shared/tcl_base/tclvar.c

/* $Header: /cvsroot/esrg/sfesrg/esrgpcpj/shared/tcl_base/tclvar.c,v 1.1.1.1 2001/06/13 04:48:07 dtashley Exp $ */

/* 
 * tclVar.c --
 *
 *      This file contains routines that implement Tcl variables
 *      (both scalars and arrays).
 *
 *      The implementation of arrays is modelled after an initial
 *      implementation by Mark Diekhans and Karl Lehenbauer.
 *
 * Copyright (c) 1987-1994 The Regents of the University of California.
 * Copyright (c) 1994-1997 Sun Microsystems, Inc.
 * Copyright (c) 1998-1999 by Scriptics Corporation.
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclvar.c,v 1.1.1.1 2001/06/13 04:48:07 dtashley Exp $
 */

#include "tclInt.h"
#include "tclPort.h"

/*
 * The strings below are used to indicate what went wrong when a
 * variable access is denied.
 */

static char *noSuchVar =        "no such variable";
static char *isArray =          "variable is array";
static char *needArray =        "variable isn't array";
static char *noSuchElement =    "no such element in array";
static char *danglingElement =  "upvar refers to element in deleted array";
static char *danglingVar =     "upvar refers to variable in deleted namespace";
static char *badNamespace =     "parent namespace doesn't exist";
static char *missingName =      "missing variable name";
static char *isArrayElement =   "name refers to an element in an array";

/*
 * Forward references to procedures defined later in this file:
 */

static  char *          CallTraces _ANSI_ARGS_((Interp *iPtr, Var *arrayPtr,
                            Var *varPtr, char *part1, char *part2,
                            int flags));
static void             CleanupVar _ANSI_ARGS_((Var *varPtr,
                            Var *arrayPtr));
static void             DeleteSearches _ANSI_ARGS_((Var *arrayVarPtr));
static void             DeleteArray _ANSI_ARGS_((Interp *iPtr,
                            char *arrayName, Var *varPtr, int flags));
static int              MakeUpvar _ANSI_ARGS_((
                            Interp *iPtr, CallFrame *framePtr,
                            char *otherP1, char *otherP2, int otherFlags,
                            char *myName, int myFlags));
static Var *            NewVar _ANSI_ARGS_((void));
static ArraySearch *    ParseSearchId _ANSI_ARGS_((Tcl_Interp *interp,
                            Var *varPtr, char *varName, char *string));
static void             VarErrMsg _ANSI_ARGS_((Tcl_Interp *interp,
                            char *part1, char *part2, char *operation,
                            char *reason));

/*
 *----------------------------------------------------------------------
 *
 * TclLookupVar --
 *
 *      This procedure is used by virtually all of the variable code to
 *      locate a variable given its name(s).
 *
 * Results:
 *      The return value is a pointer to the variable structure indicated by
 *      part1 and part2, or NULL if the variable couldn't be found. If the
 *      variable is found, *arrayPtrPtr is filled in with the address of the
 *      variable structure for the array that contains the variable (or NULL
 *      if the variable is a scalar). If the variable can't be found and
 *      either createPart1 or createPart2 are 1, a new as-yet-undefined
 *      (VAR_UNDEFINED) variable structure is created, entered into a hash
 *      table, and returned.
 *
 *      If the variable isn't found and creation wasn't specified, or some
 *      other error occurs, NULL is returned and an error message is left in
 *      the interp's result if TCL_LEAVE_ERR_MSG is set in flags. 
 *
 *      Note: it's possible for the variable returned to be VAR_UNDEFINED
 *      even if createPart1 or createPart2 are 1 (these only cause the hash
 *      table entry or array to be created). For example, the variable might
 *      be a global that has been unset but is still referenced by a
 *      procedure, or a variable that has been unset but it only being kept
 *      in existence (if VAR_UNDEFINED) by a trace.
 *
 * Side effects:
 *      New hashtable entries may be created if createPart1 or createPart2
 *      are 1.
 *
 *----------------------------------------------------------------------
 */

Var *
TclLookupVar(interp, part1, part2, flags, msg, createPart1, createPart2,
        arrayPtrPtr)
    Tcl_Interp *interp;         /* Interpreter to use for lookup. */
    register char *part1;       /* If part2 isn't NULL, this is the name of
                                 * an array. Otherwise, this
                                 * is a full variable name that could
                                 * include a parenthesized array element. */
    char *part2;                /* Name of element within array, or NULL. */
    int flags;                  /* Only TCL_GLOBAL_ONLY, TCL_NAMESPACE_ONLY,
                                 * and TCL_LEAVE_ERR_MSG bits matter. */
    char *msg;                  /* Verb to use in error messages, e.g.
                                 * "read" or "set". Only needed if
                                 * TCL_LEAVE_ERR_MSG is set in flags. */
    int createPart1;            /* If 1, create hash table entry for part 1
                                 * of name, if it doesn't already exist. If
                                 * 0, return error if it doesn't exist. */
    int createPart2;            /* If 1, create hash table entry for part 2
                                 * of name, if it doesn't already exist. If
                                 * 0, return error if it doesn't exist. */
    Var **arrayPtrPtr;          /* If the name refers to an element of an
                                 * array, *arrayPtrPtr gets filled in with
                                 * address of array variable. Otherwise
                                 * this is set to NULL. */
{
    Interp *iPtr = (Interp *) interp;
    CallFrame *varFramePtr = iPtr->varFramePtr;
                                /* Points to the procedure call frame whose
                                 * variables are currently in use. Same as
                                 * the current procedure's frame, if any,
                                 * unless an "uplevel" is executing. */
    Tcl_HashTable *tablePtr;    /* Points to the hashtable, if any, in which
                                 * to look up the variable. */
    Tcl_Var var;                /* Used to search for global names. */
    Var *varPtr;                /* Points to the Var structure returned for
                                 * the variable. */
    char *elName;               /* Name of array element or NULL; may be
                                 * same as part2, or may be openParen+1. */
    char *openParen, *closeParen;
                                /* If this procedure parses a name into
                                 * array and index, these point to the
                                 * parens around the index.  Otherwise they
                                 * are NULL. These are needed to restore
                                 * the parens after parsing the name. */
    Namespace *varNsPtr, *cxtNsPtr, *dummy1Ptr, *dummy2Ptr;
    ResolverScheme *resPtr;
    Tcl_HashEntry *hPtr;
    register char *p;
    int new, i, result;

    varPtr = NULL;
    *arrayPtrPtr = NULL;
    openParen = closeParen = NULL;
    varNsPtr = NULL;            /* set non-NULL if a nonlocal variable */

    /*
     * Parse part1 into array name and index.
     * Always check if part1 is an array element name and allow it only if
     * part2 is not given.   
     * (if one does not care about creating array elements that can't be used
     *  from tcl, and prefer slightly better performance, one can put
     *  the following in an   if (part2 == NULL) { ... } block and remove
     *  the part2's test and error reporting  or move that code in array set)
     */

    elName = part2;
    for (p = part1; *p ; p++) {
        if (*p == '(') {
            openParen = p;
            do {
                p++;
            } while (*p != '\0');
            p--;
            if (*p == ')') {
                if (part2 != NULL) {
                    openParen = NULL;
                    if (flags & TCL_LEAVE_ERR_MSG) {
                        VarErrMsg(interp, part1, part2, msg, needArray);
                    }
                    goto done;
                }
                closeParen = p;
                *openParen = 0;
                elName = openParen+1;
            } else {
                openParen = NULL;
            }
            break;
        }
    }

    /*
     * If this namespace has a variable resolver, then give it first
     * crack at the variable resolution.  It may return a Tcl_Var
     * value, it may signal to continue onward, or it may signal
     * an error.
     */
    if ((flags & TCL_GLOBAL_ONLY) != 0 || iPtr->varFramePtr == NULL) {
        cxtNsPtr = iPtr->globalNsPtr;
    } else {
        cxtNsPtr = iPtr->varFramePtr->nsPtr;
    }

    if (cxtNsPtr->varResProc != NULL || iPtr->resolverPtr != NULL) {
        resPtr = iPtr->resolverPtr;

        if (cxtNsPtr->varResProc) {
            result = (*cxtNsPtr->varResProc)(interp, part1,
                    (Tcl_Namespace *) cxtNsPtr, flags, &var);
        } else {
            result = TCL_CONTINUE;
        }

        while (result == TCL_CONTINUE && resPtr) {
            if (resPtr->varResProc) {
                result = (*resPtr->varResProc)(interp, part1,
                        (Tcl_Namespace *) cxtNsPtr, flags, &var);
            }
            resPtr = resPtr->nextPtr;
        }

        if (result == TCL_OK) {
            varPtr = (Var *) var;
            goto lookupVarPart2;
        } else if (result != TCL_CONTINUE) {
            return (Var *) NULL;
        }
    }

    /*
     * Look up part1. Look it up as either a namespace variable or as a
     * local variable in a procedure call frame (varFramePtr).
     * Interpret part1 as a namespace variable if:
     *    1) so requested by a TCL_GLOBAL_ONLY or TCL_NAMESPACE_ONLY flag,
     *    2) there is no active frame (we're at the global :: scope),
     *    3) the active frame was pushed to define the namespace context
     *       for a "namespace eval" or "namespace inscope" command,
     *    4) the name has namespace qualifiers ("::"s).
     * Otherwise, if part1 is a local variable, search first in the
     * frame's array of compiler-allocated local variables, then in its
     * hashtable for runtime-created local variables.
     *
     * If createPart1 and the variable isn't found, create the variable and,
     * if necessary, create varFramePtr's local var hashtable.
     */

    if (((flags & (TCL_GLOBAL_ONLY | TCL_NAMESPACE_ONLY)) != 0)
            || (varFramePtr == NULL)
            || !varFramePtr->isProcCallFrame
            || (strstr(part1, "::") != NULL)) {
        char *tail;
        
        /*
         * Don't pass TCL_LEAVE_ERR_MSG, we may yet create the variable,
         * or otherwise generate our own error!
         */
        var = Tcl_FindNamespaceVar(interp, part1, (Tcl_Namespace *) NULL,
                flags & ~TCL_LEAVE_ERR_MSG);
        if (var != (Tcl_Var) NULL) {
            varPtr = (Var *) var;
        }
        if (varPtr == NULL) {
            if (createPart1) {   /* var wasn't found so create it  */
                TclGetNamespaceForQualName(interp, part1, (Namespace *) NULL,
                        flags, &varNsPtr, &dummy1Ptr, &dummy2Ptr, &tail);

                if (varNsPtr == NULL) {
                    if (flags & TCL_LEAVE_ERR_MSG) {
                        VarErrMsg(interp, part1, part2, msg, badNamespace);
                    }
                    goto done;
                }
                if (tail == NULL) {
                    if (flags & TCL_LEAVE_ERR_MSG) {
                        VarErrMsg(interp, part1, part2, msg, missingName);
                    }
                    goto done;
                }
                hPtr = Tcl_CreateHashEntry(&varNsPtr->varTable, tail, &new);
                varPtr = NewVar();
                Tcl_SetHashValue(hPtr, varPtr);
                varPtr->hPtr = hPtr;
                varPtr->nsPtr = varNsPtr;
            } else {            /* var wasn't found and not to create it */
                if (flags & TCL_LEAVE_ERR_MSG) {
                    VarErrMsg(interp, part1, part2, msg, noSuchVar);
                }
                goto done;
            }
        }
    } else {                    /* local var: look in frame varFramePtr */
        Proc *procPtr = varFramePtr->procPtr;
        int localCt = procPtr->numCompiledLocals;
        CompiledLocal *localPtr = procPtr->firstLocalPtr;
        Var *localVarPtr = varFramePtr->compiledLocals;
        int part1Len = strlen(part1);
        
        for (i = 0;  i < localCt;  i++) {
            if (!TclIsVarTemporary(localPtr)) {
                register char *localName = localVarPtr->name;
                if ((part1[0] == localName[0])
                        && (part1Len == localPtr->nameLength)
                        && (strcmp(part1, localName) == 0)) {
                    varPtr = localVarPtr;
                    break;
                }
            }
            localVarPtr++;
            localPtr = localPtr->nextPtr;
        }
        if (varPtr == NULL) {   /* look in the frame's var hash table */
            tablePtr = varFramePtr->varTablePtr;
            if (createPart1) {
                if (tablePtr == NULL) {
                    tablePtr = (Tcl_HashTable *)
                        ckalloc(sizeof(Tcl_HashTable));
                    Tcl_InitHashTable(tablePtr, TCL_STRING_KEYS);
                    varFramePtr->varTablePtr = tablePtr;
                }
                hPtr = Tcl_CreateHashEntry(tablePtr, part1, &new);
                if (new) {
                    varPtr = NewVar();
                    Tcl_SetHashValue(hPtr, varPtr);
                    varPtr->hPtr = hPtr;
                    varPtr->nsPtr = NULL; /* a local variable */
                } else {
                    varPtr = (Var *) Tcl_GetHashValue(hPtr);
                }
            } else {
                hPtr = NULL;
                if (tablePtr != NULL) {
                    hPtr = Tcl_FindHashEntry(tablePtr, part1);
                }
                if (hPtr == NULL) {
                    if (flags & TCL_LEAVE_ERR_MSG) {
                        VarErrMsg(interp, part1, part2, msg, noSuchVar);
                    }
                    goto done;
                }
                varPtr = (Var *) Tcl_GetHashValue(hPtr);
            }
        }
    }

    lookupVarPart2:
    if (openParen != NULL) {
        *openParen = '(';
        openParen = NULL;
    }

    /*
     * If varPtr is a link variable, we have a reference to some variable
     * that was created through an "upvar" or "global" command. Traverse
     * through any links until we find the referenced variable.
     */
        
    while (TclIsVarLink(varPtr)) {
        varPtr = varPtr->value.linkPtr;
    }

    /*
     * If we're not dealing with an array element, return varPtr.
     */
    
    if (elName == NULL) {
        goto done;
    }

    /*
     * We're dealing with an array element. Make sure the variable is an
     * array and look up the element (create the element if desired).
     */

    if (TclIsVarUndefined(varPtr) && !TclIsVarArrayElement(varPtr)) {
        if (!createPart1) {
            if (flags & TCL_LEAVE_ERR_MSG) {
                VarErrMsg(interp, part1, part2, msg, noSuchVar);
            }
            varPtr = NULL;
            goto done;
        }

        /*
         * Make sure we are not resurrecting a namespace variable from a
         * deleted namespace!
         */
        if ((varPtr->flags & VAR_IN_HASHTABLE) && (varPtr->hPtr == NULL)) {
            if (flags & TCL_LEAVE_ERR_MSG) {
                VarErrMsg(interp, part1, part2, msg, danglingVar);
            }
            varPtr = NULL;
            goto done;
        }

        TclSetVarArray(varPtr);
        TclClearVarUndefined(varPtr);
        varPtr->value.tablePtr =
            (Tcl_HashTable *) ckalloc(sizeof(Tcl_HashTable));
        Tcl_InitHashTable(varPtr->value.tablePtr, TCL_STRING_KEYS);
    } else if (!TclIsVarArray(varPtr)) {
        if (flags & TCL_LEAVE_ERR_MSG) {
            VarErrMsg(interp, part1, part2, msg, needArray);
        }
        varPtr = NULL;
        goto done;
    }
    *arrayPtrPtr = varPtr;
    if (closeParen != NULL) {
        *closeParen = 0;
    }
    if (createPart2) {
        hPtr = Tcl_CreateHashEntry(varPtr->value.tablePtr, elName, &new);
        if (closeParen != NULL) {
            *closeParen = ')';
        }
        if (new) {
            if (varPtr->searchPtr != NULL) {
                DeleteSearches(varPtr);
            }
            varPtr = NewVar();
            Tcl_SetHashValue(hPtr, varPtr);
            varPtr->hPtr = hPtr;
            varPtr->nsPtr = varNsPtr;
            TclSetVarArrayElement(varPtr);
        }
    } else {
        hPtr = Tcl_FindHashEntry(varPtr->value.tablePtr, elName);
        if (closeParen != NULL) {
            *closeParen = ')';
        }
        if (hPtr == NULL) {
            if (flags & TCL_LEAVE_ERR_MSG) {
                VarErrMsg(interp, part1, part2, msg, noSuchElement);
            }
            varPtr = NULL;
            goto done;
        }
    }
    varPtr = (Var *) Tcl_GetHashValue(hPtr);

    done:
    if (openParen != NULL) {
        *openParen = '(';
    }
    return varPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetVar --
 *
 *      Return the value of a Tcl variable as a string.
 *
 * Results:
 *      The return value points to the current value of varName as a string.
 *      If the variable is not defined or can't be read because of a clash
 *      in array usage then a NULL pointer is returned and an error message
 *      is left in the interp's result if the TCL_LEAVE_ERR_MSG flag is set.
 *      Note: the return value is only valid up until the next change to the
 *      variable; if you depend on the value lasting longer than that, then
 *      make yourself a private copy.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

char *
Tcl_GetVar(interp, varName, flags)
    Tcl_Interp *interp;         /* Command interpreter in which varName is
                                 * to be looked up. */
    char *varName;              /* Name of a variable in interp. */
    int flags;                  /* OR-ed combination of TCL_GLOBAL_ONLY,
                                 * TCL_NAMESPACE_ONLY or TCL_LEAVE_ERR_MSG
                                 * bits. */
{
    return Tcl_GetVar2(interp, varName, (char *) NULL, flags);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetVar2 --
 *
 *      Return the value of a Tcl variable as a string, given a two-part
 *      name consisting of array name and element within array.
 *
 * Results:
 *      The return value points to the current value of the variable given
 *      by part1 and part2 as a string. If the specified variable doesn't
 *      exist, or if there is a clash in array usage, then NULL is returned
 *      and a message will be left in the interp's result if the
 *      TCL_LEAVE_ERR_MSG flag is set. Note: the return value is only valid
 *      up until the next change to the variable; if you depend on the value
 *      lasting longer than that, then make yourself a private copy.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

char *
Tcl_GetVar2(interp, part1, part2, flags)
    Tcl_Interp *interp;         /* Command interpreter in which variable is
                                 * to be looked up. */
    char *part1;                /* Name of an array (if part2 is non-NULL)
                                 * or the name of a variable. */
    char *part2;                /* If non-NULL, gives the name of an element
                                 * in the array part1. */
    int flags;                  /* OR-ed combination of TCL_GLOBAL_ONLY,
                                 * TCL_NAMESPACE_ONLY and TCL_LEAVE_ERR_MSG
                                 * bits. */
{
    Tcl_Obj *objPtr;

    objPtr = Tcl_GetVar2Ex(interp, part1, part2, flags);
    if (objPtr == NULL) {
        return NULL;
    }
    return TclGetString(objPtr);
}
/*
 *----------------------------------------------------------------------
 *
 * Tcl_ObjGetVar2 --
 *
 *      Return the value of a Tcl variable as a Tcl object, given a
 *      two-part name consisting of array name and element within array.
 *
 * Results:
 *      The return value points to the current object value of the variable
 *      given by part1Ptr and part2Ptr. If the specified variable doesn't
 *      exist, or if there is a clash in array usage, then NULL is returned
 *      and a message will be left in the interpreter's result if the
 *      TCL_LEAVE_ERR_MSG flag is set.
 *
 * Side effects:
 *      The ref count for the returned object is _not_ incremented to
 *      reflect the returned reference; if you want to keep a reference to
 *      the object you must increment its ref count yourself.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
Tcl_ObjGetVar2(interp, part1Ptr, part2Ptr, flags)
    Tcl_Interp *interp;         /* Command interpreter in which variable is
                                 * to be looked up. */
    register Tcl_Obj *part1Ptr; /* Points to an object holding the name of
                                 * an array (if part2 is non-NULL) or the
                                 * name of a variable. */
    register Tcl_Obj *part2Ptr; /* If non-null, points to an object holding
                                 * the name of an element in the array
                                 * part1Ptr. */
    int flags;                  /* OR-ed combination of TCL_GLOBAL_ONLY,
                                 * TCL_LEAVE_ERR_MSG, and
                                 * TCL_PARSE_PART1 bits. */
{
    char *part1, *part2;

    part1 = Tcl_GetString(part1Ptr);
    if (part2Ptr != NULL) {
        part2 = Tcl_GetString(part2Ptr);
    } else {
        part2 = NULL;
    }
    
    return Tcl_GetVar2Ex(interp, part1, part2, flags);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetVar2Ex --
 *
 *      Return the value of a Tcl variable as a Tcl object, given a
 *      two-part name consisting of array name and element within array.
 *
 * Results:
 *      The return value points to the current object value of the variable
 *      given by part1Ptr and part2Ptr. If the specified variable doesn't
 *      exist, or if there is a clash in array usage, then NULL is returned
 *      and a message will be left in the interpreter's result if the
 *      TCL_LEAVE_ERR_MSG flag is set.
 *
 * Side effects:
 *      The ref count for the returned object is _not_ incremented to
 *      reflect the returned reference; if you want to keep a reference to
 *      the object you must increment its ref count yourself.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
Tcl_GetVar2Ex(interp, part1, part2, flags)
    Tcl_Interp *interp;         /* Command interpreter in which variable is
                                 * to be looked up. */
    char *part1;                /* Name of an array (if part2 is non-NULL)
                                 * or the name of a variable. */
    char *part2;                /* If non-NULL, gives the name of an element
                                 * in the array part1. */
    int flags;                  /* OR-ed combination of TCL_GLOBAL_ONLY,
                                 * and TCL_LEAVE_ERR_MSG bits. */
{
    Interp *iPtr = (Interp *) interp;
    register Var *varPtr;
    Var *arrayPtr;
    char *msg;

    varPtr = TclLookupVar(interp, part1, part2, flags, "read",
            /*createPart1*/ 0, /*createPart2*/ 1, &arrayPtr);
    if (varPtr == NULL) {
        return NULL;
    }

    /*
     * Invoke any traces that have been set for the variable.
     */

    if ((varPtr->tracePtr != NULL)
            || ((arrayPtr != NULL) && (arrayPtr->tracePtr != NULL))) {
        msg = CallTraces(iPtr, arrayPtr, varPtr, part1, part2,
                (flags & (TCL_NAMESPACE_ONLY|TCL_GLOBAL_ONLY)) | TCL_TRACE_READS);
        if (msg != NULL) {
            if (flags & TCL_LEAVE_ERR_MSG) {
                VarErrMsg(interp, part1, part2, "read", msg);
            }
            goto errorReturn;
        }
    }

    /*
     * Return the element if it's an existing scalar variable.
     */
    
    if (TclIsVarScalar(varPtr) && !TclIsVarUndefined(varPtr)) {
        return varPtr->value.objPtr;
    }
    
    if (flags & TCL_LEAVE_ERR_MSG) {
        if (TclIsVarUndefined(varPtr) && (arrayPtr != NULL)
                && !TclIsVarUndefined(arrayPtr)) {
            msg = noSuchElement;
        } else if (TclIsVarArray(varPtr)) {
            msg = isArray;
        } else {
            msg = noSuchVar;
        }
        VarErrMsg(interp, part1, part2, "read", msg);
    }

    /*
     * An error. If the variable doesn't exist anymore and no-one's using
     * it, then free up the relevant structures and hash table entries.
     */

    errorReturn:
    if (TclIsVarUndefined(varPtr)) {
        CleanupVar(varPtr, arrayPtr);
    }
    return NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * TclGetIndexedScalar --
 *
 *      Return the Tcl object value of a local scalar variable in the active
 *      procedure, given its index in the procedure's array of compiler
 *      allocated local variables.
 *
 * Results:
 *      The return value points to the current object value of the variable
 *      given by localIndex. If the specified variable doesn't exist, or
 *      there is a clash in array usage, or an error occurs while executing
 *      variable traces, then NULL is returned and a message will be left in
 *      the interpreter's result if leaveErrorMsg is 1.
 *
 * Side effects:
 *      The ref count for the returned object is _not_ incremented to
 *      reflect the returned reference; if you want to keep a reference to
 *      the object you must increment its ref count yourself.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
TclGetIndexedScalar(interp, localIndex, leaveErrorMsg)
    Tcl_Interp *interp;         /* Command interpreter in which variable is
                                 * to be looked up. */
    register int localIndex;    /* Index of variable in procedure's array
                                 * of local variables. */
    int leaveErrorMsg;          /* 1 if to leave an error message in
                                 * interpreter's result on an error.
                                 * Otherwise no error message is left. */
{
    Interp *iPtr = (Interp *) interp;
    CallFrame *varFramePtr = iPtr->varFramePtr;
                                /* Points to the procedure call frame whose
                                 * variables are currently in use. Same as
                                 * the current procedure's frame, if any,
                                 * unless an "uplevel" is executing. */
    Var *compiledLocals = varFramePtr->compiledLocals;
    register Var *varPtr;       /* Points to the variable's in-frame Var
                                 * structure. */
    char *varName;              /* Name of the local variable. */
    char *msg;

#ifdef TCL_COMPILE_DEBUG
    int localCt = varFramePtr->procPtr->numCompiledLocals;

    if (compiledLocals == NULL) {
        fprintf(stderr, "\nTclGetIndexedScalar: can't get local %i in frame 0x%x, no compiled locals\n",
                localIndex, (unsigned int) varFramePtr);
        panic("TclGetIndexedScalar: no compiled locals in frame 0x%x",
                (unsigned int) varFramePtr);
    }
    if ((localIndex < 0) || (localIndex >= localCt)) {
        fprintf(stderr, "\nTclGetIndexedScalar: can't get local %i in frame 0x%x with %i locals\n",
                localIndex, (unsigned int) varFramePtr, localCt);
        panic("TclGetIndexedScalar: bad local index %i in frame 0x%x",
                localIndex, (unsigned int) varFramePtr);
    }
#endif /* TCL_COMPILE_DEBUG */
    
    varPtr = &(compiledLocals[localIndex]);
    varName = varPtr->name;

    /*
     * If varPtr is a link variable, we have a reference to some variable
     * that was created through an "upvar" or "global" command, or we have a
     * reference to a variable in an enclosing namespace. Traverse through
     * any links until we find the referenced variable.
     */
        
    while (TclIsVarLink(varPtr)) {
        varPtr = varPtr->value.linkPtr;
    }

    /*
     * Invoke any traces that have been set for the variable.
     */

    if (varPtr->tracePtr != NULL) {
        msg = CallTraces(iPtr, /*arrayPtr*/ NULL, varPtr, varName, NULL,
                TCL_TRACE_READS);
        if (msg != NULL) {
            if (leaveErrorMsg) {
                VarErrMsg(interp, varName, NULL, "read", msg);
            }
            return NULL;
        }
    }

    /*
     * Make sure we're dealing with a scalar variable and not an array, and
     * that the variable exists (isn't undefined).
     */

    if (!TclIsVarScalar(varPtr) || TclIsVarUndefined(varPtr)) {
        if (leaveErrorMsg) {
            if (TclIsVarArray(varPtr)) {
                msg = isArray;
            } else {
                msg = noSuchVar;
            }
            VarErrMsg(interp, varName, NULL, "read", msg);

        }
        return NULL;
    }
    return varPtr->value.objPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * TclGetElementOfIndexedArray --
 *
 *      Return the Tcl object value for an element in a local array
 *      variable. The element is named by the object elemPtr while the 
 *      array is specified by its index in the active procedure's array
 *      of compiler allocated local variables.
 *
 * Results:
 *      The return value points to the current object value of the
 *      element. If the specified array or element doesn't exist, or there
 *      is a clash in array usage, or an error occurs while executing
 *      variable traces, then NULL is returned and a message will be left in
 *      the interpreter's result if leaveErrorMsg is 1.
 *
 * Side effects:
 *      The ref count for the returned object is _not_ incremented to
 *      reflect the returned reference; if you want to keep a reference to
 *      the object you must increment its ref count yourself.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
TclGetElementOfIndexedArray(interp, localIndex, elemPtr, leaveErrorMsg)
    Tcl_Interp *interp;         /* Command interpreter in which variable is
                                 * to be looked up. */
    int localIndex;             /* Index of array variable in procedure's
                                 * array of local variables. */
    Tcl_Obj *elemPtr;           /* Points to an object holding the name of
                                 * an element to get in the array. */
    int leaveErrorMsg;          /* 1 if to leave an error message in
                                 * the interpreter's result on an error.
                                 * Otherwise no error message is left. */
{
    Interp *iPtr = (Interp *) interp;
    CallFrame *varFramePtr = iPtr->varFramePtr;
                                /* Points to the procedure call frame whose
                                 * variables are currently in use. Same as
                                 * the current procedure's frame, if any,
                                 * unless an "uplevel" is executing. */
    Var *compiledLocals = varFramePtr->compiledLocals;
    Var *arrayPtr;              /* Points to the array's in-frame Var
                                 * structure. */
    char *arrayName;            /* Name of the local array. */
    Tcl_HashEntry *hPtr;
    Var *varPtr = NULL;         /* Points to the element's Var structure
                                 * that we return. Initialized to avoid
                                 * compiler warning. */
    char *elem, *msg;
    int new;

#ifdef TCL_COMPILE_DEBUG
    Proc *procPtr = varFramePtr->procPtr;
    int localCt = procPtr->numCompiledLocals;

    if (compiledLocals == NULL) {
        fprintf(stderr, "\nTclGetElementOfIndexedArray: can't get element of local %i in frame 0x%x, no compiled locals\n",
                localIndex, (unsigned int) varFramePtr);
        panic("TclGetIndexedScalar: no compiled locals in frame 0x%x",
                (unsigned int) varFramePtr);
    }
    if ((localIndex < 0) || (localIndex >= localCt)) {
        fprintf(stderr, "\nTclGetIndexedScalar: can't get element of local %i in frame 0x%x with %i locals\n",
                localIndex, (unsigned int) varFramePtr, localCt);
        panic("TclGetElementOfIndexedArray: bad local index %i in frame 0x%x",
                localIndex, (unsigned int) varFramePtr);
    }
#endif /* TCL_COMPILE_DEBUG */

    elem = TclGetString(elemPtr);
    arrayPtr = &(compiledLocals[localIndex]);
    arrayName = arrayPtr->name;

    /*
     * If arrayPtr is a link variable, we have a reference to some variable
     * that was created through an "upvar" or "global" command, or we have a
     * reference to a variable in an enclosing namespace. Traverse through
     * any links until we find the referenced variable.
     */
        
    while (TclIsVarLink(arrayPtr)) {
        arrayPtr = arrayPtr->value.linkPtr;
    }

    /*
     * Make sure we're dealing with an array and that the array variable
     * exists (isn't undefined).
     */

    if (!TclIsVarArray(arrayPtr) || TclIsVarUndefined(arrayPtr)) {
        if (leaveErrorMsg) {
            VarErrMsg(interp, arrayName, elem, "read", noSuchVar);
        }
        goto errorReturn;
    } 

    /*
     * Look up the element. Note that we must create the element (but leave
     * it marked undefined) if it does not already exist. This allows a
     * trace to create new array elements "on the fly" that did not exist
     * before. A trace is always passed a variable for the array element. If
     * the trace does not define the variable, it will be deleted below (at
     * errorReturn) and an error returned.
     */

    hPtr = Tcl_CreateHashEntry(arrayPtr->value.tablePtr, elem, &new);
    if (new) {
        if (arrayPtr->searchPtr != NULL) {
            DeleteSearches(arrayPtr);
        }
        varPtr = NewVar();
        Tcl_SetHashValue(hPtr, varPtr);
        varPtr->hPtr = hPtr;
        varPtr->nsPtr = varFramePtr->nsPtr;
        TclSetVarArrayElement(varPtr);
    } else {
        varPtr = (Var *) Tcl_GetHashValue(hPtr);
    }

    /*
     * Invoke any traces that have been set for the element variable.
     */

    if ((varPtr->tracePtr != NULL)
            || ((arrayPtr != NULL) && (arrayPtr->tracePtr != NULL))) {
        msg = CallTraces(iPtr, arrayPtr, varPtr, arrayName, elem,
                TCL_TRACE_READS);
        if (msg != NULL) {
            if (leaveErrorMsg) {
                VarErrMsg(interp, arrayName, elem, "read", msg);
            }
            goto errorReturn;
        }
    }

    /*
     * Return the element if it's an existing scalar variable.
     */
    
    if (TclIsVarScalar(varPtr) && !TclIsVarUndefined(varPtr)) {
        return varPtr->value.objPtr;
    }
    
    if (leaveErrorMsg) {
        if (TclIsVarArray(varPtr)) {
            msg = isArray;
        } else {
            msg = noSuchVar;
        }
        VarErrMsg(interp, arrayName, elem, "read", msg);
    }

    /*
     * An error. If the variable doesn't exist anymore and no-one's using
     * it, then free up the relevant structures and hash table entries.
     */

    errorReturn:
    if ((varPtr != NULL) && TclIsVarUndefined(varPtr)) {
        CleanupVar(varPtr, NULL); /* the array is not in a hashtable */
    }
    return NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_SetObjCmd --
 *
 *      This procedure is invoked to process the "set" Tcl command.
 *      See the user documentation for details on what it does.
 *
 * Results:
 *      A standard Tcl result value.
 *
 * Side effects:
 *      A variable's value may be changed.
 *
 *----------------------------------------------------------------------
 */

        /* ARGSUSED */
int
Tcl_SetObjCmd(dummy, interp, objc, objv)
    ClientData dummy;                   /* Not used. */
    register Tcl_Interp *interp;        /* Current interpreter. */
    int objc;                           /* Number of arguments. */
    Tcl_Obj *CONST objv[];              /* Argument objects. */
{
    Tcl_Obj *varValueObj;

    if (objc == 2) {
        varValueObj = Tcl_ObjGetVar2(interp, objv[1], NULL, TCL_LEAVE_ERR_MSG);
        if (varValueObj == NULL) {
            return TCL_ERROR;
        }
        Tcl_SetObjResult(interp, varValueObj);
        return TCL_OK;
    } else if (objc == 3) {

        varValueObj = Tcl_ObjSetVar2(interp, objv[1], NULL, objv[2],
                TCL_LEAVE_ERR_MSG);
        if (varValueObj == NULL) {
            return TCL_ERROR;
        }
        Tcl_SetObjResult(interp, varValueObj);
        return TCL_OK;
    } else {
        Tcl_WrongNumArgs(interp, 1, objv, "varName ?newValue?");
        return TCL_ERROR;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_SetVar --
 *
 *      Change the value of a variable.
 *
 * Results:
 *      Returns a pointer to the malloc'ed string which is the character
 *      representation of the variable's new value. The caller must not
 *      modify this string. If the write operation was disallowed then NULL
 *      is returned; if the TCL_LEAVE_ERR_MSG flag is set, then an
 *      explanatory message will be left in the interp's result. Note that the
 *      returned string may not be the same as newValue; this is because
 *      variable traces may modify the variable's value.
 *
 * Side effects:
 *      If varName is defined as a local or global variable in interp,
 *      its value is changed to newValue. If varName isn't currently
 *      defined, then a new global variable by that name is created.
 *
 *----------------------------------------------------------------------
 */

char *
Tcl_SetVar(interp, varName, newValue, flags)
    Tcl_Interp *interp;         /* Command interpreter in which varName is
                                 * to be looked up. */
    char *varName;              /* Name of a variable in interp. */
    char *newValue;             /* New value for varName. */
    int flags;                  /* Various flags that tell how to set value:
                                 * any of TCL_GLOBAL_ONLY,
                                 * TCL_NAMESPACE_ONLY, TCL_APPEND_VALUE,
                                 * TCL_LIST_ELEMENT, TCL_LEAVE_ERR_MSG. */
{
    return Tcl_SetVar2(interp, varName, (char *) NULL, newValue, flags);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_SetVar2 --
 *
 *      Given a two-part variable name, which may refer either to a
 *      scalar variable or an element of an array, change the value
 *      of the variable.  If the named scalar or array or element
 *      doesn't exist then create one.
 *
 * Results:
 *      Returns a pointer to the malloc'ed string which is the character
 *      representation of the variable's new value. The caller must not
 *      modify this string. If the write operation was disallowed because an
 *      array was expected but not found (or vice versa), then NULL is
 *      returned; if the TCL_LEAVE_ERR_MSG flag is set, then an explanatory
 *      message will be left in the interp's result. Note that the returned
 *      string may not be the same as newValue; this is because variable
 *      traces may modify the variable's value.
 *
 * Side effects:
 *      The value of the given variable is set. If either the array
 *      or the entry didn't exist then a new one is created.
 *
 *----------------------------------------------------------------------
 */

char *
Tcl_SetVar2(interp, part1, part2, newValue, flags)
    Tcl_Interp *interp;         /* Command interpreter in which variable is
                                 * to be looked up. */
    char *part1;                /* If part2 is NULL, this is name of scalar
                                 * variable. Otherwise it is the name of
                                 * an array. */
    char *part2;                /* Name of an element within an array, or
                                 * NULL. */
    char *newValue;             /* New value for variable. */
    int flags;                  /* Various flags that tell how to set value:
                                 * any of TCL_GLOBAL_ONLY,
                                 * TCL_NAMESPACE_ONLY, TCL_APPEND_VALUE,
                                 * TCL_LIST_ELEMENT, or TCL_LEAVE_ERR_MSG */
{
    register Tcl_Obj *valuePtr;
    Tcl_Obj *varValuePtr;

    /*
     * Create an object holding the variable's new value and use
     * Tcl_SetVar2Ex to actually set the variable.
     */

    valuePtr = Tcl_NewStringObj(newValue, -1);
    Tcl_IncrRefCount(valuePtr);

    varValuePtr = Tcl_SetVar2Ex(interp, part1, part2, valuePtr, flags);
    Tcl_DecrRefCount(valuePtr); /* done with the object */
    
    if (varValuePtr == NULL) {
        return NULL;
    }
    return TclGetString(varValuePtr);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ObjSetVar2 --
 *
 *      This function is the same as Tcl_SetVar2Ex below, except the
 *      variable names are passed in Tcl object instead of strings.
 *
 * Results:
 *      Returns a pointer to the Tcl_Obj holding the new value of the
 *      variable. If the write operation was disallowed because an array was
 *      expected but not found (or vice versa), then NULL is returned; if
 *      the TCL_LEAVE_ERR_MSG flag is set, then an explanatory message will
 *      be left in the interpreter's result. Note that the returned object
 *      may not be the same one referenced by newValuePtr; this is because
 *      variable traces may modify the variable's value.
 *
 * Side effects:
 *      The value of the given variable is set. If either the array or the
 *      entry didn't exist then a new variable is created.

 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
Tcl_ObjSetVar2(interp, part1Ptr, part2Ptr, newValuePtr, flags)
    Tcl_Interp *interp;         /* Command interpreter in which variable is
                                 * to be found. */
    register Tcl_Obj *part1Ptr; /* Points to an object holding the name of
                                 * an array (if part2 is non-NULL) or the
                                 * name of a variable. */
    register Tcl_Obj *part2Ptr; /* If non-null, points to an object holding
                                 * the name of an element in the array
                                 * part1Ptr. */
    Tcl_Obj *newValuePtr;       /* New value for variable. */
    int flags;                  /* Various flags that tell how to set value:
                                 * any of TCL_GLOBAL_ONLY,
                                 * TCL_NAMESPACE_ONLY, TCL_APPEND_VALUE,
                                 * TCL_LIST_ELEMENT, TCL_LEAVE_ERR_MSG, or
                                 * TCL_PARSE_PART1. */
{
    char *part1, *part2;

    part1 = Tcl_GetString(part1Ptr);
    if (part2Ptr != NULL) {
        part2 = Tcl_GetString(part2Ptr);
    } else {
        part2 = NULL;
    }
    
    return Tcl_SetVar2Ex(interp, part1, part2, newValuePtr, flags);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_SetVar2Ex --
 *
 *      Given a two-part variable name, which may refer either to a scalar
 *      variable or an element of an array, change the value of the variable
 *      to a new Tcl object value. If the named scalar or array or element
 *      doesn't exist then create one.
 *
 * Results:
 *      Returns a pointer to the Tcl_Obj holding the new value of the
 *      variable. If the write operation was disallowed because an array was
 *      expected but not found (or vice versa), then NULL is returned; if
 *      the TCL_LEAVE_ERR_MSG flag is set, then an explanatory message will
 *      be left in the interpreter's result. Note that the returned object
 *      may not be the same one referenced by newValuePtr; this is because
 *      variable traces may modify the variable's value.
 *
 * Side effects:
 *      The value of the given variable is set. If either the array or the
 *      entry didn't exist then a new variable is created.
 *
 *      The reference count is decremented for any old value of the variable
 *      and incremented for its new value. If the new value for the variable
 *      is not the same one referenced by newValuePtr (perhaps as a result
 *      of a variable trace), then newValuePtr's ref count is left unchanged
 *      by Tcl_SetVar2Ex. newValuePtr's ref count is also left unchanged if
 *      we are appending it as a string value: that is, if "flags" includes
 *      TCL_APPEND_VALUE but not TCL_LIST_ELEMENT.
 *
 *      The reference count for the returned object is _not_ incremented: if
 *      you want to keep a reference to the object you must increment its
 *      ref count yourself.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
Tcl_SetVar2Ex(interp, part1, part2, newValuePtr, flags)
    Tcl_Interp *interp;         /* Command interpreter in which variable is
                                 * to be found. */
    char *part1;                /* Name of an array (if part2 is non-NULL)
                                 * or the name of a variable. */
    char *part2;                /* If non-NULL, gives the name of an element
                                 * in the array part1. */
    Tcl_Obj *newValuePtr;       /* New value for variable. */
    int flags;                  /* Various flags that tell how to set value:
                                 * any of TCL_GLOBAL_ONLY,
                                 * TCL_NAMESPACE_ONLY, TCL_APPEND_VALUE,
                                 * TCL_LIST_ELEMENT or TCL_LEAVE_ERR_MSG. */
{
    Interp *iPtr = (Interp *) interp;
    register Var *varPtr;
    Var *arrayPtr;
    Tcl_Obj *oldValuePtr;
    Tcl_Obj *resultPtr = NULL;
    char *bytes;
    int length, result;

    varPtr = TclLookupVar(interp, part1, part2, flags, "set",
            /*createPart1*/ 1, /*createPart2*/ 1, &arrayPtr);
    if (varPtr == NULL) {
        return NULL;
    }

    /*
     * If the variable is in a hashtable and its hPtr field is NULL, then we
     * may have an upvar to an array element where the array was deleted
     * or an upvar to a namespace variable whose namespace was deleted.
     * Generate an error (allowing the variable to be reset would screw up
     * our storage allocation and is meaningless anyway).
     */

    if ((varPtr->flags & VAR_IN_HASHTABLE) && (varPtr->hPtr == NULL)) {
        if (flags & TCL_LEAVE_ERR_MSG) {
            if (TclIsVarArrayElement(varPtr)) {
                VarErrMsg(interp, part1, part2, "set", danglingElement);
            } else {
                VarErrMsg(interp, part1, part2, "set", danglingVar);
            }
        }
        return NULL;
    }

    /*
     * It's an error to try to set an array variable itself.
     */

    if (TclIsVarArray(varPtr) && !TclIsVarUndefined(varPtr)) {
        if (flags & TCL_LEAVE_ERR_MSG) {
            VarErrMsg(interp, part1, part2, "set", isArray);
        }
        return NULL;
    }

    /*
     * At this point, if we were appending, we used to call read traces: we
     * treated append as a read-modify-write. However, it seemed unlikely to
     * us that a real program would be interested in such reads being done
     * during a set operation.
     */

    /*
     * Set the variable's new value. If appending, append the new value to
     * the variable, either as a list element or as a string. Also, if
     * appending, then if the variable's old value is unshared we can modify
     * it directly, otherwise we must create a new copy to modify: this is
     * "copy on write".
     */

    oldValuePtr = varPtr->value.objPtr;
    if (flags & TCL_APPEND_VALUE) {
        if (TclIsVarUndefined(varPtr) && (oldValuePtr != NULL)) {
            Tcl_DecrRefCount(oldValuePtr);     /* discard old value */
            varPtr->value.objPtr = NULL;
            oldValuePtr = NULL;
        }
        if (flags & TCL_LIST_ELEMENT) {        /* append list element */
            if (oldValuePtr == NULL) {
                TclNewObj(oldValuePtr);
                varPtr->value.objPtr = oldValuePtr;
                Tcl_IncrRefCount(oldValuePtr); /* since var is referenced */
            } else if (Tcl_IsShared(oldValuePtr)) {
                varPtr->value.objPtr = Tcl_DuplicateObj(oldValuePtr);
                Tcl_DecrRefCount(oldValuePtr);
                oldValuePtr = varPtr->value.objPtr;
                Tcl_IncrRefCount(oldValuePtr); /* since var is referenced */
            }
            result = Tcl_ListObjAppendElement(interp, oldValuePtr,
                    newValuePtr);
            if (result != TCL_OK) {
                return NULL;
            }
        } else {                               /* append string */
            /*
             * We append newValuePtr's bytes but don't change its ref count.
             */

            bytes = Tcl_GetStringFromObj(newValuePtr, &length);
            if (oldValuePtr == NULL) {
                varPtr->value.objPtr = Tcl_NewStringObj(bytes, length);
                Tcl_IncrRefCount(varPtr->value.objPtr);
            } else {
                if (Tcl_IsShared(oldValuePtr)) {   /* append to copy */
                    varPtr->value.objPtr = Tcl_DuplicateObj(oldValuePtr);
                    TclDecrRefCount(oldValuePtr);
                    oldValuePtr = varPtr->value.objPtr;
                    Tcl_IncrRefCount(oldValuePtr); /* since var is ref */
                }
                Tcl_AppendObjToObj(oldValuePtr, newValuePtr);
            }
        }
    } else {
        if (flags & TCL_LIST_ELEMENT) {        /* set var to list element */
            int neededBytes, listFlags;

            /*
             * We set the variable to the result of converting newValuePtr's
             * string rep to a list element. We do not change newValuePtr's
             * ref count.
             */

            if (oldValuePtr != NULL) {
                Tcl_DecrRefCount(oldValuePtr); /* discard old value */
            }
            bytes = Tcl_GetStringFromObj(newValuePtr, &length);
            neededBytes = Tcl_ScanElement(bytes, &listFlags);
            oldValuePtr = Tcl_NewObj();
            oldValuePtr->bytes = (char *)
                ckalloc((unsigned) (neededBytes + 1));
            oldValuePtr->length = Tcl_ConvertElement(bytes,
                    oldValuePtr->bytes, listFlags);
            varPtr->value.objPtr = oldValuePtr;
            Tcl_IncrRefCount(varPtr->value.objPtr);
        } else if (newValuePtr != oldValuePtr) {
            varPtr->value.objPtr = newValuePtr;
            Tcl_IncrRefCount(newValuePtr);      /* var is another ref */
            if (oldValuePtr != NULL) {
                TclDecrRefCount(oldValuePtr);   /* discard old value */
            }
        }
    }
    TclSetVarScalar(varPtr);
    TclClearVarUndefined(varPtr);
    if (arrayPtr != NULL) {
        TclClearVarUndefined(arrayPtr);
    }

    /*
     * Invoke any write traces for the variable.
     */

    if ((varPtr->tracePtr != NULL)
            || ((arrayPtr != NULL) && (arrayPtr->tracePtr != NULL))) {
        char *msg = CallTraces(iPtr, arrayPtr, varPtr, part1, part2,
                (flags & (TCL_GLOBAL_ONLY|TCL_NAMESPACE_ONLY)) | TCL_TRACE_WRITES);
        if (msg != NULL) {
            if (flags & TCL_LEAVE_ERR_MSG) {
                VarErrMsg(interp, part1, part2, "set", msg);
            }
            goto cleanup;
        }
    }

    /*
     * Return the variable's value unless the variable was changed in some
     * gross way by a trace (e.g. it was unset and then recreated as an
     * array). 
     */

    if (TclIsVarScalar(varPtr) && !TclIsVarUndefined(varPtr)) {
        return varPtr->value.objPtr;
    }

    /*
     * A trace changed the value in some gross way. Return an empty string
     * object.
     */
    
    resultPtr = iPtr->emptyObjPtr;

    /*
     * If the variable doesn't exist anymore and no-one's using it, then
     * free up the relevant structures and hash table entries.
     */

    cleanup:
    if (TclIsVarUndefined(varPtr)) {
        CleanupVar(varPtr, arrayPtr);
    }
    return resultPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * TclSetIndexedScalar --
 *
 *      Change the Tcl object value of a local scalar variable in the active
 *      procedure, given its compile-time allocated index in the procedure's
 *      array of local variables.
 *
 * Results:
 *      Returns a pointer to the Tcl_Obj holding the new value of the
 *      variable given by localIndex. If the specified variable doesn't
 *      exist, or there is a clash in array usage, or an error occurs while
 *      executing variable traces, then NULL is returned and a message will
 *      be left in the interpreter's result if leaveErrorMsg is 1. Note
 *      that the returned object may not be the same one referenced by
 *      newValuePtr; this is because variable traces may modify the
 *      variable's value.
 *
 * Side effects:
 *      The value of the given variable is set. The reference count is
 *      decremented for any old value of the variable and incremented for
 *      its new value. If as a result of a variable trace the new value for
 *      the variable is not the same one referenced by newValuePtr, then
 *      newValuePtr's ref count is left unchanged. The ref count for the
 *      returned object is _not_ incremented to reflect the returned
 *      reference; if you want to keep a reference to the object you must
 *      increment its ref count yourself. This procedure does not create
 *      new variables, but only sets those recognized at compile time.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
TclSetIndexedScalar(interp, localIndex, newValuePtr, leaveErrorMsg)
    Tcl_Interp *interp;         /* Command interpreter in which variable is
                                 * to be found. */
    int localIndex;             /* Index of variable in procedure's array
                                 * of local variables. */
    Tcl_Obj *newValuePtr;       /* New value for variable. */
    int leaveErrorMsg;          /* 1 if to leave an error message in
                                 * the interpreter's result on an error.
                                 * Otherwise no error message is left. */
{
    Interp *iPtr = (Interp *) interp;
    CallFrame *varFramePtr = iPtr->varFramePtr;
                                /* Points to the procedure call frame whose
                                 * variables are currently in use. Same as
                                 * the current procedure's frame, if any,
                                 * unless an "uplevel" is executing. */
    Var *compiledLocals = varFramePtr->compiledLocals;
    register Var *varPtr;       /* Points to the variable's in-frame Var
                                 * structure. */
    char *varName;              /* Name of the local variable. */
    Tcl_Obj *oldValuePtr;
    Tcl_Obj *resultPtr = NULL;

#ifdef TCL_COMPILE_DEBUG
    Proc *procPtr = varFramePtr->procPtr;
    int localCt = procPtr->numCompiledLocals;

    if (compiledLocals == NULL) {
        fprintf(stderr, "\nTclSetIndexedScalar: can't set local %i in frame 0x%x, no compiled locals\n",
                localIndex, (unsigned int) varFramePtr);
        panic("TclSetIndexedScalar: no compiled locals in frame 0x%x",
                (unsigned int) varFramePtr);
    }
    if ((localIndex < 0) || (localIndex >= localCt)) {
        fprintf(stderr, "\nTclSetIndexedScalar: can't set local %i in frame 0x%x with %i locals\n",
                localIndex, (unsigned int) varFramePtr, localCt);
        panic("TclSetIndexedScalar: bad local index %i in frame 0x%x",
                localIndex, (unsigned int) varFramePtr);
    }
#endif /* TCL_COMPILE_DEBUG */
    
    varPtr = &(compiledLocals[localIndex]);
    varName = varPtr->name;

    /*
     * If varPtr is a link variable, we have a reference to some variable
     * that was created through an "upvar" or "global" command, or we have a
     * reference to a variable in an enclosing namespace. Traverse through
     * any links until we find the referenced variable.
     */
        
    while (TclIsVarLink(varPtr)) {
        varPtr = varPtr->value.linkPtr;
    }

    /*
     * If the variable is in a hashtable and its hPtr field is NULL, then we
     * may have an upvar to an array element where the array was deleted
     * or an upvar to a namespace variable whose namespace was deleted.
     * Generate an error (allowing the variable to be reset would screw up
     * our storage allocation and is meaningless anyway).
     */

    if ((varPtr->flags & VAR_IN_HASHTABLE) && (varPtr->hPtr == NULL)) {
        if (leaveErrorMsg) {
            if (TclIsVarArrayElement(varPtr)) {
                VarErrMsg(interp, varName, NULL, "set", danglingElement);
            } else {
                VarErrMsg(interp, varName, NULL, "set", danglingVar);
            }
        }
        return NULL;
    }

    /*
     * It's an error to try to set an array variable itself.
     */

    if (TclIsVarArray(varPtr) && !TclIsVarUndefined(varPtr)) {
        if (leaveErrorMsg) {
            VarErrMsg(interp, varName, NULL, "set", isArray);
        }
        return NULL;
    }

    /*
     * Set the variable's new value and discard its old value. We don't
     * append with this "set" procedure so the old value isn't needed.
     */

    oldValuePtr = varPtr->value.objPtr;
    if (newValuePtr != oldValuePtr) {        /* set new value */
        varPtr->value.objPtr = newValuePtr;
        Tcl_IncrRefCount(newValuePtr);       /* var is another ref to obj */
        if (oldValuePtr != NULL) {
            TclDecrRefCount(oldValuePtr);    /* discard old value */
        }
    }
    TclSetVarScalar(varPtr);
    TclClearVarUndefined(varPtr);

    /*
     * Invoke any write traces for the variable.
     */

    if (varPtr->tracePtr != NULL) {
        char *msg = CallTraces(iPtr, /*arrayPtr*/ NULL, varPtr,
                varName, (char *) NULL, TCL_TRACE_WRITES);
        if (msg != NULL) {
            if (leaveErrorMsg) {
                VarErrMsg(interp, varName, NULL, "set", msg);
            }
            goto cleanup;
        }
    }

    /*
     * Return the variable's value unless the variable was changed in some
     * gross way by a trace (e.g. it was unset and then recreated as an
     * array). If it was changed is a gross way, just return an empty string
     * object.
     */

    if (TclIsVarScalar(varPtr) && !TclIsVarUndefined(varPtr)) {
        return varPtr->value.objPtr;
    }
    
    resultPtr = Tcl_NewObj();

    /*
     * If the variable doesn't exist anymore and no-one's using it, then
     * free up the relevant structures and hash table entries.
     */

    cleanup:
    if (TclIsVarUndefined(varPtr)) {
        CleanupVar(varPtr, NULL);
    }
    return resultPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * TclSetElementOfIndexedArray --
 *
 *      Change the Tcl object value of an element in a local array
 *      variable. The element is named by the object elemPtr while the array
 *      is specified by its index in the active procedure's array of
 *      compiler allocated local variables.
 *
 * Results:
 *      Returns a pointer to the Tcl_Obj holding the new value of the
 *      element. If the specified array or element doesn't exist, or there
 *      is a clash in array usage, or an error occurs while executing
 *      variable traces, then NULL is returned and a message will be left in
 *      the interpreter's result if leaveErrorMsg is 1. Note that the
 *      returned object may not be the same one referenced by newValuePtr;
 *      this is because variable traces may modify the variable's value.
 *
 * Side effects:
 *      The value of the given array element is set. The reference count is
 *      decremented for any old value of the element and incremented for its
 *      new value. If as a result of a variable trace the new value for the
 *      element is not the same one referenced by newValuePtr, then
 *      newValuePtr's ref count is left unchanged. The ref count for the
 *      returned object is _not_ incremented to reflect the returned
 *      reference; if you want to keep a reference to the object you must
 *      increment its ref count yourself. This procedure will not create new
 *      array variables, but only sets elements of those arrays recognized
 *      at compile time. However, if the entry doesn't exist then a new
 *      variable is created.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
TclSetElementOfIndexedArray(interp, localIndex, elemPtr, newValuePtr,
        leaveErrorMsg)
    Tcl_Interp *interp;         /* Command interpreter in which the array is
                                 * to be found. */
    int localIndex;             /* Index of array variable in procedure's
                                 * array of local variables. */
    Tcl_Obj *elemPtr;           /* Points to an object holding the name of
                                 * an element to set in the array. */
    Tcl_Obj *newValuePtr;       /* New value for variable. */
    int leaveErrorMsg;          /* 1 if to leave an error message in
                                 * the interpreter's result on an error.
                                 * Otherwise no error message is left. */
{
    Interp *iPtr = (Interp *) interp;
    CallFrame *varFramePtr = iPtr->varFramePtr;
                                /* Points to the procedure call frame whose
                                 * variables are currently in use. Same as
                                 * the current procedure's frame, if any,
                                 * unless an "uplevel" is executing. */
    Var *compiledLocals = varFramePtr->compiledLocals;
    Var *arrayPtr;              /* Points to the array's in-frame Var
                                 * structure. */
    char *arrayName;            /* Name of the local array. */
    char *elem;
    Tcl_HashEntry *hPtr;
    Var *varPtr = NULL;         /* Points to the element's Var structure
                                 * that we return. */
    Tcl_Obj *resultPtr = NULL;
    Tcl_Obj *oldValuePtr;
    int new;
    
#ifdef TCL_COMPILE_DEBUG
    Proc *procPtr = varFramePtr->procPtr;
    int localCt = procPtr->numCompiledLocals;

    if (compiledLocals == NULL) {
        fprintf(stderr, "\nTclSetElementOfIndexedArray: can't set element of local %i in frame 0x%x, no compiled locals\n",
                localIndex, (unsigned int) varFramePtr);
        panic("TclSetIndexedScalar: no compiled locals in frame 0x%x",
                (unsigned int) varFramePtr);
    }
    if ((localIndex < 0) || (localIndex >= localCt)) {
        fprintf(stderr, "\nTclSetIndexedScalar: can't set elememt of local %i in frame 0x%x with %i locals\n",
                localIndex, (unsigned int) varFramePtr, localCt);
        panic("TclSetElementOfIndexedArray: bad local index %i in frame 0x%x",
                localIndex, (unsigned int) varFramePtr);
    }
#endif /* TCL_COMPILE_DEBUG */

    elem = TclGetString(elemPtr);
    arrayPtr = &(compiledLocals[localIndex]);
    arrayName = arrayPtr->name;

    /*
     * If arrayPtr is a link variable, we have a reference to some variable
     * that was created through an "upvar" or "global" command, or we have a
     * reference to a variable in an enclosing namespace. Traverse through
     * any links until we find the referenced variable.
     */
        
    while (TclIsVarLink(arrayPtr)) {
        arrayPtr = arrayPtr->value.linkPtr;
    }

    /*
     * If the variable is in a hashtable and its hPtr field is NULL, then we
     * may have an upvar to an array element where the array was deleted
     * or an upvar to a namespace variable whose namespace was deleted.
     * Generate an error (allowing the variable to be reset would screw up
     * our storage allocation and is meaningless anyway).
     */

    if ((arrayPtr->flags & VAR_IN_HASHTABLE) && (arrayPtr->hPtr == NULL)) {
        if (leaveErrorMsg) {
            if (TclIsVarArrayElement(arrayPtr)) {
                VarErrMsg(interp, arrayName, elem, "set", danglingElement);
            } else {
                VarErrMsg(interp, arrayName, elem, "set", danglingVar);
            }
        }
        goto errorReturn;
    }

    /*
     * Make sure we're dealing with an array.
     */

    if (TclIsVarUndefined(arrayPtr) && !TclIsVarArrayElement(arrayPtr)) {
        TclSetVarArray(arrayPtr);
        arrayPtr->value.tablePtr =
            (Tcl_HashTable *) ckalloc(sizeof(Tcl_HashTable));
        Tcl_InitHashTable(arrayPtr->value.tablePtr, TCL_STRING_KEYS);
        TclClearVarUndefined(arrayPtr);
    } else if (!TclIsVarArray(arrayPtr)) {
        if (leaveErrorMsg) {
            VarErrMsg(interp, arrayName, elem, "set", needArray);
        }
        goto errorReturn;
    } 

    /*
     * Look up the element.
     */

    hPtr = Tcl_CreateHashEntry(arrayPtr->value.tablePtr, elem, &new);
    if (new) {
        if (arrayPtr->searchPtr != NULL) {
            DeleteSearches(arrayPtr);
        }
        varPtr = NewVar();
        Tcl_SetHashValue(hPtr, varPtr);
        varPtr->hPtr = hPtr;
        varPtr->nsPtr = varFramePtr->nsPtr;
        TclSetVarArrayElement(varPtr);
    }
    varPtr = (Var *) Tcl_GetHashValue(hPtr);

    /*
     * It's an error to try to set an array variable itself.
     */

    if (TclIsVarArray(varPtr)) {
        if (leaveErrorMsg) {
            VarErrMsg(interp, arrayName, elem, "set", isArray);
        }
        goto errorReturn;
    }

    /*
     * Set the variable's new value and discard the old one. We don't
     * append with this "set" procedure so the old value isn't needed.
     */

    oldValuePtr = varPtr->value.objPtr;
    if (newValuePtr != oldValuePtr) {        /* set new value */
        varPtr->value.objPtr = newValuePtr;
        Tcl_IncrRefCount(newValuePtr);       /* var is another ref to obj */
        if (oldValuePtr != NULL) {
            TclDecrRefCount(oldValuePtr);    /* discard old value */
        }
    }
    TclSetVarScalar(varPtr);
    TclClearVarUndefined(varPtr);

    /*
     * Invoke any write traces for the element variable.
     */

    if ((varPtr->tracePtr != NULL)
            || ((arrayPtr != NULL) && (arrayPtr->tracePtr != NULL))) {
        char *msg = CallTraces(iPtr, arrayPtr, varPtr, arrayName, elem,
                TCL_TRACE_WRITES);
        if (msg != NULL) {
            if (leaveErrorMsg) {
                VarErrMsg(interp, arrayName, elem, "set", msg);
            }
            goto errorReturn;
        }
    }

    /*
     * Return the element's value unless it was changed in some gross way by
     * a trace (e.g. it was unset and then recreated as an array). If it was
     * changed is a gross way, just return an empty string object.
     */

    if (TclIsVarScalar(varPtr) && !TclIsVarUndefined(varPtr)) {
        return varPtr->value.objPtr;
    }
    
    resultPtr = Tcl_NewObj();

    /*
     * An error. If the variable doesn't exist anymore and no-one's using
     * it, then free up the relevant structures and hash table entries.
     */

    errorReturn:
    if (varPtr != NULL) {
        if (TclIsVarUndefined(varPtr)) {
            CleanupVar(varPtr, NULL); /* note: array isn't in hashtable */
        }
    }
    return resultPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * TclIncrVar2 --
 *
 *      Given a two-part variable name, which may refer either to a scalar
 *      variable or an element of an array, increment the Tcl object value
 *      of the variable by a specified amount.
 *
 * Results:
 *      Returns a pointer to the Tcl_Obj holding the new value of the
 *      variable. If the specified variable doesn't exist, or there is a
 *      clash in array usage, or an error occurs while executing variable
 *      traces, then NULL is returned and a message will be left in
 *      the interpreter's result.
 *
 * Side effects:
 *      The value of the given variable is incremented by the specified
 *      amount. If either the array or the entry didn't exist then a new
 *      variable is created. The ref count for the returned object is _not_
 *      incremented to reflect the returned reference; if you want to keep a
 *      reference to the object you must increment its ref count yourself.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
TclIncrVar2(interp, part1Ptr, part2Ptr, incrAmount, flags)
    Tcl_Interp *interp;         /* Command interpreter in which variable is
                                 * to be found. */
    Tcl_Obj *part1Ptr;          /* Points to an object holding the name of
                                 * an array (if part2 is non-NULL) or the
                                 * name of a variable. */
    Tcl_Obj *part2Ptr;          /* If non-null, points to an object holding
                                 * the name of an element in the array
                                 * part1Ptr. */
    long incrAmount;            /* Amount to be added to variable. */
    int flags;                  /* Various flags that tell how to incr value:
                                 * any of TCL_GLOBAL_ONLY,
                                 * TCL_NAMESPACE_ONLY, TCL_APPEND_VALUE,
                                 * TCL_LIST_ELEMENT, TCL_LEAVE_ERR_MSG. */
{
    register Tcl_Obj *varValuePtr;
    Tcl_Obj *resultPtr;
    int createdNewObj;          /* Set 1 if var's value object is shared
                                 * so we must increment a copy (i.e. copy
                                 * on write). */
    long i;
    int result;

    varValuePtr = Tcl_ObjGetVar2(interp, part1Ptr, part2Ptr, flags);
    if (varValuePtr == NULL) {
        Tcl_AddObjErrorInfo(interp,
                "\n    (reading value of variable to increment)", -1);
        return NULL;
    }

    /*
     * Increment the variable's value. If the object is unshared we can
     * modify it directly, otherwise we must create a new copy to modify:
     * this is "copy on write". Then free the variable's old string
     * representation, if any, since it will no longer be valid.
     */

    createdNewObj = 0;
    if (Tcl_IsShared(varValuePtr)) {
        varValuePtr = Tcl_DuplicateObj(varValuePtr);
        createdNewObj = 1;
    }
    result = Tcl_GetLongFromObj(interp, varValuePtr, &i);
    if (result != TCL_OK) {
        if (createdNewObj) {
            Tcl_DecrRefCount(varValuePtr); /* free unneeded copy */
        }
        return NULL;
    }
    Tcl_SetLongObj(varValuePtr, (i + incrAmount));

    /*
     * Store the variable's new value and run any write traces.
     */
    
    resultPtr = Tcl_ObjSetVar2(interp, part1Ptr, part2Ptr, varValuePtr, flags);
    if (resultPtr == NULL) {
        return NULL;
    }
    return resultPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * TclIncrIndexedScalar --
 *
 *      Increments the Tcl object value of a local scalar variable in the
 *      active procedure, given its compile-time allocated index in the
 *      procedure's array of local variables.
 *
 * Results:
 *      Returns a pointer to the Tcl_Obj holding the new value of the
 *      variable given by localIndex. If the specified variable doesn't
 *      exist, or there is a clash in array usage, or an error occurs while
 *      executing variable traces, then NULL is returned and a message will
 *      be left in the interpreter's result. 
 *
 * Side effects:
 *      The value of the given variable is incremented by the specified
 *      amount. The ref count for the returned object is _not_ incremented
 *      to reflect the returned reference; if you want to keep a reference
 *      to the object you must increment its ref count yourself.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
TclIncrIndexedScalar(interp, localIndex, incrAmount)
    Tcl_Interp *interp;         /* Command interpreter in which variable is
                                 * to be found. */
    int localIndex;             /* Index of variable in procedure's array
                                 * of local variables. */
    long incrAmount;            /* Amount to be added to variable. */
{
    register Tcl_Obj *varValuePtr;
    Tcl_Obj *resultPtr;
    int createdNewObj;          /* Set 1 if var's value object is shared
                                 * so we must increment a copy (i.e. copy
                                 * on write). */
    long i;
    int result;

    varValuePtr = TclGetIndexedScalar(interp, localIndex,
            /*leaveErrorMsg*/ 1);
    if (varValuePtr == NULL) {
        Tcl_AddObjErrorInfo(interp,
                "\n    (reading value of variable to increment)", -1);
        return NULL;
    }

    /*
     * Reach into the object's representation to extract and increment the
     * variable's value. If the object is unshared we can modify it
     * directly, otherwise we must create a new copy to modify: this is
     * "copy on write". Then free the variable's old string representation,
     * if any, since it will no longer be valid.
     */

    createdNewObj = 0;
    if (Tcl_IsShared(varValuePtr)) {
        createdNewObj = 1;
        varValuePtr = Tcl_DuplicateObj(varValuePtr);
    }
    result = Tcl_GetLongFromObj(interp, varValuePtr, &i);
    if (result != TCL_OK) {
        if (createdNewObj) {
            Tcl_DecrRefCount(varValuePtr); /* free unneeded copy */
        }
        return NULL;
    }
    Tcl_SetLongObj(varValuePtr, (i + incrAmount));

    /*
     * Store the variable's new value and run any write traces.
     */
    
    resultPtr = TclSetIndexedScalar(interp, localIndex, varValuePtr,
            /*leaveErrorMsg*/ 1);
    if (resultPtr == NULL) {
        return NULL;
    }
    return resultPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * TclIncrElementOfIndexedArray --
 *
 *      Increments the Tcl object value of an element in a local array
 *      variable. The element is named by the object elemPtr while the array
 *      is specified by its index in the active procedure's array of
 *      compiler allocated local variables.
 *
 * Results:
 *      Returns a pointer to the Tcl_Obj holding the new value of the
 *      element. If the specified array or element doesn't exist, or there
 *      is a clash in array usage, or an error occurs while executing
 *      variable traces, then NULL is returned and a message will be left in
 *      the interpreter's result.
 *
 * Side effects:
 *      The value of the given array element is incremented by the specified
 *      amount. The ref count for the returned object is _not_ incremented
 *      to reflect the returned reference; if you want to keep a reference
 *      to the object you must increment its ref count yourself. If the
 *      entry doesn't exist then a new variable is created.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
TclIncrElementOfIndexedArray(interp, localIndex, elemPtr, incrAmount)
    Tcl_Interp *interp;         /* Command interpreter in which the array is
                                 * to be found. */
    int localIndex;             /* Index of array variable in procedure's
                                 * array of local variables. */
    Tcl_Obj *elemPtr;           /* Points to an object holding the name of
                                 * an element to increment in the array. */
    long incrAmount;            /* Amount to be added to variable. */
{
    register Tcl_Obj *varValuePtr;
    Tcl_Obj *resultPtr;
    int createdNewObj;          /* Set 1 if var's value object is shared
                                 * so we must increment a copy (i.e. copy
                                 * on write). */
    long i;
    int result;

    varValuePtr = TclGetElementOfIndexedArray(interp, localIndex, elemPtr,
            /*leaveErrorMsg*/ 1);
    if (varValuePtr == NULL) {
        Tcl_AddObjErrorInfo(interp,
                "\n    (reading value of variable to increment)", -1);
        return NULL;
    }

    /*
     * Reach into the object's representation to extract and increment the
     * variable's value. If the object is unshared we can modify it
     * directly, otherwise we must create a new copy to modify: this is
     * "copy on write". Then free the variable's old string representation,
     * if any, since it will no longer be valid.
     */

    createdNewObj = 0;
    if (Tcl_IsShared(varValuePtr)) {
        createdNewObj = 1;
        varValuePtr = Tcl_DuplicateObj(varValuePtr);
    }
    result = Tcl_GetLongFromObj(interp, varValuePtr, &i);
    if (result != TCL_OK) {
        if (createdNewObj) {
            Tcl_DecrRefCount(varValuePtr); /* free unneeded copy */
        }
        return NULL;
    }
    Tcl_SetLongObj(varValuePtr, (i + incrAmount));
    
    /*
     * Store the variable's new value and run any write traces.
     */
    
    resultPtr = TclSetElementOfIndexedArray(interp, localIndex, elemPtr,
            varValuePtr,
            /*leaveErrorMsg*/ 1);
    if (resultPtr == NULL) {
        return NULL;
    }
    return resultPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_UnsetVar --
 *
 *      Delete a variable, so that it may not be accessed anymore.
 *
 * Results:
 *      Returns TCL_OK if the variable was successfully deleted, TCL_ERROR
 *      if the variable can't be unset.  In the event of an error,
 *      if the TCL_LEAVE_ERR_MSG flag is set then an error message
 *      is left in the interp's result.
 *
 * Side effects:
 *      If varName is defined as a local or global variable in interp,
 *      it is deleted.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_UnsetVar(interp, varName, flags)
    Tcl_Interp *interp;         /* Command interpreter in which varName is
                                 * to be looked up. */
    char *varName;              /* Name of a variable in interp.  May be
                                 * either a scalar name or an array name
                                 * or an element in an array. */
    int flags;                  /* OR-ed combination of any of
                                 * TCL_GLOBAL_ONLY, TCL_NAMESPACE_ONLY or
                                 * TCL_LEAVE_ERR_MSG. */
{
    return Tcl_UnsetVar2(interp, varName, (char *) NULL, flags);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_UnsetVar2 --
 *
 *      Delete a variable, given a 2-part name.
 *
 * Results:
 *      Returns TCL_OK if the variable was successfully deleted, TCL_ERROR
 *      if the variable can't be unset.  In the event of an error,
 *      if the TCL_LEAVE_ERR_MSG flag is set then an error message
 *      is left in the interp's result.
 *
 * Side effects:
 *      If part1 and part2 indicate a local or global variable in interp,
 *      it is deleted.  If part1 is an array name and part2 is NULL, then
 *      the whole array is deleted.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_UnsetVar2(interp, part1, part2, flags)
    Tcl_Interp *interp;         /* Command interpreter in which varName is
                                 * to be looked up. */
    char *part1;                /* Name of variable or array. */
    char *part2;                /* Name of element within array or NULL. */
    int flags;                  /* OR-ed combination of any of
                                 * TCL_GLOBAL_ONLY, TCL_NAMESPACE_ONLY,
                                 * TCL_LEAVE_ERR_MSG. */
{
    Var dummyVar;
    Var *varPtr, *dummyVarPtr;
    Interp *iPtr = (Interp *) interp;
    Var *arrayPtr;
    ActiveVarTrace *activePtr;
    Tcl_Obj *objPtr;
    int result;

    varPtr = TclLookupVar(interp, part1, part2, flags, "unset",
            /*createPart1*/ 0, /*createPart2*/ 0, &arrayPtr);
    if (varPtr == NULL) {
        return TCL_ERROR;
    }
    result = (TclIsVarUndefined(varPtr)? TCL_ERROR : TCL_OK);

    if ((arrayPtr != NULL) && (arrayPtr->searchPtr != NULL)) {
        DeleteSearches(arrayPtr);
    }

    /*
     * The code below is tricky, because of the possibility that
     * a trace procedure might try to access a variable being
     * deleted. To handle this situation gracefully, do things
     * in three steps:
     * 1. Copy the contents of the variable to a dummy variable
     *    structure, and mark the original Var structure as undefined.
     * 2. Invoke traces and clean up the variable, using the dummy copy.
     * 3. If at the end of this the original variable is still
     *    undefined and has no outstanding references, then delete
     *    it (but it could have gotten recreated by a trace).
     */

    dummyVar = *varPtr;
    TclSetVarUndefined(varPtr);
    TclSetVarScalar(varPtr);
    varPtr->value.objPtr = NULL; /* dummyVar points to any value object */
    varPtr->tracePtr = NULL;
    varPtr->searchPtr = NULL;

    /*
     * Call trace procedures for the variable being deleted. Then delete
     * its traces. Be sure to abort any other traces for the variable
     * that are still pending. Special tricks:
     * 1. We need to increment varPtr's refCount around this: CallTraces
     *    will use dummyVar so it won't increment varPtr's refCount itself.
     * 2. Turn off the VAR_TRACE_ACTIVE flag in dummyVar: we want to
     *    call unset traces even if other traces are pending.
     */

    if ((dummyVar.tracePtr != NULL)
            || ((arrayPtr != NULL) && (arrayPtr->tracePtr != NULL))) {
        varPtr->refCount++;
        dummyVar.flags &= ~VAR_TRACE_ACTIVE;
        (void) CallTraces(iPtr, arrayPtr, &dummyVar, part1, part2,
                (flags & (TCL_GLOBAL_ONLY|TCL_NAMESPACE_ONLY)) | TCL_TRACE_UNSETS);
        while (dummyVar.tracePtr != NULL) {
            VarTrace *tracePtr = dummyVar.tracePtr;
            dummyVar.tracePtr = tracePtr->nextPtr;
            ckfree((char *) tracePtr);
        }
        for (activePtr = iPtr->activeTracePtr;  activePtr != NULL;
             activePtr = activePtr->nextPtr) {
            if (activePtr->varPtr == varPtr) {
                activePtr->nextTracePtr = NULL;
            }
        }
        varPtr->refCount--;
    }

    /*
     * If the variable is an array, delete all of its elements. This must be
     * done after calling the traces on the array, above (that's the way
     * traces are defined). If it is a scalar, "discard" its object
     * (decrement the ref count of its object, if any).
     */

    dummyVarPtr = &dummyVar;
    if (TclIsVarArray(dummyVarPtr) && !TclIsVarUndefined(dummyVarPtr)) {
        /*
         * Deleting the elements of the array may cause traces to be fired
         * on those elements.  Before deleting them, bump the reference count
         * of the array, so that if those trace procs make a global or upvar
         * link to the array, the array is not deleted when the call stack
         * gets popped (we will delete the array ourselves later in this
         * function).
         *
         * Bumping the count can lead to the odd situation that elements of the
         * array are being deleted when the array still exists, but since the
         * array is about to be removed anyway, that shouldn't really matter.
         */
        varPtr->refCount++;
        DeleteArray(iPtr, part1, dummyVarPtr,
                (flags & (TCL_GLOBAL_ONLY|TCL_NAMESPACE_ONLY)) | TCL_TRACE_UNSETS);
        /* Decr ref count */
        varPtr->refCount--;
    }
    if (TclIsVarScalar(dummyVarPtr)
            && (dummyVarPtr->value.objPtr != NULL)) {
        objPtr = dummyVarPtr->value.objPtr;
        TclDecrRefCount(objPtr);
        dummyVarPtr->value.objPtr = NULL;
    }

    /*
     * If the variable was a namespace variable, decrement its reference count.
     */
    
    if (varPtr->flags & VAR_NAMESPACE_VAR) {
        varPtr->flags &= ~VAR_NAMESPACE_VAR;
        varPtr->refCount--;
    }

    /*
     * It's an error to unset an undefined variable.
     */
        
    if (result != TCL_OK) {
        if (flags & TCL_LEAVE_ERR_MSG) {
            VarErrMsg(interp, part1, part2, "unset", 
                    ((arrayPtr == NULL) ? noSuchVar : noSuchElement));
        }
    }

    /*
     * Finally, if the variable is truly not in use then free up its Var
     * structure and remove it from its hash table, if any. The ref count of
     * its value object, if any, was decremented above.
     */

    CleanupVar(varPtr, arrayPtr);
    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_TraceVar --
 *
 *      Arrange for reads and/or writes to a variable to cause a
 *      procedure to be invoked, which can monitor the operations
 *      and/or change their actions.
 *
 * Results:
 *      A standard Tcl return value.
 *
 * Side effects:
 *      A trace is set up on the variable given by varName, such that
 *      future references to the variable will be intermediated by
 *      proc.  See the manual entry for complete details on the calling
 *      sequence for proc.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_TraceVar(interp, varName, flags, proc, clientData)
    Tcl_Interp *interp;         /* Interpreter in which variable is
                                 * to be traced. */
    char *varName;              /* Name of variable;  may end with "(index)"
                                 * to signify an array reference. */
    int flags;                  /* OR-ed collection of bits, including any
                                 * of TCL_TRACE_READS, TCL_TRACE_WRITES,
                                 * TCL_TRACE_UNSETS, TCL_GLOBAL_ONLY, and
                                 * TCL_NAMESPACE_ONLY. */
    Tcl_VarTraceProc *proc;     /* Procedure to call when specified ops are
                                 * invoked upon varName. */
    ClientData clientData;      /* Arbitrary argument to pass to proc. */
{
    return Tcl_TraceVar2(interp, varName, (char *) NULL, 
            flags, proc, clientData);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_TraceVar2 --
 *
 *      Arrange for reads and/or writes to a variable to cause a
 *      procedure to be invoked, which can monitor the operations
 *      and/or change their actions.
 *
 * Results:
 *      A standard Tcl return value.
 *
 * Side effects:
 *      A trace is set up on the variable given by part1 and part2, such
 *      that future references to the variable will be intermediated by
 *      proc.  See the manual entry for complete details on the calling
 *      sequence for proc.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_TraceVar2(interp, part1, part2, flags, proc, clientData)
    Tcl_Interp *interp;         /* Interpreter in which variable is
                                 * to be traced. */
    char *part1;                /* Name of scalar variable or array. */
    char *part2;                /* Name of element within array;  NULL means
                                 * trace applies to scalar variable or array
                                 * as-a-whole. */
    int flags;                  /* OR-ed collection of bits, including any
                                 * of TCL_TRACE_READS, TCL_TRACE_WRITES,
                                 * TCL_TRACE_UNSETS, TCL_GLOBAL_ONLY,
                                 * and TCL_NAMESPACE_ONLY. */
    Tcl_VarTraceProc *proc;     /* Procedure to call when specified ops are
                                 * invoked upon varName. */
    ClientData clientData;      /* Arbitrary argument to pass to proc. */
{
    Var *varPtr, *arrayPtr;
    register VarTrace *tracePtr;

    varPtr = TclLookupVar(interp, part1, part2, (flags | TCL_LEAVE_ERR_MSG),
            "trace", /*createPart1*/ 1, /*createPart2*/ 1, &arrayPtr);
    if (varPtr == NULL) {
        return TCL_ERROR;
    }

    /*
     * Set up trace information.
     */

    tracePtr = (VarTrace *) ckalloc(sizeof(VarTrace));
    tracePtr->traceProc = proc;
    tracePtr->clientData = clientData;
    tracePtr->flags = 
        flags & (TCL_TRACE_READS | TCL_TRACE_WRITES | TCL_TRACE_UNSETS | 
                TCL_TRACE_ARRAY);
    tracePtr->nextPtr = varPtr->tracePtr;
    varPtr->tracePtr = tracePtr;
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_UntraceVar --
 *
 *      Remove a previously-created trace for a variable.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      If there exists a trace for the variable given by varName
 *      with the given flags, proc, and clientData, then that trace
 *      is removed.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_UntraceVar(interp, varName, flags, proc, clientData)
    Tcl_Interp *interp;         /* Interpreter containing variable. */
    char *varName;              /* Name of variable; may end with "(index)"
                                 * to signify an array reference. */
    int flags;                  /* OR-ed collection of bits describing
                                 * current trace, including any of
                                 * TCL_TRACE_READS, TCL_TRACE_WRITES,
                                 * TCL_TRACE_UNSETS, TCL_GLOBAL_ONLY
                                 * and TCL_NAMESPACE_ONLY. */
    Tcl_VarTraceProc *proc;     /* Procedure assocated with trace. */
    ClientData clientData;      /* Arbitrary argument to pass to proc. */
{
    Tcl_UntraceVar2(interp, varName, (char *) NULL, flags, proc, clientData);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_UntraceVar2 --
 *
 *      Remove a previously-created trace for a variable.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      If there exists a trace for the variable given by part1
 *      and part2 with the given flags, proc, and clientData, then
 *      that trace is removed.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_UntraceVar2(interp, part1, part2, flags, proc, clientData)
    Tcl_Interp *interp;         /* Interpreter containing variable. */
    char *part1;                /* Name of variable or array. */
    char *part2;                /* Name of element within array;  NULL means
                                 * trace applies to scalar variable or array
                                 * as-a-whole. */
    int flags;                  /* OR-ed collection of bits describing
                                 * current trace, including any of
                                 * TCL_TRACE_READS, TCL_TRACE_WRITES,
                                 * TCL_TRACE_UNSETS, TCL_GLOBAL_ONLY,
                                 * and TCL_NAMESPACE_ONLY. */
    Tcl_VarTraceProc *proc;     /* Procedure assocated with trace. */
    ClientData clientData;      /* Arbitrary argument to pass to proc. */
{
    register VarTrace *tracePtr;
    VarTrace *prevPtr;
    Var *varPtr, *arrayPtr;
    Interp *iPtr = (Interp *) interp;
    ActiveVarTrace *activePtr;

    varPtr = TclLookupVar(interp, part1, part2,
            flags & (TCL_GLOBAL_ONLY|TCL_NAMESPACE_ONLY),
            /*msg*/ (char *) NULL,
            /*createPart1*/ 0, /*createPart2*/ 0, &arrayPtr);
    if (varPtr == NULL) {
        return;
    }

    flags &= (TCL_TRACE_READS | TCL_TRACE_WRITES | TCL_TRACE_UNSETS |
            TCL_TRACE_ARRAY);
    for (tracePtr = varPtr->tracePtr, prevPtr = NULL;  ;
         prevPtr = tracePtr, tracePtr = tracePtr->nextPtr) {
        if (tracePtr == NULL) {
            return;
        }
        if ((tracePtr->traceProc == proc) && (tracePtr->flags == flags)
                && (tracePtr->clientData == clientData)) {
            break;
        }
    }

    /*
     * The code below makes it possible to delete traces while traces
     * are active: it makes sure that the deleted trace won't be
     * processed by CallTraces.
     */

    for (activePtr = iPtr->activeTracePtr;  activePtr != NULL;
         activePtr = activePtr->nextPtr) {
        if (activePtr->nextTracePtr == tracePtr) {
            activePtr->nextTracePtr = tracePtr->nextPtr;
        }
    }
    if (prevPtr == NULL) {
        varPtr->tracePtr = tracePtr->nextPtr;
    } else {
        prevPtr->nextPtr = tracePtr->nextPtr;
    }
    ckfree((char *) tracePtr);

    /*
     * If this is the last trace on the variable, and the variable is
     * unset and unused, then free up the variable.
     */

    if (TclIsVarUndefined(varPtr)) {
        CleanupVar(varPtr, (Var *) NULL);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_VarTraceInfo --
 *
 *      Return the clientData value associated with a trace on a
 *      variable.  This procedure can also be used to step through
 *      all of the traces on a particular variable that have the
 *      same trace procedure.
 *
 * Results:
 *      The return value is the clientData value associated with
 *      a trace on the given variable.  Information will only be
 *      returned for a trace with proc as trace procedure.  If
 *      the clientData argument is NULL then the first such trace is
 *      returned;  otherwise, the next relevant one after the one
 *      given by clientData will be returned.  If the variable
 *      doesn't exist, or if there are no (more) traces for it,
 *      then NULL is returned.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

ClientData
Tcl_VarTraceInfo(interp, varName, flags, proc, prevClientData)
    Tcl_Interp *interp;         /* Interpreter containing variable. */
    char *varName;              /* Name of variable;  may end with "(index)"
                                 * to signify an array reference. */
    int flags;                  /* OR-ed combo or TCL_GLOBAL_ONLY,
                                 * TCL_NAMESPACE_ONLY (can be 0). */
    Tcl_VarTraceProc *proc;     /* Procedure assocated with trace. */
    ClientData prevClientData;  /* If non-NULL, gives last value returned
                                 * by this procedure, so this call will
                                 * return the next trace after that one.
                                 * If NULL, this call will return the
                                 * first trace. */
{
    return Tcl_VarTraceInfo2(interp, varName, (char *) NULL,
            flags, proc, prevClientData);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_VarTraceInfo2 --
 *
 *      Same as Tcl_VarTraceInfo, except takes name in two pieces
 *      instead of one.
 *
 * Results:
 *      Same as Tcl_VarTraceInfo.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

ClientData
Tcl_VarTraceInfo2(interp, part1, part2, flags, proc, prevClientData)
    Tcl_Interp *interp;         /* Interpreter containing variable. */
    char *part1;                /* Name of variable or array. */
    char *part2;                /* Name of element within array;  NULL means
                                 * trace applies to scalar variable or array
                                 * as-a-whole. */
    int flags;                  /* OR-ed combination of TCL_GLOBAL_ONLY,
                                 * TCL_NAMESPACE_ONLY. */
    Tcl_VarTraceProc *proc;     /* Procedure assocated with trace. */
    ClientData prevClientData;  /* If non-NULL, gives last value returned
                                 * by this procedure, so this call will
                                 * return the next trace after that one.
                                 * If NULL, this call will return the
                                 * first trace. */
{
    register VarTrace *tracePtr;
    Var *varPtr, *arrayPtr;

    varPtr = TclLookupVar(interp, part1, part2,
            flags & (TCL_GLOBAL_ONLY|TCL_NAMESPACE_ONLY),
            /*msg*/ (char *) NULL,
            /*createPart1*/ 0, /*createPart2*/ 0, &arrayPtr);
    if (varPtr == NULL) {
        return NULL;
    }

    /*
     * Find the relevant trace, if any, and return its clientData.
     */

    tracePtr = varPtr->tracePtr;
    if (prevClientData != NULL) {
        for ( ;  tracePtr != NULL;  tracePtr = tracePtr->nextPtr) {
            if ((tracePtr->clientData == prevClientData)
                    && (tracePtr->traceProc == proc)) {
                tracePtr = tracePtr->nextPtr;
                break;
            }
        }
    }
    for ( ;  tracePtr != NULL;  tracePtr = tracePtr->nextPtr) {
        if (tracePtr->traceProc == proc) {
            return tracePtr->clientData;
        }
    }
    return NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_UnsetObjCmd --
 *
 *      This object-based procedure is invoked to process the "unset" Tcl
 *      command. See the user documentation for details on what it does.
 *
 * Results:
 *      A standard Tcl object result value.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

        /* ARGSUSED */
int
Tcl_UnsetObjCmd(dummy, interp, objc, objv)
    ClientData dummy;           /* Not used. */
    Tcl_Interp *interp;         /* Current interpreter. */
    int objc;                   /* Number of arguments. */
    Tcl_Obj *CONST objv[];      /* Argument objects. */
{
    register int i;
    register char *name;

    if (objc < 2) {
        Tcl_WrongNumArgs(interp, 1, objv, "varName ?varName ...?");
        return TCL_ERROR;
    }
    
    for (i = 1;  i < objc;  i++) {
        name = TclGetString(objv[i]);
        if (Tcl_UnsetVar2(interp, name, (char *) NULL,
                TCL_LEAVE_ERR_MSG) != TCL_OK) {
            return TCL_ERROR;
        }
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_AppendObjCmd --
 *
 *      This object-based procedure is invoked to process the "append" 
 *      Tcl command. See the user documentation for details on what it does.
 *
 * Results:
 *      A standard Tcl object result value.
 *
 * Side effects:
 *      A variable's value may be changed.
 *
 *----------------------------------------------------------------------
 */

        /* ARGSUSED */
int
Tcl_AppendObjCmd(dummy, interp, objc, objv)
    ClientData dummy;           /* Not used. */
    Tcl_Interp *interp;         /* Current interpreter. */
    int objc;                   /* Number of arguments. */
    Tcl_Obj *CONST objv[];      /* Argument objects. */
{
    register Tcl_Obj *varValuePtr = NULL;
                                        /* Initialized to avoid compiler
                                         * warning. */
    int i;

    if (objc < 2) {
        Tcl_WrongNumArgs(interp, 1, objv, "varName ?value value ...?");
        return TCL_ERROR;
    }
    if (objc == 2) {
        varValuePtr = Tcl_ObjGetVar2(interp, objv[1], NULL, TCL_LEAVE_ERR_MSG);
        if (varValuePtr == NULL) {
            return TCL_ERROR;
        }
    } else {
        for (i = 2;  i < objc;  i++) {
            varValuePtr = Tcl_ObjSetVar2(interp, objv[1], (Tcl_Obj *) NULL,
                    objv[i], (TCL_APPEND_VALUE | TCL_LEAVE_ERR_MSG));
            if (varValuePtr == NULL) {
                return TCL_ERROR;
            }
        }
    }
    Tcl_SetObjResult(interp, varValuePtr);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_LappendObjCmd --
 *
 *      This object-based procedure is invoked to process the "lappend" 
 *      Tcl command. See the user documentation for details on what it does.
 *
 * Results:
 *      A standard Tcl object result value.
 *
 * Side effects:
 *      A variable's value may be changed.
 *
 *----------------------------------------------------------------------
 */

        /* ARGSUSED */
int
Tcl_LappendObjCmd(dummy, interp, objc, objv)
    ClientData dummy;           /* Not used. */
    Tcl_Interp *interp;         /* Current interpreter. */
    int objc;                   /* Number of arguments. */
    Tcl_Obj *CONST objv[];      /* Argument objects. */
{
    Tcl_Obj *varValuePtr, *newValuePtr;
    register List *listRepPtr;
    register Tcl_Obj **elemPtrs;
    int numElems, numRequired, createdNewObj, createVar, i, j;

    if (objc < 2) {
        Tcl_WrongNumArgs(interp, 1, objv, "varName ?value value ...?");
        return TCL_ERROR;
    }
    if (objc == 2) {
        newValuePtr = Tcl_ObjGetVar2(interp, objv[1], (Tcl_Obj *) NULL,
                (TCL_LEAVE_ERR_MSG));
        if (newValuePtr == NULL) {
            /*
             * The variable doesn't exist yet. Just create it with an empty
             * initial value.
             */
            
            Tcl_Obj *nullObjPtr = Tcl_NewObj();
            newValuePtr = Tcl_ObjSetVar2(interp, objv[1], NULL,
                    nullObjPtr, TCL_LEAVE_ERR_MSG);
            if (newValuePtr == NULL) {
                Tcl_DecrRefCount(nullObjPtr); /* free unneeded object */
                return TCL_ERROR;
            }
        }
    } else {
        /*
         * We have arguments to append. We used to call Tcl_SetVar2 to
         * append each argument one at a time to ensure that traces were run
         * for each append step. We now append the arguments all at once
         * because it's faster. Note that a read trace and a write trace for
         * the variable will now each only be called once. Also, if the
         * variable's old value is unshared we modify it directly, otherwise
         * we create a new copy to modify: this is "copy on write".
         */

        createdNewObj = 0;
        createVar = 1;
        varValuePtr = Tcl_ObjGetVar2(interp, objv[1], NULL, 0);
        if (varValuePtr == NULL) {
            /*
             * We couldn't read the old value: either the var doesn't yet
             * exist or it's an array element. If it's new, we will try to
             * create it with Tcl_ObjSetVar2 below.
             */
            
            char *p, *varName;
            int nameBytes, i;

            varName = Tcl_GetStringFromObj(objv[1], &nameBytes);
            for (i = 0, p = varName;  i < nameBytes;  i++, p++) {
                if (*p == '(') {
                    p = (varName + nameBytes-1);        
                    if (*p == ')') { /* last char is ')' => array ref */
                        createVar = 0;
                    }
                    break;
                }
            }
            varValuePtr = Tcl_NewObj();
            createdNewObj = 1;
        } else if (Tcl_IsShared(varValuePtr)) { 
            varValuePtr = Tcl_DuplicateObj(varValuePtr);
            createdNewObj = 1;
        }

        /*
         * Convert the variable's old value to a list object if necessary.
         */

        if (varValuePtr->typePtr != &tclListType) {
            int result = tclListType.setFromAnyProc(interp, varValuePtr);
            if (result != TCL_OK) {
                if (createdNewObj) {
                    Tcl_DecrRefCount(varValuePtr); /* free unneeded obj. */
                }
                return result;
            }
        }
        listRepPtr = (List *) varValuePtr->internalRep.otherValuePtr;
        elemPtrs = listRepPtr->elements;
        numElems = listRepPtr->elemCount;

        /*
         * If there is no room in the current array of element pointers,
         * allocate a new, larger array and copy the pointers to it.
         */
        
        numRequired = numElems + (objc-2);
        if (numRequired > listRepPtr->maxElemCount) {
            int newMax = (2 * numRequired);
            Tcl_Obj **newElemPtrs = (Tcl_Obj **)
                ckalloc((unsigned) (newMax * sizeof(Tcl_Obj *)));
            
            memcpy((VOID *) newElemPtrs, (VOID *) elemPtrs,
                    (size_t) (numElems * sizeof(Tcl_Obj *)));
            listRepPtr->maxElemCount = newMax;
            listRepPtr->elements = newElemPtrs;
            ckfree((char *) elemPtrs);
            elemPtrs = newElemPtrs;
        }

        /*
         * Insert the new elements at the end of the list.
         */

        for (i = 2, j = numElems;  i < objc;  i++, j++) {
            elemPtrs[j] = objv[i];
            Tcl_IncrRefCount(objv[i]);
        }
        listRepPtr->elemCount = numRequired;

        /*
         * Invalidate and free any old string representation since it no
         * longer reflects the list's internal representation.
         */

        Tcl_InvalidateStringRep(varValuePtr);

        /*
         * Now store the list object back into the variable. If there is an
         * error setting the new value, decrement its ref count if it
         * was new and we didn't create the variable.
         */
        
        newValuePtr = Tcl_ObjSetVar2(interp, objv[1], NULL, varValuePtr,
                TCL_LEAVE_ERR_MSG);
        if (newValuePtr == NULL) {
            if (createdNewObj && !createVar) {
                Tcl_DecrRefCount(varValuePtr); /* free unneeded obj */
            }
            return TCL_ERROR;
        }
    }

    /*
     * Set the interpreter's object result to refer to the variable's value
     * object.
     */

    Tcl_SetObjResult(interp, newValuePtr);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ArrayObjCmd --
 *
 *      This object-based procedure is invoked to process the "array" Tcl
 *      command. See the user documentation for details on what it does.
 *
 * Results:
 *      A standard Tcl result object.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

        /* ARGSUSED */
int
Tcl_ArrayObjCmd(dummy, interp, objc, objv)
    ClientData dummy;           /* Not used. */
    Tcl_Interp *interp;         /* Current interpreter. */
    int objc;                   /* Number of arguments. */
    Tcl_Obj *CONST objv[];      /* Argument objects. */
{
    /*
     * The list of constants below should match the arrayOptions string array
     * below.
     */

    enum {ARRAY_ANYMORE, ARRAY_DONESEARCH,  ARRAY_EXISTS, ARRAY_GET,
          ARRAY_NAMES, ARRAY_NEXTELEMENT, ARRAY_SET, ARRAY_SIZE,
          ARRAY_STARTSEARCH, ARRAY_UNSET}; 
    static char *arrayOptions[] = {
        "anymore", "donesearch", "exists", "get", "names", "nextelement",
        "set", "size", "startsearch", "unset", (char *) NULL
    };

    Interp *iPtr = (Interp *) interp;
    Var *varPtr, *arrayPtr;
    Tcl_HashEntry *hPtr;
    Tcl_Obj *resultPtr = Tcl_GetObjResult(interp);
    int notArray;
    char *varName, *msg;
    int index, result;


    if (objc < 3) {
        Tcl_WrongNumArgs(interp, 1, objv, "option arrayName ?arg ...?");
        return TCL_ERROR;
    }

    if (Tcl_GetIndexFromObj(interp, objv[1], arrayOptions, "option",
            0, &index) != TCL_OK) {
        return TCL_ERROR;
    }

    /*
     * Locate the array variable (and it better be an array).
     */
    
    varName = TclGetString(objv[2]);
    varPtr = TclLookupVar(interp, varName, (char *) NULL, /*flags*/ 0,
            /*msg*/ 0, /*createPart1*/ 0, /*createPart2*/ 0, &arrayPtr);

    notArray = 0;
    if ((varPtr == NULL) || !TclIsVarArray(varPtr)
            || TclIsVarUndefined(varPtr)) {
        notArray = 1;
    }

    /*
     * Special array trace used to keep the env array in sync for
     * array names, array get, etc.
     */

    if (varPtr != NULL && varPtr->tracePtr != NULL) {
        msg = CallTraces(iPtr, arrayPtr, varPtr, varName, NULL,
                (TCL_LEAVE_ERR_MSG|TCL_NAMESPACE_ONLY|TCL_GLOBAL_ONLY|
                TCL_TRACE_ARRAY));
        if (msg != NULL) {
            VarErrMsg(interp, varName, NULL, "trace array", msg);
            return TCL_ERROR;
        }
    }

    switch (index) {
        case ARRAY_ANYMORE: {
            ArraySearch *searchPtr;
            char *searchId;
            
            if (objc != 4) {
                Tcl_WrongNumArgs(interp, 2, objv, 
                        "arrayName searchId");
                return TCL_ERROR;
            }
            if (notArray) {
                goto error;
            }
            searchId = Tcl_GetString(objv[3]);
            searchPtr = ParseSearchId(interp, varPtr, varName, searchId);
            if (searchPtr == NULL) {
                return TCL_ERROR;
            }
            while (1) {
                Var *varPtr2;

                if (searchPtr->nextEntry != NULL) {
                    varPtr2 = (Var *) Tcl_GetHashValue(searchPtr->nextEntry);
                    if (!TclIsVarUndefined(varPtr2)) {
                        break;
                    }
                }
                searchPtr->nextEntry = Tcl_NextHashEntry(&searchPtr->search);
                if (searchPtr->nextEntry == NULL) {
                    Tcl_SetIntObj(resultPtr, 0);
                    return TCL_OK;
                }
            }
            Tcl_SetIntObj(resultPtr, 1);
            break;
        }
        case ARRAY_DONESEARCH: {
            ArraySearch *searchPtr, *prevPtr;
            char *searchId;

            if (objc != 4) {
                Tcl_WrongNumArgs(interp, 2, objv, 
                        "arrayName searchId");
                return TCL_ERROR;
            }
            if (notArray) {
                goto error;
            }
            searchId = Tcl_GetString(objv[3]);
            searchPtr = ParseSearchId(interp, varPtr, varName, searchId);
            if (searchPtr == NULL) {
                return TCL_ERROR;
            }
            if (varPtr->searchPtr == searchPtr) {
                varPtr->searchPtr = searchPtr->nextPtr;
            } else {
                for (prevPtr = varPtr->searchPtr;  ;
                     prevPtr = prevPtr->nextPtr) {
                    if (prevPtr->nextPtr == searchPtr) {
                        prevPtr->nextPtr = searchPtr->nextPtr;
                        break;
                    }
                }
            }
            ckfree((char *) searchPtr);
            break;
        }
        case ARRAY_EXISTS: {
            if (objc != 3) {
                Tcl_WrongNumArgs(interp, 2, objv, "arrayName");
                return TCL_ERROR;
            }
            Tcl_SetIntObj(resultPtr, !notArray);
            break;
        }
        case ARRAY_GET: {
            Tcl_HashSearch search;
            Var *varPtr2;
            char *pattern = NULL;
            char *name;
            Tcl_Obj *namePtr, *valuePtr;
            
            if ((objc != 3) && (objc != 4)) {
                Tcl_WrongNumArgs(interp, 2, objv, "arrayName ?pattern?");
                return TCL_ERROR;
            }
            if (notArray) {
                return TCL_OK;
            }
            if (objc == 4) {
                pattern = TclGetString(objv[3]);
            }
            for (hPtr = Tcl_FirstHashEntry(varPtr->value.tablePtr, &search);
                 hPtr != NULL;  hPtr = Tcl_NextHashEntry(&search)) {
                varPtr2 = (Var *) Tcl_GetHashValue(hPtr);
                if (TclIsVarUndefined(varPtr2)) {
                    continue;
                }
                name = Tcl_GetHashKey(varPtr->value.tablePtr, hPtr);
                if ((objc == 4) && !Tcl_StringMatch(name, pattern)) {
                    continue;   /* element name doesn't match pattern */
                }
                
                namePtr = Tcl_NewStringObj(name, -1);
                result = Tcl_ListObjAppendElement(interp, resultPtr,
                        namePtr);
                if (result != TCL_OK) {
                    Tcl_DecrRefCount(namePtr); /* free unneeded name obj */
                    return result;
                }

                valuePtr = Tcl_ObjGetVar2(interp, objv[2], namePtr,
                        TCL_LEAVE_ERR_MSG);
                if (valuePtr == NULL) {
                    Tcl_DecrRefCount(namePtr); /* free unneeded name obj */
                    return result;
                }
                result = Tcl_ListObjAppendElement(interp, resultPtr,
                        valuePtr);
                if (result != TCL_OK) {
                    Tcl_DecrRefCount(namePtr); /* free unneeded name obj */
                    return result;
                }
            }
            break;
        }
        case ARRAY_NAMES: {
            Tcl_HashSearch search;
            Var *varPtr2;
            char *pattern = NULL;
            char *name;
            Tcl_Obj *namePtr;
            
            if ((objc != 3) && (objc != 4)) {
                Tcl_WrongNumArgs(interp, 2, objv, "arrayName ?pattern?");
                return TCL_ERROR;
            }
            if (notArray) {
                return TCL_OK;
            }
            if (objc == 4) {
                pattern = Tcl_GetString(objv[3]);
            }
            for (hPtr = Tcl_FirstHashEntry(varPtr->value.tablePtr, &search);
                 hPtr != NULL; hPtr = Tcl_NextHashEntry(&search)) {
                varPtr2 = (Var *) Tcl_GetHashValue(hPtr);
                if (TclIsVarUndefined(varPtr2)) {
                    continue;
                }
                name = Tcl_GetHashKey(varPtr->value.tablePtr, hPtr);
                if ((objc == 4) && !Tcl_StringMatch(name, pattern)) {
                    continue;   /* element name doesn't match pattern */
                }
                
                namePtr = Tcl_NewStringObj(name, -1);
                result = Tcl_ListObjAppendElement(interp, resultPtr, namePtr);
                if (result != TCL_OK) {
                    Tcl_DecrRefCount(namePtr); /* free unneeded name obj */
                    return result;
                }
            }
            break;
        }
        case ARRAY_NEXTELEMENT: {
            ArraySearch *searchPtr;
            char *searchId;
            Tcl_HashEntry *hPtr;
            
            if (objc != 4) {
                Tcl_WrongNumArgs(interp, 2, objv, 
                        "arrayName searchId");
                return TCL_ERROR;
            }
            if (notArray) {
                goto error;
            }
            searchId = Tcl_GetString(objv[3]);
            searchPtr = ParseSearchId(interp, varPtr, varName, searchId);
            if (searchPtr == NULL) {
                return TCL_ERROR;
            }
            while (1) {
                Var *varPtr2;

                hPtr = searchPtr->nextEntry;
                if (hPtr == NULL) {
                    hPtr = Tcl_NextHashEntry(&searchPtr->search);
                    if (hPtr == NULL) {
                        return TCL_OK;
                    }
                } else {
                    searchPtr->nextEntry = NULL;
                }
                varPtr2 = (Var *) Tcl_GetHashValue(hPtr);
                if (!TclIsVarUndefined(varPtr2)) {
                    break;
                }
            }
            Tcl_SetStringObj(resultPtr,
                    Tcl_GetHashKey(varPtr->value.tablePtr, hPtr), -1);
            break;
        }
        case ARRAY_SET: {
            if (objc != 4) {
                Tcl_WrongNumArgs(interp, 2, objv, "arrayName list");
                return TCL_ERROR;
            }
            return(TclArraySet(interp, objv[2], objv[3]));
        }
        case ARRAY_SIZE: {
            Tcl_HashSearch search;
            Var *varPtr2;
            int size;

            if (objc != 3) {
                Tcl_WrongNumArgs(interp, 2, objv, "arrayName");
                return TCL_ERROR;
            }
            size = 0;
            if (!notArray) {
                for (hPtr = Tcl_FirstHashEntry(varPtr->value.tablePtr, 
                        &search);
                     hPtr != NULL;  hPtr = Tcl_NextHashEntry(&search)) {
                    varPtr2 = (Var *) Tcl_GetHashValue(hPtr);
                    if (TclIsVarUndefined(varPtr2)) {
                        continue;
                    }
                    size++;
                }
            }
            Tcl_SetIntObj(resultPtr, size);
            break;
        }
        case ARRAY_STARTSEARCH: {
            ArraySearch *searchPtr;

            if (objc != 3) {
                Tcl_WrongNumArgs(interp, 2, objv, "arrayName");
                return TCL_ERROR;
            }
            if (notArray) {
                goto error;
            }
            searchPtr = (ArraySearch *) ckalloc(sizeof(ArraySearch));
            if (varPtr->searchPtr == NULL) {
                searchPtr->id = 1;
                Tcl_AppendStringsToObj(resultPtr, "s-1-", varName,
                        (char *) NULL);
            } else {
                char string[TCL_INTEGER_SPACE];

                searchPtr->id = varPtr->searchPtr->id + 1;
                TclFormatInt(string, searchPtr->id);
                Tcl_AppendStringsToObj(resultPtr, "s-", string, "-", varName,
                        (char *) NULL);
            }
            searchPtr->varPtr = varPtr;
            searchPtr->nextEntry = Tcl_FirstHashEntry(varPtr->value.tablePtr,
                    &searchPtr->search);
            searchPtr->nextPtr = varPtr->searchPtr;
            varPtr->searchPtr = searchPtr;
            break;
        }
        case ARRAY_UNSET: {
            Tcl_HashSearch search;
            Var *varPtr2;
            char *pattern = NULL;
            char *name;
          
            if ((objc != 3) && (objc != 4)) {
                Tcl_WrongNumArgs(interp, 2, objv, "arrayName ?pattern?");
                return TCL_ERROR;
            }
            if (notArray) {
                return TCL_OK;
            }
            if (objc == 3) {
                /*
                 * When no pattern is given, just unset the whole array
                 */
                if (Tcl_UnsetVar2(interp, varName, (char *) NULL, 0)
                        != TCL_OK) {
                    return TCL_ERROR;
                }
            } else {
                pattern = Tcl_GetString(objv[3]);
                for (hPtr = Tcl_FirstHashEntry(varPtr->value.tablePtr,
                        &search);
                     hPtr != NULL; hPtr = Tcl_NextHashEntry(&search)) {
                    varPtr2 = (Var *) Tcl_GetHashValue(hPtr);
                    if (TclIsVarUndefined(varPtr2)) {
                        continue;
                    }
                    name = Tcl_GetHashKey(varPtr->value.tablePtr, hPtr);
                    if (Tcl_StringMatch(name, pattern) &&
                            (Tcl_UnsetVar2(interp, varName, name, 0)
                                    != TCL_OK)) {
                        return TCL_ERROR;
                    }
                }
            }
            break;
        }
    }
    return TCL_OK;

    error:
    Tcl_AppendStringsToObj(resultPtr, "\"", varName, "\" isn't an array",
            (char *) NULL);
    return TCL_ERROR;
}

/*
 *----------------------------------------------------------------------
 *
 * TclArraySet --
 *
 *      Set the elements of an array.  If there are no elements to
 *      set, create an empty array.  This routine is used by the
 *      Tcl_ArrayObjCmd and by the TclSetupEnv routine.
 *
 * Results:
 *      A standard Tcl result object.
 *
 * Side effects:
 *      A variable will be created if one does not already exist.
 *
 *----------------------------------------------------------------------
 */

int
TclArraySet(interp, arrayNameObj, arrayElemObj)
    Tcl_Interp *interp;         /* Current interpreter. */
    Tcl_Obj *arrayNameObj;      /* The array name. */
    Tcl_Obj *arrayElemObj;      /* The array elements list.  If this is
                                 * NULL, create an empty array. */
{
    Var *varPtr, *arrayPtr;
    Tcl_Obj **elemPtrs;
    int result, elemLen, i;
    char *varName, *p;
    
    varName = TclGetString(arrayNameObj);
    for (p = varName; *p ; p++) {
        if (*p == '(') {
            do {
                p++;
            } while (*p != '\0');
            p--;
            if (*p == ')') {
                VarErrMsg(interp, varName, NULL, "set", needArray);
                return TCL_ERROR;
            }
            break;
        }
    }

    varPtr = TclLookupVar(interp, varName, (char *) NULL, /*flags*/ 0,
            /*msg*/ 0, /*createPart1*/ 0, /*createPart2*/ 0, &arrayPtr);

    if (arrayElemObj != NULL) {
        result = Tcl_ListObjGetElements(interp, arrayElemObj,
                &elemLen, &elemPtrs);
        if (result != TCL_OK) {
            return result;
        }
        if (elemLen & 1) {
            Tcl_ResetResult(interp);
            Tcl_AppendToObj(Tcl_GetObjResult(interp),
                    "list must have an even number of elements", -1);
            return TCL_ERROR;
        }
        if (elemLen > 0) {
            for (i = 0;  i < elemLen;  i += 2) {
                if (Tcl_ObjSetVar2(interp, arrayNameObj, elemPtrs[i],
                        elemPtrs[i+1], TCL_LEAVE_ERR_MSG) == NULL) {
                    result = TCL_ERROR;
                    break;
                }
            }
            return result;
        }
    }
    
    /*
     * The list is empty make sure we have an array, or create
     * one if necessary.
     */
    
    if (varPtr != NULL) {
        if (!TclIsVarUndefined(varPtr) && TclIsVarArray(varPtr)) {
            /*
             * Already an array, done.
             */
            
            return TCL_OK;
        }
        if (TclIsVarArrayElement(varPtr) || !TclIsVarUndefined(varPtr)) {
            /*
             * Either an array element, or a scalar: lose!
             */
            
            VarErrMsg(interp, varName, (char *)NULL, "array set", needArray);
            return TCL_ERROR;
        }
    } else {
        /*
         * Create variable for new array.
         */
        
        varPtr = TclLookupVar(interp, varName, (char *) NULL,
                TCL_LEAVE_ERR_MSG, "set",
                /*createPart1*/ 1, /*createPart2*/ 0, &arrayPtr);

        /*
         * Still couldn't do it - this can occur if a non-existent
         * namespace was specified
         */
        if (varPtr == NULL) {
            return TCL_ERROR;
        }
    }
    TclSetVarArray(varPtr);
    TclClearVarUndefined(varPtr);
    varPtr->value.tablePtr =
        (Tcl_HashTable *) ckalloc(sizeof(Tcl_HashTable));
    Tcl_InitHashTable(varPtr->value.tablePtr, TCL_STRING_KEYS);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * MakeUpvar --
 *
 *      This procedure does all of the work of the "global" and "upvar"
 *      commands.
 *
 * Results:
 *      A standard Tcl completion code. If an error occurs then an
 *      error message is left in iPtr->result.
 *
 * Side effects:
 *      The variable given by myName is linked to the variable in framePtr
 *      given by otherP1 and otherP2, so that references to myName are
 *      redirected to the other variable like a symbolic link.
 *
 *----------------------------------------------------------------------
 */

static int
MakeUpvar(iPtr, framePtr, otherP1, otherP2, otherFlags, myName, myFlags)
    Interp *iPtr;               /* Interpreter containing variables. Used
                                 * for error messages, too. */
    CallFrame *framePtr;        /* Call frame containing "other" variable.
                                 * NULL means use global :: context. */
    char *otherP1, *otherP2;    /* Two-part name of variable in framePtr. */
    int otherFlags;             /* 0, TCL_GLOBAL_ONLY or TCL_NAMESPACE_ONLY:
                                 * indicates scope of "other" variable. */
    char *myName;               /* Name of variable which will refer to
                                 * otherP1/otherP2. Must be a scalar. */
    int myFlags;                /* 0, TCL_GLOBAL_ONLY or TCL_NAMESPACE_ONLY:
                                 * indicates scope of myName. */
{
    Tcl_HashEntry *hPtr;
    Var *otherPtr, *varPtr, *arrayPtr;
    CallFrame *varFramePtr;
    CallFrame *savedFramePtr = NULL;  /* Init. to avoid compiler warning. */
    Tcl_HashTable *tablePtr;
    Namespace *nsPtr, *altNsPtr, *dummyNsPtr;
    char *tail;
    int new;

    /*
     * Find "other" in "framePtr". If not looking up other in just the
     * current namespace, temporarily replace the current var frame
     * pointer in the interpreter in order to use TclLookupVar.
     */

    if (!(otherFlags & TCL_NAMESPACE_ONLY)) {
        savedFramePtr = iPtr->varFramePtr;
        iPtr->varFramePtr = framePtr;
    }
    otherPtr = TclLookupVar((Tcl_Interp *) iPtr, otherP1, otherP2,
            (otherFlags | TCL_LEAVE_ERR_MSG), "access",
            /*createPart1*/ 1, /*createPart2*/ 1, &arrayPtr);
    if (!(otherFlags & TCL_NAMESPACE_ONLY)) {
        iPtr->varFramePtr = savedFramePtr;
    }
    if (otherPtr == NULL) {
        return TCL_ERROR;
    }

    /*
     * Now create a hashtable entry for "myName". Create it as either a
     * namespace variable or as a local variable in a procedure call
     * frame. Interpret myName as a namespace variable if:
     *    1) so requested by a TCL_GLOBAL_ONLY or TCL_NAMESPACE_ONLY flag,
     *    2) there is no active frame (we're at the global :: scope),
     *    3) the active frame was pushed to define the namespace context
     *       for a "namespace eval" or "namespace inscope" command,
     *    4) the name has namespace qualifiers ("::"s).
     * If creating myName in the active procedure, look first in the
     * frame's array of compiler-allocated local variables, then in its
     * hashtable for runtime-created local variables. Create that
     * procedure's local variable hashtable if necessary.
     */

    varFramePtr = iPtr->varFramePtr;
    if ((myFlags & (TCL_GLOBAL_ONLY | TCL_NAMESPACE_ONLY))
            || (varFramePtr == NULL)
            || !varFramePtr->isProcCallFrame
            || (strstr(myName, "::") != NULL)) {
        TclGetNamespaceForQualName((Tcl_Interp *) iPtr, myName,
                (Namespace *) NULL, myFlags, &nsPtr, &altNsPtr, &dummyNsPtr, &tail);

        if (nsPtr == NULL) {
            nsPtr = altNsPtr;
        }
        if (nsPtr == NULL) {
            Tcl_AppendResult((Tcl_Interp *) iPtr, "bad variable name \"",
                    myName, "\": unknown namespace", (char *) NULL);
            return TCL_ERROR;
        }
        
        /*
         * Check that we are not trying to create a namespace var linked to
         * a local variable in a procedure. If we allowed this, the local
         * variable in the shorter-lived procedure frame could go away
         * leaving the namespace var's reference invalid.
         */

        if ((otherP2 ? arrayPtr->nsPtr : otherPtr->nsPtr) == NULL) {
            Tcl_AppendResult((Tcl_Interp *) iPtr, "bad variable name \"",
                    myName, "\": upvar won't create namespace variable that refers to procedure variable",
                    (char *) NULL);
            return TCL_ERROR;
        }
        
        hPtr = Tcl_CreateHashEntry(&nsPtr->varTable, tail, &new);
        if (new) {
            varPtr = NewVar();
            Tcl_SetHashValue(hPtr, varPtr);
            varPtr->hPtr = hPtr;
            varPtr->nsPtr = nsPtr;
        } else {
            varPtr = (Var *) Tcl_GetHashValue(hPtr);
        }
    } else {                    /* look in the call frame */
        Proc *procPtr = varFramePtr->procPtr;
        int localCt = procPtr->numCompiledLocals;
        CompiledLocal *localPtr = procPtr->firstLocalPtr;
        Var *localVarPtr = varFramePtr->compiledLocals;
        int nameLen = strlen(myName);
        int i;

        varPtr = NULL;
        for (i = 0;  i < localCt;  i++) {
            if (!TclIsVarTemporary(localPtr)) {
                char *localName = localVarPtr->name;
                if ((myName[0] == localName[0])
                        && (nameLen == localPtr->nameLength)
                        && (strcmp(myName, localName) == 0)) {
                    varPtr = localVarPtr;
                    new = 0;
                    break;
                }
            }
            localVarPtr++;
            localPtr = localPtr->nextPtr;
        }
        if (varPtr == NULL) {   /* look in frame's local var hashtable */
            tablePtr = varFramePtr->varTablePtr;
            if (tablePtr == NULL) {
                tablePtr = (Tcl_HashTable *) ckalloc(sizeof(Tcl_HashTable));
                Tcl_InitHashTable(tablePtr, TCL_STRING_KEYS);
                varFramePtr->varTablePtr = tablePtr;
            }
            hPtr = Tcl_CreateHashEntry(tablePtr, myName, &new);
            if (new) {
                varPtr = NewVar();
                Tcl_SetHashValue(hPtr, varPtr);
                varPtr->hPtr = hPtr;
                varPtr->nsPtr = varFramePtr->nsPtr;
            } else {
                varPtr = (Var *) Tcl_GetHashValue(hPtr);
            }
        }
    }

    if (!new) {
        /*
         * The variable already exists. Make sure this variable "varPtr"
         * isn't the same as "otherPtr" (avoid circular links). Also, if
         * it's not an upvar then it's an error. If it is an upvar, then
         * just disconnect it from the thing it currently refers to.
         */

        if (varPtr == otherPtr) {
            Tcl_SetResult((Tcl_Interp *) iPtr,
                    "can't upvar from variable to itself", TCL_STATIC);
            return TCL_ERROR;
        }
        if (TclIsVarLink(varPtr)) {
            Var *linkPtr = varPtr->value.linkPtr;
            if (linkPtr == otherPtr) {
                return TCL_OK;
            }
            linkPtr->refCount--;
            if (TclIsVarUndefined(linkPtr)) {
                CleanupVar(linkPtr, (Var *) NULL);
            }
        } else if (!TclIsVarUndefined(varPtr)) {
            Tcl_AppendResult((Tcl_Interp *) iPtr, "variable \"", myName,
                    "\" already exists", (char *) NULL);
            return TCL_ERROR;
        } else if (varPtr->tracePtr != NULL) {
            Tcl_AppendResult((Tcl_Interp *) iPtr, "variable \"", myName,
                    "\" has traces: can't use for upvar", (char *) NULL);
            return TCL_ERROR;
        }
    }
    TclSetVarLink(varPtr);
    TclClearVarUndefined(varPtr);
    varPtr->value.linkPtr = otherPtr;
    otherPtr->refCount++;
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_UpVar --
 *
 *      This procedure links one variable to another, just like
 *      the "upvar" command.
 *
 * Results:
 *      A standard Tcl completion code.  If an error occurs then
 *      an error message is left in the interp's result.
 *
 * Side effects:
 *      The variable in frameName whose name is given by varName becomes
 *      accessible under the name localName, so that references to
 *      localName are redirected to the other variable like a symbolic
 *      link.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_UpVar(interp, frameName, varName, localName, flags)
    Tcl_Interp *interp;         /* Command interpreter in which varName is
                                 * to be looked up. */
    char *frameName;            /* Name of the frame containing the source
                                 * variable, such as "1" or "#0". */
    char *varName;              /* Name of a variable in interp to link to.
                                 * May be either a scalar name or an
                                 * element in an array. */
    char *localName;            /* Name of link variable. */
    int flags;                  /* 0, TCL_GLOBAL_ONLY or TCL_NAMESPACE_ONLY:
                                 * indicates scope of localName. */
{
    int result;
    CallFrame *framePtr;
    register char *p;

    result = TclGetFrame(interp, frameName, &framePtr);
    if (result == -1) {
        return TCL_ERROR;
    }

    /*
     * Figure out whether varName is an array reference, then call
     * MakeUpvar to do all the real work.
     */

    for (p = varName;  *p != '\0';  p++) {
        if (*p == '(') {
            char *openParen = p;
            do {
                p++;
            } while (*p != '\0');
            p--;
            if (*p != ')') {
                goto scalar;
            }
            *openParen = '\0';
            *p = '\0';
            result = MakeUpvar((Interp *) interp, framePtr, varName,
                    openParen+1, 0, localName, flags);
            *openParen = '(';
            *p = ')';
            return result;
        }
    }

    scalar:
    return MakeUpvar((Interp *) interp, framePtr, varName, (char *) NULL,
            0, localName, flags);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_UpVar2 --
 *
 *      This procedure links one variable to another, just like
 *      the "upvar" command.
 *
 * Results:
 *      A standard Tcl completion code.  If an error occurs then
 *      an error message is left in the interp's result.
 *
 * Side effects:
 *      The variable in frameName whose name is given by part1 and
 *      part2 becomes accessible under the name localName, so that
 *      references to localName are redirected to the other variable
 *      like a symbolic link.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_UpVar2(interp, frameName, part1, part2, localName, flags)
    Tcl_Interp *interp;         /* Interpreter containing variables.  Used
                                 * for error messages too. */
    char *frameName;            /* Name of the frame containing the source
                                 * variable, such as "1" or "#0". */
    char *part1, *part2;        /* Two parts of source variable name to
                                 * link to. */
    char *localName;            /* Name of link variable. */
    int flags;                  /* 0, TCL_GLOBAL_ONLY or TCL_NAMESPACE_ONLY:
                                 * indicates scope of localName. */
{
    int result;
    CallFrame *framePtr;

    result = TclGetFrame(interp, frameName, &framePtr);
    if (result == -1) {
        return TCL_ERROR;
    }
    return MakeUpvar((Interp *) interp, framePtr, part1, part2, 0,
            localName, flags);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetVariableFullName --
 *
 *      Given a Tcl_Var token returned by Tcl_FindNamespaceVar, this
 *      procedure appends to an object the namespace variable's full
 *      name, qualified by a sequence of parent namespace names.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      The variable's fully-qualified name is appended to the string
 *      representation of objPtr.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_GetVariableFullName(interp, variable, objPtr)
    Tcl_Interp *interp;         /* Interpreter containing the variable. */
    Tcl_Var variable;           /* Token for the variable returned by a
                                 * previous call to Tcl_FindNamespaceVar. */
    Tcl_Obj *objPtr;            /* Points to the object onto which the
                                 * variable's full name is appended. */
{
    Interp *iPtr = (Interp *) interp;
    register Var *varPtr = (Var *) variable;
    char *name;

    /*
     * Add the full name of the containing namespace (if any), followed by
     * the "::" separator, then the variable name.
     */

    if (varPtr != NULL) {
        if (!TclIsVarArrayElement(varPtr)) {
            if (varPtr->nsPtr != NULL) {
                Tcl_AppendToObj(objPtr, varPtr->nsPtr->fullName, -1);
                if (varPtr->nsPtr != iPtr->globalNsPtr) {
                    Tcl_AppendToObj(objPtr, "::", 2);
                }
            }
            if (varPtr->name != NULL) {
                Tcl_AppendToObj(objPtr, varPtr->name, -1);
            } else if (varPtr->hPtr != NULL) {
                name = Tcl_GetHashKey(varPtr->hPtr->tablePtr, varPtr->hPtr);
                Tcl_AppendToObj(objPtr, name, -1);
            }
        }
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GlobalObjCmd --
 *
 *      This object-based procedure is invoked to process the "global" Tcl
 *      command. See the user documentation for details on what it does.
 *
 * Results:
 *      A standard Tcl object result value.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_GlobalObjCmd(dummy, interp, objc, objv)
    ClientData dummy;           /* Not used. */
    Tcl_Interp *interp;         /* Current interpreter. */
    int objc;                   /* Number of arguments. */
    Tcl_Obj *CONST objv[];      /* Argument objects. */
{
    Interp *iPtr = (Interp *) interp;
    register Tcl_Obj *objPtr;
    char *varName;
    register char *tail;
    int result, i;

    if (objc < 2) {
        Tcl_WrongNumArgs(interp, 1, objv, "varName ?varName ...?");
        return TCL_ERROR;
    }

    /*
     * If we are not executing inside a Tcl procedure, just return.
     */
    
    if ((iPtr->varFramePtr == NULL)
            || !iPtr->varFramePtr->isProcCallFrame) {
        return TCL_OK;
    }

    for (i = 1;  i < objc;  i++) {
        /*
         * Make a local variable linked to its counterpart in the global ::
         * namespace.
         */
        
        objPtr = objv[i];
        varName = TclGetString(objPtr);

        /*
         * The variable name might have a scope qualifier, but the name for
         * the local "link" variable must be the simple name at the tail.
         */

        for (tail = varName;  *tail != '\0';  tail++) {
            /* empty body */
        }
        while ((tail > varName) && ((*tail != ':') || (*(tail-1) != ':'))) {
            tail--;
        }
        if (*tail == ':') {
            tail++;
        }

        /*
         * Link to the variable "varName" in the global :: namespace.
         */
        
        result = MakeUpvar(iPtr, (CallFrame *) NULL,
                varName, (char *) NULL, /*otherFlags*/ TCL_GLOBAL_ONLY,
                /*myName*/ tail, /*myFlags*/ 0);
        if (result != TCL_OK) {
            return result;
        }
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_VariableObjCmd --
 *
 *      Invoked to implement the "variable" command that creates one or more
 *      global variables. Handles the following syntax:
 *
 *          variable ?name value...? name ?value?
 *
 *      One or more variables can be created. The variables are initialized
 *      with the specified values. The value for the last variable is
 *      optional.
 *
 *      If the variable does not exist, it is created and given the optional
 *      value. If it already exists, it is simply set to the optional
 *      value. Normally, "name" is an unqualified name, so it is created in
 *      the current namespace. If it includes namespace qualifiers, it can
 *      be created in another namespace.
 *
 *      If the variable command is executed inside a Tcl procedure, it
 *      creates a local variable linked to the newly-created namespace
 *      variable.
 *
 * Results:
 *      Returns TCL_OK if the variable is found or created. Returns
 *      TCL_ERROR if anything goes wrong.
 *
 * Side effects:
 *      If anything goes wrong, this procedure returns an error message
 *      as the result in the interpreter's result object.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_VariableObjCmd(dummy, interp, objc, objv)
    ClientData dummy;           /* Not used. */
    Tcl_Interp *interp;         /* Current interpreter. */
    int objc;                   /* Number of arguments. */
    Tcl_Obj *CONST objv[];      /* Argument objects. */
{