capi: prevent from directly wrapping Go functions

Fixes #102.

Author: sbinet

capi.go

@@ -16,11 +16,13 @@ func Py_BuildValue(format string, args ...interface{}) *PyObject {
 // ml_doc	char *	points to the contents of the docstring
 type PyMethodDef struct {
 	Name  string // name of the method
-	Meth  func(self, args *PyObject) *PyObject
+	Meth  PyCFunction
 	Flags MethodDefFlags
 	Doc   string
 }
 
+type PyCFunction C.PyCFunction
+
 type MethodDefFlags int
 
 const (

heap.go

@@ -24,7 +24,7 @@ func cpyMethodDefs(name string, methods []PyMethodDef) *C.PyMethodDef {
 	for i, meth := range methods {
 		cmeth := C.PyMethodDef{
 			ml_name:  C.CString(meth.Name),
-			ml_meth:  (C.PyCFunction)(unsafe.Pointer(&meth.Meth)),
+			ml_meth:  C.PyCFunction(meth.Meth),
 			ml_flags: C.int(meth.Flags),
 			ml_doc:   C.CString(meth.Doc),
 		}
@@ -43,6 +43,7 @@ func Py_InitModule(name string, methods []PyMethodDef) (*PyObject, error) {
 
 	obj := togo(C._gopy_InitModule(c_mname, cmeths))
 	if obj == nil {
+		PyErr_Print()
 		return nil, errors.New("python: internal error; module creation failed.")
 	}
 	return obj, nil
@@ -59,6 +60,7 @@ func Py_InitModule3(name string, methods []PyMethodDef, doc string) (*PyObject,
 
 	obj := togo(C._gopy_InitModule3(cname, cmeths, cdoc))
 	if obj == nil {
+		PyErr_Print()
 		return nil, errors.New("python: internal error; module creation failed.")
 	}
 	return obj, nil