Looks like we have a problem Houston! I reported in an earlier post that we have been playing around with the QUILNGTX API and found a problem where the message was was overwriting the data stored in the UIM Panel on return. Looks like its a problem with the ILEC compiler and array bounds checking! IBM asked a very valid question how did we declare the variable being passed as the message, I reviewed the code and found we declared the character array with a maximum size of 255 bytes. This is just a legacy from previous message calls we made and didn’t strike a chord when we used the same declaration. We had the call to the popup window before the call to the QUIPUTV API which loads the panel variables initially but found that moving the call after the QUIPUTV call fixed up the issue we were seeing. So we felt that the problem was with the API and it was writing the data over the variable pool used for UIM. Wrong! Its is our building of the message that was creating the problem. We used a call to sprintf to build the first part of the message and multiple calls to the strcat function to add further data. No where did we get any error or warning messages even when we ran to programs. Our array is still overwriting memory it doesn’t own but we were fortunate (or not) that moving the API call masked the problem!

Looks like we need to ensure we do our own array bounds checking within every program as the compiler is not doing any which is what I thought it was? Here is the sample code which caused the problem.

#define MAX_MSG 255
char msg_dta[MAX_MSG];

if(Check_SMTP_Addr(RapRec.SMTPSRV) != 1) {
               /* set the error message and display again */
               Dsp_Err = 1;
               memcpy(smtpsts.srvaddr,RapRec.SMTPSRV,MAX_SMTP_NAME);
               smtpsts.flag = 0xf1;
               sprintf(msg_dta,"An attempt to contact the  SMTP server you ");
               strcat(msg_dta,"entered has failed.  Before the server can be");
               strcat(msg_dta,"configured the program must be able to ");
               strcat(msg_dta,"contact the server to verify its ");
               strcat(msg_dta,"authenticity. Please enter a valid SMTP ");
               strcat(msg_dta,"server address or *NONE ");
               strcat(msg_dta,"Here is some additional data which is not");
               strcat(msg_dta," part of the final message we will ship ");
               strcat(msg_dta,"but should show the problem????");
               Show_Popup_Error(msg_dta);
               QUIPUTV(applHandle,
                       &smtpsts,
                       sizeof(smtpsts),
                       "SMTPSTS   ",
                       &Error_Code);
               if(Error_Code.EC.Bytes_Available > 0) {
                  snd_error_msg(Error_Code);
                  exit(-1);
                  }

               }
            }

int Show_Popup_Error(char *message) {
int MsgLen = 0;
char Msg_Id[7] = "GEN0001";                 /* Message ID */
char Q_File_Name[20] = "RAPMSGF   *LIBL     "; /* Message file */
EC_t Error_Code = {'0'};                    /* Error Code struct */

Error_Code.EC.Bytes_Provided = sizeof(Error_Code);
MsgLen = strlen(message);

QUILNGTX(message,
         MsgLen,
         Msg_Id,
         Q_File_Name,
         &Error_Code);
if(Error_Code.EC.Bytes_Available > 0) {
   snd_error_msg(Error_Code);
   }
}  

As you can see I added some additional text to the message to show the problem occurring, I should have recognized the msg_dta array was being over filled but never thought about it!

So if you start to see some strange behavior when using arrays like this, understand that the ILEC compiler does not do array bounds checking by default (if at all?). I know other ILE compilers such as RPG do, so IBM may want to spend a little extra money on the C compiler and improve its capabilities (DIG). The latest code doesn’t use any of the techniques used in the above code so its not even a issue, this code was simply used to try out the call to the QUILNGTX API.

Chris…

I have written numerous times now about the problems I have been having getting messages to be displayed to the right panel in UIM. I finally gave up trying to get the messages to show on the message line as no matter how I configured the QMHSNDPM API it would not place the message on the right panel once I started to nest panels. I then looked at the QUILNGTX API, it seemed to be capable of doing what I needed but did not appear to be UIM based (no application handle has to be sent to it!) so I was dubious about using it as an alternative. I had looked at simply using the QUIADDPW API and building the popups according to the type of panel I was using, but this seemed to be a simpler approach.

We started to code up the call to the API by passing in text which was built within the program using SPRINTF and STRCAT functions, the are some problems with this which IBM is looking into at the moment but overall it worked. The problem IBM is looking into is the placement of the call to the API in relation to other UIM calls which gave incorrect output, we moved the API calls around and fixed the problem temporarily and hope IBM can fix the problem permanently. The point is we can now have error messages sent to a popup window which is correctly placed over the right panel.

At first I was determined to get the messages to display at the bottom of the panel as this seemed to be the right approach and simply taking another route due to the difficulty of achieving that didn’t fit in with our mantra of trying to do it the right way. Having looked at the results we feel this is probably a better solution, if this was a GUI solution we would probably use a Dialog Box to display the message, so using a popup window is not unlike using that approach is it?

The code for the initial call to the API is below, we have altered this significantly to support replacement text and correct use of message files and allow the message to be formatted a little better.

int Show_Popup_Error(char *message) {
int MsgLen = 0;
char Msg_Id[7] = "GEN0001";                 /* Message ID */
char Q_File_Name[20] = "RAPMSGF   *LIBL     "; /* Message file */
EC_t Error_Code = {'0'};                    /* Error Code struct */

Error_Code.EC.Bytes_Provided = sizeof(Error_Code);
MsgLen = strlen(message);

QUILNGTX(message,
         MsgLen,
         Msg_Id,
         Q_File_Name,
         &Error_Code);
if(Error_Code.EC.Bytes_Available > 0) {
   snd_error_msg(Error_Code);
   }
} 

Note, the message passed in must be NULL terminated for this to work, The MsgID passed in will be used to determine the title of the popup window only. Again there appears to be a problem with that which we have asked IBM to comment on. The Message ID we passed in ‘GEN0001′ has no message text or help text so it did not show up the title problems.

I hope this helps others like us who have become frustrated with trying to get messages displayed at the bottom of display panels!

Chris…