Gambit-list Février 2012

gambit-list@iro.umontreal.ca

22 participants
26 discussions

Edge triggered I/O with libevent
by Adam Langley 04 Avr '13

04 Avr '13

Gambit uses the select call on POSIX systems to multiplex IO operations. This is fine for small numbers of file descriptors, but falls apart quickly with large numbers[1]. libevent[2] is a wrapper library around a number of modern IO multiplexing systems (epoll on Linux, kqueue on the BSDs as well as poll and select). Attached is a patch which converts Gambit to using edge triggered I/O with epoll and libevent. This also requires a patch (attached) of libevent since the standard distribution doesn't include edge triggering support and the upstream appears to be on holiday. (epoll is required because I don't have a BSD box on which to develop edge triggering support for kqueue) This patch (for Gambit) preprocesses away to nothing unless --enable-libevent is passed to the configure script. (Note that, since this patches the configure.ac script, you'll need to run autoconf to regenerate). I hope I've not broken anything, but at this stage I've only tested that the console and tcp ports work. This patch (in the future) should also allow people, who write programs which use socket calls directly, to integrate into the main event loop at some point. Testing is more than welcome and, if you find a form of IO which is broken, please email me. [1] http://monkey.org/~provos/libevent/libevent-benchmark2.jpg [2] http://monkey.org/~provos/libevent/ -- Adam Langley agl(a)imperialviolet.org http://www.imperialviolet.org (+44) (0)7906 332512 PGP: 9113 256A CC0F 71A6 4C84 5087 CDA5 52DF 2CB6 3D60

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Problem with FFI & Memory Corruption
by Taylor Venable 12 Mar '12

12 Mar '12

Hail, brothers and sisters in Scheme. I've been working with Gambit's FFI recently, trying to create bindings for libxml2. Currently I'm trying to use libxml2 to parse a file, and produce structures representing the XML nodes. Reading Gambit's lib/os.c for some examples of how to produce such things (I started with service-info and worked down from there) I developed some code that pretty much works. But there are problems with memory corruption that result in "odd" looking results (for example, a list that should have some 95,000 items is instead two large fixnums consed together) or segfaults. Finally I teased out an XML file that fails pretty reliably, at least on my desktop. First, the code is on Bitbucket --- https://bitbucket.org/taylor_venable/gambit-xml/. The default Makefile target will build xml.o1 - you will probably have to invoke it as "make GSC=gsc" (the Makefile uses "GSC=gambitc" by default, which is the name used by the Gambit compiler on Arch Linux since the "gsc" program is from Ghostscript). Second, the test XML file is on my website --- http://metasyntax.net/test.xml.gz --- warning about clicking that in your browser, it's 141 MB uncompressed. Here's how I'm using things: $ make gcc -c -o os_xml.o -I/usr/include/libxml2 -g -O0 -Wall -Wno-unused -fPIC os_xml.c gambitc -debug -link -flat -o xml.o1.c xml.scm *** WARNING -- "##direct-structure-ref" is not defined, *** referenced in: ("/home/taylor/Repos/gambit-xml/xml.c") *** WARNING -- "##direct-structure-set!" is not defined, *** referenced in: ("/home/taylor/Repos/gambit-xml/xml.c") *** WARNING -- "##structure" is not defined, *** referenced in: ("/home/taylor/Repos/gambit-xml/xml.c") *** WARNING -- "##structure-instance-of?" is not defined, *** referenced in: ("/home/taylor/Repos/gambit-xml/xml.c") *** WARNING -- "##structure-type-set!" is not defined, *** referenced in: ("/home/taylor/Repos/gambit-xml/xml.c") *** WARNING -- "##subtype-set!" is not defined, *** referenced in: ("/home/taylor/Repos/gambit-xml/xml.c") *** WARNING -- "error" is not defined, *** referenced in: ("/home/taylor/Repos/gambit-xml/xml.c") *** WARNING -- "fx=" is not defined, *** referenced in: ("/home/taylor/Repos/gambit-xml/xml.c") *** WARNING -- "map" is not defined, *** referenced in: ("/home/taylor/Repos/gambit-xml/xml.c") *** WARNING -- "vector-ref" is not defined, *** referenced in: ("/home/taylor/Repos/gambit-xml/xml.c") gcc -c -o xml.o -I/usr/include/libxml2 -D___DYNAMIC -g -O0 -Wall -Wno-unused -fPIC xml.c gcc -c -o xml.o1.o -I/usr/include/libxml2 -D___DYNAMIC -g -O0 -Wall -Wno-unused -fPIC xml.o1.c gcc -shared -o xml.o1 -lxml2 os_xml.o xml.o xml.o1.o $ gsi Gambit v4.6.3 > (load "xml") "/home/taylor/Repos/gambit-xml/xml.o1" > (define xml (read-xml "./test.xml")) > (length (xml-element-children (xml-document-root xml))) Segmentation fault Sometimes I can do this: $ gsi Gambit v4.6.3 > (load "xml") "/home/taylor/Repos/gambit-xml/xml.o1" > (define xml (read-xml "./test.xml")) > (length (xml-element-children (xml-document-root xml))) *** ERROR IN (console)(a)4.9 -- (Argument 1) Instance of #<type #2 xml-element> expected (xml-element-children '#<gc-hash-table #3>) 1> > xml #<xml-document #4 location: "./test.xml" root: #<gc-hash-table #3>> Or this: $ gsi Gambit v4.6.3 > (load "xml") "/home/taylor/Repos/gambit-xml/xml.o1" > (define xml (read-xml "/home/taylor/sis-conv-input.xml")) > (length (xml-element-children (xml-document-root xml))) *** ERROR IN (console)(a)3.1 -- (Argument 1) LIST expected (length '(23220778 . 22958618)) 1> xml #<xml-document #2 location: "/home/taylor/sis-conv-input.xml" root: #<xml-element #3 name: "enterprise" attrs: () children: (23220778 . 22958618)>> It varies. Sometimes I get the error because children is a something like '(23220778 . 22958618), then when I print out the xml value, the root is printed as #<gc-hash-table #3>. So it looks to me like a memory corruption problem, but I don't know why. When I use gdb to look for a cause: $ gdb gsi GNU gdb (GDB) 7.4 Copyright (C) 2012 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "x86_64-unknown-linux-gnu". For bug reporting instructions, please see: <http://www.gnu.org/software/gdb/bugs/>... Reading symbols from /usr/bin/gsi...(no debugging symbols found)...done. (gdb) run Starting program: /usr/bin/gsi Gambit v4.6.3 > (load "xml") "/home/taylor/Repos/gambit-xml/xml.o1" > (define xml (read-xml "./test.xml")) > (length (xml-element-children (xml-document-root xml))) Program received signal SIGSEGV, Segmentation fault. 0x00007ffff702b064 in ___H_xml_2d_element_2d_children (___ps=0xa4ce20) at xml.c:6232 6232 ___IF(___STRUCTUREDIOP(___R1,___R2)) (gdb) bt #0 0x00007ffff702b064 in ___H_xml_2d_element_2d_children (___ps=0xa4ce20) at xml.c:6232 #1 0x00000000004ad51f in ___call () #2 0x00000000004af14f in ___setup () #3 0x00000000004c3ef2 in ___main () #4 0x00000000004b8436 in ___main_char () #5 0x00000000004ac6a9 in main () (gdb) print ___ps->r $1 = {10259873, 11115697, 140737339703681, 11115697, 140737339703681} The problem manifests in code generated by Gambit, but I doubt that's where the problem originates. I don't know enough about the Gambit internals to make it any further on my own. I hope somebody can help guide me in debugging what's wrong, and hopefully point out whether my memory handling in the os_xml.c file is correct or not. There are a few places where I have doubts about whether I should use ___release_scmobj() or not. All of these problems happen fairly regularly on my desktop, which is an Intel Core i7-870 with 8GB of memory running Arch Linux x86_64 kernel 3.2.4 --- but I haven't yet had them on my laptop, which is an Intel Core 2 Duo P8800 with 4GB of memory running the same kernel. Mighty thanks for any assistance! -- Taylor C. Venable http://metasyntax.net/

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PICOBIT and continuation-next?
by Andrew Lentvorski 04 Mar '12

04 Mar '12

So, I was looking at the PICOBIT papers. I noted that the representation of continuations has a "parent" field. Presumably this is to allow something like "continuation-next" from the Better API for First Class Continuations paper. However, I don't see any corresponding virtual machine instructions to manipulate continuations. At that point, I presumed that some form of CPS conversion was going on that was wiping out continuations, so I looked at the 90 Minute Scheme to C compiler stuff. Unfortunately, I don't see how to get "continuation-next" in the context of purely CPS conversion. Anybody have suggestions as to what I am missing and where to look? Obviously, I can look through the full PICOBIT source, but doing so without some landmarks is suboptimal. Thanks, -a

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Re: [gambit-list] Interactive development with Gambit?
by Alexandre Abreu 29 Fév '12

29 Fév '12

> Guillaume Cartier <gcartier(a)jazzscheme.org> wrote:> Wow. Thanks for sharing this video with us and making me discover the > wonderful and inspiring ideas of Bret Victor! he is also the author of this great read: http://worrydream.com/LadderOfAbstraction/ Cheers,Alex

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Re: [gambit-list] [MSLUG] Hacking Health Hackathon
by Alexandre Abreu 28 Fév '12

28 Fév '12

Hi, > Hello. I am looking for people interested in joining a team of hackers for this weekend's "Hacking Health Hackathon" (http://www.hackinghealth.ca/) in Montreal. I am putting together a team with the> objective of using Gambit, and Gambit REPL on the iPhone, to build a prototype health related application. The organizers are expecting over 150 hackers, and there are prizes to win. Did you succeed in getting a team together (I couldn't, too late notice), and if yes, what did you build? Alex

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Hacking Health Hackathon
by Marc Feeley 23 Fév '12

23 Fév '12

Hello. I am looking for people interested in joining a team of hackers for this weekend's "Hacking Health Hackathon" (http://www.hackinghealth.ca/) in Montreal. I am putting together a team with the objective of using Gambit, and Gambit REPL on the iPhone, to build a prototype health related application. The organizers are expecting over 150 hackers, and there are prizes to win. If you are interested, please let me know. Note that it is not absolutely necessary to be physically in Montreal, but it would help to coordinate the team. The hacking starts friday at 6 PM EST, and ends saturday at 5:30 PM EST. Marc Feeley P.S. Sorry for not announcing this sooner...

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ffi double constants
by Álvaro Castro-Castilla 20 Fév '12

20 Fév '12

Hi, I want to use the M_PI constant, which is defined in C as #define M_PI 3.14159265358979323846, with 21 decimals. For the Cairo bindings, the full precision is needed, because drawing a circle is done by drawing an arc 2*M_PI long, and the algorithm only considers it a circle when the 2*pi is passed with the proper precision. What's the way to support this precision for the FFI bindings, so I can pass that value to the affected functions as it is done in C without a special wrapper function for each case? Best regards, Álvaro

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Gambit REPL 6.1
by Marc Feeley 20 Fév '12

20 Fév '12

Version 6.1 of Gambit REPL is now available on the App Store. With this version... - Gambit REPL is now based on the Gambit interpreter v4.6.4 which is slightly faster than the previous version - On iPad, function keys F1,...,F10 enter digits 1,2,...,9,0 by default - A file access issue on iOS 5.0 has been solved Marc

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[ANN] Gambit-C v4.6.4 released
by gambit＠iro.umontreal.ca 20 Fév '12

20 Fév '12

Gambit-C v4.6.4 is now available. Changelog: http://www.iro.umontreal.ca/~gambit/repo/.cgit.cgi/Gambit/log/ The sources and prebuilt distributions can be obtained from the Gambit web site by visiting one of the following links. sources: http://www.iro.umontreal.ca/~gambit/download/gambit/v4.6/source/gambc-v4_6_… (for typical users) http://www.iro.umontreal.ca/~gambit/download/gambit/v4.6/source/gambc-v4_6_… (for developers) prebuilt: http://www.iro.umontreal.ca/~gambit/download/gambit/v4.6/prebuilt/gambc-v4_… http://www.iro.umontreal.ca/~gambit/download/gambit/v4.6/prebuilt/gambc-v4_… http://www.iro.umontreal.ca/~gambit/download/gambit/v4.6/prebuilt/gambc-v4_… http://www.iro.umontreal.ca/~gambit/download/gambit/v4.6/prebuilt/gambc-v4_…

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sxml>>xml layout question.
by Hendrik Boom 17 Fév '12

17 Fév '12

Well I got Blackhole to work though I'll still be posting a few suggestions and questions later. I used it to import and use sxml>>xml successfully. It gives me output like >P5There seems to be nothing to say. <S />After a while he stammers, "Oh, I'm sorry," to fill the silence.P3 P5There seems to be nothing to say. <S/>After a while he stammers, "Oh, I'm sorry," to fill the silence. P3 Is there a technical reason to have the '>' after the newline and the indentation layout instead of before them? Or is this just the way it happened to get coded? (Don't worry about the P5There and such -- my application put them there by mistake and I'll be dealing with them myself) -- hendrik

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Gambit-list Février 2012