"Implicit conversion changes signedness" warning from unicodeobject.h

[skirpichev]

The GraalVM declares PyUnicode_KIND as

enum PyUnicode_Kind {
/* Return values of the PyUnicode_KIND() function: */
    PyUnicode_1BYTE_KIND = 1,
    PyUnicode_2BYTE_KIND = 2,
    PyUnicode_4BYTE_KIND = 4
};

while Python C-API:

PyAPI_FUNC(int) PyUnicode_KIND(PyObject *op);

[msimacek]

PyAPI_FUNC(int) PyUnicode_KIND(PyObject *op);

This is the limited API definition. The normal one in CPython is:
#define PyUnicode_KIND(op) _Py_RVALUE(_PyASCIIObject_CAST(op)->state.kind)
The kind field is declared as an unsigned in a bitfield: unsigned int kind:3;

Our definition is: #define PyUnicode_KIND(op) ((enum PyUnicode_Kind)GraalPyUnicode_KIND(_PyObject_CAST(op)))

If we make it an int, it could cause warnings when you use PyUnicode_Kind or unsigned int as the variable type. I guess we could make it unsigned char which can be losslessly extended to both int and unsigned int. I'll need to experiment with it.