static PyObject*
getenvironment(PyObject* environment)
{
    Py_ssize_t i, envsize, totalsize;
    ...
    envsize = PyMapping_Length(environment);

    totalsize = 1; /* trailing null character */
    for (i = 0; i < envsize; i++) {
        PyObject* key = PyList_GET_ITEM(keys, i);
        PyObject* value = PyList_GET_ITEM(values, i);

        if (! PyUnicode_Check(key) || ! PyUnicode_Check(value)) {
            PyErr_SetString(PyExc_TypeError,
                "environment can only contain strings");
            goto error;
        }
        totalsize += PyUnicode_GET_LENGTH(key) + 1;    /* +1 for '=' */
1       totalsize += PyUnicode_GET_LENGTH(value) + 1;  /* +1 for '\0' */
    }

4   for (i = 0; i < envsize; i++) {
        PyObject* key = PyList_GET_ITEM(keys, i);
        PyObject* value = PyList_GET_ITEM(values, i);
X       if (!PyUnicode_AsUCS4(key, p, end - p, 0))
            goto error;
        p += PyUnicode_GET_LENGTH(key);
X       *p++ = '=';
X       if (!PyUnicode_AsUCS4(value, p, end - p, 0))
            goto error;
        p += PyUnicode_GET_LENGTH(value);
X       *p++ = '\0';
    }