Oracle Pro*C -- Segmentation fault (core dumped)

Question

I'm teaching myself Pro*C and this is a program with a cursor through records in a database, and it compiles and runs. It gets as a far as prompting "Enter a Guest_ID(type exit to terminate)>>". After that it errors as "Segmentation fault (core dumped)" if an integer is entered. If a string is entered, it seems to go into the conditional immediately inside the outer for loop at

if(nGuest_ID==0)
{
      printf("BYE\n");
      exit(0);
}

and prints "BYE" then exits. Since I'm still getting familiar with how variables are declared and fed in from SQL, I wasn't sure what declarations might be crucial for troubleshooting here so I'm leaving the code largely intact here.

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
exec sql include sqlca;

// OK - Here we GO
void main()
{
    // First, create all the variables that we will need to communicate between 
    // the "C" program and the database
    exec sql begin declare section;
        //VARCHAR sLastName[51], sFirstName[51], sHotelName[51], sCheckInDate[12], sRoom[11];
        VARCHAR sLastName[51], sFirstName[51], sHotelName[51], sTransDate[11];
        //int nDays, nGuest_ID, nCount;
        int nGuest_ID, nQuantity, nUnitPrice, nCount, nHotelID, nItemID;
        //VARCHAR sInCity[11];
        VARCHAR sItemName[31], sTaxable[11];
        VARCHAR sUserID[21], sPassword[21];
    exec sql end declare section;
/////// begin needs work ///////
        // Now define the cursor we will use to get all of the charges that the guest incurred at all hotels
    exec sql declare dbGuest cursor for
        Select G.Guest_ID, G.Last_Name, G.First_Name, C.Item_ID, C.Item_Name, C.Quantity, C.Unit_Price, C.Trans_Date, H.Hotel_Name, H.Hotel_ID, SI.Taxable
        From Hotel H, Charge C, Stay S, Guest G, Sales_Item SI Where
        C.Stay_ID=S.Stay_ID And H.Hotel_ID=S.Hotel_ID And G.Guest_ID=S.Guest_ID
            And SI.Item_ID=C.Item_ID
        Group By S.Guest_ID;
//////// end needs work ///////
    // Set up the user-id and password to access my database
    // Because we are using the local database on this server
    // we don't need to use any database location or SID
    strcpy(sUserID.arr,"myusername"); 
    strcpy(sPassword.arr,"mypassword"); 
    sUserID.len=strlen(sUserID.arr);
    sPassword.len=strlen(sPassword.arr);
    exec sql connect :sUserID identified by :sPassword;

    // sqlca.sqlcode is a variable that is set based on the last command sent in to the database
    // a value anything other than zero for what we just did (connect to the database) indicates
    // a error.
    if(sqlca.sqlcode !=0)
       {
        //printf("Sorry, cannot connect to server, pgm aborted %s\n",sqlca.sqlcode); //correction 2/5/14
        printf("Sorry, cannot connect to server, pgm aborted %d\n",sqlca.sqlcode); //change to %d
        exit(1);
       }
    //we made it here, so we were able to open the database correctly
    exec sql SELECT COUNT(*) INTO :nCount FROM Guest;
    printf ("There are %d Guests.\n",nCount);
    for(;;){
        // Read in through stdio the Guest we want to query, then set it up do we can use it
        printf("Enter a Guest_ID(type exit to terminate)>>\n");
        scanf("%d",nGuest_ID);
        //Guest_ID.len= strlen(Guest_ID.arr);
        if(nGuest_ID==0)
        {
            printf("BYE\n");
            exit(0);
        }
        printf("%s %s %s %s %d\n","Charge Summary for:", sFirstName.arr, sLastName.arr, " Guest_ID:", nGuest_ID);
        //printf("I do not work yet (type exit to terminate)>>\n");
                // Open our cursor and begin reading records
        exec sql open dbGuest;
        for(;;)
        {
            //exec sql fetch dbGuest into :nGuest_ID, :sLastName, :sFirstName, :sHotelName, :sCheckInDate, :nDays, :sRoom;
            exec sql fetch dbGuest into :nGuest_ID, :sLastName, :sFirstName, :nItemID, :sItemName, :nQuantity, :nUnitPrice, :sTransDate, :sHotelName, :nHotelID;
            if(sqlca.sqlcode !=0)  // If anything went wrong or we read past eof, stop the loop
            {
                break;
            }
            // Do the crazy stuff to end the C-Strings
            sLastName.arr[sLastName.len] = 0;
            sFirstName.arr[sFirstName.len] = 0;
            sItemName.arr[sItemName.len] = 0;
            sTransDate.arr[sTransDate.len] = 0;
            sHotelName.arr[sHotelName.len] = 0;

            // Print out the information for this guest
            printf("%s %d %s %s \n", "Sales_Item: ", nItemID, " - ", sItemName.arr);
        }
        // close the cursor and end the program
        exec sql close dbGuest ;
    }
    exit(0);
}

I'm sure I'm making some simple mistake but I didn't find anything helpful on search. I'm running this on a server, and I'm not getting any debugging back (this is the only major bug I haven't been able to solve up to this point), so what you have is what I have. Normally C programs would be run in debuggers but this is ProC and I'm kind of lost with the whole Oracle ProC debugging thing (since it's running on a remote database). With this kind of error I'd usually suspect not allocating memory properly, but I don't see anything like that here.

Went through these but not helpful:

Segmentation fault (core dumped) runtime error in C

Not so Useful Error -- Segmentation Fault (Core Dump) in Homework Assignment

Segmentation Fault(core dumped)

Segmentation fault (core dumped) read from stdin

Answer 1

Since nGuest_ID is an int, when calling scanf(), you'll need to provide address of nGuest_ID:

scanf("%d",&nGuest_ID);

That's the likely cause of the core dump you're experiencing, but, also, OracleUser made some excellent suggestions.

Hope that helps.