[PATCHv3,1/7] gdb/remote: remove some manual reference count handling
Commit Message
While working on some other target_ops reference count related code, I
spotted that in remote.c we do some manual reference count handling,
i.e. we call target_ops::incref and decref_target (which wraps
target_ops::decref).
I think it would be better to make use of gdb::ref_ptr to automate the
reference count management.
So, this commit updates scoped_mark_target_starting in two ways,
first, I use gdb::ref_ptr to handle the reference counts. Then,
instead of using the scoped_mark_target_starting constructor and
destructor to set and reset the starting_up flag, I now use a
scoped_restore_tmpl object to set and restore the flag.
The above changes mean that the scoped_mark_target_starting destructor
can be completely removed, and the constructor body is now empty.
I've also fixed a typo in the class comment.
The only change in behaviour after this commit is that previously we
didn't care what the value of starting_up was, we just set it to true
in the constructor and false in the destructor.
Now, I assert that the flag is initially false, then set the flag true
when the scoped_mark_target_starting is created.
As the starting_up flag is initialized to false then, for the assert
to fire, we would need to recursively enter
remote_target::start_remote_1, which I don't think is something we
should be doing, so I think the new assert is an improvement.
---
gdb/remote.c | 38 ++++++++++++++++++++++----------------
1 file changed, 22 insertions(+), 16 deletions(-)
@@ -4702,7 +4702,7 @@ remote_target::process_initial_stop_replies (int from_tty)
}
}
-/* Mark a remote_target as marking (by setting the starting_up flag within
+/* Mark a remote_target as starting (by setting the starting_up flag within
its remote_state) for the lifetime of this object. The reference count
on the remote target is temporarily incremented, to prevent the target
being deleted under our feet. */
@@ -4712,26 +4712,32 @@ struct scoped_mark_target_starting
/* Constructor, TARGET is the target to be marked as starting, its
reference count will be incremented. */
scoped_mark_target_starting (remote_target *target)
- : m_remote_target (target)
- {
- m_remote_target->incref ();
- remote_state *rs = m_remote_target->get_remote_state ();
- rs->starting_up = true;
- }
+ : m_remote_target (remote_target_ref::new_reference (target)),
+ m_restore_starting_up (set_starting_up_flag (target))
+ { /* Nothing. */ }
+
+private:
- /* Destructor, mark the target being worked on as no longer starting, and
- decrement the reference count. */
- ~scoped_mark_target_starting ()
+ /* Helper function, set the starting_up flag on TARGET and return an
+ object which, when it goes out of scope, will restore the previous
+ value of the starting_up flag. */
+ static scoped_restore_tmpl<bool>
+ set_starting_up_flag (remote_target *target)
{
- remote_state *rs = m_remote_target->get_remote_state ();
- rs->starting_up = false;
- decref_target (m_remote_target);
+ remote_state *rs = target->get_remote_state ();
+ gdb_assert (!rs->starting_up);
+ return make_scoped_restore (&rs->starting_up, true);
}
-private:
+ /* A gdb::ref_ptr pointer to a remote_target. */
+ using remote_target_ref = gdb::ref_ptr<remote_target, target_ops_ref_policy>;
+
+ /* A reference to the target on which we are operating. */
+ remote_target_ref m_remote_target;
- /* The target on which we are operating. */
- remote_target *m_remote_target;
+ /* An object which restores the previous value of the starting_up flag
+ when it goes out of scope. */
+ scoped_restore_tmpl<bool> m_restore_starting_up;
};
/* Helper for remote_target::start_remote, start the remote connection and