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 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.
8 This file is part of GCC.
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)
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.
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, 51 Franklin Street, Fifth Floor,
23 Boston, MA 02110-1301, USA. */
28 #include "coretypes.h"
39 #include "tree-inline.h"
40 #include "tree-iterator.h"
43 static void push_eh_cleanup (tree);
44 static tree prepare_eh_type (tree);
45 static tree build_eh_type_type (tree);
46 static tree do_begin_catch (void);
47 static int dtor_nothrow (tree);
48 static tree do_end_catch (tree);
49 static bool decl_is_java_type (tree decl, int err);
50 static void initialize_handler_parm (tree, tree);
51 static tree do_allocate_exception (tree);
52 static tree wrap_cleanups_r (tree *, int *, void *);
53 static int complete_ptr_ref_or_void_ptr_p (tree, tree);
54 static bool is_admissible_throw_operand (tree);
55 static int can_convert_eh (tree, tree);
56 static tree cp_protect_cleanup_actions (void);
58 /* Sets up all the global eh stuff that needs to be initialized at the
59 start of compilation. */
62 init_exception_processing (void)
66 /* void std::terminate (); */
67 push_namespace (std_identifier);
68 tmp = build_function_type (void_type_node, void_list_node);
69 terminate_node = build_cp_library_fn_ptr ("terminate", tmp);
70 TREE_THIS_VOLATILE (terminate_node) = 1;
71 TREE_NOTHROW (terminate_node) = 1;
74 /* void __cxa_call_unexpected(void *); */
75 tmp = tree_cons (NULL_TREE, ptr_type_node, void_list_node);
76 tmp = build_function_type (void_type_node, tmp);
78 = push_throw_library_fn (get_identifier ("__cxa_call_unexpected"), tmp);
80 eh_personality_libfunc = init_one_libfunc (USING_SJLJ_EXCEPTIONS
81 ? "__gxx_personality_sj0"
82 : "__gxx_personality_v0");
83 if (targetm.arm_eabi_unwinder)
84 unwind_resume_libfunc = init_one_libfunc ("__cxa_end_cleanup");
86 default_init_unwind_resume_libfunc ();
88 lang_eh_runtime_type = build_eh_type_type;
89 lang_protect_cleanup_actions = &cp_protect_cleanup_actions;
92 /* Returns an expression to be executed if an unhandled exception is
93 propagated out of a cleanup region. */
96 cp_protect_cleanup_actions (void)
100 When the destruction of an object during stack unwinding exits
101 using an exception ... void terminate(); is called. */
102 return build_call (terminate_node, NULL_TREE);
106 prepare_eh_type (tree type)
108 if (type == NULL_TREE)
110 if (type == error_mark_node)
111 return error_mark_node;
113 /* peel back references, so they match. */
114 type = non_reference (type);
116 /* Peel off cv qualifiers. */
117 type = TYPE_MAIN_VARIANT (type);
122 /* Return the type info for TYPE as used by EH machinery. */
124 eh_type_info (tree type)
128 if (type == NULL_TREE || type == error_mark_node)
131 if (decl_is_java_type (type, 0))
132 exp = build_java_class_ref (TREE_TYPE (type));
134 exp = get_tinfo_decl (type);
139 /* Build the address of a typeinfo decl for use in the runtime
140 matching field of the exception model. */
143 build_eh_type_type (tree type)
145 tree exp = eh_type_info (type);
152 return convert (ptr_type_node, build_address (exp));
158 return build0 (EXC_PTR_EXPR, ptr_type_node);
161 /* Build up a call to __cxa_get_exception_ptr so that we can build a
162 copy constructor for the thrown object. */
165 do_get_exception_ptr (void)
169 fn = get_identifier ("__cxa_get_exception_ptr");
170 if (!get_global_value_if_present (fn, &fn))
172 /* Declare void* __cxa_get_exception_ptr (void *). */
173 tree tmp = tree_cons (NULL_TREE, ptr_type_node, void_list_node);
174 fn = push_library_fn (fn, build_function_type (ptr_type_node, tmp));
177 return build_function_call (fn, tree_cons (NULL_TREE, build_exc_ptr (),
181 /* Build up a call to __cxa_begin_catch, to tell the runtime that the
182 exception has been handled. */
185 do_begin_catch (void)
189 fn = get_identifier ("__cxa_begin_catch");
190 if (!get_global_value_if_present (fn, &fn))
192 /* Declare void* __cxa_begin_catch (void *). */
193 tree tmp = tree_cons (NULL_TREE, ptr_type_node, void_list_node);
194 fn = push_library_fn (fn, build_function_type (ptr_type_node, tmp));
197 return build_function_call (fn, tree_cons (NULL_TREE, build_exc_ptr (),
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)
210 if (!CLASS_TYPE_P (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 = build_function_call (fn, NULL_TREE);
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 eh_personality_libfunc is set to
298 __gxx_personality_(sj|v)0 in init_exception_processing - should it
299 be done here instead? */
301 choose_personality_routine (enum languages lang)
316 if (lang != lang_cplusplus)
321 if (lang != lang_java)
326 ; /* Proceed to language selection. */
337 eh_personality_libfunc = init_one_libfunc (USING_SJLJ_EXCEPTIONS
338 ? "__gcj_personality_sj0"
339 : "__gcj_personality_v0");
348 error ("mixing C++ and Java catches in a single translation unit");
352 /* Initialize the catch parameter DECL. */
355 initialize_handler_parm (tree decl, tree exp)
360 /* Make sure we mark the catch param as used, otherwise we'll get a
361 warning about an unused ((anonymous)). */
362 TREE_USED (decl) = 1;
364 /* Figure out the type that the initializer is. Pointers are returned
365 adjusted by value from __cxa_begin_catch. Others are returned by
367 init_type = TREE_TYPE (decl);
368 if (!POINTER_TYPE_P (init_type))
369 init_type = build_reference_type (init_type);
371 choose_personality_routine (decl_is_java_type (init_type, 0)
372 ? lang_java : lang_cplusplus);
374 /* Since pointers are passed by value, initialize a reference to
375 pointer catch parm with the address of the temporary. */
376 if (TREE_CODE (init_type) == REFERENCE_TYPE
377 && TYPE_PTR_P (TREE_TYPE (init_type)))
378 exp = build_unary_op (ADDR_EXPR, exp, 1);
380 exp = ocp_convert (init_type, exp, CONV_IMPLICIT|CONV_FORCE_TEMP, 0);
382 init = convert_from_reference (exp);
384 /* If the constructor for the catch parm exits via an exception, we
385 must call terminate. See eh23.C. */
386 if (TYPE_NEEDS_CONSTRUCTING (TREE_TYPE (decl)))
388 /* Generate the copy constructor call directly so we can wrap it.
389 See also expand_default_init. */
390 init = ocp_convert (TREE_TYPE (decl), init,
391 CONV_IMPLICIT|CONV_FORCE_TEMP, 0);
392 init = build1 (MUST_NOT_THROW_EXPR, TREE_TYPE (init), init);
395 /* Let `cp_finish_decl' know that this initializer is ok. */
396 DECL_INITIAL (decl) = error_mark_node;
397 decl = pushdecl (decl);
400 cp_finish_decl (decl, init, /*init_const_expr_p=*/false, NULL_TREE,
401 LOOKUP_ONLYCONVERTING|DIRECT_BIND);
404 /* Call this to start a catch block. DECL is the catch parameter. */
407 expand_start_catch_block (tree decl)
415 /* Make sure this declaration is reasonable. */
416 if (decl && !complete_ptr_ref_or_void_ptr_p (TREE_TYPE (decl), NULL_TREE))
420 type = prepare_eh_type (TREE_TYPE (decl));
424 if (decl && decl_is_java_type (type, 1))
426 /* Java only passes object via pointer and doesn't require
427 adjusting. The java object is immediately before the
428 generic exception header. */
429 exp = build_exc_ptr ();
430 exp = build1 (NOP_EXPR, build_pointer_type (type), exp);
431 exp = build2 (MINUS_EXPR, TREE_TYPE (exp), exp,
432 TYPE_SIZE_UNIT (TREE_TYPE (exp)));
433 exp = build_indirect_ref (exp, NULL);
434 initialize_handler_parm (decl, exp);
438 /* Call __cxa_end_catch at the end of processing the exception. */
439 push_eh_cleanup (type);
441 /* If there's no decl at all, then all we need to do is make sure
442 to tell the runtime that we've begun handling the exception. */
444 finish_expr_stmt (do_begin_catch ());
446 /* If the C++ object needs constructing, we need to do that before
447 calling __cxa_begin_catch, so that std::uncaught_exception gets
448 the right value during the copy constructor. */
449 else if (TYPE_NEEDS_CONSTRUCTING (TREE_TYPE (decl)))
451 exp = do_get_exception_ptr ();
452 initialize_handler_parm (decl, exp);
453 finish_expr_stmt (do_begin_catch ());
456 /* Otherwise the type uses a bitwise copy, and we don't have to worry
457 about the value of std::uncaught_exception and therefore can do the
458 copy with the return value of __cxa_end_catch instead. */
461 tree init = do_begin_catch ();
462 exp = create_temporary_var (ptr_type_node);
463 DECL_REGISTER (exp) = 1;
464 cp_finish_decl (exp, init, /*init_const_expr=*/false,
465 NULL_TREE, LOOKUP_ONLYCONVERTING);
466 finish_expr_stmt (build_modify_expr (exp, INIT_EXPR, init));
467 initialize_handler_parm (decl, exp);
474 /* Call this to end a catch block. Its responsible for emitting the
475 code to handle jumping back to the correct place, and for emitting
476 the label to jump to if this catch block didn't match. */
479 expand_end_catch_block (void)
484 /* The exception being handled is rethrown if control reaches the end of
485 a handler of the function-try-block of a constructor or destructor. */
486 if (in_function_try_handler
487 && (DECL_CONSTRUCTOR_P (current_function_decl)
488 || DECL_DESTRUCTOR_P (current_function_decl)))
489 finish_expr_stmt (build_throw (NULL_TREE));
493 begin_eh_spec_block (void)
495 tree r = build_stmt (EH_SPEC_BLOCK, NULL_TREE, NULL_TREE);
497 EH_SPEC_STMTS (r) = push_stmt_list ();
502 finish_eh_spec_block (tree raw_raises, tree eh_spec_block)
506 EH_SPEC_STMTS (eh_spec_block) = pop_stmt_list (EH_SPEC_STMTS (eh_spec_block));
508 /* Strip cv quals, etc, from the specification types. */
509 for (raises = NULL_TREE;
510 raw_raises && TREE_VALUE (raw_raises);
511 raw_raises = TREE_CHAIN (raw_raises))
513 tree type = prepare_eh_type (TREE_VALUE (raw_raises));
514 tree tinfo = eh_type_info (type);
517 raises = tree_cons (NULL_TREE, type, raises);
520 EH_SPEC_RAISES (eh_spec_block) = raises;
523 /* Return a pointer to a buffer for an exception object of type TYPE. */
526 do_allocate_exception (tree type)
530 fn = get_identifier ("__cxa_allocate_exception");
531 if (!get_global_value_if_present (fn, &fn))
533 /* Declare void *__cxa_allocate_exception(size_t). */
534 tree tmp = tree_cons (NULL_TREE, size_type_node, void_list_node);
535 fn = push_library_fn (fn, build_function_type (ptr_type_node, tmp));
538 return build_function_call (fn, tree_cons (NULL_TREE, size_in_bytes (type),
542 /* Call __cxa_free_exception from a cleanup. This is never invoked
543 directly, but see the comment for stabilize_throw_expr. */
546 do_free_exception (tree ptr)
550 fn = get_identifier ("__cxa_free_exception");
551 if (!get_global_value_if_present (fn, &fn))
553 /* Declare void __cxa_free_exception (void *). */
554 fn = push_void_library_fn (fn, tree_cons (NULL_TREE, ptr_type_node,
558 return build_function_call (fn, tree_cons (NULL_TREE, ptr, NULL_TREE));
561 /* Wrap all cleanups for TARGET_EXPRs in MUST_NOT_THROW_EXPR.
562 Called from build_throw via walk_tree_without_duplicates. */
565 wrap_cleanups_r (tree *tp, int *walk_subtrees ATTRIBUTE_UNUSED,
566 void *data ATTRIBUTE_UNUSED)
571 /* Don't walk into types. */
577 if (TREE_CODE (exp) != TARGET_EXPR)
580 cleanup = TARGET_EXPR_CLEANUP (exp);
583 cleanup = build1 (MUST_NOT_THROW_EXPR, void_type_node, cleanup);
584 TARGET_EXPR_CLEANUP (exp) = cleanup;
587 /* Keep iterating. */
591 /* Build a throw expression. */
594 build_throw (tree exp)
598 if (exp == error_mark_node)
601 if (processing_template_decl)
603 current_function_returns_abnormally = 1;
604 return build_min (THROW_EXPR, void_type_node, exp);
607 if (exp == null_node)
608 warning (0, "throwing NULL, which has integral, not pointer type");
610 if (exp != NULL_TREE)
612 if (!is_admissible_throw_operand (exp))
613 return error_mark_node;
617 return error_mark_node;
619 if (exp && decl_is_java_type (TREE_TYPE (exp), 1))
621 tree fn = get_identifier ("_Jv_Throw");
622 if (!get_global_value_if_present (fn, &fn))
624 /* Declare void _Jv_Throw (void *). */
625 tree tmp = tree_cons (NULL_TREE, ptr_type_node, void_list_node);
626 tmp = build_function_type (ptr_type_node, tmp);
627 fn = push_throw_library_fn (fn, tmp);
629 else if (really_overloaded_fn (fn))
631 error ("%qD should never be overloaded", fn);
632 return error_mark_node;
634 fn = OVL_CURRENT (fn);
635 exp = build_function_call (fn, tree_cons (NULL_TREE, exp, NULL_TREE));
643 tree temp_expr, allocate_expr;
646 /* The CLEANUP_TYPE is the internal type of a destructor. */
649 tmp = void_list_node;
650 tmp = tree_cons (NULL_TREE, ptr_type_node, tmp);
651 tmp = build_function_type (void_type_node, tmp);
652 cleanup_type = build_pointer_type (tmp);
655 fn = get_identifier ("__cxa_throw");
656 if (!get_global_value_if_present (fn, &fn))
658 /* Declare void __cxa_throw (void*, void*, void (*)(void*)). */
659 /* ??? Second argument is supposed to be "std::type_info*". */
660 tmp = void_list_node;
661 tmp = tree_cons (NULL_TREE, cleanup_type, tmp);
662 tmp = tree_cons (NULL_TREE, ptr_type_node, tmp);
663 tmp = tree_cons (NULL_TREE, ptr_type_node, tmp);
664 tmp = build_function_type (void_type_node, tmp);
665 fn = push_throw_library_fn (fn, tmp);
668 /* throw expression */
669 /* First, decay it. */
670 exp = decay_conversion (exp);
672 /* OK, this is kind of wacky. The standard says that we call
673 terminate when the exception handling mechanism, after
674 completing evaluation of the expression to be thrown but
675 before the exception is caught (_except.throw_), calls a
676 user function that exits via an uncaught exception.
678 So we have to protect the actual initialization of the
679 exception object with terminate(), but evaluate the
680 expression first. Since there could be temps in the
681 expression, we need to handle that, too. We also expand
682 the call to __cxa_allocate_exception first (which doesn't
683 matter, since it can't throw). */
685 /* Allocate the space for the exception. */
686 allocate_expr = do_allocate_exception (TREE_TYPE (exp));
687 allocate_expr = get_target_expr (allocate_expr);
688 ptr = TARGET_EXPR_SLOT (allocate_expr);
689 object = build1 (NOP_EXPR, build_pointer_type (TREE_TYPE (exp)), ptr);
690 object = build_indirect_ref (object, NULL);
692 elided = (TREE_CODE (exp) == TARGET_EXPR);
694 /* And initialize the exception object. */
695 exp = build_init (object, exp, LOOKUP_ONLYCONVERTING);
696 if (exp == error_mark_node)
698 error (" in thrown expression");
699 return error_mark_node;
702 /* Pre-evaluate the thrown expression first, since if we allocated
703 the space first we would have to deal with cleaning it up if
704 evaluating this expression throws.
706 The case where EXP the initializer is a cast or a function
707 returning a class is a bit of a grey area in the standard; it's
708 unclear whether or not it should be allowed to throw. We used to
709 say no, as that allowed us to optimize this case without worrying
710 about deallocating the exception object if it does. But that
711 conflicted with expectations (PR 13944) and the EDG compiler; now
712 we wrap the initialization in a TRY_CATCH_EXPR to call
713 do_free_exception rather than in a MUST_NOT_THROW_EXPR, for this
716 BUT: Issue 475 may do away with this inconsistency by removing the
717 terminate() in this situation.
719 Note that we don't check the return value from stabilize_init
720 because it will only return false in cases where elided is true,
721 and therefore we don't need to work around the failure to
723 temp_expr = NULL_TREE;
724 stabilize_init (exp, &temp_expr);
726 exp = build1 (CLEANUP_POINT_EXPR, TREE_TYPE (exp), exp);
728 exp = build2 (TRY_CATCH_EXPR, void_type_node, exp,
729 do_free_exception (ptr));
731 exp = build1 (MUST_NOT_THROW_EXPR, void_type_node, exp);
733 /* Prepend the allocation. */
734 exp = build2 (COMPOUND_EXPR, TREE_TYPE (exp), allocate_expr, exp);
737 /* Prepend the calculation of the throw expression. Also, force
738 any cleanups from the expression to be evaluated here so that
739 we don't have to do them during unwinding. But first wrap
740 them in MUST_NOT_THROW_EXPR, since they are run after the
741 exception object is initialized. */
742 walk_tree_without_duplicates (&temp_expr, wrap_cleanups_r, 0);
743 exp = build2 (COMPOUND_EXPR, TREE_TYPE (exp), temp_expr, exp);
744 exp = build1 (CLEANUP_POINT_EXPR, TREE_TYPE (exp), exp);
747 throw_type = build_eh_type_type (prepare_eh_type (TREE_TYPE (object)));
749 if (TYPE_HAS_NONTRIVIAL_DESTRUCTOR (TREE_TYPE (object)))
751 cleanup = lookup_fnfields (TYPE_BINFO (TREE_TYPE (object)),
752 complete_dtor_identifier, 0);
753 cleanup = BASELINK_FUNCTIONS (cleanup);
755 cxx_mark_addressable (cleanup);
756 /* Pretend it's a normal function. */
757 cleanup = build1 (ADDR_EXPR, cleanup_type, cleanup);
760 cleanup = build_int_cst (cleanup_type, 0);
762 tmp = tree_cons (NULL_TREE, cleanup, NULL_TREE);
763 tmp = tree_cons (NULL_TREE, throw_type, tmp);
764 tmp = tree_cons (NULL_TREE, ptr, tmp);
765 /* ??? Indicate that this function call throws throw_type. */
766 tmp = build_function_call (fn, tmp);
768 /* Tack on the initialization stuff. */
769 exp = build2 (COMPOUND_EXPR, TREE_TYPE (tmp), exp, tmp);
773 /* Rethrow current exception. */
775 tree fn = get_identifier ("__cxa_rethrow");
776 if (!get_global_value_if_present (fn, &fn))
778 /* Declare void __cxa_rethrow (void). */
779 fn = push_throw_library_fn
780 (fn, build_function_type (void_type_node, void_list_node));
783 /* ??? Indicate that this function call allows exceptions of the type
784 of the enclosing catch block (if known). */
785 exp = build_function_call (fn, NULL_TREE);
788 exp = build1 (THROW_EXPR, void_type_node, exp);
793 /* Make sure TYPE is complete, pointer to complete, reference to
794 complete, or pointer to cv void. Issue diagnostic on failure.
795 Return the zero on failure and nonzero on success. FROM can be
796 the expr or decl from whence TYPE came, if available. */
799 complete_ptr_ref_or_void_ptr_p (tree type, tree from)
803 /* Check complete. */
804 type = complete_type_or_else (type, from);
808 /* Or a pointer or ref to one, or cv void *. */
809 is_ptr = TREE_CODE (type) == POINTER_TYPE;
810 if (is_ptr || TREE_CODE (type) == REFERENCE_TYPE)
812 tree core = TREE_TYPE (type);
814 if (is_ptr && VOID_TYPE_P (core))
816 else if (!complete_type_or_else (core, from))
822 /* Return truth-value if EXPRESSION is admissible in throw-expression,
823 i.e. if it is not of incomplete type or a pointer/reference to such
824 a type or of an abstract class type. */
827 is_admissible_throw_operand (tree expr)
829 tree type = TREE_TYPE (expr);
831 /* 15.1/4 [...] The type of the throw-expression shall not be an
832 incomplete type, or a pointer or a reference to an incomplete
833 type, other than void*, const void*, volatile void*, or
834 const volatile void*. Except for these restriction and the
835 restrictions on type matching mentioned in 15.3, the operand
836 of throw is treated exactly as a function argument in a call
837 (5.2.2) or the operand of a return statement. */
838 if (!complete_ptr_ref_or_void_ptr_p (type, expr))
841 /* 10.4/3 An abstract class shall not be used as a parameter type,
842 as a function return type or as type of an explicit
844 else if (CLASS_TYPE_P (type) && CLASSTYPE_PURE_VIRTUALS (type))
846 error ("expression %qE of abstract class type %qT cannot "
847 "be used in throw-expression", expr, type);
854 /* Returns nonzero if FN is a declaration of a standard C library
855 function which is known not to throw.
857 [lib.res.on.exception.handling]: None of the functions from the
858 Standard C library shall report an error by throwing an
859 exception, unless it calls a program-supplied function that
860 throws an exception. */
865 nothrow_libfn_p (tree fn)
870 && DECL_EXTERNAL (fn)
871 && DECL_NAMESPACE_SCOPE_P (fn)
872 && DECL_EXTERN_C_P (fn))
875 /* Can't be a C library function. */
878 /* Being a C library function, DECL_ASSEMBLER_NAME == DECL_NAME
879 unless the system headers are playing rename tricks, and if
880 they are, we don't want to be confused by them. */
882 return !!libc_name_p (IDENTIFIER_POINTER (id), IDENTIFIER_LENGTH (id));
885 /* Returns nonzero if an exception of type FROM will be caught by a
886 handler for type TO, as per [except.handle]. */
889 can_convert_eh (tree to, tree from)
891 to = non_reference (to);
892 from = non_reference (from);
894 if (TREE_CODE (to) == POINTER_TYPE && TREE_CODE (from) == POINTER_TYPE)
897 from = TREE_TYPE (from);
899 if (! at_least_as_qualified_p (to, from))
902 if (TREE_CODE (to) == VOID_TYPE)
905 /* Else fall through. */
908 if (CLASS_TYPE_P (to) && CLASS_TYPE_P (from)
909 && PUBLICLY_UNIQUELY_DERIVED_P (to, from))
915 /* Check whether any of the handlers in I are shadowed by another handler
916 accepting TYPE. Note that the shadowing may not be complete; even if
917 an exception of type B would be caught by a handler for A, there could
918 be a derived class C for which A is an ambiguous base but B is not, so
919 the handler for B would catch an exception of type C. */
922 check_handlers_1 (tree master, tree_stmt_iterator i)
924 tree type = TREE_TYPE (master);
926 for (; !tsi_end_p (i); tsi_next (&i))
928 tree handler = tsi_stmt (i);
929 if (TREE_TYPE (handler) && can_convert_eh (type, TREE_TYPE (handler)))
931 warning (0, "%Hexception of type %qT will be caught",
932 EXPR_LOCUS (handler), TREE_TYPE (handler));
933 warning (0, "%H by earlier handler for %qT",
934 EXPR_LOCUS (master), type);
940 /* Given a STATEMENT_LIST of HANDLERs, make sure that they're OK. */
943 check_handlers (tree handlers)
945 tree_stmt_iterator i;
947 /* If we don't have a STATEMENT_LIST, then we've just got one
948 handler, and thus nothing to warn about. */
949 if (TREE_CODE (handlers) != STATEMENT_LIST)
952 i = tsi_start (handlers);
956 tree handler = tsi_stmt (i);
959 /* No more handlers; nothing to shadow. */
962 if (TREE_TYPE (handler) == NULL_TREE)
963 pedwarn ("%H%<...%> handler must be the last handler for"
964 " its try block", EXPR_LOCUS (handler));
966 check_handlers_1 (handler, i);