rem: int *p = (o ? o : &default_quoting_options)->quote_these_too + uc / INT_BITS;
add: unsigned int *p = (o ? o : &default_quoting_options)->quote_these_too + uc / INT_BITS;
context: set_char_quoting (struct quoting_options *o, char c, int i){  unsigned char uc = c;  int *p = (o ? o : &default_quoting_options)->quote_these_too + uc / INT_BITS;  int shift = uc % INT_BITS;  int r = (*p >> shift) & 1;  *p ^= ((i & 1) ^ r) << shift;  return r;}