Place displaced step data directly in inferior structure

This patch moves the per-inferior data related to displaced stepping to
be directly in the inferior structure, rather than in a container on the
side.

On notable difference is that previously, we deleted the state on
inferior exit, which guaranteed a clean state if re-using the inferior
for a new run or attach.  We now need to reset the state manually.

At the same time, I changed step_saved_copy to be a gdb::byte_vector, so
it is automatically freed on destruction (which should plug the leak
reported here [1]).

[1] https://sourceware.org/ml/gdb-patches/2018-11/msg00202.html

gdb/ChangeLog:

	* inferior.h (class inferior) <displaced_step_state>: New field.
	* infrun.h (struct displaced_step_state): Move here from
	infrun.c.  Initialize fields, add constructor.
	<inf>: Remove field.
	<reset>: New method.
	* infrun.c (struct displaced_step_inferior_state): Move to
	infrun.h.
	(displaced_step_inferior_states): Remove.
	(get_displaced_stepping_state): Adust.
	(displaced_step_in_progress_any_inferior): Adjust.
	(displaced_step_in_progress_thread): Adjust.
	(displaced_step_in_progress): Adjust.
	(add_displaced_stepping_state): Remove.
	(get_displaced_step_closure_by_addr): Adjust.
	(remove_displaced_stepping_state): Remove.
	(infrun_inferior_exit): Call displaced_step_state.reset.
	(use_displaced_stepping): Don't check for NULL.
	(displaced_step_prepare_throw): Call
	get_displaced_stepping_state.
	(displaced_step_fixup): Don't check for NULL.
	(prepare_for_detach): Don't check for NULL.

1 files changed, 44 insertions, 0 deletions

diff --git a/gdb/infrun.h b/gdb/infrun.h
index 0d1309b..8f61b75 100644
--- a/gdb/infrun.h
+++ b/gdb/infrun.h
@@ -258,4 +258,48 @@ struct buf_displaced_step_closure : displaced_step_closure
   gdb::byte_vector buf;
 };
 
+/* Per-inferior displaced stepping state.  */
+struct displaced_step_inferior_state
+{
+  displaced_step_inferior_state ()
+  {
+    reset ();
+  }
+
+  /* Put this object back in its original state.  */
+  void reset ()
+  {
+    failed_before = 0;
+    step_thread = nullptr;
+    step_gdbarch = nullptr;
+    step_closure = nullptr;
+    step_original = 0;
+    step_copy = 0;
+    step_saved_copy.clear ();
+  }
+
+  /* True if preparing a displaced step ever failed.  If so, we won't
+     try displaced stepping for this inferior again.  */
+  int failed_before;
+
+  /* If this is not nullptr, this is the thread carrying out a
+     displaced single-step in process PID.  This thread's state will
+     require fixing up once it has completed its step.  */
+  thread_info *step_thread;
+
+  /* The architecture the thread had when we stepped it.  */
+  gdbarch *step_gdbarch;
+
+  /* The closure provided gdbarch_displaced_step_copy_insn, to be used
+     for post-step cleanup.  */
+  displaced_step_closure *step_closure;
+
+  /* The address of the original instruction, and the copy we
+     made.  */
+  CORE_ADDR step_original, step_copy;
+
+  /* Saved contents of copy area.  */
+  gdb::byte_vector step_saved_copy;
+};
+
 #endif /* INFRUN_H */