* generic/tclBasic.c: NRE: enabled calling NR commands

	* generic/tclExecute.c:  from the callbacks. Completely
	* generic/tclInt.h:      redone tailcall implementation
	* generic/tclNRE.h:      using the new feature.
	* generic/tclProc.c:
	* tests/NRE.test:

5 files changed, 341 insertions, 242 deletions

diff --git a/generic/tclBasic.c b/generic/tclBasic.c
index eb35aaf..c06a514 100644
--- a/generic/tclBasic.c
+++ b/generic/tclBasic.c
@@ -16,7 +16,7 @@
  * See the file "license.terms" for information on usage and redistribution of
  * this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tclBasic.c,v 1.316 2008/07/18 23:29:41 msofer Exp $
+ * RCS: @(#) $Id: tclBasic.c,v 1.317 2008/07/21 03:43:26 msofer Exp $
  */
 
 #include "tclInt.h"
@@ -129,6 +129,8 @@ static Tcl_NRPostProc	TEOV_Error;
 static Tcl_NRPostProc	TEOEx_ListCallback;
 static Tcl_NRPostProc	TEOEx_ByteCodeCallback;
 
+static Tcl_NRPostProc	TailcallCallback;
+
 /*
  * The following structure define the commands in the Tcl core.
  */
@@ -4082,21 +4084,13 @@ Tcl_EvalObjv(
      * record and proceed with the next call.
      */
 
+  callbackReentryPoint:
     switch(recordPtr->type) {
     case TCL_NR_NO_TYPE:
 	break;
     case TCL_NR_BC_TYPE:
     tcl_nr_bc_type:
 	if (USE_NR_TEBC && tebcCall) {
-	    /*
-	     * We were called by TEBC, and we need a bytecode to be executed:
-	     * just ask our caller to do that.
-	     * TEBC_CALL(iPtr) = TEBC_DO_EXEC = 0 is not really needed, as it
-	     * is already 0==TEBC_DO_EXEC
-	     */
-
-	    TEBC_CALL(iPtr) = TEBC_DO_EXEC;
-	    TEBC_DATA(iPtr) = recordPtr->data.codePtr;
 	    return TCL_OK;
 	}
 
@@ -4107,40 +4101,17 @@ Tcl_EvalObjv(
 
 	result = TclExecuteByteCode(interp, recordPtr->data.codePtr);
 	goto done;
-    case TCL_NR_TAILCALL_TYPE: {
+    case TCL_NR_TAILCALL_TYPE:
 	/*
-	 * Got to save this record, free the stack (i.e., perform all pending
-	 * callbacks) and restore the record.
+	 * Proceed to cleanup the current command, the tailcall will be run
+	 * from the callbacks.
 	 */
 
-	Tcl_Obj *tailObjPtr = recordPtr->data.obj.objPtr;
-
-	result = TclEvalObjv_NR2(interp, result, rootPtr);
-
-	if (result != TCL_OK) {
-	    goto done;
-	}
 	if (USE_NR_TEBC && tebcCall) {
-	    /*
-	     * We were called by TEBC, and we need it to drop a frame: let him
-	     * know.
-	     */
-
-	    TEBC_CALL(iPtr) = TEBC_DO_TAILCALL;
-	    TEBC_DATA(iPtr) = tailObjPtr;
 	    return TCL_OK;
 	}
-
-	/*
-	 * ONLY supported if called from TEBC. Could do an 'uplevel 1'? Run
-	 * from here (as hinted below)? Mmhhh ... FIXME. Maybe tailcalls
-	 * SHOULD actually be bytecompiled (we know how to more or less fake
-	 * it when falling off TEBC)?
-	 */
-
-	Tcl_Panic("tailcall called from a non-compiled command?");
-	/* FALL THROUGH */
-    }
+	recordPtr->type = TCL_NR_NO_TYPE; 
+	break;
     case TCL_NR_CMD_TYPE: {
 	/*
 	 * We got an unshared canonical list to eval , do it from here.
@@ -4182,8 +4153,7 @@ Tcl_EvalObjv(
     case TCL_NR_OBJPROC_TYPE:
 	/*
 	 * This is a rewrite like ns-import does, without a new cmdPtr or new
-	 * reentrant call. FIXME: add the possibility of a new callback
-	 * (Tcl_NRObjProc has that), and maybe also edition of objc/objv?
+	 * reentrant call. FIXME NRE: add edition of objc/objv?
 	 */
 
 	objProc = recordPtr->data.objProc.objProc;
@@ -4195,7 +4165,19 @@ Tcl_EvalObjv(
     }
 
   done:
-    return TclEvalObjv_NR2(interp, result, rootPtr);
+    result = TclEvalObjv_NR2(interp, result, rootPtr);
+    recordPtr = TOP_RECORD(iPtr);
+    if (recordPtr == rootPtr) {
+	return result;
+    }
+
+    /*
+     * A callback scheduled a new evaluation! Deal with it.
+     * Note that recordPtr was already updated right above.
+     */
+
+    assert((result == TCL_OK));
+    goto callbackReentryPoint;
 }
 
 int
@@ -4206,6 +4188,7 @@ TclEvalObjv_NR2(
 {
     Interp *iPtr = (Interp *) interp;
     TEOV_record *recordPtr;
+    TEOV_callback *callbackPtr;
 
     /*
      * If the interpreter has a non-empty string result, the result object is
@@ -4221,17 +4204,41 @@ TclEvalObjv_NR2(
 	(void) Tcl_GetObjResult(interp);
     }
 
-    while (TOP_RECORD(iPtr) != rootPtr) {
-	POP_RECORD(iPtr, recordPtr);
-
+  restart:
+    while ((recordPtr = TOP_RECORD(iPtr)) != rootPtr) {
 	while (recordPtr->callbackPtr) {
-	    TEOV_callback *callbackPtr = recordPtr->callbackPtr;
-
+	    callbackPtr = recordPtr->callbackPtr;
+	    recordPtr->callbackPtr = callbackPtr->nextPtr;
 	    result = callbackPtr->procPtr(callbackPtr->data, interp, result);
-	    callbackPtr = callbackPtr->nextPtr;
-	    TclSmallFree(recordPtr->callbackPtr);
-	    recordPtr->callbackPtr = callbackPtr;
+	    TclSmallFree(callbackPtr);
+
+	    if (recordPtr != TOP_RECORD(iPtr)) {
+
+		if (result != TCL_OK) {
+		    goto restart;
+		}
+		
+		/*
+		 * A callback scheduled a new evaluation; return so that our
+		 * caller can run it.
+		 */
+		
+		switch(recordPtr->type) {
+		    case TCL_NR_NO_TYPE:
+			goto restart;
+		    case TCL_NR_BC_TYPE:
+		    case TCL_NR_CMD_TYPE: 
+		    case TCL_NR_SCRIPT_TYPE:
+			goto done;
+		    case TCL_NR_TAILCALL_TYPE:
+			Tcl_Panic("Tailcall called from a callback!");						
+		    default:
+			Tcl_Panic("TEOV_NR2: invalid record type: %d",
+				recordPtr->type);
+		}
+	    }
 	}
+	TOP_RECORD(iPtr) = recordPtr->nextPtr;
 
 	if (!CHECK_EXTRA(iPtr, recordPtr)) {
 	    Tcl_Panic("TclEvalObjv_NR2: wrong tosPtr?");
@@ -4257,6 +4264,8 @@ TclEvalObjv_NR2(
      * check at the end.
      */
 
+    done:
+    
     if (TclAsyncReady(iPtr)) {
 	result = Tcl_AsyncInvoke(interp, result);
     }
@@ -7394,48 +7403,62 @@ NRPostProcess(
     int objc,
     Tcl_Obj *const objv[])
 {
-    TEOV_record *recordPtr = TOP_RECORD(interp);
-
-    if ((result == TCL_OK) && VALID_NEW_REQUEST(recordPtr)) {
+    TEOV_record *recordPtr, *rootPtr = TOP_RECORD(interp)->nextPtr;
+    
+  restart:
+    recordPtr = TOP_RECORD(interp);
+    if (result == TCL_OK) {
 	switch (recordPtr->type) {
-	case TCL_NR_BC_TYPE:
-	    result = TclExecuteByteCode(interp, recordPtr->data.codePtr);
-	    break;
-	case TCL_NR_CMD_TYPE: {
-	    Tcl_Obj *objPtr = recordPtr->data.obj.objPtr;
-	    int flags = recordPtr->data.obj.flags;
-	    Tcl_Obj **objv;
-	    int objc;
-
-	    Tcl_ListObjGetElements(NULL, objPtr, &objc, &objv);
-	    result = Tcl_EvalObjv(interp, objc, objv, flags);
-	    break;
-	}
-	case TCL_NR_SCRIPT_TYPE: {
-	    Tcl_Obj *objPtr = recordPtr->data.obj.objPtr;
-	    int flags = recordPtr->data.obj.flags;
-
-	    result = TclEvalObjEx(interp, objPtr, flags, NULL, 0);
-	    break;
-	}
-	case TCL_NR_OBJPROC_TYPE: {
-	    Tcl_ObjCmdProc *objProc = recordPtr->data.objProc.objProc;
-	    ClientData clientData = recordPtr->data.objProc.clientData;
-
-	    if (!objc) {
-		Tcl_Panic("NRPostProcess: something is very wrong!");
+	    case TCL_NR_NO_TYPE:
+		break;
+	    case TCL_NR_BC_TYPE:
+		result = TclExecuteByteCode(interp, recordPtr->data.codePtr);
+		break;
+	    case TCL_NR_TAILCALL_TYPE:
+		Tcl_SetResult(interp,
+			"impossible to tailcall from a non-NRE enabled command",
+			TCL_STATIC);
+		result = TCL_ERROR;
+		break;	    
+	    case TCL_NR_CMD_TYPE: {
+		Tcl_Obj *objPtr = recordPtr->data.obj.objPtr;
+		int flags = recordPtr->data.obj.flags;
+		Tcl_Obj **objv;
+		int objc;
+
+		Tcl_ListObjGetElements(NULL, objPtr, &objc, &objv);
+		result = Tcl_EvalObjv(interp, objc, objv, flags);
+		break;
 	    }
-	    result = (*objProc)(clientData, interp, objc, objv);
-	    break;
-	}
-	default:
-	    Tcl_Panic("NRPostProcess: invalid record type: %d",
-		    recordPtr->type);
+	    case TCL_NR_SCRIPT_TYPE: {
+		Tcl_Obj *objPtr = recordPtr->data.obj.objPtr;
+		int flags = recordPtr->data.obj.flags;
+		
+		result = TclNREvalObjEx(interp, objPtr, flags, NULL, 0);
+		break;
+	    }
+	    case TCL_NR_OBJPROC_TYPE: {
+		Tcl_ObjCmdProc *objProc = recordPtr->data.objProc.objProc;
+		ClientData clientData = recordPtr->data.objProc.clientData;
+		
+		if (!objc) {
+		    Tcl_Panic("NRPostProcess: something is very wrong!");
+		}
+		result = (*objProc)(clientData, interp, objc, objv);
+		break;
+	    }
+	    default:
+		Tcl_Panic("NRPostProcess: invalid record type: %d",
+			recordPtr->type);
 	}
     }
-
-    assert((TOP_RECORD(interp) == recordPtr));
-    return TclEvalObjv_NR2(interp, result, recordPtr->nextPtr);
+    
+    result = TclEvalObjv_NR2(interp, result, rootPtr);
+    if (TOP_RECORD(interp) != rootPtr) {
+	assert((result == TCL_OK));
+	goto restart;
+    }
+    return result;
 }
 
 /*
@@ -7599,11 +7622,12 @@ Tcl_NRObjProc(
  *	      (b) 'a' is looked up in the returning frame's namespace, but the
  *		  command is run in the context to which we are returning
  *       Current implementation does this if [tailcall] is called from within
- *       a proc, panics otherwise-
+ *       a proc, errors otherwise.
  *   (2) Should a tailcall bypass [catch] in the returning frame? Current
- *       implementation does not - it causes an error.
+ *       implementation does not (or does it? Changed, test!) - it causes an
+ *       error. 
  *
- * FIXME!
+ * FIXME NRE!
  */
 
 int
@@ -7614,25 +7638,122 @@ TclTailcallObjCmd(
     Tcl_Obj *const objv[])
 {
     Interp *iPtr = (Interp *) interp;
-    TEOV_record *recordPtr = TOP_RECORD(interp);
+    TEOV_record *rootPtr = TOP_RECORD(interp);
+    TEOV_callback *headPtr, *tailPtr;
+    TEOV_record *tmpPtr;
     Tcl_Obj *listPtr;
-
-    /*
-     * Do NOT allow tailcall to be called from a non-proc/lambda: tough to
-     * manage the proper semantics, especially for [uplevel $x tailcall foo]
-     */
+    Command *cmdPtr;
+    Namespace *nsPtr = iPtr->varFramePtr->nsPtr;
 
     if (!iPtr->varFramePtr->isProcCallFrame) {
+	/* FIXME! Why error? Just look if we have a TEOV above! */
 	Tcl_SetResult(interp,
 	    "tailcall can only be called from a proc or lambda", TCL_STATIC);
 	return TCL_ERROR;
     }
-
+    
+    nsPtr->activationCount++;
     listPtr = Tcl_NewListObj(objc-1, objv+1);
-    Tcl_NREvalObj(interp, listPtr, 0);
-    recordPtr->type = TCL_NR_TAILCALL_TYPE;
+    rootPtr->type = TCL_NR_TAILCALL_TYPE;
+
+    /*
+     * Add a callback to perform the tailcall as LAST item in the caller's
+     * callback stack.
+     * Find the first record for the caller: start at the one below the top
+     * (the top being this command's record), and go back until you find
+     * the one that contains the cmdPtr.
+     */
+    
+    tmpPtr = rootPtr->nextPtr;
+    while (tmpPtr->cmdPtr == NULL) {
+	tmpPtr = tmpPtr->nextPtr;
+    }
+
+    /*
+     * Now find the first and last callbacks in this record, and temporarily
+     * set the callback list to empty.
+     */
+    
+    headPtr = tailPtr = tmpPtr->callbackPtr;
+    if (headPtr) {
+	while (tailPtr->nextPtr) {
+	    tailPtr = tailPtr->nextPtr;
+	}
+	tmpPtr->callbackPtr = NULL;
+    }
+
+    /*
+     * Temporarily put tmpPtr as the TOP_RECORD, register a callback, then
+     * replug things back the way they were.
+     */
+
+    TOP_RECORD(iPtr) = tmpPtr;
+    TclNRAddCallback(interp, TailcallCallback, listPtr, nsPtr, NULL, NULL);
+    TOP_RECORD(iPtr) = rootPtr;
+    
+    if (headPtr) {
+	tailPtr->nextPtr = tmpPtr->callbackPtr;
+	tmpPtr->callbackPtr = headPtr;
+    }
+
     return TCL_OK;
 }
+
+static int
+TailcallCallback(
+    ClientData data[],
+    Tcl_Interp *interp,
+    int result)
+{
+    Interp *iPtr = (Interp *) interp;
+    Tcl_Obj *listPtr = data[0], *namePtr;
+    Namespace *nsPtr = data[1];
+    TEOV_record *recordPtr = TOP_RECORD(iPtr);
+    Command *cmdPtr;
+    
+    if (!recordPtr->cmdPtr || recordPtr->callbackPtr) {
+	Tcl_Panic("TailcallCallback: should not happen!");
+    }
+
+    result = Tcl_ListObjIndex(interp, listPtr, 0, &namePtr);
+    if (result == TCL_OK) {
+	cmdPtr = TEOV_LookupCmdFromObj(interp, namePtr, nsPtr);
+    }
+
+    nsPtr->activationCount--;
+    if ((nsPtr->flags & NS_DYING)
+	    && (nsPtr->activationCount - (nsPtr == iPtr->globalNsPtr) == 0)) {
+	/*
+	 * FIXME NRE tailcall: is this the proper way to manage this? This is
+	 * like what CallFrames do.
+	 */
+
+	Tcl_DeleteNamespace((Tcl_Namespace *) nsPtr);
+    }
+    
+    if (!cmdPtr || (result != TCL_OK)) {
+	Tcl_DecrRefCount(listPtr);
+	Tcl_SetResult(interp,
+	    "the command to be tailcalled does not exist", TCL_STATIC);
+	return TCL_ERROR;
+    }	
+
+    /*
+     * Take over the previous command's record.
+     */
+    
+    TclCleanupCommandMacro(recordPtr->cmdPtr);
+    recordPtr->cmdPtr = cmdPtr;
+    cmdPtr->refCount++;
+    
+    /*
+     * Push a new record to signal that a new command was scheduled.
+     */
+
+    PUSH_RECORD(iPtr, recordPtr);
+    iPtr->lookupNsPtr = nsPtr;
+    return TclNREvalCmd(interp, listPtr, 0);
+}
 
 void
 Tcl_NRAddCallback(
diff --git a/generic/tclExecute.c b/generic/tclExecute.c
index 7b9ae49..6243266 100644
--- a/generic/tclExecute.c
+++ b/generic/tclExecute.c
@@ -14,7 +14,7 @@
  * See the file "license.terms" for information on usage and redistribution of
  * this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tclExecute.c,v 1.382 2008/07/18 23:29:43 msofer Exp $
+ * RCS: @(#) $Id: tclExecute.c,v 1.383 2008/07/21 03:43:30 msofer Exp $
  */
 
 #include "tclInt.h"
@@ -25,9 +25,6 @@
 #include <math.h>
 #include <float.h>
 
-static Tcl_NRPostProc TailcallFromTebc;
-
-
 /*
  * Hack to determine whether we may expect IEEE floating point. The hack is
  * formally incorrect in that non-IEEE platforms might have the same precision
@@ -1757,10 +1754,6 @@ TclExecuteByteCode(
     BottomData *bottomPtr;
 #if USE_NR_TEBC
     BottomData *oldBottomPtr = NULL;
-
-    /* for tailcall support */
-    Namespace *lookupNsPtr = NULL;
-    Tcl_Obj *tailObjPtr = NULL;
 #endif
     
     /*
@@ -1800,7 +1793,10 @@ TclExecuteByteCode(
 
     register int cleanup;
     Tcl_Obj *objResultPtr;
-
+    int evalFlags = TCL_EVAL_NOERR;
+#if (USE_NR_TEBC)
+    int tailcall = 0;
+#endif    
     /*
      * Result variable - needed only when going to checkForcatch or other
      * error handlers; also used as local in some opcodes.
@@ -1880,24 +1876,9 @@ TclExecuteByteCode(
 	bcFramePtr->data.tebc.pc = NULL;
 	bcFramePtr->cmd.str.cmd = NULL;
 	bcFramePtr->cmd.str.len = 0;
-#if USE_NR_TEBC
-    } else if (tailObjPtr) {
-	/*
-	 * A request to perform a tailcall; a frame has already been dropped,
-	 * so we just have to ...
-	 * (Note that we already have a refcount for tailObjPtr!)
-	 */
-
-	*++tosPtr = tailObjPtr;
-	tailObjPtr = NULL;
-	iPtr->lookupNsPtr = lookupNsPtr;
-	lookupNsPtr = NULL;
-	
-	/*
-	 * Fake pc, INST_EVAL STK will fix this and resume properly
-	 */
-	pc--;
-	goto tailCallEntryPoint;
+#if (USE_NR_TEBC)
+    } else if (tailcall) {
+	    goto tailcallEntry;	    
 #endif
     } else {
 	/*
@@ -2497,7 +2478,11 @@ TclExecuteByteCode(
 
 	int objc, pcAdjustment;
 	Tcl_Obj **objv;
-
+#if (USE_NR_TEBC)
+	TEOV_record *recordPtr;
+	ByteCode *newCodePtr;
+#endif
+	
 	case INST_EXPR_STK: {
 	    /*
 	     * Moved here to support transforming the eval of an expression to
@@ -2505,13 +2490,12 @@ TclExecuteByteCode(
 	     */
 
 #if (USE_NR_TEBC)
-
 	    pcAdjustment = 1;
 	    cleanup = 1;
 	    bcFramePtr->data.tebc.pc = (char *) pc;
 	    iPtr->cmdFramePtr = bcFramePtr;	    
 	    DECACHE_STACK_INFO();
-	    TEBC_DATA(iPtr) = CompileExprObj(interp, OBJ_AT_TOS);
+	    newCodePtr = CompileExprObj(interp, OBJ_AT_TOS);
 	    CACHE_STACK_INFO();
 	    goto tebc_do_exec;
 #else
@@ -2536,8 +2520,28 @@ TclExecuteByteCode(
 #endif
 	}
 
+#if (USE_NR_TEBC)
+	tailcallEntry: {
+	    TEOV_record *recordPtr = TOP_RECORD(iPtr);
 
-	tailCallEntryPoint:
+	    /*
+	     * We take over the record's object, with its refCount. Clear the
+	     * record type so that it is not freed again when popping the
+	     * record. 
+	     */
+	    
+	    recordPtr->type = TCL_NR_NO_TYPE;
+	    *++tosPtr = recordPtr->data.obj.objPtr;
+	    evalFlags = recordPtr->data.obj.flags;
+	    recordPtr->type = TCL_NR_NO_TYPE;
+#ifdef TCL_COMPILE_DEBUG
+		if (traceInstructions) {
+		    fprintf(stdout, "   Tailcall: pushing obj with refCount %i\n",
+			    (OBJ_AT_TOS)->refCount);
+		}
+#endif
+	}
+#endif
 	case INST_EVAL_STK: {
 	    /*
 	     * Moved here to support transforming the eval of objects to a
@@ -2546,16 +2550,25 @@ TclExecuteByteCode(
 	     */
 	    
 	    Tcl_Obj *objPtr = OBJ_AT_TOS;
-	    ByteCode *newCodePtr;
 
-	    pcAdjustment = 1;
 	    cleanup = 1;
-
+	    pcAdjustment = !tailcall;
+	    tailcall = 0;
+		
 	    if (objPtr->typePtr == &tclListType) {	/* is a list... */
 		List *listRepPtr = objPtr->internalRep.twoPtrValue.ptr1;
+		Tcl_Obj *copyPtr;
 		
 		if (objPtr->bytes == NULL ||	/* ...without a string rep */
-			listRepPtr->canonicalFlag) {/* ...or that is canonical */
+			listRepPtr->canonicalFlag) {/* ...or that is canonical
+						     * */
+		    if (Tcl_IsShared(objPtr)) {
+			copyPtr = TclListObjCopy(interp, objPtr);
+			Tcl_IncrRefCount(copyPtr);
+			OBJ_AT_TOS = copyPtr;
+			listRepPtr = copyPtr->internalRep.twoPtrValue.ptr1;
+			Tcl_DecrRefCount(objPtr);			
+		    }
 		    objc = listRepPtr->elemCount;
 		    objv = &listRepPtr->elements;
 		    goto doInvocationFromEval;
@@ -2576,8 +2589,7 @@ TclExecuteByteCode(
 		 */
 #if (USE_NR_TEBC)
 		bcFramePtr->data.tebc.pc = (char *) pc;
-		iPtr->cmdFramePtr = bcFramePtr;		
-		TEBC_DATA(iPtr) = newCodePtr;
+		iPtr->cmdFramePtr = bcFramePtr;
 		goto tebc_do_exec;
 #else
 		result = TclExecuteByteCode(interp, newCodePtr);
@@ -2692,49 +2704,50 @@ TclExecuteByteCode(
 
 	    DECACHE_STACK_INFO();
 
+#if (USE_NR_TEBC)
 	    TEBC_CALL(iPtr) = 1;
-	    result = Tcl_EvalObjv(interp, objc, objv, TCL_EVAL_NOERR);
+	    recordPtr = TOP_RECORD(iPtr);
+#endif
+	    result = Tcl_EvalObjv(interp, objc, objv, evalFlags);
 	    CACHE_STACK_INFO();
 #if (USE_NR_TEBC)
-	    switch (TEBC_CALL(iPtr)) {
-		case TEBC_DO_EXEC: {
+	    evalFlags = TCL_EVAL_NOERR;
+	    if (TOP_RECORD(iPtr) != recordPtr) {
+		assert((result == TCL_OK));
+		recordPtr = TOP_RECORD(iPtr);
+		switch(recordPtr->type) {
+		case TCL_NR_BC_TYPE:
+		    newCodePtr = recordPtr->data.codePtr;
 		tebc_do_exec:
 		    /*
 		     * A request to execute a bytecode came back. We save
 		     * the current state and restart at the top.
 		     */
-		    assert((result == TCL_OK));
-		    TEBC_CALL(iPtr) = 0;
+
 		    pc += pcAdjustment;
 		    NR_DATA_BURY(); /* this level's state variables */
-		    codePtr = TEBC_DATA(iPtr);
-		    result = TCL_OK;
+		    codePtr = newCodePtr;
 		    goto nonRecursiveCallStart;
-		}
-		case TEBC_DO_TAILCALL: {
+		case TCL_NR_TAILCALL_TYPE:
 		    /*
-		     * A request to perform a tailcall: save the current
-		     * namespace, drop a frame and eval the passed listObj
-		     * in the previous frame while looking up the command
-		     * in the current namespace. Read it again.
-		     *
-		     * We take over tailObjPtr's refcount!
+		     * A request to perform a tailcall: just drop this
+		     * bytecode as it is; the tailCall has been scheduled in
+		     * the callbacks.
 		     */
-		    
-		    assert((result == TCL_OK));
-		    TEBC_CALL(iPtr) = 0;
-		    tailObjPtr = TEBC_DATA(iPtr);
+#ifdef TCL_COMPILE_DEBUG
+		    if (traceInstructions) {
+			fprintf(stdout, "   Tailcall: request received\n");
+		    }
+#endif
 		    if (catchTop != initCatchTop) {
 			result = TCL_ERROR;
 			Tcl_SetResult(interp,"Tailcall called from within a catch environment",
 				TCL_STATIC);
-			Tcl_DecrRefCount(tailObjPtr);
-			tailObjPtr = NULL;
 			goto checkForCatch;
 		    }
-		    lookupNsPtr = iPtr->varFramePtr->nsPtr;
-		    result = TCL_OK;
 		    goto abnormalReturn; /* drop a level */
+		default:
+		    Tcl_Panic("TEBC: TEOV sent us a record we cannot handle!");
 		}
 	    }
 #endif
@@ -2742,7 +2755,6 @@ TclExecuteByteCode(
 
 	    if (result == TCL_OK) {
 		Tcl_Obj *objPtr;
-
 #ifndef TCL_COMPILE_DEBUG
 		if (*(pc+pcAdjustment) == INST_POP) {
 		    NEXT_INST_V((pcAdjustment+1), cleanup, 0);
@@ -7760,14 +7772,49 @@ TclExecuteByteCode(
 	 *
 	 * NR_TEBC
 	 */
-	
 	bottomPtr = oldBottomPtr;        /* back to old bc */
 	
 	/* Please free anything that might still be on my new stack */
-	result = TclEvalObjv_NR2(interp, result, bottomPtr->recordPtr);
-	assert((TOP_RECORD(iPtr) == bottomPtr->recordPtr));
-	
-	/* restore state variables */
+	if (TOP_RECORD(iPtr) != bottomPtr->recordPtr) {
+	    CACHE_STACK_INFO();
+	    result = TclEvalObjv_NR2(interp, result, bottomPtr->recordPtr);
+	    if (TOP_RECORD(iPtr) != bottomPtr->recordPtr) {
+		TEOV_record *recordPtr = TOP_RECORD(iPtr);
+		
+		assert((result == TCL_OK));
+
+		/*
+		 * A callback scheduled a new evaluation: process it.
+		 */
+
+		switch(recordPtr->type) {
+		    case TCL_NR_BC_TYPE:
+			codePtr = recordPtr->data.codePtr;
+			goto nonRecursiveCallStart;
+		    case TCL_NR_TAILCALL_TYPE:
+			/* FIXME NRE tailcall*/			
+			Tcl_Panic("Tailcall called from a callback!");
+			NR_DATA_DIG();
+			esPtr = iPtr->execEnvPtr->execStackPtr;
+			goto abnormalReturn; /* drop a level */
+		    case TCL_NR_CMD_TYPE: 
+		    case TCL_NR_SCRIPT_TYPE:
+			/*
+			 * FIXME NRE tailcall: error messages will be all wrong?
+			 */
+#ifdef TCL_COMPILE_DEBUG
+			if (traceInstructions) {
+			    fprintf(stdout, "   Tailcall: eval request received from callback\n");
+			}
+#endif
+			tailcall = 1;
+			goto restoreStateVariables;
+		    default:
+			Tcl_Panic("TEBC: TEOV_NR2 sent us a record we cannot handle!");
+		}
+	    }
+	}
+      restoreStateVariables:
 	NR_DATA_DIG();
 	esPtr = iPtr->execEnvPtr->execStackPtr;
 	tosPtr = esPtr->tosPtr;
@@ -7778,69 +7825,9 @@ TclExecuteByteCode(
 	CACHE_STACK_INFO();
 	goto nonRecursiveCallReturn;
     }
-
-    if (tailObjPtr && result == TCL_OK) {
-	/*
-	 * The best we can do here is to add the tailcall at the FRONT of the
-	 * callback list. This will be a real tailcall if we're lucky to have
-	 * been called from TEOV (or similar), and not-quite-but-almost if
-	 * called from eg TclOO (I think).
-	 * The simplest way to add to the front is:
-	 *  (a) push a new record
-	 *  (b) add the tailcall as callback to the newly-created 2nd record
-	 *  (c) swap the two top records: old top is still top, newly created
-	 *      record is second
-	 */
-
-	TEOV_record *rootPtr, *recordPtr;
-
-	rootPtr = TOP_RECORD(iPtr);
-	PUSH_RECORD(iPtr, recordPtr);
-	TclNRAddCallback(interp, TailcallFromTebc, tailObjPtr, lookupNsPtr, NULL, NULL);
-
-	/* Now swap them! */
-	recordPtr->nextPtr = rootPtr->nextPtr;
-	rootPtr->nextPtr = recordPtr;
-	TOP_RECORD(iPtr) = rootPtr;
-    }
 #endif
     return result;
 }
-
-static int
-TailcallFromTebc(
-    ClientData data[],
-    Tcl_Interp *interp,
-    int result)
-{
-    Tcl_Obj *tailObjPtr = data[0];
-    Namespace *lookupNsPtr = data[1];
-    int objc;
-    Tcl_Obj **objv;
-
-    Tcl_IncrRefCount(tailObjPtr); /* unshared per construction! */
-    if (result != TCL_OK) {
-	goto done;
-    }
-    result = Tcl_ListObjGetElements(NULL, tailObjPtr, &objc, &objv);
-    if (result != TCL_OK) {
-	/* shouldn't happen */
-	goto done;
-    }
-	
-    /*
-     * Note that by this time the proc's frame SHOULD BE ALREADY POPPED! We do
-     * as if it was (don't know what happens with eg TclOO), ie, assume that
-     * are already in [uplevel 1] from the proc's callFrame..
-     */
-
-    iPtr->lookupNsPtr = lookupNsPtr;
-    result = Tcl_EvalObjv(interp, objc, objv, TCL_EVAL_INVOKE);
-
-    done:
-    Tcl_DecrRefCount(tailObjPtr);
-    return result;
-}
 #undef iPtr
 
 #ifdef TCL_COMPILE_DEBUG
diff --git a/generic/tclInt.h b/generic/tclInt.h
index 202f5b8..93fa71b 100644
--- a/generic/tclInt.h
+++ b/generic/tclInt.h
@@ -14,7 +14,7 @@
  * See the file "license.terms" for information on usage and redistribution of
  * this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tclInt.h,v 1.373 2008/07/13 16:07:19 msofer Exp $
+ * RCS: @(#) $Id: tclInt.h,v 1.374 2008/07/21 03:43:31 msofer Exp $
  */
 
 #ifndef _TCLINT
@@ -1319,9 +1319,6 @@ typedef struct ExecEnv {
     int tebcCall;                   /* used to distinguish tebc calls from
 				     * other calls to TEOV, and other comms
 				     * between TEBC and TEOV */
-    ClientData tebcData;            /* used by TEOV to pass data to its
-				     * calling TEBC */
-    
 } ExecEnv;
 
 /*
diff --git a/generic/tclNRE.h b/generic/tclNRE.h
index 08ddcd5..4d44ab2 100644
--- a/generic/tclNRE.h
+++ b/generic/tclNRE.h
@@ -11,7 +11,7 @@
  * this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
  * // FIXME: RCS numbering?
- * RCS: @(#) $Id: tclNRE.h,v 1.4 2008/07/18 23:29:44 msofer Exp $
+ * RCS: @(#) $Id: tclNRE.h,v 1.5 2008/07/21 03:43:32 msofer Exp $
  */
 
 
@@ -102,7 +102,7 @@ typedef struct TEOV_record {
     TEOV_callback *callbackPtr;
     struct TEOV_record *nextPtr;
     union {
-	struct ByteCode *codePtr;
+	struct ByteCode *codePtr;       /* TCL_NR_BC_TYPE       */
 	struct {
 	    Tcl_Obj *objPtr;
 	    int flags;
@@ -111,10 +111,6 @@ typedef struct TEOV_record {
 	    Tcl_ObjCmdProc *objProc;
 	    ClientData clientData;
 	} objProc;
-	struct {
-	    int objc;
-	    Tcl_Obj *const *objv;
-	} objv;
     } data;
 #if !USE_SMALL_ALLOC
     /* Extra checks: can disappear later */
@@ -165,12 +161,6 @@ typedef struct TEOV_record {
 #define TEBC_CALL(iPtr)				\
     (((Interp *)iPtr)->execEnvPtr->tebcCall)
 
-#define TEBC_DATA(iPtr)				\
-    (((Interp *)iPtr)->execEnvPtr->tebcData)
-
-#define TEBC_DO_EXEC             1  /* MUST NOT be 0 */
-#define TEBC_DO_TAILCALL         2
-
 #define TclNRAddCallback(\
     interp,\
     postProcPtr,\
diff --git a/generic/tclProc.c b/generic/tclProc.c
index 187c789..713ee18 100644
--- a/generic/tclProc.c
+++ b/generic/tclProc.c
@@ -12,7 +12,7 @@
  * See the file "license.terms" for information on usage and redistribution of
  * this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tclProc.c,v 1.149 2008/07/19 22:50:41 nijtmans Exp $
+ * RCS: @(#) $Id: tclProc.c,v 1.150 2008/07/21 03:43:32 msofer Exp $
  */
 
 #include "tclInt.h"
@@ -1737,6 +1737,10 @@ TclObjInterpProcCore(
     if (result == TCL_OK) {
     	result = TclExecuteByteCode(interp, record.data.codePtr);
 	result = TclEvalObjv_NR2(interp, result, rootPtr);
+	if (TOP_RECORD(iPtr) != rootPtr) {
+	    /* FIXME NRE & tailcalls */
+	    Tcl_Panic("TclObjInterpProcCore not yet prepared to deal with evals in callbacks!");
+	}
 	result = InterpProcNR2(record.callbackPtr->data, interp, result);
 	TclSmallFree(record.callbackPtr);
     }