'Allocate a stack slot and initialize it to NULL.
The default is to allocate a pyobject pointer.
Use ``ltype`` to override.'

def alloca(self, name, ltype=None):

    if (ltype is None):
        ltype = self.context.get_value_type(types.pyobject)
    with self.builder.goto_block(self.entry_block):
        ptr = self.builder.alloca(ltype, name=name)
        self.builder.store(cgutils.get_null_value(ltype), ptr)
    return ptr
