Ubuntu Manpage: SBCL -- Steel Bank Common Lisp

NAME

       SBCL -- Steel Bank Common Lisp

DESCRIPTION

       SBCL  is  an  implementation  of  ANSI  Common  Lisp,  featuring a high-performance native
       compiler, native  threads  on  several  platforms,  a  socket  interface,  a  source-level
       debugger, a statistical profiler, and much more.

       It is free software, mostly in the public domain, but with some subsystems under BSD-style
       licenses which allow modification and reuse as long as credit is given. It is provided "as
       is", with no warranty of any kind.

       For  more  information about license issues, see the COPYING file in the distribution. For
       more information about history, see the CREDITS file in the distribution.

RUNNING SBCL

       To run SBCL, type "sbcl". After startup messages a prompt  ("*")  appears.  Enter  a  Lisp
       expression, and SBCL will read and execute it, print any values returned, give you another
       prompt, and wait for your next input.

         $ sbcl
         ...[startup messages elided]...
         * (+ 1 2 3)

         6
         * (exit)

       Most people like to run SBCL as a subprocess under Emacs. The Emacs "Slime" mode  provides
       many  convenient features, like command line editing, tab completion, and various kinds of
       coupling between Common Lisp source files and the interactive SBCL subprocess.

       For   information   on    creating    "standalone    executables"    using    SBCL,    see
       SB-EXT:SAVE-LISP-AND-DIE in the User Manual.

COMMAND LINE SYNTAX

       For ordinary interactive use, no command line arguments should be necessary.

       In  order to understand the SBCL command line syntax, it is helpful to understand that the
       system is composed of two parts: a runtime environment, and  the  Common  Lisp  system  it
       supports.  Some  command  line  arguments  are  processed during the initialization of the
       runtime, and some during the initialization of the Lisp system --  any  remaining  command
       line arguments are passed on to user code.

       The overall command line syntax is:

              sbcl     [runtime     options]     --end-runtime-options     [toplevel     options]
              --end-toplevel-options [user options]

       Both --end-runtime-options and --end-toplevel-options are optional, and  may  be  omitted.
       They  are  intended  for  use  in situations where any command line options are under user
       control (e.g. in batch files): by using them you can prevent  options  intended  for  your
       program being accidentally processed by SBCL.

       Supported runtime options are

       --core <corefilename>
          Use the specified Lisp core file instead of the default. (See the FILES section for the
          standard core, or the system documentation for SB-EXT:SAVE-LISP-AND-DIE for information
          about  how  to create a custom core.) Note that if the Lisp core file is a user-created
          core file, it may run a nonstandard toplevel which  does  not  recognize  the  standard
          toplevel options.

       --dynamic-space-size <megabytes>
          Size  of  the dynamic space reserved on startup in megabytes. Default value is platform
          dependent.

       --control-stack-size <megabytes>
          Size of control stack reserved for each thread in megabytes. Default value is 2.

       --noinform
          Suppress the printing of any banner or other informational message  at  startup.  (This
          makes  it  easier to write Lisp programs which work cleanly in Unix pipelines. See also
          the "--noprint" and "--disable-debugger" options.)

       --disable-ldb
          Disable the low-level debugger. Only effective if SBCL is compiled with LDB.

       --lose-on-corruption
          There are some dangerous low level  errors  (for  instance,  control  stack  exhausted,
          memory  fault) that (or whose handlers) can corrupt the image. By default SBCL prints a
          warning, then tries to continue and handle the error in Lisp, but this will not  always
          work and SBCL may malfunction or even hang. With this option, upon encountering such an
          error SBCL will invoke ldb (if present and enabled) or else exit.

       --script <filename>
          As  a  runtime  option  equivalent  to  --noinform  --disable-ldb  --lose-on-corruption
          --end-runtime-options  --script  <filename>.  See  the  description  of  --script  as a
          toplevel option below.

       --merge-core-pages
          When platform support is present, provide hints to the operating system that  identical
          pages  may be shared between processes until they are written to. This can be useful to
          reduce the memory usage on systems with multiple SBCL processes  started  from  similar
          but  differently-named  core files, or from compressed cores. Without platform support,
          do nothing. By default only compressed cores trigger hinting.

       --no-merge-core-pages
          Ensures that no sharing hint is provided to the operating system.

       --help
          Print some basic information about SBCL, then exit.

       --version
          Print SBCL's version information, then exit.

       In the future, runtime options may be added to control behavior such as lazy allocation of
       memory.

       Runtime  options,  including  any  --end-runtime-options  option,  are stripped out of the
       command line before the Lisp toplevel logic gets a chance to see it.

       The toplevel options supported by the standard SBCL core are

       --sysinit <filename>
          Load filename instead of the default system-wide initialization file.  (See  the  FILES
          section.)

       --no-sysinit
          Do  not  load a system-wide initialization file. If this option is given, the --sysinit
          option is ignored.

       --userinit <filename>
          Load filename instead of the default user initialization file. (See the FILES section.)

       --no-userinit
          Do not load a user initialization file. If this option is given, the --userinit  option
          is ignored.

       --eval <command>
          After  executing  any initialization file, but before starting the read-eval-print loop
          on standard input, read and evaluate the command given. More than one --eval option can
          be  used,  and  all  will be read and executed, in the order they appear on the command
          line.

       --load <filename>
          This is equivalent to --eval '(load "<filename>")'. The special syntax is  intended  to
          reduce quoting headaches when invoking SBCL from shell scripts.

       --noprint
          When ordinarily the toplevel "read-eval-print loop" would be executed, execute a "read-
          eval loop" instead, i.e. don't print a prompt and don't echo results. Combined with the
          --noinform  runtime  option,  this  makes  it easier to write Lisp "scripts" which work
          cleanly in Unix pipelines.

       --disable-debugger
          By default when SBCL encounters an error, it  enters  the  builtin  debugger,  allowing
          interactive  diagnosis  and  possible intercession.  This option disables the debugger,
          causing errors to print a backtrace and exit with status 1 instead -- which is  a  mode
          of   operation   better   suited   for   batch  processing.  See  the  User  Manual  on
          SB-EXT:DISABLE-DEBUGGER for details.

       --quit
          At the end of toplevel option processing, exit SBCL with a  successful  code  of  zero.
          Note  that  the effect of this option is delayed until after toplevel options following
          this one.

       --non-interactive
          This option disables the read-eval-print loop for both exceptional and  non-exceptional
          reasons.   It  is  short for --disable-debugger and --quit in combination and is useful
          for batch uses where the special option processing implied by --script is not desired.

       --script <filename>
          Implies --no-sysinit --no-userinit --disable-debugger --end-toplevel-options.

          Causes the system to load the specified file and exit immediately  afterwards,  instead
          of  entering  the  read-eval-print  loop. If the file begins with a shebang line, it is
          ignored.

       Regardless of the order in which toplevel options appear on the command line, the order of
       actions is:

       1. Debugger is disabled, if requested.

       2. Any system initialization file is loaded, unless prohibited.

       3. Any user initialization file is loaded, unless prohibited.

       4. --eval and --load options are processed in the order given.

       Finally,  either  the  read-eval-print loop is entered or the file specified with --script
       option is loaded.

       When running in the read-eval-print loop the system exits on end of file.  Similarly,  the
       system exits immediately after processing the file specified with --script.

       Note  that  when  running SBCL with the --core option, using a core file created by a user
       call to the SB-EXT:SAVE-LISP-AND-DIE, the toplevel options may be  under  the  control  of
       user  code  passed  as  arguments  to  SB-EXT:SAVE-LISP-AND-DIE.  For  this  purpose,  the
       --end-toplevel-options option itself can be considered a toplevel option,  i.e.  the  user
       core, at its option, may not support it.

       In  the  standard SBCL startup sequence (i.e. with no user core involved) toplevel options
       and any --end-toplevel-options option are stripped out of the command line  argument  list
       before user code gets a chance to see it.

OVERVIEW

       SBCL  is  derived  from  the  CMU CL. (The name is intended to acknowledge the connection:
       steel and banking are the industries where Carnegie and Mellon made the big bucks.)

       SBCL compiles by default: even functions entered in the read-eval-print loop are  compiled
       to  native  code, unless the evaluator has been explicitly turned on. (Even today, some 40
       years after the MacLisp compiler, people  will  tell  you  that  Lisp  is  an  interpreted
       language. Ignore them.)

       SBCL aims for but has not completely achieved compliance with the ANSI standard for Common
       Lisp. More information about this is available in the BUGS section below.

       SBCL also includes various non-ANSI extensions, described more fully in the  User  Manual.
       Some  of  these  are in the base system and others are "contrib" modules loaded on request
       using REQUIRE.  For example, to  load  the  SB-BSD-SOCKETS  module  that  provides  TCP/IP
       connectivity,
          * (require 'asdf)
          * (require 'sb-bsd-sockets)

       For more information, see the User Manual.

THE COMPILER

       SBCL  inherits  from CMU CL the "Python" native code compiler. (Though we often avoid that
       name in order to avoid confusion with the scripting language  also  called  Python.)  This
       compiler is very clever about understanding the type system of Common Lisp and using it to
       optimize code, and about producing notes to let the user know when  the  compiler  doesn't
       have  enough  type  information  to  produce  efficient code. It also tries (almost always
       successfully) to follow the unusual but  very  useful  principle  that  "declarations  are
       assertions",  i.e.   type  declarations  should  be  checked  at  runtime  unless the user
       explicitly tells the system that speed is more important than safety.

       The compiled code uses garbage collection to  automatically  manage  memory.  The  garbage
       collector  implementation varies considerably from CPU to CPU. In particular, on some CPUs
       the GC is nearly exact, while on others it's more conservative, and on some CPUs the GC is
       generational, while on others simpler stop and copy strategies are used.

       For more information about the compiler, see the user manual.

SYSTEM REQUIREMENTS

       SBCL  currently  runs  on  X86  (Linux, FreeBSD, OpenBSD, and NetBSD), X86-64 (Linux), PPC
       (Linux), SPARC (Linux and Solaris 2.x), and MIPS (Linux). For information on other ongoing
       and possible ports, see the sbcl-devel mailing list, and/or the web site.

       SBCL  requires on the order of 16Mb RAM to run on X86 systems, though all but the smallest
       programs would be happier with 32Mb or more.

KNOWN BUGS

       This section attempts to list the most serious and long-standing bugs.  For more  detailed
       and current information on bugs, see the BUGS file in the distribution.

       It  is  possible  to  get  in  deep  trouble  by  exhausting heap memory.  The SBCL system
       overcommits memory at startup, so, on typical Unix-alikes like  Linux  and  FreeBSD,  this
       means  that  if  the  SBCL system turns out to use more virtual memory than the system has
       available for it, other processes tend to be killed randomly (!).

       The compiler's handling of function return values unnecessarily violates the "declarations
       are  assertions"  principle  that  it  otherwise  adheres to. Using PROCLAIM or DECLAIM to
       specify the return type of a function causes the compiler to believe you without checking.
       Thus compiling a file containing
         (DECLAIM (FTYPE (FUNCTION (T) NULL) SOMETIMES))
         (DEFUN SOMETIMES (X) (ODDP X))
         (DEFUN FOO (X) (IF (SOMETIMES X) 'THIS-TIME 'NOT-THIS-TIME))
       then  running (FOO 1) gives NOT-THIS-TIME, because the compiler relied on the truth of the
       DECLAIM without checking it.

       Some things are implemented very inefficiently.

       -- Multidimensional arrays are inefficient, especially multidimensional arrays of floating
          point numbers.

       -- SBCL,  like  most  (maybe  all?)  implementations of Common Lisp on stock hardware, has
          trouble passing floating point numbers around efficiently,  because  a  floating  point
          number,  plus  a  few  extra  bits to identify its type, is larger than a machine word.
          (Thus, they get "boxed" in heap-allocated  storage,  causing  GC  overhead.)  Within  a
          single  compilation unit, or when doing built-in operations like SQRT and AREF, or some
          special operations like structure slot accesses, this is avoidable: see the user manual
          for  some  efficiency  hints.  But  for general function calls across the boundaries of
          compilation units, passing the result of a floating point  calculation  as  a  function
          argument  (or returning a floating point result as a function value) is a fundamentally
          slow operation.

REPORTING BUGS

       To report a bug, please send mail to the mailing lists sbcl-help or  sbcl-devel.  You  can
       find    the    complete    mailing    list    addresses    on    the    web    pages    at
       <http://sbcl.sourceforge.net/>; note that as a spam reduction measure you  must  subscribe
       to  the  lists  before  you  can  post.  (You may also find fancy SourceForge bug-tracking
       machinery there, but don't be fooled. As of 2002-07-25 anyway, we don't  actively  monitor
       that  machinery, and it exists only because we haven't been able to figure out how to turn
       it off.)

       As with any software bug report, it's most helpful if you can provide  enough  information
       to  reproduce  the  symptoms  reliably, and if you say clearly what the symptoms are.  For
       example, "There seems to be something wrong with TAN of  very  small  negative  arguments.
       When  I  execute (TAN LEAST-NEGATIVE-SINGLE-FLOAT) interactively on sbcl-1.2.3 on my Linux
       4.5 X86 box, I get an UNBOUND-VARIABLE error."

DIFFERENCES FROM CMU CL

SBCL can be built from scratch using a plain vanilla ANSI Common Lisp system and a C
compiler, and all of its properties are specified by the version of the source code that
it was created from. This clean bootstrappability was the immediate motivation for forking
off of the CMU CL development tree. A variety of implementation differences are motivated
by this design goal.

Maintenance work in SBCL since the fork has diverged somewhat from the maintenance work in
CMU CL. Many but not all bug fixes and improvements have been shared between the two
projects, and sometimes the two projects disagree about what would be an improvement.

Most extensions supported by CMU CL have been unbundled from SBCL, including Motif
support, the Hemlock editor, search paths, the WIRE protocol, various user-level macros
and functions (e.g. LETF, ITERATE, MEMQ, REQUIRED-ARGUMENT), and many others.

(Why doesn't SBCL support more extensions natively? Why drop all those nice extensions
from CMU CL when the code already exists? This is a frequently asked question on the
mailing list. There are two principal reasons. First, it's a design philosophy issue:
arguably SBCL has done its job by supplying a stable FFI, and the right design decision is
to move functionality derived from that, like socket support, into separate libraries.
Some of these are distributed with SBCL as "contrib" modules, others are distributed as
separate software packages by separate maintainers. Second, it's a practical decision -
focusing on a smaller number of things will, we hope, let us do a better job on them.)

SUPPORT

       Various  information  about SBCL is available at <http://www.sbcl.org/>. The mailing lists
       there are the recommended place to look for support.

AUTHORS

       Dozens of people have made substantial contributions to SBCL and its  subsystems,  and  to
       the  CMU  CL  system  on  which  it was based, over the years. See the CREDITS file in the
       distribution for more information.

ENVIRONMENT

       SBCL_HOME This variable controls where files like "sbclrc", "sbcl.core",  and  the  add-on
                 "contrib"  systems  are  searched  for.  If  it  is  not set, then sbcl looks in
                 ../lib/sbcl/ relative to the location of  the  executable,  or  in  the  current
                 directory. If your executable is in the default location /usr/local/bin/ then it
                 will look in /usr/local/lib/sbcl/.

FILES

       sbcl   executable program containing some low-level runtime support and a loader, used  to
              read sbcl.core

       sbcl.core
              dumped memory image containing most of SBCL, to be loaded by the `sbcl' executable.
              Looked for in $SBCL_HOME, unless overridden by the --core option.

       sbclrc optional system-wide startup script, looked for in  $SBCL_HOME  then  /etc,  unless
              overridden by the --sysinit command line option.

       .sbclrc
              optional  per-user  customizable  startup  script  (in user's home directory, or as
              specified by  --userinit)