SBCL(1)SBCL(1)NAME
SBCL -- Steel Bank Common Lisp
DESCRIPTION
SBCL is an implementation of ANSI Common Lisp, featuring a high-perfor‐
mance 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 subsys‐
tems 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 edit‐
ing, 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 nec‐
essary.
In order to understand the SBCL command line syntax, it is helpful to
understand that the system is composed of two parts: a runtime environ‐
ment, and the Common Lisp system it supports. Some command line argu‐
ments 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 com‐
mand 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 cus‐
tom 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 "--dis‐
able-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.
--no-merge-core-pages
Ensures that no sharing hint is provided to the operating system.
--default-merge-core-pages
Reverts the sharing hint policy to the default: only compressed
cores trigger hinting. Uncompressed cores are mapped directly from
the core file, which is usually enough to ensure sharing.
--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 com‐
mand 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 syn‐
tax is intended to reduce quoting headaches when invoking SBCL from
shell scripts.
--noprint
When ordinarily the toplevel "read-eval-print loop" would be exe‐
cuted, 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 back‐
trace 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 success‐
ful 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 speci‐
fied 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 explic‐
itly turned on. (Even today, some 30 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 under‐
standing 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 use‐
ful principle that "declarations are assertions", i.e. type declara‐
tions 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 mem‐
ory. 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), Alpha (Linux, Tru64), PPC (Linux, Darwin/MacOS X),
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 vio‐
lates 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 com‐
piling 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 effi‐
ciently, 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 func‐
tion 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 machin‐
ery, 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 some‐
thing 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 boot‐
strappability was the immediate motivation for forking off of the CMU
CL development tree. A variety of implementation differences are moti‐
vated 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 sepa‐
rate libraries. Some of these are distributed with SBCL as "contrib"
modules, others are distributed as separate software packages by sepa‐
rate 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 sets it from a compile-time
default location which is usually /usr/local/lib/sbcl/ but
may have been changed e.g. by a third-party packager.
FILESsbcl 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/sbclrc then /etc/sbclrc, 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)
SEE ALSO
Full SBCL documentation is maintained as a Texinfo manual. If is has
been installed, the command
info sbcl
should give you access to the complete manual. Depending on your
installation it may also be available in HTML and PDF formats in e.g.
/usr/local/share/doc/sbcl/
See the SBCL homepage
<http://www.sbcl.org/>
for more information, including directions on how to subscribe to the
sbcl-devel and sbcl-help mailing-lists.
7th Edition December 23, 2015 SBCL(1)
