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SHA1: 8ef09a1e8a1a6c7f6e7131ce3180136033180232
User & Date: msofer 2015-03-23 13:43:37
Context
2015-03-23
13:46
fix comments describing tailcall implementation check-in: 654bad187e user: msofer tags: trunk
13:43
more comments Closed-Leaf check-in: 8ef09a1e8a user: msofer tags: mig-tailcall-cleanup
02:11
updated, improved tailcall comments check-in: cf96e3ae67 user: msofer tags: mig-tailcall-cleanup
Changes
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Changes to generic/tclBasic.c.

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 * The steps of the tailcall dance are as follows:
 *
 *   1. when [tailcall] is invoked, it stores the corresponding callback in
 *      the current CallFrame and returns TCL_RETURN
 *   2. when the CallFrame is popped, it calls TclSetTailcall to store the
 *      callback in the proper NRCommand callback - the spot where the command
 *      that pushed the CallFrame is completely cleaned up
 *   3. The NRCommand schedules the tailcall callback to run immediately after
 *      NRCommand returns
 *
 *   One delicate point is to properly define the NRCommand where the tailcall
 *   will execute. There are functions whose purpose is to help define the
 *   precise spot: TclMarkTailcall ("this is the spot") and TclSkipTailcall
 *   ("skip the next command: we are redirecting to it, tailcalls should run
 *   after WE return"), TclPushTailcallPoint (special for OO).
 */
................................................................................
TclPushTailcallPoint(
    Tcl_Interp *interp)
{
    TclNRAddCallback(interp, NRCommand, NULL, NULL, NULL, NULL);
    ((Interp *) interp)->numLevels++;
}













void
TclSetTailcall(
    Tcl_Interp *interp,
    Tcl_Obj *listPtr)
{
    /*
     * Find the splicing spot: right before the NRCommand of the thing
................................................................................
    }
    if (!runPtr) {
        Tcl_Panic("tailcall cannot find the right splicing spot: should not happen!");
    }
    runPtr->data[1] = listPtr;
}


















int
TclNRTailcallObjCmd(
    ClientData clientData,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const objv[])
{
................................................................................
 	TclListObjSetElement(interp, listPtr, 0, nsObjPtr);
        
        iPtr->varFramePtr->tailcallPtr = listPtr;
    }
    return TCL_RETURN;
}












int
TclNRTailcallEval(
    ClientData data[],
    Tcl_Interp *interp,
    int result)
{
    Interp *iPtr = (Interp *) interp;






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 * The steps of the tailcall dance are as follows:
 *
 *   1. when [tailcall] is invoked, it stores the corresponding callback in
 *      the current CallFrame and returns TCL_RETURN
 *   2. when the CallFrame is popped, it calls TclSetTailcall to store the
 *      callback in the proper NRCommand callback - the spot where the command
 *      that pushed the CallFrame is completely cleaned up
 *   3. when the NRCommand callback runs, it schedules the tailcall callback
 *      to run immediately after it returns
 *
 *   One delicate point is to properly define the NRCommand where the tailcall
 *   will execute. There are functions whose purpose is to help define the
 *   precise spot: TclMarkTailcall ("this is the spot") and TclSkipTailcall
 *   ("skip the next command: we are redirecting to it, tailcalls should run
 *   after WE return"), TclPushTailcallPoint (special for OO).
 */
................................................................................
TclPushTailcallPoint(
    Tcl_Interp *interp)
{
    TclNRAddCallback(interp, NRCommand, NULL, NULL, NULL, NULL);
    ((Interp *) interp)->numLevels++;
}

 
/*
 *----------------------------------------------------------------------
 *
 * TclSetTailcall --
 *
 *	Splice a tailcall command in the proper spot of the NRE callback
 *	stack, so that it runs at the right time.
 *
 *----------------------------------------------------------------------
 */

void
TclSetTailcall(
    Tcl_Interp *interp,
    Tcl_Obj *listPtr)
{
    /*
     * Find the splicing spot: right before the NRCommand of the thing
................................................................................
    }
    if (!runPtr) {
        Tcl_Panic("tailcall cannot find the right splicing spot: should not happen!");
    }
    runPtr->data[1] = listPtr;
}

 
/*
 *----------------------------------------------------------------------
 *
 * TclNRTailcallObjCmd --
 *
 *	Prepare the tailcall as a list and store it in the current
 *	varFrame. When the frame is later popped the tailcall will be spliced
 *	at the proper place.
 *
 * Results:
 *	The first NRCommand callback that is not marked to be skipped is
 *	updated so that its data[1] field contains the tailcall list.
 *
 *----------------------------------------------------------------------
 */

int
TclNRTailcallObjCmd(
    ClientData clientData,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const objv[])
{
................................................................................
 	TclListObjSetElement(interp, listPtr, 0, nsObjPtr);
        
        iPtr->varFramePtr->tailcallPtr = listPtr;
    }
    return TCL_RETURN;
}

 
/*
 *----------------------------------------------------------------------
 *
 * TclNRTailcallEval --
 *
 *	This NREcallback actually causes the tailcall to be evaluated.
 *
 *----------------------------------------------------------------------
 */

int
TclNRTailcallEval(
    ClientData data[],
    Tcl_Interp *interp,
    int result)
{
    Interp *iPtr = (Interp *) interp;