From 099a6354dab7e74c990501929f383394fc8efd02 Mon Sep 17 00:00:00 2001 From: Tankut Baris Aktemur Date: Fri, 20 Dec 2019 17:43:06 +0100 Subject: [PATCH] infcall: handle pass-by-reference arguments appropriately If an aggregate argument is implicitly pass-by-reference, allocate a temporary object on the stack, initialize it via the copy constructor (if exists) or trivially by memcpy'ing. Pass the reference of the temporary to the callee function. After the callee returns, invoke the destructor of the temporary. gdb/ChangeLog: 2019-12-20 Tankut Baris Aktemur PR gdb/25054 * infcall.c (call_function_by_hand_dummy): Update the argument- passing section for call-by-value parameters. (struct destructor_info): New struct. (call_destructors): New auxiliary function. Change-Id: I18fa5d0df814dfa0defe9e862a88a6dbf1d99d01 --- gdb/ChangeLog | 8 ++++ gdb/infcall.c | 127 ++++++++++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 132 insertions(+), 3 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 43b86f2c023..c2157e44fdb 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,11 @@ +2019-12-20 Tankut Baris Aktemur + + PR gdb/25054 + * infcall.c (call_function_by_hand_dummy): Update the argument- + passing section for call-by-value parameters. + (struct destructor_info): New struct. + (call_destructors): New auxiliary function. + 2019-12-20 Tankut Baris Aktemur * gnu-v3-abi.c (enum definition_style): New enum type. diff --git a/gdb/infcall.c b/gdb/infcall.c index f3664d50804..b6b617aa44b 100644 --- a/gdb/infcall.c +++ b/gdb/infcall.c @@ -42,6 +42,7 @@ #include "thread-fsm.h" #include #include "gdbsupport/scope-exit.h" +#include /* If we can't find a function's name from its address, we print this instead. */ @@ -704,6 +705,33 @@ reserve_stack_space (const type *values_type, CORE_ADDR &sp) return addr; } +/* The data structure which keeps a destructor function and + its implicit 'this' parameter. */ + +struct destructor_info +{ + destructor_info (struct value *function, struct value *self) + : function (function), self (self) { } + + struct value *function; + struct value *self; +}; + + +/* Auxiliary function that takes a list of destructor functions + with their 'this' parameters, and invokes the functions. */ + +static void +call_destructors (const std::list &dtors_to_invoke, + struct type *default_return_type) +{ + for (auto vals : dtors_to_invoke) + { + call_function_by_hand (vals.function, default_return_type, + gdb::make_array_view (&(vals.self), 1)); + } +} + /* See infcall.h. */ struct value * @@ -983,6 +1011,12 @@ call_function_by_hand_dummy (struct value *function, internal_error (__FILE__, __LINE__, _("bad switch")); } + /* Coerce the arguments and handle pass-by-reference. + We want to remember the destruction required for pass-by-ref values. + For these, store the dtor function and the 'this' argument + in DTORS_TO_INVOKE. */ + std::list dtors_to_invoke; + for (int i = args.size () - 1; i >= 0; i--) { int prototyped; @@ -1017,12 +1051,95 @@ call_function_by_hand_dummy (struct value *function, else param_type = NULL; + value *original_arg = args[i]; args[i] = value_arg_coerce (gdbarch, args[i], param_type, prototyped); - if (param_type != NULL - && !(language_pass_by_reference (param_type).trivially_copyable)) - args[i] = value_addr (args[i]); + if (param_type == NULL) + continue; + + auto info = language_pass_by_reference (param_type); + if (!info.copy_constructible) + error (_("expression cannot be evaluated because the type '%s' " + "is not copy constructible"), TYPE_NAME (param_type)); + + if (!info.destructible) + error (_("expression cannot be evaluated because the type '%s' " + "is not destructible"), TYPE_NAME (param_type)); + + if (info.trivially_copyable) + continue; + + /* Make a copy of the argument on the stack. If the argument is + trivially copy ctor'able, copy bit by bit. Otherwise, call + the copy ctor to initialize the clone. */ + CORE_ADDR addr = reserve_stack_space (param_type, sp); + value *clone + = value_from_contents_and_address (param_type, nullptr, addr); + push_thread_stack_temporary (call_thread.get (), clone); + value *clone_ptr + = value_from_pointer (lookup_pointer_type (param_type), addr); + + if (info.trivially_copy_constructible) + { + int length = TYPE_LENGTH (param_type); + write_memory (addr, value_contents (args[i]), length); + } + else + { + value *copy_ctor; + value *cctor_args[2] = { clone_ptr, original_arg }; + find_overload_match (gdb::make_array_view (cctor_args, 2), + TYPE_NAME (param_type), METHOD, + &clone_ptr, nullptr, ©_ctor, nullptr, + nullptr, 0, EVAL_NORMAL); + + if (copy_ctor == nullptr) + error (_("expression cannot be evaluated because a copy " + "constructor for the type '%s' could not be found " + "(maybe inlined?)"), TYPE_NAME (param_type)); + + call_function_by_hand (copy_ctor, default_return_type, + gdb::make_array_view (cctor_args, 2)); + } + + /* If the argument has a destructor, remember it so that we + invoke it after the infcall is complete. */ + if (!info.trivially_destructible) + { + /* Looking up the function via overload resolution does not + work because the compiler (in particular, gcc) adds an + artificial int parameter in some cases. So we look up + the function by using the "~" name. This should be OK + because there can be only one dtor definition. */ + const char *dtor_name = nullptr; + for (int fieldnum = 0; + fieldnum < TYPE_NFN_FIELDS (param_type); + fieldnum++) + { + fn_field *fn + = TYPE_FN_FIELDLIST1 (param_type, fieldnum); + const char *field_name + = TYPE_FN_FIELDLIST_NAME (param_type, fieldnum); + + if (field_name[0] == '~') + dtor_name = TYPE_FN_FIELD_PHYSNAME (fn, 0); + } + + if (dtor_name == nullptr) + error (_("expression cannot be evaluated because a destructor " + "for the type '%s' could not be found " + "(maybe inlined?)"), TYPE_NAME (param_type)); + + value *dtor + = find_function_in_inferior (dtor_name, 0); + + /* Insert the dtor to the front of the list to call them + in reverse order later. */ + dtors_to_invoke.emplace_front (dtor, clone_ptr); + } + + args[i] = clone_ptr; } /* Reserve space for the return structure to be written on the @@ -1189,6 +1306,10 @@ call_function_by_hand_dummy (struct value *function, maybe_remove_breakpoints (); gdb_assert (retval != NULL); + + /* Destruct the pass-by-ref argument clones. */ + call_destructors (dtors_to_invoke, default_return_type); + return retval; } -- 2.30.2