Allow cpdef void-returning functions.

Cython/Compiler/ExprNodes.py

@@ -11182,7 +11182,7 @@ class CoerceToPyTypeNode(CoercionNode):
                     func = func.replace("Object", self.type.name.title(), 1)
                 elif self.type is bytearray_type:
                     func = func.replace("Object", "ByteArray", 1)
-            funccall = "%s(%s)" % (func, self.arg.result())
+            funccall = "%s(%s)" % (func, self.arg.result() or 'NULL')
 
         code.putln('%s = %s; %s' % (
             self.result(),

Cython/Compiler/PyrexTypes.py

@@ -1307,6 +1307,7 @@ class CVoidType(CType):
     #
 
     is_void = 1
+    to_py_function = "__Pyx_void_to_None"
 
     def __repr__(self):
         return "<CVoidType>"

Cython/Utility/ModuleSetupCode.c

@@ -215,6 +215,8 @@ static CYTHON_INLINE float __PYX_NAN() {
 }
 #endif
 
+#define __Pyx_void_to_None(void_result) (void_result, Py_INCREF(Py_None), Py_None)
+
 // Work around clang bug http://stackoverflow.com/questions/21847816/c-invoke-nested-template-class-destructor
 #ifdef __cplusplus
 template<typename T>

tests/run/cpdef.pyx

+cpdef void unraisable():
+    """
+    >>> unraisable()
+    here
+    """
+    print('here')
+    raise RuntimeError()
+
+cpdef void raisable() except *:
+    """
+    >>> raisable()
+    Traceback (most recent call last):
+    ...
+    RuntimeError
+    """
+    print('here')
+    raise RuntimeError()