Add new overload of gdbarch_return_value

The gdbarch "return_value" can't correctly handle variably-sized
types.  The problem here is that the TYPE_LENGTH of such a type is 0,
until the type is resolved, which requires reading memory.  However,
gdbarch_return_value only accepts a buffer as an out parameter.

Fixing this requires letting the implementation of the gdbarch method
resolve the type and return a value -- that is, both the contents and
the new type.

After an attempt at this, I realized I wouldn't be able to correctly
update all implementations (there are ~80) of this method.  So,
instead, this patch adds a new method that falls back to the current
method, and it updates gdb to only call the new method.  This way it's
possible to incrementally convert the architectures that I am able to
test.

1 files changed, 9 insertions, 9 deletions

diff --git a/gdb/infcmd.c b/gdb/infcmd.c
index 0c1765d..0497ad0 100644
--- a/gdb/infcmd.c
+++ b/gdb/infcmd.c
@@ -1497,15 +1497,14 @@ get_return_value (struct symbol *func_symbol, struct value *function)
      inferior function call code.  In fact, when inferior function
      calls are made async, this will likely be made the norm.  */
 
-  switch (gdbarch_return_value (gdbarch, function, value_type,
-				nullptr, nullptr, nullptr))
+  switch (gdbarch_return_value_as_value (gdbarch, function, value_type,
+					 nullptr, nullptr, nullptr))
     {
     case RETURN_VALUE_REGISTER_CONVENTION:
     case RETURN_VALUE_ABI_RETURNS_ADDRESS:
     case RETURN_VALUE_ABI_PRESERVES_ADDRESS:
-      value = allocate_value (value_type);
-      gdbarch_return_value (gdbarch, function, value_type, stop_regs,
-			    value_contents_raw (value).data (), nullptr);
+      gdbarch_return_value_as_value (gdbarch, function, value_type, stop_regs,
+				     &value, nullptr);
       break;
     case RETURN_VALUE_STRUCT_CONVENTION:
       value = nullptr;
@@ -1889,10 +1888,11 @@ finish_command (const char *arg, int from_tty)
       struct type * val_type
 	= check_typedef (sm->function->type ()->target_type ());
 
-      return_value = gdbarch_return_value (gdbarch,
-					   read_var_value (sm->function, nullptr,
-							   callee_frame),
-					   val_type, nullptr, nullptr, nullptr);
+      return_value
+	= gdbarch_return_value_as_value (gdbarch,
+					 read_var_value (sm->function, nullptr,
+							 callee_frame),
+					 val_type, nullptr, nullptr, nullptr);
 
       if (return_value == RETURN_VALUE_STRUCT_CONVENTION
 	  && val_type->code () != TYPE_CODE_VOID)