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"
39 #include "tree-inline.h"
40 #include "tree-iterator.h"
44 static void push_eh_cleanup (tree);
45 static tree prepare_eh_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 lang_protect_cleanup_actions = &cp_protect_cleanup_actions;
83 /* Returns an expression to be executed if an unhandled exception is
84 propagated out of a cleanup region. */
87 cp_protect_cleanup_actions (void)
91 When the destruction of an object during stack unwinding exits
92 using an exception ... void terminate(); is called. */
93 return terminate_node;
97 prepare_eh_type (tree type)
99 if (type == NULL_TREE)
101 if (type == error_mark_node)
102 return error_mark_node;
104 /* peel back references, so they match. */
105 type = non_reference (type);
107 /* Peel off cv qualifiers. */
108 type = TYPE_MAIN_VARIANT (type);
110 /* Functions and arrays decay to pointers. */
111 type = type_decays_to (type);
116 /* Return the type info for TYPE as used by EH machinery. */
118 eh_type_info (tree type)
122 if (type == NULL_TREE || type == error_mark_node)
125 if (decl_is_java_type (type, 0))
126 exp = build_java_class_ref (TREE_TYPE (type));
128 exp = get_tinfo_decl (type);
133 /* Build the address of a typeinfo decl for use in the runtime
134 matching field of the exception model. */
137 build_eh_type_type (tree type)
139 tree exp = eh_type_info (type);
146 return convert (ptr_type_node, build_address (exp));
152 return build_call_n (built_in_decls [BUILT_IN_EH_POINTER],
153 1, integer_zero_node);
156 /* Declare a function NAME, returning RETURN_TYPE, taking a single
157 parameter PARM_TYPE, with an empty exception specification.
159 Note that the C++ ABI document does not have a throw-specifier on
160 the routines declared below via this function. The declarations
161 are consistent with the actual implementations in libsupc++. */
164 declare_nothrow_library_fn (tree name, tree return_type, tree parm_type)
166 tree tmp = tree_cons (NULL_TREE, parm_type, void_list_node);
167 return push_library_fn (name, build_function_type (return_type, tmp),
171 /* Build up a call to __cxa_get_exception_ptr so that we can build a
172 copy constructor for the thrown object. */
175 do_get_exception_ptr (void)
179 fn = get_identifier ("__cxa_get_exception_ptr");
180 if (!get_global_value_if_present (fn, &fn))
182 /* Declare void* __cxa_get_exception_ptr (void *) throw(). */
183 fn = declare_nothrow_library_fn (fn, ptr_type_node, ptr_type_node);
186 return cp_build_function_call (fn, tree_cons (NULL_TREE, build_exc_ptr (),
188 tf_warning_or_error);
191 /* Build up a call to __cxa_begin_catch, to tell the runtime that the
192 exception has been handled. */
195 do_begin_catch (void)
199 fn = get_identifier ("__cxa_begin_catch");
200 if (!get_global_value_if_present (fn, &fn))
202 /* Declare void* __cxa_begin_catch (void *) throw(). */
203 fn = declare_nothrow_library_fn (fn, ptr_type_node, ptr_type_node);
206 return cp_build_function_call (fn, tree_cons (NULL_TREE, build_exc_ptr (),
208 tf_warning_or_error);
211 /* Returns nonzero if cleaning up an exception of type TYPE (which can be
212 NULL_TREE for a ... handler) will not throw an exception. */
215 dtor_nothrow (tree type)
217 if (type == NULL_TREE || type == error_mark_node)
220 if (TYPE_HAS_TRIVIAL_DESTRUCTOR (type))
223 if (CLASSTYPE_LAZY_DESTRUCTOR (type))
224 lazily_declare_fn (sfk_destructor, type);
226 return TREE_NOTHROW (CLASSTYPE_DESTRUCTORS (type));
229 /* Build up a call to __cxa_end_catch, to destroy the exception object
230 for the current catch block if no others are currently using it. */
233 do_end_catch (tree type)
237 fn = get_identifier ("__cxa_end_catch");
238 if (!get_global_value_if_present (fn, &fn))
240 /* Declare void __cxa_end_catch (). */
241 fn = push_void_library_fn (fn, void_list_node);
242 /* This can throw if the destructor for the exception throws. */
243 TREE_NOTHROW (fn) = 0;
246 cleanup = cp_build_function_call (fn, NULL_TREE, tf_warning_or_error);
247 TREE_NOTHROW (cleanup) = dtor_nothrow (type);
252 /* This routine creates the cleanup for the current exception. */
255 push_eh_cleanup (tree type)
257 finish_decl_cleanup (NULL_TREE, do_end_catch (type));
260 /* Return nonzero value if DECL is a Java type suitable for catch or
264 decl_is_java_type (tree decl, int err)
266 bool r = (TREE_CODE (decl) == POINTER_TYPE
267 && TREE_CODE (TREE_TYPE (decl)) == RECORD_TYPE
268 && TYPE_FOR_JAVA (TREE_TYPE (decl)));
272 if (TREE_CODE (decl) == REFERENCE_TYPE
273 && TREE_CODE (TREE_TYPE (decl)) == RECORD_TYPE
274 && TYPE_FOR_JAVA (TREE_TYPE (decl)))
276 /* Can't throw a reference. */
277 error ("type %qT is disallowed in Java %<throw%> or %<catch%>",
284 = IDENTIFIER_GLOBAL_VALUE (get_identifier ("jthrowable"));
286 if (jthrow_node == NULL_TREE)
288 ("call to Java %<catch%> or %<throw%> with %<jthrowable%> undefined");
290 jthrow_node = TREE_TYPE (TREE_TYPE (jthrow_node));
292 if (! DERIVED_FROM_P (jthrow_node, TREE_TYPE (decl)))
294 /* Thrown object must be a Throwable. */
295 error ("type %qT is not derived from %<java::lang::Throwable%>",
304 /* Select the personality routine to be used for exception handling,
305 or issue an error if we need two different ones in the same
307 ??? At present eh_personality_decl is set to
308 __gxx_personality_(sj|v)0 in init_exception_processing - should it
309 be done here instead? */
311 choose_personality_routine (enum languages lang)
326 if (lang != lang_cplusplus)
331 if (lang != lang_java)
336 ; /* Proceed to language selection. */
347 terminate_node = built_in_decls [BUILT_IN_ABORT];
348 pragma_java_exceptions = true;
357 error ("mixing C++ and Java catches in a single translation unit");
361 /* Initialize the catch parameter DECL. */
364 initialize_handler_parm (tree decl, tree exp)
369 /* Make sure we mark the catch param as used, otherwise we'll get a
370 warning about an unused ((anonymous)). */
371 TREE_USED (decl) = 1;
372 DECL_READ_P (decl) = 1;
374 /* Figure out the type that the initializer is. Pointers are returned
375 adjusted by value from __cxa_begin_catch. Others are returned by
377 init_type = TREE_TYPE (decl);
378 if (!POINTER_TYPE_P (init_type))
379 init_type = build_reference_type (init_type);
381 choose_personality_routine (decl_is_java_type (init_type, 0)
382 ? lang_java : lang_cplusplus);
384 /* Since pointers are passed by value, initialize a reference to
385 pointer catch parm with the address of the temporary. */
386 if (TREE_CODE (init_type) == REFERENCE_TYPE
387 && TYPE_PTR_P (TREE_TYPE (init_type)))
388 exp = cp_build_unary_op (ADDR_EXPR, exp, 1, tf_warning_or_error);
390 exp = ocp_convert (init_type, exp, CONV_IMPLICIT|CONV_FORCE_TEMP, 0);
392 init = convert_from_reference (exp);
394 /* If the constructor for the catch parm exits via an exception, we
395 must call terminate. See eh23.C. */
396 if (TYPE_NEEDS_CONSTRUCTING (TREE_TYPE (decl)))
398 /* Generate the copy constructor call directly so we can wrap it.
399 See also expand_default_init. */
400 init = ocp_convert (TREE_TYPE (decl), init,
401 CONV_IMPLICIT|CONV_FORCE_TEMP, 0);
402 /* Force cleanups now to avoid nesting problems with the
403 MUST_NOT_THROW_EXPR. */
404 init = fold_build_cleanup_point_expr (TREE_TYPE (init), init);
405 init = build1 (MUST_NOT_THROW_EXPR, TREE_TYPE (init), init);
408 decl = pushdecl (decl);
410 start_decl_1 (decl, true);
411 cp_finish_decl (decl, init, /*init_const_expr_p=*/false, NULL_TREE,
412 LOOKUP_ONLYCONVERTING|DIRECT_BIND);
415 /* Call this to start a catch block. DECL is the catch parameter. */
418 expand_start_catch_block (tree decl)
426 /* Make sure this declaration is reasonable. */
427 if (decl && !complete_ptr_ref_or_void_ptr_p (TREE_TYPE (decl), NULL_TREE))
428 decl = error_mark_node;
431 type = prepare_eh_type (TREE_TYPE (decl));
435 if (decl && decl_is_java_type (type, 1))
437 /* Java only passes object via pointer and doesn't require
438 adjusting. The java object is immediately before the
439 generic exception header. */
440 exp = build_exc_ptr ();
441 exp = build1 (NOP_EXPR, build_pointer_type (type), exp);
442 exp = build2 (POINTER_PLUS_EXPR, TREE_TYPE (exp), exp,
443 fold_build1_loc (input_location,
444 NEGATE_EXPR, sizetype,
445 TYPE_SIZE_UNIT (TREE_TYPE (exp))));
446 exp = cp_build_indirect_ref (exp, RO_NULL, tf_warning_or_error);
447 initialize_handler_parm (decl, exp);
451 /* Call __cxa_end_catch at the end of processing the exception. */
452 push_eh_cleanup (type);
454 init = do_begin_catch ();
456 /* If there's no decl at all, then all we need to do is make sure
457 to tell the runtime that we've begun handling the exception. */
458 if (decl == NULL || decl == error_mark_node || init == error_mark_node)
459 finish_expr_stmt (init);
461 /* If the C++ object needs constructing, we need to do that before
462 calling __cxa_begin_catch, so that std::uncaught_exception gets
463 the right value during the copy constructor. */
464 else if (flag_use_cxa_get_exception_ptr
465 && TYPE_NEEDS_CONSTRUCTING (TREE_TYPE (decl)))
467 exp = do_get_exception_ptr ();
468 initialize_handler_parm (decl, exp);
469 finish_expr_stmt (init);
472 /* Otherwise the type uses a bitwise copy, and we don't have to worry
473 about the value of std::uncaught_exception and therefore can do the
474 copy with the return value of __cxa_end_catch instead. */
477 tree init_type = type;
479 /* Pointers are passed by values, everything else by reference. */
480 if (!TYPE_PTR_P (type))
481 init_type = build_pointer_type (type);
482 if (init_type != TREE_TYPE (init))
483 init = build1 (NOP_EXPR, init_type, init);
484 exp = create_temporary_var (init_type);
485 DECL_REGISTER (exp) = 1;
486 cp_finish_decl (exp, init, /*init_const_expr=*/false,
487 NULL_TREE, LOOKUP_ONLYCONVERTING);
488 initialize_handler_parm (decl, exp);
495 /* Call this to end a catch block. Its responsible for emitting the
496 code to handle jumping back to the correct place, and for emitting
497 the label to jump to if this catch block didn't match. */
500 expand_end_catch_block (void)
505 /* The exception being handled is rethrown if control reaches the end of
506 a handler of the function-try-block of a constructor or destructor. */
507 if (in_function_try_handler
508 && (DECL_CONSTRUCTOR_P (current_function_decl)
509 || DECL_DESTRUCTOR_P (current_function_decl)))
510 finish_expr_stmt (build_throw (NULL_TREE));
514 begin_eh_spec_block (void)
516 tree r = build_stmt (input_location, EH_SPEC_BLOCK, NULL_TREE, NULL_TREE);
518 EH_SPEC_STMTS (r) = push_stmt_list ();
523 finish_eh_spec_block (tree raw_raises, tree eh_spec_block)
527 EH_SPEC_STMTS (eh_spec_block) = pop_stmt_list (EH_SPEC_STMTS (eh_spec_block));
529 /* Strip cv quals, etc, from the specification types. */
530 for (raises = NULL_TREE;
531 raw_raises && TREE_VALUE (raw_raises);
532 raw_raises = TREE_CHAIN (raw_raises))
534 tree type = prepare_eh_type (TREE_VALUE (raw_raises));
535 tree tinfo = eh_type_info (type);
538 raises = tree_cons (NULL_TREE, type, raises);
541 EH_SPEC_RAISES (eh_spec_block) = raises;
544 /* Return a pointer to a buffer for an exception object of type TYPE. */
547 do_allocate_exception (tree type)
551 fn = get_identifier ("__cxa_allocate_exception");
552 if (!get_global_value_if_present (fn, &fn))
554 /* Declare void *__cxa_allocate_exception(size_t) throw(). */
555 fn = declare_nothrow_library_fn (fn, ptr_type_node, size_type_node);
558 return cp_build_function_call (fn,
559 tree_cons (NULL_TREE, size_in_bytes (type),
561 tf_warning_or_error);
564 /* Call __cxa_free_exception from a cleanup. This is never invoked
565 directly, but see the comment for stabilize_throw_expr. */
568 do_free_exception (tree ptr)
572 fn = get_identifier ("__cxa_free_exception");
573 if (!get_global_value_if_present (fn, &fn))
575 /* Declare void __cxa_free_exception (void *) throw(). */
576 fn = declare_nothrow_library_fn (fn, void_type_node, ptr_type_node);
579 return cp_build_function_call (fn, tree_cons (NULL_TREE, ptr, NULL_TREE),
580 tf_warning_or_error);
583 /* Wrap all cleanups for TARGET_EXPRs in MUST_NOT_THROW_EXPR.
584 Called from build_throw via walk_tree_without_duplicates. */
587 wrap_cleanups_r (tree *tp, int *walk_subtrees ATTRIBUTE_UNUSED,
588 void *data ATTRIBUTE_UNUSED)
593 /* Don't walk into types. */
599 if (TREE_CODE (exp) != TARGET_EXPR)
602 cleanup = TARGET_EXPR_CLEANUP (exp);
605 cleanup = build1 (MUST_NOT_THROW_EXPR, void_type_node, cleanup);
606 TARGET_EXPR_CLEANUP (exp) = cleanup;
609 /* Keep iterating. */
613 /* Build a throw expression. */
616 build_throw (tree exp)
620 if (exp == error_mark_node)
623 if (processing_template_decl)
626 current_function_returns_abnormally = 1;
627 return build_min (THROW_EXPR, void_type_node, exp);
630 if (exp == null_node)
631 warning (0, "throwing NULL, which has integral, not pointer type");
633 if (exp != NULL_TREE)
635 if (!is_admissible_throw_operand (exp))
636 return error_mark_node;
640 return error_mark_node;
642 if (exp && decl_is_java_type (TREE_TYPE (exp), 1))
644 tree fn = get_identifier ("_Jv_Throw");
645 if (!get_global_value_if_present (fn, &fn))
647 /* Declare void _Jv_Throw (void *). */
648 tree tmp = tree_cons (NULL_TREE, ptr_type_node, void_list_node);
649 tmp = build_function_type (ptr_type_node, tmp);
650 fn = push_throw_library_fn (fn, tmp);
652 else if (really_overloaded_fn (fn))
654 error ("%qD should never be overloaded", fn);
655 return error_mark_node;
657 fn = OVL_CURRENT (fn);
658 exp = cp_build_function_call (fn, tree_cons (NULL_TREE, exp, NULL_TREE),
659 tf_warning_or_error);
670 /* The CLEANUP_TYPE is the internal type of a destructor. */
673 tmp = void_list_node;
674 tmp = tree_cons (NULL_TREE, ptr_type_node, tmp);
675 tmp = build_function_type (void_type_node, tmp);
676 cleanup_type = build_pointer_type (tmp);
679 fn = get_identifier ("__cxa_throw");
680 if (!get_global_value_if_present (fn, &fn))
682 /* Declare void __cxa_throw (void*, void*, void (*)(void*)). */
683 /* ??? Second argument is supposed to be "std::type_info*". */
684 tmp = void_list_node;
685 tmp = tree_cons (NULL_TREE, cleanup_type, tmp);
686 tmp = tree_cons (NULL_TREE, ptr_type_node, tmp);
687 tmp = tree_cons (NULL_TREE, ptr_type_node, tmp);
688 tmp = build_function_type (void_type_node, tmp);
689 fn = push_throw_library_fn (fn, tmp);
694 A throw-expression initializes a temporary object, the type
695 of which is determined by removing any top-level
696 cv-qualifiers from the static type of the operand of throw
697 and adjusting the type from "array of T" or "function return
698 T" to "pointer to T" or "pointer to function returning T"
700 temp_type = is_bitfield_expr_with_lowered_type (exp);
702 temp_type = type_decays_to (TREE_TYPE (exp));
704 /* OK, this is kind of wacky. The standard says that we call
705 terminate when the exception handling mechanism, after
706 completing evaluation of the expression to be thrown but
707 before the exception is caught (_except.throw_), calls a
708 user function that exits via an uncaught exception.
710 So we have to protect the actual initialization of the
711 exception object with terminate(), but evaluate the
712 expression first. Since there could be temps in the
713 expression, we need to handle that, too. We also expand
714 the call to __cxa_allocate_exception first (which doesn't
715 matter, since it can't throw). */
717 /* Allocate the space for the exception. */
718 allocate_expr = do_allocate_exception (temp_type);
719 allocate_expr = get_target_expr (allocate_expr);
720 ptr = TARGET_EXPR_SLOT (allocate_expr);
721 TARGET_EXPR_CLEANUP (allocate_expr) = do_free_exception (ptr);
722 CLEANUP_EH_ONLY (allocate_expr) = 1;
724 object = build_nop (build_pointer_type (temp_type), ptr);
725 object = cp_build_indirect_ref (object, RO_NULL, tf_warning_or_error);
727 /* And initialize the exception object. */
728 if (CLASS_TYPE_P (temp_type))
730 int flags = LOOKUP_NORMAL | LOOKUP_ONLYCONVERTING;
731 VEC(tree,gc) *exp_vec;
733 /* Under C++0x [12.8/16 class.copy], a thrown lvalue is sometimes
734 treated as an rvalue for the purposes of overload resolution
735 to favor move constructors over copy constructors. */
736 if (/* Must be a local, automatic variable. */
737 TREE_CODE (exp) == VAR_DECL
738 && DECL_CONTEXT (exp) == current_function_decl
739 && ! TREE_STATIC (exp)
740 /* The variable must not have the `volatile' qualifier. */
741 && !(cp_type_quals (TREE_TYPE (exp)) & TYPE_QUAL_VOLATILE))
742 flags = flags | LOOKUP_PREFER_RVALUE;
744 /* Call the copy constructor. */
745 exp_vec = make_tree_vector_single (exp);
746 exp = (build_special_member_call
747 (object, complete_ctor_identifier, &exp_vec,
748 TREE_TYPE (object), flags, tf_warning_or_error));
749 release_tree_vector (exp_vec);
750 if (exp == error_mark_node)
752 error (" in thrown expression");
753 return error_mark_node;
758 tmp = decay_conversion (exp);
759 if (tmp == error_mark_node)
760 return error_mark_node;
761 exp = build2 (INIT_EXPR, temp_type, object, tmp);
764 /* Mark any cleanups from the initialization as MUST_NOT_THROW, since
765 they are run after the exception object is initialized. */
766 cp_walk_tree_without_duplicates (&exp, wrap_cleanups_r, 0);
768 /* Prepend the allocation. */
769 exp = build2 (COMPOUND_EXPR, TREE_TYPE (exp), allocate_expr, exp);
771 /* Force all the cleanups to be evaluated here so that we don't have
772 to do them during unwinding. */
773 exp = build1 (CLEANUP_POINT_EXPR, void_type_node, exp);
775 throw_type = build_eh_type_type (prepare_eh_type (TREE_TYPE (object)));
777 if (TYPE_HAS_NONTRIVIAL_DESTRUCTOR (TREE_TYPE (object)))
779 cleanup = lookup_fnfields (TYPE_BINFO (TREE_TYPE (object)),
780 complete_dtor_identifier, 0);
781 cleanup = BASELINK_FUNCTIONS (cleanup);
783 cxx_mark_addressable (cleanup);
784 /* Pretend it's a normal function. */
785 cleanup = build1 (ADDR_EXPR, cleanup_type, cleanup);
788 cleanup = build_int_cst (cleanup_type, 0);
790 tmp = tree_cons (NULL_TREE, cleanup, NULL_TREE);
791 tmp = tree_cons (NULL_TREE, throw_type, tmp);
792 tmp = tree_cons (NULL_TREE, ptr, tmp);
793 /* ??? Indicate that this function call throws throw_type. */
794 tmp = cp_build_function_call (fn, tmp, tf_warning_or_error);
796 /* Tack on the initialization stuff. */
797 exp = build2 (COMPOUND_EXPR, TREE_TYPE (tmp), exp, tmp);
801 /* Rethrow current exception. */
803 tree fn = get_identifier ("__cxa_rethrow");
804 if (!get_global_value_if_present (fn, &fn))
806 /* Declare void __cxa_rethrow (void). */
807 fn = push_throw_library_fn
808 (fn, build_function_type (void_type_node, void_list_node));
811 /* ??? Indicate that this function call allows exceptions of the type
812 of the enclosing catch block (if known). */
813 exp = cp_build_function_call (fn, NULL_TREE, tf_warning_or_error);
816 exp = build1 (THROW_EXPR, void_type_node, exp);
821 /* Make sure TYPE is complete, pointer to complete, reference to
822 complete, or pointer to cv void. Issue diagnostic on failure.
823 Return the zero on failure and nonzero on success. FROM can be
824 the expr or decl from whence TYPE came, if available. */
827 complete_ptr_ref_or_void_ptr_p (tree type, tree from)
831 /* Check complete. */
832 type = complete_type_or_else (type, from);
836 /* Or a pointer or ref to one, or cv void *. */
837 is_ptr = TREE_CODE (type) == POINTER_TYPE;
838 if (is_ptr || TREE_CODE (type) == REFERENCE_TYPE)
840 tree core = TREE_TYPE (type);
842 if (is_ptr && VOID_TYPE_P (core))
844 else if (!complete_type_or_else (core, from))
850 /* Return truth-value if EXPRESSION is admissible in throw-expression,
851 i.e. if it is not of incomplete type or a pointer/reference to such
852 a type or of an abstract class type. */
855 is_admissible_throw_operand (tree expr)
857 tree type = TREE_TYPE (expr);
859 /* 15.1/4 [...] The type of the throw-expression shall not be an
860 incomplete type, or a pointer or a reference to an incomplete
861 type, other than void*, const void*, volatile void*, or
862 const volatile void*. Except for these restriction and the
863 restrictions on type matching mentioned in 15.3, the operand
864 of throw is treated exactly as a function argument in a call
865 (5.2.2) or the operand of a return statement. */
866 if (!complete_ptr_ref_or_void_ptr_p (type, expr))
869 /* 10.4/3 An abstract class shall not be used as a parameter type,
870 as a function return type or as type of an explicit
872 else if (CLASS_TYPE_P (type) && CLASSTYPE_PURE_VIRTUALS (type))
874 error ("expression %qE of abstract class type %qT cannot "
875 "be used in throw-expression", expr, type);
882 /* Returns nonzero if FN is a declaration of a standard C library
883 function which is known not to throw.
885 [lib.res.on.exception.handling]: None of the functions from the
886 Standard C library shall report an error by throwing an
887 exception, unless it calls a program-supplied function that
888 throws an exception. */
893 nothrow_libfn_p (const_tree fn)
898 && DECL_EXTERNAL (fn)
899 && DECL_NAMESPACE_SCOPE_P (fn)
900 && DECL_EXTERN_C_P (fn))
903 /* Can't be a C library function. */
906 /* Being a C library function, DECL_ASSEMBLER_NAME == DECL_NAME
907 unless the system headers are playing rename tricks, and if
908 they are, we don't want to be confused by them. */
910 return !!libc_name_p (IDENTIFIER_POINTER (id), IDENTIFIER_LENGTH (id));
913 /* Returns nonzero if an exception of type FROM will be caught by a
914 handler for type TO, as per [except.handle]. */
917 can_convert_eh (tree to, tree from)
919 to = non_reference (to);
920 from = non_reference (from);
922 if (TREE_CODE (to) == POINTER_TYPE && TREE_CODE (from) == POINTER_TYPE)
925 from = TREE_TYPE (from);
927 if (! at_least_as_qualified_p (to, from))
930 if (TREE_CODE (to) == VOID_TYPE)
933 /* Else fall through. */
936 if (CLASS_TYPE_P (to) && CLASS_TYPE_P (from)
937 && PUBLICLY_UNIQUELY_DERIVED_P (to, from))
943 /* Check whether any of the handlers in I are shadowed by another handler
944 accepting TYPE. Note that the shadowing may not be complete; even if
945 an exception of type B would be caught by a handler for A, there could
946 be a derived class C for which A is an ambiguous base but B is not, so
947 the handler for B would catch an exception of type C. */
950 check_handlers_1 (tree master, tree_stmt_iterator i)
952 tree type = TREE_TYPE (master);
954 for (; !tsi_end_p (i); tsi_next (&i))
956 tree handler = tsi_stmt (i);
957 if (TREE_TYPE (handler) && can_convert_eh (type, TREE_TYPE (handler)))
959 warning_at (EXPR_LOCATION (handler), 0,
960 "exception of type %qT will be caught",
961 TREE_TYPE (handler));
962 warning_at (EXPR_LOCATION (master), 0,
963 " by earlier handler for %qT", type);
969 /* Given a STATEMENT_LIST of HANDLERs, make sure that they're OK. */
972 check_handlers (tree handlers)
974 tree_stmt_iterator i;
976 /* If we don't have a STATEMENT_LIST, then we've just got one
977 handler, and thus nothing to warn about. */
978 if (TREE_CODE (handlers) != STATEMENT_LIST)
981 i = tsi_start (handlers);
985 tree handler = tsi_stmt (i);
988 /* No more handlers; nothing to shadow. */
991 if (TREE_TYPE (handler) == NULL_TREE)
992 permerror (EXPR_LOCATION (handler), "%<...%>"
993 " handler must be the last handler for its try block");
995 check_handlers_1 (handler, i);