tok_new(void)
{
    struct tok_state *tok = (struct tok_state *)PyMem_MALLOC(
                                            sizeof(struct tok_state));
    if (tok == NULL)
        return NULL;
    tok->buf = tok->cur = tok->end = tok->inp = tok->start = NULL;
    tok->done = E_OK;
    tok->fp = NULL;
    tok->input = NULL;
    tok->tabsize = TABSIZE;
    tok->indent = 0;
    tok->indstack[0] = 0;

    tok->atbol = 1;
    tok->pendin = 0;
    tok->prompt = tok->nextprompt = NULL;
    tok->lineno = 0;
    tok->level = 0;
    tok->altwarning = 1;
    tok->alterror = 1;
    tok->alttabsize = 1;
    tok->altindstack[0] = 0;
    tok->decoding_state = STATE_INIT;
    tok->decoding_erred = 0;
    tok->read_coding_spec = 0;
    tok->enc = NULL;
    tok->encoding = NULL;
    tok->cont_line = 0;
#ifndef PGEN
    tok->filename = NULL;
    tok->decoding_readline = NULL;
    tok->decoding_buffer = NULL;
#endif

    tok->async_def = 0;
    tok->async_def_indent = 0;
    tok->async_def_nl = 0;

    return tok;
}
The software reads data past the end, or before the beginning, of the intended buffer.