cstring troubles

foo_bar_foo · 09-29-2004, 03:28 AM

Hi,
I've never had this trouble before with this but in this situation ??
it's twilight zone time --
so this code gets SMTP response
rfp is static FILE *rfp; that's the read end of an AF_INET socket
it's a local connection to avmailgate on port 25 that relays to exim on port 825 or something
(can't imagine how that makes a difference)

Code:

int  mySMTP::get_response()
{
    char buf[BUFSIZ];
    char nCode[3]={0};
    while (fgets(buf, sizeof(buf), rfp)) {
        buf[strlen(buf)-1] = 0;
        printf("%s --> %s\n", host, buf);
        if (!isdigit(buf[0]) || buf[0] > '3') {
          return 1;
        }
        if (buf[4] != '-')
            break;
    }
    strncpy(nCode, buf, 3);
    return (atoi(nCode));
}

ok with this server buf is
220 lisa.sourcery.net AvMailGate-2.0.2-2
the entire line from the printf is
0x42ce2904localhost --> 220 lisa.sourcery.net AvMailGate-2.0.2-2
somehow above code is returning
2201
last digit is not an "L" (i copy and paste here to make sure)
i haven't tested this alot becaus it always works
i have no idea where the 1 is comming from ?????????
need c gurus help cause i'm not good with c char arrays

dougpotter · 09-29-2004, 04:08 AM

Your buffer, nCode is not null terminated. The function strncpy will not add a null terminating character if it copies the maximum number of characters. Also, your buffer doesn't have space for a null terminating character. Declare nCode as "char nCode[4];", then use the following:

Code:

    strncpy(nCode, buf, 3);
    nCode[3] = 0;
    return (atoi(nCode));

nCode is declared as a local variable (on the stack) so it's unpredictable what nCode[3] would be at run-time. It may have worked in the past because there was a null byte, or some other non-numeric character (atoi stops when it finds the first non-numeric character).

chrism01 · 09-29-2004, 09:37 AM

Actually, adding a zero won't work, you need the string null terminator:
nCode[3] = '\0';

foo_bar_foo · 09-30-2004, 09:43 PM

yep that fixed it !
thanks for both of your help