/* Handle exceptional things in C++. Copyright (C) 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc. Contributed by Michael Tiemann Rewritten by Mike Stump , based upon an initial re-implementation courtesy Tad Hunt. This file is part of GCC. GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GCC; see the file COPYING. If not, write to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ #include "config.h" #include "system.h" #include "coretypes.h" #include "tm.h" #include "tree.h" #include "rtl.h" #include "expr.h" #include "libfuncs.h" #include "cp-tree.h" #include "flags.h" #include "output.h" #include "except.h" #include "toplev.h" #include "tree-inline.h" static void push_eh_cleanup (tree); static tree prepare_eh_type (tree); static tree build_eh_type_type (tree); static tree do_begin_catch (void); static int dtor_nothrow (tree); static tree do_end_catch (tree); static bool decl_is_java_type (tree decl, int err); static void initialize_handler_parm (tree, tree); static tree do_allocate_exception (tree); static tree wrap_cleanups_r (tree *, int *, void *); static int complete_ptr_ref_or_void_ptr_p (tree, tree); static bool is_admissible_throw_operand (tree); static int can_convert_eh (tree, tree); static void check_handlers_1 (tree, tree); static tree cp_protect_cleanup_actions (void); /* Sets up all the global eh stuff that needs to be initialized at the start of compilation. */ void init_exception_processing (void) { tree tmp; /* void std::terminate (); */ push_namespace (std_identifier); tmp = build_function_type (void_type_node, void_list_node); terminate_node = build_cp_library_fn_ptr ("terminate", tmp); TREE_THIS_VOLATILE (terminate_node) = 1; TREE_NOTHROW (terminate_node) = 1; pop_namespace (); /* void __cxa_call_unexpected(void *); */ tmp = tree_cons (NULL_TREE, ptr_type_node, void_list_node); tmp = build_function_type (void_type_node, tmp); call_unexpected_node = push_throw_library_fn (get_identifier ("__cxa_call_unexpected"), tmp); eh_personality_libfunc = init_one_libfunc (USING_SJLJ_EXCEPTIONS ? "__gxx_personality_sj0" : "__gxx_personality_v0"); lang_eh_runtime_type = build_eh_type_type; lang_protect_cleanup_actions = &cp_protect_cleanup_actions; } /* Returns an expression to be executed if an unhandled exception is propagated out of a cleanup region. */ static tree cp_protect_cleanup_actions (void) { /* [except.terminate] When the destruction of an object during stack unwinding exits using an exception ... void terminate(); is called. */ return build_call (terminate_node, NULL_TREE); } static tree prepare_eh_type (tree type) { if (type == NULL_TREE) return type; if (type == error_mark_node) return error_mark_node; /* peel back references, so they match. */ type = non_reference (type); /* Peel off cv qualifiers. */ type = TYPE_MAIN_VARIANT (type); return type; } /* Return the type info for TYPE as used by EH machinery. */ tree eh_type_info (tree type) { tree exp; if (type == NULL_TREE || type == error_mark_node) return type; if (decl_is_java_type (type, 0)) exp = build_java_class_ref (TREE_TYPE (type)); else exp = get_tinfo_decl (type); return exp; } /* Build the address of a typeinfo decl for use in the runtime matching field of the exception model. */ static tree build_eh_type_type (tree type) { tree exp = eh_type_info (type); if (!exp) return NULL; mark_used (exp); return convert (ptr_type_node, build_address (exp)); } tree build_exc_ptr (void) { return build (EXC_PTR_EXPR, ptr_type_node); } /* Build up a call to __cxa_begin_catch, to tell the runtime that the exception has been handled. */ static tree do_begin_catch (void) { tree fn; fn = get_identifier ("__cxa_begin_catch"); if (!get_global_value_if_present (fn, &fn)) { /* Declare void* __cxa_begin_catch (void *). */ tree tmp = tree_cons (NULL_TREE, ptr_type_node, void_list_node); fn = push_library_fn (fn, build_function_type (ptr_type_node, tmp)); } return build_function_call (fn, tree_cons (NULL_TREE, build_exc_ptr (), NULL_TREE)); } /* Returns nonzero if cleaning up an exception of type TYPE (which can be NULL_TREE for a ... handler) will not throw an exception. */ static int dtor_nothrow (tree type) { if (type == NULL_TREE) return 0; if (! TYPE_HAS_DESTRUCTOR (type)) return 1; return TREE_NOTHROW (CLASSTYPE_DESTRUCTORS (type)); } /* Build up a call to __cxa_end_catch, to destroy the exception object for the current catch block if no others are currently using it. */ static tree do_end_catch (tree type) { tree fn, cleanup; fn = get_identifier ("__cxa_end_catch"); if (!get_global_value_if_present (fn, &fn)) { /* Declare void __cxa_end_catch (). */ fn = push_void_library_fn (fn, void_list_node); /* This can throw if the destructor for the exception throws. */ TREE_NOTHROW (fn) = 0; } cleanup = build_function_call (fn, NULL_TREE); TREE_NOTHROW (cleanup) = dtor_nothrow (type); return cleanup; } /* This routine creates the cleanup for the current exception. */ static void push_eh_cleanup (tree type) { finish_decl_cleanup (NULL_TREE, do_end_catch (type)); } /* Return nonzero value if DECL is a Java type suitable for catch or throw. */ static bool decl_is_java_type (tree decl, int err) { bool r = (TREE_CODE (decl) == POINTER_TYPE && TREE_CODE (TREE_TYPE (decl)) == RECORD_TYPE && TYPE_FOR_JAVA (TREE_TYPE (decl))); if (err) { if (TREE_CODE (decl) == REFERENCE_TYPE && TREE_CODE (TREE_TYPE (decl)) == RECORD_TYPE && TYPE_FOR_JAVA (TREE_TYPE (decl))) { /* Can't throw a reference. */ error ("type `%T' is disallowed in Java `throw' or `catch'", decl); } if (r) { tree jthrow_node = IDENTIFIER_GLOBAL_VALUE (get_identifier ("jthrowable")); if (jthrow_node == NULL_TREE) fatal_error ("call to Java `catch' or `throw' with `jthrowable' undefined"); jthrow_node = TREE_TYPE (TREE_TYPE (jthrow_node)); if (! DERIVED_FROM_P (jthrow_node, TREE_TYPE (decl))) { /* Thrown object must be a Throwable. */ error ("type `%T' is not derived from `java::lang::Throwable'", TREE_TYPE (decl)); } } } return r; } /* Select the personality routine to be used for exception handling, or issue an error if we need two different ones in the same translation unit. ??? At present eh_personality_libfunc is set to __gxx_personality_(sj|v)0 in init_exception_processing - should it be done here instead? */ void choose_personality_routine (enum languages lang) { static enum { chose_none, chose_cpp, chose_java, gave_error } state; switch (state) { case gave_error: return; case chose_cpp: if (lang != lang_cplusplus) goto give_error; return; case chose_java: if (lang != lang_java) goto give_error; return; case chose_none: ; /* Proceed to language selection. */ } switch (lang) { case lang_cplusplus: state = chose_cpp; break; case lang_java: state = chose_java; eh_personality_libfunc = init_one_libfunc (USING_SJLJ_EXCEPTIONS ? "__gcj_personality_sj0" : "__gcj_personality_v0"); break; default: abort (); } return; give_error: error ("mixing C++ and Java catches in a single translation unit"); state = gave_error; } /* Initialize the catch parameter DECL. */ static void initialize_handler_parm (tree decl, tree exp) { tree init; tree init_type; /* Make sure we mark the catch param as used, otherwise we'll get a warning about an unused ((anonymous)). */ TREE_USED (decl) = 1; /* Figure out the type that the initializer is. Pointers are returned adjusted by value from __cxa_begin_catch. Others are returned by reference. */ init_type = TREE_TYPE (decl); if (! TYPE_PTR_P (init_type) && TREE_CODE (init_type) != REFERENCE_TYPE) init_type = build_reference_type (init_type); choose_personality_routine (decl_is_java_type (init_type, 0) ? lang_java : lang_cplusplus); /* Since pointers are passed by value, initialize a reference to pointer catch parm with the address of the temporary. */ if (TREE_CODE (init_type) == REFERENCE_TYPE && TYPE_PTR_P (TREE_TYPE (init_type))) exp = build_unary_op (ADDR_EXPR, exp, 1); exp = ocp_convert (init_type, exp, CONV_IMPLICIT|CONV_FORCE_TEMP, 0); init = convert_from_reference (exp); /* If the constructor for the catch parm exits via an exception, we must call terminate. See eh23.C. */ if (TYPE_NEEDS_CONSTRUCTING (TREE_TYPE (decl))) { /* Generate the copy constructor call directly so we can wrap it. See also expand_default_init. */ init = ocp_convert (TREE_TYPE (decl), init, CONV_IMPLICIT|CONV_FORCE_TEMP, 0); init = build1 (MUST_NOT_THROW_EXPR, TREE_TYPE (init), init); } /* Let `cp_finish_decl' know that this initializer is ok. */ DECL_INITIAL (decl) = error_mark_node; decl = pushdecl (decl); start_decl_1 (decl); cp_finish_decl (decl, init, NULL_TREE, LOOKUP_ONLYCONVERTING|DIRECT_BIND); } /* Call this to start a catch block. DECL is the catch parameter. */ tree expand_start_catch_block (tree decl) { tree exp = NULL_TREE; tree type; bool is_java; if (! doing_eh (1)) return NULL_TREE; /* Make sure this declaration is reasonable. */ if (decl && !complete_ptr_ref_or_void_ptr_p (TREE_TYPE (decl), NULL_TREE)) decl = NULL_TREE; if (decl) type = prepare_eh_type (TREE_TYPE (decl)); else type = NULL_TREE; is_java = false; if (decl) { tree init; if (decl_is_java_type (type, 1)) { /* Java only passes object via pointer and doesn't require adjusting. The java object is immediately before the generic exception header. */ init = build_exc_ptr (); init = build1 (NOP_EXPR, build_pointer_type (type), init); init = build (MINUS_EXPR, TREE_TYPE (init), init, TYPE_SIZE_UNIT (TREE_TYPE (init))); init = build_indirect_ref (init, NULL); is_java = true; } else { /* C++ requires that we call __cxa_begin_catch to get the pointer to the actual object. */ init = do_begin_catch (); } exp = create_temporary_var (ptr_type_node); DECL_REGISTER (exp) = 1; cp_finish_decl (exp, init, NULL_TREE, LOOKUP_ONLYCONVERTING); finish_expr_stmt (build_modify_expr (exp, INIT_EXPR, init)); } else finish_expr_stmt (do_begin_catch ()); /* C++ requires that we call __cxa_end_catch at the end of processing the exception. */ if (! is_java) push_eh_cleanup (type); if (decl) initialize_handler_parm (decl, exp); return type; } /* Call this to end a catch block. Its responsible for emitting the code to handle jumping back to the correct place, and for emitting the label to jump to if this catch block didn't match. */ void expand_end_catch_block (void) { if (! doing_eh (1)) return; /* The exception being handled is rethrown if control reaches the end of a handler of the function-try-block of a constructor or destructor. */ if (in_function_try_handler && (DECL_CONSTRUCTOR_P (current_function_decl) || DECL_DESTRUCTOR_P (current_function_decl))) finish_expr_stmt (build_throw (NULL_TREE)); } tree begin_eh_spec_block (void) { tree r = build_stmt (EH_SPEC_BLOCK, NULL_TREE, NULL_TREE); add_stmt (r); return r; } void finish_eh_spec_block (tree raw_raises, tree eh_spec_block) { tree raises; RECHAIN_STMTS (eh_spec_block, EH_SPEC_STMTS (eh_spec_block)); /* Strip cv quals, etc, from the specification types. */ for (raises = NULL_TREE; raw_raises && TREE_VALUE (raw_raises); raw_raises = TREE_CHAIN (raw_raises)) { tree type = prepare_eh_type (TREE_VALUE (raw_raises)); tree tinfo = eh_type_info (type); mark_used (tinfo); raises = tree_cons (NULL_TREE, type, raises); } EH_SPEC_RAISES (eh_spec_block) = raises; } /* Return a pointer to a buffer for an exception object of type TYPE. */ static tree do_allocate_exception (tree type) { tree fn; fn = get_identifier ("__cxa_allocate_exception"); if (!get_global_value_if_present (fn, &fn)) { /* Declare void *__cxa_allocate_exception(size_t). */ tree tmp = tree_cons (NULL_TREE, size_type_node, void_list_node); fn = push_library_fn (fn, build_function_type (ptr_type_node, tmp)); } return build_function_call (fn, tree_cons (NULL_TREE, size_in_bytes (type), NULL_TREE)); } /* Call __cxa_free_exception from a cleanup. This is never invoked directly, but see the comment for stabilize_throw_expr. */ static tree do_free_exception (tree ptr) { tree fn; fn = get_identifier ("__cxa_free_exception"); if (!get_global_value_if_present (fn, &fn)) { /* Declare void __cxa_free_exception (void *). */ fn = push_void_library_fn (fn, tree_cons (NULL_TREE, ptr_type_node, void_list_node)); } return build_function_call (fn, tree_cons (NULL_TREE, ptr, NULL_TREE)); } /* Wrap all cleanups for TARGET_EXPRs in MUST_NOT_THROW_EXPR. Called from build_throw via walk_tree_without_duplicates. */ static tree wrap_cleanups_r (tree *tp, int *walk_subtrees ATTRIBUTE_UNUSED, void *data ATTRIBUTE_UNUSED) { tree exp = *tp; tree cleanup; /* Don't walk into types. */ if (TYPE_P (exp)) { *walk_subtrees = 0; return NULL_TREE; } if (TREE_CODE (exp) != TARGET_EXPR) return NULL_TREE; cleanup = TARGET_EXPR_CLEANUP (exp); if (cleanup) { cleanup = build1 (MUST_NOT_THROW_EXPR, void_type_node, cleanup); TARGET_EXPR_CLEANUP (exp) = cleanup; } /* Keep iterating. */ return NULL_TREE; } /* Build a throw expression. */ tree build_throw (tree exp) { tree fn; if (exp == error_mark_node) return exp; if (processing_template_decl) { current_function_returns_abnormally = 1; return build_min (THROW_EXPR, void_type_node, exp); } if (exp == null_node) warning ("throwing NULL, which has integral, not pointer type"); if (exp != NULL_TREE) { if (!is_admissible_throw_operand (exp)) return error_mark_node; } if (! doing_eh (1)) return error_mark_node; if (exp && decl_is_java_type (TREE_TYPE (exp), 1)) { tree fn = get_identifier ("_Jv_Throw"); if (!get_global_value_if_present (fn, &fn)) { /* Declare void _Jv_Throw (void *). */ tree tmp = tree_cons (NULL_TREE, ptr_type_node, void_list_node); tmp = build_function_type (ptr_type_node, tmp); fn = push_throw_library_fn (fn, tmp); } else if (really_overloaded_fn (fn)) { error ("`%D' should never be overloaded", fn); return error_mark_node; } fn = OVL_CURRENT (fn); exp = build_function_call (fn, tree_cons (NULL_TREE, exp, NULL_TREE)); } else if (exp) { tree throw_type; tree cleanup; tree object, ptr; tree tmp; tree temp_expr, allocate_expr; bool elided; fn = get_identifier ("__cxa_throw"); if (!get_global_value_if_present (fn, &fn)) { /* The CLEANUP_TYPE is the internal type of a destructor. */ if (cleanup_type == NULL_TREE) { tmp = void_list_node; tmp = tree_cons (NULL_TREE, ptr_type_node, tmp); tmp = build_function_type (void_type_node, tmp); cleanup_type = build_pointer_type (tmp); } /* Declare void __cxa_throw (void*, void*, void (*)(void*)). */ /* ??? Second argument is supposed to be "std::type_info*". */ tmp = void_list_node; tmp = tree_cons (NULL_TREE, cleanup_type, tmp); tmp = tree_cons (NULL_TREE, ptr_type_node, tmp); tmp = tree_cons (NULL_TREE, ptr_type_node, tmp); tmp = build_function_type (void_type_node, tmp); fn = push_throw_library_fn (fn, tmp); } /* throw expression */ /* First, decay it. */ exp = decay_conversion (exp); /* OK, this is kind of wacky. The standard says that we call terminate when the exception handling mechanism, after completing evaluation of the expression to be thrown but before the exception is caught (_except.throw_), calls a user function that exits via an uncaught exception. So we have to protect the actual initialization of the exception object with terminate(), but evaluate the expression first. Since there could be temps in the expression, we need to handle that, too. We also expand the call to __cxa_allocate_exception first (which doesn't matter, since it can't throw). */ /* Allocate the space for the exception. */ allocate_expr = do_allocate_exception (TREE_TYPE (exp)); allocate_expr = get_target_expr (allocate_expr); ptr = TARGET_EXPR_SLOT (allocate_expr); object = build1 (NOP_EXPR, build_pointer_type (TREE_TYPE (exp)), ptr); object = build_indirect_ref (object, NULL); elided = (TREE_CODE (exp) == TARGET_EXPR); /* And initialize the exception object. */ exp = build_init (object, exp, LOOKUP_ONLYCONVERTING); if (exp == error_mark_node) { error (" in thrown expression"); return error_mark_node; } /* Pre-evaluate the thrown expression first, since if we allocated the space first we would have to deal with cleaning it up if evaluating this expression throws. The case where EXP the initializer is a call to a constructor or a function returning a class is a bit of a grey area in the standard; it's unclear whether or not it should be allowed to throw. We used to say no, as that allowed us to optimize this case without worrying about deallocating the exception object if it does. But that conflicted with expectations (PR 13944) and the EDG compiler; now we wrap the initialization in a TRY_CATCH_EXPR to call do_free_exception rather than in a MUST_NOT_THROW_EXPR, for this case only. Note that we don't check the return value from stabilize_init because it will only return false in cases where elided is true, and therefore we don't need to work around the failure to preevaluate. */ stabilize_init (exp, &temp_expr); if (elided) exp = build (TRY_CATCH_EXPR, void_type_node, exp, do_free_exception (ptr)); else exp = build1 (MUST_NOT_THROW_EXPR, void_type_node, exp); /* Prepend the allocation. */ exp = build (COMPOUND_EXPR, TREE_TYPE (exp), allocate_expr, exp); if (temp_expr) { /* Prepend the calculation of the throw expression. Also, force any cleanups from the expression to be evaluated here so that we don't have to do them during unwinding. But first wrap them in MUST_NOT_THROW_EXPR, since they are run after the exception object is initialized. */ walk_tree_without_duplicates (&temp_expr, wrap_cleanups_r, 0); exp = build (COMPOUND_EXPR, TREE_TYPE (exp), temp_expr, exp); exp = build1 (CLEANUP_POINT_EXPR, TREE_TYPE (exp), exp); } throw_type = build_eh_type_type (prepare_eh_type (TREE_TYPE (object))); if (TYPE_HAS_DESTRUCTOR (TREE_TYPE (object))) { cleanup = lookup_fnfields (TYPE_BINFO (TREE_TYPE (object)), complete_dtor_identifier, 0); cleanup = BASELINK_FUNCTIONS (cleanup); mark_used (cleanup); cxx_mark_addressable (cleanup); /* Pretend it's a normal function. */ cleanup = build1 (ADDR_EXPR, cleanup_type, cleanup); } else { cleanup = build_int_2 (0, 0); TREE_TYPE (cleanup) = cleanup_type; } tmp = tree_cons (NULL_TREE, cleanup, NULL_TREE); tmp = tree_cons (NULL_TREE, throw_type, tmp); tmp = tree_cons (NULL_TREE, ptr, tmp); /* ??? Indicate that this function call throws throw_type. */ tmp = build_function_call (fn, tmp); /* Tack on the initialization stuff. */ exp = build (COMPOUND_EXPR, TREE_TYPE (tmp), exp, tmp); } else { /* Rethrow current exception. */ tree fn = get_identifier ("__cxa_rethrow"); if (!get_global_value_if_present (fn, &fn)) { /* Declare void __cxa_rethrow (void). */ fn = push_throw_library_fn (fn, build_function_type (void_type_node, void_list_node)); } /* ??? Indicate that this function call allows exceptions of the type of the enclosing catch block (if known). */ exp = build_function_call (fn, NULL_TREE); } exp = build1 (THROW_EXPR, void_type_node, exp); return exp; } /* Make sure TYPE is complete, pointer to complete, reference to complete, or pointer to cv void. Issue diagnostic on failure. Return the zero on failure and nonzero on success. FROM can be the expr or decl from whence TYPE came, if available. */ static int complete_ptr_ref_or_void_ptr_p (tree type, tree from) { int is_ptr; /* Check complete. */ type = complete_type_or_else (type, from); if (!type) return 0; /* Or a pointer or ref to one, or cv void *. */ is_ptr = TREE_CODE (type) == POINTER_TYPE; if (is_ptr || TREE_CODE (type) == REFERENCE_TYPE) { tree core = TREE_TYPE (type); if (is_ptr && VOID_TYPE_P (core)) /* OK */; else if (!complete_type_or_else (core, from)) return 0; } return 1; } /* Return truth-value if EXPRESSION is admissible in throw-expression, i.e. if it is not of incomplete type or a pointer/reference to such a type or of an abstract class type. */ static bool is_admissible_throw_operand (tree expr) { tree type = TREE_TYPE (expr); /* 15.1/4 [...] The type of the throw-expression shall not be an incomplete type, or a pointer or a reference to an incomplete type, other than void*, const void*, volatile void*, or const volatile void*. Except for these restriction and the restrictions on type matching mentioned in 15.3, the operand of throw is treated exactly as a function argument in a call (5.2.2) or the operand of a return statement. */ if (!complete_ptr_ref_or_void_ptr_p (type, expr)) return false; /* 10.4/3 An abstract class shall not be used as a parameter type, as a function return type or as type of an explicit conversion. */ else if (CLASS_TYPE_P (type) && CLASSTYPE_PURE_VIRTUALS (type)) { error ("expression '%E' of abstract class type '%T' cannot be used in throw-expression", expr, type); return false; } return true; } /* Returns nonzero if FN is a declaration of a standard C library function which is known not to throw. [lib.res.on.exception.handling]: None of the functions from the Standard C library shall report an error by throwing an exception, unless it calls a program-supplied function that throws an exception. */ #include "cfns.h" int nothrow_libfn_p (tree fn) { tree id; if (TREE_PUBLIC (fn) && DECL_EXTERNAL (fn) && DECL_NAMESPACE_SCOPE_P (fn) && DECL_EXTERN_C_P (fn)) /* OK */; else /* Can't be a C library function. */ return 0; id = DECL_ASSEMBLER_NAME (fn); return !!libc_name_p (IDENTIFIER_POINTER (id), IDENTIFIER_LENGTH (id)); } /* Returns nonzero if an exception of type FROM will be caught by a handler for type TO, as per [except.handle]. */ static int can_convert_eh (tree to, tree from) { to = non_reference (to); from = non_reference (from); if (TREE_CODE (to) == POINTER_TYPE && TREE_CODE (from) == POINTER_TYPE) { to = TREE_TYPE (to); from = TREE_TYPE (from); if (! at_least_as_qualified_p (to, from)) return 0; if (TREE_CODE (to) == VOID_TYPE) return 1; /* Else fall through. */ } if (CLASS_TYPE_P (to) && CLASS_TYPE_P (from) && PUBLICLY_UNIQUELY_DERIVED_P (to, from)) return 1; return 0; } /* Check whether any of HANDLERS are shadowed by another handler accepting TYPE. Note that the shadowing may not be complete; even if an exception of type B would be caught by a handler for A, there could be a derived class C for which A is an ambiguous base but B is not, so the handler for B would catch an exception of type C. */ static void check_handlers_1 (tree master, tree handlers) { tree type = TREE_TYPE (master); tree handler; for (handler = handlers; handler; handler = TREE_CHAIN (handler)) if (TREE_TYPE (handler) && can_convert_eh (type, TREE_TYPE (handler))) { warning ("%Hexception of type `%T' will be caught", EXPR_LOCUS (handler), TREE_TYPE (handler)); warning ("%H by earlier handler for `%T'", EXPR_LOCUS (master), type); break; } } /* Given a chain of HANDLERs, make sure that they're OK. */ void check_handlers (tree handlers) { tree handler; int save_line = input_line; for (handler = handlers; handler; handler = TREE_CHAIN (handler)) { if (TREE_CHAIN (handler) == NULL_TREE) /* No more handlers; nothing to shadow. */; else if (TREE_TYPE (handler) == NULL_TREE) pedwarn ("%H`...' handler must be the last handler for" " its try block", EXPR_LOCUS (handler)); else check_handlers_1 (handler, TREE_CHAIN (handler)); } input_line = save_line; }