X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=doc%2Fbeyond-ansi.sgml;h=913848978f4c71333d94ff323e2666d069e1148b;hb=1b650be8b800cf96e2c268ae317fb26d0bf36827;hp=b1c0a39a32b301bf7aa883f11018530091b0faed;hpb=abbf4da893fae087978fcdf544c85187ea9c2a9d;p=sbcl.git diff --git a/doc/beyond-ansi.sgml b/doc/beyond-ansi.sgml index b1c0a39..9138489 100644 --- a/doc/beyond-ansi.sgml +++ b/doc/beyond-ansi.sgml @@ -48,7 +48,7 @@ of the same symbol more than once is undefined unless the new value is eql to the old value. Conforming to this specification is a nuisance when the "constant" value is only constant under some weaker test like string= or equal. It's -especially annoying because defconstant takes effect +especially annoying because, in &SBCL;, defconstant takes effect not only at load time but also at compile time, so that just compiling and loading reasonable code like (defconstant +foobyte+ '(1 4)) @@ -63,7 +63,11 @@ E.g., the code above can be given an exactly defined meaning by replacing defconstant either with defparameter or with a customized macro which does the right thing, possibly along the lines of the defconstant-eqx macro used internally in the -implementation of SBCL itself. +implementation of &SBCL; itself. In circumstances where this is not +appropriate, the programmer can handle the condition type +sb-ext:defconstant-uneql, and choose either the +continue or abort restart as +appropriate. &SBCL; gives style warnings about various kinds of perfectly legal code, e.g. @@ -138,7 +142,7 @@ current bugs) are: Threading (a.k.a Multiprocessing)</> -<para>&SBCL; (as of version 0.x.y, on Linux x86 only) supports a +<para>&SBCL; (as of version 0.8.3, on Linux x86 only) supports a fairly low-level threading interface that maps onto the host operating system's concept of threads or lightweight processes. @@ -210,20 +214,20 @@ and woken with SIGCONT. <para>&SBCL; at present will alway have at least two tasks running as seen from Linux: when the first process has done startup initialization (mapping files in place, installing signal handlers -etc) it creates a new thread to run the Lisp startup and initial listener. -The original thread is then used to run GC and to reap dead subthreads -when they exit. +etc) it creates a new thread to run the Lisp startup and initial +listener. The original thread stays around to reap dead subthreads +and deallocate their resources (e.g. stacks) when they exit. <para>Garbage collection is done with the existing Conservative Generational GC. Allocation is done in small (typically 8k) regions : each thread has its own region so this involves no stopping. However, when a region fills, a lock must be obtained while another is allocated, and when a collection is required, all processes are -stopped. This is achieved using <function>ptrace()</function>, so you -should be very careful if you wish to examine an &SBCL; worker thread -using <command>strace</command>, <command>truss</command>, -<command>gdb</command> or similar. It may be prudent to disable GC -before doing so. +stopped. This is achieved by sending them signals, which may make for +interesting behaviour if they are interrupted in system calls. The +streams interface is believed to handle the required system call +restarting correctly, but this may be a consideration when making +other blocking calls e.g. from foreign library code. <para>Large amounts of the &SBCL; library have not been inspected for thread-safety. Some of the obviously unsafe areas have large locks @@ -237,7 +241,7 @@ on keyboard interrupt handling: pressing your terminal's intr key process group, including Lisp threads that &SBCL; considers to be notionally `background'. This is undesirable, so background threads are set to ignore the SIGINT signal. Arbitration for the input stream -is managed by locking on sb-thread::*session-lock* +is managed by locking on <varname>sb-thread::*session-lock*</varname> <para>A thread can be created in a new Lisp 'session' (new terminal or window) using <function>sb-thread:make-listener-thread</function>. @@ -332,11 +336,9 @@ fixed addresses, a precondition for using copy-on-write to share code between multiple Lisp processes. is less important with modern generational garbage collectors. </para> -<para>The <function>sb-ext:truly-the</> operator does what the -<function>cl:the</> operator does in a more conventional -implementation of &CommonLisp;, declaring the type of its argument -without any runtime checks. (Ordinarily in &SBCL;, any type -declaration is treated as an assertion and checked at runtime.)</para> +<para>The <function>sb-ext:truly-the</> declares the type of the +result of the operations, producing its argument; the declaration is +not checked. In short: don't use it.</para> <para>The <function>sb-ext:freeze-type</> declaration declares that a type will never change, which can make type testing @@ -349,9 +351,11 @@ to it. This is appropriate for functions like <function>sqrt</>, but is <emphasis>not</> appropriate for functions like <function>aref</>, which can change their return values when the underlying data are changed.</para> +<!-- FIXME: This declaration does not seem to be supported in the -- + -- current compiler. --> </sect2> </sect1> -</chapter> \ No newline at end of file +</chapter>