Fix segfault on calling unknown method

CHANGELOG.md

@@ -7,7 +7,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ## Unreleased
 
 ### Added
- 
+
  * `#[pyclass]` objects can now be returned from rust functions
  * `PyComplex` by kngwyu in [#226](https://github.com/PyO3/pyo3/pull/226)
 
@@ -28,10 +28,11 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
  * Added an explenation that the GIL can temporarily be released even while holding a GILGuard.
  * Lots of clippy errors
+ * Fix segfault on calling an unknown method on a PyObject
 
 ### Removed
 
- * The pyobject_extract macro   
+ * The pyobject_extract macro
 
 ## [0.4.1] - 2018-08-20
 
@@ -102,7 +103,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ## [0.2.5] - 2018-02-21
 
-### Added 
+### Added
 
 * CPython 3.7 support
 
@@ -121,7 +122,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 * Drop `RefFromPyObject` trait
 * Add Python::register_any() method
 
-### Fixed 
+### Fixed
 
 * Fix impl `FromPyObject` for `Py<T>`
 * Mark method that work with raw pointers as unsafe #95
@@ -160,7 +161,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 * Allow to add gc support without implementing PyGCProtocol #57
 * Refactor `PyErr` implementation. Drop `py` parameter from constructor.
 
-### Added 
+### Added
 
 * Added inheritance support #15
 * Added weakref support #56

src/object.rs

@@ -213,6 +213,9 @@ impl PyObject {
             let args = args.into_tuple(py).into_ptr();
             let kwargs = kwargs.into_ptr();
             let ptr = ffi::PyObject_GetAttr(self.as_ptr(), name);
+            if ptr.is_null() {
+                return Err(PyErr::fetch(py));
+            }
             let result = PyObject::from_owned_ptr_or_err(py, ffi::PyObject_Call(ptr, args, kwargs));
             ffi::Py_DECREF(ptr);
             ffi::Py_XDECREF(args);
@@ -322,3 +325,21 @@ impl Drop for PyObject {
         }
     }
 }
+
+#[cfg(test)]
+mod test {
+    use super::PyObject;
+    use python::Python;
+    use types::PyDict;
+
+    #[test]
+    fn test_call_for_non_existing_method() {
+        let gil = Python::acquire_gil();
+        let py = gil.python();
+        let obj: PyObject = PyDict::new(py).into();
+        assert!(obj.call_method0(py, "asdf").is_err());
+        assert!(obj.call_method(py, "nonexistent_method", (1,), None).is_err());
+        assert!(obj.call_method0(py, "nonexistent_method").is_err());
+        assert!(obj.call_method1(py, "nonexistent_method", (1,)).is_err());
+    }
+}