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infcall: handle pass-by-reference arguments appropriately

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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  <tankut.baris.aktemur@intel.com>

	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
This commit is contained in:
Tankut Baris Aktemur
2019-12-20 17:43:06 +01:00
parent 62bf63d74d
commit 099a6354da
2 changed files with 132 additions and 3 deletions
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127
gdb/infcall.c
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@@ -42,6 +42,7 @@
#include "thread-fsm.h"
#include <algorithm>
#include "gdbsupport/scope-exit.h"
#include <list>
/* 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<destructor_info> &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<destructor_info> 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, &copy_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;
}