Add Python InferiorThread.inferior attribute

So a script can easily get at a thread's inferior and its number.

gdb/ChangeLog:
2016-01-13  Pedro Alves  <palves@redhat.com>

	* NEWS: Mention InferiorThread.inferior.
	* python/py-infthread.c (thpy_get_inferior): New.
	(thread_object_getset): Register "inferior".

gdb/testsuite/ChangeLog:
2016-01-13  Pedro Alves  <palves@redhat.com>

	* gdb.python/py-infthread.exp: Test InferiorThread.inferior.

gdb/doc/ChangeLog:
2016-01-13  Pedro Alves  <palves@redhat.com>

	* python.texi (Threads In Python): Document
	InferiorThread.inferior.

gdb/ChangeLog

@@ -1,3 +1,9 @@
+2016-01-13  Pedro Alves  <palves@redhat.com>
+
+	* NEWS: Mention InferiorThread.inferior.
+	* python/py-infthread.c (thpy_get_inferior): New.
+	(thread_object_getset): Register "inferior".
+
 2016-01-13  Pedro Alves  <palves@redhat.com>
 
 	* NEWS: Mention $_inferior.

gdb/NEWS

@@ -175,6 +175,11 @@ show remote catch-syscall-packet
      format.  It outputs data in hexadecimal format with zero-padding on the
      left.
 
+* Python Scripting
+
+  ** gdb.InferiorThread objects have a new attribute "inferior", which
+     is the Inferior object the thread belongs to.
+
 *** Changes in GDB 7.10
 
 * Support for process record-replay and reverse debugging on aarch64*-linux*

gdb/doc/ChangeLog

@@ -1,3 +1,8 @@
+2016-01-13  Pedro Alves  <palves@redhat.com>
+
+	* python.texi (Threads In Python): Document
+	InferiorThread.inferior.
+
 2016-01-13  Pedro Alves  <palves@redhat.com>
 
 	* gdb.texinfo (Inferiors and Programs): Document the $_inferior

gdb/doc/python.texi

@@ -3006,6 +3006,11 @@ Either the LWPID or TID may be 0, which indicates that the operating system
 does not  use that identifier.
 @end defvar
 
+@defvar InferiorThread.inferior
+The inferior this thread belongs to.  This attribute is represented as
+a @code{gdb.Inferior} object.  This attribute is not writable.
+@end defvar
+
 A @code{gdb.InferiorThread} object has the following methods:
 
 @defun InferiorThread.is_valid ()

gdb/python/py-infthread.c

@@ -140,6 +140,18 @@ thpy_get_ptid (PyObject *self, void *closure)
   return gdbpy_create_ptid_object (thread_obj->thread->ptid);
 }
 
+/* Getter for InferiorThread.inferior -> Inferior.  */
+
+static PyObject *
+thpy_get_inferior (PyObject *self, void *ignore)
+{
+  thread_object *thread_obj = (thread_object *) self;
+
+  THPY_REQUIRE_VALID (thread_obj);
+
+  return thread_obj->inf_obj;
+}
+
 /* Implementation of InferiorThread.switch ().
    Makes this the GDB selected thread.  */
 
@@ -285,6 +297,8 @@ static PyGetSetDef thread_object_getset[] =
   { "num", thpy_get_num, NULL, "ID of the thread, as assigned by GDB.", NULL },
   { "ptid", thpy_get_ptid, NULL, "ID of the thread, as assigned by the OS.",
     NULL },
+  { "inferior", thpy_get_inferior, NULL,
+    "The Inferior object this thread belongs to.", NULL },
 
   { NULL }
 };

gdb/testsuite/ChangeLog

@@ -1,3 +1,7 @@
+2016-01-13  Pedro Alves  <palves@redhat.com>
+
+	* gdb.python/py-infthread.exp: Test InferiorThread.inferior.
+
 2016-01-13  Pedro Alves  <palves@redhat.com>
 
 	* gdb.base/default.exp: Expect $_inferior as well.

gdb/testsuite/gdb.python/py-infthread.exp

@@ -44,6 +44,9 @@ gdb_test "python print (t0)" "\\<gdb.InferiorThread object at 0x\[\[:xdigit:\]\]
 gdb_test "python print ('result = %s' % t0.num)" " = 1" "test InferiorThread.num"
 gdb_test "python print ('result = %s' % str (t0.ptid))" " = \\(\[0-9\]+, \[0-9\]+, \[0-9\]+\\)" "test InferiorThread.ptid"
 
+gdb_py_test_silent_cmd "python i0 = t0.inferior" "test InferiorThread.inferior" 1
+gdb_test "python print ('result = %s' % i0.num)" " = 1" "test Inferior.num"
+
 gdb_py_test_silent_cmd "python name = gdb.selected_thread().name" \
     "get supplied name of current thread" 1
 gdb_py_test_silent_cmd "python gdb.selected_thread().name = 'hibob'" \