rem: while (string->len>0 && (*ptr==0 || isspace(*ptr))) {
add: while (string->len>0 && (*ptr==0 || isspace((int)*ptr))) {
context: rtrim(str *string){    char *ptr;    ptr = string->s + string->len - 1;    while (string->len>0 && (*ptr==0 || isspace(*ptr))) {        string->len--;        ptr--;    }}