consider void* the independent spanning type of any two incompatible pointer types

Cython/Compiler/PyrexTypes.py

@@ -3711,6 +3711,9 @@ def independent_spanning_type(type1, type2):
         return py_object_type
     span_type = _spanning_type(type1, type2)
     if span_type is None:
+        if type1.is_ptr and type2.is_ptr:
+            # incompatible pointers, void* will do as a result
+            return c_void_ptr_type
         return error_type
     return span_type
 

tests/run/pointers.pyx

+cimport cython
 
 cdef char* c_string = b'abcdefg'
 cdef void* void_ptr = c_string
@@ -60,3 +61,29 @@ def bool_binop_truth(int x):
         print True
     if c_string and x or not (void_ptr or int_ptr and float_ptr) or x:
         print True
+
+
+def binop_voidptr(int x, long y, char* z):
+    """
+    >>> binop_voidptr(1, 3, b'abc')
+    'void *'
+    """
+    result = &x and &y and z
+    return cython.typeof(result)
+
+
+def cond_expr_voidptr(int x, long y, char* z):
+    """
+    >>> cond_expr_voidptr(0, -1, b'abc')
+    ('void *', 0)
+    >>> cond_expr_voidptr(-1, 0, b'abc')
+    ('void *', -1)
+    >>> cond_expr_voidptr(-1, 0, b'')
+    ('void *', 0)
+    >>> cond_expr_voidptr(0, -1, b'')
+    ('void *', -1)
+    """
+    result = &x if len(z) else &y
+    assert sizeof(long) >= sizeof(int)
+    assert -1 == <int>(-1L)
+    return cython.typeof(result), (<int*>result)[0]