TraceVarInfo *tvarPtr = (TraceVarInfo *)clientData;
    char *result;
    int code, destroy = 0;
    Tcl_DString cmd;
    int rewind = ((Interp *)interp)->execEnvPtr->rewind;

    /*
     * We might call Tcl_EvalEx() below, and that might evaluate [trace vdelete]
     * which might try to free tvarPtr. We want to use tvarPtr until the end
     * of this function, so we use Tcl_Preserve() and Tcl_Release() to be sure
     * it is not freed while we still need it.
     * We might call Tcl_EvalEx() below, and that might evaluate
     * [trace remove variable] which might try to free tvarPtr. We want to
     * use tvarPtr until the end of this function, so we use Tcl_Preserve()
     * and Tcl_Release() to be sure it is not freed while we still need it.
     */

    result = NULL;
    if ((tvarPtr->flags & flags) && !Tcl_InterpDeleted(interp)
	    && !Tcl_LimitExceeded(interp)) {
	if (tvarPtr->length) {
	    /*