gdb/python: new Progspace.symbol_file attribute

Add a new Progspace.symbol_file attribute.  This attribute holds the
gdb.Objfile object that corresponds to Progspace.filename, or None if
there is no main symbol file currently set.

Currently, to get this gdb.Objfile, a user would need to use
Progspace.objfiles, and then search for the objfile with a name that
matches Progspace.filename -- which should work just fine, but having
direct access seems a little nicer.

Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Approved-By: Tom Tromey <tom@tromey.com>

gdb/python/py-progspace.c

@@ -111,6 +111,26 @@ pspy_get_filename (PyObject *self, void *closure)
   Py_RETURN_NONE;
 }
 
+/* Implement the gdb.Progspace.symbol_file attribute.  Retun the
+   gdb.Objfile corresponding to the currently loaded symbol-file, or None
+   if no symbol-file is loaded.  If the Progspace is invalid then raise an
+   exception.  */
+
+static PyObject *
+pspy_get_symbol_file (PyObject *self, void *closure)
+{
+  pspace_object *obj = (pspace_object *) self;
+
+  PSPY_REQUIRE_VALID (obj);
+
+  struct objfile *objfile = obj->pspace->symfile_object_file;
+
+  if (objfile != nullptr)
+    return objfile_to_objfile_object (objfile).release ();
+
+  Py_RETURN_NONE;
+}
+
 static void
 pspy_dealloc (PyObject *self)
 {
@@ -573,6 +593,9 @@ static gdb_PyGetSetDef pspace_getset[] =
     "The __dict__ for this progspace.", &pspace_object_type },
   { "filename", pspy_get_filename, NULL,
     "The filename of the progspace's main symbol file, or None.", nullptr },
+  { "symbol_file", pspy_get_symbol_file, nullptr,
+    "The gdb.Objfile for the progspace's main symbol file, or None.",
+    nullptr},
   { "pretty_printers", pspy_get_printers, pspy_set_printers,
     "Pretty printers.", NULL },
   { "frame_filters", pspy_get_frame_filters, pspy_set_frame_filters,