fix segfault when passing a docstring to def_property* (fixes #222)

include/pybind11/pybind11.h

@@ -860,9 +860,20 @@ public:
     template <typename... Extra>
     class_ &def_property_static(const char *name, const cpp_function &fget, const cpp_function &fset, const Extra& ...extra) {
         auto rec_fget = get_function_record(fget), rec_fset = get_function_record(fset);
+        char *doc_prev = rec_fget->doc; /* 'extra' field may include a property-specific documentation string */
         detail::process_attributes<Extra...>::init(extra..., rec_fget);
-        if (rec_fset)
+        if (rec_fget->doc && rec_fget->doc != doc_prev) {
+            free(doc_prev);
+            rec_fget->doc = strdup(rec_fget->doc);
+        }
+        if (rec_fset) {
+            doc_prev = rec_fset->doc;
             detail::process_attributes<Extra...>::init(extra..., rec_fset);
+            if (rec_fset->doc && rec_fset->doc != doc_prev) {
+                free(doc_prev);
+                rec_fset->doc = strdup(rec_fset->doc);
+            }
+        }
         pybind11::str doc_obj = pybind11::str(rec_fget->doc ? rec_fget->doc : "");
         object property(
             PyObject_CallFunctionObjArgs((PyObject *) &PyProperty_Type, fget.ptr() ? fget.ptr() : Py_None,