X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=doc%2Fsbcl.1;h=ea0c131d4d38f6bc66b425a891c2708df44457f1;hb=979539d20a27f4315db9e1bde0a4413135cf8603;hp=9161690e4d74c11583194966d26664170d63cce4;hpb=ea36d3d79b9dfe3598faca5e267efd5980b94d4a;p=sbcl.git diff --git a/doc/sbcl.1 b/doc/sbcl.1 index 9161690..ea0c131 100644 --- a/doc/sbcl.1 +++ b/doc/sbcl.1 @@ -16,390 +16,456 @@ .TH SBCL 1 "$Date$" .AT 3 .SH NAME -SBCL -- "Steel Bank Common Lisp" +SBCL -- Steel Bank Common Lisp .SH DESCRIPTION -SBCL is a free Common Lisp programming environment. It is derived from -the free CMU CL programming environment. (The name is intended to -acknowledge the connection: steel and banking are the industries where -Carnegie and Mellon made the big bucks.) +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. + +.SH RUNNING SBCL + +To run SBCL, type "sbcl". After startup messages a prompt +("\f(CR*\fR") 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. + +\f(CR + $ sbcl + ...[startup messages elided]... + * (+ 1 2 3) + + 6 + * (exit) +\fR + +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 +\f(CRSB\-EXT:SAVE\-LISP\-AND\-DIE\fR in the User Manual. .SH COMMAND LINE SYNTAX -Command line syntax can be considered an advanced topic; for ordinary -interactive use, no command line arguments should be necessary. +For ordinary interactive use, no command line arguments should be +necessary. -In order to understand the command line argument syntax for SBCL, it -is helpful to understand that the SBCL system is implemented as two -components, a low-level runtime environment written in C and a -higher-level system written in Common Lisp itself. Some command line -arguments are processed during the initialization of the low-level -runtime environment, some command line arguments are processed during -the initialization of the Common Lisp system, and any remaining +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 full, unambiguous syntax for invoking SBCL at the command line is +The overall command line syntax is: .TP 3 -.B sbcl [runtime options] --end-runtime-options [toplevel options] --end-toplevel-options [user options] +.B sbcl [runtime options] \-\-end\-runtime\-options [toplevel options] \-\-end\-toplevel\-options [user options] .PP -For convenience, the --end-runtime-options and --end-toplevel-options -elements can be omitted. Omitting these elements can be convenient -when you are running the program interactively, and you can see that -no ambiguities are possible with the option values you are using. -Omitting these elements is probably a bad idea for any batch file -where any of the options are under user control, since it makes it -impossible for SBCL to detect erroneous command line input, so that -erroneous command line arguments will be passed on to the user program -even if they was intended for the runtime system or the Lisp system. +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 .TP 3 -.B --core -Run the specified Lisp core file instead of the default. (See the FILES -section.) 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. +.B \-\-core +Use the specified Lisp core file instead of the default. (See the FILES +section for the standard core, or the system documentation for +\f(CRSB\-EXT:SAVE\-LISP\-AND\-DIE\fR 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. +.TP 3 +.B \-\-dynamic-space-size +Size of the dynamic space reserved on startup in megabytes. Default value +is platform dependent. +.TP 3 +.B \-\-control-stack-size +Size of control stack reserved for each thread in megabytes. Default value +is 2. .TP 3 -.B --noinform +.B \-\-noinform Suppress the printing of any banner or other informational message at -startup. (This makes it easier to write Lisp programs which work in -Unix pipelines. See also the "--noprogrammer" and "--noprint" options.) +startup. (This makes it easier to write Lisp programs which work +cleanly in Unix pipelines. See also the "\-\-noprint" and +"\-\-disable\-debugger" options.) +.TP 3 +.B \-\-disable\-ldb +Disable the low-level debugger. Only effective if SBCL is compiled with LDB. +.TP 3 +.B \-\-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. +.TP 3 +.B \-\-script +As a runtime option equivalent to \-\-noinform \-\-disable\-ldb +\-\-lose\-on\-corruption \-\-end\-runtime\-options \-\-script +. See the description of \-\-script as a toplevel option +below. +.TP 3 +.B \-\-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. +.TP 3 +.B \-\-no-merge\-core\-pages +Ensures that no sharing hint is provided to the operating system. +.TP 3 +.B \-\-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. +.TP 3 +.B \-\-help +Print some basic information about SBCL, then exit. +.TP 3 +.B \-\-version +Print SBCL's version information, then exit. .PP 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, +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. -Supported toplevel options for the standard SBCL core are +The toplevel options supported by the standard SBCL core are .TP 3 -.B --sysinit +.B \-\-sysinit Load filename instead of the default system-wide initialization file. -(See the FILES section.) There is no special option to cause no -system-wide initialization file to be read, but on a Unix system -"--sysinit /dev/null" can be used to achieve the same effect. +(See the FILES section.) +.TP 3 +.B \-\-no\-sysinit +Do not load a system-wide initialization file. If this option is +given, the \-\-sysinit option is ignored. .TP 3 -.B --userinit +.B \-\-userinit Load filename instead of the default user initialization file. (See -the FILES section.) There is no special option to cause no user -initialization file to be read, but on a Unix system "--userinit -/dev/null" can be used to achieve the same effect. +the FILES section.) .TP 3 -.B --eval +.B \-\-no\-userinit +Do not load a user initialization file. If this option is +given, the \-\-userinit option is ignored. +.TP 3 +.B \-\-eval After executing any initialization file, but before starting the -read-eval-print loop on standard input, evaluate the command given. -More than one --eval option can be used, and all will be executed, in -the order they appear on the command line. +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. +.TP 3 +.B \-\-load +This is equivalent to \-\-eval \(aq(load "")\(aq. The special +syntax is intended to reduce quoting headaches when invoking SBCL +from shell scripts. .TP 3 -.B --noprint +.B \-\-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 in Unix pipelines. +execute a "read-eval loop" instead, \fIi.e.\fR 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. .TP 3 -.B --noprogrammer -By default, a Common Lisp system tries to ask the programmer for help -when it gets in trouble (by printing a debug prompt on *DEBUG-IO*). -However, this is not useful behavior for a system running with no -programmer available, and this option tries to set up more appropriate -behavior for that situation. Thus we set *DEBUG-IO* to send its -output to *ERROR-OUTPUT*, and to raise an error if any input is -requested from it; and we set *DEBUGGER-HOOK* to output a backtrace, -then exit the process with a failure code. -.PP - -Regardless of the order in which --sysinit, --userinit, and --eval -options appear on the command line, the sysinit file, if it exists, is -loaded first; then the userinit file, if it exists, is loaded; then -any --eval commands are executed in sequence; then the read-eval-print -loop is started on standard input. At any step, error conditions or -commands such as SB-EXT:QUIT can cause execution to be terminated -before proceeding to subsequent steps. - -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. +.B \-\-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 \f(CRSB\-EXT:DISABLE\-DEBUGGER\fR for details. +.TP 3 +.B \-\-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. +.TP 3 +.B \-\-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. +.TP 3 +.B \-\-script +Implies \-\-no-sysinit \-\-no-userinit \-\-disable-debugger +\-\-end\-toplevel\-options. -.SH OVERVIEW +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. +.PP -SBCL aims for but has not reached ANSI compliance. +Regardless of the order in which toplevel options appear on the command +line, the order of actions is: + +.nr step 1 1 +.IP \n[step]. 3 +Debugger is disabled, if requested. +.IP \n+[step]. +Any system initialization file is loaded, unless prohibited. +.IP \n+[step]. +Any user initialization file is loaded, unless prohibited. +.IP \n+[step]. +\-\-eval and \-\-load options are processed in the order given. +.PP -SBCL compiles Lisp to native code, or optionally to more-compact but -much slower byte code. +Finally, either the read-eval-print loop is entered or the file +specified with \-\-script option is loaded. -SBCL's garbage collector is generational and conservative. +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. -SBCL includes a source level debugger, as well as the ANSI TRACE -facility and a rudimentary profiler. +Note that when running SBCL with the \-\-core option, using a core +file created by a user call to the +\f(CRSB\-EXT:SAVE\-LISP\-AND\-DIE\fR, the toplevel options may be +under the control of user code passed as arguments to +\f(CRSB\-EXT:SAVE\-LISP\-AND\-DIE\fR. For this purpose, the +\-\-end\-toplevel\-options option itself can be considered a toplevel +option, \fIi.e.\fR the user core, at its option, may not support it. -.SH DIFFERENCES FROM CMU CL +In the standard SBCL startup sequence (\fIi.e.\fR 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. -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 internal implementation -differences are motivated by this. - -Maintenance work in SBCL since the fork has diverged in various -details from the maintenance work in CMU CL. E.g. as of 2001-04-12, -SBCL was more ANSI-compliant than CMU CL in various details such as -support for PRINT-OBJECT and DESCRIBE-OBJECT, and SBCL's compiler was -substantially better than CMU CL's at optimizing operations on -non-simple vectors. - -Most extensions supported by CMU CL are not supported in SBCL, -including Motif support, the Hemlock editor, search paths, the -low-level Unix interface, the WIRE protocol, multithreading support, -various user-level macros and functions (e.g. LETF, ITERATE, MEMQ, -REQUIRED-ARGUMENT), and many others. - -SBCL has retained some extensions from parent CMU CL. Many of the -retained extensions are in these categories: -.TP 3 -\-- -things which might be in the new ANSI spec, e.g. weak pointers, -finalization, foreign function interface to C, and Gray streams -.TP 3 -\-- -things which are universally available in Unix scripting languages, -e.g. RUN-PROGRAM and POSIX argv and getenv -.TP 3 -\-- -hooks into the low level workings of the system which can be useful -for debugging, e.g. a list of functions to be run whenever GC occurs, -or parameters to modify compiler diagnostic output -.TP 3 -\-- -unportable performance hacks, e.g. TRULY-THE, FREEZE-TYPE, and PURIFY -.PP +.SH OVERVIEW -There are also a few retained extensions which don't fall into -any particular category, e.g. -.TP 3 -\-- -the ability to save running Lisp images as executable files +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 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 \f(CRREQUIRE\fR. For +example, to load the \f(CRSB\-BSD\-SOCKETS\fR module that provides +TCP/IP connectivity, +\f(CR + * (require \(aqasdf) + * (require \(aqsb\-bsd\-sockets) +\fR + +For more information, see the User Manual. .PP -Some of the retained extensions have new names and/or different -options than their CMU CL counterparts. For example, the SBCL function -which saves a Lisp image to disk and kills it is called -SAVE-LISP-AND-DIE instead of SAVE-LISP, and it supports fewer keyword -options than CMU CL's SAVE-LISP. - -(Why doesn't SBCL support more extensions? Why the hell did I (WHN) -drop all those nice extensions from CMU CL when the code already -exists? This is a frequently asked question on the mailing list. The -answer is that they're hard to maintain, and I have enough on my hands -already. Also, in the case of some big and unquestionably useful -extensions, like sockets and Motif, I think that SBCL has done its job -by supplying the FFI, and that people who need, and understand, and -are motivated to maintain the functionality should supply it as a -separate library, which I'd be happy to distribute or link to on the -SBCL home page. Finally, in the case of multithreading, I do think it -belongs in the new ANSI spec, and it'd be a good feature to have, but -I didn't think the CMU CL implementation was sufficiently mature, and -it's such a complicated and far-reaching extension that I thought that -trying to fix it would interfere with the more urgent task of getting -basic ANSI support up to speed.) - .SH THE COMPILER -SBCL inherits from CMU CL the "Python" native code compiler. This -compiler is very clever about understanding the type system of Common -Lisp and using it to produce efficient 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 +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", \fIi.e.\fR type declarations should be checked at runtime unless the user explicitly tells the system that speed is more important than safety. -The CMU CL version of this compiler reportedly produces pretty good -code for modern machines which have lots of registers, but its code -for the X86 is marred by a lot of extra loads and stores to -stack-based temporary variables. Because of this, and because of the -extra levels of indirection in Common Lisp relative to C, we find a -typical performance decrease by a factor of perhaps 2 to 5 for small -programs coded in SBCL instead of GCC. +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. -.SH DOCUMENTATION - -Currently, the documentation for the system is -.TP 3 -\-- -the user manual -.TP 3 -\-- -this man page -.TP 3 -\-- -doc strings and online help built into the SBCL executable -.PP - .SH SYSTEM REQUIREMENTS -Unlike its distinguished ancestor CMU CL, SBCL is currently on X86 -(Linux, FreeBSD, and OpenBSD) and Alpha (Linux). It would probably be -straightforward to port the CMU CL support for SPARC, or to port to -NetBSD. +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. -As of version 0.6.11, SBCL requires on the order of 16Mb to run. In -some future version, this number could shrink significantly, since -large parts of the system are far from execution bottlenecks and could -reasonably be stored in compact byte compiled form. (CMU CL does this -routinely; the only reason SBCL doesn't currently do this is a -combination of bootstrapping technicalities and inertia.) +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. -.SH ENVIRONMENT +.SH KNOWN BUGS -.TP 10n -.BR SBCL_HOME -If this variable is set, it overrides the default directories for -files like "sbclrc" and "sbcl.core", so that instead of being searched -for in e.g. /etc/, /usr/local/etc/, /usr/lib/, and /usr/local/lib/, they -are searched for only in the directory named by SBCL_HOME. This is -intended to support users who wish to use their own version of SBCL -instead of the version which is currently installed as the system -default. -.PP +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. -.SH FILES - -/usr/lib/sbcl.core and /usr/local/lib/sbcl.core are the standard -locations for the standard SBCL core, unless overridden by the SBCL_HOME -variable. - -/etc/sbclrc and /usr/local/etc/sbclrc are the standard locations for -system-wide SBCL initialization files, unless overridden by the -SBCL_HOME variable or the --sysinit command line option. - - -$HOME/.sbclrc is the standard location for a user's SBCL -initialization file, unless overridden by the --userinit -command line option. - -.SH BUGS - -To report a bug, please send mail to sbcl-help@lists.sourceforge.net -or sbcl-devel@lists.sourceforge.net. As with any software bug report, -it's most helpful if you remember to describe the environment where -the problem occurs (machine type, O/S name and version, etc.) and if -you can provide enough information to reproduce the problem, -preferably in compact form. - -This section attempts to list the most serious and long-standing bugs -or surprising performance hits. 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 -memory. To plagiarize a sadly apt description of a language not -renowned for the production of bulletproof software, "[The current -SBCL implementation of] Common Lisp makes it harder for you to shoot -yourself in the foot, but when you do, the entire universe explodes." -.TP 3 -\-- -The system doesn't deal well with stack overflow. (It tends to cause -a segmentation fault instead of being caught cleanly.) -.TP 3 -\-- -Like CMU CL, the SBCL system overcommits memory at startup. 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 (!). -.PP - -The compiler is overaggressive about static typing, assuming that a -function's return type never changes. Thus compiling and loading a -file containing -(DEFUN FOO (X) NIL) -(DEFUN BAR (X) (IF (FOO X) 1 2)) -(DEFUN FOO (X) (PLUSP X)) -then running (FOO 1) gives 2 (because the compiler "knew" -that FOO's return type is NULL). +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 -never compiled code to check the declaration. - -The implementation of multidimensional arrays, especially -multidimensional arrays of floating point numbers, is very -inefficient. - -SYMBOL-FUNCTION is much slower than you might expect, being -implemented not as a slot access but as a search through the -compiler/kernel "globaldb" database. - -CLOS (based on the PCL reference implementation) is somewhat -inefficient. - -There are many nagging pre-ANSIisms, e.g. -.TP 3 -\-- -CLOS (based on the PCL reference implementation) is incompletely -integrated into the system, so that e.g. SB-PCL::FIND-CLASS is a -different function than CL::FIND-CLASS. (This is less of a problem in -practice than the speed, but it's still distasteful.) -.TP 3 --- -The ANSI-recommended idiom for creating a function which is only -sometimes expanded inline, -(DECLAIM (INLINE F)) -(DEFUN F ...) -(DECLAIM (NOTINLINE F)), -doesn't do what you'd expect. (Instead, you have to declare the -function as SB-EXT:MAYBE-INLINE to get the desired effect.) +adheres to. Using \f(CRPROCLAIM\fR or \f(CRDECLAIM\fR to specify the +return type of a function causes the compiler to believe you without +checking. Thus compiling a file containing +\f(CR + (DECLAIM (FTYPE (FUNCTION (T) NULL) SOMETIMES)) + (DEFUN SOMETIMES (X) (ODDP X)) + (DEFUN FOO (X) (IF (SOMETIMES X) \(aqTHIS\-TIME \(aqNOT\-THIS\-TIME))\fR +.br +then running \f(CR(FOO 1)\fR gives \f(CRNOT\-THIS\-TIME\fR, because +the compiler relied on the truth of the \f(CRDECLAIM\fR without checking it. + +Some things are implemented very inefficiently. .TP 3 \-- -The DYNAMIC-EXTENT declaration is not implemented, and is simply -ignored. (This is allowed by the ANSI spec, but can have a large -efficiency cost in some kinds of code, e.g. code which uses a lot -of upward closures or &REST lists.) -.TP 3 --- -Compiling DEFSTRUCT in strange places (e.g. inside a DEFUN) doesn't -do anything like what it should. +Multidimensional arrays are inefficient, especially +multidimensional arrays of floating point numbers. .TP 3 \-- -The symbol * is the name of a type similar to T. (It's used as part of -the implementation of compound types like (ARRAY * 1) and (CONS * *). -In a strict ANSI implementation, * would not be the name of a type, -but instead just a symbol which is recognized and handled specially by -certain type expanders.) +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 +\f(CRSQRT\fR and \f(CRAREF\fR, 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. .PP +.SH 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 <\f(CRhttp://sbcl.sourceforge.net/\fR>; 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 \f(CR(TAN LEAST\-NEGATIVE\-SINGLE\-FLOAT)\fR interactively on +sbcl-1.2.3 on my Linux 4.5 X86 box, I get an \f(CRUNBOUND\-VARIABLE\fR +error." + +.SH 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 (\fIe.g.\fR +\f(CRLETF\fR, \f(CRITERATE\fR, \f(CRMEMQ\fR, \f(CRREQUIRED\-ARGUMENT\fR), +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.) + .SH SUPPORT Various information about SBCL is available at -. The mailing lists there are the -recommended place to look for support. +<\f(CRhttp://www.sbcl.org/\fR>. The mailing lists there are the recommended +place to look for support. + +.SH 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. + +.SH ENVIRONMENT -.SH DISTRIBUTION +.TP 10n +.BR 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 \fIe.g.\fR by a third-party +packager. -SBCL is a free implementation of Common Lisp derived from CMU CL. Both -sources and executables are freely available; this software is "as -is", and has no warranty of any kind. CMU and the authors assume no -responsibility for the consequences of any use of this software. See -the CREDITS file in the distribution for more information about -history, contributors and permissions. +.SH FILES +.TP +.I sbcl +executable program containing some low-level runtime support and +a loader, used to read sbcl.core +.TP +.I sbcl.core +dumped memory image containing most of SBCL, to be loaded by +the `sbcl' executable. Looked for in $\f(CRSBCL_HOME\fR, +unless overridden by the \f(CR\-\-core\fR option. +.TP +.I sbclrc +optional system-wide startup script, looked for in $\f(CRSBCL_HOME\fR/sbclrc +then /etc/sbclrc, unless overridden by the \f(CR\-\-sysinit\fR command line +option. +.TP +.I .sbclrc +optional per-user customizable startup script (in user's home +directory, or as specified by \f(CR\-\-userinit\fR) + +.SH SEE ALSO + +Full SBCL documentation is maintained as a Texinfo manual. If is has +been installed, the command +.IP +.B info sbcl +.PP +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. +.IP +.B /usr/local/share/doc/sbcl/ +.PP +See the SBCL homepage +.IP +.B <\f(CRhttp://www.sbcl.org/\fR> +.PP +for more information, including directions on how to subscribe to the +sbcl\-devel and sbcl\-help mailing-lists.