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The Glulx VM reference interpreter
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.gitignore Added a .gitignore.
Makefile Adds defaults for gtkglk.
README Put on a release date.
accel.c Added a new set of acceleration functions. (The old set still exist.)
exec.c Putting arguments on the macros is silly.
files.c Release 0.4.3.
float.c Added an option to *not* assume IEEE-754 native floats.
funcs.c Record stack information in profiling.
gestalt.c Putting arguments on the macros is silly.
gestalt.h Started adding the floating-point opcodes.
glkop.c Put in some defensive checks for missing Glk objects. I'm not sure this
glulxdump.c Brought the opcode table up to date. However, the disassembler is sti…
glulxe.h A compile-time option where the initial RAM state is kept in memory,
heap.c Removed a bunch of unused variables that never bothered me before.
iosstart.h Stash the gamefile.tag away in the library state, so that we can reco…
iosstart.m Add a hook for startup code customization.
macstart.c Release 0.3.4.
main.c Hook for autorestore.
opcodes.h Started adding the floating-point opcodes.
operand.c Putting arguments on the macros is silly.
osdepend.c Abstracted powf() to an osdepend wrapper. (Needed for Windows.) Add a list_by function.
profile.c Comment.
search.c Removed unnecessary include.
serial.c A compile-time option where the initial RAM state is kept in memory,
string.c Removed a bunch of unused variables that never bothered me before.
unixstrt.c Start rigging up call-count profiling.
vm.c Load memory in 256-byte chunks, because why rely on OS stream buffering?
winstart.c Bumped version number for 0.4.7 release.


Glulxe: the Glulx VM interpreter
Version 0.5.2

    Designed by Andrew Plotkin <>

* Compiling

Since this is a Glk program, it must be built with a Glk library. See
the Glk home page at

The Unix Makefile that comes with this package is designed to link any
of the Unix libraries (GlkTerm and CheapGlk.) You'll have to go into
the Makefile and set three variables to find the library. There are
instructions at the top of the Makefile. Then just type

    make glulxe

That should suffice. When the program is built, type

    ./glulxe filename.ulx

where "filename.ulx" is a Glulx game file to execute.

To build this program with a Mac or Window interface, you'll need the
appropriate Glk library.

This program supports floating-point operations, which are implemented
using the standard C99 math functions. The Makefile uses "-lm" to link
these in. If your platform does not support these functions, you can
comment out the "#define FLOAT_SUPPORT" line in glulxe.h.

* Version

0.5.2 (Mar 27, 2014):
    Added acceleration functions 8 through 13, which work correctly when
    NUM_ATTR_BYTES is changed.

0.5.1 (Mar 10, 2013):
    Fixed a bug in glkop.c that prevented get_buffer_stream() from
    working right.
    Updated to understand the upcoming, updated I6
    debug file format. (See
    The old format is still supported.

0.5.0 (Oct 18, 2012):
    Turned on memory-range checking in the default build. (Should have
    done this years ago.)
    Fixed a bug where @setmemsize could crash an open char memory stream
    or char line input request.
    Updated glkop.c to handle arrays of Glk objects. (This is needed to
    support glk_schannel_play_multi().)
    Added hooks for the library to execute at startup and select time.
    Added a hook which allows the library to get and pass on a game ID
    Clean up all memory allocation when the VM exits.

0.4.7 (Oct 10, 2011):
    Abstracted powf() to an osdepend wrapper. (Needed for Windows.)
    Fixed a @ceil bug, for some C math libraries.
    Improved the profiling system in several ways.
    Fixed a bug in glkop.c dispatching, to do with optional array

0.4.6 (Aug 17, 2010):
    Added floating-point math feature.
    Updated winstart.c. (Thanks David Kinder.)
    Fixed @random even more, on Windows.
    @verify works right on game files with extended memory.
    @getiosys works right when the two store operands are different
    variable types. (E.g., one local and one global.)

0.4.5 (Nov 23, 2009):
    VERIFY_MEMORY_ACCESS now detects writes to the ROM section of memory.
    Fixed off-by-eight bug in @astorebit and @aloadbit with negative bit
    Fixed an obscure bug with division and modulo of $80000000. (Thanks 
    Evin Robertson.)
    Fixed an extremely obscure problem with changing I/O mode in the middle
    of printing a number.
    Glk array/string operations are now checked for memory overflows
    (though not for ROM writing). This generates a warning at present;
    in the future, it will be a fatal error.
    Better fix for the @random bug.

0.4.4 (Mar 11, 2009):
    Added profiling code, which is turned off by default. To compile it 
    in, define VM_PROFILING in Makefile or in glulxe.h.
    Added function-accleration feature.
    Fixed bug where @random 0 was returning only positive numbers.

0.4.3 (Jan 23, 2008):
    Verify the presence of Unicode calls in the Glk library at runtime.
    (Thanks Simon Baldwin.)
    Added a compile-time option to check for invalid memory accesses.
    (This is slower, but safer. Define VERIFY_MEMORY_ACCESS in Makefile
    or in glulxe.h. Thanks Evin Robertson.)
    Fixed a memory leak of undo states. (Thanks Matthew Wightman.)
    Fixed a linked-list handling error for Glk unicode arrays. (Thanks
    David Kinder.)

0.4.2 (Feb 15, 2007):
    Fixed a bug that preventing compiling with old (pre-Unicode) Glk

0.4.1 (Feb 11, 2007):
    Added array copy and heap allocation functionality. (Glulx spec 

0.4.0 (Aug 13, 2006):
    Added Unicode functionality. (Glulx spec 3.0.0.)

0.3.5 (Aug 24, 2000):
    Fixed El-Stupido bug in the modulo opcode.

0.3.4 (Jul 11, 2000):
    Finally supports string arguments to Glk calls.

0.3.3 (Mar 29, 2000):
    Added setiosys, getiosys opcodes.
    Fixed bug in binarysearch.

0.3.2 (Feb 21, 2000):
    Added search, jumpabs, callf, and gestalt opcodes.

0.3.1 (Aug 23, 1999):
    Startup code now handles Blorb files correctly.

0.3.0 (Aug 17, 1999):
    Added support for compressed strings.

0.2.2 (Jun 15, 1999):
    Another pre-release version.

0.2.0 (May 30, 1999):
    A pre-release version.

* Permissions

The source code in this package is copyright 1999-2012 by Andrew Plotkin.
You may copy and distribute it freely, by any means and under any conditions,
as long as the code and documentation is not changed. You may also
incorporate this code into your own program and distribute that, or modify
this code and use and distribute the modified version, as long as you retain
a notice in your program or documentation which mentions my name and the
URL shown above.

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