Import Micropolis from http://www.donhopkins.com/home/micropolis/

[micropolis] / src / tcl / tclbasic.c

/* 
 * tclBasic.c --
 *
 *      Contains the basic facilities for TCL command interpretation,
 *      including interpreter creation and deletion, command creation
 *      and deletion, and command parsing and execution.
 *
 * Copyright 1987-1992 Regents of the University of California
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies.  The University of California
 * makes no representations about the suitability of this
 * software for any purpose.  It is provided "as is" without
 * express or implied warranty.
 */

#ifndef lint
static char rcsid[] = "$Header: /user6/ouster/tcl/RCS/tclBasic.c,v 1.131 92/06/21 14:09:41 ouster Exp $ SPRITE (Berkeley)";
#endif

#include "tclint.h"

/*
 * The following structure defines all of the commands in the Tcl core,
 * and the C procedures that execute them.
 */

typedef struct {
    char *name;                 /* Name of command. */
    Tcl_CmdProc *proc;          /* Procedure that executes command. */
} CmdInfo;

/*
 * Built-in commands, and the procedures associated with them:
 */

static CmdInfo builtInCmds[] = {
    /*
     * Commands in the generic core:
     */

    {"append",          Tcl_AppendCmd},
    {"array",           Tcl_ArrayCmd},
    {"break",           Tcl_BreakCmd},
    {"case",            Tcl_CaseCmd},
    {"catch",           Tcl_CatchCmd},
    {"concat",          Tcl_ConcatCmd},
    {"continue",        Tcl_ContinueCmd},
    {"error",           Tcl_ErrorCmd},
    {"eval",            Tcl_EvalCmd},
    {"expr",            Tcl_ExprCmd},
    {"for",             Tcl_ForCmd},
    {"foreach",         Tcl_ForeachCmd},
    {"format",          Tcl_FormatCmd},
    {"global",          Tcl_GlobalCmd},
    {"if",              Tcl_IfCmd},
    {"incr",            Tcl_IncrCmd},
    {"info",            Tcl_InfoCmd},
    {"join",            Tcl_JoinCmd},
    {"lappend",         Tcl_LappendCmd},
    {"lindex",          Tcl_LindexCmd},
    {"linsert",         Tcl_LinsertCmd},
    {"list",            Tcl_ListCmd},
    {"llength",         Tcl_LlengthCmd},
    {"lrange",          Tcl_LrangeCmd},
    {"lreplace",        Tcl_LreplaceCmd},
    {"lsearch",         Tcl_LsearchCmd},
    {"lsort",           Tcl_LsortCmd},
    {"proc",            Tcl_ProcCmd},
    {"regexp",          Tcl_RegexpCmd},
    {"regsub",          Tcl_RegsubCmd},
    {"rename",          Tcl_RenameCmd},
    {"return",          Tcl_ReturnCmd},
    {"scan",            Tcl_ScanCmd},
    {"set",             Tcl_SetCmd},
    {"split",           Tcl_SplitCmd},
    {"string",          Tcl_StringCmd},
    {"trace",           Tcl_TraceCmd},
    {"unset",           Tcl_UnsetCmd},
    {"uplevel",         Tcl_UplevelCmd},
    {"upvar",           Tcl_UpvarCmd},
    {"while",           Tcl_WhileCmd},

    /*
     * Commands in the UNIX core:
     */

#ifndef TCL_GENERIC_ONLY
    {"cd",              Tcl_CdCmd},
    {"close",           Tcl_CloseCmd},
    {"eof",             Tcl_EofCmd},
    {"exec",            Tcl_ExecCmd},
    {"exit",            Tcl_ExitCmd},
    {"file",            Tcl_FileCmd},
    {"flush",           Tcl_FlushCmd},
    {"gets",            Tcl_GetsCmd},
    {"glob",            Tcl_GlobCmd},
    {"open",            Tcl_OpenCmd},
    {"puts",            Tcl_PutsCmd},
    {"pwd",             Tcl_PwdCmd},
    {"read",            Tcl_ReadCmd},
    {"seek",            Tcl_SeekCmd},
    {"source",          Tcl_SourceCmd},
    {"tell",            Tcl_TellCmd},
    {"time",            Tcl_TimeCmd},
#endif /* TCL_GENERIC_ONLY */
    {NULL,              (Tcl_CmdProc *) NULL}
};
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_CreateInterp --
 *
 *      Create a new TCL command interpreter.
 *
 * Results:
 *      The return value is a token for the interpreter, which may be
 *      used in calls to procedures like Tcl_CreateCmd, Tcl_Eval, or
 *      Tcl_DeleteInterp.
 *
 * Side effects:
 *      The command interpreter is initialized with an empty variable
 *      table and the built-in commands.
 *
 *----------------------------------------------------------------------
 */

Tcl_Interp *
Tcl_CreateInterp()
{
    register Interp *iPtr;
    register Command *cmdPtr;
    register CmdInfo *cmdInfoPtr;
    int i;

    iPtr = (Interp *) ckalloc(sizeof(Interp));
    iPtr->result = iPtr->resultSpace;
    iPtr->freeProc = 0;
    iPtr->errorLine = 0;
    Tcl_InitHashTable(&iPtr->commandTable, TCL_STRING_KEYS);
    Tcl_InitHashTable(&iPtr->globalTable, TCL_STRING_KEYS);
    iPtr->numLevels = 0;
    iPtr->framePtr = NULL;
    iPtr->varFramePtr = NULL;
    iPtr->activeTracePtr = NULL;
    iPtr->numEvents = 0;
    iPtr->events = NULL;
    iPtr->curEvent = 0;
    iPtr->curEventNum = 0;
    iPtr->revPtr = NULL;
    iPtr->historyFirst = NULL;
    iPtr->revDisables = 1;
    iPtr->evalFirst = iPtr->evalLast = NULL;
    iPtr->appendResult = NULL;
    iPtr->appendAvl = 0;
    iPtr->appendUsed = 0;
    iPtr->numFiles = 0;
    iPtr->filePtrArray = NULL;
    for (i = 0; i < NUM_REGEXPS; i++) {
        iPtr->patterns[i] = NULL;
        iPtr->patLengths[i] = -1;
        iPtr->regexps[i] = NULL;
    }
    iPtr->cmdCount = 0;
    iPtr->noEval = 0;
    iPtr->scriptFile = NULL;
    iPtr->flags = 0;
    iPtr->tracePtr = NULL;
    iPtr->resultSpace[0] = 0;

    /*
     * Create the built-in commands.  Do it here, rather than calling
     * Tcl_CreateCommand, because it's faster (there's no need to
     * check for a pre-existing command by the same name).
     */

    for (cmdInfoPtr = builtInCmds; cmdInfoPtr->name != NULL; cmdInfoPtr++) {
        int new;
        Tcl_HashEntry *hPtr;

        hPtr = Tcl_CreateHashEntry(&iPtr->commandTable,
                cmdInfoPtr->name, &new);
        if (new) {
            cmdPtr = (Command *) ckalloc(sizeof(Command));
            cmdPtr->proc = cmdInfoPtr->proc;
            cmdPtr->clientData = (ClientData) NULL;
            cmdPtr->deleteProc = NULL;
            Tcl_SetHashValue(hPtr, cmdPtr);
        }
    }

#ifndef TCL_GENERIC_ONLY
    TclSetupEnv((Tcl_Interp *) iPtr);
#endif

    return (Tcl_Interp *) iPtr;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_DeleteInterp --
 *
 *      Delete an interpreter and free up all of the resources associated
 *      with it.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      The interpreter is destroyed.  The caller should never again
 *      use the interp token.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_DeleteInterp(interp)
    Tcl_Interp *interp;         /* Token for command interpreter (returned
                                 * by a previous call to Tcl_CreateInterp). */
{
    Interp *iPtr = (Interp *) interp;
    Tcl_HashEntry *hPtr;
    Tcl_HashSearch search;
    register Command *cmdPtr;
    int i;

    /*
     * If the interpreter is in use, delay the deletion until later.
     */

    iPtr->flags |= DELETED;
    if (iPtr->numLevels != 0) {
        return;
    }

    /*
     * Free up any remaining resources associated with the
     * interpreter.
     */

    for (hPtr = Tcl_FirstHashEntry(&iPtr->commandTable, &search);
            hPtr != NULL; hPtr = Tcl_NextHashEntry(&search)) {
        cmdPtr = (Command *) Tcl_GetHashValue(hPtr);
        if (cmdPtr->deleteProc != NULL) { 
            (*cmdPtr->deleteProc)(cmdPtr->clientData);
        }
        ckfree((char *) cmdPtr);
    }
    Tcl_DeleteHashTable(&iPtr->commandTable);
    TclDeleteVars(iPtr, &iPtr->globalTable);
    if (iPtr->events != NULL) {
        int i;

        for (i = 0; i < iPtr->numEvents; i++) {
            ckfree(iPtr->events[i].command);
        }
        ckfree((char *) iPtr->events);
    }
    while (iPtr->revPtr != NULL) {
        HistoryRev *nextPtr = iPtr->revPtr->nextPtr;

        ckfree((char *) iPtr->revPtr);
        iPtr->revPtr = nextPtr;
    }
    if (iPtr->appendResult != NULL) {
        ckfree(iPtr->appendResult);
    }
#ifndef TCL_GENERIC_ONLY
    if (iPtr->numFiles > 0) {
        for (i = 0; i < iPtr->numFiles; i++) {
            OpenFile *filePtr;
    
            filePtr = iPtr->filePtrArray[i];
            if (filePtr == NULL) {
                continue;
            }
            if (i >= 3) {
                fclose(filePtr->f);
                if (filePtr->f2 != NULL) {
                    fclose(filePtr->f2);
                }
                if (filePtr->numPids > 0) {
                    Tcl_DetachPids(filePtr->numPids, filePtr->pidPtr);
                    ckfree((char *) filePtr->pidPtr);
                }
            }
            ckfree((char *) filePtr);
        }
        ckfree((char *) iPtr->filePtrArray);
    }
#endif
    for (i = 0; i < NUM_REGEXPS; i++) {
        if (iPtr->patterns[i] == NULL) {
            break;
        }
        ckfree(iPtr->patterns[i]);
        ckfree((char *) iPtr->regexps[i]);
    }
    while (iPtr->tracePtr != NULL) {
        Trace *nextPtr = iPtr->tracePtr->nextPtr;

        ckfree((char *) iPtr->tracePtr);
        iPtr->tracePtr = nextPtr;
    }
    ckfree((char *) iPtr);
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_CreateCommand --
 *
 *      Define a new command in a command table.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      If a command named cmdName already exists for interp, it is
 *      deleted.  In the future, when cmdName is seen as the name of
 *      a command by Tcl_Eval, proc will be called.  When the command
 *      is deleted from the table, deleteProc will be called.  See the
 *      manual entry for details on the calling sequence.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_CreateCommand(interp, cmdName, proc, clientData, deleteProc)
    Tcl_Interp *interp;         /* Token for command interpreter (returned
                                 * by a previous call to Tcl_CreateInterp). */
    char *cmdName;              /* Name of command. */
    Tcl_CmdProc *proc;          /* Command procedure to associate with
                                 * cmdName. */
    ClientData clientData;      /* Arbitrary one-word value to pass to proc. */
    Tcl_CmdDeleteProc *deleteProc;
                                /* If not NULL, gives a procedure to call when
                                 * this command is deleted. */
{
    Interp *iPtr = (Interp *) interp;
    register Command *cmdPtr;
    Tcl_HashEntry *hPtr;
    int new;

    hPtr = Tcl_CreateHashEntry(&iPtr->commandTable, cmdName, &new);
    if (!new) {
        /*
         * Command already exists:  delete the old one.
         */

        cmdPtr = (Command *) Tcl_GetHashValue(hPtr);
        if (cmdPtr->deleteProc != NULL) {
            (*cmdPtr->deleteProc)(cmdPtr->clientData);
        }
    } else {
        cmdPtr = (Command *) ckalloc(sizeof(Command));
        Tcl_SetHashValue(hPtr, cmdPtr);
    }
    cmdPtr->proc = proc;
    cmdPtr->clientData = clientData;
    cmdPtr->deleteProc = deleteProc;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_DeleteCommand --
 *
 *      Remove the given command from the given interpreter.
 *
 * Results:
 *      0 is returned if the command was deleted successfully.
 *      -1 is returned if there didn't exist a command by that
 *      name.
 *
 * Side effects:
 *      CmdName will no longer be recognized as a valid command for
 *      interp.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_DeleteCommand(interp, cmdName)
    Tcl_Interp *interp;         /* Token for command interpreter (returned
                                 * by a previous call to Tcl_CreateInterp). */
    char *cmdName;              /* Name of command to remove. */
{
    Interp *iPtr = (Interp *) interp;
    Tcl_HashEntry *hPtr;
    Command *cmdPtr;

    hPtr = Tcl_FindHashEntry(&iPtr->commandTable, cmdName);
    if (hPtr == NULL) {
        return -1;
    }
    cmdPtr = (Command *) Tcl_GetHashValue(hPtr);
    if (cmdPtr->deleteProc != NULL) {
        (*cmdPtr->deleteProc)(cmdPtr->clientData);
    }
    ckfree((char *) cmdPtr);
    Tcl_DeleteHashEntry(hPtr);
    return 0;
}
\f
/*
 *-----------------------------------------------------------------
 *
 * Tcl_Eval --
 *
 *      Parse and execute a command in the Tcl language.
 *
 * Results:
 *      The return value is one of the return codes defined in tcl.hd
 *      (such as TCL_OK), and interp->result contains a string value
 *      to supplement the return code.  The value of interp->result
 *      will persist only until the next call to Tcl_Eval:  copy it or
 *      lose it! *TermPtr is filled in with the character just after
 *      the last one that was part of the command (usually a NULL
 *      character or a closing bracket).
 *
 * Side effects:
 *      Almost certainly;  depends on the command.
 *
 *-----------------------------------------------------------------
 */

int
Tcl_Eval(interp, cmd, flags, termPtr)
    Tcl_Interp *interp;         /* Token for command interpreter (returned
                                 * by a previous call to Tcl_CreateInterp). */
    char *cmd;                  /* Pointer to TCL command to interpret. */
    int flags;                  /* OR-ed combination of flags like
                                 * TCL_BRACKET_TERM and TCL_RECORD_BOUNDS. */
    char **termPtr;             /* If non-NULL, fill in the address it points
                                 * to with the address of the char. just after
                                 * the last one that was part of cmd.  See
                                 * the man page for details on this. */
{
    /*
     * The storage immediately below is used to generate a copy
     * of the command, after all argument substitutions.  Pv will
     * contain the argv values passed to the command procedure.
     */

#   define NUM_CHARS 200
    char copyStorage[NUM_CHARS];
    ParseValue pv;
    char *oldBuffer;

    /*
     * This procedure generates an (argv, argc) array for the command,
     * It starts out with stack-allocated space but uses dynamically-
     * allocated storage to increase it if needed.
     */

#   define NUM_ARGS 10
    char *(argStorage[NUM_ARGS]);
    char **argv = argStorage;
    int argc;
    int argSize = NUM_ARGS;

    register char *src;                 /* Points to current character
                                         * in cmd. */
    char termChar;                      /* Return when this character is found
                                         * (either ']' or '\0').  Zero means
                                         * that newlines terminate commands. */
    int result;                         /* Return value. */
    register Interp *iPtr = (Interp *) interp;
    Tcl_HashEntry *hPtr;
    Command *cmdPtr;
    char *dummy;                        /* Make termPtr point here if it was
                                         * originally NULL. */
    char *cmdStart;                     /* Points to first non-blank char. in
                                         * command (used in calling trace
                                         * procedures). */
    char *ellipsis = "";                /* Used in setting errorInfo variable;
                                         * set to "..." to indicate that not
                                         * all of offending command is included
                                         * in errorInfo.  "" means that the
                                         * command is all there. */
    register Trace *tracePtr;

    /*
     * Initialize the result to an empty string and clear out any
     * error information.  This makes sure that we return an empty
     * result if there are no commands in the command string.
     */

    Tcl_FreeResult((Tcl_Interp *) iPtr);
    iPtr->result = iPtr->resultSpace;
    iPtr->resultSpace[0] = 0;
    result = TCL_OK;

    /*
     * Check depth of nested calls to Tcl_Eval:  if this gets too large,
     * it's probably because of an infinite loop somewhere.
     */

    iPtr->numLevels++;
    if (iPtr->numLevels > MAX_NESTING_DEPTH) {
        iPtr->numLevels--;
        iPtr->result =  "too many nested calls to Tcl_Eval (infinite loop?)";
        return TCL_ERROR;
    }

    /*
     * Initialize the area in which command copies will be assembled.
     */

    pv.buffer = copyStorage;
    pv.end = copyStorage + NUM_CHARS - 1;
    pv.expandProc = TclExpandParseValue;
    pv.clientData = (ClientData) NULL;

    src = cmd;
    if (flags & TCL_BRACKET_TERM) {
        termChar = ']';
    } else {
        termChar = 0;
    }
    if (termPtr == NULL) {
        termPtr = &dummy;
    }
    *termPtr = src;
    cmdStart = src;

    /*
     * There can be many sub-commands (separated by semi-colons or
     * newlines) in one command string.  This outer loop iterates over
     * individual commands.
     */

    while (*src != termChar) {
        iPtr->flags &= ~(ERR_IN_PROGRESS | ERROR_CODE_SET);

        /*
         * Skim off leading white space and semi-colons, and skip
         * comments.
         */

        while (1) {
            register char c = *src;

            if ((CHAR_TYPE(c) != TCL_SPACE) && (c != ';') && (c != '\n')) {
                break;
            }
            src += 1;
        }
        if (*src == '#') {
            for (src++; *src != 0; src++) {
                if (*src == '\n') {
                    src++;
                    break;
                }
            }
            continue;
        }
        cmdStart = src;

        /*
         * Parse the words of the command, generating the argc and
         * argv for the command procedure.  May have to call
         * TclParseWords several times, expanding the argv array
         * between calls.
         */

        pv.next = oldBuffer = pv.buffer;
        argc = 0;
        while (1) {
            int newArgs, maxArgs;
            char **newArgv;
            int i;

            /*
             * Note:  the "- 2" below guarantees that we won't use the
             * last two argv slots here.  One is for a NULL pointer to
             * mark the end of the list, and the other is to leave room
             * for inserting the command name "unknown" as the first
             * argument (see below).
             */

            maxArgs = argSize - argc - 2;
            result = TclParseWords((Tcl_Interp *) iPtr, src, flags,
                    maxArgs, termPtr, &newArgs, &argv[argc], &pv);
            src = *termPtr;
            if (result != TCL_OK) {
                ellipsis = "...";
                goto done;
            }

            /*
             * Careful!  Buffer space may have gotten reallocated while
             * parsing words.  If this happened, be sure to update all
             * of the older argv pointers to refer to the new space.
             */

            if (oldBuffer != pv.buffer) {
                int i;

                for (i = 0; i < argc; i++) {
                    argv[i] = pv.buffer + (argv[i] - oldBuffer);
                }
                oldBuffer = pv.buffer;
            }
            argc += newArgs;
            if (newArgs < maxArgs) {
                argv[argc] = (char *) NULL;
                break;
            }

            /*
             * Args didn't all fit in the current array.  Make it bigger.
             */

            argSize *= 2;
            newArgv = (char **)
                    ckalloc((unsigned) argSize * sizeof(char *));
            for (i = 0; i < argc; i++) {
                newArgv[i] = argv[i];
            }
            if (argv != argStorage) {
                ckfree((char *) argv);
            }
            argv = newArgv;
        }

        /*
         * If this is an empty command (or if we're just parsing
         * commands without evaluating them), then just skip to the
         * next command.
         */

        if ((argc == 0) || iPtr->noEval) {
            continue;
        }
        argv[argc] = NULL;

        /*
         * Save information for the history module, if needed.
         */

        if (flags & TCL_RECORD_BOUNDS) {
            iPtr->evalFirst = cmdStart;
            iPtr->evalLast = src-1;
        }

        /*
         * Find the procedure to execute this command.  If there isn't
         * one, then see if there is a command "unknown".  If so,
         * invoke it instead, passing it the words of the original
         * command as arguments.
         */

        hPtr = Tcl_FindHashEntry(&iPtr->commandTable, argv[0]);
        if (hPtr == NULL) {
            int i;

            hPtr = Tcl_FindHashEntry(&iPtr->commandTable, "unknown");
            if (hPtr == NULL) {
                Tcl_ResetResult(interp);
                Tcl_AppendResult(interp, "invalid command name: \"",
                        argv[0], "\"", (char *) NULL);
                result = TCL_ERROR;
                goto done;
            }
            for (i = argc; i >= 0; i--) {
                argv[i+1] = argv[i];
            }
            argv[0] = "unknown";
            argc++;
        }
        cmdPtr = (Command *) Tcl_GetHashValue(hPtr);

        /*
         * Call trace procedures, if any.
         */

        for (tracePtr = iPtr->tracePtr; tracePtr != NULL;
                tracePtr = tracePtr->nextPtr) {
            char saved;

            if (tracePtr->level < iPtr->numLevels) {
                continue;
            }
            saved = *src;
            *src = 0;
            (*tracePtr->proc)(tracePtr->clientData, interp, iPtr->numLevels,
                    cmdStart, cmdPtr->proc, cmdPtr->clientData, argc, argv);
            *src = saved;
        }

        /*
         * At long last, invoke the command procedure.  Reset the
         * result to its default empty value first (it could have
         * gotten changed by earlier commands in the same command
         * string).
         */

        iPtr->cmdCount++;
        Tcl_FreeResult(iPtr);
        iPtr->result = iPtr->resultSpace;
        iPtr->resultSpace[0] = 0;
        result = (*cmdPtr->proc)(cmdPtr->clientData, interp, argc, argv);
        if (result != TCL_OK) {
            break;
        }
    }

    /*
     * Free up any extra resources that were allocated.
     */

    done:
    if (pv.buffer != copyStorage) {
        ckfree((char *) pv.buffer);
    }
    if (argv != argStorage) {
        ckfree((char *) argv);
    }
    iPtr->numLevels--;
    if (iPtr->numLevels == 0) {
        if (result == TCL_RETURN) {
            result = TCL_OK;
        }
        if ((result != TCL_OK) && (result != TCL_ERROR)) {
            Tcl_ResetResult(interp);
            if (result == TCL_BREAK) {
                iPtr->result = "invoked \"break\" outside of a loop";
            } else if (result == TCL_CONTINUE) {
                iPtr->result = "invoked \"continue\" outside of a loop";
            } else {
                iPtr->result = iPtr->resultSpace;
                sprintf(iPtr->resultSpace, "command returned bad code: %d",
                        result);
            }
            result = TCL_ERROR;
        }
        if (iPtr->flags & DELETED) {
            Tcl_DeleteInterp(interp);
        }
    }

    /*
     * If an error occurred, record information about what was being
     * executed when the error occurred.
     */

    if ((result == TCL_ERROR) && !(iPtr->flags & ERR_ALREADY_LOGGED)) {
        int numChars;
        register char *p;

        /*
         * Compute the line number where the error occurred.
         */

        iPtr->errorLine = 1;
        for (p = cmd; p != cmdStart; p++) {
            if (*p == '\n') {
                iPtr->errorLine++;
            }
        }
        for ( ; isspace(*p) || (*p == ';'); p++) {
            if (*p == '\n') {
                iPtr->errorLine++;
            }
        }

        /*
         * Figure out how much of the command to print in the error
         * message (up to a certain number of characters, or up to
         * the first new-line).
         */

        numChars = src - cmdStart;
        if (numChars > (NUM_CHARS-50)) {
            numChars = NUM_CHARS-50;
            ellipsis = " ...";
        }

        if (!(iPtr->flags & ERR_IN_PROGRESS)) {
            sprintf(copyStorage, "\n    while executing\n\"%.*s%s\"",
                    numChars, cmdStart, ellipsis);
        } else {
            sprintf(copyStorage, "\n    invoked from within\n\"%.*s%s\"",
                    numChars, cmdStart, ellipsis);
        }
        Tcl_AddErrorInfo(interp, copyStorage);
        iPtr->flags &= ~ERR_ALREADY_LOGGED;
    } else {
        iPtr->flags &= ~ERR_ALREADY_LOGGED;
    }
    return result;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_CreateTrace --
 *
 *      Arrange for a procedure to be called to trace command execution.
 *
 * Results:
 *      The return value is a token for the trace, which may be passed
 *      to Tcl_DeleteTrace to eliminate the trace.
 *
 * Side effects:
 *      From now on, proc will be called just before a command procedure
 *      is called to execute a Tcl command.  Calls to proc will have the
 *      following form:
 *
 *      void
 *      proc(clientData, interp, level, command, cmdProc, cmdClientData,
 *              argc, argv)
 *          ClientData clientData;
 *          Tcl_Interp *interp;
 *          int level;
 *          char *command;
 *          int (*cmdProc)();
 *          ClientData cmdClientData;
 *          int argc;
 *          char **argv;
 *      {
 *      }
 *
 *      The clientData and interp arguments to proc will be the same
 *      as the corresponding arguments to this procedure.  Level gives
 *      the nesting level of command interpretation for this interpreter
 *      (0 corresponds to top level).  Command gives the ASCII text of
 *      the raw command, cmdProc and cmdClientData give the procedure that
 *      will be called to process the command and the ClientData value it
 *      will receive, and argc and argv give the arguments to the
 *      command, after any argument parsing and substitution.  Proc
 *      does not return a value.
 *
 *----------------------------------------------------------------------
 */

Tcl_Trace
Tcl_CreateTrace(interp, level, proc, clientData)
    Tcl_Interp *interp;         /* Interpreter in which to create the trace. */
    int level;                  /* Only call proc for commands at nesting level
                                 * <= level (1 => top level). */
    Tcl_CmdTraceProc *proc;     /* Procedure to call before executing each
                                 * command. */
    ClientData clientData;      /* Arbitrary one-word value to pass to proc. */
{
    register Trace *tracePtr;
    register Interp *iPtr = (Interp *) interp;

    tracePtr = (Trace *) ckalloc(sizeof(Trace));
    tracePtr->level = level;
    tracePtr->proc = proc;
    tracePtr->clientData = clientData;
    tracePtr->nextPtr = iPtr->tracePtr;
    iPtr->tracePtr = tracePtr;

    return (Tcl_Trace) tracePtr;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_DeleteTrace --
 *
 *      Remove a trace.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      From now on there will be no more calls to the procedure given
 *      in trace.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_DeleteTrace(interp, trace)
    Tcl_Interp *interp;         /* Interpreter that contains trace. */
    Tcl_Trace trace;            /* Token for trace (returned previously by
                                 * Tcl_CreateTrace). */
{
    register Interp *iPtr = (Interp *) interp;
    register Trace *tracePtr = (Trace *) trace;
    register Trace *tracePtr2;

    if (iPtr->tracePtr == tracePtr) {
        iPtr->tracePtr = tracePtr->nextPtr;
        ckfree((char *) tracePtr);
    } else {
        for (tracePtr2 = iPtr->tracePtr; tracePtr2 != NULL;
                tracePtr2 = tracePtr2->nextPtr) {
            if (tracePtr2->nextPtr == tracePtr) {
                tracePtr2->nextPtr = tracePtr->nextPtr;
                ckfree((char *) tracePtr);
                return;
            }
        }
    }
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_AddErrorInfo --
 *
 *      Add information to a message being accumulated that describes
 *      the current error.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      The contents of message are added to the "errorInfo" variable.
 *      If Tcl_Eval has been called since the current value of errorInfo
 *      was set, errorInfo is cleared before adding the new message.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_AddErrorInfo(interp, message)
    Tcl_Interp *interp;         /* Interpreter to which error information
                                 * pertains. */
    char *message;              /* Message to record. */
{
    register Interp *iPtr = (Interp *) interp;

    /*
     * If an error is already being logged, then the new errorInfo
     * is the concatenation of the old info and the new message.
     * If this is the first piece of info for the error, then the
     * new errorInfo is the concatenation of the message in
     * interp->result and the new message.
     */

    if (!(iPtr->flags & ERR_IN_PROGRESS)) {
        Tcl_SetVar2(interp, "errorInfo", (char *) NULL, interp->result,
                TCL_GLOBAL_ONLY);
        iPtr->flags |= ERR_IN_PROGRESS;

        /*
         * If the errorCode variable wasn't set by the code that generated
         * the error, set it to "NONE".
         */

        if (!(iPtr->flags & ERROR_CODE_SET)) {
            (void) Tcl_SetVar2(interp, "errorCode", (char *) NULL, "NONE",
                    TCL_GLOBAL_ONLY);
        }
    }
    Tcl_SetVar2(interp, "errorInfo", (char *) NULL, message,
            TCL_GLOBAL_ONLY|TCL_APPEND_VALUE);
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_VarEval --
 *
 *      Given a variable number of string arguments, concatenate them
 *      all together and execute the result as a Tcl command.
 *
 * Results:
 *      A standard Tcl return result.  An error message or other
 *      result may be left in interp->result.
 *
 * Side effects:
 *      Depends on what was done by the command.
 *
 *----------------------------------------------------------------------
 */
int
Tcl_VarEval(Tcl_Interp *interp, ...)
{
    va_list argList;
#define FIXED_SIZE 200
    char fixedSpace[FIXED_SIZE+1];
    int spaceAvl, spaceUsed, length;
    char *string, *cmd;
    int result;

    /*
     * Copy the strings one after the other into a single larger
     * string.  Use stack-allocated space for small commands, but if
     * the commands gets too large than call ckalloc to create the
     * space.
     */

    va_start(argList, interp);
    spaceAvl = FIXED_SIZE;
    spaceUsed = 0;
    cmd = fixedSpace;
    while (1) {
        string = va_arg(argList, char *);
        if (string == NULL) {
            break;
        }
        length = strlen(string);
        if ((spaceUsed + length) > spaceAvl) {
            char *new;

            spaceAvl = spaceUsed + length;
            spaceAvl += spaceAvl/2;
            new = ckalloc((unsigned) spaceAvl);
            memcpy((VOID *) new, (VOID *) cmd, spaceUsed);
            if (cmd != fixedSpace) {
                ckfree(cmd);
            }
            cmd = new;
        }
        strcpy(cmd + spaceUsed, string);
        spaceUsed += length;
    }
    va_end(argList);
    cmd[spaceUsed] = '\0';

    result = Tcl_Eval(interp, cmd, 0, (char **) NULL);
    if (cmd != fixedSpace) {
        ckfree(cmd);
    }
    return result;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_GlobalEval --
 *
 *      Evaluate a command at global level in an interpreter.
 *
 * Results:
 *      A standard Tcl result is returned, and interp->result is
 *      modified accordingly.
 *
 * Side effects:
 *      The command string is executed in interp, and the execution
 *      is carried out in the variable context of global level (no
 *      procedures active), just as if an "uplevel #0" command were
 *      being executed.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_GlobalEval(interp, command)
    Tcl_Interp *interp;         /* Interpreter in which to evaluate command. */
    char *command;              /* Command to evaluate. */
{
    register Interp *iPtr = (Interp *) interp;
    int result;
    CallFrame *savedVarFramePtr;

    savedVarFramePtr = iPtr->varFramePtr;
    iPtr->varFramePtr = NULL;
    result = Tcl_Eval(interp, command, 0, (char **) NULL);
    iPtr->varFramePtr = savedVarFramePtr;
    return result;
}