[PATCH v2 1/2] thread: add can_access_registers_ptid

[Markus Metzger <markus.t.metzger@intel.com>]

Add a function can_access_registers_ptid that behaves like
validate_registers_access but returns a boolean value instead of throwing an
exception.

2017-01-20  Markus Metzger  <markus.t.metzger@intel.com>

	* gdbthread.h (can_access_registers_ptid): New.
	* thread.c (can_access_registers_ptid): New.
---
 gdb/gdbthread.h |  4 ++++
 gdb/thread.c    | 20 ++++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/gdb/gdbthread.h b/gdb/gdbthread.h
index 455cfd8..041b7c2 100644
--- a/gdb/gdbthread.h
+++ b/gdb/gdbthread.h
@@ -625,6 +625,10 @@ extern void thread_cancel_execution_command (struct thread_info *thr);
    executing).  */
 extern void validate_registers_access (void);
 
+/* Check whether it makes sense to access a register of PTID at this point.
+   Returns non-zero if registers may be accessed; zero otherwise.  */
+extern int can_access_registers_ptid (ptid_t ptid);
+
 /* Returns whether to show which thread hit the breakpoint, received a
    signal, etc. and ended up causing a user-visible stop.  This is
    true iff we ever detected multiple threads.  */
diff --git a/gdb/thread.c b/gdb/thread.c
index e45b257..d5dfe80 100644
--- a/gdb/thread.c
+++ b/gdb/thread.c
@@ -1141,6 +1141,26 @@ validate_registers_access (void)
     error (_("Selected thread is running."));
 }
 
+/* See gdbthread.h.  */
+
+int
+can_access_registers_ptid (ptid_t ptid)
+{
+  /* No thread, no registers.  */
+  if (ptid_equal (ptid, null_ptid))
+    return 0;
+
+  /* Don't try to read from a dead thread.  */
+  if (is_exited (ptid))
+    return 0;
+
+  /* ... or from a spinning thread.  FIXME: see validate_registers_access.  */
+  if (is_executing (ptid))
+    return 0;
+
+  return 1;
+}
+
 int
 pc_in_thread_step_range (CORE_ADDR pc, struct thread_info *thread)
 {
-- 
1.8.3.1