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  <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

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 43b86f2c023554c0c79112ae19c1e64c6e56daa5..c2157e44fdb9821998873ca3820820bea8bb00e4 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,11 @@
+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.
+
 2019-12-20  Tankut Baris Aktemur  <tankut.baris.aktemur@intel.com>
 
        * gnu-v3-abi.c (enum definition_style): New enum type.

diff --git a/gdb/infcall.c b/gdb/infcall.c
index f3664d508041496def13634fdc962bf075fc8fcb..b6b617aa44b446ff51cd708cd4a48109bc0d1b24 100644 (file)
--- a/gdb/infcall.c
+++ b/gdb/infcall.c
@@ -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;
          }