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/*
 * tclNamesp.c --
 *
 *	Contains support for namespaces, which provide a separate context of
 *	commands and global variables. The global :: namespace is the
 *	traditional Tcl "global" scope. Other namespaces are created as
 *	children of the global namespace. These other namespaces contain
 *	special-purpose commands and variables for packages. Also includes the
 *	TIP#112 ensemble machinery.
 *
 * Copyright (c) 1993-1997 Lucent Technologies.
 * Copyright (c) 1997 Sun Microsystems, Inc.
 * Copyright (c) 1998-1999 by Scriptics Corporation.
 * Copyright (c) 2002-2005 Donal K. Fellows.
 * Copyright (c) 2006 Neil Madden.
 * Contributions from Don Porter, NIST, 2007. (not subject to US copyright)
 *
 * Originally implemented by
 *   Michael J. McLennan
 *   Bell Labs Innovations for Lucent Technologies
 *   mmclennan@lucent.com
 *
 * See the file "license.terms" for information on usage and redistribution of
 * this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclNamesp.c,v 1.164 2008/05/22 15:22:07 dgp Exp $
 */

#include "tclInt.h"

/*
 * Thread-local storage used to avoid having a global lock on data that is not
 * limited to a single interpreter.
 */

typedef struct ThreadSpecificData {
    long numNsCreated;		/* Count of the number of namespaces created
				 * within the thread. This value is used as a
				 * unique id for each namespace. Cannot be
				 * per-interp because the nsId is used to
				 * distinguish objects which can be passed
				 * around between interps in the same thread,
				 * but does not need to be global because
				 * object internal reps are always per-thread
				 * anyway. */
} ThreadSpecificData;

static Tcl_ThreadDataKey dataKey;

/*
 * This structure contains a cached pointer to a namespace that is the result
 * of resolving the namespace's name in some other namespace. It is the
 * internal representation for a nsName object. It contains the pointer along
 * with some information that is used to check the cached pointer's validity.
 */

typedef struct ResolvedNsName {
    Namespace *nsPtr;          /* A cached pointer to the Namespace that the
                                * name resolved to. */
    Namespace *refNsPtr;       /* Points to the namespace context in which the
                                * name was resolved. NULL if the name is fully
                                * qualified and thus the resolution does not
                                * depend on the context. */
    int refCount;		/* Reference count: 1 for each nsName object
				 * that has a pointer to this ResolvedNsName
				 * structure as its internal rep. This
				 * structure can be freed when refCount
				 * becomes zero. */
} ResolvedNsName;

/*
 * The client data for an ensemble command. This consists of the table of
 * commands that are actually exported by the namespace, and an epoch counter
 * that, combined with the exportLookupEpoch field of the namespace structure,
 * defines whether the table contains valid data or will need to be recomputed
 * next time the ensemble command is called.
 */

typedef struct EnsembleConfig {
    Namespace *nsPtr;		/* The namspace backing this ensemble up. */
    Tcl_Command token;		/* The token for the command that provides
				 * ensemble support for the namespace, or NULL
				 * if the command has been deleted (or never
				 * existed; the global namespace never has an
				 * ensemble command.) */
    int epoch;			/* The epoch at which this ensemble's table of
				 * exported commands is valid. */
    char **subcommandArrayPtr;	/* Array of ensemble subcommand names. At all
				 * consistent points, this will have the same
				 * number of entries as there are entries in
				 * the subcommandTable hash. */
    Tcl_HashTable subcommandTable;
				/* Hash table of ensemble subcommand names,
				 * which are its keys so this also provides
				 * the storage management for those subcommand
				 * names. The contents of the entry values are
				 * object version the prefix lists to use when
				 * substituting for the command/subcommand to
				 * build the ensemble implementation command.
				 * Has to be stored here as well as in
				 * subcommandDict because that field is NULL
				 * when we are deriving the ensemble from the
				 * namespace exports list. FUTURE WORK: use
				 * object hash table here. */
    struct EnsembleConfig *next;/* The next ensemble in the linked list of
				 * ensembles associated with a namespace. If
				 * this field points to this ensemble, the
				 * structure has already been unlinked from
				 * all lists, and cannot be found by scanning
				 * the list from the namespace's ensemble
				 * field. */
    int flags;			/* ORed combo of TCL_ENSEMBLE_PREFIX, ENS_DEAD
				 * and ENSEMBLE_COMPILE. */

    /* OBJECT FIELDS FOR ENSEMBLE CONFIGURATION */

    Tcl_Obj *subcommandDict;	/* Dictionary providing mapping from
				 * subcommands to their implementing command
				 * prefixes, or NULL if we are to build the
				 * map automatically from the namespace
				 * exports. */
    Tcl_Obj *subcmdList;	/* List of commands that this ensemble
				 * actually provides, and whose implementation
				 * will be built using the subcommandDict (if
				 * present and defined) and by simple mapping
				 * to the namespace otherwise. If NULL,
				 * indicates that we are using the (dynamic)
				 * list of currently exported commands. */
    Tcl_Obj *unknownHandler;	/* Script prefix used to handle the case when
				 * no match is found (according to the rule
				 * defined by flag bit TCL_ENSEMBLE_PREFIX) or
				 * NULL to use the default error-generating
				 * behaviour. The script execution gets all
				 * the arguments to the ensemble command
				 * (including objv[0]) and will have the
				 * results passed directly back to the caller
				 * (including the error code) unless the code
				 * is TCL_CONTINUE in which case the
				 * subcommand will be reparsed by the ensemble
				 * core, presumably because the ensemble
				 * itself has been updated. */
} EnsembleConfig;

#define ENS_DEAD	0x1	/* Flag value to say that the ensemble is dead
				 * and on its way out. */

/*
 * Declarations for functions local to this file:
 */

static void		DeleteImportedCmd(ClientData clientData);
static int		DoImport(Tcl_Interp *interp,
			    Namespace *nsPtr, Tcl_HashEntry *hPtr,
			    const char *cmdName, const char *pattern,
			    Namespace *importNsPtr, int allowOverwrite);
static void		DupNsNameInternalRep(Tcl_Obj *objPtr,Tcl_Obj *copyPtr);
static char *		ErrorCodeRead(ClientData clientData,Tcl_Interp *interp,
			    const char *name1, const char *name2, int flags);
static char *		ErrorInfoRead(ClientData clientData,Tcl_Interp *interp,
			    const char *name1, const char *name2, int flags);
static char *		EstablishErrorCodeTraces(ClientData clientData,
			    Tcl_Interp *interp, const char *name1,
			    const char *name2, int flags);
static char *		EstablishErrorInfoTraces(ClientData clientData,
			    Tcl_Interp *interp, const char *name1,
			    const char *name2, int flags);
static void		FreeNsNameInternalRep(Tcl_Obj *objPtr);
static int		GetNamespaceFromObj(Tcl_Interp *interp,
			    Tcl_Obj *objPtr, Tcl_Namespace **nsPtrPtr);
static int		InvokeImportedCmd(ClientData clientData,
			    Tcl_Interp *interp,int objc,Tcl_Obj *const objv[]);
static int		NamespaceChildrenCmd(ClientData dummy,
			    Tcl_Interp *interp,int objc,Tcl_Obj *const objv[]);
static int		NamespaceCodeCmd(ClientData dummy, Tcl_Interp *interp,
			    int objc, Tcl_Obj *const objv[]);
static int		NamespaceCurrentCmd(ClientData dummy,
			    Tcl_Interp *interp,int objc,Tcl_Obj *const objv[]);
static int		NamespaceDeleteCmd(ClientData dummy,Tcl_Interp *interp,
			    int objc, Tcl_Obj *const objv[]);
static int		NamespaceEnsembleCmd(ClientData dummy,
			    Tcl_Interp *interp,int objc,Tcl_Obj *const objv[]);
static int		NamespaceEvalCmd(ClientData dummy, Tcl_Interp *interp,
			    int objc, Tcl_Obj *const objv[]);
static int		NamespaceExistsCmd(ClientData dummy,Tcl_Interp *interp,
			    int objc, Tcl_Obj *const objv[]);
static int		NamespaceExportCmd(ClientData dummy,Tcl_Interp *interp,
			    int objc, Tcl_Obj *const objv[]);
static int		NamespaceForgetCmd(ClientData dummy,Tcl_Interp *interp,
			    int objc, Tcl_Obj *const objv[]);
static void		NamespaceFree(Namespace *nsPtr);
static int		NamespaceImportCmd(ClientData dummy,Tcl_Interp *interp,
			    int objc, Tcl_Obj *const objv[]);
static int		NamespaceInscopeCmd(ClientData dummy,
			    Tcl_Interp *interp,int objc,Tcl_Obj *const objv[]);
static int		NamespaceOriginCmd(ClientData dummy,Tcl_Interp *interp,
			    int objc, Tcl_Obj *const objv[]);
static int		NamespaceParentCmd(ClientData dummy,Tcl_Interp *interp,
			    int objc, Tcl_Obj *const objv[]);
static int		NamespacePathCmd(ClientData dummy, Tcl_Interp *interp,
			    int objc, Tcl_Obj *const objv[]);
static int		NamespaceQualifiersCmd(ClientData dummy,
			    Tcl_Interp *interp,int objc,Tcl_Obj *const objv[]);
static int		NamespaceTailCmd(ClientData dummy, Tcl_Interp *interp,
			    int objc, Tcl_Obj *const objv[]);
static int		NamespaceUpvarCmd(ClientData dummy, Tcl_Interp *interp,
			    int objc, Tcl_Obj *const objv[]);
static int		NamespaceUnknownCmd(ClientData dummy,
			    Tcl_Interp *interp, int objc,
			    Tcl_Obj *const objv[]);
static int		NamespaceWhichCmd(ClientData dummy, Tcl_Interp *interp,
			    int objc, Tcl_Obj *const objv[]);
static int		SetNsNameFromAny(Tcl_Interp *interp, Tcl_Obj *objPtr);
static int		NsEnsembleImplementationCmd(ClientData clientData,
			    Tcl_Interp *interp,int objc,Tcl_Obj *const objv[]);
static void		BuildEnsembleConfig(EnsembleConfig *ensemblePtr);
static int		NsEnsembleStringOrder(const void *strPtr1,
			    const void *strPtr2);
static void		DeleteEnsembleConfig(ClientData clientData);
static void		MakeCachedEnsembleCommand(Tcl_Obj *objPtr,
			    EnsembleConfig *ensemblePtr,
			    const char *subcmdName, Tcl_Obj *prefixObjPtr);
static void		FreeEnsembleCmdRep(Tcl_Obj *objPtr);
static void		DupEnsembleCmdRep(Tcl_Obj *objPtr, Tcl_Obj *copyPtr);
static void		StringOfEnsembleCmdRep(Tcl_Obj *objPtr);
static void		UnlinkNsPath(Namespace *nsPtr);

/*
 * This structure defines a Tcl object type that contains a namespace
 * reference. It is used in commands that take the name of a namespace as an
 * argument. The namespace reference is resolved, and the result in cached in
 * the object.
 */

static Tcl_ObjType nsNameType = {
    "nsName",			/* the type's name */
    FreeNsNameInternalRep,	/* freeIntRepProc */
    DupNsNameInternalRep,	/* dupIntRepProc */
    NULL,			/* updateStringProc */
    SetNsNameFromAny		/* setFromAnyProc */
};

/*
 * This structure defines a Tcl object type that contains a reference to an
 * ensemble subcommand (e.g. the "length" in [string length ab]). It is used
 * to cache the mapping between the subcommand itself and the real command
 * that implements it.
 */

Tcl_ObjType tclEnsembleCmdType = {
    "ensembleCommand",		/* the type's name */
    FreeEnsembleCmdRep,		/* freeIntRepProc */
    DupEnsembleCmdRep,		/* dupIntRepProc */
    StringOfEnsembleCmdRep,	/* updateStringProc */
    NULL			/* setFromAnyProc */
};

/*
 *----------------------------------------------------------------------
 *
 * TclInitNamespaceSubsystem --
 *
 *	This function is called to initialize all the structures that are used
 *	by namespaces on a per-process basis.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

void
TclInitNamespaceSubsystem(void)
{
    /*
     * Does nothing for now.
     */
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetCurrentNamespace --
 *
 *	Returns a pointer to an interpreter's currently active namespace.
 *
 * Results:
 *	Returns a pointer to the interpreter's current namespace.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_Namespace *
Tcl_GetCurrentNamespace(
    register Tcl_Interp *interp)/* Interpreter whose current namespace is
				 * being queried. */
{
    return TclGetCurrentNamespace(interp);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetGlobalNamespace --
 *
 *	Returns a pointer to an interpreter's global :: namespace.
 *
 * Results:
 *	Returns a pointer to the specified interpreter's global namespace.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_Namespace *
Tcl_GetGlobalNamespace(
    register Tcl_Interp *interp)/* Interpreter whose global namespace should
				 * be returned. */
{
    return TclGetGlobalNamespace(interp);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_PushCallFrame --
 *
 *	Pushes a new call frame onto the interpreter's Tcl call stack. Called
 *	when executing a Tcl procedure or a "namespace eval" or "namespace
 *	inscope" command.
 *
 * Results:
 *	Returns TCL_OK if successful, or TCL_ERROR (along with an error
 *	message in the interpreter's result object) if something goes wrong.
 *
 * Side effects:
 *	Modifies the interpreter's Tcl call stack.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_PushCallFrame(
    Tcl_Interp *interp,		/* Interpreter in which the new call frame is
				 * to be pushed. */
    Tcl_CallFrame *callFramePtr,/* Points to a call frame structure to push.
				 * Storage for this has already been allocated
				 * by the caller; typically this is the
				 * address of a CallFrame structure allocated
				 * on the caller's C stack. The call frame
				 * will be initialized by this function. The
				 * caller can pop the frame later with
				 * Tcl_PopCallFrame, and it is responsible for
				 * freeing the frame's storage. */
    Tcl_Namespace *namespacePtr,/* Points to the namespace in which the frame
				 * will execute. If NULL, the interpreter's
				 * current namespace will be used. */
    int isProcCallFrame)	/* If nonzero, the frame represents a called
				 * Tcl procedure and may have local vars. Vars
				 * will ordinarily be looked up in the frame.
				 * If new variables are created, they will be
				 * created in the frame. If 0, the frame is
				 * for a "namespace eval" or "namespace
				 * inscope" command and var references are
				 * treated as references to namespace
				 * variables. */
{
    Interp *iPtr = (Interp *) interp;
    register CallFrame *framePtr = (CallFrame *) callFramePtr;
    register Namespace *nsPtr;

    if (namespacePtr == NULL) {
	nsPtr = (Namespace *) TclGetCurrentNamespace(interp);
    } else {
	nsPtr = (Namespace *) namespacePtr;

	/*
	 * TODO: Examine whether it would be better to guard based on NS_DYING
	 * or NS_KILLED. It appears that these are not tested because they can
	 * be set in a global interp that has been [namespace delete]d, but
	 * which never really completely goes away because of lingering global
	 * things like ::errorInfo and [::unknown] and hidden commands.
	 * Review of those designs might permit stricter checking here.
	 */

	if (nsPtr->flags & NS_DEAD) {
	    Tcl_Panic("Trying to push call frame for dead namespace");
	    /*NOTREACHED*/
	}
    }

    nsPtr->activationCount++;
    framePtr->nsPtr = nsPtr;
    framePtr->isProcCallFrame = isProcCallFrame;
    framePtr->objc = 0;
    framePtr->objv = NULL;
    framePtr->callerPtr = iPtr->framePtr;
    framePtr->callerVarPtr = iPtr->varFramePtr;
    if (iPtr->varFramePtr != NULL) {
	framePtr->level = (iPtr->varFramePtr->level + 1);
    } else {
	framePtr->level = 0;
    }
    framePtr->procPtr = NULL;		/* no called procedure */
    framePtr->varTablePtr = NULL;	/* and no local variables */
    framePtr->numCompiledLocals = 0;
    framePtr->compiledLocals = NULL;
    framePtr->clientData = NULL;
    framePtr->localCachePtr = NULL;

    /*
     * Push the new call frame onto the interpreter's stack of procedure call
     * frames making it the current frame.
     */

    iPtr->framePtr = framePtr;
    iPtr->varFramePtr = framePtr;
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_PopCallFrame --
 *
 *	Removes a call frame from the Tcl call stack for the interpreter.
 *	Called to remove a frame previously pushed by Tcl_PushCallFrame.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Modifies the call stack of the interpreter. Resets various fields of
 *	the popped call frame. If a namespace has been deleted and has no more
 *	activations on the call stack, the namespace is destroyed.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_PopCallFrame(
    Tcl_Interp *interp)		/* Interpreter with call frame to pop. */
{
    register Interp *iPtr = (Interp *) interp;
    register CallFrame *framePtr = iPtr->framePtr;
    Namespace *nsPtr;

    /*
     * It's important to remove the call frame from the interpreter's stack of
     * call frames before deleting local variables, so that traces invoked by
     * the variable deletion don't see the partially-deleted frame.
     */

    if (framePtr->callerPtr) {
	iPtr->framePtr = framePtr->callerPtr;
	iPtr->varFramePtr = framePtr->callerVarPtr;
    } else {
	/* Tcl_PopCallFrame: trying to pop rootCallFrame! */
    }

    if (framePtr->varTablePtr != NULL) {
	TclDeleteVars(iPtr, framePtr->varTablePtr);
	ckfree((char *) framePtr->varTablePtr);
	framePtr->varTablePtr = NULL;
    }
    if (framePtr->numCompiledLocals > 0) {
	TclDeleteCompiledLocalVars(iPtr, framePtr);
	if (--framePtr->localCachePtr->refCount == 0) {
	    TclFreeLocalCache(interp, framePtr->localCachePtr);
	}
	framePtr->localCachePtr = NULL;
    }

    /*
     * Decrement the namespace's count of active call frames. If the namespace
     * is "dying" and there are no more active call frames, call
     * Tcl_DeleteNamespace to destroy it.
     */

    nsPtr = framePtr->nsPtr;
    nsPtr->activationCount--;
    if ((nsPtr->flags & NS_DYING)
	    && (nsPtr->activationCount - (nsPtr == iPtr->globalNsPtr) == 0)) {
	Tcl_DeleteNamespace((Tcl_Namespace *) nsPtr);
    }
    framePtr->nsPtr = NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * TclPushStackFrame --
 *
 *	Allocates a new call frame in the interpreter's execution stack, then
 *	pushes it onto the interpreter's Tcl call stack. Called when executing
 *	a Tcl procedure or a "namespace eval" or "namespace inscope" command.
 *
 * Results:
 *	Returns TCL_OK if successful, or TCL_ERROR (along with an error
 *	message in the interpreter's result object) if something goes wrong.
 *
 * Side effects:
 *	Modifies the interpreter's Tcl call stack.
 *
 *----------------------------------------------------------------------
 */

int
TclPushStackFrame(
    Tcl_Interp *interp,		/* Interpreter in which the new call frame is
				 * to be pushed. */
    Tcl_CallFrame **framePtrPtr,/* Place to store a pointer to the stack
				 * allocated call frame. */
    Tcl_Namespace *namespacePtr,/* Points to the namespace in which the frame
				 * will execute. If NULL, the interpreter's
				 * current namespace will be used. */
    int isProcCallFrame)	/* If nonzero, the frame represents a called
				 * Tcl procedure and may have local vars. Vars
				 * will ordinarily be looked up in the frame.
				 * If new variables are created, they will be
				 * created in the frame. If 0, the frame is
				 * for a "namespace eval" or "namespace
				 * inscope" command and var references are
				 * treated as references to namespace
				 * variables. */
{
    *framePtrPtr = (Tcl_CallFrame *) TclStackAlloc(interp, sizeof(CallFrame));
    return Tcl_PushCallFrame(interp, *framePtrPtr, namespacePtr,
	    isProcCallFrame);
}

void
TclPopStackFrame(
    Tcl_Interp *interp)		/* Interpreter with call frame to pop. */
{
    CallFrame *freePtr = ((Interp *)interp)->framePtr;

    Tcl_PopCallFrame(interp);
    TclStackFree(interp, freePtr);
}

/*
 *----------------------------------------------------------------------
 *
 * EstablishErrorCodeTraces --
 *
 *	Creates traces on the ::errorCode variable to keep its value
 *	consistent with the expectations of legacy code.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Read and unset traces are established on ::errorCode.
 *
 *----------------------------------------------------------------------
 */

static char *
EstablishErrorCodeTraces(
    ClientData clientData,
    Tcl_Interp *interp,
    const char *name1,
    const char *name2,
    int flags)
{
    Tcl_TraceVar(interp, "errorCode", TCL_GLOBAL_ONLY | TCL_TRACE_READS,
	    ErrorCodeRead, NULL);
    Tcl_TraceVar(interp, "errorCode", TCL_GLOBAL_ONLY | TCL_TRACE_UNSETS,
	    EstablishErrorCodeTraces, NULL);
    return NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * ErrorCodeRead --
 *
 *	Called when the ::errorCode variable is read. Copies the current value
 *	of the interp's errorCode field into ::errorCode.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static char *
ErrorCodeRead(
    ClientData clientData,
    Tcl_Interp *interp,
    const char *name1,
    const char *name2,
    int flags)
{
    Interp *iPtr = (Interp *)interp;

    if (Tcl_InterpDeleted(interp) || !(iPtr->flags & ERR_LEGACY_COPY)) {
	return NULL;
    }
    if (iPtr->errorCode) {
	Tcl_ObjSetVar2(interp, iPtr->ecVar, NULL,
		iPtr->errorCode, TCL_GLOBAL_ONLY);
	return NULL;
    }
    if (NULL == Tcl_ObjGetVar2(interp, iPtr->ecVar, NULL, TCL_GLOBAL_ONLY)) {
	Tcl_ObjSetVar2(interp, iPtr->ecVar, NULL,
		Tcl_NewObj(), TCL_GLOBAL_ONLY);
    }
    return NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * EstablishErrorInfoTraces --
 *
 *	Creates traces on the ::errorInfo variable to keep its value
 *	consistent with the expectations of legacy code.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Read and unset traces are established on ::errorInfo.
 *
 *----------------------------------------------------------------------
 */

static char *
EstablishErrorInfoTraces(
    ClientData clientData,
    Tcl_Interp *interp,
    const char *name1,
    const char *name2,
    int flags)
{
    Tcl_TraceVar(interp, "errorInfo", TCL_GLOBAL_ONLY | TCL_TRACE_READS,
	    ErrorInfoRead, NULL);
    Tcl_TraceVar(interp, "errorInfo", TCL_GLOBAL_ONLY | TCL_TRACE_UNSETS,
	    EstablishErrorInfoTraces, NULL);
    return NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * ErrorInfoRead --
 *
 *	Called when the ::errorInfo variable is read. Copies the current value
 *	of the interp's errorInfo field into ::errorInfo.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static char *
ErrorInfoRead(
    ClientData clientData,
    Tcl_Interp *interp,
    const char *name1,
    const char *name2,
    int flags)
{
    Interp *iPtr = (Interp *) interp;

    if (Tcl_InterpDeleted(interp) || !(iPtr->flags & ERR_LEGACY_COPY)) {
	return NULL;
    }
    if (iPtr->errorInfo) {
	Tcl_ObjSetVar2(interp, iPtr->eiVar, NULL,
		iPtr->errorInfo, TCL_GLOBAL_ONLY);
	return NULL;
    }
    if (NULL == Tcl_ObjGetVar2(interp, iPtr->eiVar, NULL, TCL_GLOBAL_ONLY)) {
	Tcl_ObjSetVar2(interp, iPtr->eiVar, NULL,
		Tcl_NewObj(), TCL_GLOBAL_ONLY);
    }
    return NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_CreateNamespace --
 *
 *	Creates a new namespace with the given name. If there is no active
 *	namespace (i.e., the interpreter is being initialized), the global ::
 *	namespace is created and returned.
 *
 * Results:
 *	Returns a pointer to the new namespace if successful. If the namespace
 *	already exists or if another error occurs, this routine returns NULL,
 *	along with an error message in the interpreter's result object.
 *
 * Side effects:
 *	If the name contains "::" qualifiers and a parent namespace does not
 *	already exist, it is automatically created.
 *
 *----------------------------------------------------------------------
 */

Tcl_Namespace *
Tcl_CreateNamespace(
    Tcl_Interp *interp,		/* Interpreter in which a new namespace is
				 * being created. Also used for error
				 * reporting. */
    const char *name,		/* Name for the new namespace. May be a
				 * qualified name with names of ancestor
				 * namespaces separated by "::"s. */
    ClientData clientData,	/* One-word value to store with namespace. */
    Tcl_NamespaceDeleteProc *deleteProc)
				/* Function called to delete client data when
				 * the namespace is deleted. NULL if no
				 * function should be called. */
{
    Interp *iPtr = (Interp *) interp;
    register Namespace *nsPtr, *ancestorPtr;
    Namespace *parentPtr, *dummy1Ptr, *dummy2Ptr;
    Namespace *globalNsPtr = iPtr->globalNsPtr;
    const char *simpleName;
    Tcl_HashEntry *entryPtr;
    Tcl_DString buffer1, buffer2;
    Tcl_DString *namePtr, *buffPtr;
    int newEntry, nameLen;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    /*
     * If there is no active namespace, the interpreter is being initialized.
     */

    if ((globalNsPtr == NULL) && (iPtr->varFramePtr == NULL)) {
	/*
	 * Treat this namespace as the global namespace, and avoid looking for
	 * a parent.
	 */

	parentPtr = NULL;
	simpleName = "";
    } else if (*name == '\0') {
	Tcl_ResetResult(interp);
	Tcl_AppendResult(interp, "can't create namespace \"\": "
		"only global namespace can have empty name", NULL);
	return NULL;
    } else {
	/*
	 * Find the parent for the new namespace.
	 */

	TclGetNamespaceForQualName(interp, name, NULL,
		/*flags*/ (TCL_CREATE_NS_IF_UNKNOWN | TCL_LEAVE_ERR_MSG),
		&parentPtr, &dummy1Ptr, &dummy2Ptr, &simpleName);

	/*
	 * If the unqualified name at the end is empty, there were trailing
	 * "::"s after the namespace's name which we ignore. The new namespace
	 * was already (recursively) created and is pointed to by parentPtr.
	 */

	if (*simpleName == '\0') {
	    return (Tcl_Namespace *) parentPtr;
	}

	/*
	 * Check for a bad namespace name and make sure that the name does not
	 * already exist in the parent namespace.
	 */

	if (Tcl_FindHashEntry(&parentPtr->childTable, simpleName) != NULL) {
	    Tcl_AppendResult(interp, "can't create namespace \"", name,
		    "\": already exists", NULL);
	    return NULL;
	}
    }

    /*
     * Create the new namespace and root it in its parent. Increment the count
     * of namespaces created.
     */

    nsPtr = (Namespace *) ckalloc(sizeof(Namespace));
    nsPtr->name = ckalloc((unsigned) (strlen(simpleName)+1));
    strcpy(nsPtr->name, simpleName);
    nsPtr->fullName = NULL;		/* Set below. */
    nsPtr->clientData = clientData;
    nsPtr->deleteProc = deleteProc;
    nsPtr->parentPtr = parentPtr;
    Tcl_InitHashTable(&nsPtr->childTable, TCL_STRING_KEYS);
    nsPtr->nsId = ++(tsdPtr->numNsCreated);
    nsPtr->interp = interp;
    nsPtr->flags = 0;
    nsPtr->activationCount = 0;
    nsPtr->refCount = 0;
    Tcl_InitHashTable(&nsPtr->cmdTable, TCL_STRING_KEYS);
    TclInitVarHashTable(&nsPtr->varTable, nsPtr);
    nsPtr->exportArrayPtr = NULL;
    nsPtr->numExportPatterns = 0;
    nsPtr->maxExportPatterns = 0;
    nsPtr->cmdRefEpoch = 0;
    nsPtr->resolverEpoch = 0;
    nsPtr->cmdResProc = NULL;
    nsPtr->varResProc = NULL;
    nsPtr->compiledVarResProc = NULL;
    nsPtr->exportLookupEpoch = 0;
    nsPtr->ensembles = NULL;
    nsPtr->unknownHandlerPtr = NULL;
    nsPtr->commandPathLength = 0;
    nsPtr->commandPathArray = NULL;
    nsPtr->commandPathSourceList = NULL;

    if (parentPtr != NULL) {
	entryPtr = Tcl_CreateHashEntry(&parentPtr->childTable, simpleName,
		&newEntry);
	Tcl_SetHashValue(entryPtr, nsPtr);
    } else {
	/*
	 * In the global namespace create traces to maintain the ::errorInfo
	 * and ::errorCode variables.
	 */

	iPtr->globalNsPtr = nsPtr;
	EstablishErrorInfoTraces(NULL, interp, NULL, NULL, 0);
	EstablishErrorCodeTraces(NULL, interp, NULL, NULL, 0);
    }

    /*
     * Build the fully qualified name for this namespace.
     */

    Tcl_DStringInit(&buffer1);
    Tcl_DStringInit(&buffer2);
    namePtr = &buffer1;
    buffPtr = &buffer2;
    for (ancestorPtr = nsPtr; ancestorPtr != NULL;
	    ancestorPtr = ancestorPtr->parentPtr) {
	if (ancestorPtr != globalNsPtr) {
	    register Tcl_DString *tempPtr = namePtr;

	    Tcl_DStringAppend(buffPtr, "::", 2);
	    Tcl_DStringAppend(buffPtr, ancestorPtr->name, -1);
	    Tcl_DStringAppend(buffPtr, Tcl_DStringValue(namePtr),
		    Tcl_DStringLength(namePtr));

	    /*
	     * Clear the unwanted buffer or we end up appending to previous
	     * results, making the namespace fullNames of nested namespaces
	     * very wrong (and strange).
	     */

	    Tcl_DStringSetLength(namePtr, 0);

	    /*
	     * Now swap the buffer pointers so that we build in the other
	     * buffer. This is faster than repeated copying back and forth
	     * between buffers.
	     */

	    namePtr = buffPtr;
	    buffPtr = tempPtr;
	}
    }

    name = Tcl_DStringValue(namePtr);
    nameLen = Tcl_DStringLength(namePtr);
    nsPtr->fullName = ckalloc((unsigned) (nameLen+1));
    memcpy(nsPtr->fullName, name, (unsigned) nameLen + 1);

    Tcl_DStringFree(&buffer1);
    Tcl_DStringFree(&buffer2);

    /*
     * Return a pointer to the new namespace.
     */

    return (Tcl_Namespace *) nsPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DeleteNamespace --
 *
 *	Deletes a namespace and all of the commands, variables, and other
 *	namespaces within it.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	When a namespace is deleted, it is automatically removed as a child of
 *	its parent namespace. Also, all its commands, variables and child
 *	namespaces are deleted.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_DeleteNamespace(
    Tcl_Namespace *namespacePtr)/* Points to the namespace to delete. */
{
    register Namespace *nsPtr = (Namespace *) namespacePtr;
    Interp *iPtr = (Interp *) nsPtr->interp;
    Namespace *globalNsPtr = (Namespace *)
	    TclGetGlobalNamespace((Tcl_Interp *) iPtr);
    Tcl_HashEntry *entryPtr;

    /*
     * If the namespace has associated ensemble commands, delete them first.
     * This leaves the actual contents of the namespace alone (unless they are
     * linked ensemble commands, of course). Note that this code is actually
     * reentrant so command delete traces won't purturb things badly.
     */

    while (nsPtr->ensembles != NULL) {
	EnsembleConfig *ensemblePtr = (EnsembleConfig *) nsPtr->ensembles;

	/*
	 * Splice out and link to indicate that we've already been killed.
	 */

	nsPtr->ensembles = (Tcl_Ensemble *) ensemblePtr->next;
	ensemblePtr->next = ensemblePtr;
	Tcl_DeleteCommandFromToken(nsPtr->interp, ensemblePtr->token);
    }

    /*
     * If the namespace has a registered unknown handler (TIP 181), then free
     * it here.
     */

    if (nsPtr->unknownHandlerPtr != NULL) {
	Tcl_DecrRefCount(nsPtr->unknownHandlerPtr);
	nsPtr->unknownHandlerPtr = NULL;
    }

    /*
     * If the namespace is on the call frame stack, it is marked as "dying"
     * (NS_DYING is OR'd into its flags): the namespace can't be looked up by
     * name but its commands and variables are still usable by those active
     * call frames. When all active call frames referring to the namespace
     * have been popped from the Tcl stack, Tcl_PopCallFrame will call this
     * function again to delete everything in the namespace. If no nsName
     * objects refer to the namespace (i.e., if its refCount is zero), its
     * commands and variables are deleted and the storage for its namespace
     * structure is freed. Otherwise, if its refCount is nonzero, the
     * namespace's commands and variables are deleted but the structure isn't
     * freed. Instead, NS_DEAD is OR'd into the structure's flags to allow the
     * namespace resolution code to recognize that the namespace is "deleted".
     * The structure's storage is freed by FreeNsNameInternalRep when its
     * refCount reaches 0.
     */

    if (nsPtr->activationCount - (nsPtr == globalNsPtr) > 0) {
	nsPtr->flags |= NS_DYING;
	if (nsPtr->parentPtr != NULL) {
	    entryPtr = Tcl_FindHashEntry(&nsPtr->parentPtr->childTable,
		    nsPtr->name);
	    if (entryPtr != NULL) {
		Tcl_DeleteHashEntry(entryPtr);
	    }
	}
	nsPtr->parentPtr = NULL;
    } else if (!(nsPtr->flags & NS_KILLED)) {
	/*
	 * Delete the namespace and everything in it. If this is the global
	 * namespace, then clear it but don't free its storage unless the
	 * interpreter is being torn down. Set the NS_KILLED flag to avoid
	 * recursive calls here - if the namespace is really in the process of
	 * being deleted, ignore any second call.
	 */

	nsPtr->flags |= (NS_DYING|NS_KILLED);

	TclTeardownNamespace(nsPtr);

	if ((nsPtr != globalNsPtr) || (iPtr->flags & DELETED)) {
	    /*
	     * If this is the global namespace, then it may have residual
	     * "errorInfo" and "errorCode" variables for errors that occurred
	     * while it was being torn down. Try to clear the variable list
	     * one last time.
	     */

	    TclDeleteNamespaceVars(nsPtr);

	    Tcl_DeleteHashTable(&nsPtr->childTable);
	    Tcl_DeleteHashTable(&nsPtr->cmdTable);

	    /*
	     * If the reference count is 0, then discard the namespace.
	     * Otherwise, mark it as "dead" so that it can't be used.
	     */

	    if (nsPtr->refCount == 0) {
		NamespaceFree(nsPtr);
	    } else {
		nsPtr->flags |= NS_DEAD;
	    }
	} else {
	    /*
	     * Restore the ::errorInfo and ::errorCode traces.
	     */

	    EstablishErrorInfoTraces(NULL, nsPtr->interp, NULL, NULL, 0);
	    EstablishErrorCodeTraces(NULL, nsPtr->interp, NULL, NULL, 0);

	    /*
	     * We didn't really kill it, so remove the KILLED marks, so it can
	     * get killed later, avoiding mem leaks.
	     */

	    nsPtr->flags &= ~(NS_DYING|NS_KILLED);
	}
    }
}

/*
 *----------------------------------------------------------------------
 *
 * TclTeardownNamespace --
 *
 *	Used internally to dismantle and unlink a namespace when it is
 *	deleted. Divorces the namespace from its parent, and deletes all
 *	commands, variables, and child namespaces.
 *
 *	This is kept separate from Tcl_DeleteNamespace so that the global
 *	namespace can be handled specially.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Removes this namespace from its parent's child namespace hashtable.
 *	Deletes all commands, variables and namespaces in this namespace.
 *
 *----------------------------------------------------------------------
 */

void
TclTeardownNamespace(
    register Namespace *nsPtr)	/* Points to the namespace to be dismantled
				 * and unlinked from its parent. */
{
    Interp *iPtr = (Interp *) nsPtr->interp;
    register Tcl_HashEntry *entryPtr;
    Tcl_HashSearch search;
    Tcl_Namespace *childNsPtr;
    Tcl_Command cmd;
    int i;

    /*
     * Start by destroying the namespace's variable table, since variables
     * might trigger traces. Variable table should be cleared but not freed!
     * TclDeleteNamespaceVars frees it, so we reinitialize it afterwards.
     */

    TclDeleteNamespaceVars(nsPtr);
    TclInitVarHashTable(&nsPtr->varTable, nsPtr);

    /*
     * Delete all commands in this namespace. Be careful when traversing the
     * hash table: when each command is deleted, it removes itself from the
     * command table.
     *
     * Don't optimize to Tcl_NextHashEntry() because of traces.
     */

    for (entryPtr = Tcl_FirstHashEntry(&nsPtr->cmdTable, &search);
	    entryPtr != NULL;
	    entryPtr = Tcl_FirstHashEntry(&nsPtr->cmdTable, &search)) {
	cmd = Tcl_GetHashValue(entryPtr);
	Tcl_DeleteCommandFromToken((Tcl_Interp *) iPtr, cmd);
    }
    Tcl_DeleteHashTable(&nsPtr->cmdTable);
    Tcl_InitHashTable(&nsPtr->cmdTable, TCL_STRING_KEYS);

    /*
     * Remove the namespace from its parent's child hashtable.
     */

    if (nsPtr->parentPtr != NULL) {
	entryPtr = Tcl_FindHashEntry(&nsPtr->parentPtr->childTable,
		nsPtr->name);
	if (entryPtr != NULL) {
	    Tcl_DeleteHashEntry(entryPtr);
	}
    }
    nsPtr->parentPtr = NULL;

    /*
     * Delete the namespace path if one is installed.
     */

    if (nsPtr->commandPathLength != 0) {
	UnlinkNsPath(nsPtr);
	nsPtr->commandPathLength = 0;
    }
    if (nsPtr->commandPathSourceList != NULL) {
	NamespacePathEntry *nsPathPtr = nsPtr->commandPathSourceList;
	do {
	    if (nsPathPtr->nsPtr != NULL && nsPathPtr->creatorNsPtr != NULL) {
		nsPathPtr->creatorNsPtr->cmdRefEpoch++;
	    }
	    nsPathPtr->nsPtr = NULL;
	    nsPathPtr = nsPathPtr->nextPtr;
	} while (nsPathPtr != NULL);
	nsPtr->commandPathSourceList = NULL;
    }

    /*
     * Delete all the child namespaces.
     *
     * BE CAREFUL: When each child is deleted, it will divorce itself from its
     * parent. You can't traverse a hash table properly if its elements are
     * being deleted. We use only the Tcl_FirstHashEntry function to be safe.
     *
     * Don't optimize to Tcl_NextHashEntry() because of traces.
     */

    for (entryPtr = Tcl_FirstHashEntry(&nsPtr->childTable, &search);
	    entryPtr != NULL;
	    entryPtr = Tcl_FirstHashEntry(&nsPtr->childTable, &search)) {
	childNsPtr = Tcl_GetHashValue(entryPtr);
	Tcl_DeleteNamespace(childNsPtr);
    }

    /*
     * Free the namespace's export pattern array.
     */

    if (nsPtr->exportArrayPtr != NULL) {
	for (i = 0;  i < nsPtr->numExportPatterns;  i++) {
	    ckfree(nsPtr->exportArrayPtr[i]);
	}
	ckfree((char *) nsPtr->exportArrayPtr);
	nsPtr->exportArrayPtr = NULL;
	nsPtr->numExportPatterns = 0;
	nsPtr->maxExportPatterns = 0;
    }

    /*
     * Free any client data associated with the namespace.
     */

    if (nsPtr->deleteProc != NULL) {
	(*nsPtr->deleteProc)(nsPtr->clientData);
    }
    nsPtr->deleteProc = NULL;
    nsPtr->clientData = NULL;

    /*
     * Reset the namespace's id field to ensure that this namespace won't be
     * interpreted as valid by, e.g., the cache validation code for cached
     * command references in Tcl_GetCommandFromObj.
     */

    nsPtr->nsId = 0;
}

/*
 *----------------------------------------------------------------------
 *
 * NamespaceFree --
 *
 *	Called after a namespace has been deleted, when its reference count
 *	reaches 0. Frees the data structure representing the namespace.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static void
NamespaceFree(
    register Namespace *nsPtr)	/* Points to the namespace to free. */
{
    /*
     * Most of the namespace's contents are freed when the namespace is
     * deleted by Tcl_DeleteNamespace. All that remains is to free its names
     * (for error messages), and the structure itself.
     */

    ckfree(nsPtr->name);
    ckfree(nsPtr->fullName);

    ckfree((char *) nsPtr);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_Export --
 *
 *	Makes all the commands matching a pattern available to later be
 *	imported from the namespace specified by namespacePtr (or the current
 *	namespace if namespacePtr is NULL). The specified pattern is appended
 *	onto the namespace's export pattern list, which is optionally cleared
 *	beforehand.
 *
 * Results:
 *	Returns TCL_OK if successful, or TCL_ERROR (along with an error
 *	message in the interpreter's result) if something goes wrong.
 *
 * Side effects:
 *	Appends the export pattern onto the namespace's export list.
 *	Optionally reset the namespace's export pattern list.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_Export(
    Tcl_Interp *interp,		/* Current interpreter. */
    Tcl_Namespace *namespacePtr,/* Points to the namespace from which commands
				 * are to be exported. NULL for the current
				 * namespace. */
    const char *pattern,	/* String pattern indicating which commands to
				 * export. This pattern may not include any
				 * namespace qualifiers; only commands in the
				 * specified namespace may be exported. */
    int resetListFirst)		/* If nonzero, resets the namespace's export
				 * list before appending. */
{
#define INIT_EXPORT_PATTERNS 5
    Namespace *nsPtr, *exportNsPtr, *dummyPtr;
    Namespace *currNsPtr = (Namespace *) TclGetCurrentNamespace(interp);
    const char *simplePattern;
    char *patternCpy;
    int neededElems, len, i;

    /*
     * If the specified namespace is NULL, use the current namespace.
     */

    if (namespacePtr == NULL) {
	nsPtr = (Namespace *) currNsPtr;
    } else {
	nsPtr = (Namespace *) namespacePtr;
    }

    /*
     * If resetListFirst is true (nonzero), clear the namespace's export
     * pattern list.
     */

    if (resetListFirst) {
	if (nsPtr->exportArrayPtr != NULL) {
	    for (i = 0;  i < nsPtr->numExportPatterns;  i++) {
		ckfree(nsPtr->exportArrayPtr[i]);
	    }
	    ckfree((char *) nsPtr->exportArrayPtr);
	    nsPtr->exportArrayPtr = NULL;
	    TclInvalidateNsCmdLookup(nsPtr);
	    nsPtr->numExportPatterns = 0;
	    nsPtr->maxExportPatterns = 0;
	}
    }

    /*
     * Check that the pattern doesn't have namespace qualifiers.
     */

    TclGetNamespaceForQualName(interp, pattern, nsPtr,
	    /*flags*/ (TCL_LEAVE_ERR_MSG | TCL_NAMESPACE_ONLY),
	    &exportNsPtr, &dummyPtr, &dummyPtr, &simplePattern);

    if ((exportNsPtr != nsPtr) || (strcmp(pattern, simplePattern) != 0)) {
	Tcl_AppendResult(interp, "invalid export pattern \"", pattern,
		"\": pattern can't specify a namespace", NULL);
	return TCL_ERROR;
    }

    /*
     * Make sure that we don't already have the pattern in the array
     */

    if (nsPtr->exportArrayPtr != NULL) {
	for (i = 0;  i < nsPtr->numExportPatterns;  i++) {
	    if (strcmp(pattern, nsPtr->exportArrayPtr[i]) == 0) {
		/*
		 * The pattern already exists in the list.
		 */

		return TCL_OK;
	    }
	}
    }

    /*
     * Make sure there is room in the namespace's pattern array for the new
     * pattern.
     */

    neededElems = nsPtr->numExportPatterns + 1;
    if (neededElems > nsPtr->maxExportPatterns) {
	nsPtr->maxExportPatterns = nsPtr->maxExportPatterns ?
		2 * nsPtr->maxExportPatterns : INIT_EXPORT_PATTERNS;
	nsPtr->exportArrayPtr = (char **)
		ckrealloc((char *) nsPtr->exportArrayPtr,
		sizeof(char *) * nsPtr->maxExportPatterns);
    }

    /*
     * Add the pattern to the namespace's array of export patterns.
     */

    len = strlen(pattern);
    patternCpy = ckalloc((unsigned) (len + 1));
    memcpy(patternCpy, pattern, (unsigned) len + 1);

    nsPtr->exportArrayPtr[nsPtr->numExportPatterns] = patternCpy;
    nsPtr->numExportPatterns++;

    /*
     * The list of commands actually exported from the namespace might have
     * changed (probably will have!) However, we do not need to recompute this
     * just yet; next time we need the info will be soon enough.
     */

    TclInvalidateNsCmdLookup(nsPtr);

    return TCL_OK;
#undef INIT_EXPORT_PATTERNS
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_AppendExportList --
 *
 *	Appends onto the argument object the list of export patterns for the
 *	specified namespace.
 *
 * Results:
 *	The return value is normally TCL_OK; in this case the object
 *	referenced by objPtr has each export pattern appended to it. If an
 *	error occurs, TCL_ERROR is returned and the interpreter's result holds
 *	an error message.
 *
 * Side effects:
 *	If necessary, the object referenced by objPtr is converted into a list
 *	object.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_AppendExportList(
    Tcl_Interp *interp,		/* Interpreter used for error reporting. */
    Tcl_Namespace *namespacePtr,/* Points to the namespace whose export
				 * pattern list is appended onto objPtr. NULL
				 * for the current namespace. */
    Tcl_Obj *objPtr)		/* Points to the Tcl object onto which the
				 * export pattern list is appended. */
{
    Namespace *nsPtr;
    int i, result;

    /*
     * If the specified namespace is NULL, use the current namespace.
     */

    if (namespacePtr == NULL) {
	nsPtr = (Namespace *) TclGetCurrentNamespace(interp);
    } else {
	nsPtr = (Namespace *) namespacePtr;
    }

    /*
     * Append the export pattern list onto objPtr.
     */

    for (i = 0;  i < nsPtr->numExportPatterns;  i++) {
	result = Tcl_ListObjAppendElement(interp, objPtr,
		Tcl_NewStringObj(nsPtr->exportArrayPtr[i], -1));
	if (result != TCL_OK) {
	    return result;
	}
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_Import --
 *
 *	Imports all of the commands matching a pattern into the namespace
 *	specified by namespacePtr (or the current namespace if contextNsPtr is
 *	NULL). This is done by creating a new command (the "imported command")
 *	that points to the real command in its original namespace.
 *
 *	If matching commands are on the autoload path but haven't been loaded
 *	yet, this command forces them to be loaded, then creates the links to
 *	them.
 *
 * Results:
 *	Returns TCL_OK if successful, or TCL_ERROR (along with an error
 *	message in the interpreter's result) if something goes wrong.
 *
 * Side effects:
 *	Creates new commands in the importing namespace. These indirect calls
 *	back to the real command and are deleted if the real commands are
 *	deleted.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_Import(
    Tcl_Interp *interp,		/* Current interpreter. */
    Tcl_Namespace *namespacePtr,/* Points to the namespace into which the
				 * commands are to be imported. NULL for the
				 * current namespace. */
    const char *pattern,	/* String pattern indicating which commands to
				 * import. This pattern should be qualified by
				 * the name of the namespace from which to
				 * import the command(s). */
    int allowOverwrite)		/* If nonzero, allow existing commands to be
				 * overwritten by imported commands. If 0,
				 * return an error if an imported cmd
				 * conflicts with an existing one. */
{
    Namespace *nsPtr, *importNsPtr, *dummyPtr;
    const char *simplePattern;
    register Tcl_HashEntry *hPtr;
    Tcl_HashSearch search;

    /*
     * If the specified namespace is NULL, use the current namespace.
     */

    if (namespacePtr == NULL) {
	nsPtr = (Namespace *) TclGetCurrentNamespace(interp);
    } else {
	nsPtr = (Namespace *) namespacePtr;
    }

    /*
     * First, invoke the "auto_import" command with the pattern being
     * imported. This command is part of the Tcl library. It looks for
     * imported commands in autoloaded libraries and loads them in. That way,
     * they will be found when we try to create links below.
     *
     * Note that we don't just call Tcl_EvalObjv() directly because we do not
     * want absence of the command to be a failure case.
     */

    if (Tcl_FindCommand(interp,"auto_import",NULL,TCL_GLOBAL_ONLY) != NULL) {
	Tcl_Obj *objv[2];
	int result;

	TclNewLiteralStringObj(objv[0], "auto_import");
	objv[1] = Tcl_NewStringObj(pattern, -1);

	Tcl_IncrRefCount(objv[0]);
	Tcl_IncrRefCount(objv[1]);
	result = Tcl_EvalObjv(interp, 2, objv, TCL_GLOBAL_ONLY);
	Tcl_DecrRefCount(objv[0]);
	Tcl_DecrRefCount(objv[1]);

	if (result != TCL_OK) {
	    return TCL_ERROR;
	}
	Tcl_ResetResult(interp);
    }

    /*
     * From the pattern, find the namespace from which we are importing and
     * get the simple pattern (no namespace qualifiers or ::'s) at the end.
     */

    if (strlen(pattern) == 0) {
	Tcl_SetObjResult(interp, Tcl_NewStringObj("empty import pattern", -1));
	return TCL_ERROR;
    }
    TclGetNamespaceForQualName(interp, pattern, nsPtr,
	    /*flags*/ (TCL_LEAVE_ERR_MSG | TCL_NAMESPACE_ONLY),
	    &importNsPtr, &dummyPtr, &dummyPtr, &simplePattern);

    if (importNsPtr == NULL) {
	Tcl_AppendResult(interp, "unknown namespace in import pattern \"",
		pattern, "\"", NULL);
	Tcl_SetErrorCode(interp, "TCL", "LOOKUP", "NAMESPACE", pattern, NULL);
	return TCL_ERROR;
    }
    if (importNsPtr == nsPtr) {
	if (pattern == simplePattern) {
	    Tcl_AppendResult(interp,
		    "no namespace specified in import pattern \"", pattern,
		    "\"", NULL);
	} else {
	    Tcl_AppendResult(interp, "import pattern \"", pattern,
		    "\" tries to import from namespace \"",
		    importNsPtr->name, "\" into itself", NULL);
	}
	return TCL_ERROR;
    }

    /*
     * Scan through the command table in the source namespace and look for
     * exported commands that match the string pattern. Create an "imported
     * command" in the current namespace for each imported command; these
     * commands redirect their invocations to the "real" command.
     */

    if ((simplePattern != NULL) && TclMatchIsTrivial(simplePattern)) {
	hPtr = Tcl_FindHashEntry(&importNsPtr->cmdTable, simplePattern);
	if (hPtr == NULL) {
	    return TCL_OK;
	}
	return DoImport(interp, nsPtr, hPtr, simplePattern, pattern,
		importNsPtr, allowOverwrite);
    }
    for (hPtr = Tcl_FirstHashEntry(&importNsPtr->cmdTable, &search);
	    (hPtr != NULL); hPtr = Tcl_NextHashEntry(&search)) {
	char *cmdName = Tcl_GetHashKey(&importNsPtr->cmdTable, hPtr);
	if (Tcl_StringMatch(cmdName, simplePattern) &&
		DoImport(interp, nsPtr, hPtr, cmdName, pattern, importNsPtr,
		allowOverwrite) == TCL_ERROR) {
	    return TCL_ERROR;
	}
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * DoImport --
 *
 *	Import a particular command from one namespace into another. Helper
 *	for Tcl_Import().
 *
 * Results:
 *	Standard Tcl result code. If TCL_ERROR, appends an error message to
 *	the interpreter result.
 *
 * Side effects:
 *	A new command is created in the target namespace unless this is a
 *	reimport of exactly the same command as before.
 *
 *----------------------------------------------------------------------
 */

static int
DoImport(
    Tcl_Interp *interp,
    Namespace *nsPtr,
    Tcl_HashEntry *hPtr,
    const char *cmdName,
    const char *pattern,
    Namespace *importNsPtr,
    int allowOverwrite)
{
    int i = 0, exported = 0;
    Tcl_HashEntry *found;

    /*
     * The command cmdName in the source namespace matches the pattern. Check
     * whether it was exported. If it wasn't, we ignore it.
     */

    while (!exported && (i < importNsPtr->numExportPatterns)) {
	exported |= Tcl_StringMatch(cmdName, importNsPtr->exportArrayPtr[i++]);
    }
    if (!exported) {
	return TCL_OK;
    }

    /*
     * Unless there is a name clash, create an imported command in the current
     * namespace that refers to cmdPtr.
     */

    found = Tcl_FindHashEntry(&nsPtr->cmdTable, cmdName);
    if ((found == NULL) || allowOverwrite) {
	/*
	 * Create the imported command and its client data. To create the new
	 * command in the current namespace, generate a fully qualified name
	 * for it.
	 */

	Tcl_DString ds;
	Tcl_Command importedCmd;
	ImportedCmdData *dataPtr;
	Command *cmdPtr;
	ImportRef *refPtr;

	Tcl_DStringInit(&ds);
	Tcl_DStringAppend(&ds, nsPtr->fullName, -1);
	if (nsPtr != ((Interp *) interp)->globalNsPtr) {
	    Tcl_DStringAppend(&ds, "::", 2);
	}
	Tcl_DStringAppend(&ds, cmdName, -1);

	/*
	 * Check whether creating the new imported command in the current
	 * namespace would create a cycle of imported command references.
	 */

	cmdPtr = Tcl_GetHashValue(hPtr);
	if (found != NULL && cmdPtr->deleteProc == DeleteImportedCmd) {
	    Command *overwrite = Tcl_GetHashValue(found);
	    Command *link = cmdPtr;

	    while (link->deleteProc == DeleteImportedCmd) {
		ImportedCmdData *dataPtr = link->objClientData;

		link = dataPtr->realCmdPtr;
		if (overwrite == link) {
		    Tcl_AppendResult(interp, "import pattern \"", pattern,
			    "\" would create a loop containing command \"",
			    Tcl_DStringValue(&ds), "\"", NULL);
		    Tcl_DStringFree(&ds);
		    return TCL_ERROR;
		}
	    }
	}

	dataPtr = (ImportedCmdData *) ckalloc(sizeof(ImportedCmdData));
	importedCmd = Tcl_CreateObjCommand(interp, Tcl_DStringValue(&ds),
		InvokeImportedCmd, dataPtr, DeleteImportedCmd);
	dataPtr->realCmdPtr = cmdPtr;
	dataPtr->selfPtr = (Command *) importedCmd;
	dataPtr->selfPtr->compileProc = cmdPtr->compileProc;
	Tcl_DStringFree(&ds);

	/*
	 * Create an ImportRef structure describing this new import command
	 * and add it to the import ref list in the "real" command.
	 */

	refPtr = (ImportRef *) ckalloc(sizeof(ImportRef));
	refPtr->importedCmdPtr = (Command *) importedCmd;
	refPtr->nextPtr = cmdPtr->importRefPtr;
	cmdPtr->importRefPtr = refPtr;
    } else {
	Command *overwrite = Tcl_GetHashValue(found);

	if (overwrite->deleteProc == DeleteImportedCmd) {
	    ImportedCmdData *dataPtr = overwrite->objClientData;

	    if (dataPtr->realCmdPtr == Tcl_GetHashValue(hPtr)) {
		/*
		 * Repeated import of same command is acceptable.
		 */

		return TCL_OK;
	    }
	}
	Tcl_AppendResult(interp, "can't import command \"", cmdName,
		"\": already exists", NULL);
	return TCL_ERROR;
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ForgetImport --
 *
 *	Deletes commands previously imported into the namespace indicated.
 *	The by namespacePtr, or the current namespace of interp, when
 *	namespacePtr is NULL. The pattern controls which imported commands are
 *	deleted. A simple pattern, one without namespace separators, matches
 *	the current command names of imported commands in the namespace.
 *	Matching imported commands are deleted. A qualified pattern is
 *	interpreted as deletion selection on the basis of where the command is
 *	imported from. The original command and "first link" command for each
 *	imported command are determined, and they are matched against the
 *	pattern. A match leads to deletion of the imported command.
 *
 * Results:
 *	Returns TCL_ERROR and records an error message in the interp result if
 *	a namespace qualified pattern refers to a namespace that does not
 *	exist. Otherwise, returns TCL_OK.
 *
 * Side effects:
 *	May delete commands.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_ForgetImport(
    Tcl_Interp *interp,		/* Current interpreter. */
    Tcl_Namespace *namespacePtr,/* Points to the namespace from which
				 * previously imported commands should be
				 * removed. NULL for current namespace. */
    const char *pattern)	/* String pattern indicating which imported
				 * commands to remove. */
{
    Namespace *nsPtr, *sourceNsPtr, *dummyPtr;
    const char *simplePattern;
    char *cmdName;
    register Tcl_HashEntry *hPtr;
    Tcl_HashSearch search;

    /*
     * If the specified namespace is NULL, use the current namespace.
     */

    if (namespacePtr == NULL) {
	nsPtr = (Namespace *) TclGetCurrentNamespace(interp);
    } else {
	nsPtr = (Namespace *) namespacePtr;
    }

    /*
     * Parse the pattern into its namespace-qualification (if any) and the
     * simple pattern.
     */

    TclGetNamespaceForQualName(interp, pattern, nsPtr,
	    /*flags*/ (TCL_LEAVE_ERR_MSG | TCL_NAMESPACE_ONLY),
	    &sourceNsPtr, &dummyPtr, &dummyPtr, &simplePattern);

    if (sourceNsPtr == NULL) {
	Tcl_AppendResult(interp,
		"unknown namespace in namespace forget pattern \"",
		pattern, "\"", NULL);
	Tcl_SetErrorCode(interp, "TCL", "LOOKUP", "NAMESPACE", pattern, NULL);
	return TCL_ERROR;
    }

    if (strcmp(pattern, simplePattern) == 0) {
	/*
	 * The pattern is simple. Delete any imported commands that match it.
	 */

	if (TclMatchIsTrivial(simplePattern)) {
	    Command *cmdPtr;

	    hPtr = Tcl_FindHashEntry(&nsPtr->cmdTable, simplePattern);
	    if ((hPtr != NULL)
		    && (cmdPtr = Tcl_GetHashValue(hPtr))
		    && (cmdPtr->deleteProc == DeleteImportedCmd)) {
		Tcl_DeleteCommandFromToken(interp, (Tcl_Command) cmdPtr);
	    }
	    return TCL_OK;
	}
	for (hPtr = Tcl_FirstHashEntry(&nsPtr->cmdTable, &search);
		(hPtr != NULL); hPtr = Tcl_NextHashEntry(&search)) {
	    Command *cmdPtr = Tcl_GetHashValue(hPtr);

	    if (cmdPtr->deleteProc != DeleteImportedCmd) {
		continue;
	    }
	    cmdName = Tcl_GetHashKey(&nsPtr->cmdTable, hPtr);
	    if (Tcl_StringMatch(cmdName, simplePattern)) {
		Tcl_DeleteCommandFromToken(interp, (Tcl_Command) cmdPtr);
	    }
	}
	return TCL_OK;
    }

    /*
     * The pattern was namespace-qualified.
     */

    for (hPtr = Tcl_FirstHashEntry(&nsPtr->cmdTable, &search); (hPtr != NULL);
	    hPtr = Tcl_NextHashEntry(&search)) {
	Tcl_CmdInfo info;
	Tcl_Command token = Tcl_GetHashValue(hPtr);
	Tcl_Command origin = TclGetOriginalCommand(token);

	if (Tcl_GetCommandInfoFromToken(origin, &info) == 0) {
	    continue;			/* Not an imported command. */
	}
	if (info.namespacePtr != (Tcl_Namespace *) sourceNsPtr) {
	    /*
	     * Original not in namespace we're matching. Check the first link
	     * in the import chain.
	     */

	    Command *cmdPtr = (Command *) token;
	    ImportedCmdData *dataPtr = cmdPtr->objClientData;
	    Tcl_Command firstToken = (Tcl_Command) dataPtr->realCmdPtr;

	    if (firstToken == origin) {
		continue;
	    }
	    Tcl_GetCommandInfoFromToken(firstToken, &info);
	    if (info.namespacePtr != (Tcl_Namespace *) sourceNsPtr) {
		continue;
	    }
	    origin = firstToken;
	}
	if (Tcl_StringMatch(Tcl_GetCommandName(NULL, origin), simplePattern)) {
	    Tcl_DeleteCommandFromToken(interp, token);
	}
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * TclGetOriginalCommand --
 *
 *	An imported command is created in an namespace when a "real" command
 *	is imported from another namespace. If the specified command is an
 *	imported command, this function returns the original command it refers
 *	to.
 *
 * Results:
 *	If the command was imported into a sequence of namespaces a, b,...,n
 *	where each successive namespace just imports the command from the
 *	previous namespace, this function returns the Tcl_Command token in the
 *	first namespace, a. Otherwise, if the specified command is not an
 *	imported command, the function returns NULL.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_Command
TclGetOriginalCommand(
    Tcl_Command command)	/* The imported command for which the original
				 * command should be returned. */
{
    register Command *cmdPtr = (Command *) command;
    ImportedCmdData *dataPtr;

    if (cmdPtr->deleteProc != DeleteImportedCmd) {
	return NULL;
    }

    while (cmdPtr->deleteProc == DeleteImportedCmd) {
	dataPtr = cmdPtr->objClientData;
	cmdPtr = dataPtr->realCmdPtr;
    }
    return (Tcl_Command) cmdPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * InvokeImportedCmd --
 *
 *	Invoked by Tcl whenever the user calls an imported command that was
 *	created by Tcl_Import. Finds the "real" command (in another
 *	namespace), and passes control to it.
 *
 * Results:
 *	Returns TCL_OK if successful, and TCL_ERROR if anything goes wrong.
 *
 * Side effects:
 *	Returns a result in the interpreter's result object. If anything goes
 *	wrong, the result object is set to an error message.
 *
 *----------------------------------------------------------------------
 */

static int
InvokeImportedCmd(
    ClientData clientData,	/* Points to the imported command's
				 * ImportedCmdData structure. */
    Tcl_Interp *interp,		/* Current interpreter. */
    int objc,			/* Number of arguments. */
    Tcl_Obj *const objv[])	/* The argument objects. */
{
    register ImportedCmdData *dataPtr = clientData;
    register Command *realCmdPtr = dataPtr->realCmdPtr;

    return (*realCmdPtr->objProc)(realCmdPtr->objClientData, interp,
	    objc, objv);
}

/*
 *----------------------------------------------------------------------
 *
 * DeleteImportedCmd --
 *
 *	Invoked by Tcl whenever an imported command is deleted. The "real"
 *	command keeps a list of all the imported commands that refer to it, so
 *	those imported commands can be deleted when the real command is
 *	deleted. This function removes the imported command reference from the
 *	real command's list, and frees up the memory associated with the
 *	imported command.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Removes the imported command from the real command's import list.
 *
 *----------------------------------------------------------------------
 */

static void
DeleteImportedCmd(
    ClientData clientData)	/* Points to the imported command's
				 * ImportedCmdData structure. */
{
    ImportedCmdData *dataPtr = clientData;
    Command *realCmdPtr = dataPtr->realCmdPtr;
    Command *selfPtr = dataPtr->selfPtr;
    register ImportRef *refPtr, *prevPtr;

    prevPtr = NULL;
    for (refPtr = realCmdPtr->importRefPtr; refPtr != NULL;
	    refPtr = refPtr->nextPtr) {
	if (refPtr->importedCmdPtr == selfPtr) {
	    /*
	     * Remove *refPtr from real command's list of imported commands
	     * that refer to it.
	     */

	    if (prevPtr == NULL) { /* refPtr is first in list. */
		realCmdPtr->importRefPtr = refPtr->nextPtr;
	    } else {
		prevPtr->nextPtr = refPtr->nextPtr;
	    }
	    ckfree((char *) refPtr);
	    ckfree((char *) dataPtr);
	    return;
	}
	prevPtr = refPtr;
    }

    Tcl_Panic("DeleteImportedCmd: did not find cmd in real cmd's list of import references");
}

/*
 *----------------------------------------------------------------------
 *
 * TclGetNamespaceForQualName --
 *
 *	Given a qualified name specifying a command, variable, or namespace,
 *	and a namespace in which to resolve the name, this function returns a
 *	pointer to the namespace that contains the item. A qualified name
 *	consists of the "simple" name of an item qualified by the names of an
 *	arbitrary number of containing namespace separated by "::"s. If the
 *	qualified name starts with "::", it is interpreted absolutely from the
 *	global namespace. Otherwise, it is interpreted relative to the
 *	namespace specified by cxtNsPtr if it is non-NULL. If cxtNsPtr is
 *	NULL, the name is interpreted relative to the current namespace.
 *
 *	A relative name like "foo::bar::x" can be found starting in either the
 *	current namespace or in the global namespace. So each search usually
 *	follows two tracks, and two possible namespaces are returned. If the
 *	function sets either *nsPtrPtr or *altNsPtrPtr to NULL, then that path
 *	failed.
 *
 *	If "flags" contains TCL_GLOBAL_ONLY, the relative qualified name is
 *	sought only in the global :: namespace. The alternate search (also)
 *	starting from the global namespace is ignored and *altNsPtrPtr is set
 *	NULL.
 *
 *	If "flags" contains TCL_NAMESPACE_ONLY, the relative qualified name is
 *	sought only in the namespace specified by cxtNsPtr. The alternate
 *	search starting from the global namespace is ignored and *altNsPtrPtr
 *	is set NULL. If both TCL_GLOBAL_ONLY and TCL_NAMESPACE_ONLY are
 *	specified, TCL_GLOBAL_ONLY is ignored and the search starts from the
 *	namespace specified by cxtNsPtr.
 *
 *	If "flags" contains TCL_CREATE_NS_IF_UNKNOWN, all namespace components
 *	of the qualified name that cannot be found are automatically created
 *	within their specified parent. This makes sure that functions like
 *	Tcl_CreateCommand always succeed. There is no alternate search path,
 *	so *altNsPtrPtr is set NULL.
 *
 *	If "flags" contains TCL_FIND_ONLY_NS, the qualified name is treated as
 *	a reference to a namespace, and the entire qualified name is followed.
 *	If the name is relative, the namespace is looked up only in the
 *	current namespace. A pointer to the namespace is stored in *nsPtrPtr
 *	and NULL is stored in *simpleNamePtr. Otherwise, if TCL_FIND_ONLY_NS
 *	is not specified, only the leading components are treated as namespace
 *	names, and a pointer to the simple name of the final component is
 *	stored in *simpleNamePtr.
 *
 * Results:
 *	It sets *nsPtrPtr and *altNsPtrPtr to point to the two possible
 *	namespaces which represent the last (containing) namespace in the
 *	qualified name. If the function sets either *nsPtrPtr or *altNsPtrPtr
 *	to NULL, then the search along that path failed. The function also
 *	stores a pointer to the simple name of the final component in
 *	*simpleNamePtr. If the qualified name is "::" or was treated as a
 *	namespace reference (TCL_FIND_ONLY_NS), the function stores a pointer
 *	to the namespace in *nsPtrPtr, NULL in *altNsPtrPtr, and sets
 *	*simpleNamePtr to point to an empty string.
 *
 *	If there is an error, this function returns TCL_ERROR. If "flags"
 *	contains TCL_LEAVE_ERR_MSG, an error message is returned in the
 *	interpreter's result object. Otherwise, the interpreter's result
 *	object is left unchanged.
 *
 *	*actualCxtPtrPtr is set to the actual context namespace. It is set to
 *	the input context namespace pointer in cxtNsPtr. If cxtNsPtr is NULL,
 *	it is set to the current namespace context.
 *
 *	For backwards compatibility with the TclPro byte code loader, this
 *	function always returns TCL_OK.
 *
 * Side effects:
 *	If "flags" contains TCL_CREATE_NS_IF_UNKNOWN, new namespaces may be
 *	created.
 *
 *----------------------------------------------------------------------
 */

int
TclGetNamespaceForQualName(
    Tcl_Interp *interp,		/* Interpreter in which to find the namespace
				 * containing qualName. */
    const char *qualName,	/* A namespace-qualified name of an command,
				 * variable, or namespace. */
    Namespace *cxtNsPtr,	/* The namespace in which to start the search
				 * for qualName's namespace. If NULL start
				 * from the current namespace. Ignored if
				 * TCL_GLOBAL_ONLY is set. */
    int flags,			/* Flags controlling the search: an OR'd
				 * combination of TCL_GLOBAL_ONLY,
				 * TCL_NAMESPACE_ONLY, TCL_FIND_ONLY_NS, and
				 * TCL_CREATE_NS_IF_UNKNOWN. */
    Namespace **nsPtrPtr,	/* Address where function stores a pointer to
				 * containing namespace if qualName is found
				 * starting from *cxtNsPtr or, if
				 * TCL_GLOBAL_ONLY is set, if qualName is
				 * found in the global :: namespace. NULL is
				 * stored otherwise. */
    Namespace **altNsPtrPtr,	/* Address where function stores a pointer to
				 * containing namespace if qualName is found
				 * starting from the global :: namespace.
				 * NULL is stored if qualName isn't found
				 * starting from :: or if the TCL_GLOBAL_ONLY,
				 * TCL_NAMESPACE_ONLY, TCL_FIND_ONLY_NS,
				 * TCL_CREATE_NS_IF_UNKNOWN flag is set. */
    Namespace **actualCxtPtrPtr,/* Address where function stores a pointer to
				 * the actual namespace from which the search
				 * started. This is either cxtNsPtr, the ::
				 * namespace if TCL_GLOBAL_ONLY was specified,
				 * or the current namespace if cxtNsPtr was
				 * NULL. */
    const char **simpleNamePtr) /* Address where function stores the simple
				 * name at end of the qualName, or NULL if
				 * qualName is "::" or the flag
				 * TCL_FIND_ONLY_NS was specified. */
{
    Interp *iPtr = (Interp *) interp;
    Namespace *nsPtr = cxtNsPtr;
    Namespace *altNsPtr;
    Namespace *globalNsPtr = iPtr->globalNsPtr;
    const char *start, *end;
    const char *nsName;
    Tcl_HashEntry *entryPtr;
    Tcl_DString buffer;
    int len;

    /*
     * Determine the context namespace nsPtr in which to start the primary
     * search. If the qualName name starts with a "::" or TCL_GLOBAL_ONLY was
     * specified, search from the global namespace. Otherwise, use the
     * namespace given in cxtNsPtr, or if that is NULL, use the current
     * namespace context. Note that we always treat two or more adjacent ":"s
     * as a namespace separator.
     */

    if (flags & TCL_GLOBAL_ONLY) {
	nsPtr = globalNsPtr;
    } else if (nsPtr == NULL) {
	nsPtr = iPtr->varFramePtr->nsPtr;
    }

    start = qualName;			/* Points to start of qualifying
					 * namespace. */
    if ((*qualName == ':') && (*(qualName+1) == ':')) {
	start = qualName+2;		/* Skip over the initial :: */
	while (*start == ':') {
	    start++;			/* Skip over a subsequent : */
	}
	nsPtr = globalNsPtr;
	if (*start == '\0') {		/* qualName is just two or more
					 * ":"s. */
	    *nsPtrPtr = globalNsPtr;
	    *altNsPtrPtr = NULL;
	    *actualCxtPtrPtr = globalNsPtr;
	    *simpleNamePtr = start;	/* Points to empty string. */
	    return TCL_OK;
	}
    }
    *actualCxtPtrPtr = nsPtr;

    /*
     * Start an alternate search path starting with the global namespace.
     * However, if the starting context is the global namespace, or if the
     * flag is set to search only the namespace *cxtNsPtr, ignore the
     * alternate search path.
     */

    altNsPtr = globalNsPtr;
    if ((nsPtr == globalNsPtr)
	    || (flags & (TCL_NAMESPACE_ONLY | TCL_FIND_ONLY_NS))) {
	altNsPtr = NULL;
    }

    /*
     * Loop to resolve each namespace qualifier in qualName.
     */

    Tcl_DStringInit(&buffer);
    end = start;
    while (*start != '\0') {
	/*
	 * Find the next namespace qualifier (i.e., a name ending in "::") or
	 * the end of the qualified name (i.e., a name ending in "\0"). Set
	 * len to the number of characters, starting from start, in the name;
	 * set end to point after the "::"s or at the "\0".
	 */

	len = 0;
	for (end = start;  *end != '\0';  end++) {
	    if ((*end == ':') && (*(end+1) == ':')) {
		end += 2;		/* Skip over the initial :: */
		while (*end == ':') {
		    end++;		/* Skip over the subsequent : */
		}
		break;			/* Exit for loop; end is after ::'s */
	    }
	    len++;
	}

	if (*end=='\0' && !(end-start>=2 && *(end-1)==':' && *(end-2)==':')) {
	    /*
	     * qualName ended with a simple name at start. If TCL_FIND_ONLY_NS
	     * was specified, look this up as a namespace. Otherwise, start is
	     * the name of a cmd or var and we are done.
	     */

	    if (flags & TCL_FIND_ONLY_NS) {
		nsName = start;
	    } else {
		*nsPtrPtr = nsPtr;
		*altNsPtrPtr = altNsPtr;
		*simpleNamePtr = start;
		Tcl_DStringFree(&buffer);
		return TCL_OK;
	    }
	} else {
	    /*
	     * start points to the beginning of a namespace qualifier ending
	     * in "::". end points to the start of a name in that namespace
	     * that might be empty. Copy the namespace qualifier to a buffer
	     * so it can be null terminated. We can't modify the incoming
	     * qualName since it may be a string constant.
	     */

	    Tcl_DStringSetLength(&buffer, 0);
	    Tcl_DStringAppend(&buffer, start, len);
	    nsName = Tcl_DStringValue(&buffer);
	}

	/*
	 * Look up the namespace qualifier nsName in the current namespace
	 * context. If it isn't found but TCL_CREATE_NS_IF_UNKNOWN is set,
	 * create that qualifying namespace. This is needed for functions like
	 * Tcl_CreateCommand that cannot fail.
	 */

	if (nsPtr != NULL) {
	    entryPtr = Tcl_FindHashEntry(&nsPtr->childTable, nsName);
	    if (entryPtr != NULL) {
		nsPtr = Tcl_GetHashValue(entryPtr);
	    } else if (flags & TCL_CREATE_NS_IF_UNKNOWN) {
		Tcl_CallFrame *framePtr;

		(void) TclPushStackFrame(interp, &framePtr,
			(Tcl_Namespace *) nsPtr, /*isProcCallFrame*/ 0);

		nsPtr = (Namespace *) Tcl_CreateNamespace(interp, nsName,
			NULL, NULL);
		TclPopStackFrame(interp);

		if (nsPtr == NULL) {
		    Tcl_Panic("Could not create namespace '%s'", nsName);
		}
	    } else {			/* Namespace not found and was not
					 * created. */
		nsPtr = NULL;
	    }
	}

	/*
	 * Look up the namespace qualifier in the alternate search path too.
	 */

	if (altNsPtr != NULL) {
	    entryPtr = Tcl_FindHashEntry(&altNsPtr->childTable, nsName);
	    if (entryPtr != NULL) {
		altNsPtr = Tcl_GetHashValue(entryPtr);
	    } else {
		altNsPtr = NULL;
	    }
	}

	/*
	 * If both search paths have failed, return NULL results.
	 */

	if ((nsPtr == NULL) && (altNsPtr == NULL)) {
	    *nsPtrPtr = NULL;
	    *altNsPtrPtr = NULL;
	    *simpleNamePtr = NULL;
	    Tcl_DStringFree(&buffer);
	    return TCL_OK;
	}

	start = end;
    }

    /*
     * We ignore trailing "::"s in a namespace name, but in a command or
     * variable name, trailing "::"s refer to the cmd or var named {}.
     */

    if ((flags & TCL_FIND_ONLY_NS) || (end>start && *(end-1)!=':')) {
	*simpleNamePtr = NULL;		/* Found namespace name. */
    } else {
	*simpleNamePtr = end;		/* Found cmd/var: points to empty
					 * string. */
    }

    /*
     * As a special case, if we are looking for a namespace and qualName is ""
     * and the current active namespace (nsPtr) is not the global namespace,
     * return NULL (no namespace was found). This is because namespaces can
     * not have empty names except for the global namespace.
     */

    if ((flags & TCL_FIND_ONLY_NS) && (*qualName == '\0')
	    && (nsPtr != globalNsPtr)) {
	nsPtr = NULL;
    }

    *nsPtrPtr = nsPtr;
    *altNsPtrPtr = altNsPtr;
    Tcl_DStringFree(&buffer);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_FindNamespace --
 *
 *	Searches for a namespace.
 *
 * Results:
 *	Returns a pointer to the namespace if it is found. Otherwise, returns
 *	NULL and leaves an error message in the interpreter's result object if
 *	"flags" contains TCL_LEAVE_ERR_MSG.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_Namespace *
Tcl_FindNamespace(
    Tcl_Interp *interp,		/* The interpreter in which to find the
				 * namespace. */
    const char *name,		/* Namespace name. If it starts with "::",
				 * will be looked up in global namespace.
				 * Else, looked up first in contextNsPtr
				 * (current namespace if contextNsPtr is
				 * NULL), then in global namespace. */
    Tcl_Namespace *contextNsPtr,/* Ignored if TCL_GLOBAL_ONLY flag is set or
				 * if the name starts with "::". Otherwise,
				 * points to namespace in which to resolve
				 * name; if NULL, look up name in the current
				 * namespace. */
    register int flags)		/* Flags controlling namespace lookup: an OR'd
				 * combination of TCL_GLOBAL_ONLY and
				 * TCL_LEAVE_ERR_MSG flags. */
{
    Namespace *nsPtr, *dummy1Ptr, *dummy2Ptr;
    const char *dummy;

    /*
     * Find the namespace(s) that contain the specified namespace name. Add
     * the TCL_FIND_ONLY_NS flag to resolve the name all the way down to its
     * last component, a namespace.
     */

    TclGetNamespaceForQualName(interp, name, (Namespace *) contextNsPtr,
	    flags|TCL_FIND_ONLY_NS, &nsPtr, &dummy1Ptr, &dummy2Ptr, &dummy);

    if (nsPtr != NULL) {
	return (Tcl_Namespace *) nsPtr;
    } else if (flags & TCL_LEAVE_ERR_MSG) {
	Tcl_ResetResult(interp);
	Tcl_AppendResult(interp, "unknown namespace \"", name, "\"", NULL);
	Tcl_SetErrorCode(interp, "TCL", "LOOKUP", "NAMESPACE", name, NULL);
    }
    return NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_FindCommand --
 *
 *	Searches for a command.
 *
 * Results:
 *	Returns a token for the command if it is found. Otherwise, if it can't
 *	be found or there is an error, returns NULL and leaves an error
 *	message in the interpreter's result object if "flags" contains
 *	TCL_LEAVE_ERR_MSG.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_Command
Tcl_FindCommand(
    Tcl_Interp *interp,		/* The interpreter in which to find the
				 * command and to report errors. */
    const char *name,		/* Command's name. If it starts with "::",
				 * will be looked up in global namespace.
				 * Else, looked up first in contextNsPtr
				 * (current namespace if contextNsPtr is
				 * NULL), then in global namespace. */
    Tcl_Namespace *contextNsPtr,/* Ignored if TCL_GLOBAL_ONLY flag set.
				 * Otherwise, points to namespace in which to
				 * resolve name. If NULL, look up name in the
				 * current namespace. */
    int flags)			/* An OR'd combination of flags:
				 * TCL_GLOBAL_ONLY (look up name only in
				 * global namespace), TCL_NAMESPACE_ONLY (look
				 * up only in contextNsPtr, or the current
				 * namespace if contextNsPtr is NULL), and
				 * TCL_LEAVE_ERR_MSG. If both TCL_GLOBAL_ONLY
				 * and TCL_NAMESPACE_ONLY are given,
				 * TCL_GLOBAL_ONLY is ignored. */
{
    Interp *iPtr = (Interp *) interp;
    Namespace *cxtNsPtr;
    register Tcl_HashEntry *entryPtr;
    register Command *cmdPtr;
    const char *simpleName;
    int result;

    /*
     * If this namespace has a command resolver, then give it first crack at
     * the command resolution. If the interpreter has any command resolvers,
     * consult them next. The command resolver functions may return a
     * Tcl_Command value, they may signal to continue onward, or they may
     * signal an error.
     */

    if ((flags & TCL_GLOBAL_ONLY) || !strncmp(name, "::", 2)) {
	cxtNsPtr = (Namespace *) TclGetGlobalNamespace(interp);
    } else if (contextNsPtr != NULL) {
	cxtNsPtr = (Namespace *) contextNsPtr;
    } else {
	cxtNsPtr = (Namespace *) TclGetCurrentNamespace(interp);
    }

    if (cxtNsPtr->cmdResProc != NULL || iPtr->resolverPtr != NULL) {
	ResolverScheme *resPtr = iPtr->resolverPtr;
	Tcl_Command cmd;

	if (cxtNsPtr->cmdResProc) {
	    result = (*cxtNsPtr->cmdResProc)(interp, name,
		    (Tcl_Namespace *) cxtNsPtr, flags, &cmd);
	} else {
	    result = TCL_CONTINUE;
	}

	while (result == TCL_CONTINUE && resPtr) {
	    if (resPtr->cmdResProc) {
		result = (*resPtr->cmdResProc)(interp, name,
			(Tcl_Namespace *) cxtNsPtr, flags, &cmd);
	    }
	    resPtr = resPtr->nextPtr;
	}

	if (result == TCL_OK) {
	    return cmd;
	} else if (result != TCL_CONTINUE) {
	    return NULL;
	}
    }

    /*
     * Find the namespace(s) that contain the command.
     */

    cmdPtr = NULL;
    if (cxtNsPtr->commandPathLength!=0 && strncmp(name, "::", 2)) {
	int i;
	Namespace *pathNsPtr, *realNsPtr, *dummyNsPtr;

	(void) TclGetNamespaceForQualName(interp, name, cxtNsPtr,
		TCL_NAMESPACE_ONLY, &realNsPtr, &dummyNsPtr, &dummyNsPtr,
		&simpleName);
	if ((realNsPtr != NULL) && (simpleName != NULL)) {
	    if ((cxtNsPtr == realNsPtr)
		    || !(realNsPtr->flags & NS_DYING)) {
		entryPtr = Tcl_FindHashEntry(&realNsPtr->cmdTable, simpleName);
		if (entryPtr != NULL) {
		    cmdPtr = Tcl_GetHashValue(entryPtr);
		}
	    }
	}

	/*
	 * Next, check along the path.
	 */

	for (i=0 ; i<cxtNsPtr->commandPathLength && cmdPtr==NULL ; i++) {
	    pathNsPtr = cxtNsPtr->commandPathArray[i].nsPtr;
	    if (pathNsPtr == NULL) {
		continue;
	    }
	    (void) TclGetNamespaceForQualName(interp, name, pathNsPtr,
		    TCL_NAMESPACE_ONLY, &realNsPtr, &dummyNsPtr, &dummyNsPtr,
		    &simpleName);
	    if ((realNsPtr != NULL) && (simpleName != NULL)
		    && !(realNsPtr->flags & NS_DYING)) {
		entryPtr = Tcl_FindHashEntry(&realNsPtr->cmdTable, simpleName);
		if (entryPtr != NULL) {
		    cmdPtr = Tcl_GetHashValue(entryPtr);
		}
	    }
	}

	/*
	 * If we've still not found the command, look in the global namespace
	 * as a last resort.
	 */

	if (cmdPtr == NULL) {
	    (void) TclGetNamespaceForQualName(interp, name, NULL,
		    TCL_GLOBAL_ONLY, &realNsPtr, &dummyNsPtr, &dummyNsPtr,
		    &simpleName);
	    if ((realNsPtr != NULL) && (simpleName != NULL)
		    && !(realNsPtr->flags & NS_DYING)) {
		entryPtr = Tcl_FindHashEntry(&realNsPtr->cmdTable, simpleName);
		if (entryPtr != NULL) {
		    cmdPtr = Tcl_GetHashValue(entryPtr);
		}
	    }
	}
    } else {
	Namespace *nsPtr[2];
	register int search;

	TclGetNamespaceForQualName(interp, name, (Namespace *) contextNsPtr,
		flags, &nsPtr[0], &nsPtr[1], &cxtNsPtr, &simpleName);

	/*
	 * Look for the command in the command table of its namespace. Be sure
	 * to check both possible search paths: from the specified namespace
	 * context and from the global namespace.
	 */

	for (search = 0;  (search < 2) && (cmdPtr == NULL);  search++) {
	    if ((nsPtr[search] != NULL) && (simpleName != NULL)) {
		entryPtr = Tcl_FindHashEntry(&nsPtr[search]->cmdTable,
			simpleName);
		if (entryPtr != NULL) {
		    cmdPtr = Tcl_GetHashValue(entryPtr);
		}
	    }
	}
    }

    if (cmdPtr != NULL) {
	return (Tcl_Command) cmdPtr;
    }

    if (flags & TCL_LEAVE_ERR_MSG) {
	Tcl_ResetResult(interp);
	Tcl_AppendResult(interp, "unknown command \"", name, "\"", NULL);
	Tcl_SetErrorCode(interp, "TCL", "LOOKUP", "COMMAND", name, NULL);
    }
    return NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * TclResetShadowedCmdRefs --
 *
 *	Called when a command is added to a namespace to check for existing
 *	command references that the new command may invalidate. Consider the
 *	following cases that could happen when you add a command "foo" to a
 *	namespace "b":
 *	   1. It could shadow a command named "foo" at the global scope. If
 *	      it does, all command references in the namespace "b" are
 *	      suspect.
 *	   2. Suppose the namespace "b" resides in a namespace "a". Then to
 *	      "a" the new command "b::foo" could shadow another command
 *	      "b::foo" in the global namespace. If so, then all command
 *	      references in "a" * are suspect.
 *	The same checks are applied to all parent namespaces, until we reach
 *	the global :: namespace.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	If the new command shadows an existing command, the cmdRefEpoch
 *	counter is incremented in each namespace that sees the shadow. This
 *	invalidates all command references that were previously cached in that
 *	namespace. The next time the commands are used, they are resolved from
 *	scratch.
 *
 *----------------------------------------------------------------------
 */

void
TclResetShadowedCmdRefs(
    Tcl_Interp *interp,		/* Interpreter containing the new command. */
    Command *newCmdPtr)		/* Points to the new command. */
{
    char *cmdName;
    Tcl_HashEntry *hPtr;
    register Namespace *nsPtr;
    Namespace *trailNsPtr, *shadowNsPtr;
    Namespace *globalNsPtr = (Namespace *) TclGetGlobalNamespace(interp);
    int found, i;
    int trailFront = -1;
    int trailSize = 5;		/* Formerly NUM_TRAIL_ELEMS. */
    Namespace **trailPtr = (Namespace **)
	    TclStackAlloc(interp, trailSize * sizeof(Namespace *));

    /*
     * Start at the namespace containing the new command, and work up through
     * the list of parents. Stop just before the global namespace, since the
     * global namespace can't "shadow" its own entries.
     *
     * The namespace "trail" list we build consists of the names of each
     * namespace that encloses the new command, in order from outermost to
     * innermost: for example, "a" then "b". Each iteration of this loop
     * eventually extends the trail upwards by one namespace, nsPtr. We use
     * this trail list to see if nsPtr (e.g. "a" in 2. above) could have
     * now-invalid cached command references. This will happen if nsPtr
     * (e.g. "a") contains a sequence of child namespaces (e.g. "b") such that
     * there is a identically-named sequence of child namespaces starting from
     * :: (e.g. "::b") whose tail namespace contains a command also named
     * cmdName.
     */

    cmdName = Tcl_GetHashKey(newCmdPtr->hPtr->tablePtr, newCmdPtr->hPtr);
    for (nsPtr=newCmdPtr->nsPtr ; (nsPtr!=NULL) && (nsPtr!=globalNsPtr) ;
	    nsPtr=nsPtr->parentPtr) {
	/*
	 * Find the maximal sequence of child namespaces contained in nsPtr
	 * such that there is a identically-named sequence of child namespaces
	 * starting from ::. shadowNsPtr will be the tail of this sequence, or
	 * the deepest namespace under :: that might contain a command now
	 * shadowed by cmdName. We check below if shadowNsPtr actually
	 * contains a command cmdName.
	 */

	found = 1;
	shadowNsPtr = globalNsPtr;

	for (i = trailFront;  i >= 0;  i--) {
	    trailNsPtr = trailPtr[i];
	    hPtr = Tcl_FindHashEntry(&shadowNsPtr->childTable,
		    trailNsPtr->name);
	    if (hPtr != NULL) {
		shadowNsPtr = Tcl_GetHashValue(hPtr);
	    } else {
		found = 0;
		break;
	    }
	}

	/*
	 * If shadowNsPtr contains a command named cmdName, we invalidate all
	 * of the command refs cached in nsPtr. As a boundary case,
	 * shadowNsPtr is initially :: and we check for case 1. above.
	 */

	if (found) {
	    hPtr = Tcl_FindHashEntry(&shadowNsPtr->cmdTable, cmdName);
	    if (hPtr != NULL) {
		nsPtr->cmdRefEpoch++;
		TclInvalidateNsPath(nsPtr);

		/*
		 * If the shadowed command was compiled to bytecodes, we
		 * invalidate all the bytecodes in nsPtr, to force a new
		 * compilation. We use the resolverEpoch to signal the need
		 * for a fresh compilation of every bytecode.
		 */

		if (((Command *)Tcl_GetHashValue(hPtr))->compileProc != NULL) {
		    nsPtr->resolverEpoch++;
		}
	    }
	}

	/*
	 * Insert nsPtr at the front of the trail list: i.e., at the end of
	 * the trailPtr array.
	 */

	trailFront++;
	if (trailFront == trailSize) {
	    int newSize = 2 * trailSize;
	    trailPtr = (Namespace **) TclStackRealloc(interp,
		    trailPtr, newSize * sizeof(Namespace *));
	    trailSize = newSize;
	}
	trailPtr[trailFront] = nsPtr;
    }
    TclStackFree(interp, trailPtr);
}

/*
 *----------------------------------------------------------------------
 *
 * TclGetNamespaceFromObj, GetNamespaceFromObj --
 *
 *	Gets the namespace specified by the name in a Tcl_Obj.
 *
 * Results:
 *	Returns TCL_OK if the namespace was resolved successfully, and stores
 *	a pointer to the namespace in the location specified by nsPtrPtr. If
 *	the namespace can't be found, or anything else goes wrong, this
 *	function returns TCL_ERROR and writes an error message to interp,
 *	if non-NULL.
 *
 * Side effects:
 *	May update the internal representation for the object, caching the
 *	namespace reference. The next time this function is called, the
 *	namespace value can be found quickly.
 *
 *----------------------------------------------------------------------
 */

int
TclGetNamespaceFromObj(
    Tcl_Interp *interp,		/* The current interpreter. */
    Tcl_Obj *objPtr,		/* The object to be resolved as the name of a
				 * namespace. */
    Tcl_Namespace **nsPtrPtr)	/* Result namespace pointer goes here. */
{
    if (GetNamespaceFromObj(interp, objPtr, nsPtrPtr) == TCL_ERROR) {
	const char *name = TclGetString(objPtr);

	if ((name[0] == ':') && (name[1] == ':')) {
	    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
		    "namespace \"%s\" not found", name));
	} else {
	    /*
	     * Get the current namespace name.
	     */

	    NamespaceCurrentCmd(NULL, interp, 2, NULL);
	    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
		    "namespace \"%s\" not found in \"%s\"", name,
		    Tcl_GetStringResult(interp)));
	}
	Tcl_SetErrorCode(interp, "TCL", "LOOKUP", "NAMESPACE", name, NULL);
	return TCL_ERROR;
    }
    return TCL_OK;
}

static int
GetNamespaceFromObj(
    Tcl_Interp *interp,		/* The current interpreter. */
    Tcl_Obj *objPtr,		/* The object to be resolved as the name of a
				 * namespace. */
    Tcl_Namespace **nsPtrPtr)	/* Result namespace pointer goes here. */
{
    ResolvedNsName *resNamePtr;
    Namespace *nsPtr, *refNsPtr;

    if (objPtr->typePtr == &nsNameType) {
	/*
	 * Check that the ResolvedNsName is still valid; avoid letting the ref 
	 * cross interps.
	 */

	resNamePtr = (ResolvedNsName *) objPtr->internalRep.twoPtrValue.ptr1;
	nsPtr = resNamePtr->nsPtr;
	refNsPtr = resNamePtr->refNsPtr;
	if (!(nsPtr->flags & NS_DYING) && (interp == nsPtr->interp) &&
		(!refNsPtr || ((interp == refNsPtr->interp) &&
		 (refNsPtr== (Namespace *) Tcl_GetCurrentNamespace(interp))))) {
	    *nsPtrPtr = (Tcl_Namespace *) nsPtr;
	    return TCL_OK;
	}
    }
    if (SetNsNameFromAny(interp, objPtr) == TCL_OK) {
	resNamePtr = (ResolvedNsName *) objPtr->internalRep.twoPtrValue.ptr1;
	*nsPtrPtr = (Tcl_Namespace *) resNamePtr->nsPtr;
	return TCL_OK;
    }
    return TCL_ERROR;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_NamespaceObjCmd --
 *
 *	Invoked to implement the "namespace" command that creates, deletes, or
 *	manipulates Tcl namespaces. Handles the following syntax:
 *
 *	    namespace children ?name? ?pattern?
 *	    namespace code arg
 *	    namespace current
 *	    namespace delete ?name name...?
 *	    namespace ensemble subcommand ?arg...?
 *	    namespace eval name arg ?arg...?
 *	    namespace exists name
 *	    namespace export ?-clear? ?pattern pattern...?
 *	    namespace forget ?pattern pattern...?
 *	    namespace import ?-force? ?pattern pattern...?
 *	    namespace inscope name arg ?arg...?
 *	    namespace origin name
 *	    namespace parent ?name?
 *	    namespace qualifiers string
 *	    namespace tail string
 *	    namespace which ?-command? ?-variable? name
 *
 * Results:
 *	Returns TCL_OK if the command is successful. Returns TCL_ERROR if
 *	anything goes wrong.
 *
 * Side effects:
 *	Based on the subcommand name (e.g., "import"), this function
 *	dispatches to a corresponding function NamespaceXXXCmd defined
 *	statically in this file. This function's side effects depend on
 *	whatever that subcommand function does. If there is an error, this
 *	function returns an error message in the interpreter's result object.
 *	Otherwise it may return a result in the interpreter's result object.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_NamespaceObjCmd(
    ClientData clientData,	/* Arbitrary value passed to cmd. */
    Tcl_Interp *interp,		/* Current interpreter. */
    int objc,			/* Number of arguments. */
    Tcl_Obj *const objv[])	/* Argument objects. */
{
    static const char *subCmds[] = {
	"children", "code", "current", "delete", "ensemble",
	"eval", "exists", "export", "forget", "import",
	"inscope", "origin", "parent", "path", "qualifiers",
	"tail", "unknown", "upvar", "which", NULL
    };
    enum NSSubCmdIdx {
	NSChildrenIdx, NSCodeIdx, NSCurrentIdx, NSDeleteIdx, NSEnsembleIdx,
	NSEvalIdx, NSExistsIdx, NSExportIdx, NSForgetIdx, NSImportIdx,
	NSInscopeIdx, NSOriginIdx, NSParentIdx, NSPathIdx, NSQualifiersIdx,
	NSTailIdx, NSUnknownIdx, NSUpvarIdx, NSWhichIdx
    };
    int index, result;

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

    /*
     * Return an index reflecting the particular subcommand.
     */

    result = Tcl_GetIndexFromObj((Tcl_Interp *) interp, objv[1], subCmds,
	    "option", /*flags*/ 0, (int *) &index);
    if (result != TCL_OK) {
	return result;
    }

    switch (index) {
    case NSChildrenIdx:
	result = NamespaceChildrenCmd(clientData, interp, objc, objv);
	break;
    case NSCodeIdx:

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