I marked bpo-34992 as a duplicate of this issue:

I use Fedora 28 and gcc (GCC) 8.1.1 20180712 (Red Hat 8.1.1-5)

and I get a lot of warnings, with the standard config of Python (./configure)

Objects/call.c: In function '_PyMethodDef_RawFastCallDict':
Objects/call.c:515:24: warning: cast between incompatible function types from 'PyCFunction' {aka 'struct _object * (*)(struct _object *, struct _object *)'} to 'PyObject * (*)(PyObject *, PyObject *, PyObject *)' {aka 'struct _object * (*)(struct _object *, struct _object *, struct _object *)'} [-Wcast-function-type]
             result = (*(PyCFunctionWithKeywords)meth) (self, argstuple, kwargs);
                        ^
Objects/call.c:530:20: warning: cast between incompatible function types from 'PyCFunction' {aka 'struct _object * (*)(struct _object *, struct _object *)'} to 'PyObject * (*)(PyObject *, PyObject * const*, Py_ssize_t)' {aka 'struct _object * (*)(struct _object *, struct _object * const*, long int)'} [-Wcast-function-type]
         result = (*(_PyCFunctionFast)meth) (self, args, nargs);
                    ^
Objects/call.c:538:49: warning: cast between incompatible function types from 'PyCFunction' {aka 'struct _object * (*)(struct _object *, struct _object *)'} to 'PyObject * (*)(PyObject *, PyObject * const*, Py_ssize_t,  PyObject *)' {aka 'struct _object * (*)(struct _object *, struct _object * const*, long int,  struct _object *)'} [-Wcast-function-type]
         _PyCFunctionFastWithKeywords fastmeth = (_PyCFunctionFastWithKeywords)meth;

....

+- 827 warnings