X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=doc%2Fsbcl.1;h=92eb13f012fe9d476831300d8b487d40458825c1;hb=80304981972c91c1b3f3fca75f36dacf1fecf307;hp=dc06a67c56f81601b29fc864eb45aa2d07caaca4;hpb=a530bbe337109d898d5b4a001fc8f1afa3b5dc39;p=sbcl.git diff --git a/doc/sbcl.1 b/doc/sbcl.1 index dc06a67..92eb13f 100644 --- a/doc/sbcl.1 +++ b/doc/sbcl.1 @@ -10,9 +10,9 @@ .\" If you want to use this code or any part of CMU Common Lisp, please .\" contact Scott Fahlman or slisp-group@cs.cmu.edu. .\" ********************************************************************** +.\" Most of SBCL, including this man page, is in the public domain. See +.\" COPYING in the distribution for more information. .\" -.\" $Header$ -.\" FIXME: The date below should be $Date$. .TH SBCL 1 "$Date$" .AT 3 .SH NAME @@ -25,6 +25,179 @@ 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.) +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" at the command line with no arguments. (SBCL +understands command line arguments, but you probably won't need to use +them unless you're a fairly advanced user, in which case you should +read the COMMAND LINE SYNTAX section, below.) You should see some +startup messages, then a prompt ("*"). Type a Lisp expression at the +prompt, and SBCL will read it, execute it, print the result, +give you another prompt, and wait for your next input. E.g. + * (+ 1 2 3) + 6 + * + +Many people like to run SBCL, like other Lisp systems, as a subprocess +under Emacs. The Emacs "ilisp" 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. + +.SH OVERVIEW + +SBCL aims for but has not reached ANSI compliance. + +SBCL compiles Common Lisp to native code, and is essentially a +"compiler-only" implementation of the ANSI standard. (Unlike earlier +versions of SBCL, byte compilation is no longer supported, and there +is only a vestigial interpreter. Thus, in particular, +COMPILED-FUNCTION-P is always equal to FUNCTIONP.) + +SBCL uses a generational conservative garbage collector for some ports, +and a simple stop-and-copy garbage collector for other ports. + +SBCL also includes some non-ANSI extensions, notably + * Lispy extensions: + ** CMU-CL-style safe implementation of type declarations: + "Declarations are assertions." + ** source level debugger + ** profiler + ** saving the state of the running SBCL process, producing a + "core" file which can be restarted later + ** Gray streams (overloadable CLOS classes whose instances can + be used wherever ANSI streams can be used) + ** weak pointers and finalization (which have unfortunately + suffered from at least some code rot, e.g. weak hash tables + don't work) + * system interface extensions: + ** calling out to C code (a.k.a. FFI, foreign function interface) + ** some simple support for operations with a "scripting language" + flavor, e.g. reading POSIX argc and argv, or executing a + subprogram + +.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 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 + +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 +.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 + +As noted above, SBCL is essentially a compiler-only implementation of +Lisp, with all nontrivial code being implemented by compilation, even +when you type it interactively at the "interpreter" prompt. + +SBCL inherits from CMU CL the "Python" native code compiler. (Though +we've essentially dropped the name 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 CMU CL version of this compiler reportedly produces pretty good +code for modern CPU architectures 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, the +performance of SBCL isn't going to impress people who are impressed by +small constant factors. However, even on the X86 it tends to be faster +than byte interpreted languages (and can be a lot faster). + +For more information about the compiler, see the user manual. + +.SH DOCUMENTATION + +Currently, the documentation for the system is +.TP 3 +\-- +this man page +.TP 3 +\-- +the user manual +.TP 3 +\-- +doc strings and online help built into the SBCL executable +.PP + .SH COMMAND LINE SYNTAX Command line syntax can be considered an advanced topic; for ordinary @@ -39,7 +212,7 @@ runtime environment, some command line arguments are processed during the initialization of the Common Lisp system, and any remaining command line arguments are passed on to user code. -The full, unambiguous syntax for SBCL is +The full, unambiguous syntax for invoking SBCL at the command line is .TP 3 .B sbcl [runtime options] --end-runtime-options [toplevel options] --end-toplevel-options [user options] .PP @@ -59,12 +232,13 @@ Supported runtime options are .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 accept the standard toplevel options. +run a nonstandard toplevel which does not recognize the standard toplevel +options. .TP 3 .B --noinform Suppress the printing of any banner or other informational message at -startup. (Combined with the --noprint toplevel option, this makes it -straightforward to write Lisp "scripts" which work as Unix pipes.) +startup. (This makes it easier to write Lisp programs which work in +Unix pipelines. See also the "--noprogrammer" and "--noprint" options.) .PP In the future, runtime options may be added to control behavior such @@ -77,42 +251,38 @@ Lisp toplevel logic gets a chance to see it. Supported toplevel options for the standard SBCL core are .TP 3 .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. +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. .TP 3 .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. +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. .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, 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. .TP 3 .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 straightforward to write Lisp -"scripts" which work as Unix pipe utilities.) +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. .TP 3 .B --noprogrammer -Ordinarily the system initializes *DEBUG-IO* to *TERMINAL-IO*. -When the --notty option is set, however, *DEBUG-IO* is instead -set to a stream which sends its output to *ERROR-OUTPUT* and -which raises an error on input. As a result, any attempt by the -program to get programmer feedback through the debugger -causes an error which abnormally terminates the entire -Lisp environment. (This can be useful behavior for programs -which are to run without programmer supervision.) +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 @@ -123,123 +293,26 @@ 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 from 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. +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. -.SH OVERVIEW - -SBCL aims for but has not reached ANSI compliance. - -SBCL compiles Lisp to native code, or optionally to more-compact but -much slower byte code. - -SBCL's garbage collector is generational and conservative. - -SBCL includes a source level debugger, as well as the ANSI TRACE -facility and a rudimentary profiler. - -.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.) - -Many extensions supported by CMU CL, like 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. - -SBCL has retained some extensions of its parent CMU CL. Many -of them are in three categories: -.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 an operator to cause a particular string to be compiled into a fasl -file) -.TP 3 -\-- -non-portable performance hacks (e.g. PURIFY, which causes -everything currently in existence to become immune to GC) -.TP 3 -\-- -things which might be in the new ANSI spec (e.g. weak pointers, -finalization, foreign function interface to C, and Gray streams) -.PP - -There are also various retained extensions which don't fall into -any particular category, e.g. -.TP 3 -\-- -the ability to save running Lisp images as executable files -.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. - -.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 -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. - -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 only -supported on X86. Linux and FreeBSD are currently available. It would -probably be straightforward to port the CMU CL support for Alpha or -SPARC as well, or to OpenBSD or NetBSD, but at the time of this -writing no such efforts are underway. +Unlike its distinguished ancestor CMU CL, SBCL currently runs only on X86 +(Linux, FreeBSD, and OpenBSD) and Alpha (Linux). For information on +other ongoing ports, see the sbcl-devel mailing list, and/or the +web site. -As of version 0.6.3, 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. .SH ENVIRONMENT @@ -262,17 +335,17 @@ 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. +SBCL_HOME variable or the --sysinit command line option. $HOME/.sbclrc is the standard location for a user's SBCL -initialization file. +initialization file, unless overridden by the --userinit +command line option. -.SH BUGS +.SH KNOWN BUGS -Too numerous to list, alas. This section attempts to list the most -serious known bugs, and a reasonably representative sampling of -others. For more information on bugs, see the BUGS file in the -distribution. +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 memory. To plagiarize a sadly apt description of a language not @@ -281,31 +354,16 @@ 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. +The system doesn't deal well with stack overflow. (It tends to cause +a segmentation fault instead of being caught cleanly.) .TP 3 \-- -The SBCL system overcommits memory at startup. On typical Unix-alikes -like Linux and *BSD, this can cause other processes to be killed -randomly (!) if the SBCL system turns out to use more virtual memory -than the system has available for it. +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 facility for dumping a running Lisp image to disk gets confused -when run without the PURIFY option, and creates an unnecessarily large -core file (apparently representing memory usage up to the previous -high-water mark). Moreover, when the file is loaded, it confuses the -GC, so that thereafter memory usage can never be reduced below that -level. - -By default, 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). - 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 @@ -317,27 +375,48 @@ compiling a file containing then running (FOO 1) gives NOT-THIS-TIME, because the never compiled code to check the declaration. -The TRACE facility can't be used on some kinds of functions. - -The profiler is flaky, e.g. sometimes it fails by throwing a -signal instead of giving you a result. - -SYMBOL-FUNCTION is much slower than you'd 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 quite slow. - -The interpreter's pre-processing freezes in the macro definitions in effect at -the time an interpreted function is defined. +Some things are implemented very inefficiently. +.TP 3 +\-- +Multidimensional arrays are inefficient, especially +multidimensional arrays of floating point numbers +.TP 3 +\-- +The DYNAMIC-EXTENT declaration isn't implemented at all, not even +for &REST lists or upward closures, so such constructs always allocate +their temporary storage from the heap, causing GC overhead. +.TP 3 +\-- +CLOS isn't particularly efficient. (In part, CLOS is so dynamic +that it's slow for fundamental reasons, but beyond that, the +SBCL implementation of CLOS doesn't do some important known +optimizations.) +.TP 3 +\-- +SBCL, like most implementations of Common Lisp, has trouble +passing floating point numbers around efficiently, because +they're 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 a floating point +number as a function argument (or returning a floating point +number as a function value) is a fundamentally slow operation. +.PP -There are many nagging pre-ANSIisms, e.g. +There are still some nagging pre-ANSIisms, notably .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.) +different function than CL::FIND-CLASS. (In practice, you need to +be a pretty advanced user before this is a serious problem, and +by then you can usually work around it, but it's still distasteful. +It's arguably the outstanding "This should be fixed by version 1.0" +issue.) .TP 3 -- The ANSI-recommended idiom for creating a function which is only @@ -348,36 +427,38 @@ sometimes expanded inline, doesn't do what you'd expect. (Instead, you have to declare the function as SB-EXT:MAYBE-INLINE to get the desired effect.) .TP 3 --- -Compiling DEFSTRUCT in strange places (e.g. inside a DEFUN) doesn't -do anything like what it should. -.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).) -.TP 3 -\-- -The DESCRIBE facility doesn't use CLOS (PRINT-OBJECT, etc.) as it should. -Instead it is based on old hardwired TYPECASEs. -.TP 3 \-- -The printer doesn't use CLOS (PRINT-OBJECT, etc.) everywhere it should. -Instead it still uses old hardwired TYPECASEs. (This one is not as -annoying as it sounds, since the printer does use PRINT-OBJECT in the -places where it tends to matter most.) +There are several nonconforming bits of type syntax. E.g. (1) The type +FOO is strictly equivalent to (FOO), so e.g. the type OR is treated as +the type (OR), i.e. the empty type. This is the way that the ancestral +code worked, and even though ANSI specifically forbids it, it hasn't +been fixed yet. (2) 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.) .PP -.SH SUPPORT +.SH REPORTING BUGS + +To report a bug, please send mail to sbcl-help@lists.sourceforge.net +or sbcl-devel@lists.sourceforge.net. -Please send bug reports or other information to -. +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. E.g. "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." + +.SH SUPPORT -.SH DISTRIBUTION +Various information about SBCL is available at +. The mailing lists there are the +recommended place to look for support. -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 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.