SysError
SysError Perform action normally taken upon a system error #include System Error Codes
short errID ; Error to simulate.
SysError is called by the system when a catastrophic error occurs. It
displays the "Sorry, a system error..." dialog (with the bomb icon) and takes
some precise steps, as described below.
errID is a System Error Code, such as dsAddressError, and so forth.
Notes: You usually won't use this in an application, but it is handy for testing
your "resume" proc (as setup via InitDialogs), and some applications may find reasons to intercept this trap.
This function relies heavily on something called the "Sytem Alert Table
which gets loaded at startup. A pointer to it gets stored into the global
variable DSAlertTab, at 0x2BA. For details, see Inside Macintosh, Volume 2,
page 359.
The steps taken by the system error handler are as follows:
1 Save all registers
2 Store errID in global variable DSErrCode
3 Check DSAlertTab and if no error table in memory, draw Sad Mac Icon
3 Allocate memory for Quickdraw globals on stack and initialize a GrafPort for use in the error dialog.
4 If errID is < 0 the alert box will not be drawn (redrawn).
5 If errID matches an entry in the error alert table, display an
error-specific message, otherwise, display the generic "Sorry, a system
error occurred" message.
6 Draw the alert in the global- coordinates of the Rect in global variable 7 If the string IDs in the alert table are non-0, draw both strings.
8 If the Icon ID in the alert table is non-0, draw the icon.
9 If the procedure definition ID in the alert table is non-0, execute the
procedure.
10 If the button definition ID in the alert table is 0, return to the caller.
11 If there's a resume procedure, increment the button definition ID by one.
12 Draw the buttons matching the button definition ID from the alert table.
13 Hit-test the buttons. If a resume-proc exists, and Resume is clicked, set the stack pointer to the value in CurStackBase (throwing away the stack),
set A5 to what is was earlier, and jump to resume procedure.
14 Return to the caller.
Notice that "resume procedures" must be written with the assumption that
the stack has been lost so there is no "return address". After performing
whatever error recovery is possible, the routine must be able to jump to a
known "starting point" in the program.