From patchwork Mon Jun 24 09:29:42 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Aktemur, Tankut Baris" X-Patchwork-Id: 33337 Received: (qmail 15612 invoked by alias); 24 Jun 2019 09:32:22 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Delivered-To: mailing list gdb-patches@sourceware.org Received: (qmail 15604 invoked by uid 89); 24 Jun 2019 09:32:22 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-21.6 required=5.0 tests=AWL, BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3 autolearn=ham version=3.3.1 spammy=H*r:LOCAL X-HELO: mga07.intel.com Received: from mga07.intel.com (HELO mga07.intel.com) (134.134.136.100) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Mon, 24 Jun 2019 09:32:20 +0000 Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 24 Jun 2019 02:30:19 -0700 Received: from irvmail001.ir.intel.com ([163.33.26.43]) by fmsmga004.fm.intel.com with ESMTP; 24 Jun 2019 02:30:18 -0700 Received: from ulvlx001.iul.intel.com (ulvlx001.iul.intel.com [172.28.207.17]) by irvmail001.ir.intel.com (8.14.3/8.13.6/MailSET/Hub) with ESMTP id x5O9UHed020916; Mon, 24 Jun 2019 10:30:17 +0100 Received: from ulvlx001.iul.intel.com (localhost [127.0.0.1]) by ulvlx001.iul.intel.com with ESMTP id x5O9UHoq022260; Mon, 24 Jun 2019 11:30:17 +0200 Received: (from taktemur@localhost) by ulvlx001.iul.intel.com with LOCAL id x5O9UHoo022256; Mon, 24 Jun 2019 11:30:17 +0200 From: Tankut Baris Aktemur To: gdb-patches@sourceware.org Cc: andrew.burgess@embecosm.com Subject: [PATCH v2 2/8] infcall, c++: allow more info to be computed for pass-by-reference values Date: Mon, 24 Jun 2019 11:29:42 +0200 Message-Id: <1561368588-21858-3-git-send-email-tankut.baris.aktemur@intel.com> In-Reply-To: <1561368588-21858-1-git-send-email-tankut.baris.aktemur@intel.com> References: <1561368588-21858-1-git-send-email-tankut.baris.aktemur@intel.com> X-IsSubscribed: yes In C++, call-by-value arguments that cannot be trivially copied are implicitly passed by reference. When making an infcall, GDB needs to find out if an argument is pass-by-reference or not, so that the correct semantics can be followed. This patch enriches the information computed by the language ops for pass-by-reference arguments. Instead of a plain binary result, the computed information now includes whether the argument is - copy constructible - destructible - trivially copyable - trivially copy constructible - trivially destructible and also - the full name of the copy constructor - the full name of the destructor This information is stored in a struct named 'language_pass_by_ref_info'. This patch paves the way for GDB's infcall mechanism to call the copy ctor and the destructor of a pass-by-ref argument appropriately. gdb/ChangeLog: 2019-MM-DD Tankut Baris Aktemur * language.h (struct language_pass_by_ref_info): New struct. (struct language_defn): Change the signature to return a language_pass_by_ref_info instead of an int. (language_pass_by_reference): Ditto. (default_pass_by_reference): Ditto. Adjust the users listed below. * arch-utils.c (default_return_in_first_hidden_param_p): Update. * cp-abi.c (cp_pass_by_reference): Update. * cp-abi.h (struct cp_abi_ops): Update. * gnu-v3-abi.c (gnuv3_pass_by_reference): Update. * infcall.c (call_function_by_hand_dummy): Update. * language.c (language_pass_by_reference): Update. (default_pass_by_reference): Update. * tic6x-tdep.c (tic6x_return_value): Update. 2019-06-24 Tankut Baris Aktemur --- gdb/arch-utils.c | 2 +- gdb/cp-abi.c | 6 +++-- gdb/cp-abi.h | 10 ++++--- gdb/gnu-v3-abi.c | 49 ++++++++++++++++++++++++--------- gdb/infcall.c | 3 ++- gdb/language.c | 19 +++++++------ gdb/language.h | 70 +++++++++++++++++++++++++++++++++++++++++------- gdb/tic6x-tdep.c | 2 +- 8 files changed, 121 insertions(+), 40 deletions(-) diff --git a/gdb/arch-utils.c b/gdb/arch-utils.c index 43f5834b383..5ccabde45e3 100644 --- a/gdb/arch-utils.c +++ b/gdb/arch-utils.c @@ -858,7 +858,7 @@ default_return_in_first_hidden_param_p (struct gdbarch *gdbarch, /* Usually, the return value's address is stored the in the "first hidden" parameter if the return value should be passed by reference, as specified in ABI. */ - return language_pass_by_reference (type); + return !(language_pass_by_reference (type).trivially_copyable); } int default_insn_is_call (struct gdbarch *gdbarch, CORE_ADDR addr) diff --git a/gdb/cp-abi.c b/gdb/cp-abi.c index bbb74d42638..6503b4c160b 100644 --- a/gdb/cp-abi.c +++ b/gdb/cp-abi.c @@ -220,11 +220,13 @@ cplus_typename_from_type_info (struct value *value) return (*current_cp_abi.get_typename_from_type_info) (value); } -int +/* See cp-abi.h. */ + +struct language_pass_by_ref_info cp_pass_by_reference (struct type *type) { if ((current_cp_abi.pass_by_reference) == NULL) - return 0; + return default_pass_by_reference (type); return (*current_cp_abi.pass_by_reference) (type); } diff --git a/gdb/cp-abi.h b/gdb/cp-abi.h index 3cbf19cd511..cc77e0b0632 100644 --- a/gdb/cp-abi.h +++ b/gdb/cp-abi.h @@ -207,9 +207,11 @@ extern std::string cplus_typename_from_type_info (struct value *value); CORE_ADDR cplus_skip_trampoline (struct frame_info *frame, CORE_ADDR stop_pc); -/* Return non-zero if an argument of type TYPE should be passed by - reference instead of value. */ -extern int cp_pass_by_reference (struct type *type); +/* Return a struct that provides pass-by-reference information + about the given TYPE. */ + +extern struct language_pass_by_ref_info cp_pass_by_reference + (struct type *type); struct cp_abi_ops { @@ -246,7 +248,7 @@ struct cp_abi_ops struct type *(*get_type_from_type_info) (struct value *value); std::string (*get_typename_from_type_info) (struct value *value); CORE_ADDR (*skip_trampoline) (struct frame_info *, CORE_ADDR); - int (*pass_by_reference) (struct type *type); + struct language_pass_by_ref_info (*pass_by_reference) (struct type *type); }; diff --git a/gdb/gnu-v3-abi.c b/gdb/gnu-v3-abi.c index 6407c9beb82..69cd56859cb 100644 --- a/gdb/gnu-v3-abi.c +++ b/gdb/gnu-v3-abi.c @@ -1228,7 +1228,7 @@ gnuv3_skip_trampoline (struct frame_info *frame, CORE_ADDR stop_pc) return real_stop_pc; } -/* Return nonzero if a type should be passed by reference. +/* Return pass-by-reference information for the given TYPE. The rule in the v3 ABI document comes from section 3.1.1. If the type has a non-trivial copy constructor or destructor, then the @@ -1246,22 +1246,33 @@ gnuv3_skip_trampoline (struct frame_info *frame, CORE_ADDR stop_pc) We don't do anything with the constructors or destructors, but we have to get the argument passing right anyway. */ -static int + +static struct language_pass_by_ref_info gnuv3_pass_by_reference (struct type *type) { int fieldnum, fieldelem; type = check_typedef (type); + /* Start with the default values. */ + struct language_pass_by_ref_info info + = default_pass_by_reference (type); + + /* FIXME: Currently, this implementation only fills in the + 'trivially-copyable' field to perserve GDB's existing behavior. */ + /* We're only interested in things that can have methods. */ if (TYPE_CODE (type) != TYPE_CODE_STRUCT && TYPE_CODE (type) != TYPE_CODE_UNION) - return 0; + return info; /* A dynamic class has a non-trivial copy constructor. See c++98 section 12.8 Copying class objects [class.copy]. */ if (gnuv3_dynamic_class (type)) - return 1; + { + info.trivially_copyable = false; + return info; + } for (fieldnum = 0; fieldnum < TYPE_NFN_FIELDS (type); fieldnum++) for (fieldelem = 0; fieldelem < TYPE_FN_FIELDLIST_LENGTH (type, fieldnum); @@ -1278,7 +1289,10 @@ gnuv3_pass_by_reference (struct type *type) /* If we've found a destructor, we must pass this by reference. */ if (name[0] == '~') - return 1; + { + info.trivially_copyable = false; + return info; + } /* If the mangled name of this method doesn't indicate that it is a constructor, we're not interested. @@ -1300,11 +1314,13 @@ gnuv3_pass_by_reference (struct type *type) if (TYPE_CODE (arg_type) == TYPE_CODE_REF) { - struct type *arg_target_type; - - arg_target_type = check_typedef (TYPE_TARGET_TYPE (arg_type)); + struct type *arg_target_type + = check_typedef (TYPE_TARGET_TYPE (arg_type)); if (class_types_same_p (arg_target_type, type)) - return 1; + { + info.trivially_copyable = false; + return info; + } } } } @@ -1317,11 +1333,18 @@ gnuv3_pass_by_reference (struct type *type) about recursive loops here, since we are only looking at members of complete class type. Also ignore any static members. */ for (fieldnum = 0; fieldnum < TYPE_NFIELDS (type); fieldnum++) - if (! field_is_static (&TYPE_FIELD (type, fieldnum)) - && gnuv3_pass_by_reference (TYPE_FIELD_TYPE (type, fieldnum))) - return 1; + if (!field_is_static (&TYPE_FIELD (type, fieldnum))) + { + struct language_pass_by_ref_info field_info + = gnuv3_pass_by_reference (TYPE_FIELD_TYPE (type, fieldnum)); + if (!field_info.trivially_copyable) + { + info.trivially_copyable = false; + return info; + } + } - return 0; + return info; } static void diff --git a/gdb/infcall.c b/gdb/infcall.c index 84092d37e64..9b833643dcc 100644 --- a/gdb/infcall.c +++ b/gdb/infcall.c @@ -985,7 +985,8 @@ call_function_by_hand_dummy (struct value *function, args[i] = value_arg_coerce (gdbarch, args[i], param_type, prototyped, &sp); - if (param_type != NULL && language_pass_by_reference (param_type)) + if (param_type != NULL + && !(language_pass_by_reference (param_type).trivially_copyable)) args[i] = value_addr (args[i]); } diff --git a/gdb/language.c b/gdb/language.c index a7c09ccd6db..85066033606 100644 --- a/gdb/language.c +++ b/gdb/language.c @@ -652,21 +652,24 @@ language_class_name_from_physname (const struct language_defn *lang, return NULL; } -/* Return non-zero if TYPE should be passed (and returned) by - reference at the language level. */ -int +/* Return information about whether TYPE should be passed + (and returned) by reference at the language level. */ + +struct language_pass_by_ref_info language_pass_by_reference (struct type *type) { return current_language->la_pass_by_reference (type); } -/* Return zero; by default, types are passed by value at the language - level. The target ABI may pass or return some structs by reference - independent of this. */ -int +/* Return a default struct that provides pass-by-reference information + about the given TYPE. Languages should update the default values + as appropriate. */ + +struct language_pass_by_ref_info default_pass_by_reference (struct type *type) { - return 0; + struct language_pass_by_ref_info info; + return info; } /* Return the default string containing the list of characters diff --git a/gdb/language.h b/gdb/language.h index e7446efa07f..c3afe30a2d0 100644 --- a/gdb/language.h +++ b/gdb/language.h @@ -128,6 +128,55 @@ struct language_arch_info struct type *bool_type_default; }; +/* In a language (particularly C++) a function argument of an aggregate + type (i.e. class/struct/union) may be implicitly passed by reference + even though it is declared a call-by-value argument in the source. + The struct below puts together necessary information for GDB to be + able to detect and carry out pass-by-reference semantics for a + particular type. This type is referred as T in the inlined comments + below. + + The default values of the fields are chosen to give correct semantics + for primitive types and for simple aggregate types, such as + + class T { + int x; + }; */ + +struct language_pass_by_ref_info +{ + /* Name of the copy ctor function of T. Expected to be + fully-qualified. */ + const char *cctor_name = nullptr; + + /* Name of the destructor function of T. Expected to be + fully-qualified. */ + const char *dtor_name = nullptr; + + /* True if an argument of type T can be passed to a function by value + (i.e. not through an implicit reference). False, otherwise. */ + bool trivially_copyable = true; + + /* True if a copy of a value of type T can be initialized by + memcpy'ing the value bit-by-bit. False, otherwise. + E.g. If T has a user-defined copy ctor, this should be false. */ + bool trivially_copy_constructible = true; + + /* True if a value of type T can be destructed simply by reclaiming + the memory area occupied by the value. False, otherwise. + E.g. If T has a user-defined destructor, this should be false. */ + bool trivially_destructible = true; + + /* True if it is allowed to create a copy of a value of type T. + False, otherwise. + E.g. If T has a deleted copy ctor, this should be false. */ + bool copy_constructible = true; + + /* True if a value of type T can be destructed. False, otherwise. + E.g. If T has a deleted destructor, this should be false. */ + bool destructible = true; +}; + /* Structure tying together assorted information about a language. */ struct language_defn @@ -356,9 +405,10 @@ struct language_defn struct ui_file *stream, const struct value_print_options *options); - /* Return non-zero if TYPE should be passed (and returned) by - reference at the language level. */ - int (*la_pass_by_reference) (struct type *type); + /* Return information about whether TYPE should be passed + (and returned) by reference at the language level. */ + struct language_pass_by_ref_info (*la_pass_by_reference) + (struct type *type); /* Obtain a string from the inferior, storing it in a newly allocated buffer in BUFFER, which should be freed by the caller. If the @@ -625,14 +675,14 @@ extern void default_print_array_index (struct value *index_value, struct ui_file *stream, const struct value_print_options *options); -/* Return non-zero if TYPE should be passed (and returned) by - reference at the language level. */ -int language_pass_by_reference (struct type *type); +/* Return information about whether TYPE should be passed + (and returned) by reference at the language level. */ +struct language_pass_by_ref_info language_pass_by_reference (struct type *type); -/* Return zero; by default, types are passed by value at the language - level. The target ABI may pass or return some structs by reference - independent of this. */ -int default_pass_by_reference (struct type *type); +/* Return a default struct that provides pass-by-reference information + about the given TYPE. Languages should update the default values + as appropriate. */ +struct language_pass_by_ref_info default_pass_by_reference (struct type *type); /* The default implementation of la_print_typedef. */ void default_print_typedef (struct type *type, struct symbol *new_symbol, diff --git a/gdb/tic6x-tdep.c b/gdb/tic6x-tdep.c index 2df83c4f619..ca059f91b58 100644 --- a/gdb/tic6x-tdep.c +++ b/gdb/tic6x-tdep.c @@ -784,7 +784,7 @@ tic6x_return_value (struct gdbarch *gdbarch, struct value *function, if (type != NULL) { type = check_typedef (type); - if (language_pass_by_reference (type)) + if (!(language_pass_by_reference (type).trivially_copyable)) return RETURN_VALUE_STRUCT_CONVENTION; } }