infcall, c++: allow more info to be computed for pass-by-reference values
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 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: 2019-12-20 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com> * language.h (struct language_pass_by_ref_info): New struct. (struct language_defn)<la_pass_by_reference>: 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 (cp_pass_by_reference): Update declaration. (struct cp_abi_ops)<pass_by_reference>: 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. Change-Id: Ib1c1f87f2490a5737c469f7b7185ddc7f6a164cb
This commit is contained in:
Tankut Baris Aktemur
parent
e35000a7f8
commit
9d084466d7
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@ -1,3 +1,22 @@
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2019-12-20 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
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* language.h (struct language_pass_by_ref_info): New struct.
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(struct language_defn)<la_pass_by_reference>: Change the signature
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to return a language_pass_by_ref_info instead of an int.
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(language_pass_by_reference): Ditto.
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(default_pass_by_reference): Ditto.
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Adjust the users listed below.
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* arch-utils.c (default_return_in_first_hidden_param_p):
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Update.
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* cp-abi.c (cp_pass_by_reference): Update.
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* cp-abi.h (cp_pass_by_reference): Update declaration.
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(struct cp_abi_ops)<pass_by_reference>: Update.
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* gnu-v3-abi.c (gnuv3_pass_by_reference): Update.
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* infcall.c (call_function_by_hand_dummy): Update.
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* language.c (language_pass_by_reference): Update.
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(default_pass_by_reference): Update.
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* tic6x-tdep.c (tic6x_return_value): Update.
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2019-12-20 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
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* dwarf2read.c (dwarf2_add_member_fn): Read the DW_AT_defaulted
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@ -858,7 +858,7 @@ default_return_in_first_hidden_param_p (struct gdbarch *gdbarch,
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/* Usually, the return value's address is stored the in the "first hidden"
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parameter if the return value should be passed by reference, as
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specified in ABI. */
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return language_pass_by_reference (type);
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return !(language_pass_by_reference (type).trivially_copyable);
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}
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int default_insn_is_call (struct gdbarch *gdbarch, CORE_ADDR addr)
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@ -220,11 +220,13 @@ cplus_typename_from_type_info (struct value *value)
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return (*current_cp_abi.get_typename_from_type_info) (value);
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}
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int
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/* See cp-abi.h. */
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struct language_pass_by_ref_info
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cp_pass_by_reference (struct type *type)
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{
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if ((current_cp_abi.pass_by_reference) == NULL)
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return 0;
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return default_pass_by_reference (type);
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return (*current_cp_abi.pass_by_reference) (type);
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}
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10
gdb/cp-abi.h
10
gdb/cp-abi.h
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@ -207,9 +207,11 @@ extern std::string cplus_typename_from_type_info (struct value *value);
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CORE_ADDR cplus_skip_trampoline (struct frame_info *frame,
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CORE_ADDR stop_pc);
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/* Return non-zero if an argument of type TYPE should be passed by
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reference instead of value. */
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extern int cp_pass_by_reference (struct type *type);
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/* Return a struct that provides pass-by-reference information
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about the given TYPE. */
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extern struct language_pass_by_ref_info cp_pass_by_reference
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(struct type *type);
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struct cp_abi_ops
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{
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@ -246,7 +248,7 @@ struct cp_abi_ops
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struct type *(*get_type_from_type_info) (struct value *value);
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std::string (*get_typename_from_type_info) (struct value *value);
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CORE_ADDR (*skip_trampoline) (struct frame_info *, CORE_ADDR);
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int (*pass_by_reference) (struct type *type);
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struct language_pass_by_ref_info (*pass_by_reference) (struct type *type);
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};
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@ -1230,7 +1230,7 @@ gnuv3_skip_trampoline (struct frame_info *frame, CORE_ADDR stop_pc)
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return real_stop_pc;
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}
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/* Return nonzero if a type should be passed by reference.
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/* Return pass-by-reference information for the given TYPE.
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The rule in the v3 ABI document comes from section 3.1.1. If the
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type has a non-trivial copy constructor or destructor, then the
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@ -1248,22 +1248,33 @@ gnuv3_skip_trampoline (struct frame_info *frame, CORE_ADDR stop_pc)
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We don't do anything with the constructors or destructors,
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but we have to get the argument passing right anyway. */
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static int
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static struct language_pass_by_ref_info
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gnuv3_pass_by_reference (struct type *type)
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{
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int fieldnum, fieldelem;
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type = check_typedef (type);
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/* Start with the default values. */
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struct language_pass_by_ref_info info
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= default_pass_by_reference (type);
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/* FIXME: Currently, this implementation only fills in the
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'trivially-copyable' field to preserve GDB's existing behavior. */
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/* We're only interested in things that can have methods. */
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if (TYPE_CODE (type) != TYPE_CODE_STRUCT
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&& TYPE_CODE (type) != TYPE_CODE_UNION)
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return 0;
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return info;
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/* A dynamic class has a non-trivial copy constructor.
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See c++98 section 12.8 Copying class objects [class.copy]. */
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if (gnuv3_dynamic_class (type))
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return 1;
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{
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info.trivially_copyable = false;
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return info;
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}
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for (fieldnum = 0; fieldnum < TYPE_NFN_FIELDS (type); fieldnum++)
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for (fieldelem = 0; fieldelem < TYPE_FN_FIELDLIST_LENGTH (type, fieldnum);
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@ -1280,7 +1291,10 @@ gnuv3_pass_by_reference (struct type *type)
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/* If we've found a destructor, we must pass this by reference. */
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if (name[0] == '~')
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return 1;
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{
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info.trivially_copyable = false;
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return info;
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}
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/* If the mangled name of this method doesn't indicate that it
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is a constructor, we're not interested.
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@ -1302,11 +1316,13 @@ gnuv3_pass_by_reference (struct type *type)
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if (TYPE_CODE (arg_type) == TYPE_CODE_REF)
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{
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struct type *arg_target_type;
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arg_target_type = check_typedef (TYPE_TARGET_TYPE (arg_type));
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struct type *arg_target_type
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= check_typedef (TYPE_TARGET_TYPE (arg_type));
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if (class_types_same_p (arg_target_type, type))
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return 1;
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{
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info.trivially_copyable = false;
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return info;
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}
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}
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}
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}
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@ -1319,11 +1335,18 @@ gnuv3_pass_by_reference (struct type *type)
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about recursive loops here, since we are only looking at members
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of complete class type. Also ignore any static members. */
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for (fieldnum = 0; fieldnum < TYPE_NFIELDS (type); fieldnum++)
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if (! field_is_static (&TYPE_FIELD (type, fieldnum))
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&& gnuv3_pass_by_reference (TYPE_FIELD_TYPE (type, fieldnum)))
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return 1;
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if (!field_is_static (&TYPE_FIELD (type, fieldnum)))
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{
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struct language_pass_by_ref_info field_info
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= gnuv3_pass_by_reference (TYPE_FIELD_TYPE (type, fieldnum));
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if (!field_info.trivially_copyable)
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{
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info.trivially_copyable = false;
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return info;
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}
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}
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return 0;
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return info;
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}
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static void
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@ -1020,7 +1020,8 @@ call_function_by_hand_dummy (struct value *function,
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args[i] = value_arg_coerce (gdbarch, args[i],
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param_type, prototyped);
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if (param_type != NULL && language_pass_by_reference (param_type))
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if (param_type != NULL
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&& !(language_pass_by_reference (param_type).trivially_copyable))
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args[i] = value_addr (args[i]);
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}
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@ -652,21 +652,23 @@ language_class_name_from_physname (const struct language_defn *lang,
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return NULL;
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}
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/* Return non-zero if TYPE should be passed (and returned) by
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reference at the language level. */
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int
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/* Return information about whether TYPE should be passed
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(and returned) by reference at the language level. */
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struct language_pass_by_ref_info
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language_pass_by_reference (struct type *type)
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{
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return current_language->la_pass_by_reference (type);
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}
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/* Return zero; by default, types are passed by value at the language
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level. The target ABI may pass or return some structs by reference
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independent of this. */
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int
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/* Return a default struct that provides pass-by-reference information
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about the given TYPE. Languages should update the default values
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as appropriate. */
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struct language_pass_by_ref_info
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default_pass_by_reference (struct type *type)
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{
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return 0;
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return {};
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}
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/* Return the default string containing the list of characters
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@ -128,6 +128,47 @@ struct language_arch_info
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struct type *bool_type_default;
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};
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/* In a language (particularly C++) a function argument of an aggregate
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type (i.e. class/struct/union) may be implicitly passed by reference
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even though it is declared a call-by-value argument in the source.
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The struct below puts together necessary information for GDB to be
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able to detect and carry out pass-by-reference semantics for a
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particular type. This type is referred as T in the inlined comments
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below.
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The default values of the fields are chosen to give correct semantics
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for primitive types and for simple aggregate types, such as
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class T {
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int x;
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}; */
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struct language_pass_by_ref_info
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{
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/* True if an argument of type T can be passed to a function by value
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(i.e. not through an implicit reference). False, otherwise. */
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bool trivially_copyable = true;
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/* True if a copy of a value of type T can be initialized by
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memcpy'ing the value bit-by-bit. False, otherwise.
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E.g. If T has a user-defined copy ctor, this should be false. */
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bool trivially_copy_constructible = true;
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/* True if a value of type T can be destructed simply by reclaiming
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the memory area occupied by the value. False, otherwise.
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E.g. If T has a user-defined destructor, this should be false. */
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bool trivially_destructible = true;
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/* True if it is allowed to create a copy of a value of type T.
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False, otherwise.
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E.g. If T has a deleted copy ctor, this should be false. */
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bool copy_constructible = true;
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/* True if a value of type T can be destructed. False, otherwise.
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E.g. If T has a deleted destructor, this should be false. */
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bool destructible = true;
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};
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/* Structure tying together assorted information about a language. */
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struct language_defn
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@ -356,9 +397,10 @@ struct language_defn
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struct ui_file *stream,
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const struct value_print_options *options);
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/* Return non-zero if TYPE should be passed (and returned) by
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reference at the language level. */
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int (*la_pass_by_reference) (struct type *type);
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/* Return information about whether TYPE should be passed
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(and returned) by reference at the language level. */
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struct language_pass_by_ref_info (*la_pass_by_reference)
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(struct type *type);
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/* Return an expression that can be used for a location
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watchpoint. TYPE is a pointer type that points to the memory
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@ -613,14 +655,14 @@ extern void default_print_array_index (struct value *index_value,
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struct ui_file *stream,
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const struct value_print_options *options);
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/* Return non-zero if TYPE should be passed (and returned) by
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reference at the language level. */
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int language_pass_by_reference (struct type *type);
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/* Return information about whether TYPE should be passed
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(and returned) by reference at the language level. */
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struct language_pass_by_ref_info language_pass_by_reference (struct type *type);
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/* Return zero; by default, types are passed by value at the language
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level. The target ABI may pass or return some structs by reference
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independent of this. */
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int default_pass_by_reference (struct type *type);
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/* Return a default struct that provides pass-by-reference information
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about the given TYPE. Languages should update the default values
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as appropriate. */
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struct language_pass_by_ref_info default_pass_by_reference (struct type *type);
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/* The default implementation of la_print_typedef. */
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void default_print_typedef (struct type *type, struct symbol *new_symbol,
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@ -784,7 +784,7 @@ tic6x_return_value (struct gdbarch *gdbarch, struct value *function,
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if (type != NULL)
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{
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type = check_typedef (type);
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if (language_pass_by_reference (type))
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if (!(language_pass_by_reference (type).trivially_copyable))
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return RETURN_VALUE_STRUCT_CONVENTION;
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}
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}
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