Accessing a negative index

[soramame21]

I read following code and found next line is accessing a negative index. Is it true?
response[i+1-_recv_delim_size]
I assume following conditions.
i=0, recv_delim_size=2, recv_delimiter="\r\n"

bool ATParser::vrecv(const char *response, va_list args)

        int i = 0;
        int offset = 0;

        while (response[i]) {
            if (memcmp(&response[i+1-_recv_delim_size], _recv_delimiter, _recv_delim_size) == 0) {
                i++;

[geky]

That is a good catch! Although now I'm not sure what that line is doing exactly.

I think it should be replaced with

if (strncmp(&response[i], _recv_delimiter, _recv_delim_size) == 0) {
    i += _recv_delim_size;
    break;

This will need some testing to make sure.

[soramame21]

@geky I see. Thanks for reply and the fix.