Add Inferior.architecture method

I've written a couple of gdb unwinders in Python, and while doing so,
I wanted to find the architecture of the inferior.  (In an unwinder in
particular, one can't use the frame's architecture, because there is
no frame.)

This patch adds Inferior.architecture to allow this.  Normally I think
I would have chosen an attribute and not a method here, but seeing
that Frame.architecture is a method, I chose a method as well, for
consistency.

gdb/ChangeLog
2018-10-06  Tom Tromey  <tom@tromey.com>

	PR python/19399:
	* python/py-inferior.c: Add "architecture" entry.
	(infpy_architecture): New function.

gdb/doc/ChangeLog
2018-10-06  Tom Tromey  <tom@tromey.com>

	PR python/19399:
	* python.texi (Inferiors In Python): Document
	Inferior.Architecture.

gdb/testsuite/ChangeLog
2018-10-06  Tom Tromey  <tom@tromey.com>

	PR python/19399:
	* gdb.python/py-inferior.exp: Add architecture test.

gdb/ChangeLog

@@ -1,3 +1,9 @@
+2018-10-06  Tom Tromey  <tom@tromey.com>
+
+	PR python/19399:
+	* python/py-inferior.c: Add "architecture" entry.
+	(infpy_architecture): New function.
+
 2018-10-06  Tom Tromey  <tom@tromey.com>
 
 	PR python/21765:

gdb/doc/ChangeLog

@@ -1,3 +1,9 @@
+2018-10-06  Tom Tromey  <tom@tromey.com>
+
+	PR python/19399:
+	* python.texi (Inferiors In Python): Document
+	Inferior.Architecture.
+
 2018-10-06  Tom Tromey  <tom@tromey.com>
 
 	PR python/21765:

gdb/doc/python.texi

@@ -2860,6 +2860,13 @@ when it is called.  If there are no valid threads, the method will
 return an empty tuple.
 @end defun
 
+@defun Inferior.architecture ()
+Return the @code{gdb.Architecture} (@pxref{Architectures In Python})
+for this inferior.  This represents the architecture of the inferior
+as a whole.  Some platforms can have multiple architectures in a
+single address space, so this may not match the architecture of a
+particular frame (@pxref{Frames in Python}).
+
 @findex Inferior.read_memory
 @defun Inferior.read_memory (address, length)
 Read @var{length} addressable memory units from the inferior, starting at

gdb/python/py-inferior.c

@@ -855,6 +855,18 @@ infpy_thread_from_thread_handle (PyObject *self, PyObject *args, PyObject *kw)
   Py_RETURN_NONE;
 }
 
+/* Implementation of gdb.Inferior.architecture.  */
+
+static PyObject *
+infpy_architecture (PyObject *self, PyObject *args)
+{
+  inferior_object *inf = (inferior_object *) self;
+
+  INFPY_REQUIRE_VALID (inf);
+
+  return gdbarch_to_arch_object (inf->inferior->gdbarch);
+}
+
 /* Implement repr() for gdb.Inferior.  */
 
 static PyObject *
@@ -988,6 +1000,9 @@ Return a long with the address of a match, or None." },
     METH_VARARGS | METH_KEYWORDS,
     "thread_from_thread_handle (handle) -> gdb.InferiorThread.\n\
 Return thread object corresponding to thread handle." },
+  { "architecture", (PyCFunction) infpy_architecture, METH_NOARGS,
+    "architecture () -> gdb.Architecture\n\
+Return architecture of this inferior." },
   { NULL }
 };
 

gdb/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2018-10-06  Tom Tromey  <tom@tromey.com>
+
+	PR python/19399:
+	* gdb.python/py-inferior.exp: Add architecture test.
+
 2018-10-06  Tom Tromey  <tom@tromey.com>
 
 	* gdb.base/gnu-ifunc.exp (build): Use standard_output_file.

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

@@ -299,3 +299,11 @@ with_test_prefix "__repr__" {
 	"\\\(<gdb.Inferior num=1, pid=$decimal>, <gdb.Inferior \\\(invalid\\\)>\\\)" \
 	"print all inferiors 2"
 }
+
+# Test architecture.
+with_test_prefix "architecture" {
+    gdb_test "inferior 1" ".*" "switch to first inferior"
+    gdb_test "python print(gdb.selected_frame().architecture() is gdb.selected_inferior().architecture())" \
+	"True" \
+	"inferior architecture matches frame architecture"
+}