1 /* Handle exceptional things in C++.
2 Copyright (C) 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
3 2000, 2001, 2002, 2003, 2004, 2005, 2007, 2008, 2009, 2010
4 Free Software Foundation, Inc.
5 Contributed by Michael Tiemann <tiemann@cygnus.com>
6 Rewritten by Mike Stump <mrs@cygnus.com>, based upon an
7 initial re-implementation courtesy Tad Hunt.
9 This file is part of GCC.
11 GCC is free software; you can redistribute it and/or modify
12 it under the terms of the GNU General Public License as published by
13 the Free Software Foundation; either version 3, or (at your option)
16 GCC is distributed in the hope that it will be useful,
17 but WITHOUT ANY WARRANTY; without even the implied warranty of
18 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 GNU General Public License for more details.
21 You should have received a copy of the GNU General Public License
22 along with GCC; see the file COPYING3. If not see
23 <http://www.gnu.org/licenses/>. */
28 #include "coretypes.h"
34 #include "tree-inline.h"
35 #include "tree-iterator.h"
39 static void push_eh_cleanup (tree);
40 static tree prepare_eh_type (tree);
41 static tree do_begin_catch (void);
42 static int dtor_nothrow (tree);
43 static tree do_end_catch (tree);
44 static bool decl_is_java_type (tree decl, int err);
45 static void initialize_handler_parm (tree, tree);
46 static tree do_allocate_exception (tree);
47 static tree wrap_cleanups_r (tree *, int *, void *);
48 static int complete_ptr_ref_or_void_ptr_p (tree, tree);
49 static bool is_admissible_throw_operand (tree);
50 static int can_convert_eh (tree, tree);
52 /* Sets up all the global eh stuff that needs to be initialized at the
53 start of compilation. */
56 init_exception_processing (void)
60 /* void std::terminate (); */
61 push_namespace (std_identifier);
62 tmp = build_function_type_list (void_type_node, NULL_TREE);
63 terminate_node = build_cp_library_fn_ptr ("terminate", tmp);
64 TREE_THIS_VOLATILE (terminate_node) = 1;
65 TREE_NOTHROW (terminate_node) = 1;
68 /* void __cxa_call_unexpected(void *); */
69 tmp = build_function_type_list (void_type_node, ptr_type_node, NULL_TREE);
71 = push_throw_library_fn (get_identifier ("__cxa_call_unexpected"), tmp);
74 /* Returns an expression to be executed if an unhandled exception is
75 propagated out of a cleanup region. */
78 cp_protect_cleanup_actions (void)
82 When the destruction of an object during stack unwinding exits
83 using an exception ... void terminate(); is called. */
84 return terminate_node;
88 prepare_eh_type (tree type)
90 if (type == NULL_TREE)
92 if (type == error_mark_node)
93 return error_mark_node;
95 /* peel back references, so they match. */
96 type = non_reference (type);
98 /* Peel off cv qualifiers. */
99 type = TYPE_MAIN_VARIANT (type);
101 /* Functions and arrays decay to pointers. */
102 type = type_decays_to (type);
107 /* Return the type info for TYPE as used by EH machinery. */
109 eh_type_info (tree type)
113 if (type == NULL_TREE || type == error_mark_node)
116 if (decl_is_java_type (type, 0))
117 exp = build_java_class_ref (TREE_TYPE (type));
119 exp = get_tinfo_decl (type);
124 /* Build the address of a typeinfo decl for use in the runtime
125 matching field of the exception model. */
128 build_eh_type_type (tree type)
130 tree exp = eh_type_info (type);
137 return convert (ptr_type_node, build_address (exp));
143 return build_call_n (built_in_decls [BUILT_IN_EH_POINTER],
144 1, integer_zero_node);
147 /* Declare a function NAME, returning RETURN_TYPE, taking a single
148 parameter PARM_TYPE, with an empty exception specification.
150 Note that the C++ ABI document does not have a throw-specifier on
151 the routines declared below via this function. The declarations
152 are consistent with the actual implementations in libsupc++. */
155 declare_nothrow_library_fn (tree name, tree return_type, tree parm_type)
157 return push_library_fn (name, build_function_type_list (return_type,
163 /* Build up a call to __cxa_get_exception_ptr so that we can build a
164 copy constructor for the thrown object. */
167 do_get_exception_ptr (void)
171 fn = get_identifier ("__cxa_get_exception_ptr");
172 if (!get_global_value_if_present (fn, &fn))
174 /* Declare void* __cxa_get_exception_ptr (void *) throw(). */
175 fn = declare_nothrow_library_fn (fn, ptr_type_node, ptr_type_node);
178 return cp_build_function_call_nary (fn, tf_warning_or_error,
179 build_exc_ptr (), NULL_TREE);
182 /* Build up a call to __cxa_begin_catch, to tell the runtime that the
183 exception has been handled. */
186 do_begin_catch (void)
190 fn = get_identifier ("__cxa_begin_catch");
191 if (!get_global_value_if_present (fn, &fn))
193 /* Declare void* __cxa_begin_catch (void *) throw(). */
194 fn = declare_nothrow_library_fn (fn, ptr_type_node, ptr_type_node);
197 return cp_build_function_call_nary (fn, tf_warning_or_error,
198 build_exc_ptr (), NULL_TREE);
201 /* Returns nonzero if cleaning up an exception of type TYPE (which can be
202 NULL_TREE for a ... handler) will not throw an exception. */
205 dtor_nothrow (tree type)
207 if (type == NULL_TREE || type == error_mark_node)
210 if (TYPE_HAS_TRIVIAL_DESTRUCTOR (type))
213 if (CLASSTYPE_LAZY_DESTRUCTOR (type))
214 lazily_declare_fn (sfk_destructor, type);
216 return TREE_NOTHROW (CLASSTYPE_DESTRUCTORS (type));
219 /* Build up a call to __cxa_end_catch, to destroy the exception object
220 for the current catch block if no others are currently using it. */
223 do_end_catch (tree type)
227 fn = get_identifier ("__cxa_end_catch");
228 if (!get_global_value_if_present (fn, &fn))
230 /* Declare void __cxa_end_catch (). */
231 fn = push_void_library_fn (fn, void_list_node);
232 /* This can throw if the destructor for the exception throws. */
233 TREE_NOTHROW (fn) = 0;
236 cleanup = cp_build_function_call_vec (fn, NULL, tf_warning_or_error);
237 TREE_NOTHROW (cleanup) = dtor_nothrow (type);
242 /* This routine creates the cleanup for the current exception. */
245 push_eh_cleanup (tree type)
247 finish_decl_cleanup (NULL_TREE, do_end_catch (type));
250 /* Return nonzero value if DECL is a Java type suitable for catch or
254 decl_is_java_type (tree decl, int err)
256 bool r = (TREE_CODE (decl) == POINTER_TYPE
257 && TREE_CODE (TREE_TYPE (decl)) == RECORD_TYPE
258 && TYPE_FOR_JAVA (TREE_TYPE (decl)));
262 if (TREE_CODE (decl) == REFERENCE_TYPE
263 && TREE_CODE (TREE_TYPE (decl)) == RECORD_TYPE
264 && TYPE_FOR_JAVA (TREE_TYPE (decl)))
266 /* Can't throw a reference. */
267 error ("type %qT is disallowed in Java %<throw%> or %<catch%>",
274 = IDENTIFIER_GLOBAL_VALUE (get_identifier ("jthrowable"));
276 if (jthrow_node == NULL_TREE)
278 ("call to Java %<catch%> or %<throw%> with %<jthrowable%> undefined");
280 jthrow_node = TREE_TYPE (TREE_TYPE (jthrow_node));
282 if (! DERIVED_FROM_P (jthrow_node, TREE_TYPE (decl)))
284 /* Thrown object must be a Throwable. */
285 error ("type %qT is not derived from %<java::lang::Throwable%>",
294 /* Select the personality routine to be used for exception handling,
295 or issue an error if we need two different ones in the same
297 ??? At present DECL_FUNCTION_PERSONALITY is set via
298 LANG_HOOKS_EH_PERSONALITY. Should it be done here instead? */
300 choose_personality_routine (enum languages lang)
315 if (lang != lang_cplusplus)
320 if (lang != lang_java)
325 ; /* Proceed to language selection. */
336 terminate_node = built_in_decls [BUILT_IN_ABORT];
337 pragma_java_exceptions = true;
346 error ("mixing C++ and Java catches in a single translation unit");
350 /* Initialize the catch parameter DECL. */
353 initialize_handler_parm (tree decl, tree exp)
358 /* Make sure we mark the catch param as used, otherwise we'll get a
359 warning about an unused ((anonymous)). */
360 TREE_USED (decl) = 1;
361 DECL_READ_P (decl) = 1;
363 /* Figure out the type that the initializer is. Pointers are returned
364 adjusted by value from __cxa_begin_catch. Others are returned by
366 init_type = TREE_TYPE (decl);
367 if (!POINTER_TYPE_P (init_type))
368 init_type = build_reference_type (init_type);
370 choose_personality_routine (decl_is_java_type (init_type, 0)
371 ? lang_java : lang_cplusplus);
373 /* Since pointers are passed by value, initialize a reference to
374 pointer catch parm with the address of the temporary. */
375 if (TREE_CODE (init_type) == REFERENCE_TYPE
376 && TYPE_PTR_P (TREE_TYPE (init_type)))
377 exp = cp_build_addr_expr (exp, tf_warning_or_error);
379 exp = ocp_convert (init_type, exp, CONV_IMPLICIT|CONV_FORCE_TEMP, 0);
381 init = convert_from_reference (exp);
383 /* If the constructor for the catch parm exits via an exception, we
384 must call terminate. See eh23.C. */
385 if (TYPE_NEEDS_CONSTRUCTING (TREE_TYPE (decl)))
387 /* Generate the copy constructor call directly so we can wrap it.
388 See also expand_default_init. */
389 init = ocp_convert (TREE_TYPE (decl), init,
390 CONV_IMPLICIT|CONV_FORCE_TEMP, 0);
391 /* Force cleanups now to avoid nesting problems with the
392 MUST_NOT_THROW_EXPR. */
393 init = fold_build_cleanup_point_expr (TREE_TYPE (init), init);
394 init = build1 (MUST_NOT_THROW_EXPR, TREE_TYPE (init), init);
397 decl = pushdecl (decl);
399 start_decl_1 (decl, true);
400 cp_finish_decl (decl, init, /*init_const_expr_p=*/false, NULL_TREE,
401 LOOKUP_ONLYCONVERTING|DIRECT_BIND);
405 /* Routine to see if exception handling is turned on.
406 DO_WARN is nonzero if we want to inform the user that exception
407 handling is turned off.
409 This is used to ensure that -fexceptions has been specified if the
410 compiler tries to use any exception-specific functions. */
415 if (! flag_exceptions)
417 static int warned = 0;
420 error ("exception handling disabled, use -fexceptions to enable");
428 /* Call this to start a catch block. DECL is the catch parameter. */
431 expand_start_catch_block (tree decl)
439 /* Make sure this declaration is reasonable. */
440 if (decl && !complete_ptr_ref_or_void_ptr_p (TREE_TYPE (decl), NULL_TREE))
441 decl = error_mark_node;
444 type = prepare_eh_type (TREE_TYPE (decl));
448 if (decl && decl_is_java_type (type, 1))
450 /* Java only passes object via pointer and doesn't require
451 adjusting. The java object is immediately before the
452 generic exception header. */
453 exp = build_exc_ptr ();
454 exp = build1 (NOP_EXPR, build_pointer_type (type), exp);
455 exp = fold_build_pointer_plus (exp,
456 fold_build1_loc (input_location,
457 NEGATE_EXPR, sizetype,
458 TYPE_SIZE_UNIT (TREE_TYPE (exp))));
459 exp = cp_build_indirect_ref (exp, RO_NULL, tf_warning_or_error);
460 initialize_handler_parm (decl, exp);
464 /* Call __cxa_end_catch at the end of processing the exception. */
465 push_eh_cleanup (type);
467 init = do_begin_catch ();
469 /* If there's no decl at all, then all we need to do is make sure
470 to tell the runtime that we've begun handling the exception. */
471 if (decl == NULL || decl == error_mark_node || init == error_mark_node)
472 finish_expr_stmt (init);
474 /* If the C++ object needs constructing, we need to do that before
475 calling __cxa_begin_catch, so that std::uncaught_exception gets
476 the right value during the copy constructor. */
477 else if (flag_use_cxa_get_exception_ptr
478 && TYPE_NEEDS_CONSTRUCTING (TREE_TYPE (decl)))
480 exp = do_get_exception_ptr ();
481 initialize_handler_parm (decl, exp);
482 finish_expr_stmt (init);
485 /* Otherwise the type uses a bitwise copy, and we don't have to worry
486 about the value of std::uncaught_exception and therefore can do the
487 copy with the return value of __cxa_end_catch instead. */
490 tree init_type = type;
492 /* Pointers are passed by values, everything else by reference. */
493 if (!TYPE_PTR_P (type))
494 init_type = build_pointer_type (type);
495 if (init_type != TREE_TYPE (init))
496 init = build1 (NOP_EXPR, init_type, init);
497 exp = create_temporary_var (init_type);
498 DECL_REGISTER (exp) = 1;
499 cp_finish_decl (exp, init, /*init_const_expr=*/false,
500 NULL_TREE, LOOKUP_ONLYCONVERTING);
501 initialize_handler_parm (decl, exp);
508 /* Call this to end a catch block. Its responsible for emitting the
509 code to handle jumping back to the correct place, and for emitting
510 the label to jump to if this catch block didn't match. */
513 expand_end_catch_block (void)
518 /* The exception being handled is rethrown if control reaches the end of
519 a handler of the function-try-block of a constructor or destructor. */
520 if (in_function_try_handler
521 && (DECL_CONSTRUCTOR_P (current_function_decl)
522 || DECL_DESTRUCTOR_P (current_function_decl)))
523 finish_expr_stmt (build_throw (NULL_TREE));
527 begin_eh_spec_block (void)
530 location_t spec_location = DECL_SOURCE_LOCATION (current_function_decl);
532 /* A noexcept specification (or throw() with -fnothrow-opt) is a
533 MUST_NOT_THROW_EXPR. */
534 if (TYPE_NOEXCEPT_P (TREE_TYPE (current_function_decl)))
536 r = build_stmt (spec_location, MUST_NOT_THROW_EXPR, NULL_TREE);
537 TREE_SIDE_EFFECTS (r) = 1;
540 r = build_stmt (spec_location, EH_SPEC_BLOCK, NULL_TREE, NULL_TREE);
542 TREE_OPERAND (r, 0) = push_stmt_list ();
547 finish_eh_spec_block (tree raw_raises, tree eh_spec_block)
551 TREE_OPERAND (eh_spec_block, 0)
552 = pop_stmt_list (TREE_OPERAND (eh_spec_block, 0));
554 if (TREE_CODE (eh_spec_block) == MUST_NOT_THROW_EXPR)
557 /* Strip cv quals, etc, from the specification types. */
558 for (raises = NULL_TREE;
559 raw_raises && TREE_VALUE (raw_raises);
560 raw_raises = TREE_CHAIN (raw_raises))
562 tree type = prepare_eh_type (TREE_VALUE (raw_raises));
563 tree tinfo = eh_type_info (type);
566 raises = tree_cons (NULL_TREE, type, raises);
569 EH_SPEC_RAISES (eh_spec_block) = raises;
572 /* Return a pointer to a buffer for an exception object of type TYPE. */
575 do_allocate_exception (tree type)
579 fn = get_identifier ("__cxa_allocate_exception");
580 if (!get_global_value_if_present (fn, &fn))
582 /* Declare void *__cxa_allocate_exception(size_t) throw(). */
583 fn = declare_nothrow_library_fn (fn, ptr_type_node, size_type_node);
586 return cp_build_function_call_nary (fn, tf_warning_or_error,
587 size_in_bytes (type), NULL_TREE);
590 /* Call __cxa_free_exception from a cleanup. This is never invoked
591 directly, but see the comment for stabilize_throw_expr. */
594 do_free_exception (tree ptr)
598 fn = get_identifier ("__cxa_free_exception");
599 if (!get_global_value_if_present (fn, &fn))
601 /* Declare void __cxa_free_exception (void *) throw(). */
602 fn = declare_nothrow_library_fn (fn, void_type_node, ptr_type_node);
605 return cp_build_function_call_nary (fn, tf_warning_or_error, ptr, NULL_TREE);
608 /* Wrap all cleanups for TARGET_EXPRs in MUST_NOT_THROW_EXPR.
609 Called from build_throw via walk_tree_without_duplicates. */
612 wrap_cleanups_r (tree *tp, int *walk_subtrees ATTRIBUTE_UNUSED,
613 void *data ATTRIBUTE_UNUSED)
618 /* Don't walk into types. */
624 if (TREE_CODE (exp) != TARGET_EXPR)
627 cleanup = TARGET_EXPR_CLEANUP (exp);
630 cleanup = build1 (MUST_NOT_THROW_EXPR, void_type_node, cleanup);
631 TARGET_EXPR_CLEANUP (exp) = cleanup;
634 /* Keep iterating. */
638 /* Build a throw expression. */
641 build_throw (tree exp)
645 if (exp == error_mark_node)
648 if (processing_template_decl)
651 current_function_returns_abnormally = 1;
652 exp = build_min (THROW_EXPR, void_type_node, exp);
653 SET_EXPR_LOCATION (exp, input_location);
657 if (exp == null_node)
658 warning (0, "throwing NULL, which has integral, not pointer type");
660 if (exp != NULL_TREE)
662 if (!is_admissible_throw_operand (exp))
663 return error_mark_node;
667 return error_mark_node;
669 if (exp && decl_is_java_type (TREE_TYPE (exp), 1))
671 tree fn = get_identifier ("_Jv_Throw");
672 if (!get_global_value_if_present (fn, &fn))
674 /* Declare void _Jv_Throw (void *). */
676 tmp = build_function_type_list (ptr_type_node,
677 ptr_type_node, NULL_TREE);
678 fn = push_throw_library_fn (fn, tmp);
680 else if (really_overloaded_fn (fn))
682 error ("%qD should never be overloaded", fn);
683 return error_mark_node;
685 fn = OVL_CURRENT (fn);
686 exp = cp_build_function_call_nary (fn, tf_warning_or_error,
698 /* The CLEANUP_TYPE is the internal type of a destructor. */
701 tmp = build_function_type_list (void_type_node,
702 ptr_type_node, NULL_TREE);
703 cleanup_type = build_pointer_type (tmp);
706 fn = get_identifier ("__cxa_throw");
707 if (!get_global_value_if_present (fn, &fn))
709 /* Declare void __cxa_throw (void*, void*, void (*)(void*)). */
710 /* ??? Second argument is supposed to be "std::type_info*". */
711 tmp = build_function_type_list (void_type_node,
712 ptr_type_node, ptr_type_node,
713 cleanup_type, NULL_TREE);
714 fn = push_throw_library_fn (fn, tmp);
719 A throw-expression initializes a temporary object, the type
720 of which is determined by removing any top-level
721 cv-qualifiers from the static type of the operand of throw
722 and adjusting the type from "array of T" or "function return
723 T" to "pointer to T" or "pointer to function returning T"
725 temp_type = is_bitfield_expr_with_lowered_type (exp);
727 temp_type = cv_unqualified (type_decays_to (TREE_TYPE (exp)));
729 /* OK, this is kind of wacky. The standard says that we call
730 terminate when the exception handling mechanism, after
731 completing evaluation of the expression to be thrown but
732 before the exception is caught (_except.throw_), calls a
733 user function that exits via an uncaught exception.
735 So we have to protect the actual initialization of the
736 exception object with terminate(), but evaluate the
737 expression first. Since there could be temps in the
738 expression, we need to handle that, too. We also expand
739 the call to __cxa_allocate_exception first (which doesn't
740 matter, since it can't throw). */
742 /* Allocate the space for the exception. */
743 allocate_expr = do_allocate_exception (temp_type);
744 allocate_expr = get_target_expr (allocate_expr);
745 ptr = TARGET_EXPR_SLOT (allocate_expr);
746 TARGET_EXPR_CLEANUP (allocate_expr) = do_free_exception (ptr);
747 CLEANUP_EH_ONLY (allocate_expr) = 1;
749 object = build_nop (build_pointer_type (temp_type), ptr);
750 object = cp_build_indirect_ref (object, RO_NULL, tf_warning_or_error);
752 /* And initialize the exception object. */
753 if (CLASS_TYPE_P (temp_type))
755 int flags = LOOKUP_NORMAL | LOOKUP_ONLYCONVERTING;
756 VEC(tree,gc) *exp_vec;
758 /* Under C++0x [12.8/16 class.copy], a thrown lvalue is sometimes
759 treated as an rvalue for the purposes of overload resolution
760 to favor move constructors over copy constructors. */
761 if (/* Must be a local, automatic variable. */
762 TREE_CODE (exp) == VAR_DECL
763 && DECL_CONTEXT (exp) == current_function_decl
764 && ! TREE_STATIC (exp)
765 /* The variable must not have the `volatile' qualifier. */
766 && !(cp_type_quals (TREE_TYPE (exp)) & TYPE_QUAL_VOLATILE))
767 flags = flags | LOOKUP_PREFER_RVALUE;
769 /* Call the copy constructor. */
770 exp_vec = make_tree_vector_single (exp);
771 exp = (build_special_member_call
772 (object, complete_ctor_identifier, &exp_vec,
773 TREE_TYPE (object), flags, tf_warning_or_error));
774 release_tree_vector (exp_vec);
775 if (exp == error_mark_node)
777 error (" in thrown expression");
778 return error_mark_node;
783 tmp = decay_conversion (exp);
784 if (tmp == error_mark_node)
785 return error_mark_node;
786 exp = build2 (INIT_EXPR, temp_type, object, tmp);
789 /* Mark any cleanups from the initialization as MUST_NOT_THROW, since
790 they are run after the exception object is initialized. */
791 cp_walk_tree_without_duplicates (&exp, wrap_cleanups_r, 0);
793 /* Prepend the allocation. */
794 exp = build2 (COMPOUND_EXPR, TREE_TYPE (exp), allocate_expr, exp);
796 /* Force all the cleanups to be evaluated here so that we don't have
797 to do them during unwinding. */
798 exp = build1 (CLEANUP_POINT_EXPR, void_type_node, exp);
800 throw_type = build_eh_type_type (prepare_eh_type (TREE_TYPE (object)));
802 if (TYPE_HAS_NONTRIVIAL_DESTRUCTOR (TREE_TYPE (object)))
804 cleanup = lookup_fnfields (TYPE_BINFO (TREE_TYPE (object)),
805 complete_dtor_identifier, 0);
806 cleanup = BASELINK_FUNCTIONS (cleanup);
808 cxx_mark_addressable (cleanup);
809 /* Pretend it's a normal function. */
810 cleanup = build1 (ADDR_EXPR, cleanup_type, cleanup);
813 cleanup = build_int_cst (cleanup_type, 0);
815 /* ??? Indicate that this function call throws throw_type. */
816 tmp = cp_build_function_call_nary (fn, tf_warning_or_error,
817 ptr, throw_type, cleanup, NULL_TREE);
819 /* Tack on the initialization stuff. */
820 exp = build2 (COMPOUND_EXPR, TREE_TYPE (tmp), exp, tmp);
824 /* Rethrow current exception. */
826 tree fn = get_identifier ("__cxa_rethrow");
827 if (!get_global_value_if_present (fn, &fn))
829 /* Declare void __cxa_rethrow (void). */
830 fn = push_throw_library_fn
831 (fn, build_function_type_list (void_type_node, NULL_TREE));
834 /* ??? Indicate that this function call allows exceptions of the type
835 of the enclosing catch block (if known). */
836 exp = cp_build_function_call_vec (fn, NULL, tf_warning_or_error);
839 exp = build1 (THROW_EXPR, void_type_node, exp);
840 SET_EXPR_LOCATION (exp, input_location);
845 /* Make sure TYPE is complete, pointer to complete, reference to
846 complete, or pointer to cv void. Issue diagnostic on failure.
847 Return the zero on failure and nonzero on success. FROM can be
848 the expr or decl from whence TYPE came, if available. */
851 complete_ptr_ref_or_void_ptr_p (tree type, tree from)
855 /* Check complete. */
856 type = complete_type_or_else (type, from);
860 /* Or a pointer or ref to one, or cv void *. */
861 is_ptr = TREE_CODE (type) == POINTER_TYPE;
862 if (is_ptr || TREE_CODE (type) == REFERENCE_TYPE)
864 tree core = TREE_TYPE (type);
866 if (is_ptr && VOID_TYPE_P (core))
868 else if (!complete_type_or_else (core, from))
874 /* Return truth-value if EXPRESSION is admissible in throw-expression,
875 i.e. if it is not of incomplete type or a pointer/reference to such
876 a type or of an abstract class type. */
879 is_admissible_throw_operand (tree expr)
881 tree type = TREE_TYPE (expr);
883 /* 15.1/4 [...] The type of the throw-expression shall not be an
884 incomplete type, or a pointer or a reference to an incomplete
885 type, other than void*, const void*, volatile void*, or
886 const volatile void*. Except for these restriction and the
887 restrictions on type matching mentioned in 15.3, the operand
888 of throw is treated exactly as a function argument in a call
889 (5.2.2) or the operand of a return statement. */
890 if (!complete_ptr_ref_or_void_ptr_p (type, expr))
893 /* 10.4/3 An abstract class shall not be used as a parameter type,
894 as a function return type or as type of an explicit
896 else if (CLASS_TYPE_P (type) && CLASSTYPE_PURE_VIRTUALS (type))
898 error ("expression %qE of abstract class type %qT cannot "
899 "be used in throw-expression", expr, type);
906 /* Returns nonzero if FN is a declaration of a standard C library
907 function which is known not to throw.
909 [lib.res.on.exception.handling]: None of the functions from the
910 Standard C library shall report an error by throwing an
911 exception, unless it calls a program-supplied function that
912 throws an exception. */
917 nothrow_libfn_p (const_tree fn)
922 && DECL_EXTERNAL (fn)
923 && DECL_NAMESPACE_SCOPE_P (fn)
924 && DECL_EXTERN_C_P (fn))
927 /* Can't be a C library function. */
930 /* Being a C library function, DECL_ASSEMBLER_NAME == DECL_NAME
931 unless the system headers are playing rename tricks, and if
932 they are, we don't want to be confused by them. */
934 return !!libc_name_p (IDENTIFIER_POINTER (id), IDENTIFIER_LENGTH (id));
937 /* Returns nonzero if an exception of type FROM will be caught by a
938 handler for type TO, as per [except.handle]. */
941 can_convert_eh (tree to, tree from)
943 to = non_reference (to);
944 from = non_reference (from);
946 if (TREE_CODE (to) == POINTER_TYPE && TREE_CODE (from) == POINTER_TYPE)
949 from = TREE_TYPE (from);
951 if (! at_least_as_qualified_p (to, from))
954 if (TREE_CODE (to) == VOID_TYPE)
957 /* Else fall through. */
960 if (CLASS_TYPE_P (to) && CLASS_TYPE_P (from)
961 && PUBLICLY_UNIQUELY_DERIVED_P (to, from))
967 /* Check whether any of the handlers in I are shadowed by another handler
968 accepting TYPE. Note that the shadowing may not be complete; even if
969 an exception of type B would be caught by a handler for A, there could
970 be a derived class C for which A is an ambiguous base but B is not, so
971 the handler for B would catch an exception of type C. */
974 check_handlers_1 (tree master, tree_stmt_iterator i)
976 tree type = TREE_TYPE (master);
978 for (; !tsi_end_p (i); tsi_next (&i))
980 tree handler = tsi_stmt (i);
981 if (TREE_TYPE (handler) && can_convert_eh (type, TREE_TYPE (handler)))
983 warning_at (EXPR_LOCATION (handler), 0,
984 "exception of type %qT will be caught",
985 TREE_TYPE (handler));
986 warning_at (EXPR_LOCATION (master), 0,
987 " by earlier handler for %qT", type);
993 /* Given a STATEMENT_LIST of HANDLERs, make sure that they're OK. */
996 check_handlers (tree handlers)
998 tree_stmt_iterator i;
1000 /* If we don't have a STATEMENT_LIST, then we've just got one
1001 handler, and thus nothing to warn about. */
1002 if (TREE_CODE (handlers) != STATEMENT_LIST)
1005 i = tsi_start (handlers);
1009 tree handler = tsi_stmt (i);
1012 /* No more handlers; nothing to shadow. */
1015 if (TREE_TYPE (handler) == NULL_TREE)
1016 permerror (EXPR_LOCATION (handler), "%<...%>"
1017 " handler must be the last handler for its try block");
1019 check_handlers_1 (handler, i);
1023 /* walk_tree helper for finish_noexcept_expr. Returns non-null if the
1024 expression *TP causes the noexcept operator to evaluate to false.
1026 5.3.7 [expr.noexcept]: The result of the noexcept operator is false if
1027 in a potentially-evaluated context the expression would contain
1028 * a potentially evaluated call to a function, member function,
1029 function pointer, or member function pointer that does not have a
1030 non-throwing exception-specification (15.4),
1031 * a potentially evaluated throw-expression (15.1),
1032 * a potentially evaluated dynamic_cast expression dynamic_cast<T>(v),
1033 where T is a reference type, that requires a run-time check (5.2.7), or
1034 * a potentially evaluated typeid expression (5.2.8) applied to a glvalue
1035 expression whose type is a polymorphic class type (10.3). */
1038 check_noexcept_r (tree *tp, int *walk_subtrees ATTRIBUTE_UNUSED,
1039 void *data ATTRIBUTE_UNUSED)
1042 enum tree_code code = TREE_CODE (t);
1043 if (code == CALL_EXPR
1044 || code == AGGR_INIT_EXPR)
1046 /* We can only use the exception specification of the called function
1047 for determining the value of a noexcept expression; we can't use
1048 TREE_NOTHROW, as it might have a different value in another
1049 translation unit, creating ODR problems.
1051 We could use TREE_NOTHROW (t) for !TREE_PUBLIC fns, though... */
1052 tree fn = (code == AGGR_INIT_EXPR
1053 ? AGGR_INIT_EXPR_FN (t) : CALL_EXPR_FN (t));
1054 tree type = TREE_TYPE (TREE_TYPE (fn));
1057 if (TREE_CODE (fn) == ADDR_EXPR)
1058 fn = TREE_OPERAND (fn, 0);
1059 if (TREE_CODE (fn) == FUNCTION_DECL)
1061 /* We do use TREE_NOTHROW for ABI internals like __dynamic_cast,
1062 and for C library functions known not to throw. */
1063 if (DECL_EXTERN_C_P (fn)
1064 && (DECL_ARTIFICIAL (fn)
1065 || nothrow_libfn_p (fn)))
1066 return TREE_NOTHROW (fn) ? NULL_TREE : fn;
1067 /* A call to a constexpr function is noexcept if the call
1068 is a constant expression. */
1069 if (DECL_DECLARED_CONSTEXPR_P (fn)
1070 && is_sub_constant_expr (t))
1073 if (!TYPE_NOTHROW_P (type))
1080 /* If a function that causes a noexcept-expression to be false isn't
1081 defined yet, remember it and check it for TREE_NOTHROW again at EOF. */
1083 typedef struct GTY(()) pending_noexcept {
1087 DEF_VEC_O(pending_noexcept);
1088 DEF_VEC_ALLOC_O(pending_noexcept,gc);
1089 static GTY(()) VEC(pending_noexcept,gc) *pending_noexcept_checks;
1091 /* FN is a FUNCTION_DECL that caused a noexcept-expr to be false. Warn if
1095 maybe_noexcept_warning (tree fn)
1097 if (TREE_NOTHROW (fn))
1099 warning (OPT_Wnoexcept, "noexcept-expression evaluates to %<false%> "
1100 "because of a call to %qD", fn);
1101 warning (OPT_Wnoexcept, "but %q+D does not throw; perhaps "
1102 "it should be declared %<noexcept%>", fn);
1106 /* Check any functions that weren't defined earlier when they caused a
1107 noexcept expression to evaluate to false. */
1110 perform_deferred_noexcept_checks (void)
1113 pending_noexcept *p;
1114 location_t saved_loc = input_location;
1115 FOR_EACH_VEC_ELT (pending_noexcept, pending_noexcept_checks, i, p)
1117 input_location = p->loc;
1118 maybe_noexcept_warning (p->fn);
1120 input_location = saved_loc;
1123 /* Evaluate noexcept ( EXPR ). */
1126 finish_noexcept_expr (tree expr, tsubst_flags_t complain)
1128 if (expr == error_mark_node)
1129 return error_mark_node;
1131 if (processing_template_decl)
1132 return build_min (NOEXCEPT_EXPR, boolean_type_node, expr);
1134 return (expr_noexcept_p (expr, complain)
1135 ? boolean_true_node : boolean_false_node);
1138 /* Returns whether EXPR is noexcept, possibly warning if allowed by
1142 expr_noexcept_p (tree expr, tsubst_flags_t complain)
1146 if (expr == error_mark_node)
1149 fn = cp_walk_tree_without_duplicates (&expr, check_noexcept_r, 0);
1152 if ((complain & tf_warning) && warn_noexcept
1153 && TREE_CODE (fn) == FUNCTION_DECL)
1155 if (!DECL_INITIAL (fn))
1157 /* Not defined yet; check again at EOF. */
1159 = VEC_safe_push (pending_noexcept, gc,
1160 pending_noexcept_checks, NULL);
1162 p->loc = input_location;
1165 maybe_noexcept_warning (fn);
1173 /* Return true iff SPEC is throw() or noexcept(true). */
1176 nothrow_spec_p (const_tree spec)
1178 gcc_assert (!DEFERRED_NOEXCEPT_SPEC_P (spec));
1179 if (spec == NULL_TREE
1180 || TREE_VALUE (spec) != NULL_TREE
1181 || spec == noexcept_false_spec)
1183 if (TREE_PURPOSE (spec) == NULL_TREE
1184 || spec == noexcept_true_spec)
1186 gcc_assert (processing_template_decl
1187 || TREE_PURPOSE (spec) == error_mark_node);
1191 /* For FUNCTION_TYPE or METHOD_TYPE, true if NODE is noexcept. This is the
1192 case for things declared noexcept(true) and, with -fnothrow-opt, for
1193 throw() functions. */
1196 type_noexcept_p (const_tree type)
1198 tree spec = TYPE_RAISES_EXCEPTIONS (type);
1199 gcc_assert (!DEFERRED_NOEXCEPT_SPEC_P (spec));
1200 if (flag_nothrow_opt)
1201 return nothrow_spec_p (spec);
1203 return spec == noexcept_true_spec;
1206 /* For FUNCTION_TYPE or METHOD_TYPE, true if NODE can throw any type,
1207 i.e. no exception-specification or noexcept(false). */
1210 type_throw_all_p (const_tree type)
1212 tree spec = TYPE_RAISES_EXCEPTIONS (type);
1213 gcc_assert (!DEFERRED_NOEXCEPT_SPEC_P (spec));
1214 return spec == NULL_TREE || spec == noexcept_false_spec;
1217 /* Create a representation of the noexcept-specification with
1218 constant-expression of EXPR. COMPLAIN is as for tsubst. */
1221 build_noexcept_spec (tree expr, int complain)
1223 /* This isn't part of the signature, so don't bother trying to evaluate
1224 it until instantiation. */
1225 if (!processing_template_decl && TREE_CODE (expr) != DEFERRED_NOEXCEPT)
1227 expr = perform_implicit_conversion_flags (boolean_type_node, expr,
1230 expr = cxx_constant_value (expr);
1232 if (expr == boolean_true_node)
1233 return noexcept_true_spec;
1234 else if (expr == boolean_false_node)
1235 return noexcept_false_spec;
1236 else if (expr == error_mark_node)
1237 return error_mark_node;
1240 gcc_assert (processing_template_decl || expr == error_mark_node
1241 || TREE_CODE (expr) == DEFERRED_NOEXCEPT);
1242 return build_tree_list (expr, NULL_TREE);
1246 #include "gt-cp-except.h"