# t3.h | documentation

    #charset "us-ascii"
    #pragma once

    /*
     *   Copyright (c) 1999, 2006 Michael J. Roberts
     *
     *   This file is part of TADS 3
     *
     *   This header defines the t3vm intrinsic function set.  These functions
     *   provide access to basic features of the Virtual Machine.
     */

    /*
     *   include the LookupTable intrinsic class, since t3GetGlobalSymbols()
     *   returns an instance of this class
     */
    #include "lookup.h"

    /*
     *   T3 intrinsic function set definition
     */
    intrinsic 't3vm/010006'
    {
        /*
         *   Explicitly run garbage collection.
         */
        t3RunGC();

        /*
         *   Set the default output function or method.  The return value is the
         *   old function pointer or method, depending on which one is being set
         *   with this call.  (If 'val' is a function pointer, the return value
         *   will be the old function; if 'val' is a property ID, the return
         *   value is the old method.)
         *
         *   The special values T3SetSayNoFunc and T3SetSayNoMethod can be passed
         *   to the function to remove any existing function or method,
         *   respectively, and are returned when appropriate to indicate that
         *   there was no previous setting.
         */
        t3SetSay(val);

        /*
         *   Get the VM version number.  Returns the version number as an integer
         *   value, with the major version in the high-order 16 bits, the minor
         *   version number in the next 8 bits, and the patch number ("point
         *   release" number) in the low-order 8 bits.  For example, version
         *   3.0.10 is encoded as 0x0003000A.
         */
        t3GetVMVsn();

        /*
         *   Get the VM identifier string.  This returns the version number as a
         *   string, as in '3.0.10'.
         */
        t3GetVMID();

        /*
         *   Get the VM banner string.  This returns a string with the name of
         *   the VM, the version number, and a copyright string, in a format
         *   suitable for displaying to the user to identify the VM executable.
         */
        t3GetVMBanner();

        /*
         *   Get the preinitialization mode flag.  This returns true if the VM is
         *   running as part of the compiler's pre-initialization phase, nil if
         *   it's running as a normal interpreter.
         */
        t3GetVMPreinitMode();

        /*
         *   Debugger trace operations.  This provides access to the interactive
         *   debugger subsystem, if the VM is running under a debugger.  The
         *   'mode' argument determines what the function does and what the
         *   additional arguments, if any, are for:
         *
         *   T3DebugCheck - checks to see if an interactive debugger is present.
         *   No additional arguments; returns true if a debugger is present, nil
         *   if not.
         *
         *   T3DebugBreak - breaks into the interactive debugger, pausing
         *   execution at the current code location so that the user can inspect
         *   the current machine state and determine how to proceed.  No
         *   additional arguments; after the user proceeds with execution, the
         *   function returns true to indicate that a debugger is present.  If no
         *   debugger is present, the function simply returns nil, and has no
         *   other effect.
         *
         *   T3DebugLog - writes a message to the debug log.  The second argument
         *   is a string with the text of the message to write.  When running
         *   under an interactive debugger, the log is usually displayed as a
         *   window in the UI, or something similar.  When running in a regular
         *   interpreter, the log is stored as a text file called tadslog.txt, in
         *   a directory location that varies by system.  When a log file is
         *   used, the system automatically adds a timestamp to each message.
         */
        t3DebugTrace(mode, ...);

        /*
         *   Get the global symbol table or the global macro table.
         *
         *   'which' specifies which table to retrieve:
         *
         *.     T3GlobalSymbols - return the global symbol table
         *.     T3PreprocMacros - return the preprocessor macro table
         *
         *   If 'which' is omitted, the global symbol table is returned by
         *   default.
         *
         *   If the requested symbol table is available, this returns a
         *   LookupTable object; otherwise, it returns nil.
         *
         *   The symbol tables are available under two conditions.  First, while
         *   pre-initialization is running during the program build (compiling)
         *   process, regardless of the debug/release mode being used for
         *   compilation.  Second, during normal "t3run" execution, but only when
         *   the program has been compiled for debugging.  When you compile in
         *   release mode, the compiler omits the debugging symbols from the .t3
         *   image file to save space, so the symbol tables won't be available
         *   when running a release build under the interpreter.
         *
         *   If you want to access the symbol tables under normal execution
         *   (i.e., after preinit) in a release build, you can do it, but it
         *   requires an extra manual step.  The trick is to call this function
         *   during preinit, when the symbol tables are definitely available
         *   regardless of the debug/release mode, and then save a reference to
         *   each desired table in an object property.  This will ensure that the
         *   final image file saved after preinit completes includes the tables,
         *   because the object property reference ensures that the garbage
         *   collector won't delete them.  Now, you *still* can't access the
         *   tables again at run-time by calling t3GetGlobalSymbols(), but you
         *   can instead get the same information from your saved object
         *   property.
         */
        t3GetGlobalSymbols(which?);

        /*
         *   Allocate a new property.  Returns a new property not yet used
         *   anywhere in the program.  Note that property ID's are a somewhat
         *   limited resource - only approximately 65,000 total are available,
         *   including all of the properties that the program defines
         *   statically.
         */
        t3AllocProp();

        /*
         *   Get a stack trace.  This returns a list of T3StackInfo objects.
         *   Each object represents a nesting level in the call stack.  The first
         *   element in the list represents the currently active level (i.e., the
         *   level that called this function), the second element represents the
         *   caller of the first element, and so on.
         *
         *   If 'level' is an integer, we'll return a single T3StackInfo object
         *   giving the context at the given stack level - 1 is the active level,
         *   2 is its caller, and so on, so 'level' would simply be the index in
         *   the returned list when this argument is omitted.  If 'level' is
         *   omitted or nil, we return a list of T3StackInfo objects giving the
         *   entire stack trace.
         *
         *   If 'flags' is specified, it's a combination of T3GetStackXxx flags
         *   specifying additional options.  If this isn't included, the default
         *   is 0 (i.e., all flags turned off).
         */
        t3GetStackTrace(level?, flags?);

        /*
         *   Get a named argument.  This searches for the specified named
         *   argument, and returns the value of the argument if it's defined.
         *
         *   'name' is a string giving the name of the argument to search for.
         *   This must exactly match the name of an argument passed by a caller
         *   with the "name: value" syntax.  The match is case-sensitive.
         *
         *   'defval' is an optional default value to return if the argument
         *   doesn't exist.  If 'deval' is specified, and the argument doesn't
         *   exist, the function returns 'defval'.  If 'defval' is omitted, and
         *   the argument doesn't exist, the function throws an error.
         */
        t3GetNamedArg(name, defval?);

        /*
         *   Get a list of all named arguments currently in effect.  This returns
         *   a list of strings, where each string is the name of a named argument
         *   that's currently active.
         */
        t3GetNamedArgList();
    }

    /*
     *   t3DebugTrace() mode flags
     */

    /* check to see if the debugger is present */
    #define T3DebugCheck     1

    /* break into the debugger */
    #define T3DebugBreak     2

    /* log a message to the system/debug log */
    #define T3DebugLog       3

    /*
     *   t3SetSay() special values.  These can be passed in lieu of a function
     *   pointer or property ID when the caller wants to remove any existing
     *   function or method rather than install a new one.
     */
    #define T3SetSayNoFunc    1
    #define T3SetSayNoMethod  2

    /*
     *   t3GetGlobalSymbols 'which' flag.  One of these values can be specified
     *   as the function argument to specify which type of table is to be
     *   retrieved.
     */
    #define T3GlobalSymbols   1
    #define T3PreprocMacros   2

    /*
     *   t3GetStackTrace flags.  These can be combined with the bitwise '|'
     *   operator.
     */
    #define T3GetStackLocals  0x0001
    #define T3GetStackDesc    0x0002

    /*
     *   Macro information flags.
     */
    #define T3MacroHasArgs     0x0001
    #define T3MacroHasVarargs  0x0002

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