Caché ObjectScript Reference - InterSystems Documentation

$ESTACK$ESTACKContains the number of context frames saved on the call stack from a user-defined point.$ESTACK$ESDescription$ESTACK contains the number of context frames saved on the call stack for your job froma user-defined point. You specify this point by creating a new copy of $ESTACK using theNEW command.The $ESTACK special variable is similar to the $STACK special variable. Both contain thenumber of context frames currently saved on the call stack for your job or process. Cachéincrements and restores both when changing context. The major difference is that you canreset the $ESTACK count to zero at any point by using the NEW command. You cannotreset the $STACK count.Context Frames and Call StacksWhen a Caché image is started, before any contexts have been saved on the call stack, thevalues of both $ESTACK and $STACK are zero. Each time a routine calls another routinewith DO, Caché saves the context of the currently executing routine on the call stack, increments$ESTACK and $STACK, and starts execution of the called routine in the newly-createdcontext. The called routine can, in turn, call another routine, and so on. Each time anotherroutine is called, Caché increments $ESTACK and $STACK and places more saved contextson the call stack.Issuing a DO command, an XECUTE command, or a call to a user-defined function establishesa new execution context. Issuing a GOTO command does not.As DO commands, XECUTE commands, or user-defined function references create newcontexts, Caché increments the values of $STACK and $ESTACK. As QUIT commandscause contexts to exit, Caché restores the previous contexts from the call stack and decrementsthe values of $STACK and $ESTACK.The $ESTACK and $STACK special variables cannot be modified using the SET command.Attempting to do so results in a error.Creating a New $ESTACKYou can create a new copy of $ESTACK in any context by using the NEW command. Cachétakes the following actions:Caché ObjectScript Reference 423