shared_source/c_tcl_base_7_5_w_mods/tclinterp.c

/* $Header$ */
/* 
 * tclInterp.c --
 *
 *      This file implements the "interp" command which allows creation
 *      and manipulation of Tcl interpreters from within Tcl scripts.
 *
 * Copyright (c) 1995-1997 Sun Microsystems, Inc.
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclinterp.c,v 1.1.1.1 2001/06/13 04:40:36 dtashley Exp $
 */

#include <stdio.h>
#include "tclInt.h"
#include "tclPort.h"

/*
 * Counter for how many aliases were created (global)
 */

static int aliasCounter = 0;
TCL_DECLARE_MUTEX(cntMutex)

/*
 * struct Alias:
 *
 * Stores information about an alias. Is stored in the slave interpreter
 * and used by the source command to find the target command in the master
 * when the source command is invoked.
 */

typedef struct Alias {
    Tcl_Obj *namePtr;           /* Name of alias command in slave interp. */
    Tcl_Interp *targetInterp;   /* Interp in which target command will be
                                 * invoked. */
    Tcl_Obj *prefixPtr;         /* Tcl list making up the prefix of the
                                 * target command to be invoked in the target
                                 * interpreter.  Additional arguments
                                 * specified when calling the alias in the
                                 * slave interp will be appended to the prefix
                                 * before the command is invoked. */
    Tcl_Command slaveCmd;       /* Source command in slave interpreter,
                                 * bound to command that invokes the target
                                 * command in the target interpreter. */
    Tcl_HashEntry *aliasEntryPtr;
                                /* Entry for the alias hash table in slave.
                                 * This is used by alias deletion to remove
                                 * the alias from the slave interpreter
                                 * alias table. */
    Tcl_HashEntry *targetEntryPtr;
                                /* Entry for target command in master.
                                 * This is used in the master interpreter to
                                 * map back from the target command to aliases
                                 * redirecting to it. Random access to this
                                 * hash table is never required - we are using
                                 * a hash table only for convenience. */
} Alias;

/*
 *
 * struct Slave:
 *
 * Used by the "interp" command to record and find information about slave
 * interpreters. Maps from a command name in the master to information about
 * a slave interpreter, e.g. what aliases are defined in it.
 */

typedef struct Slave {
    Tcl_Interp *masterInterp;   /* Master interpreter for this slave. */
    Tcl_HashEntry *slaveEntryPtr;
                                /* Hash entry in masters slave table for
                                 * this slave interpreter.  Used to find
                                 * this record, and used when deleting the
                                 * slave interpreter to delete it from the
                                 * master's table. */
    Tcl_Interp  *slaveInterp;   /* The slave interpreter. */
    Tcl_Command interpCmd;      /* Interpreter object command. */
    Tcl_HashTable aliasTable;   /* Table which maps from names of commands
                                 * in slave interpreter to struct Alias
                                 * defined below. */
} Slave;

/*
 * struct Target:
 *
 * Maps from master interpreter commands back to the source commands in slave
 * interpreters. This is needed because aliases can be created between sibling
 * interpreters and must be deleted when the target interpreter is deleted. In
 * case they would not be deleted the source interpreter would be left with a
 * "dangling pointer". One such record is stored in the Master record of the
 * master interpreter (in the targetTable hashtable, see below) with the
 * master for each alias which directs to a command in the master. These
 * records are used to remove the source command for an from a slave if/when
 * the master is deleted.
 */

typedef struct Target {
    Tcl_Command slaveCmd;       /* Command for alias in slave interp. */
    Tcl_Interp *slaveInterp;    /* Slave Interpreter. */
} Target;

/*
 * struct Master:
 *
 * This record is used for two purposes: First, slaveTable (a hashtable)
 * maps from names of commands to slave interpreters. This hashtable is
 * used to store information about slave interpreters of this interpreter,
 * to map over all slaves, etc. The second purpose is to store information
 * about all aliases in slaves (or siblings) which direct to target commands
 * in this interpreter (using the targetTable hashtable).
 * 
 * NB: the flags field in the interp structure, used with SAFE_INTERP
 * mask denotes whether the interpreter is safe or not. Safe
 * interpreters have restricted functionality, can only create safe slave
 * interpreters and can only load safe extensions.
 */

typedef struct Master {
    Tcl_HashTable slaveTable;   /* Hash table for slave interpreters.
                                 * Maps from command names to Slave records. */
    Tcl_HashTable targetTable;  /* Hash table for Target Records. Contains
                                 * all Target records which denote aliases
                                 * from slaves or sibling interpreters that
                                 * direct to commands in this interpreter. This
                                 * table is used to remove dangling pointers
                                 * from the slave (or sibling) interpreters
                                 * when this interpreter is deleted. */
} Master;

/*
 * The following structure keeps track of all the Master and Slave information
 * on a per-interp basis.
 */

typedef struct InterpInfo {
    Master master;              /* Keeps track of all interps for which this
                                 * interp is the Master. */
    Slave slave;                /* Information necessary for this interp to
                                 * function as a slave. */
} InterpInfo;

/*
 * Prototypes for local static procedures:
 */

static int              AliasCreate _ANSI_ARGS_((Tcl_Interp *interp,
                            Tcl_Interp *slaveInterp, Tcl_Interp *masterInterp,
                            Tcl_Obj *namePtr, Tcl_Obj *targetPtr, int objc,
                            Tcl_Obj *CONST objv[]));
static int              AliasDelete _ANSI_ARGS_((Tcl_Interp *interp,
                            Tcl_Interp *slaveInterp, Tcl_Obj *namePtr));
static int              AliasDescribe _ANSI_ARGS_((Tcl_Interp *interp,
                            Tcl_Interp *slaveInterp, Tcl_Obj *objPtr));
static int              AliasList _ANSI_ARGS_((Tcl_Interp *interp,
                            Tcl_Interp *slaveInterp));
static int              AliasObjCmd _ANSI_ARGS_((ClientData dummy,
                            Tcl_Interp *currentInterp, int objc,
                            Tcl_Obj *CONST objv[]));
static void             AliasObjCmdDeleteProc _ANSI_ARGS_((
                            ClientData clientData));

static Tcl_Interp *     GetInterp _ANSI_ARGS_((Tcl_Interp *interp,
                            Tcl_Obj *pathPtr));
static Tcl_Interp *     GetInterp2 _ANSI_ARGS_((Tcl_Interp *interp, int objc,
                            Tcl_Obj *CONST objv[]));
static void             InterpInfoDeleteProc _ANSI_ARGS_((
                            ClientData clientData, Tcl_Interp *interp));
static Tcl_Interp *     SlaveCreate _ANSI_ARGS_((Tcl_Interp *interp,
                            Tcl_Obj *pathPtr, int safe));
static int              SlaveEval _ANSI_ARGS_((Tcl_Interp *interp,
                            Tcl_Interp *slaveInterp, int objc,
                            Tcl_Obj *CONST objv[]));
static int              SlaveExpose _ANSI_ARGS_((Tcl_Interp *interp,
                            Tcl_Interp *slaveInterp, int objc,
                            Tcl_Obj *CONST objv[]));
static int              SlaveHide _ANSI_ARGS_((Tcl_Interp *interp,
                            Tcl_Interp *slaveInterp, int objc,
                            Tcl_Obj *CONST objv[]));
static int              SlaveHidden _ANSI_ARGS_((Tcl_Interp *interp,
                            Tcl_Interp *slaveInterp));
static int              SlaveInvokeHidden _ANSI_ARGS_((Tcl_Interp *interp,
                            Tcl_Interp *slaveInterp, int global, int objc,
                            Tcl_Obj *CONST objv[]));
static int              SlaveMarkTrusted _ANSI_ARGS_((Tcl_Interp *interp,
                            Tcl_Interp *slaveInterp));
static int              SlaveObjCmd _ANSI_ARGS_((ClientData dummy,
                            Tcl_Interp *interp, int objc,
                            Tcl_Obj *CONST objv[]));
static void             SlaveObjCmdDeleteProc _ANSI_ARGS_((
                            ClientData clientData));

/*
 *---------------------------------------------------------------------------
 *
 * TclInterpInit --
 *
 *      Initializes the invoking interpreter for using the master, slave
 *      and safe interp facilities.  This is called from inside
 *      Tcl_CreateInterp().
 *
 * Results:
 *      Always returns TCL_OK for backwards compatibility.
 *
 * Side effects:
 *      Adds the "interp" command to an interpreter and initializes the
 *      interpInfoPtr field of the invoking interpreter.
 *
 *---------------------------------------------------------------------------
 */

int
TclInterpInit(interp)
    Tcl_Interp *interp;                 /* Interpreter to initialize. */
{
    InterpInfo *interpInfoPtr;
    Master *masterPtr;
    Slave *slavePtr;    

    interpInfoPtr = (InterpInfo *) ckalloc(sizeof(InterpInfo));
    ((Interp *) interp)->interpInfo = (ClientData) interpInfoPtr;

    masterPtr = &interpInfoPtr->master;
    Tcl_InitHashTable(&masterPtr->slaveTable, TCL_STRING_KEYS);
    Tcl_InitHashTable(&masterPtr->targetTable, TCL_ONE_WORD_KEYS);

    slavePtr = &interpInfoPtr->slave;
    slavePtr->masterInterp      = NULL;
    slavePtr->slaveEntryPtr     = NULL;
    slavePtr->slaveInterp       = interp;
    slavePtr->interpCmd         = NULL;
    Tcl_InitHashTable(&slavePtr->aliasTable, TCL_STRING_KEYS);

    Tcl_CreateObjCommand(interp, "interp", Tcl_InterpObjCmd, NULL, NULL);

    Tcl_CallWhenDeleted(interp, InterpInfoDeleteProc, NULL);
    return TCL_OK;
}

/*
 *---------------------------------------------------------------------------
 *
 * InterpInfoDeleteProc --
 *
 *      Invoked when an interpreter is being deleted.  It releases all
 *      storage used by the master/slave/safe interpreter facilities.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Cleans up storage.  Sets the interpInfoPtr field of the interp
 *      to NULL.
 *
 *---------------------------------------------------------------------------
 */

static void
InterpInfoDeleteProc(clientData, interp)
    ClientData clientData;      /* Ignored. */
    Tcl_Interp *interp;         /* Interp being deleted.  All commands for
                                 * slave interps should already be deleted. */
{
    InterpInfo *interpInfoPtr;
    Slave *slavePtr;
    Master *masterPtr;
    Tcl_HashSearch hSearch;
    Tcl_HashEntry *hPtr;
    Target *targetPtr;

    interpInfoPtr = (InterpInfo *) ((Interp *) interp)->interpInfo;

    /*
     * There shouldn't be any commands left.
     */

    masterPtr = &interpInfoPtr->master;
    if (masterPtr->slaveTable.numEntries != 0) {
        panic("InterpInfoDeleteProc: still exist commands");
    }
    Tcl_DeleteHashTable(&masterPtr->slaveTable);

    /*
     * Tell any interps that have aliases to this interp that they should
     * delete those aliases.  If the other interp was already dead, it
     * would have removed the target record already. 
     */

    hPtr = Tcl_FirstHashEntry(&masterPtr->targetTable, &hSearch);
    while (hPtr != NULL) {
        targetPtr = (Target *) Tcl_GetHashValue(hPtr);
        Tcl_DeleteCommandFromToken(targetPtr->slaveInterp,
                targetPtr->slaveCmd);
        hPtr = Tcl_NextHashEntry(&hSearch);
    }
    Tcl_DeleteHashTable(&masterPtr->targetTable);

    slavePtr = &interpInfoPtr->slave;
    if (slavePtr->interpCmd != NULL) {
        /*
         * Tcl_DeleteInterp() was called on this interpreter, rather
         * "interp delete" or the equivalent deletion of the command in the
         * master.  First ensure that the cleanup callback doesn't try to
         * delete the interp again.
         */

        slavePtr->slaveInterp = NULL;
        Tcl_DeleteCommandFromToken(slavePtr->masterInterp,
                slavePtr->interpCmd);
    }

    /*
     * There shouldn't be any aliases left.
     */

    if (slavePtr->aliasTable.numEntries != 0) {
        panic("InterpInfoDeleteProc: still exist aliases");
    }
    Tcl_DeleteHashTable(&slavePtr->aliasTable);

    ckfree((char *) interpInfoPtr);    
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_InterpObjCmd --
 *
 *      This procedure is invoked to process the "interp" Tcl command.
 *      See the user documentation for details on what it does.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */
        /* ARGSUSED */
int
Tcl_InterpObjCmd(clientData, interp, objc, objv)
    ClientData clientData;              /* Unused. */
    Tcl_Interp *interp;                 /* Current interpreter. */
    int objc;                           /* Number of arguments. */
    Tcl_Obj *CONST objv[];              /* Argument objects. */
{
    int index;
    static char *options[] = {
        "alias",        "aliases",      "create",       "delete", 
        "eval",         "exists",       "expose",       "hide", 
        "hidden",       "issafe",       "invokehidden", "marktrusted", 
        "slaves",       "share",        "target",       "transfer",
        NULL
    };
    enum option {
        OPT_ALIAS,      OPT_ALIASES,    OPT_CREATE,     OPT_DELETE,
        OPT_EVAL,       OPT_EXISTS,     OPT_EXPOSE,     OPT_HIDE,
        OPT_HIDDEN,     OPT_ISSAFE,     OPT_INVOKEHID,  OPT_MARKTRUSTED,
        OPT_SLAVES,     OPT_SHARE,      OPT_TARGET,     OPT_TRANSFER
    };


    if (objc < 2) {
        Tcl_WrongNumArgs(interp, 1, objv, "cmd ?arg ...?");
        return TCL_ERROR;
    }
    if (Tcl_GetIndexFromObj(interp, objv[1], options, "option", 0, 
            &index) != TCL_OK) {
        return TCL_ERROR;
    }
    switch ((enum option) index) {
        case OPT_ALIAS: {
            Tcl_Interp *slaveInterp, *masterInterp;

            if (objc < 4) {
                aliasArgs:
                Tcl_WrongNumArgs(interp, 2, objv,
                        "slavePath slaveCmd ?masterPath masterCmd? ?args ..?");
                return TCL_ERROR;
            }
            slaveInterp = GetInterp(interp, objv[2]);
            if (slaveInterp == (Tcl_Interp *) NULL) {
                return TCL_ERROR;
            }
            if (objc == 4) {
                return AliasDescribe(interp, slaveInterp, objv[3]);
            }
            if ((objc == 5) && (Tcl_GetString(objv[4])[0] == '\0')) {
                return AliasDelete(interp, slaveInterp, objv[3]);
            }
            if (objc > 5) {
                masterInterp = GetInterp(interp, objv[4]);
                if (masterInterp == (Tcl_Interp *) NULL) {
                    return TCL_ERROR;
                }
                if (Tcl_GetString(objv[5])[0] == '\0') {
                    if (objc == 6) {
                        return AliasDelete(interp, slaveInterp, objv[3]);
                    }
                } else {
                    return AliasCreate(interp, slaveInterp, masterInterp,
                            objv[3], objv[5], objc - 6, objv + 6);
                }
            }
            goto aliasArgs;
        }
        case OPT_ALIASES: {
            Tcl_Interp *slaveInterp;

            slaveInterp = GetInterp2(interp, objc, objv);
            if (slaveInterp == NULL) {
                return TCL_ERROR;
            }
            return AliasList(interp, slaveInterp);
        }
        case OPT_CREATE: {
            int i, last, safe;
            Tcl_Obj *slavePtr;
            char buf[16 + TCL_INTEGER_SPACE];
            static char *options[] = {
                "-safe",        "--",           NULL
            };
            enum option {
                OPT_SAFE,       OPT_LAST
            };

            safe = Tcl_IsSafe(interp);
            
            /*
             * Weird historical rules: "-safe" is accepted at the end, too.
             */

            slavePtr = NULL;
            last = 0;
            for (i = 2; i < objc; i++) {
                if ((last == 0) && (Tcl_GetString(objv[i])[0] == '-')) {
                    if (Tcl_GetIndexFromObj(interp, objv[i], options, "option",
                            0, &index) != TCL_OK) {
                        return TCL_ERROR;
                    }
                    if (index == OPT_SAFE) {
                        safe = 1;
                        continue;
                    }
                    i++;
                    last = 1;
                }
                if (slavePtr != NULL) {
                    Tcl_WrongNumArgs(interp, 2, objv, "?-safe? ?--? ?path?");
                    return TCL_ERROR;
                }
                slavePtr = objv[i];
            }
            buf[0] = '\0';
            if (slavePtr == NULL) {
                /*
                 * Create an anonymous interpreter -- we choose its name and
                 * the name of the command. We check that the command name
                 * that we use for the interpreter does not collide with an
                 * existing command in the master interpreter.
                 */
                
                for (i = 0; ; i++) {
                    Tcl_CmdInfo cmdInfo;
                    
                    sprintf(buf, "interp%d", i);
                    if (Tcl_GetCommandInfo(interp, buf, &cmdInfo) == 0) {
                        break;
                    }
                }
                slavePtr = Tcl_NewStringObj(buf, -1);
            }
            if (SlaveCreate(interp, slavePtr, safe) == NULL) {
                if (buf[0] != '\0') {
                    Tcl_DecrRefCount(slavePtr);
                }
                return TCL_ERROR;
            }
            Tcl_SetObjResult(interp, slavePtr);
            return TCL_OK;
        }
        case OPT_DELETE: {
            int i;
            InterpInfo *iiPtr;
            Tcl_Interp *slaveInterp;
            
            for (i = 2; i < objc; i++) {
                slaveInterp = GetInterp(interp, objv[i]);
                if (slaveInterp == NULL) {
                    return TCL_ERROR;
                } else if (slaveInterp == interp) {
                    Tcl_ResetResult(interp);
                    Tcl_AppendStringsToObj(Tcl_GetObjResult(interp),
                            "cannot delete the current interpreter",
                            (char *) NULL);
                    return TCL_ERROR;
                }
                iiPtr = (InterpInfo *) ((Interp *) slaveInterp)->interpInfo;
                Tcl_DeleteCommandFromToken(iiPtr->slave.masterInterp,
                        iiPtr->slave.interpCmd);
            }
            return TCL_OK;
        }
        case OPT_EVAL: {
            Tcl_Interp *slaveInterp;

            if (objc < 4) {
                Tcl_WrongNumArgs(interp, 2, objv, "path arg ?arg ...?");
                return TCL_ERROR;
            }
            slaveInterp = GetInterp(interp, objv[2]);
            if (slaveInterp == NULL) {
                return TCL_ERROR;
            }
            return SlaveEval(interp, slaveInterp, objc - 3, objv + 3);
        }
        case OPT_EXISTS: {
            int exists;
            Tcl_Interp *slaveInterp;

            exists = 1;
            slaveInterp = GetInterp2(interp, objc, objv);
            if (slaveInterp == NULL) {
                if (objc > 3) {
                    return TCL_ERROR;
                }
                Tcl_ResetResult(interp);
                exists = 0;
            }
            Tcl_SetIntObj(Tcl_GetObjResult(interp), exists);
            return TCL_OK;
        }
        case OPT_EXPOSE: {
            Tcl_Interp *slaveInterp;

            if ((objc < 4) || (objc > 5)) {
                Tcl_WrongNumArgs(interp, 2, objv,
                        "path hiddenCmdName ?cmdName?");
                return TCL_ERROR;
            }
            slaveInterp = GetInterp(interp, objv[2]);
            if (slaveInterp == NULL) {
                return TCL_ERROR;
            }
            return SlaveExpose(interp, slaveInterp, objc - 3, objv + 3);
        }
        case OPT_HIDE: {
            Tcl_Interp *slaveInterp;            /* A slave. */

            if ((objc < 4) || (objc > 5)) {
                Tcl_WrongNumArgs(interp, 2, objv,
                        "path cmdName ?hiddenCmdName?");
                return TCL_ERROR;
            }
            slaveInterp = GetInterp(interp, objv[2]);
            if (slaveInterp == (Tcl_Interp *) NULL) {
                return TCL_ERROR;
            }
            return SlaveHide(interp, slaveInterp, objc - 3, objv + 3);
        }
        case OPT_HIDDEN: {
            Tcl_Interp *slaveInterp;            /* A slave. */

            slaveInterp = GetInterp2(interp, objc, objv);
            if (slaveInterp == NULL) {
                return TCL_ERROR;
            }
            return SlaveHidden(interp, slaveInterp);
        }
        case OPT_ISSAFE: {
            Tcl_Interp *slaveInterp;

            slaveInterp = GetInterp2(interp, objc, objv);
            if (slaveInterp == NULL) {
                return TCL_ERROR;
            }
            Tcl_SetIntObj(Tcl_GetObjResult(interp), Tcl_IsSafe(slaveInterp));
            return TCL_OK;
        }
        case OPT_INVOKEHID: {
            int i, index, global;
            Tcl_Interp *slaveInterp;
            static char *hiddenOptions[] = {
                "-global",      "--",           NULL
            };
            enum hiddenOption {
                OPT_GLOBAL,     OPT_LAST
            };

            global = 0;
            for (i = 3; i < objc; i++) {
                if (Tcl_GetString(objv[i])[0] != '-') {
                    break;
                }
                if (Tcl_GetIndexFromObj(interp, objv[i], hiddenOptions,
                        "option", 0, &index) != TCL_OK) {
                    return TCL_ERROR;
                }
                if (index == OPT_GLOBAL) {
                    global = 1;
                } else {
                    i++;
                    break;
                }
            }
            if (objc - i < 1) {
                Tcl_WrongNumArgs(interp, 2, objv,
                        "path ?-global? ?--? cmd ?arg ..?");
                return TCL_ERROR;
            }
            slaveInterp = GetInterp(interp, objv[2]);
            if (slaveInterp == (Tcl_Interp *) NULL) {
                return TCL_ERROR;
            }
            return SlaveInvokeHidden(interp, slaveInterp, global, objc - i,
                    objv + i);
        }
        case OPT_MARKTRUSTED: {
            Tcl_Interp *slaveInterp;

            if (objc != 3) {
                Tcl_WrongNumArgs(interp, 2, objv, "path");
                return TCL_ERROR;
            }
            slaveInterp = GetInterp(interp, objv[2]);
            if (slaveInterp == NULL) {
                return TCL_ERROR;
            }
            return SlaveMarkTrusted(interp, slaveInterp);
        }
        case OPT_SLAVES: {
            Tcl_Interp *slaveInterp;
            InterpInfo *iiPtr;
            Tcl_Obj *resultPtr;
            Tcl_HashEntry *hPtr;
            Tcl_HashSearch hashSearch;
            char *string;
            
            slaveInterp = GetInterp2(interp, objc, objv);
            if (slaveInterp == NULL) {
                return TCL_ERROR;
            }
            iiPtr = (InterpInfo *) ((Interp *) slaveInterp)->interpInfo;
            resultPtr = Tcl_GetObjResult(interp);
            hPtr = Tcl_FirstHashEntry(&iiPtr->master.slaveTable, &hashSearch);
            for ( ; hPtr != NULL; hPtr = Tcl_NextHashEntry(&hashSearch)) {
                string = Tcl_GetHashKey(&iiPtr->master.slaveTable, hPtr);
                Tcl_ListObjAppendElement(NULL, resultPtr,
                        Tcl_NewStringObj(string, -1));
            }
            return TCL_OK;
        }
        case OPT_SHARE: {
            Tcl_Interp *slaveInterp;            /* A slave. */
            Tcl_Interp *masterInterp;           /* Its master. */
            Tcl_Channel chan;

            if (objc != 5) {
                Tcl_WrongNumArgs(interp, 2, objv, "srcPath channelId destPath");
                return TCL_ERROR;
            }
            masterInterp = GetInterp(interp, objv[2]);
            if (masterInterp == NULL) {
                return TCL_ERROR;
            }
            chan = Tcl_GetChannel(masterInterp, Tcl_GetString(objv[3]),
                    NULL);
            if (chan == NULL) {
                TclTransferResult(masterInterp, TCL_OK, interp);
                return TCL_ERROR;
            }
            slaveInterp = GetInterp(interp, objv[4]);
            if (slaveInterp == NULL) {
                return TCL_ERROR;
            }
            Tcl_RegisterChannel(slaveInterp, chan);
            return TCL_OK;
        }
        case OPT_TARGET: {
            Tcl_Interp *slaveInterp;
            InterpInfo *iiPtr;
            Tcl_HashEntry *hPtr;        
            Alias *aliasPtr;            
            char *aliasName;

            if (objc != 4) {
                Tcl_WrongNumArgs(interp, 2, objv, "path alias");
                return TCL_ERROR;
            }

            slaveInterp = GetInterp(interp, objv[2]);
            if (slaveInterp == NULL) {
                return TCL_ERROR;
            }

            aliasName = Tcl_GetString(objv[3]);

            iiPtr = (InterpInfo *) ((Interp *) slaveInterp)->interpInfo;
            hPtr = Tcl_FindHashEntry(&iiPtr->slave.aliasTable, aliasName);
            if (hPtr == NULL) {
                Tcl_AppendStringsToObj(Tcl_GetObjResult(interp),
                        "alias \"", aliasName, "\" in path \"",
                        Tcl_GetString(objv[2]), "\" not found",
                        (char *) NULL);
                return TCL_ERROR;
            }
            aliasPtr = (Alias *) Tcl_GetHashValue(hPtr);
            if (Tcl_GetInterpPath(interp, aliasPtr->targetInterp) != TCL_OK) {
                Tcl_ResetResult(interp);
                Tcl_AppendStringsToObj(Tcl_GetObjResult(interp),
                        "target interpreter for alias \"", aliasName,
                        "\" in path \"", Tcl_GetString(objv[2]),
                        "\" is not my descendant", (char *) NULL);
                return TCL_ERROR;
            }
            return TCL_OK;
        }
        case OPT_TRANSFER: {
            Tcl_Interp *slaveInterp;            /* A slave. */
            Tcl_Interp *masterInterp;           /* Its master. */
            Tcl_Channel chan;
                    
            if (objc != 5) {
                Tcl_WrongNumArgs(interp, 2, objv,
                        "srcPath channelId destPath");
                return TCL_ERROR;
            }
            masterInterp = GetInterp(interp, objv[2]);
            if (masterInterp == NULL) {
                return TCL_ERROR;
            }
            chan = Tcl_GetChannel(masterInterp, Tcl_GetString(objv[3]), NULL);
            if (chan == NULL) {
                TclTransferResult(masterInterp, TCL_OK, interp);
                return TCL_ERROR;
            }
            slaveInterp = GetInterp(interp, objv[4]);
            if (slaveInterp == NULL) {
                return TCL_ERROR;
            }
            Tcl_RegisterChannel(slaveInterp, chan);
            if (Tcl_UnregisterChannel(masterInterp, chan) != TCL_OK) {
                TclTransferResult(masterInterp, TCL_OK, interp);
                return TCL_ERROR;
            }
            return TCL_OK;
        }
    }
    return TCL_OK;
}

/*
 *---------------------------------------------------------------------------
 *
 * GetInterp2 --
 *
 *      Helper function for Tcl_InterpObjCmd() to convert the interp name
 *      potentially specified on the command line to an Tcl_Interp.
 *
 * Results:
 *      The return value is the interp specified on the command line,
 *      or the interp argument itself if no interp was specified on the
 *      command line.  If the interp could not be found or the wrong
 *      number of arguments was specified on the command line, the return
 *      value is NULL and an error message is left in the interp's result.
 *
 * Side effects:
 *      None.
 *
 *---------------------------------------------------------------------------
 */
 
static Tcl_Interp *
GetInterp2(interp, objc, objv)
    Tcl_Interp *interp;         /* Default interp if no interp was specified
                                 * on the command line. */
    int objc;                   /* Number of arguments. */
    Tcl_Obj *CONST objv[];      /* Argument objects. */
{
    if (objc == 2) {
        return interp;
    } else if (objc == 3) {
        return GetInterp(interp, objv[2]);
    } else {
        Tcl_WrongNumArgs(interp, 2, objv, "?path?");
        return NULL;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_CreateAlias --
 *
 *      Creates an alias between two interpreters.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      Creates a new alias, manipulates the result field of slaveInterp.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_CreateAlias(slaveInterp, slaveCmd, targetInterp, targetCmd, argc, argv)
    Tcl_Interp *slaveInterp;    /* Interpreter for source command. */
    char *slaveCmd;             /* Command to install in slave. */
    Tcl_Interp *targetInterp;   /* Interpreter for target command. */
    char *targetCmd;            /* Name of target command. */
    int argc;                   /* How many additional arguments? */
    char **argv;                /* These are the additional args. */
{
    Tcl_Obj *slaveObjPtr, *targetObjPtr;
    Tcl_Obj **objv;
    int i;
    int result;
    
    objv = (Tcl_Obj **) ckalloc((unsigned) sizeof(Tcl_Obj *) * argc);
    for (i = 0; i < argc; i++) {
        objv[i] = Tcl_NewStringObj(argv[i], -1);
        Tcl_IncrRefCount(objv[i]);
    }
    
    slaveObjPtr = Tcl_NewStringObj(slaveCmd, -1);
    Tcl_IncrRefCount(slaveObjPtr);

    targetObjPtr = Tcl_NewStringObj(targetCmd, -1);
    Tcl_IncrRefCount(targetObjPtr);

    result = AliasCreate(slaveInterp, slaveInterp, targetInterp, slaveObjPtr,
            targetObjPtr, argc, objv);

    for (i = 0; i < argc; i++) {
        Tcl_DecrRefCount(objv[i]);
    }
    ckfree((char *) objv);
    Tcl_DecrRefCount(targetObjPtr);
    Tcl_DecrRefCount(slaveObjPtr);

    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_CreateAliasObj --
 *
 *      Object version: Creates an alias between two interpreters.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      Creates a new alias.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_CreateAliasObj(slaveInterp, slaveCmd, targetInterp, targetCmd, objc, objv)
    Tcl_Interp *slaveInterp;    /* Interpreter for source command. */
    char *slaveCmd;             /* Command to install in slave. */
    Tcl_Interp *targetInterp;   /* Interpreter for target command. */
    char *targetCmd;            /* Name of target command. */
    int objc;                   /* How many additional arguments? */
    Tcl_Obj *CONST objv[];      /* Argument vector. */
{
    Tcl_Obj *slaveObjPtr, *targetObjPtr;
    int result;

    slaveObjPtr = Tcl_NewStringObj(slaveCmd, -1);
    Tcl_IncrRefCount(slaveObjPtr);

    targetObjPtr = Tcl_NewStringObj(targetCmd, -1);
    Tcl_IncrRefCount(targetObjPtr);

    result = AliasCreate(slaveInterp, slaveInterp, targetInterp, slaveObjPtr,
            targetObjPtr, objc, objv);

    Tcl_DecrRefCount(slaveObjPtr);
    Tcl_DecrRefCount(targetObjPtr);
    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetAlias --
 *
 *      Gets information about an alias.
 *
 * Results:
 *      A standard Tcl result. 
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_GetAlias(interp, aliasName, targetInterpPtr, targetNamePtr, argcPtr,
        argvPtr)
    Tcl_Interp *interp;                 /* Interp to start search from. */
    char *aliasName;                    /* Name of alias to find. */
    Tcl_Interp **targetInterpPtr;       /* (Return) target interpreter. */
    char **targetNamePtr;               /* (Return) name of target command. */
    int *argcPtr;                       /* (Return) count of addnl args. */
    char ***argvPtr;                    /* (Return) additional arguments. */
{
    InterpInfo *iiPtr;
    Tcl_HashEntry *hPtr;
    Alias *aliasPtr;
    int i, objc;
    Tcl_Obj **objv;
    
    iiPtr = (InterpInfo *) ((Interp *) interp)->interpInfo;
    hPtr = Tcl_FindHashEntry(&iiPtr->slave.aliasTable, aliasName);
    if (hPtr == NULL) {
        Tcl_AppendStringsToObj(Tcl_GetObjResult(interp),
                "alias \"", aliasName, "\" not found", (char *) NULL);
        return TCL_ERROR;
    }
    aliasPtr = (Alias *) Tcl_GetHashValue(hPtr);
    Tcl_ListObjGetElements(NULL, aliasPtr->prefixPtr, &objc, &objv);

    if (targetInterpPtr != NULL) {
        *targetInterpPtr = aliasPtr->targetInterp;
    }
    if (targetNamePtr != NULL) {
        *targetNamePtr = Tcl_GetString(objv[0]);
    }
    if (argcPtr != NULL) {
        *argcPtr = objc - 1;
    }
    if (argvPtr != NULL) {
        *argvPtr = (char **) ckalloc((unsigned) sizeof(char *) * (objc - 1));
        for (i = 1; i < objc; i++) {
            *argvPtr[i - 1] = Tcl_GetString(objv[i]);
        }
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ObjGetAlias --
 *
 *      Object version: Gets information about an alias.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_GetAliasObj(interp, aliasName, targetInterpPtr, targetNamePtr, objcPtr,
        objvPtr)
    Tcl_Interp *interp;                 /* Interp to start search from. */
    char *aliasName;                    /* Name of alias to find. */
    Tcl_Interp **targetInterpPtr;       /* (Return) target interpreter. */
    char **targetNamePtr;               /* (Return) name of target command. */
    int *objcPtr;                       /* (Return) count of addnl args. */
    Tcl_Obj ***objvPtr;                 /* (Return) additional args. */
{
    InterpInfo *iiPtr;
    Tcl_HashEntry *hPtr;
    Alias *aliasPtr;    
    int objc;
    Tcl_Obj **objv;

    iiPtr = (InterpInfo *) ((Interp *) interp)->interpInfo;
    hPtr = Tcl_FindHashEntry(&iiPtr->slave.aliasTable, aliasName);
    if (hPtr == (Tcl_HashEntry *) NULL) {
        Tcl_AppendStringsToObj(Tcl_GetObjResult(interp),
                "alias \"", aliasName, "\" not found", (char *) NULL);
        return TCL_ERROR;
    }
    aliasPtr = (Alias *) Tcl_GetHashValue(hPtr);
    Tcl_ListObjGetElements(NULL, aliasPtr->prefixPtr, &objc, &objv);

    if (targetInterpPtr != (Tcl_Interp **) NULL) {
        *targetInterpPtr = aliasPtr->targetInterp;
    }
    if (targetNamePtr != (char **) NULL) {
        *targetNamePtr = Tcl_GetString(objv[0]);
    }
    if (objcPtr != (int *) NULL) {
        *objcPtr = objc - 1;
    }
    if (objvPtr != (Tcl_Obj ***) NULL) {
        *objvPtr = objv + 1;
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * TclPreventAliasLoop --
 *
 *      When defining an alias or renaming a command, prevent an alias
 *      loop from being formed.
 *
 * Results:
 *      A standard Tcl object result.
 *
 * Side effects:
 *      If TCL_ERROR is returned, the function also stores an error message
 *      in the interpreter's result object.
 *
 * NOTE:
 *      This function is public internal (instead of being static to
 *      this file) because it is also used from TclRenameCommand.
 *
 *----------------------------------------------------------------------
 */

int
TclPreventAliasLoop(interp, cmdInterp, cmd)
    Tcl_Interp *interp;                 /* Interp in which to report errors. */
    Tcl_Interp *cmdInterp;              /* Interp in which the command is
                                         * being defined. */
    Tcl_Command cmd;                    /* Tcl command we are attempting
                                         * to define. */
{
    Command *cmdPtr = (Command *) cmd;
    Alias *aliasPtr, *nextAliasPtr;
    Tcl_Command aliasCmd;
    Command *aliasCmdPtr;
    
    /*
     * If we are not creating or renaming an alias, then it is
     * always OK to create or rename the command.
     */
    
    if (cmdPtr->objProc != AliasObjCmd) {
        return TCL_OK;
    }

    /*
     * OK, we are dealing with an alias, so traverse the chain of aliases.
     * If we encounter the alias we are defining (or renaming to) any in
     * the chain then we have a loop.
     */

    aliasPtr = (Alias *) cmdPtr->objClientData;
    nextAliasPtr = aliasPtr;
    while (1) {
        int objc;
        Tcl_Obj **objv;

        /*
         * If the target of the next alias in the chain is the same as
         * the source alias, we have a loop.
         */

        Tcl_ListObjGetElements(NULL, nextAliasPtr->prefixPtr, &objc, &objv);
        aliasCmd = Tcl_FindCommand(nextAliasPtr->targetInterp,
                Tcl_GetString(objv[0]),
                Tcl_GetGlobalNamespace(nextAliasPtr->targetInterp),
                /*flags*/ 0);
        if (aliasCmd == (Tcl_Command) NULL) {
            return TCL_OK;
        }
        aliasCmdPtr = (Command *) aliasCmd;
        if (aliasCmdPtr == cmdPtr) {
            Tcl_AppendStringsToObj(Tcl_GetObjResult(interp),
                    "cannot define or rename alias \"",
                    Tcl_GetString(aliasPtr->namePtr),
                    "\": would create a loop", (char *) NULL);
            return TCL_ERROR;
        }

        /*
         * Otherwise, follow the chain one step further. See if the target
         * command is an alias - if so, follow the loop to its target
         * command. Otherwise we do not have a loop.
         */

        if (aliasCmdPtr->objProc != AliasObjCmd) {
            return TCL_OK;
        }
        nextAliasPtr = (Alias *) aliasCmdPtr->objClientData;
    }

    /* NOTREACHED */
}

/*
 *----------------------------------------------------------------------
 *
 * AliasCreate --
 *
 *      Helper function to do the work to actually create an alias.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      An alias command is created and entered into the alias table
 *      for the slave interpreter.
 *
 *----------------------------------------------------------------------
 */

static int
AliasCreate(interp, slaveInterp, masterInterp, namePtr, targetNamePtr,
        objc, objv)
    Tcl_Interp *interp;         /* Interp for error reporting. */
    Tcl_Interp *slaveInterp;    /* Interp where alias cmd will live or from
                                 * which alias will be deleted. */
    Tcl_Interp *masterInterp;   /* Interp in which target command will be
                                 * invoked. */
    Tcl_Obj *namePtr;           /* Name of alias cmd. */
    Tcl_Obj *targetNamePtr;     /* Name of target cmd. */
    int objc;                   /* Additional arguments to store */
    Tcl_Obj *CONST objv[];      /* with alias. */
{
    Alias *aliasPtr;
    Tcl_HashEntry *hPtr;
    int new;
    Target *targetPtr;
    Slave *slavePtr;
    Master *masterPtr;

    aliasPtr = (Alias *) ckalloc((unsigned) sizeof(Alias));
    aliasPtr->namePtr           = namePtr;
    Tcl_IncrRefCount(aliasPtr->namePtr);
    aliasPtr->targetInterp      = masterInterp;
    aliasPtr->prefixPtr         = Tcl_NewListObj(1, &targetNamePtr);
    Tcl_ListObjReplace(NULL, aliasPtr->prefixPtr, 1, 0, objc, objv);
    Tcl_IncrRefCount(aliasPtr->prefixPtr);

    aliasPtr->slaveCmd = Tcl_CreateObjCommand(slaveInterp,
            Tcl_GetString(namePtr), AliasObjCmd, (ClientData) aliasPtr,
            AliasObjCmdDeleteProc);

    if (TclPreventAliasLoop(interp, slaveInterp, aliasPtr->slaveCmd) != TCL_OK) {
        /*
         * Found an alias loop!  The last call to Tcl_CreateObjCommand made
         * the alias point to itself.  Delete the command and its alias
         * record.  Be careful to wipe out its client data first, so the
         * command doesn't try to delete itself.
         */

        Command *cmdPtr;
        
        Tcl_DecrRefCount(aliasPtr->namePtr);
        Tcl_DecrRefCount(aliasPtr->prefixPtr);
        
        cmdPtr = (Command *) aliasPtr->slaveCmd;
        cmdPtr->clientData = NULL;
        cmdPtr->deleteProc = NULL;
        cmdPtr->deleteData = NULL;
        Tcl_DeleteCommandFromToken(slaveInterp, aliasPtr->slaveCmd);

        ckfree((char *) aliasPtr);

        /*
         * The result was already set by TclPreventAliasLoop.
         */

        return TCL_ERROR;
    }
    
    /*
     * Make an entry in the alias table. If it already exists delete
     * the alias command. Then retry.
     */

    slavePtr = &((InterpInfo *) ((Interp *) slaveInterp)->interpInfo)->slave;
    while (1) {
        Alias *oldAliasPtr;
        char *string;
        
        string = Tcl_GetString(namePtr);
        hPtr = Tcl_CreateHashEntry(&slavePtr->aliasTable, string, &new);
        if (new != 0) {
            break;
        }

        oldAliasPtr = (Alias *) Tcl_GetHashValue(hPtr);
        Tcl_DeleteCommandFromToken(slaveInterp, oldAliasPtr->slaveCmd);
    }

    aliasPtr->aliasEntryPtr = hPtr;
    Tcl_SetHashValue(hPtr, (ClientData) aliasPtr);
    
    /*
     * Create the new command. We must do it after deleting any old command,
     * because the alias may be pointing at a renamed alias, as in:
     *
     * interp alias {} foo {} bar               # Create an alias "foo"
     * rename foo zop                           # Now rename the alias
     * interp alias {} foo {} zop               # Now recreate "foo"...
     */

    targetPtr = (Target *) ckalloc((unsigned) sizeof(Target));
    targetPtr->slaveCmd = aliasPtr->slaveCmd;
    targetPtr->slaveInterp = slaveInterp;

    Tcl_MutexLock(&cntMutex);
    masterPtr = &((InterpInfo *) ((Interp *) masterInterp)->interpInfo)->master;
    do {
        hPtr = Tcl_CreateHashEntry(&masterPtr->targetTable,
                (char *) aliasCounter, &new);
        aliasCounter++;
    } while (new == 0);
    Tcl_MutexUnlock(&cntMutex);

    Tcl_SetHashValue(hPtr, (ClientData) targetPtr);
    aliasPtr->targetEntryPtr = hPtr;

    Tcl_SetObjResult(interp, namePtr);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * AliasDelete --
 *
 *      Deletes the given alias from the slave interpreter given.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      Deletes the alias from the slave interpreter.
 *
 *----------------------------------------------------------------------
 */

static int
AliasDelete(interp, slaveInterp, namePtr)
    Tcl_Interp *interp;         /* Interpreter for result & errors. */
    Tcl_Interp *slaveInterp;    /* Interpreter containing alias. */
    Tcl_Obj *namePtr;           /* Name of alias to describe. */
{
    Slave *slavePtr;
    Alias *aliasPtr;
    Tcl_HashEntry *hPtr;

    /*
     * If the alias has been renamed in the slave, the master can still use
     * the original name (with which it was created) to find the alias to
     * delete it.
     */

    slavePtr = &((InterpInfo *) ((Interp *) slaveInterp)->interpInfo)->slave;
    hPtr = Tcl_FindHashEntry(&slavePtr->aliasTable, Tcl_GetString(namePtr));
    if (hPtr == NULL) {
        Tcl_AppendStringsToObj(Tcl_GetObjResult(interp), "alias \"",
                Tcl_GetString(namePtr), "\" not found", NULL);
        return TCL_ERROR;
    }
    aliasPtr = (Alias *) Tcl_GetHashValue(hPtr);
    Tcl_DeleteCommandFromToken(slaveInterp, aliasPtr->slaveCmd);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * AliasDescribe --
 *
 *      Sets the interpreter's result object to a Tcl list describing
 *      the given alias in the given interpreter: its target command
 *      and the additional arguments to prepend to any invocation
 *      of the alias.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

static int
AliasDescribe(interp, slaveInterp, namePtr)
    Tcl_Interp *interp;         /* Interpreter for result & errors. */
    Tcl_Interp *slaveInterp;    /* Interpreter containing alias. */
    Tcl_Obj *namePtr;           /* Name of alias to describe. */
{
    Slave *slavePtr;
    Tcl_HashEntry *hPtr;
    Alias *aliasPtr;    

    /*
     * If the alias has been renamed in the slave, the master can still use
     * the original name (with which it was created) to find the alias to
     * describe it.
     */

    slavePtr = &((InterpInfo *) ((Interp *) slaveInterp)->interpInfo)->slave;
    hPtr = Tcl_FindHashEntry(&slavePtr->aliasTable, Tcl_GetString(namePtr));
    if (hPtr == NULL) {
        return TCL_OK;
    }
    aliasPtr = (Alias *) Tcl_GetHashValue(hPtr);
    Tcl_SetObjResult(interp, aliasPtr->prefixPtr);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * AliasList --
 *
 *      Computes a list of aliases defined in a slave interpreter.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

static int
AliasList(interp, slaveInterp)
    Tcl_Interp *interp;         /* Interp for data return. */
    Tcl_Interp *slaveInterp;    /* Interp whose aliases to compute. */
{
    Tcl_HashEntry *entryPtr;
    Tcl_HashSearch hashSearch;
    Tcl_Obj *resultPtr; 
    Alias *aliasPtr;
    Slave *slavePtr;

    slavePtr = &((InterpInfo *) ((Interp *) slaveInterp)->interpInfo)->slave;
    resultPtr = Tcl_GetObjResult(interp);

    entryPtr = Tcl_FirstHashEntry(&slavePtr->aliasTable, &hashSearch);
    for ( ; entryPtr != NULL; entryPtr = Tcl_NextHashEntry(&hashSearch)) {
        aliasPtr = (Alias *) Tcl_GetHashValue(entryPtr);
        Tcl_ListObjAppendElement(NULL, resultPtr, aliasPtr->namePtr);
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * AliasObjCmd --
 *
 *      This is the procedure that services invocations of aliases in a
 *      slave interpreter. One such command exists for each alias. When
 *      invoked, this procedure redirects the invocation to the target
 *      command in the master interpreter as designated by the Alias
 *      record associated with this command.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      Causes forwarding of the invocation; all possible side effects
 *      may occur as a result of invoking the command to which the
 *      invocation is forwarded.
 *
 *----------------------------------------------------------------------
 */

static int
AliasObjCmd(clientData, interp, objc, objv)
    ClientData clientData;      /* Alias record. */
    Tcl_Interp *interp;         /* Current interpreter. */
    int objc;                   /* Number of arguments. */
    Tcl_Obj *CONST objv[];      /* Argument vector. */  
{
    Tcl_Interp *targetInterp;   
    Alias *aliasPtr;            
    int result, prefc, cmdc;
    Tcl_Obj *cmdPtr;
    Tcl_Obj **prefv, **cmdv;
    
    aliasPtr = (Alias *) clientData;
    targetInterp = aliasPtr->targetInterp;

    Tcl_Preserve((ClientData) targetInterp);

    ((Interp *) targetInterp)->numLevels++;

    Tcl_ResetResult(targetInterp);
    Tcl_AllowExceptions(targetInterp);

    /*
     * Append the arguments to the command prefix and invoke the command
     * in the target interp's global namespace.
     */
     
    Tcl_ListObjGetElements(NULL, aliasPtr->prefixPtr, &prefc, &prefv);
    cmdPtr = Tcl_NewListObj(prefc, prefv);
    Tcl_ListObjReplace(NULL, cmdPtr, prefc, 0, objc - 1, objv + 1);
    Tcl_ListObjGetElements(NULL, cmdPtr, &cmdc, &cmdv);
    result = TclObjInvoke(targetInterp, cmdc, cmdv,
            TCL_INVOKE_NO_TRACEBACK);
    Tcl_DecrRefCount(cmdPtr);

    ((Interp *) targetInterp)->numLevels--;
    
    /*
     * Check if we are at the bottom of the stack for the target interpreter.
     * If so, check for special return codes.
     */
    
    if (((Interp *) targetInterp)->numLevels == 0) {
        if (result == TCL_RETURN) {
            result = TclUpdateReturnInfo((Interp *) targetInterp);
        }
        if ((result != TCL_OK) && (result != TCL_ERROR)) {
            Tcl_ResetResult(targetInterp);
            if (result == TCL_BREAK) {
                Tcl_SetObjResult(targetInterp,
                        Tcl_NewStringObj("invoked \"break\" outside of a loop",
                                -1));
            } else if (result == TCL_CONTINUE) {
                Tcl_SetObjResult(targetInterp,
                        Tcl_NewStringObj(
                            "invoked \"continue\" outside of a loop",
                            -1));
            } else {
                char buf[32 + TCL_INTEGER_SPACE];

                sprintf(buf, "command returned bad code: %d", result);
                Tcl_SetObjResult(targetInterp, Tcl_NewStringObj(buf, -1));
            }
            result = TCL_ERROR;
        }
    }

    TclTransferResult(targetInterp, result, interp);

    Tcl_Release((ClientData) targetInterp);
    return result;        
}

/*
 *----------------------------------------------------------------------
 *
 * AliasObjCmdDeleteProc --
 *
 *      Is invoked when an alias command is deleted in a slave. Cleans up
 *      all storage associated with this alias.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Deletes the alias record and its entry in the alias table for
 *      the interpreter.
 *
 *----------------------------------------------------------------------
 */

static void
AliasObjCmdDeleteProc(clientData)
    ClientData clientData;      /* The alias record for this alias. */
{
    Alias *aliasPtr;            
    Target *targetPtr;          

    aliasPtr = (Alias *) clientData;
    
    Tcl_DecrRefCount(aliasPtr->namePtr);
    Tcl_DecrRefCount(aliasPtr->prefixPtr);
    Tcl_DeleteHashEntry(aliasPtr->aliasEntryPtr);

    targetPtr = (Target *) Tcl_GetHashValue(aliasPtr->targetEntryPtr);
    ckfree((char *) targetPtr);
    Tcl_DeleteHashEntry(aliasPtr->targetEntryPtr);

    ckfree((char *) aliasPtr);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_CreateSlave --
 *
 *      Creates a slave interpreter. The slavePath argument denotes the
 *      name of the new slave relative to the current interpreter; the
 *      slave is a direct descendant of the one-before-last component of
 *      the path, e.g. it is a descendant of the current interpreter if
 *      the slavePath argument contains only one component. Optionally makes
 *      the slave interpreter safe.
 *
 * Results:
 *      Returns the interpreter structure created, or NULL if an error
 *      occurred.
 *
 * Side effects:
 *      Creates a new interpreter and a new interpreter object command in
 *      the interpreter indicated by the slavePath argument.
 *
 *----------------------------------------------------------------------
 */

Tcl_Interp *
Tcl_CreateSlave(interp, slavePath, isSafe)
    Tcl_Interp *interp;         /* Interpreter to start search at. */
    char *slavePath;            /* Name of slave to create. */
    int isSafe;                 /* Should new slave be "safe" ? */
{
    Tcl_Obj *pathPtr;
    Tcl_Interp *slaveInterp;

    pathPtr = Tcl_NewStringObj(slavePath, -1);
    slaveInterp = SlaveCreate(interp, pathPtr, isSafe);
    Tcl_DecrRefCount(pathPtr);

    return slaveInterp;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetSlave --
 *
 *      Finds a slave interpreter by its path name.
 *
 * Results:
 *      Returns a Tcl_Interp * for the named interpreter or NULL if not
 *      found.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

Tcl_Interp *
Tcl_GetSlave(interp, slavePath)
    Tcl_Interp *interp;         /* Interpreter to start search from. */
    char *slavePath;            /* Path of slave to find. */
{
    Tcl_Obj *pathPtr;
    Tcl_Interp *slaveInterp;

    pathPtr = Tcl_NewStringObj(slavePath, -1);
    slaveInterp = GetInterp(interp, pathPtr);
    Tcl_DecrRefCount(pathPtr);

    return slaveInterp;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetMaster --
 *
 *      Finds the master interpreter of a slave interpreter.
 *
 * Results:
 *      Returns a Tcl_Interp * for the master interpreter or NULL if none.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

Tcl_Interp *
Tcl_GetMaster(interp)
    Tcl_Interp *interp;         /* Get the master of this interpreter. */
{
    Slave *slavePtr;            /* Slave record of this interpreter. */

    if (interp == (Tcl_Interp *) NULL) {
        return NULL;
    }
    slavePtr = &((InterpInfo *) ((Interp *) interp)->interpInfo)->slave;
    return slavePtr->masterInterp;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetInterpPath --
 *
 *      Sets the result of the asking interpreter to a proper Tcl list
 *      containing the names of interpreters between the asking and
 *      target interpreters. The target interpreter must be either the
 *      same as the asking interpreter or one of its slaves (including
 *      recursively).
 *
 * Results:
 *      TCL_OK if the target interpreter is the same as, or a descendant
 *      of, the asking interpreter; TCL_ERROR else. This way one can
 *      distinguish between the case where the asking and target interps
 *      are the same (an empty list is the result, and TCL_OK is returned)
 *      and when the target is not a descendant of the asking interpreter
 *      (in which case the Tcl result is an error message and the function
 *      returns TCL_ERROR).
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_GetInterpPath(askingInterp, targetInterp)
    Tcl_Interp *askingInterp;   /* Interpreter to start search from. */
    Tcl_Interp *targetInterp;   /* Interpreter to find. */
{
    InterpInfo *iiPtr;
    
    if (targetInterp == askingInterp) {
        return TCL_OK;
    }
    if (targetInterp == NULL) {
        return TCL_ERROR;
    }
    iiPtr = (InterpInfo *) ((Interp *) targetInterp)->interpInfo;
    if (Tcl_GetInterpPath(askingInterp, iiPtr->slave.masterInterp) != TCL_OK) {
        return TCL_ERROR;
    }
    Tcl_AppendElement(askingInterp,
            Tcl_GetHashKey(&iiPtr->master.slaveTable,
                    iiPtr->slave.slaveEntryPtr));
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * GetInterp --
 *
 *      Helper function to find a slave interpreter given a pathname.
 *
 * Results:
 *      Returns the slave interpreter known by that name in the calling
 *      interpreter, or NULL if no interpreter known by that name exists. 
 *
 * Side effects:
 *      Assigns to the pointer variable passed in, if not NULL.
 *
 *----------------------------------------------------------------------
 */

static Tcl_Interp *
GetInterp(interp, pathPtr)
    Tcl_Interp *interp;         /* Interp. to start search from. */
    Tcl_Obj *pathPtr;           /* List object containing name of interp. to 
                                 * be found. */
{
    Tcl_HashEntry *hPtr;        /* Search element. */
    Slave *slavePtr;            /* Interim slave record. */
    Tcl_Obj **objv;
    int objc, i;        
    Tcl_Interp *searchInterp;   /* Interim storage for interp. to find. */
    InterpInfo *masterInfoPtr;

    if (Tcl_ListObjGetElements(interp, pathPtr, &objc, &objv) != TCL_OK) {
        return NULL;
    }

    searchInterp = interp;
    for (i = 0; i < objc; i++) {
        masterInfoPtr = (InterpInfo *) ((Interp *) searchInterp)->interpInfo;
        hPtr = Tcl_FindHashEntry(&masterInfoPtr->master.slaveTable,
                Tcl_GetString(objv[i]));
        if (hPtr == NULL) {
            searchInterp = NULL;
            break;
        }
        slavePtr = (Slave *) Tcl_GetHashValue(hPtr);
        searchInterp = slavePtr->slaveInterp;
        if (searchInterp == NULL) {
            break;
        }
    }
    if (searchInterp == NULL) {
        Tcl_AppendStringsToObj(Tcl_GetObjResult(interp),
                "could not find interpreter \"",
                Tcl_GetString(pathPtr), "\"", (char *) NULL);
    }
    return searchInterp;
}

/*
 *----------------------------------------------------------------------
 *
 * SlaveCreate --
 *
 *      Helper function to do the actual work of creating a slave interp
 *      and new object command. Also optionally makes the new slave
 *      interpreter "safe".
 *
 * Results:
 *      Returns the new Tcl_Interp * if successful or NULL if not. If failed,
 *      the result of the invoking interpreter contains an error message.
 *
 * Side effects:
 *      Creates a new slave interpreter and a new object command.
 *
 *----------------------------------------------------------------------
 */

static Tcl_Interp *
SlaveCreate(interp, pathPtr, safe)
    Tcl_Interp *interp;         /* Interp. to start search from. */
    Tcl_Obj *pathPtr;           /* Path (name) of slave to create. */
    int safe;                   /* Should we make it "safe"? */
{
    Tcl_Interp *masterInterp, *slaveInterp;
    Slave *slavePtr;
    InterpInfo *masterInfoPtr;
    Tcl_HashEntry *hPtr;
    char *path;
    int new, objc;
    Tcl_Obj **objv;

    if (Tcl_ListObjGetElements(interp, pathPtr, &objc, &objv) != TCL_OK) {
        return NULL;
    }
    if (objc < 2) {
        masterInterp = interp;
        path = Tcl_GetString(pathPtr);
    } else {
        Tcl_Obj *objPtr;
        
        objPtr = Tcl_NewListObj(objc - 1, objv);
        masterInterp = GetInterp(interp, objPtr);
        Tcl_DecrRefCount(objPtr);
        if (masterInterp == NULL) {
            return NULL;
        }
        path = Tcl_GetString(objv[objc - 1]);
    }
    if (safe == 0) {
        safe = Tcl_IsSafe(masterInterp);
    }

    masterInfoPtr = (InterpInfo *) ((Interp *) masterInterp)->interpInfo;
    hPtr = Tcl_CreateHashEntry(&masterInfoPtr->master.slaveTable, path, &new);
    if (new == 0) {
        Tcl_AppendStringsToObj(Tcl_GetObjResult(interp),
                "interpreter named \"", path,
                "\" already exists, cannot create", (char *) NULL);
        return NULL;
    }

    slaveInterp = Tcl_CreateInterp();
    slavePtr = &((InterpInfo *) ((Interp *) slaveInterp)->interpInfo)->slave;
    slavePtr->masterInterp = masterInterp;
    slavePtr->slaveEntryPtr = hPtr;
    slavePtr->slaveInterp = slaveInterp;
    slavePtr->interpCmd = Tcl_CreateObjCommand(masterInterp, path,
            SlaveObjCmd, (ClientData) slaveInterp, SlaveObjCmdDeleteProc);
    Tcl_InitHashTable(&slavePtr->aliasTable, TCL_STRING_KEYS);
    Tcl_SetHashValue(hPtr, (ClientData) slavePtr);
    Tcl_SetVar(slaveInterp, "tcl_interactive", "0", TCL_GLOBAL_ONLY);
    
    /*
     * Inherit the recursion limit.
     */
    ((Interp *) slaveInterp)->maxNestingDepth =
        ((Interp *) masterInterp)->maxNestingDepth ;

    if (safe) {
        if (Tcl_MakeSafe(slaveInterp) == TCL_ERROR) {
            goto error;
        }
    } else {
        if (Tcl_Init(slaveInterp) == TCL_ERROR) {
            goto error;
        }
    }
    return slaveInterp;

    error:
    TclTransferResult(slaveInterp, TCL_ERROR, interp);
    Tcl_DeleteInterp(slaveInterp);

    return NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * SlaveObjCmd --
 *
 *      Command to manipulate an interpreter, e.g. to send commands to it
 *      to be evaluated. One such command exists for each slave interpreter.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      See user documentation for details.
 *
 *----------------------------------------------------------------------
 */

static int
SlaveObjCmd(clientData, interp, objc, objv)
    ClientData clientData;      /* Slave interpreter. */
    Tcl_Interp *interp;         /* Current interpreter. */
    int objc;                   /* Number of arguments. */
    Tcl_Obj *CONST objv[];      /* Argument objects. */
{
    Tcl_Interp *slaveInterp;
    int index;
    static char *options[] = {
        "alias",        "aliases",      "eval",         "expose",
        "hide",         "hidden",       "issafe",       "invokehidden",
        "marktrusted",  NULL
    };
    enum options {
        OPT_ALIAS,      OPT_ALIASES,    OPT_EVAL,       OPT_EXPOSE,
        OPT_HIDE,       OPT_HIDDEN,     OPT_ISSAFE,     OPT_INVOKEHIDDEN,
        OPT_MARKTRUSTED
    };
    
    slaveInterp = (Tcl_Interp *) clientData;
    if (slaveInterp == NULL) {
        panic("SlaveObjCmd: interpreter has been deleted");
    }

    if (objc < 2) {
        Tcl_WrongNumArgs(interp, 1, objv, "cmd ?arg ...?");
        return TCL_ERROR;
    }
    if (Tcl_GetIndexFromObj(interp, objv[1], options, "option", 0,
            &index) != TCL_OK) {
        return TCL_ERROR;
    }

    switch ((enum options) index) {
        case OPT_ALIAS: {
            if (objc == 3) {
                return AliasDescribe(interp, slaveInterp, objv[2]);
            }
            if (Tcl_GetString(objv[3])[0] == '\0') {
                if (objc == 4) {
                    return AliasDelete(interp, slaveInterp, objv[2]);
                }
            } else {
                return AliasCreate(interp, slaveInterp, interp, objv[2],
                        objv[3], objc - 4, objv + 4);
            }
            Tcl_WrongNumArgs(interp, 2, objv,
                    "aliasName ?targetName? ?args..?");
            return TCL_ERROR;
        }
        case OPT_ALIASES: {
            return AliasList(interp, slaveInterp);
        }
        case OPT_EVAL: {
            if (objc < 3) {
                Tcl_WrongNumArgs(interp, 2, objv, "arg ?arg ...?");
                return TCL_ERROR;
            }
            return SlaveEval(interp, slaveInterp, objc - 2, objv + 2);
        }
        case OPT_EXPOSE: {
            if ((objc < 3) || (objc > 4)) {
                Tcl_WrongNumArgs(interp, 2, objv, "hiddenCmdName ?cmdName?");
                return TCL_ERROR;
            }
            return SlaveExpose(interp, slaveInterp, objc - 2, objv + 2);
        }
        case OPT_HIDE: {
            if ((objc < 3) || (objc > 4)) {
                Tcl_WrongNumArgs(interp, 2, objv, "cmdName ?hiddenCmdName?");
                return TCL_ERROR;
            }
            return SlaveHide(interp, slaveInterp, objc - 2, objv + 2);
        }
        case OPT_HIDDEN: {
            if (objc != 2) {
                Tcl_WrongNumArgs(interp, 2, objv, NULL);
                return TCL_ERROR;
            }
            return SlaveHidden(interp, slaveInterp);
        }
        case OPT_ISSAFE: {
            Tcl_SetIntObj(Tcl_GetObjResult(interp), Tcl_IsSafe(slaveInterp));
            return TCL_OK;
        }
        case OPT_INVOKEHIDDEN: {
            int global, i, index;
            static char *hiddenOptions[] = {
                "-global",      "--",           NULL
            };
            enum hiddenOption {
                OPT_GLOBAL,     OPT_LAST
            };
            global = 0;
            for (i = 2; i < objc; i++) {
                if (Tcl_GetString(objv[i])[0] != '-') {
                    break;
                }
                if (Tcl_GetIndexFromObj(interp, objv[i], hiddenOptions,
                        "option", 0, &index) != TCL_OK) {
                    return TCL_ERROR;
                }
                if (index == OPT_GLOBAL) {
                    global = 1;
                } else {
                    i++;
                    break;
                }
            }
            if (objc - i < 1) {
                Tcl_WrongNumArgs(interp, 2, objv,
                        "?-global? ?--? cmd ?arg ..?");
                return TCL_ERROR;
            }
            return SlaveInvokeHidden(interp, slaveInterp, global, objc - i,
                    objv + i);
        }
        case OPT_MARKTRUSTED: {
            if (objc != 2) {
                Tcl_WrongNumArgs(interp, 2, objv, NULL);
                return TCL_ERROR;
            }
            return SlaveMarkTrusted(interp, slaveInterp);
        }
    }

    return TCL_ERROR;
}

/*
 *----------------------------------------------------------------------
 *
 * SlaveObjCmdDeleteProc --
 *
 *      Invoked when an object command for a slave interpreter is deleted;
 *      cleans up all state associated with the slave interpreter and destroys
 *      the slave interpreter.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Cleans up all state associated with the slave interpreter and
 *      destroys the slave interpreter.
 *
 *----------------------------------------------------------------------
 */

static void
SlaveObjCmdDeleteProc(clientData)
    ClientData clientData;              /* The SlaveRecord for the command. */
{
    Slave *slavePtr;                    /* Interim storage for Slave record. */
    Tcl_Interp *slaveInterp;            /* And for a slave interp. */

    slaveInterp = (Tcl_Interp *) clientData;
    slavePtr = &((InterpInfo *) ((Interp *) slaveInterp)->interpInfo)->slave;

    /*
     * Unlink the slave from its master interpreter.
     */

    Tcl_DeleteHashEntry(slavePtr->slaveEntryPtr);

    /*
     * Set to NULL so that when the InterpInfo is cleaned up in the slave
     * it does not try to delete the command causing all sorts of grief.
     * See SlaveRecordDeleteProc().
     */

    slavePtr->interpCmd = NULL;

    if (slavePtr->slaveInterp != NULL) {
        Tcl_DeleteInterp(slavePtr->slaveInterp);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * SlaveEval --
 *
 *      Helper function to evaluate a command in a slave interpreter.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      Whatever the command does.
 *
 *----------------------------------------------------------------------
 */

static int
SlaveEval(interp, slaveInterp, objc, objv)
    Tcl_Interp *interp;         /* Interp for error return. */
    Tcl_Interp *slaveInterp;    /* The slave interpreter in which command
                                 * will be evaluated. */
    int objc;                   /* Number of arguments. */
    Tcl_Obj *CONST objv[];      /* Argument objects. */
{
    int result;
    Tcl_Obj *objPtr;
    
    Tcl_Preserve((ClientData) slaveInterp);
    Tcl_AllowExceptions(slaveInterp);

    if (objc == 1) {
        result = Tcl_EvalObjEx(slaveInterp, objv[0], 0);
    } else {
        objPtr = Tcl_ConcatObj(objc, objv);
        Tcl_IncrRefCount(objPtr);
        result = Tcl_EvalObjEx(slaveInterp, objPtr, 0);
        Tcl_DecrRefCount(objPtr);
    }
    TclTransferResult(slaveInterp, result, interp);

    Tcl_Release((ClientData) slaveInterp);
    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * SlaveExpose --
 *
 *      Helper function to expose a command in a slave interpreter.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      After this call scripts in the slave will be able to invoke
 *      the newly exposed command.
 *
 *----------------------------------------------------------------------
 */

static int
SlaveExpose(interp, slaveInterp, objc, objv)
    Tcl_Interp *interp;         /* Interp for error return. */
    Tcl_Interp  *slaveInterp;   /* Interp in which command will be exposed. */
    int objc;                   /* Number of arguments. */
    Tcl_Obj *CONST objv[];      /* Argument strings. */
{
    char *name;
    
    if (Tcl_IsSafe(interp)) {
        Tcl_AppendStringsToObj(Tcl_GetObjResult(interp),
                "permission denied: safe interpreter cannot expose commands",
                (char *) NULL);
        return TCL_ERROR;
    }

    name = Tcl_GetString(objv[(objc == 1) ? 0 : 1]);
    if (Tcl_ExposeCommand(slaveInterp, Tcl_GetString(objv[0]),
            name) != TCL_OK) {
        TclTransferResult(slaveInterp, TCL_ERROR, interp);
        return TCL_ERROR;
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * SlaveHide --
 *
 *      Helper function to hide a command in a slave interpreter.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      After this call scripts in the slave will no longer be able
 *      to invoke the named command.
 *
 *----------------------------------------------------------------------
 */

static int
SlaveHide(interp, slaveInterp, objc, objv)
    Tcl_Interp *interp;         /* Interp for error return. */
    Tcl_Interp  *slaveInterp;   /* Interp in which command will be exposed. */
    int objc;                   /* Number of arguments. */
    Tcl_Obj *CONST objv[];      /* Argument strings. */
{
    char *name;
    
    if (Tcl_IsSafe(interp)) {
        Tcl_AppendStringsToObj(Tcl_GetObjResult(interp),
                "permission denied: safe interpreter cannot hide commands",
                (char *) NULL);
        return TCL_ERROR;
    }

    name = Tcl_GetString(objv[(objc == 1) ? 0 : 1]);
    if (Tcl_HideCommand(slaveInterp, Tcl_GetString(objv[0]),
            name) != TCL_OK) {
        TclTransferResult(slaveInterp, TCL_ERROR, interp);
        return TCL_ERROR;
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * SlaveHidden --
 *
 *      Helper function to compute list of hidden commands in a slave
 *      interpreter.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

static int
SlaveHidden(interp, slaveInterp)
    Tcl_Interp *interp;         /* Interp for data return. */
    Tcl_Interp *slaveInterp;    /* Interp whose hidden commands to query. */
{
    Tcl_Obj *listObjPtr;                /* Local object pointer. */
    Tcl_HashTable *hTblPtr;             /* For local searches. */
    Tcl_HashEntry *hPtr;                /* For local searches. */
    Tcl_HashSearch hSearch;             /* For local searches. */
    
    listObjPtr = Tcl_GetObjResult(interp);
    hTblPtr = ((Interp *) slaveInterp)->hiddenCmdTablePtr;
    if (hTblPtr != (Tcl_HashTable *) NULL) {
        for (hPtr = Tcl_FirstHashEntry(hTblPtr, &hSearch);
             hPtr != (Tcl_HashEntry *) NULL;
             hPtr = Tcl_NextHashEntry(&hSearch)) {

            Tcl_ListObjAppendElement(NULL, listObjPtr,
                    Tcl_NewStringObj(Tcl_GetHashKey(hTblPtr, hPtr), -1));
        }
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * SlaveInvokeHidden --
 *
 *      Helper function to invoke a hidden command in a slave interpreter.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      Whatever the hidden command does.
 *
 *----------------------------------------------------------------------
 */

static int
SlaveInvokeHidden(interp, slaveInterp, global, objc, objv)
    Tcl_Interp *interp;         /* Interp for error return. */
    Tcl_Interp *slaveInterp;    /* The slave interpreter in which command
                                 * will be invoked. */
    int global;                 /* Non-zero to invoke in global namespace. */
    int objc;                   /* Number of arguments. */
    Tcl_Obj *CONST objv[];      /* Argument objects. */
{
    int result;
    
    if (Tcl_IsSafe(interp)) {
        Tcl_SetStringObj(Tcl_GetObjResult(interp),
                "not allowed to invoke hidden commands from safe interpreter",
                -1);
        return TCL_ERROR;
    }

    Tcl_Preserve((ClientData) slaveInterp);
    Tcl_AllowExceptions(slaveInterp);
    
    if (global) {
        result = TclObjInvokeGlobal(slaveInterp, objc, objv,
                TCL_INVOKE_HIDDEN);
    } else {
        result = TclObjInvoke(slaveInterp, objc, objv, TCL_INVOKE_HIDDEN);
    }

    TclTransferResult(slaveInterp, result, interp);

    Tcl_Release((ClientData) slaveInterp);
    return result;        
}

/*
 *----------------------------------------------------------------------
 *
 * SlaveMarkTrusted --
 *
 *      Helper function to mark a slave interpreter as trusted (unsafe).
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      After this call the hard-wired security checks in the core no
 *      longer prevent the slave from performing certain operations.
 *
 *----------------------------------------------------------------------
 */

static int
SlaveMarkTrusted(interp, slaveInterp)
    Tcl_Interp *interp;         /* Interp for error return. */
    Tcl_Interp *slaveInterp;    /* The slave interpreter which will be
                                 * marked trusted. */
{
    if (Tcl_IsSafe(interp)) {
        Tcl_AppendStringsToObj(Tcl_GetObjResult(interp),
                "permission denied: safe interpreter cannot mark trusted",
                (char *) NULL);
        return TCL_ERROR;
    }
    ((Interp *) slaveInterp)->flags &= ~SAFE_INTERP;
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_IsSafe --
 *
 *      Determines whether an interpreter is safe
 *
 * Results:
 *      1 if it is safe, 0 if it is not.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_IsSafe(interp)
    Tcl_Interp *interp;         /* Is this interpreter "safe" ? */
{
    Interp *iPtr;

    if (interp == (Tcl_Interp *) NULL) {
        return 0;
    }
    iPtr = (Interp *) interp;

    return ( (iPtr->flags) & SAFE_INTERP ) ? 1 : 0 ;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_MakeSafe --
 *
 *      Makes its argument interpreter contain only functionality that is
 *      defined to be part of Safe Tcl. Unsafe commands are hidden, the
 *      env array is unset, and the standard channels are removed.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Hides commands in its argument interpreter, and removes settings
 *      and channels.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_MakeSafe(interp)
    Tcl_Interp *interp;         /* Interpreter to be made safe. */
{
    Tcl_Channel chan;                           /* Channel to remove from
                                                 * safe interpreter. */
    Interp *iPtr = (Interp *) interp;

    TclHideUnsafeCommands(interp);
    
    iPtr->flags |= SAFE_INTERP;

    /*
     *  Unsetting variables : (which should not have been set 
     *  in the first place, but...)
     */

    /*
     * No env array in a safe slave.
     */

    Tcl_UnsetVar(interp, "env", TCL_GLOBAL_ONLY);

    /* 
     * Remove unsafe parts of tcl_platform
     */

    Tcl_UnsetVar2(interp, "tcl_platform", "os", TCL_GLOBAL_ONLY);
    Tcl_UnsetVar2(interp, "tcl_platform", "osVersion", TCL_GLOBAL_ONLY);
    Tcl_UnsetVar2(interp, "tcl_platform", "machine", TCL_GLOBAL_ONLY);
    Tcl_UnsetVar2(interp, "tcl_platform", "user", TCL_GLOBAL_ONLY);

    /*
     * Unset path informations variables
     * (the only one remaining is [info nameofexecutable])
     */

    Tcl_UnsetVar(interp, "tclDefaultLibrary", TCL_GLOBAL_ONLY);
    Tcl_UnsetVar(interp, "tcl_library", TCL_GLOBAL_ONLY);
    Tcl_UnsetVar(interp, "tcl_pkgPath", TCL_GLOBAL_ONLY);
    
    /*
     * Remove the standard channels from the interpreter; safe interpreters
     * do not ordinarily have access to stdin, stdout and stderr.
     *
     * NOTE: These channels are not added to the interpreter by the
     * Tcl_CreateInterp call, but may be added later, by another I/O
     * operation. We want to ensure that the interpreter does not have
     * these channels even if it is being made safe after being used for
     * some time..
     */

    chan = Tcl_GetStdChannel(TCL_STDIN);
    if (chan != (Tcl_Channel) NULL) {
        Tcl_UnregisterChannel(interp, chan);
    }
    chan = Tcl_GetStdChannel(TCL_STDOUT);
    if (chan != (Tcl_Channel) NULL) {
        Tcl_UnregisterChannel(interp, chan);
    }
    chan = Tcl_GetStdChannel(TCL_STDERR);
    if (chan != (Tcl_Channel) NULL) {
        Tcl_UnregisterChannel(interp, chan);
    }

    return TCL_OK;
}

/* End of tclinterp.c */