1 ;;;; tags which are set during the build process and which end up in
2 ;;;; CL:*FEATURES* in the target SBCL, plus some comments about other
3 ;;;; CL:*FEATURES* tags which have special meaning to SBCL or which
4 ;;;; have a special conventional meaning
6 ;;;; Note that the preferred way to customize the features of a local
7 ;;;; build of SBCL is not to edit this file, but to tweak
8 ;;;; customize-target-features.lisp.
10 ;;;; This software is part of the SBCL system. See the README file for
11 ;;;; more information.
13 ;;;; This software is derived from the CMU CL system, which was
14 ;;;; written at Carnegie Mellon University and released into the
15 ;;;; public domain. The software is in the public domain and is
16 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
17 ;;;; files for more information.
21 ;; features present in all builds
26 ;; FIXME: Isn't there a :x3jsomething feature which we should set too?
31 ;; Douglas Thomas Crosher's conservative generational GC (the only one
32 ;; we currently support)
35 ;; We're running under a UNIX. This is sort of redundant, and it was also
36 ;; sort of redundant under CMU CL, which we inherited it from: neither SBCL
37 ;; nor CMU CL supports anything but UNIX (and "technically not UNIX"es
38 ;; such as *BSD and Linux). But someday, maybe we might, and in that case
39 ;; we'd presumably remove this, so its presence conveys the information
40 ;; that the system isn't one which follows such a change.
44 ;; features present in this particular build
47 ;; Setting this enables the compilation of documentation strings
48 ;; from the system sources into the target Lisp executable.
49 ;; Traditional Common Lisp folk will want this option set.
50 ;; I (WHN) made it optional because I came to Common Lisp from
51 ;; C++ through Scheme, so I'm accustomed to asking
52 ;; Emacs about things that I'm curious about instead of asking
53 ;; the executable I'm running.
56 ;; When this is set, EVAL is implemented as an "IR1 interpreter":
57 ;; code is compiled into the compiler's first internal representation,
58 ;; then the IR1 is interpreted. When this is not set, EVAL is implemented
59 ;; as a little bit of hackery wrapped around a call to COMPILE, i.e.
60 ;; the system becomes a "compiler-only implementation" of Common Lisp.
61 ;; As of sbcl-0.6.7, the compiler-only implementation is prototype code,
62 ;; and much less mature than the old IR1 interpreter. Thus, the safe
63 ;; thing is to leave :SB-INTERPRETER set. However, the compiler-only
64 ;; system is noticeably smaller, so you might want to omit
65 ;; :SB-INTERPRETER if you have a small machine.
67 ;; Probably, the compiler-only implementation will become more
68 ;; stable someday, and support for the IR1 interpreter will then be
69 ;; dropped. This will make the system smaller and easier to maintain
70 ;; not only because we no longer need to support the interpreter,
71 ;; but because code elsewhere in the system (the dumper, the debugger,
72 ;; etc.) no longer needs special cases for interpreted code.
75 ;; Do regression and other tests when building the system. You
76 ;; might or might not want this if you're not a developer,
77 ;; depending on how paranoid you are. You probably do want it if
78 ;; you are a developer.
81 ;; :SB-PROPAGATE-FLOAT-TYPE and :SB-PROPAGATE-FUN-TYPE enable
82 ;; some numeric optimizer code in the target compiler. They
83 ;; correspond to the :PROPAGATE-FLOAT-TYPE and :PROPAGATE-FUN-TYPE
84 ;; features in the original CMU CL code, and while documentation
85 ;; existed for those, it seemed a little inconsistent. Despite the
86 ;; name, :SB-PROPAGATE-FLOAT-TYPE seems to control not only
87 ;; floating point optimizations, but some integer optimizations as
90 ;; CROSS-FLOAT-INFINITY-KLUDGE:
91 ;; * Even when these target features are enabled, the optimizations
92 ;; aren't enabled in the cross-compiler, because some of them
93 ;; depend on floating point infinities, which aren't in general
94 ;; supported on the cross-compilation host.
95 ;; * This is supported by hacking the features out of the
96 ;; *SHEBANG-FEATURES* list while we're building the cross-compiler.
97 ;; This is ugly and confusing and weird, but all the alternatives
98 ;; that I could think of seem messy and error-prone. That doesn't
99 ;; mean there's not a better way, though. Suggestions are welcome;
100 ;; or if you'd like to submit patches to make this code work
101 ;; without requiring floating point infinities, so that the entire
102 ;; problem goes away, that might be even better! -- WHN 2001-03-22
103 :sb-propagate-float-type
104 :sb-propagate-fun-type
106 ;; Setting this makes more debugging information available.
107 ;; If you aren't hacking or troubleshooting SBCL itself, you
108 ;; probably don't want this set.
110 ;; At least two varieties of debugging information are enabled by this
112 ;; * SBCL is compiled with a higher level of OPTIMIZE DEBUG, so that
113 ;; the debugger can tell more about the state of the system.
114 ;; * Various code to print debugging messages, and similar debugging code,
115 ;; is compiled only when this feature is present.
117 ;; Note that the extra information recorded by the compiler at
118 ;; this higher level of OPTIMIZE DEBUG includes the source location
119 ;; forms. In order for the debugger to use this information, it has to
120 ;; re-READ the source file. In an ordinary installation of SBCL, this
121 ;; re-READing may not work very well, for either of two reasons:
122 ;; * The sources aren't present on the system in the same location that
123 ;; they were on the system where SBCL was compiled.
124 ;; * SBCL is using the standard readtable, without the added hackage
125 ;; which allows it to handle things like target features.
126 ;; If you want to be able to use the extra debugging information,
127 ;; therefore, be sure to keep the sources around, and run with the
128 ;; readtable configured so that the system sources can be read.
131 ;; Enable extra debugging output in the assem.lisp assembler/scheduler
132 ;; code. (This is the feature which was called :DEBUG in the
133 ;; original CMU CL code.)
136 ;; Setting this makes SBCL more "fluid", i.e. more amenable to
137 ;; modification at runtime, by suppressing various INLINE declarations,
138 ;; compiler macro definitions, FREEZE-TYPE declarations; and by
139 ;; suppressing various burning-our-ships-behind-us actions after
140 ;; initialization is complete; and so forth. This tends to clobber the
141 ;; performance of the system, so unless you have some special need for
142 ;; this when hacking SBCL itself, you don't want this set.
145 ;; Enable code for collecting statistics on usage of various operations,
146 ;; useful for performance tuning of the SBCL system itself. This code
147 ;; is probably pretty stale (having not been tested since the fork from
148 ;; base CMU CL) but might nonetheless be a useful starting point for
149 ;; anyone who wants to collect such statistics in the future.
152 ;; Peter Van Eynde's increase-bulletproofness code
154 ;; This is not maintained or tested in current SBCL, but I haven't
155 ;; gone out of my way to remove or break it, either.
158 ; :high-security-support
160 ;; multiprocessing support
162 ;; This is not maintained or tested in current SBCL. I haven't gone out
163 ;; of my way to break it, but since it's derived from an old version of
164 ;; CMU CL where multiprocessing was pretty shaky, it's likely to be very
166 ;; :MP enables multiprocessing
167 ;; :MP-I486 is used, only within the multiprocessing code, to control
168 ;; what seems to control processor-version-specific code. It's
169 ;; probably for 486 or later, i.e. could be set as long as
170 ;; you know you're not running on a 386, but it doesn't seem
171 ;; to be documented anywhere, so that's just a guess.
175 ;; This affects the definition of a lot of things in bignum.lisp. It
176 ;; doesn't seem to be documented anywhere what systems it might apply
177 ;; to. It doesn't seem to be needed for X86 systems anyway.
180 ;; This is probably true for some processor types, but not X86. It
181 ;; affects a lot of floating point code.
182 ; :negative-zero-is-not-zero
184 ;; It's unclear to me what this does (but it was enabled in the code
185 ;; that I picked up from Peter Van Eynde, called CONSTRAIN-FLOAT-TYPE
186 ;; instead of SB-CONSTRAIN-FLOAT-TYPE). -- WHN 19990224
187 :sb-constrain-float-type
189 ;; This is set in classic CMU CL, and presumably there it means
190 ;; that the floating point arithmetic implementation
191 ;; conforms to IEEE's standard. Here it definitely means that the
192 ;; floating point arithmetic implementation conforms to IEEE's standard.
193 ;; I (WHN 19990702) haven't tried to verify
194 ;; that it does conform, but it should at least mostly conform (because
195 ;; the underlying x86 hardware tries).
198 ;; This seems to be the pre-GENCGC garbage collector for CMU CL, which was
199 ;; AFAIK never supported for the X86.
202 ;; CMU CL had, and we inherited, code to support 80-bit LONG-FLOAT on the x86
203 ;; architecture. Nothing has been done to actively destroy the long float
204 ;; support, but it hasn't been thoroughly maintained, and needs at least
205 ;; some maintenance before it will work. (E.g. the LONG-FLOAT-only parts of
206 ;; genesis are still implemented in terms of unportable CMU CL functions
207 ;; which are not longer available at genesis time in SBCL.) A deeper
208 ;; problem is SBCL's bootstrap process implicitly assumes that the
209 ;; cross-compilation host will be able to make the same distinctions
210 ;; between floating point types that it does. This assumption is
211 ;; fundamentally sleazy, even though in practice it's unlikely to break down
212 ;; w.r.t. distinguishing SINGLE-FLOAT from DOUBLE-FLOAT; it's much more
213 ;; likely to break down w.r.t. distinguishing DOUBLE-FLOAT from LONG-FLOAT.
214 ;; Still it's likely to be quite doable to get LONG-FLOAT support working
215 ;; again, if anyone's sufficiently motivated.
219 ;; miscellaneous notes on other things which could have special significance
220 ;; in the *FEATURES* list
223 ;; notes on the :NIL and :IGNORE features:
225 ;; #+NIL is used to comment out forms. Occasionally #+IGNORE is used
226 ;; for this too. So don't use :NIL or :IGNORE as the names of features..
228 ;; notes on :SB-XC and :SB-XC-HOST features (which aren't controlled by this
229 ;; file, but are instead temporarily pushed onto *FEATURES* or
230 ;; *TARGET-FEATURES* during some phases of cross-compilation):
232 ;; :SB-XC-HOST stands for "cross-compilation host" and is in *FEATURES*
233 ;; during the first phase of cross-compilation bootstrapping, when the
234 ;; host Lisp is being used to compile the cross-compiler.
236 ;; :SB-XC stands for "cross compiler", and is in *FEATURES* during the second
237 ;; phase of cross-compilation bootstrapping, when the cross-compiler is
238 ;; being used to create the first target Lisp.
240 ;; notes on the :SB-ASSEMBLING feature (which isn't controlled by
243 ;; This is a flag for whether we're in the assembler. It's
244 ;; temporarily pushed onto the *FEATURES* list in the setup for
245 ;; the ASSEMBLE-FILE function. It would be a bad idea
246 ;; to use it as a name for a permanent feature.
248 ;; notes on local features (which are set automatically by the
249 ;; configuration script, and should not be set here unless you
250 ;; really, really know what you're doing):
252 ;; machine architecture features:
253 ;; :x86 ; any Intel 386 or better, or compatibles like the AMD K6 or K7
254 ;; (No others are supported by SBCL as of 0.6.7, but :alpha or
255 ;; :sparc support could be ported from CMU CL if anyone is
256 ;; sufficiently motivated to do so.)
257 ;; (CMU CL also had a :pentium feature, which affected the definition
258 ;; of some floating point vops. It was present but not enabled in the
259 ;; CMU CL code that SBCL is derived from, and is present but stale
260 ;; in SBCL as of 0.6.7.)
262 ;; operating system features:
263 ;; :linux = We're intended to run under some version of Linux.
264 ;; :bsd = We're intended to run under some version of BSD Unix. (This
265 ;; is not exclusive with the features which indicate which
266 ;; particular version of BSD we're intended to run under.)
267 ;; :freebsd = We're intended to run under FreeBSD.
268 ;; :openbsd = We're intended to run under FreeBSD.
269 ;; (No others are supported by SBCL as of 0.6.7, but :hpux or
270 ;; :solaris support could be ported from CMU CL if anyone is
271 ;; sufficiently motivated to do so.)