show_token_sequence
static const char *show_token_sequence(struct token *token, int quote);
sparse_error(p->pos, "garbage at end: %s", show_token_sequence(p, 0));
warning(token->pos, "%s", show_token_sequence(token->next, 0));
sparse_error(token->pos, "%s", show_token_sequence(token->next, 0));
sparse_error(token->pos, "unrecognized preprocessor line '%s'", show_token_sequence(token, 0));
const char *s = show_token_sequence(arg, 1);