Mercurial > hg > CbC > CbC_gcc
view gcc/cp/except.c @ 111:04ced10e8804
gcc 7
| author | kono |
|---|---|
| date | Fri, 27 Oct 2017 22:46:09 +0900 |
| parents | |
| children | 84e7813d76e9 |
line wrap: on
line source
/* Handle exceptional things in C++. Copyright (C) 1989-2017 Free Software Foundation, Inc. Contributed by Michael Tiemann <tiemann@cygnus.com> Rewritten by Mike Stump <mrs@cygnus.com>, 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 3, 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 COPYING3. If not see <http://www.gnu.org/licenses/>. */ #include "config.h" #include "system.h" #include "coretypes.h" #include "cp-tree.h" #include "stringpool.h" #include "trans-mem.h" #include "attribs.h" #include "tree-iterator.h" static void push_eh_cleanup (tree); static tree prepare_eh_type (tree); static tree do_begin_catch (void); static int dtor_nothrow (tree); static tree do_end_catch (tree); 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_or_catch_parameter (tree, bool); static int can_convert_eh (tree, tree); /* 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_list (void_type_node, NULL_TREE); terminate_fn = build_cp_library_fn_ptr ("terminate", tmp, ECF_NOTHROW | ECF_NORETURN | ECF_COLD); gcc_checking_assert (TREE_THIS_VOLATILE (terminate_fn) && TREE_NOTHROW (terminate_fn)); pop_namespace (); /* void __cxa_call_unexpected(void *); */ tmp = build_function_type_list (void_type_node, ptr_type_node, NULL_TREE); call_unexpected_fn = push_throw_library_fn (get_identifier ("__cxa_call_unexpected"), tmp); } /* Returns an expression to be executed if an unhandled exception is propagated out of a cleanup region. */ 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 terminate_fn; } 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); /* Functions and arrays decay to pointers. */ type = type_decays_to (type); return type; } /* Return the type info for TYPE as used by EH machinery. */ tree eh_type_info (tree type) { if (type == NULL_TREE || type == error_mark_node) return type; return get_tinfo_decl (type); } /* Build the address of a typeinfo decl for use in the runtime matching field of the exception model. */ 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_call_n (builtin_decl_explicit (BUILT_IN_EH_POINTER), 1, integer_zero_node); } /* Find or declare a function NAME, returning RTYPE, taking a single parameter PTYPE, with an empty exception specification. ECF are the library fn flags. If TM_ECF is non-zero, also find or create a transaction variant and record it as a replacement, when flag_tm is in effect. Note that the C++ ABI document does not have a throw-specifier on the routines declared below via this function. The declarations are consistent with the actual implementations in libsupc++. */ static tree declare_library_fn (const char *name, tree rtype, tree ptype, int ecf, int tm_ecf) { tree ident = get_identifier (name); tree res = get_global_binding (ident); if (!res) { tree type = build_function_type_list (rtype, ptype, NULL_TREE); tree except = ecf & ECF_NOTHROW ? empty_except_spec : NULL_TREE; res = push_library_fn (ident, type, except, ecf); if (tm_ecf && flag_tm) { char *tm_name = concat ("_ITM_", name + 2, NULL_TREE); tree tm_ident = get_identifier (tm_name); free (tm_name); tree tm_fn = get_global_binding (tm_ident); if (!tm_fn) tm_fn = push_library_fn (tm_ident, type, except, ecf | tm_ecf); record_tm_replacement (res, tm_fn); } } return res; } /* Build up a call to __cxa_get_exception_ptr so that we can build a copy constructor for the thrown object. */ static tree do_get_exception_ptr (void) { if (!get_exception_ptr_fn) /* Declare void* __cxa_get_exception_ptr (void *) throw(). */ get_exception_ptr_fn = declare_library_fn ("__cxa_get_exception_ptr", ptr_type_node, ptr_type_node, ECF_NOTHROW | ECF_PURE | ECF_LEAF | ECF_TM_PURE, 0); return cp_build_function_call_nary (get_exception_ptr_fn, tf_warning_or_error, build_exc_ptr (), NULL_TREE); } /* Build up a call to __cxa_begin_catch, to tell the runtime that the exception has been handled. */ static tree do_begin_catch (void) { if (!begin_catch_fn) /* Declare void* __cxa_begin_catch (void *) throw(). */ begin_catch_fn = declare_library_fn ("__cxa_begin_catch", ptr_type_node, ptr_type_node, ECF_NOTHROW, ECF_TM_PURE); return cp_build_function_call_nary (begin_catch_fn, tf_warning_or_error, 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 || type == error_mark_node) return 0; if (TYPE_HAS_TRIVIAL_DESTRUCTOR (type)) return 1; if (CLASSTYPE_LAZY_DESTRUCTOR (type)) lazily_declare_fn (sfk_destructor, type); return TREE_NOTHROW (CLASSTYPE_DESTRUCTOR (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) { if (!end_catch_fn) /* Declare void __cxa_end_catch (). This can throw if the destructor for the exception throws. */ end_catch_fn = declare_library_fn ("__cxa_end_catch", void_type_node, NULL_TREE, 0, ECF_TM_PURE); tree cleanup = cp_build_function_call_vec (end_catch_fn, NULL, tf_warning_or_error); 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)); } /* Wrap EXPR in a MUST_NOT_THROW_EXPR expressing that EXPR must not throw any exceptions if COND is true. A condition of NULL_TREE is treated as 'true'. */ tree build_must_not_throw_expr (tree body, tree cond) { tree type = body ? TREE_TYPE (body) : void_type_node; if (!flag_exceptions) return body; if (!cond) /* OK, unconditional. */; else { tree conv = NULL_TREE; if (!type_dependent_expression_p (cond)) conv = perform_implicit_conversion_flags (boolean_type_node, cond, tf_warning_or_error, LOOKUP_NORMAL); if (tree inst = instantiate_non_dependent_or_null (conv)) cond = cxx_constant_value (inst); else require_constant_expression (cond); if (integer_zerop (cond)) return body; else if (integer_onep (cond)) cond = NULL_TREE; } return build2 (MUST_NOT_THROW_EXPR, type, body, cond); } /* 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; DECL_READ_P (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 (!POINTER_TYPE_P (init_type)) init_type = build_reference_type (init_type); /* 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 = cp_build_addr_expr (exp, tf_warning_or_error); exp = ocp_convert (init_type, exp, CONV_IMPLICIT|CONV_FORCE_TEMP, 0, tf_warning_or_error); 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, tf_warning_or_error); /* Force cleanups now to avoid nesting problems with the MUST_NOT_THROW_EXPR. */ init = fold_build_cleanup_point_expr (TREE_TYPE (init), init); init = build_must_not_throw_expr (init, NULL_TREE); } decl = pushdecl (decl); start_decl_1 (decl, true); cp_finish_decl (decl, init, /*init_const_expr_p=*/false, NULL_TREE, LOOKUP_ONLYCONVERTING|DIRECT_BIND); } /* Routine to see if exception handling is turned on. DO_WARN is nonzero if we want to inform the user that exception handling is turned off. This is used to ensure that -fexceptions has been specified if the compiler tries to use any exception-specific functions. */ static inline int doing_eh (void) { if (! flag_exceptions) { static int warned = 0; if (! warned) { error ("exception handling disabled, use -fexceptions to enable"); warned = 1; } return 0; } return 1; } /* Call this to start a catch block. DECL is the catch parameter. */ tree expand_start_catch_block (tree decl) { tree exp; tree type, init; if (! doing_eh ()) return NULL_TREE; if (decl) { if (!is_admissible_throw_operand_or_catch_parameter (decl, false)) decl = error_mark_node; type = prepare_eh_type (TREE_TYPE (decl)); mark_used (eh_type_info (type)); } else type = NULL_TREE; /* Call __cxa_end_catch at the end of processing the exception. */ push_eh_cleanup (type); init = do_begin_catch (); /* If there's no decl at all, then all we need to do is make sure to tell the runtime that we've begun handling the exception. */ if (decl == NULL || decl == error_mark_node || init == error_mark_node) finish_expr_stmt (init); /* If the C++ object needs constructing, we need to do that before calling __cxa_begin_catch, so that std::uncaught_exception gets the right value during the copy constructor. */ else if (flag_use_cxa_get_exception_ptr && TYPE_NEEDS_CONSTRUCTING (TREE_TYPE (decl))) { exp = do_get_exception_ptr (); initialize_handler_parm (decl, exp); finish_expr_stmt (init); } /* Otherwise the type uses a bitwise copy, and we don't have to worry about the value of std::uncaught_exception and therefore can do the copy with the return value of __cxa_end_catch instead. */ else { tree init_type = type; /* Pointers are passed by values, everything else by reference. */ if (!TYPE_PTR_P (type)) init_type = build_pointer_type (type); if (init_type != TREE_TYPE (init)) init = build1 (NOP_EXPR, init_type, init); exp = create_temporary_var (init_type); cp_finish_decl (exp, init, /*init_const_expr=*/false, NULL_TREE, LOOKUP_ONLYCONVERTING); DECL_REGISTER (exp) = 1; 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 ()) 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))) { tree rethrow = build_throw (NULL_TREE); TREE_NO_WARNING (rethrow) = true; finish_expr_stmt (rethrow); } } tree begin_eh_spec_block (void) { tree r; location_t spec_location = DECL_SOURCE_LOCATION (current_function_decl); /* A noexcept specification (or throw() with -fnothrow-opt) is a MUST_NOT_THROW_EXPR. */ if (TYPE_NOEXCEPT_P (TREE_TYPE (current_function_decl))) { r = build_stmt (spec_location, MUST_NOT_THROW_EXPR, NULL_TREE, NULL_TREE); TREE_SIDE_EFFECTS (r) = 1; } else r = build_stmt (spec_location, EH_SPEC_BLOCK, NULL_TREE, NULL_TREE); add_stmt (r); TREE_OPERAND (r, 0) = push_stmt_list (); return r; } void finish_eh_spec_block (tree raw_raises, tree eh_spec_block) { tree raises; TREE_OPERAND (eh_spec_block, 0) = pop_stmt_list (TREE_OPERAND (eh_spec_block, 0)); if (TREE_CODE (eh_spec_block) == MUST_NOT_THROW_EXPR) return; /* 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) { if (!allocate_exception_fn) /* Declare void *__cxa_allocate_exception(size_t) throw(). */ allocate_exception_fn = declare_library_fn ("__cxa_allocate_exception", ptr_type_node, size_type_node, ECF_NOTHROW | ECF_MALLOC, ECF_TM_PURE); return cp_build_function_call_nary (allocate_exception_fn, tf_warning_or_error, 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) { if (!free_exception_fn) /* Declare void __cxa_free_exception (void *) throw(). */ free_exception_fn = declare_library_fn ("__cxa_free_exception", void_type_node, ptr_type_node, ECF_NOTHROW | ECF_LEAF, ECF_TM_PURE); return cp_build_function_call_nary (free_exception_fn, tf_warning_or_error, 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, void * /*data*/) { 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 = build2 (MUST_NOT_THROW_EXPR, void_type_node, cleanup, NULL_TREE); TARGET_EXPR_CLEANUP (exp) = cleanup; } /* Keep iterating. */ return NULL_TREE; } /* Build a throw expression. */ tree build_throw (tree exp) { if (exp == error_mark_node) return exp; if (processing_template_decl) { if (cfun) current_function_returns_abnormally = 1; exp = build_min (THROW_EXPR, void_type_node, exp); SET_EXPR_LOCATION (exp, input_location); return exp; } if (exp == null_node) warning (0, "throwing NULL, which has integral, not pointer type"); if (exp != NULL_TREE) { if (!is_admissible_throw_operand_or_catch_parameter (exp, true)) return error_mark_node; } if (! doing_eh ()) return error_mark_node; if (exp) { tree throw_type; tree temp_type; tree cleanup; tree object, ptr; tree tmp; tree allocate_expr; /* The CLEANUP_TYPE is the internal type of a destructor. */ if (!cleanup_type) { tmp = build_function_type_list (void_type_node, ptr_type_node, NULL_TREE); cleanup_type = build_pointer_type (tmp); } if (!throw_fn) { tree name = get_identifier ("__cxa_throw"); throw_fn = get_global_binding (name); if (!throw_fn) { /* Declare void __cxa_throw (void*, void*, void (*)(void*)). */ /* ??? Second argument is supposed to be "std::type_info*". */ tmp = build_function_type_list (void_type_node, ptr_type_node, ptr_type_node, cleanup_type, NULL_TREE); throw_fn = push_throw_library_fn (name, tmp); if (flag_tm) { tree itm_name = get_identifier ("_ITM_cxa_throw"); tree itm_fn = get_global_binding (itm_name); if (!itm_fn) itm_fn = push_throw_library_fn (itm_name, tmp); apply_tm_attr (itm_fn, get_identifier ("transaction_pure")); record_tm_replacement (throw_fn, itm_fn); } } } /* [except.throw] A throw-expression initializes a temporary object, the type of which is determined by removing any top-level cv-qualifiers from the static type of the operand of throw and adjusting the type from "array of T" or "function return T" to "pointer to T" or "pointer to function returning T" respectively. */ temp_type = is_bitfield_expr_with_lowered_type (exp); if (!temp_type) temp_type = cv_unqualified (type_decays_to (TREE_TYPE (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 (temp_type); allocate_expr = get_target_expr (allocate_expr); ptr = TARGET_EXPR_SLOT (allocate_expr); TARGET_EXPR_CLEANUP (allocate_expr) = do_free_exception (ptr); CLEANUP_EH_ONLY (allocate_expr) = 1; object = build_nop (build_pointer_type (temp_type), ptr); object = cp_build_indirect_ref (object, RO_NULL, tf_warning_or_error); /* And initialize the exception object. */ if (CLASS_TYPE_P (temp_type)) { int flags = LOOKUP_NORMAL | LOOKUP_ONLYCONVERTING; vec<tree, va_gc> *exp_vec; bool converted = false; /* Under C++0x [12.8/16 class.copy], a thrown lvalue is sometimes treated as an rvalue for the purposes of overload resolution to favor move constructors over copy constructors. */ if (/* Must be a local, automatic variable. */ VAR_P (exp) && DECL_CONTEXT (exp) == current_function_decl && ! TREE_STATIC (exp) /* The variable must not have the `volatile' qualifier. */ && !(cp_type_quals (TREE_TYPE (exp)) & TYPE_QUAL_VOLATILE)) { tree moved = move (exp); exp_vec = make_tree_vector_single (moved); moved = (build_special_member_call (object, complete_ctor_identifier, &exp_vec, TREE_TYPE (object), flags|LOOKUP_PREFER_RVALUE, tf_none)); release_tree_vector (exp_vec); if (moved != error_mark_node) { exp = moved; converted = true; } } /* Call the copy constructor. */ if (!converted) { exp_vec = make_tree_vector_single (exp); exp = (build_special_member_call (object, complete_ctor_identifier, &exp_vec, TREE_TYPE (object), flags, tf_warning_or_error)); release_tree_vector (exp_vec); } if (exp == error_mark_node) { error (" in thrown expression"); return error_mark_node; } } else { tmp = decay_conversion (exp, tf_warning_or_error); if (tmp == error_mark_node) return error_mark_node; exp = build2 (INIT_EXPR, temp_type, object, tmp); } /* Mark any cleanups from the initialization as MUST_NOT_THROW, since they are run after the exception object is initialized. */ cp_walk_tree_without_duplicates (&exp, wrap_cleanups_r, 0); /* Prepend the allocation. */ exp = build2 (COMPOUND_EXPR, TREE_TYPE (exp), allocate_expr, exp); /* Force all the cleanups to be evaluated here so that we don't have to do them during unwinding. */ exp = build1 (CLEANUP_POINT_EXPR, void_type_node, exp); throw_type = build_eh_type_type (prepare_eh_type (TREE_TYPE (object))); cleanup = NULL_TREE; if (type_build_dtor_call (TREE_TYPE (object))) { tree dtor_fn = lookup_fnfields (TYPE_BINFO (TREE_TYPE (object)), complete_dtor_identifier, 0); dtor_fn = BASELINK_FUNCTIONS (dtor_fn); mark_used (dtor_fn); if (TYPE_HAS_NONTRIVIAL_DESTRUCTOR (TREE_TYPE (object))) { cxx_mark_addressable (dtor_fn); /* Pretend it's a normal function. */ cleanup = build1 (ADDR_EXPR, cleanup_type, dtor_fn); } } if (cleanup == NULL_TREE) cleanup = build_int_cst (cleanup_type, 0); /* ??? Indicate that this function call throws throw_type. */ tmp = cp_build_function_call_nary (throw_fn, tf_warning_or_error, ptr, throw_type, cleanup, NULL_TREE); /* Tack on the initialization stuff. */ exp = build2 (COMPOUND_EXPR, TREE_TYPE (tmp), exp, tmp); } else { /* Rethrow current exception. */ if (!rethrow_fn) { tree name = get_identifier ("__cxa_rethrow"); rethrow_fn = get_global_binding (name); if (!rethrow_fn) /* Declare void __cxa_rethrow (void). */ rethrow_fn = push_throw_library_fn (name, build_function_type_list (void_type_node, NULL_TREE)); if (flag_tm) apply_tm_attr (rethrow_fn, get_identifier ("transaction_pure")); } /* ??? Indicate that this function call allows exceptions of the type of the enclosing catch block (if known). */ exp = cp_build_function_call_vec (rethrow_fn, NULL, tf_warning_or_error); } exp = build1 (THROW_EXPR, void_type_node, exp); SET_EXPR_LOCATION (exp, input_location); 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 = TYPE_PTR_P (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; } /* If IS_THROW is true return truth-value if T is an expression 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. If IS_THROW is false, likewise for a catch parameter, same requirements for its type plus rvalue reference type is also not admissible. */ static bool is_admissible_throw_operand_or_catch_parameter (tree t, bool is_throw) { tree expr = is_throw ? t : NULL_TREE; tree type = TREE_TYPE (t); /* C++11 [except.handle] The exception-declaration shall not denote an incomplete type, an abstract class type, or an rvalue reference type. */ /* 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 (abstract_virtuals_error (is_throw ? ACU_THROW : ACU_CATCH, type)) return false; else if (!is_throw && TREE_CODE (type) == REFERENCE_TYPE && TYPE_REF_IS_RVALUE (type)) { error ("cannot declare catch parameter to be of rvalue " "reference type %qT", type); return false; } else if (variably_modified_type_p (type, NULL_TREE)) { if (is_throw) error ("cannot throw expression of type %qT because it involves " "types of variable size", type); else error ("cannot catch type %qT because it involves types of " "variable size", 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 (const_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; /* Being a C library function, DECL_ASSEMBLER_NAME == DECL_NAME unless the system headers are playing rename tricks, and if they are, we don't want to be confused by them. */ id = DECL_NAME (fn); const struct libc_name_struct *s = libc_name::libc_name_p (IDENTIFIER_POINTER (id), IDENTIFIER_LENGTH (id)); if (s == NULL) return 0; switch (s->c_ver) { case 89: return 1; case 99: return !flag_iso || flag_isoc99; case 11: return !flag_iso || flag_isoc11; default: gcc_unreachable (); } } /* 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 (TYPE_PTR_P (to) && TYPE_PTR_P (from)) { to = TREE_TYPE (to); from = TREE_TYPE (from); if (! at_least_as_qualified_p (to, from)) return 0; if (VOID_TYPE_P (to)) 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 the handlers in I 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_stmt_iterator i) { tree type = TREE_TYPE (master); for (; !tsi_end_p (i); tsi_next (&i)) { tree handler = tsi_stmt (i); if (TREE_TYPE (handler) && can_convert_eh (type, TREE_TYPE (handler))) { warning_at (EXPR_LOCATION (handler), 0, "exception of type %qT will be caught", TREE_TYPE (handler)); warning_at (EXPR_LOCATION (master), 0, " by earlier handler for %qT", type); break; } } } /* Given a STATEMENT_LIST of HANDLERs, make sure that they're OK. */ void check_handlers (tree handlers) { tree_stmt_iterator i; /* If we don't have a STATEMENT_LIST, then we've just got one handler, and thus nothing to warn about. */ if (TREE_CODE (handlers) != STATEMENT_LIST) return; i = tsi_start (handlers); if (!tsi_end_p (i)) while (1) { tree handler = tsi_stmt (i); tsi_next (&i); /* No more handlers; nothing to shadow. */ if (tsi_end_p (i)) break; if (TREE_TYPE (handler) == NULL_TREE) permerror (EXPR_LOCATION (handler), "%<...%>" " handler must be the last handler for its try block"); else check_handlers_1 (handler, i); } } /* walk_tree helper for finish_noexcept_expr. Returns non-null if the expression *TP causes the noexcept operator to evaluate to false. 5.3.7 [expr.noexcept]: The result of the noexcept operator is false if in a potentially-evaluated context the expression would contain * a potentially evaluated call to a function, member function, function pointer, or member function pointer that does not have a non-throwing exception-specification (15.4), * a potentially evaluated throw-expression (15.1), * a potentially evaluated dynamic_cast expression dynamic_cast<T>(v), where T is a reference type, that requires a run-time check (5.2.7), or * a potentially evaluated typeid expression (5.2.8) applied to a glvalue expression whose type is a polymorphic class type (10.3). */ static tree check_noexcept_r (tree *tp, int * /*walk_subtrees*/, void * /*data*/) { tree t = *tp; enum tree_code code = TREE_CODE (t); if ((code == CALL_EXPR && CALL_EXPR_FN (t)) || code == AGGR_INIT_EXPR) { /* We can only use the exception specification of the called function for determining the value of a noexcept expression; we can't use TREE_NOTHROW, as it might have a different value in another translation unit, creating ODR problems. We could use TREE_NOTHROW (t) for !TREE_PUBLIC fns, though... */ tree fn = cp_get_callee (t); tree type = TREE_TYPE (fn); gcc_assert (POINTER_TYPE_P (type)); type = TREE_TYPE (type); STRIP_NOPS (fn); if (TREE_CODE (fn) == ADDR_EXPR) fn = TREE_OPERAND (fn, 0); if (TREE_CODE (fn) == FUNCTION_DECL) { /* We do use TREE_NOTHROW for ABI internals like __dynamic_cast, and for C library functions known not to throw. */ if (DECL_EXTERN_C_P (fn) && (DECL_ARTIFICIAL (fn) || nothrow_libfn_p (fn))) return TREE_NOTHROW (fn) ? NULL_TREE : fn; /* A call to a constexpr function is noexcept if the call is a constant expression. */ if (DECL_DECLARED_CONSTEXPR_P (fn) && is_sub_constant_expr (t)) return NULL_TREE; } if (!TYPE_NOTHROW_P (type)) return fn; } return NULL_TREE; } /* If a function that causes a noexcept-expression to be false isn't defined yet, remember it and check it for TREE_NOTHROW again at EOF. */ struct GTY(()) pending_noexcept { tree fn; location_t loc; }; static GTY(()) vec<pending_noexcept, va_gc> *pending_noexcept_checks; /* FN is a FUNCTION_DECL that caused a noexcept-expr to be false. Warn if it can't throw. */ static void maybe_noexcept_warning (tree fn) { if (TREE_NOTHROW (fn)) { warning (OPT_Wnoexcept, "noexcept-expression evaluates to %<false%> " "because of a call to %qD", fn); warning_at (DECL_SOURCE_LOCATION (fn), OPT_Wnoexcept, "but %qD does not throw; perhaps " "it should be declared %<noexcept%>", fn); } } /* Check any functions that weren't defined earlier when they caused a noexcept expression to evaluate to false. */ void perform_deferred_noexcept_checks (void) { int i; pending_noexcept *p; location_t saved_loc = input_location; FOR_EACH_VEC_SAFE_ELT (pending_noexcept_checks, i, p) { input_location = p->loc; maybe_noexcept_warning (p->fn); } input_location = saved_loc; } /* Evaluate noexcept ( EXPR ). */ tree finish_noexcept_expr (tree expr, tsubst_flags_t complain) { if (expr == error_mark_node) return error_mark_node; if (processing_template_decl) return build_min (NOEXCEPT_EXPR, boolean_type_node, expr); return (expr_noexcept_p (expr, complain) ? boolean_true_node : boolean_false_node); } /* Returns whether EXPR is noexcept, possibly warning if allowed by COMPLAIN. */ bool expr_noexcept_p (tree expr, tsubst_flags_t complain) { tree fn; if (expr == error_mark_node) return false; fn = cp_walk_tree_without_duplicates (&expr, check_noexcept_r, 0); if (fn) { if ((complain & tf_warning) && warn_noexcept && TREE_CODE (fn) == FUNCTION_DECL) { if (!DECL_INITIAL (fn)) { /* Not defined yet; check again at EOF. */ pending_noexcept p = {fn, input_location}; vec_safe_push (pending_noexcept_checks, p); } else maybe_noexcept_warning (fn); } return false; } else return true; } /* Return true iff SPEC is throw() or noexcept(true). */ bool nothrow_spec_p (const_tree spec) { gcc_assert (!DEFERRED_NOEXCEPT_SPEC_P (spec)); if (spec == empty_except_spec || spec == noexcept_true_spec) return true; gcc_assert (!spec || TREE_VALUE (spec) || spec == noexcept_false_spec || TREE_PURPOSE (spec) == error_mark_node || processing_template_decl); return false; } /* For FUNCTION_TYPE or METHOD_TYPE, true if NODE is noexcept. This is the case for things declared noexcept(true) and, with -fnothrow-opt, for throw() functions. */ bool type_noexcept_p (const_tree type) { tree spec = TYPE_RAISES_EXCEPTIONS (type); gcc_assert (!DEFERRED_NOEXCEPT_SPEC_P (spec)); if (flag_nothrow_opt) return nothrow_spec_p (spec); else return spec == noexcept_true_spec; } /* For FUNCTION_TYPE or METHOD_TYPE, true if NODE can throw any type, i.e. no exception-specification or noexcept(false). */ bool type_throw_all_p (const_tree type) { tree spec = TYPE_RAISES_EXCEPTIONS (type); gcc_assert (!DEFERRED_NOEXCEPT_SPEC_P (spec)); return spec == NULL_TREE || spec == noexcept_false_spec; } /* Create a representation of the noexcept-specification with constant-expression of EXPR. COMPLAIN is as for tsubst. */ tree build_noexcept_spec (tree expr, int complain) { /* This isn't part of the signature, so don't bother trying to evaluate it until instantiation. */ if (!processing_template_decl && TREE_CODE (expr) != DEFERRED_NOEXCEPT) { expr = perform_implicit_conversion_flags (boolean_type_node, expr, complain, LOOKUP_NORMAL); expr = cxx_constant_value (expr); } if (TREE_CODE (expr) == INTEGER_CST) { if (operand_equal_p (expr, boolean_true_node, 0)) return noexcept_true_spec; else { gcc_checking_assert (operand_equal_p (expr, boolean_false_node, 0)); return noexcept_false_spec; } } else if (expr == error_mark_node) return error_mark_node; else { gcc_assert (processing_template_decl || TREE_CODE (expr) == DEFERRED_NOEXCEPT); return build_tree_list (expr, NULL_TREE); } } /* Returns a TRY_CATCH_EXPR that will put TRY_LIST and CATCH_LIST in the TRY and CATCH locations. CATCH_LIST must be a STATEMENT_LIST */ tree create_try_catch_expr (tree try_expr, tree catch_list) { location_t loc = EXPR_LOCATION (try_expr); append_to_statement_list (do_begin_catch (), &catch_list); append_to_statement_list (build_throw (NULL_TREE), &catch_list); tree catch_tf_expr = build_stmt (loc, TRY_FINALLY_EXPR, catch_list, do_end_catch (NULL_TREE)); catch_list = build2 (CATCH_EXPR, void_type_node, NULL_TREE, catch_tf_expr); tree try_catch_expr = build_stmt (loc, TRY_CATCH_EXPR, try_expr, catch_list); return try_catch_expr; } #include "gt-cp-except.h"