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The programmers of old were mysterious and profound. We
cannot fathom their thoughts, so all we do is describe their
Aware, like a fox crossing the water. Alert, like a general
on the battlefield. Kind, like a hostess greeting her guests.
Simple, like uncarved blocks of wood. Opaque, like black
pools in darkened caves.
Who can tell the secrets of their hearts and minds?
The answer exists only in the Tao.
-- Geoffrey James, "The Tao of Programming"
SBCL is derived from the 18b version of CMU CL.
Most of CMU CL was originally written as part of the CMU Common Lisp
project at Carnegie Mellon University. According to the documentation
in CMU CL 18b,
Organizationally, CMU Common Lisp was a small, mostly autonomous
part within the Mach operating system project. The CMU CL project
was more of a tool development effort than a research project.
The project started out as Spice Lisp, which provided a modern
Lisp implementation for use in the CMU community.
CMU CL has been under continuous development since the early 1980's
(concurrent with the Common Lisp standardization effort.)
Apparently most of the CMU Common Lisp implementors moved on to
work on the Gwydion environment for Dylan.
CMU CL's CLOS implementation is derived from the PCL reference
implementation written at Xerox PARC.
CMU CL's implementation of the LOOP macro was derived from code
from Symbolics, which was derived from code from MIT.
CMU CL had many individual author credits in the source files. In the
sometimes-extensive rearrangements which were required to make SBCL
bootstrap itself cleanly, it was tedious to try keep such credits
attached to individual source files, so they have been moved here
Bill Newman <firstname.lastname@example.org> did this transformation, and
so any errors made are probably his. Corrections would be appreciated.
MORE DETAILS ON SBCL'S CLOS CODE
The original headers of the PCL files contained the following text:
;;; Any person obtaining a copy of this software is requested to send their
;;; name and post office or electronic mail address to:
;;; CommonLoops Coordinator
;;; Xerox PARC
;;; 3333 Coyote Hill Rd.
;;; Palo Alto, CA 94304
;;; (or send Arpanet mail to CommonLoops-Coordinator.pa@Xerox.arpa)
;;; Suggestions, comments and requests for improvements are also welcome.
This was intended for the original incarnation of the PCL code as a
portable reference implementation. Since our version of the code has
had its portability hacked out of it, it's no longer particularly
relevant to any coordinated PCL effort (which probably doesn't exist
any more anyway). Therefore, this contact information has been deleted
from the PCL file headers.
A few files in the original CMU CL 18b src/pcl/ directory did not
carry such Xerox copyright notices:
* Some code was originally written by Douglas T. Crosher for CMU CL:
** the Gray streams implementation
** the implementation of DOCUMENTATION as methods of a generic
* generic-functions.lisp seems to have been machine-generated.
The comments in the CMU CL 18b version of the PCL code walker,
src/pcl/walk.lisp, said in part
;;; a simple code walker, based IN PART on: (roll the credits)
;;; Larry Masinter's Masterscope
;;; Moon's Common Lisp code walker
;;; Gary Drescher's code walker
;;; Larry Masinter's simple code walker
;;; boy, thats fair (I hope).
MORE DETAILS ON SBCL'S LOOP CODE
The src/code/loop.lisp file from CMU CL 18b had the following
credits-related information in it:
;;; The LOOP iteration macro is one of a number of pieces of code
;;; originally developed at MIT for which free distribution has been
;;; permitted, as long as the code is not sold for profit, and as long
;;; as notification of MIT's interest in the code is preserved.
;;; This version of LOOP, which is almost entirely rewritten both as
;;; clean-up and to conform with the ANSI Lisp LOOP standard, started
;;; life as MIT LOOP version 829 (which was a part of NIL, possibly
;;; never released).
;;; A "light revision" was performed by me (Glenn Burke) while at
;;; Palladian Software in April 1986, to make the code run in Common
;;; Lisp. This revision was informally distributed to a number of
;;; people, and was sort of the "MIT" version of LOOP for running in
;;; Common Lisp.
;;; A later more drastic revision was performed at Palladian perhaps a
;;; year later. This version was more thoroughly Common Lisp in style,
;;; with a few miscellaneous internal improvements and extensions. I
;;; have lost track of this source, apparently never having moved it to
;;; the MIT distribution point. I do not remember if it was ever
;;; The revision for the ANSI standard is based on the code of my April
;;; 1986 version, with almost everything redesigned and/or rewritten.
The date of the M.I.T. copyright statement falls around the time
described in these comments. The dates on the Symbolics copyright
statement are all later -- the earliest is 1989.
MORE DETAILS ON OTHER SBCL CODE FROM CMU CL
CMU CL's symbol (but not package) code (code/symbol.lisp) was
originally written by Scott Fahlman and updated and maintained
by Skef Wholey.
The CMU CL reader (code/reader.lisp) was originally the Spice Lisp
reader, written by David Dill and with support for packages added by
Lee Schumacher. David Dill also wrote the sharpmacro support
CMU CL's package code was rewritten by Rob MacLachlan based on an
earlier version by Lee Schumacher. It also includes DEFPACKAGE by Dan
Zigmond, and WITH-PACKAGE-ITERATOR written by Blaine Burks. William
Lott also rewrote the DEFPACKAGE and DO-FOO-SYMBOLS stuff.
CMU CL's string code (code/string.lisp) was originally written by
David Dill, then rewritten by Skef Wholey, Bill Chiles, and Rob
Various code in the system originated with "Spice Lisp", which was
apparently a predecessor to the CMU CL project. Much of that was
originally written by Skef Wholey:
code/seq.lisp, generic sequence functions, and COERCE
code/array.lisp, general array stuff
code/list.lisp, list functions (based on code from Joe Ginder and
The CMU CL seq.lisp code also gave credits for later work by Jim Muller
and Bill Chiles.
The modules system (code/module.lisp, containing REQUIRE, PROVIDE,
and friends, now deprecated by ANSI) was written by Jim Muller and
rewritten by Bill Chiles.
The CMU CL garbage collector was credited to "Christopher Hoover,
Rob MacLachlan, Dave McDonald, et al." in the CMU CL code/gc.lisp file,
with some extra code for the MIPS port credited to Christopher Hoover
alone. The credits on the original "gc.c", "Stop and Copy GC based
on Cheney's algorithm", said "written by Christopher Hoover".
Guy Steele wrote the original character functions
They were subsequently rewritten by David Dill, speeded up by Scott
Fahlman, and rewritten without fonts and with a new type system by Rob
Lee Schumacher made the Spice Lisp version of backquote. The comment
in the CMU CL sources suggests he based it on someone else's code for
some other Lisp system, but doesn't say which. A note in the CMU CL
code to pretty-print backquote expressions says that unparsing support
was provided by Miles Bader.
The CMU implementations of the Common Lisp query functions Y-OR-N-P
and YES-OR-NO-P were originally written by Walter van Roggen, and
updated and modified by Rob MacLachlan and Bill Chiles.
The CMU CL sort functions (code/sort.lisp) were written by Jim Large,
hacked on and maintained by Skef Wholey, and rewritten by Bill Chiles.
Most of the internals of the Python compiler seem to have been
originally written by Robert MacLachlan:
the type system and associated "cold load hack magic"
the lexical environment database
the IR1 representation and optimizer
the IR2 representation and optimizer
many concrete optimizations
compiler/srctran.lisp (with some code adapted from
CLC by Wholey and Fahlman)
information about optimization of known functions
debug information representation
memory pools to reduce consing by reusing compiler objects
toplevel interface functions and drivers
Besides writing the compiler, and various other work mentioned elsewhere,
Robert MacLachlan was also credited with tuning the implementation of
streams for Unix files, and writing
various floating point support code
code/float-trap.lisp, floating point traps
code/float.lisp, misc. support a la INTEGER-DECODE-FLOAT
low-level time functions
William Lott is also credited with writing or heavily maintaining some
parts of the CMU CL compiler. He was responsible for lifting
compiler/meta-vmdef.lisp out of compiler/vmdef.lisp, and also wrote
compiler/seqtran.lisp (with some code adapted from an older
seqtran written by Wholey and Fahlman)
the separable compiler backend
the implementation of LOAD-TIME-VALUE
the most recent version of the assembler
vop statistics gathering
centralized information about machine-dependent and..
..machine-independent FOO, with
compiler/generic/vm-fndb.lisp, FOO=function signatures
compiler/generic/vm-typetran.lisp, FOO=type ops
compiler/generic/objdef.lisp, FOO=object representation
compiler/generic/primtype.lisp, FOO=primitive types
Also, Christopher Hoover and William Lott wrote compiler/generic/vm-macs.lisp
to centralize information about machine-dependent macros and constants.
Sean Hallgren is credited with most of the Alpha backend. Julian
Dolby created the CMU CL Alpha/Linux port. Douglas Crosher added
The original PPC backend was the work of Gary Byers. Some bug fixes
and other changes to update it for current CMUCL interfaces were made
by Eric Marsden and Douglas Crosher
The CMU CL machine-independent disassembler (compiler/disassem.lisp)
was written by Miles Bader.
Parts of the CMU CL system were credited to Skef Wholey and Rob
MacLachlan jointly, perhaps because they were originally part of Spice
Lisp and were then heavily modified:
code/load.lisp, the loader, including all the FASL stuff
code/macros.lisp, various fundamental macros
code/mipsstrops.lisp, primitives for hacking strings
code/purify.lisp, implementation of PURIFY
code/stream.lisp, stream functions
code/lispinit.lisp, cold startup
code/profile.lisp, the profiler
Bill Chiles also modified code/macros.lisp. Much of the implementation
of PURIFY was rewritten in C by William Lott.
The CMU CL number functions (code/number.lisp) were written by Rob
MacLachlan, but acknowledge much code "derived from code written by
William Lott, Dave Mcdonald, Jim Large, Scott Fahlman, etc."
CMU CL's weak pointer support (code/weak.lisp) was written by
The CMU CL DEFSTRUCT system was credited to Rob MacLachlan, William
Lott and Skef Wholey jointly.
The FDEFINITION system for handling arbitrary function names (a la
(SETF FOO)) was originally written by Rob MacLachlan. It was modified
by Bill Chiles to add encapsulation, and modified more by William Lott
to add FDEFN objects.
The CMU CL condition system (code/error.lisp) was based on
some prototyping code written by Kent Pitman at Symbolics.
The CMU CL HASH-TABLE system was originally written by Skef Wholey
for Spice Lisp, then rewritten by William Lott, then rewritten
again by Douglas T. Crosher.
The support code for environment queries (a la LONG-SITE-NAME),
the DOCUMENTATION function, and the DRIBBLE function was written
and maintained "mostly by Skef Wholey and Rob MacLachlan. Scott
Fahlman, Dan Aronson, and Steve Handerson did stuff here too."
The same credit statement was given for the original Mach OS interface code.
The CMU CL printer, print.lisp, was credited as "written by Neal
Feinberg, Bill Maddox, Steven Handerson, and Skef Wholey, and modified
by various CMU Common Lisp maintainers." The comments on the float
printer said specifically that it was written by Bill Maddox. The
comments on bignum printing said specifically that it was written by
Steven Handerson (based on Skef's idea), and that it was rewritten by
William Lott to remove assumptions about length of fixnums on the MIPS
The comments in the main body of the CMU CL debugger
say that it was written by Bill Chiles. Some other related files
code/debug-int.lisp, programmer's interface to the debugger
code/ntrace.lisp, tracing facility based on breakpoints
say they were written by Bill Chiles and Rob MacLachlan.
The related file
src/debug-vm.lisp, low-level support for :FUNCTION-END breakpoints
was written by William Lott.
The CMU CL GENESIS cold load system,
compiler/generic/new-genesis.lisp, was originally written by Skef
Wholey, then jazzed up for packages by Rob MacLachlan, then completely
rewritten by William Lott for the MIPS port.
The CMU CL IR1 interpreter was written by Bill Chiles and Robert
Various CMU CL support code was written by William Lott:
the bytecode interpreter
bitblt-ish operations a la SYSTEM-AREA-COPY
code/fd-stream.lisp, Unix file descriptors as Lisp streams
code/filesys.lisp, other Unix filesystem interface stuff
handling errors signalled from assembly code
finalization based on weak pointers
irrational numeric functions
the pretty printer
predicates (both type predicates and EQUAL and friends)
saving the current Lisp image as a core file
handling Unix signals
The ALIEN facility seems to have been written largely by Rob
MacLachlan and William Lott. The CMU CL comments say "rewritten again,
this time by William Lott and Rob MacLachlan," but don't identify who
else might have been involved in earlier versions.
The comments in CMU CL's code/final.lisp say "the idea really was
Chris Hoover's". The comments in CMU CL's code/pprint.lisp say "Algorithm
stolen from Richard Waters' XP." The comments in CMU CL's code/format.lisp
say "with lots of stuff stolen from the previous version by David Adam
and later rewritten by Bill Maddox."
Jim Muller was credited with fixing seq.lisp.
CMU CL's time printing logic, in code/format-time.lisp, was written
by Jim Healy.
Bill Chiles was credited with fixing/updating seq.lisp after Jim Muller.
The CMU CL machine/filesystem-independent pathname functions
(code/pathname.lisp) were written by William Lott, Paul Gleichauf, and
Rob MacLachlan, based on an earlier version written by Jim Large and
Besides writing the original versions of the things credited to him
above, William Lott rewrote, updated, and cleaned up various stuff:
The INSPECT function was originally written by Blaine Burks.
The CMU CL DESCRIBE facility was originally written by "Skef Wholey or
Rob MacLachlan", according to the comments in the CMU CL sources. It
was cleaned up and reorganized by Blaine Burks, then ported and
cleaned up more by Rob MacLachlan. Also, since the split from CMU CL,
the SBCL DESCRIBE facility was rewritten as a generic function and so
become entangled with some DESCRIBE code which was distributed as part
The implementation of the Mersenne Twister RNG used in SBCL is based
on an implementation written by Douglas T. Crosher and Raymond Toy,
which was placed in the public domain with permission from M.
Comments in the CMU CL version of FreeBSD-os.c said it came from
an OSF version by Sean Hallgren, later hacked by Paul Werkowski,
with generational conservative GC support added by Douglas Crosher.
Comments in the CMU CL version of linux-os.c said it came from the
FreeBSD-os.c version, morfed to Linux by Peter Van Eynde in July 1996.
Comments in the CMU CL version of backtrace.c said it was "originally
from Rob's version" (presumably Robert Maclachlan).
Comments in the CMU CL version of purify.c said it had stack direction
changes, x86/CGC stack scavenging, and static blue bag stuff (all for
x86 port?) by Paul Werkowski, 1995, 1996; and bug fixes, x86 code
movement support, and x86/gencgc stack scavenging by Douglas Crosher,
1996, 1997, 1998.
According to comments in the source files, much of the CMU CL version
of the x86 support code
was originally written by William Lott, then debugged by Paul
Werkowski, and in some cases later enhanced and further debugged by
Douglas T. Crosher; and the x86 runtime support code,
was written by Paul F. Werkowski and Douglas T. Crosher.
The CMU CL user manual (doc/cmu-user/cmu-user.tex) says that the X86
FreeBSD port was originally contributed by Paul Werkowski, and Peter
VanEynde took the FreeBSD port and created a Linux version.
According to comments in src/code/bsd-os.lisp, work on the generic BSD
port was done by Skef Wholey, Rob MacLachlan, Scott Fahlman, Dan
Aronson, and Steve Handerson.
Douglas Crosher wrote code to support Gray streams, added X86 support
for the debugger and relocatable code, wrote a conservative
generational GC for the X86 port. He also added X86-specific
extensions to support stack groups and multiprocessing, but these are
not present in SBCL
The CMU CL user manual credits Robert MacLachlan as editor. A chapter
on the CMU CL interprocess communication extensions (not supported in
SBCL) was contributed by William Lott and Bill Chiles.
Peter VanEynde also contributed a variety of #+HIGH-SECURITY patches
to CMU CL, to provide additional safety, especially through runtime
checking on various tricky cases of standard functions (e.g. MAP with
complicated result types, and interactions of various variants of
Raymond Toy wrote CMU CL's PROPAGATE-FLOAT-TYPE extension and various
other floating point optimizations. (In SBCL, the PROPAGATE-FLOAT-TYPE
entry in *FEATURES* first became SB-PROPAGATE-FLOAT-TYPE, then went
away completely as the code became an unconditional part of the
CMU CL's long float support was written by Douglas T. Crosher.
Paul Werkowski turned the Mach OS support code into Linux OS support code.
Versions of the RUN-PROGRAM extension were written first by David
McDonald, then by Jim Healy and Bill Chiles, then by William Lott.
MORE DETAILS ON THE TRANSITION FROM CMU CL
Bill Newman did the original conversion from CMU CL 18b to a form
which could bootstrap itself cleanly, on Linux/x86 only. Although they
may not have realized it at the time, Rob Maclachlan and Peter Van
Eynde were very helpful, RAM by posting a clear explanation of what
GENESIS is supposed to be doing and PVE by maintaining a version of
CMU CL which worked on Debian, so that I had something to refer to
whenever I got stuck.
CREDITS SINCE THE RELEASE OF SBCL
(Note: (1) This is probably incomplete, since there's no systematic
procedure for updating it. (2) Some more details are available in the
NEWS file, in the project's CVS change logs, and in the archives of
the sbcl-devel mailing list. (3) In this, as in other parts of SBCL,
patches are welcome. Don't be shy.)
He reported many bugs, fixed many bugs, ported various fixes
from CMU CL, and helped clean up various stale bug data. (He has
been unusually energetic at this. As of sbcl-0.6.9.10, the
total number of bugs involved likely exceeded 100. Since then,
I've lost count. See the CVS logs.)
His contributions have included support for shared object loading
(from CMUCL), the Cheney GC for non-x86 ports (from CMUCL), Alpha
and PPC ports (from CMUCL), control stack exhaustion checking (new)
and native threads support for x86 Linux (new). He also refactored
the garbage collectors for understandability, wrote code
(e.g. grovel_headers.c and stat_wrapper stuff) to find
machine-dependent and OS-dependent constants automatically, and was
original author of the asdf, asdf-install, sb-bsd-sockets,
sb-executable, sb-grovel and sb-posix contrib packages.
Robert E. Brown:
He has reported various bugs and submitted several patches,
especially improving removing gratuitous efficiencies in the
Cadabra, Inc. (later merged into GoTo.com):
They hired Bill Newman to do some consulting for them,
including the implementation of EQUALP hash tables for CMU CL;
then agreed to release the EQUALP code into the public domain,
giving SBCL (and CMU CL) its EQUALP hash tables.
He continued to improve CMU CL after SBCL forked from it, creating
many patches which were directly applicable to SBCL. Notable examples
include fixes for various compiler bugs, the implementation of
CL:DEFINE-SYMBOL-MACRO, and a generalization of the type system's
handling of the CONS type to allow ANSI-style (CONS FOO BAR) types.
He has fixed many, many bugs. There's no single summary theme, but
he's fixed about a dozen different bugs in LOOP alone, and more
in the compiler itself. It appears that a lot of his fixes there
and elsewhere reflect systematic public-spiritedness, fixing bugs
as they show up in sbcl-devel or as archived in the BUGS file.
He is in the process of writing a comprehensive test suite for the
requirements of the ANSI Common Lisp standard. Already, at the
halfway stage, it has caught many tens of bugs in SBCL, and provided
simple test cases for them.
He creates binary packages of SBCL releases for Red Hat and other
He has fixed various bugs, and also done a lot of internal
cleanup, not visible at the user level but important for
maintenance. (E.g. converting the PCL code to use LOOP instead
of the old weird pre-ANSI ITERATE macro so that the code can be
read without being an expert in ancient languages and so that we
can delete a thousand lines of implement-ITERATE macrology from
He reported and fixed COMPILE's misbehavior on macros.
Espen S Johnsen:
He provided an ANSI-compliant version of CHANGE-CLASS for PCL.
He showed how to implement the DEBUG-RETURN functionality.
He found and fixed a number of SBCL bugs while partially porting
SBCL to bootstrap under Lispworks for Windows
He has continued to answer questions about, and contribute fixes to,
the CMU CL project. Some of these fixes, especially for compiler
problems, has been invaluable to the CMU CL project and, by
porting, invaluable to the SBCL project as well.
He has continued to work on CMU CL since the SBCL fork, and also
patched code to SBCL to enable dynamic loading of object files
under OpenBSD. He contributed to the port of SBCL to MacOS X,
implementing the Lisp side of the PowerOpen ABI.
Some of his fixes to CMU CL since the SBCL fork have been ported
to SBCL. He also maintains the cl-benchmark package, which gives
us some idea of how our performance changes compared to earlier
releases and to other implementations.
He has contributed a number of bug fixes and bug reports to SBCL.
He contributed to the port of SBCL to MacOS X. He found a way to
overcome binary compatibility issues between different versions of
dlcompat on Darwin.
He made a lot of progress toward getting SBCL to be bootstrappable
He has made many cleanups and improvements, small and large, in
CMU CL (mostly in PCL), which we have gratefully ported to SBCL. Of
particular note is his ctor MAKE-INSTANCE optimization, which is both
faster in the typical case than the old optimizations in PCL and
William ("Bill") Newman:
He continued to maintain SBCL after the fork, increasing ANSI
compliance, fixing bugs, regularizing the internals of the
system, deleting unused extensions, improving performance in
some areas (especially sequence functions and non-simple vectors),
updating documentation, and even, for better or worse, getting
rid of various functionality (e.g. the byte interpreter).
He contributed to the port of SBCL to MacOS X, finding solutions for
ABI and assembly syntax differences between Darwin and Linux.
Kevin M. Rosenberg:
He provided the ACL-style toplevel (sb-aclrepl contrib module), and
a number of MOP-related bug reports. He also creates the official
Debian packages of SBCL.
He ported SBCL to SPARC (based on the CMUCL backend), made various
port-related and SPARC-related changes (like *BACKEND-SUBFEATURES*),
made many fixes and improvements in the compiler's type system, has
essentially completed the work to enable bootstrapping SBCL under
unrelated (non-SBCL, non-CMU-CL) Common Lisps. He participated in
the modernization of SBCL's CLOS implementation, implemented the
treatment of compiler notes as restartable conditions, provided
optimizations to compiler output, and contributed in other ways as
Stig Erik Sandoe:
He showed how to convince the GNU toolchain to build SBCL in a way
which supports callbacks from C code into SBCL.
He wrote Unicode-capable versions of SBCL's character, string, and
stream types and operations on them.
He continued to work on CMU CL after the SBCL fork, especially on
floating point stuff. Various patches and fixes of his have been
ported to SBCL.
Peter Van Eynde:
He wrestled the CLISP test suite into a mostly portable test suite
(clocc ansi-test) which can be used on SBCL, provided a slew of
of bug reports resulting from that, and submitted many other bug
reports as well.
He ported SBCL to NetBSD, and also fixed a long-standing bug in
DEFSTRUCT with respect to colliding accessor names.
His O(N) implementation of the general case of MAP, posted on the
email@example.com mailing list, was the inspiration for similar MAP
code added in sbcl-0.6.8.
He ported sbcl-0.6.3 back to FreeBSD, restoring the ancestral
CMU CL support for FreeBSD and updating it for the changes made
from FreeBSD version 3 to FreeBSD version 4. He also ported the
CMU CL extension RUN-PROGRAM, and related code, to SBCL.
INITIALS GLOSSARY (helpful when reading comments, CVS commit logs, etc.)
MNA Martin Atzmueller
DB Daniel Barlow (also "dan")
DTC Douglas Crosher
APD Alexey Dejneka
NJF Nathan Froyd
AL Arthur Lemmens
RAM Robert MacLachlan
PRM Pierre Mai
WHN William ("Bill") Newman
CSR Christophe Rhodes
PVE Peter Van Eynde
PW Paul Werkowski