PR python/18285

gdb/ChangeLog:

	PR python/18285
	* NEWS: Document new gdb.XMethodWorker.get_result_type method.
	* eval.c (evaluate_subexp_standard) <OP_FUNCALL>: Handle
	EVAL_AVOID_SIDE_EFFECTS for xmethods.
	* extension-priv.h (struct extension_language_ops)
	<get_xmethod_result_type>: New member.
	* extension.c (get_xmethod_result_type): New function.
	* extension.h (get_xmethod_result_type): Declare.
	* python/py-xmethods.c (get_result_type_method_name): New static
	global.
	(py_get_result_type_method_name): Ditto.
	(gdbpy_get_xmethod_result_type): New function.
	(gdbpy_initialize_xmethods): Initialize py_get_result_type_method_name.
	* python/python-internal.h (gdbpy_get_xmethod_result_type): Declare.
	* python/python.c (python_extension_ops): Add
	gdbpy_get_xmethod_result_type.
	* python/lib/gdb/xmethod.py (XMethodWorker): Add get_result_type.
	* valarith.c (value_x_binop): Handle EVAL_AVOID_SIDE_EFFECTS for
	xmethods.
	(value_x_unop): Ditto.
	* value.c (result_type_of_xmethod): New function.
	* value.h (result_type_of_xmethod): Declare.

gdb/testsuite/ChangeLog:

	* gdb.python/py-xmethods.exp: Add ptype tests.
	* gdb.python/py-xmethods.py (E_method_char_worker): Add
	get_result_type method.

gdb/doc/ChangeLog:

	* python.texi (Xmethod API) <gdb.XMethodWorker.get_result_type>:
	Document.
	(Writing an Xmethod): Add get_result_type to example.

gdb/doc/python.texi

@@ -2455,6 +2455,13 @@ If the xmethod takes a single argument, then a single
 @code{gdb.Type} object corresponding to it can be returned.
 @end defun
 
+@defun XMethodWorker.get_result_type (self, *args)
+This method returns a @code{gdb.Type} object representing the type
+of the result of invoking this xmethod.
+The @var{args} argument is the same tuple of arguments that would be
+passed to the @code{__call__} method of this worker.
+@end defun
+
 @defun XMethodWorker.__call__ (self, *args)
 This is the method which does the @emph{work} of the xmethod.  The
 @var{args} arguments is the tuple of arguments to the xmethod.  Each
@@ -2571,6 +2578,9 @@ above is as follows:
 class MyClassWorker_geta(gdb.xmethod.XMethodWorker):
     def get_arg_types(self):
         return None
+
+    def get_result_type(self, obj):
+        return gdb.lookup_type('int')
  
     def __call__(self, obj):
         return obj['a_']
@@ -2579,6 +2589,9 @@ class MyClassWorker_geta(gdb.xmethod.XMethodWorker):
 class MyClassWorker_plus(gdb.xmethod.XMethodWorker):
     def get_arg_types(self):
         return gdb.lookup_type('MyClass')
+
+    def get_result_type(self, obj):
+        return gdb.lookup_type('int')
  
     def __call__(self, obj, other):
         return obj['a_'] + other['a_']
@@ -2642,10 +2655,13 @@ of the xmethod workers and xmethod matchers is as follows:
 class MyTemplateWorker_footprint(gdb.xmethod.XMethodWorker):
     def __init__(self, class_type):
         self.class_type = class_type
- 
+
     def get_arg_types(self):
         return None
- 
+
+    def get_result_type(self):
+        return gdb.lookup_type('int')
+
     def __call__(self, obj):
         return (self.class_type.sizeof +
                 obj['dsize_'] *