gdb: make thread_info::m_thread_fsm a std::unique_ptr

While working on function calls, I realized that the thread_fsm member
of struct thread_info is a raw pointer to a resource it owns.  This
commit changes the type of the thread_fsm member to a std::unique_ptr in
order to signify this ownership relationship and slightly ease resource
management (no need to manually call delete).

To ensure consistent use, the field is made a private member
(m_thread_fsm).  The setter method (set_thread_fsm) can then check
that it is incorrect to associate a FSM to a thread_info object if
another one is already in place.  This is ensured by an assertion.

The function run_inferior_call takes an argument as a pointer to a
call_thread_fsm and installs it in it in a thread_info instance.  Also
change this function's signature to accept a unique_ptr in order to
signify that the ownership of the call_thread_fsm is transferred during
the call.

No user visible change expected after this commit.

Tested on x86_64-linux with no regression observed.

Change-Id: Ia1224f72a4afa247801ce6650ce82f90224a9ae8

1 files changed, 3 insertions, 4 deletions

diff --git a/gdb/thread.c b/gdb/thread.c
index 611be3f..12f3abd 100644
--- a/gdb/thread.c
+++ b/gdb/thread.c
@@ -160,11 +160,10 @@ thread_has_single_step_breakpoint_here (struct thread_info *tp,
 void
 thread_cancel_execution_command (struct thread_info *thr)
 {
-  if (thr->thread_fsm != NULL)
+  if (thr->thread_fsm () != nullptr)
     {
-      thr->thread_fsm->clean_up (thr);
-      delete thr->thread_fsm;
-      thr->thread_fsm = NULL;
+      std::unique_ptr<thread_fsm> fsm = thr->release_thread_fsm ();
+      fsm->clean_up (thr);
     }
 }