ErrorMessage function is to be used while inside a function that can be interrupted with a MessagePopup, e.g. some control callback where the user is operating on the user interface or saving data or doing some interruptible piece of code. The use is like this one:
int CVICALLBACK ShowOnePanel (int panel, int control, int event, void *callbackData, int eventData1, int eventData2)
{
int line, error = 0;
if (event != EVENT_COMMIT) return 0;
errChk (tmpH = LoadPanel (0, "MyFile,uir", PANEL));
DisplayPanel (tmpH);
Error:
if (error < 0)
ErrorMessage (error, ERRGEN, line, __FUNCTION__, __FILE__);
return 0;
}
In this code, if LoadPanel returns an error, errChk macro lets the program jump to Error label where ErrorMessage displays a properly formatted error message.
On the other hand, when you cannot use a popup to inform the operator, you can prepare a memory structure with all relevant informations and display the message in another moment, like in this example:
int SomeFunction (...)
{
int line, error = 0;
errStruct *xe = NULL;
// some line of code
while (TRUE) {
// some line of code
error = some_function_returning_an_error;
if (error < 0) {
// prepare to warn the operator
xe = malloc (sizeor (errStruct));
xe.err = error; // Error code
xe.terr = ERRGEN; // Type of error
xe.line = line; // Line the error raised
strcpy (xe.func, __FUNCTION__); // Function where the error raised
strcpy (xe.file, __FILE__); // Source file where the error raised
// issue a warning in the main thread
PostDeferredCall (WarnMessage, (void *)&xe);
error = 0; // Clear error indicator
}
// the rest of the code
ProcessSystemEvents ();
}
// Stopping active tasks / operations; cleaning environment and so on
return 0;
}
In this case, the next time the system processes events after the error has arised, WarnMessage function will be executed and will prompt the operator with error informations and will dispose of the memory allocate with error informations.
Now, to permit using __FUNCTION__ macro on CVI from 8.5 on you need to enable C)) function within the IDE adding this macro to the code:
// Enable C99 fucntions in CVI
#pragma iso_9899_1999;
On previous CVI releases this is not necessary (but I seem to remember that __FUNCTION__ macro is present only starting from CVI7 - to be confirmed).
I have used variable argument functions with strings without errors: this is an abstract from a function that logs parameters on a string to display them on a textbox:
// Types of parameters ("stdarg.h")
#define INTPRM 1
#define DBLPRM 2
#define CHRPRM 3
Logging function:
// Logging parameters
strcpy (msg, "Parameters");
while ((type = *parms++) != 0) {
switch (type) {
case INTPRM: sprintf (msg, "%s,%d", msg, va_arg (ap, int)); break;
case DBLPRM: sprintf (msg, "%s,%.1f", msg, va_arg (ap, double)); break;
case CHRPRM: sprintf (msg, "%s,%s", msg, va_arg (ap, char *)); break;
}
}
Hope these informations can help you in your job.
