do the
434 copy with the return value of __cxa_end_catch instead. */
437 tree init_type
= type
;
439 /* Pointers are passed by values, everything else by reference. */
440 if (!TYPE_PTR_P (type
))
441 init_type
= build_pointer_type (type
);
442 if (init_type
!= TREE_TYPE (init
))
443 init
= build1 (NOP_EXPR
, init_type
, init
);
444 exp
= create_temporary_var (init_type
);
445 cp_finish_decl (exp
, init
, /*init_const_expr=*/false,
446 NULL_TREE
, LOOKUP_ONLYCONVERTING
);
447 DECL_REGISTER (exp
) = 1;
448 initialize_handler_parm (decl
, exp
);
454 /* True if we are in a catch block within a catch block. Assumes that we are
455 in function scope. */
458 in_nested_catch (void)
462 /* Scan through the template parameter scopes. */
463 for (cp_binding_level
*b
= current_binding_level
;
464 b
->kind
!= sk_function_parms
;
466 if (b
->kind
== sk_catch
472 /* Call this to end a catch block. Its responsible for emitting the
473 code to handle jumping back to the correct place, and for emitting
474 the label to jump to if this catch block didn't match. */
477 expand_end_catch_block (void)
482 /* The exception being handled is rethrown if control reaches the end of
483 a handler of the function-try-block of a constructor or destructor. */
484 if (in_function_try_handler
485 && (DECL_CONSTRUCTOR_P (current_function_decl
)
486 || DECL_DESTRUCTOR_P (current_function_decl
))
487 && !in_nested_catch ())
489 tree rethrow
= build_throw (input_location
, NULL_TREE
);
490 /* Disable all warnings for the generated rethrow statement. */
491 suppress_warning (rethrow
);
492 finish_expr_stmt (rethrow
);
497 begin_eh_spec_block (void)
500 location_t spec_location
= DECL_SOURCE_LOCATION (current_function_decl
);
502 /* A noexcept specification (or throw() with -fnothrow-opt) is a
503 MUST_NOT_THROW_EXPR. */
504 if (TYPE_NOEXCEPT_P (TREE_TYPE (current_function_decl
)))
506 r
= build_stmt (spec_location
, MUST_NOT_THROW_EXPR
,
507 NULL_TREE
, NULL_TREE
);
508 TREE_SIDE_EFFECTS (r
) = 1;
511 r
= build_stmt (spec_location
, EH_SPEC_BLOCK
, NULL_TREE
, NULL_TREE
);
513 TREE_OPERAND (r
, 0) = push_stmt_list ();
518 finish_eh_spec_block (tree raw_raises
, tree eh_spec_block
)
522 TREE_OPERAND (eh_spec_block
, 0)
523 = pop_stmt_list (TREE_OPERAND (eh_spec_block
, 0));
525 if (TREE_CODE (eh_spec_block
) == MUST_NOT_THROW_EXPR
)
528 /* Strip cv quals, etc, from the specification types. */
529 for (raises
= NULL_TREE
;
530 raw_raises
&& TREE_VALUE (raw_raises
);
531 raw_raises
= TREE_CHAIN (raw_raises
))
533 tree type
= prepare_eh_type (TREE_VALUE (raw_raises
));
534 tree tinfo
= eh_type_info (type
);
537 raises
= tree_cons (NULL_TREE
, type
, raises
);
540 EH_SPEC_RAISES (eh_spec_block
) = raises
;
543 /* Return a pointer to a buffer for an exception object of type TYPE. */
546 do_allocate_exception (tree type
)
548 if (!allocate_exception_fn
)
549 /* Declare void *__cxa_allocate_exception(size_t) throw(). */
550 allocate_exception_fn
551 = declare_library_fn ("__cxa_allocate_exception",
552 ptr_type_node
, size_type_node
,
553 ECF_NOTHROW
| ECF_MALLOC
| ECF_COLD
, ECF_TM_PURE
);
555 return cp_build_function_call_nary (allocate_exception_fn
,
557 size_in_bytes (type
), NULL_TREE
);
560 /* Call __cxa_free_exception from a cleanup. This is never invoked
561 directly, but see the comment for stabilize_throw_expr. */
564 do_free_exception (tree ptr
)
566 if (!free_exception_fn
)
567 /* Declare void __cxa_free_exception (void *) throw(). */
569 = declare_library_fn ("__cxa_free_exception",
570 void_type_node
, ptr_type_node
,
571 ECF_NOTHROW
| ECF_LEAF
, ECF_TM_PURE
);
573 return cp_build_function_call_nary (free_exception_fn
,
574 tf_warning_or_error
, ptr
, NULL_TREE
);
577 /* Wrap all cleanups for TARGET_EXPRs in MUST_NOT_THROW_EXPR.
578 Called from build_throw via walk_tree_without_duplicates. */
581 wrap_cleanups_r (tree
*tp
, int *walk_subtrees
, void * /*data*/)
586 /* Don't walk into types. */
592 if (TREE_CODE (exp
) != TARGET_EXPR
)
595 cleanup
= TARGET_EXPR_CLEANUP (exp
);
598 cleanup
= build2 (MUST_NOT_THROW_EXPR
, void_type_node
, cleanup
,
600 TARGET_EXPR_CLEANUP (exp
) = cleanup
;
603 /* Keep iterating. */
607 /* Build a throw expression. */
610 build_throw (location_t loc
, tree exp
)
612 if (exp
== error_mark_node
)
615 if (processing_template_decl
)
618 current_function_returns_abnormally
= 1;
619 exp
= build_min (THROW_EXPR
, void_type_node
, exp
);
620 SET_EXPR_LOCATION (exp
, loc
);
624 if (exp
&& null_node_p (exp
))
626 "throwing NULL, which has integral, not pointer type");
628 if (exp
!= NULL_TREE
)
630 if (!is_admissible_throw_operand_or_catch_parameter (exp
, true))
631 return error_mark_node
;
635 return error_mark_node
;
645 tsubst_flags_t complain
= tf_warning_or_error
;
647 /* The CLEANUP_TYPE is the internal type of a destructor. */
650 tree tmp
= build_function_type_list (void_type_node
,
651 ptr_type_node
, NULL_TREE
);
652 cleanup_type
= build_pointer_type (tmp
);
657 tree args
[3] = {ptr_type_node
, ptr_type_node
, cleanup_type
};
659 throw_fn
= declare_library_fn_1 ("__cxa_throw",
660 ECF_NORETURN
| ECF_COLD
,
661 void_type_node
, 3, args
);
662 if (flag_tm
&& throw_fn
!= error_mark_node
)
664 tree itm_fn
= declare_library_fn_1 ("_ITM_cxa_throw",
665 ECF_NORETURN
| ECF_COLD
,
666 void_type_node
, 3, args
);
667 if (itm_fn
!= error_mark_node
)
669 apply_tm_attr (itm_fn
, get_identifier ("transaction_pure"));
670 record_tm_replacement (throw_fn
, itm_fn
);
677 A throw-expression initializes a temporary object, the type
678 of which is determined by removing any top-level
679 cv-qualifiers from the static type of the operand of throw
680 and adjusting the type from "array of T" or "function return
681 T" to "pointer to T" or "pointer to function returning T"
683 temp_type
= is_bitfield_expr_with_lowered_type (exp
);
685 temp_type
= cv_unqualified (type_decays_to (TREE_TYPE (exp
)));
687 /* OK, this is kind of wacky. The standard says that we call
688 terminate when the exception handling mechanism, after
689 completing evaluation of the expression to be thrown but
690 before the exception is caught (_except.throw_), calls a
691 user function that exits via an uncaught exception.
693 So we have to protect the actual initialization of the
694 exception object with terminate(), but evaluate the
695 expression first. Since there could be temps in the
696 expression, we need to handle that, too. We also expand
697 the call to __cxa_allocate_exception first (which doesn't
698 matter, since it can't throw). */
700 /* Allocate the space for the exception. */
701 allocate_expr
= do_allocate_exception (temp_type
);
702 if (allocate_expr
== error_mark_node
)
703 return error_mark_node
;
704 allocate_expr
= get_target_expr (allocate_expr
);
705 ptr
= TARGET_EXPR_SLOT (allocate_expr
);
706 TARGET_EXPR_CLEANUP (allocate_expr
) = do_free_exception (ptr
);
707 CLEANUP_EH_ONLY (allocate_expr
) = 1;
709 object
= build_nop (build_pointer_type (temp_type
), ptr
);
710 object
= cp_build_fold_indirect_ref (object
);
712 /* And initialize the exception object. */
713 if (CLASS_TYPE_P (temp_type
))
715 int flags
= LOOKUP_NORMAL
| LOOKUP_ONLYCONVERTING
;
716 bool converted
= false;
717 location_t exp_loc
= cp_expr_loc_or_loc (exp
, loc
);
719 /* Under C++0x [12.8/16 class.copy], a thrown lvalue is sometimes
720 treated as an rvalue for the purposes of overload resolution
721 to favor move constructors over copy constructors. */
722 if (tree moved
= treat_lvalue_as_rvalue_p (exp
, /*return*/false))
723 /* In C++20 we treat the return value as an rvalue that
724 can bind to lvalue refs. In C++23, such an expression is just
728 /* Call the copy constructor. */
731 releasing_vec
exp_vec (make_tree_vector_single (exp
));
732 exp
= (build_special_member_call
733 (object
, complete_ctor_identifier
, &exp_vec
,
734 TREE_TYPE (object
), flags
, tf_warning_or_error
));
737 if (exp
== error_mark_node
)
739 inform (exp_loc
, " in thrown expression");
740 return error_mark_node
;
745 tree tmp
= decay_conversion (exp
, tf_warning_or_error
);
746 if (tmp
== error_mark_node
)
747 return error_mark_node
;
748 exp
= cp_build_init_expr (object
, tmp
);
751 /* Mark any cleanups from the initialization as MUST_NOT_THROW, since
752 they are run after the exception object is initialized. */
753 cp_walk_tree_without_duplicates (&exp
, wrap_cleanups_r
, 0);
755 /* Prepend the allocation. */
756 exp
= build2 (COMPOUND_EXPR
, TREE_TYPE (exp
), allocate_expr
, exp
);
758 /* Force all the cleanups to be evaluated here so that we don't have
759 to do them during unwinding. */
760 exp
= build1 (CLEANUP_POINT_EXPR
, void_type_node
, exp
);
762 throw_type
= build_eh_type_type (prepare_eh_type (TREE_TYPE (object
)));
765 if (type_build_dtor_call (TREE_TYPE (object
)))
767 tree binfo
= TYPE_BINFO (TREE_TYPE (object
));
768 tree dtor_fn
= lookup_fnfields (binfo
,
769 complete_dtor_identifier
, 0,
770 tf_warning_or_error
);
771 dtor_fn
= BASELINK_FUNCTIONS (dtor_fn
);
772 if (!mark_used (dtor_fn
)
773 || !perform_or_defer_access_check (binfo
, dtor_fn
,
775 return error_mark_node
;
776 if (TYPE_HAS_NONTRIVIAL_DESTRUCTOR (TREE_TYPE (object
)))
778 cxx_mark_addressable (dtor_fn
);
779 /* Pretend it's a normal function. */
780 cleanup
= build1 (ADDR_EXPR
, cleanup_type
, dtor_fn
);
783 if (cleanup
== NULL_TREE
)
784 cleanup
= build_int_cst (cleanup_type
, 0);
786 /* ??? Indicate that this function call throws throw_type. */
787 tree tmp
= cp_build_function_call_nary (throw_fn
, tf_warning_or_error
,
788 ptr
, throw_type
, cleanup
,
791 /* Tack on the initialization stuff. */
792 exp
= build2 (COMPOUND_EXPR
, TREE_TYPE (tmp
), exp
, tmp
);
796 /* Rethrow current exception. */
799 rethrow_fn
= declare_library_fn_1 ("__cxa_rethrow",
800 ECF_NORETURN
| ECF_COLD
,
801 void_type_node
, 0, NULL
);
802 if (flag_tm
&& rethrow_fn
!= error_mark_node
)
803 apply_tm_attr (rethrow_fn
, get_identifier ("transaction_pure"));
806 /* ??? Indicate that this function call allows exceptions of the type
807 of the enclosing catch block (if known). */
808 exp
= cp_build_function_call_vec (rethrow_fn
, NULL
, tf_warning_or_error
);
811 exp
= build1_loc (loc
, THROW_EXPR
, void_type_node
, exp
);
816 /* Make sure TYPE is complete, pointer to complete, reference to
817 complete, or pointer to cv void. Issue diagnostic on failure.
818 Return the zero on failure and nonzero on success. FROM can be
819 the expr or decl from whence TYPE came, if available. */
822 complete_ptr_ref_or_void_ptr_p (tree type
, tree from
)
826 /* Check complete. */
827 type
= complete_type_or_else (type
, from
);
831 /* Or a pointer or ref to one, or cv void *. */
832 is_ptr
= TYPE_PTR_P (type
);
833 if (is_ptr
|| TYPE_REF_P (type
))
835 tree core
= TREE_TYPE (type
);
837 if (is_ptr
&& VOID_TYPE_P (core
))
839 else if (!complete_type_or_else (core
, from
))
845 /* If IS_THROW is true return truth-value if T is an expression admissible
846 in throw-expression, i.e. if it is not of incomplete type or a pointer/
847 reference to such a type or of an abstract class type.
848 If IS_THROW is false, likewise for a catch parameter, same requirements
849 for its type plus rvalue reference type is also not admissible. */
852 is_admissible_throw_operand_or_catch_parameter (tree t
, bool is_throw
)
854 tree expr
= is_throw
? t
: NULL_TREE
;
855 tree type
= TREE_TYPE (t
);
857 /* C++11 [except.handle] The exception-declaration shall not denote
858 an incomplete type, an abstract class type, or an rvalue reference
861 /* 15.1/4 [...] The type of the throw-expression shall not be an
862 incomplete type, or a pointer or a reference to an incomplete
863 type, other than void*, const void*, volatile void*, or
864 const volatile void*. Except for these restriction and the
865 restrictions on type matching mentioned in 15.3, the operand
866 of throw is treated exactly as a function argument in a call
867 (5.2.2) or the operand of a return statement. */
868 if (!complete_ptr_ref_or_void_ptr_p (type
, expr
))
871 tree nonref_type
= non_reference (type
);
872 if (!verify_type_context (input_location
, TCTX_EXCEPTIONS
, nonref_type
))
875 /* 10.4/3 An abstract class shall not be used as a parameter type,
876 as a function return type or as type of an explicit
878 else if (abstract_virtuals_error (is_throw
? ACU_THROW
: ACU_CATCH
, type
))
882 && TYPE_REF_IS_RVALUE (type
))
884 error ("cannot declare %<catch%> parameter to be of rvalue "
885 "reference type %qT", type
);
888 else if (variably_modified_type_p (type
, NULL_TREE
))
891 error_at (cp_expr_loc_or_input_loc (expr
),
892 "cannot throw expression of type %qT because it involves "
893 "types of variable size", type
);
895 error ("cannot catch type %qT because it involves types of "
896 "variable size", type
);
903 /* Returns nonzero if FN is a declaration of a standard C library
904 function which is known not to throw.
906 [lib.res.on.exception.handling]: None of the functions from the
907 Standard C library shall report an error by throwing an
908 exception, unless it calls a program-supplied function that
909 throws an exception. */
914 nothrow_libfn_p (const_tree fn
)
919 && DECL_EXTERNAL (fn
)
920 && DECL_NAMESPACE_SCOPE_P (fn
)
921 && DECL_EXTERN_C_P (fn
))
924 /* Can't be a C library function. */
927 /* Being a C library function, DECL_ASSEMBLER_NAME == DECL_NAME
928 unless the system headers are playing rename tricks, and if
929 they are, we don't want to be confused by them. */
931 const struct libc_name_struct
*s
932 = libc_name::libc_name_p (IDENTIFIER_POINTER (id
), IDENTIFIER_LENGTH (id
));
938 case 99: return !flag_iso
|| flag_isoc99
;
939 case 11: return !flag_iso
|| flag_isoc11
;
940 default: gcc_unreachable ();
944 /* Returns nonzero if an exception of type FROM will be caught by a
945 handler for type TO, as per [except.handle]. */
948 can_convert_eh (tree to
, tree from
)
950 to
= non_reference (to
);
951 from
= non_reference (from
);
953 if (same_type_ignoring_top_level_qualifiers_p (to
, from
))
956 if (TYPE_PTR_P (to
) && TYPE_PTR_P (from
))
959 from
= TREE_TYPE (from
);
961 if (! at_least_as_qualified_p (to
, from
))
964 if (VOID_TYPE_P (to
))
967 /* Else fall through. */
970 if (CLASS_TYPE_P (to
) && CLASS_TYPE_P (from
)
971 && publicly_uniquely_derived_p (to
, from
))
977 /* Check whether any of the handlers in I are shadowed by another handler
978 accepting TYPE. Note that the shadowing may not be complete; even if
979 an exception of type B would be caught by a handler for A, there could
980 be a derived class C for which A is an ambiguous base but B is not, so
981 the handler for B would catch an exception of type C. */
984 check_handlers_1 (tree master
, tree_stmt_iterator i
)
986 tree type
= TREE_TYPE (master
);
988 for (; !tsi_end_p (i
); tsi_next (&i
))
990 tree handler
= tsi_stmt (i
);
991 if (TREE_TYPE (handler
) && can_convert_eh (type
, TREE_TYPE (handler
)))
993 auto_diagnostic_group d
;
994 if (warning_at (EXPR_LOCATION (handler
), OPT_Wexceptions
,
995 "exception of type %qT will be caught by earlier "
996 "handler", TREE_TYPE (handler
)))
997 inform (EXPR_LOCATION (master
), "for type %qT", type
);
1003 /* Given a STATEMENT_LIST of HANDLERs, make sure that they're OK. */
1006 check_handlers (tree handlers
)
1008 tree_stmt_iterator i
;
1010 /* If we don't have a STATEMENT_LIST, then we've just got one
1011 handler, and thus nothing to warn about. */
1012 if (TREE_CODE (handlers
) != STATEMENT_LIST
)
1015 i
= tsi_start (handlers
);
1019 tree handler
= tsi_stmt (i
);
1022 /* No more handlers; nothing to shadow. */
1025 if (TREE_TYPE (handler
) == NULL_TREE
)
1026 permerror (EXPR_LOCATION (handler
), "%<...%>"
1027 " handler must be the last handler for its try block");
1029 check_handlers_1 (handler
, i
);
1033 /* walk_tree helper for finish_noexcept_expr. Returns non-null if the
1034 expression *TP causes the noexcept operator to evaluate to false.
1036 5.3.7 [expr.noexcept]: The result of the noexcept operator is false if
1037 in a potentially-evaluated context the expression would contain
1038 * a potentially evaluated call to a function, member function,
1039 function pointer, or member function pointer that does not have a
1040 non-throwing exception-specification (15.4),
1041 * a potentially evaluated throw-expression (15.1),
1042 * a potentially evaluated dynamic_cast expression dynamic_cast<T>(v),
1043 where T is a reference type, that requires a run-time check (5.2.7), or
1044 * a potentially evaluated typeid expression (5.2.8) applied to a glvalue
1045 expression whose type is a polymorphic class type (10.3). */
1048 check_noexcept_r (tree
*tp
, int *walk_subtrees
, void *)
1051 enum tree_code code
= TREE_CODE (t
);
1053 if (unevaluated_p (code
))
1054 *walk_subtrees
= false;
1055 else if ((code
== CALL_EXPR
&& CALL_EXPR_FN (t
))
1056 || code
== AGGR_INIT_EXPR
)
1058 /* We can only use the exception specification of the called function
1059 for determining the value of a noexcept expression; we can't use
1060 TREE_NOTHROW, as it might have a different value in another
1061 translation unit, creating ODR problems.
1063 We could use TREE_NOTHROW (t) for !TREE_PUBLIC fns, though... */
1064 tree fn
= cp_get_callee (t
);
1065 if (concept_check_p (fn
))
1067 tree type
= TREE_TYPE (fn
);
1068 gcc_assert (INDIRECT_TYPE_P (type
));
1069 type
= TREE_TYPE (type
);
1072 if (TREE_CODE (fn
) == ADDR_EXPR
)
1073 fn
= TREE_OPERAND (fn
, 0);
1074 if (TREE_CODE (fn
) == FUNCTION_DECL
)
1076 /* We do use TREE_NOTHROW for ABI internals like __dynamic_cast,
1077 and for C library functions known not to throw. */
1078 if (DECL_EXTERN_C_P (fn
)
1079 && (DECL_ARTIFICIAL (fn
)
1080 || nothrow_libfn_p (fn
)))
1081 return TREE_NOTHROW (fn
) ? NULL_TREE
: fn
;
1082 /* We used to treat a call to a constexpr function as noexcept if
1083 the call was a constant expression (CWG 1129). This has changed
1084 in P0003 whereby noexcept has no special rule for constant
1085 expressions anymore. Since the current behavior is important for
1086 certain library functionality, we treat this as a DR, therefore
1087 adjusting the behavior for C++11 and C++14. Previously, we had
1088 to evaluate the noexcept-specifier's operand here, but that could
1089 cause instantiations that would fail. */
1091 if (!TYPE_NOTHROW_P (type
))
1098 /* If a function that causes a noexcept-expression to be false isn't
1099 defined yet, remember it and check it for TREE_NOTHROW again at EOF. */
1101 struct GTY(()) pending_noexcept
{
1105 static GTY(()) vec
<pending_noexcept
, va_gc
> *pending_noexcept_checks
;
1107 /* FN is a FUNCTION_DECL that caused a noexcept-expr to be false. Warn if
1110 TODO: Consider extending -Wnoexcept to do something like walk_subtrees in the
1111 case of a defaulted function that obtained a noexcept(false) spec. */
1114 maybe_noexcept_warning (tree fn
)
1116 if (TREE_NOTHROW (fn
)
1117 && (!DECL_IN_SYSTEM_HEADER (fn
)
1118 || global_dc
->dc_warn_system_headers
))
1120 auto s
= make_temp_override (global_dc
->dc_warn_system_headers
, true);
1121 auto_diagnostic_group d
;
1122 if (warning (OPT_Wnoexcept
, "noexcept-expression evaluates to %<false%> "
1123 "because of a call to %qD", fn
))
1124 inform (DECL_SOURCE_LOCATION (fn
),
1125 "but %qD does not throw; perhaps "
1126 "it should be declared %<noexcept%>", fn
);
1130 /* Check any functions that weren't defined earlier when they caused a
1131 noexcept expression to evaluate to false. */
1134 perform_deferred_noexcept_checks (void)
1137 pending_noexcept
*p
;
1138 location_t saved_loc
= input_location
;
1139 FOR_EACH_VEC_SAFE_ELT (pending_noexcept_checks
, i
, p
)
1141 input_location
= p
->loc
;
1142 maybe_noexcept_warning (p
->fn
);
1144 input_location
= saved_loc
;
1147 /* Evaluate noexcept ( EXPR ). */
1150 finish_noexcept_expr (tree expr
, tsubst_flags_t complain
)
1152 if (expr
== error_mark_node
)
1153 return error_mark_node
;
1155 if (processing_template_decl
)
1156 return build_min (NOEXCEPT_EXPR
, boolean_type_node
, expr
);
1158 return (expr_noexcept_p (expr
, complain
)
1159 ? boolean_true_node
: boolean_false_node
);
1162 /* Returns whether EXPR is noexcept, possibly warning if allowed by
1166 expr_noexcept_p (tree expr
, tsubst_flags_t complain
)
1170 if (expr
== error_mark_node
)
1173 fn
= cp_walk_tree_without_duplicates (&expr
, check_noexcept_r
, 0);
1176 if ((complain
& tf_warning
) && warn_noexcept
1177 && TREE_CODE (fn
) == FUNCTION_DECL
)
1179 if (!DECL_INITIAL (fn
))
1181 /* Not defined yet; check again at EOF. */
1182 pending_noexcept p
= {fn
, input_location
};
1183 vec_safe_push (pending_noexcept_checks
, p
);
1186 maybe_noexcept_warning (fn
);
1194 /* Return true iff SPEC is throw() or noexcept(true). */
1197 nothrow_spec_p (const_tree spec
)
1199 gcc_assert (!DEFERRED_NOEXCEPT_SPEC_P (spec
));
1201 if (spec
== empty_except_spec
1202 || spec
== noexcept_true_spec
)
1206 || TREE_VALUE (spec
)
1207 || spec
== noexcept_false_spec
1208 || TREE_PURPOSE (spec
) == error_mark_node
1209 || UNPARSED_NOEXCEPT_SPEC_P (spec
)
1210 || processing_template_decl
);
1215 /* For FUNCTION_TYPE or METHOD_TYPE, true if NODE is noexcept. This is the
1216 case for things declared noexcept(true) and, with -fnothrow-opt, for
1217 throw() functions. */
1220 type_noexcept_p (const_tree type
)
1222 tree spec
= TYPE_RAISES_EXCEPTIONS (type
);
1223 gcc_assert (!DEFERRED_NOEXCEPT_SPEC_P (spec
));
1224 if (flag_nothrow_opt
)
1225 return nothrow_spec_p (spec
);
1227 return spec
== noexcept_true_spec
;
1230 /* For FUNCTION_TYPE or METHOD_TYPE, true if NODE can throw any type,
1231 i.e. no exception-specification or noexcept(false). */
1234 type_throw_all_p (const_tree type
)
1236 tree spec
= TYPE_RAISES_EXCEPTIONS (type
);
1237 gcc_assert (!DEFERRED_NOEXCEPT_SPEC_P (spec
));
1238 return spec
== NULL_TREE
|| spec
== noexcept_false_spec
;
1241 /* Create a representation of the noexcept-specification with
1242 constant-expression of EXPR. COMPLAIN is as for tsubst. */
1245 build_noexcept_spec (tree expr
, tsubst_flags_t complain
)
1247 if (check_for_bare_parameter_packs (expr
))
1248 return error_mark_node
;
1249 if (TREE_CODE (expr
) != DEFERRED_NOEXCEPT
1250 && !instantiation_dependent_expression_p (expr
))
1252 expr
= build_converted_constant_bool_expr (expr
, complain
);
1253 expr
= instantiate_non_dependent_expr (expr
, complain
);
1254 expr
= cxx_constant_value (expr
, complain
);
1256 if (TREE_CODE (expr
) == INTEGER_CST
)
1258 if (operand_equal_p (expr
, boolean_true_node
, 0))
1259 return noexcept_true_spec
;
1262 gcc_checking_assert (operand_equal_p (expr
, boolean_false_node
, 0));
1263 return noexcept_false_spec
;
1266 else if (expr
== error_mark_node
)
1267 return error_mark_node
;
1270 gcc_assert (processing_template_decl
1271 || TREE_CODE (expr
) == DEFERRED_NOEXCEPT
);
1272 if (TREE_CODE (expr
) != DEFERRED_NOEXCEPT
)
1273 /* Avoid problems with a function type built with a dependent typedef
1274 being reused in another scope (c++/84045). */
1275 expr
= strip_typedefs_expr (expr
);
1276 return build_tree_list (expr
, NULL_TREE
);
1280 /* If the current function has a cleanup that might throw, and the return value
1281 has a non-trivial destructor, return a MODIFY_EXPR to set
1282 current_retval_sentinel so that we know that the return value needs to be
1283 destroyed on throw. Do the same if the current function might use the
1284 named return value optimization, so we don't destroy it on return.
1285 Otherwise, returns NULL_TREE. */
1288 maybe_set_retval_sentinel ()
1290 if (processing_template_decl
)
1292 tree retval
= DECL_RESULT (current_function_decl
);
1293 if (!TYPE_HAS_NONTRIVIAL_DESTRUCTOR (TREE_TYPE (retval
)))
1295 if (!cp_function_chain
->throwing_cleanup
1296 && (current_function_return_value
== error_mark_node
1297 || current_function_return_value
== NULL_TREE
))
1300 if (!current_retval_sentinel
)
1302 /* Just create the temporary now, maybe_splice_retval_cleanup
1303 will do the rest. */
1304 current_retval_sentinel
= create_temporary_var (boolean_type_node
);
1305 DECL_INITIAL (current_retval_sentinel
) = boolean_false_node
;
1306 pushdecl_outermost_localscope (current_retval_sentinel
);
1309 return build2 (MODIFY_EXPR
, boolean_type_node
,
1310 current_retval_sentinel
, boolean_true_node
);
1313 /* COMPOUND_STMT is the STATEMENT_LIST for some block. If COMPOUND_STMT is the
1314 current function body or a try block, and current_retval_sentinel was set in
1315 this function, wrap the block in a CLEANUP_STMT to destroy the return value
1319 maybe_splice_retval_cleanup (tree compound_stmt
, bool is_try
)
1321 if (!current_function_decl
|| !cfun
1322 || DECL_CONSTRUCTOR_P (current_function_decl
)
1323 || DECL_DESTRUCTOR_P (current_function_decl
)
1324 || !current_retval_sentinel
)
1327 /* if we need a cleanup for the return value, add it in at the same level as
1328 pushdecl_outermost_localscope. And also in try blocks. */
1329 cp_binding_level
*b
= current_binding_level
;
1330 const bool function_body
= b
->kind
== sk_function_parms
;
1332 if (function_body
|| is_try
)
1334 location_t loc
= DECL_SOURCE_LOCATION (current_function_decl
);
1335 tree_stmt_iterator iter
= tsi_start (compound_stmt
);
1336 tree retval
= DECL_RESULT (current_function_decl
);
1340 /* Add a DECL_EXPR for current_retval_sentinel. */
1341 tree decl_expr
= build_stmt (loc
, DECL_EXPR
, current_retval_sentinel
);
1342 tsi_link_before (&iter
, decl_expr
, TSI_SAME_STMT
);
1345 if (!cp_function_chain
->throwing_cleanup
)
1346 /* We're only using the sentinel for an NRV. */
1349 /* Skip past other decls, they can't contain a return. */
1350 while (TREE_CODE (tsi_stmt (iter
)) == DECL_EXPR
)
1352 gcc_assert (!tsi_end_p (iter
));
1354 /* Wrap the rest of the STATEMENT_LIST in a CLEANUP_STMT. */
1355 tree stmts
= NULL_TREE
;
1356 while (!tsi_end_p (iter
))
1358 append_to_statement_list_force (tsi_stmt (iter
), &stmts
);
1361 tree dtor
= build_cleanup (retval
);
1362 tree cond
= build3 (COND_EXPR
, void_type_node
, current_retval_sentinel
,
1364 tree cleanup
= build_stmt (loc
, CLEANUP_STMT
,
1365 stmts
, cond
, retval
);
1366 CLEANUP_EH_ONLY (cleanup
) = true;
1367 append_to_statement_list_force (cleanup
, &compound_stmt
);
1371 #include "gt-cp-except.h"