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Difficulties linking against a C++ library
by John Thompson 25 Fév '09

25 Fév '09

Hi, I'm trying to get a toy, loadable C++ library compiled. My setup is as follows: foo.scm: (define bar (c-lambda (char-string) int "cpp_bar")) foo.cpp: int cpp_bar(char* text) { return 0; } foo.h: int cpp_bar(char* text); I'm using the latest tarball of gambit, compiled with --enable-cplusplus. I compile foo.scm to C++ via: gsc -link -flat foo.scm ==> foo.c and foo_.c Then I want to compile these into object files and I run into trouble. g++ -fPIC -c foo.c outputs the following: oo.c: In function ‘int ___H__20_foo_23_0(___processor_state_struct*)’: foo.c:119: error: ‘cpp_bar’ was not declared in this scope foo.c: At global scope: foo.c:156: warning: deprecated conversion from string constant to ‘char*’ Whereas gcc compiles it fine. It must be a name-mangling issue, but it seems peculiar to me, given that I compiled gsc using g++. Moreover, I can compile if I add extern "C" {int cpp_bar(char*);} to foo.c. I picked this up from reading about someone who had similar problems a few years ago: http://osdir.com/ml/lisp.scheme.gambit/2005-02/msg00037.html I then compile and link like: g++ -fPIC -c -D___DYNAMIC foo_.c foo.c g++ -fPIC -c -D___DYNAMIC foo.cpp -o cppfoo.o ld -G -o foo.o1 /usr/lib/libstdc++.so.6.0.9 /usr/lib/gcc/i486-linux-gnu/4.2/crtbegin.o cppfoo.o foo_.o foo.o Unfortunately, this leads me here: *** WARNING -- Could not find C function: "____20_foo_2e_o1" *** ERROR IN ##main -- .../foo.o1: undefined symbol: cpp_bar (load "foo.o1") Can anyone offer me any pointers on how to proceed? -John

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sllgen for gambit?
by Pavel Dudrenov 25 Fév '09

25 Fév '09

Does anyone know if there is anything portable written, or that works on gambit? The only thing I found works is plt scheme. Thanks, Pavel

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Getting rid of compiler warnings.
by lowly coder 24 Fév '09

24 Fév '09

Hi! There are two compiler warnings I want to get rid of. Please enlighten me. (1) is from gcc, (2) is from gsc. (1) this one deals with const char * vs char * if I try to do (pointer char), I get the following error: ~/test$ cat error1.scm; echo '-----'; gsc error1.scm; echo '-----'; gsc -link error1; gsi -e '(load "error1")' (c-declare #<<c-declare-end #include <stdio.h> void foo(const char* str) { fprintf(stderr, "printing: %s\n", str); } c-declare-end ) (define foo (c-lambda ((pointer char)) void "foo")) (foo "hello world") ----- error1.c:45: warning: deprecated conversion from string constant to ?char*? error1.c:51: warning: deprecated conversion from string constant to ?char*? error1.c:51: warning: deprecated conversion from string constant to ?char*? error1.c:51: warning: deprecated conversion from string constant to ?char*? error1.c:191: warning: deprecated conversion from string constant to ?char*? ----- *** ERROR IN ##load -- (Argument 1) Can't convert to C pointer (foo "hello world") now, if I use char-string instead, I get an annoying error while compiling with gcc: ~/test$ cat error2.scm; echo '-----'; gsc error2.scm; echo '-----'; gsc -link error2; gsi -e '(load "error2")' (c-declare #<<c-declare-end #include <stdio.h> void foo(const char* str) { fprintf(stderr, "printing: %s\n", str); } c-declare-end ) (define foo (c-lambda (char-string) void "foo")) (foo "hello world") ----- error2.c:42: warning: deprecated conversion from string constant to ?char*? error2.c:42: warning: deprecated conversion from string constant to ?char*? error2.c:42: warning: deprecated conversion from string constant to ?char*? error2.c:174: warning: deprecated conversion from string constant to ?char*? ----- printing: hello world I don't want to tell gcc to ignore this error. I want to get gambit to generate correct code. How do I do that? (2) This is shown right in section 3.4.2 of the gambit reference manual: $ gsc -link -flat -o foo.o1.c m2 m3 m2: m3: *** WARNING -- "cons" is not defined, *** referenced in: ("m2.c") *** WARNING -- "map" is not defined, *** referenced in: ("m3.c") *** WARNING -- "newline" is not defined, *** referenced in: ("m3.c") *** WARNING -- "write" is not defined, *** referenced in: ("m3.c") Is there something I can put in m2.scm / m3.scm like "don't worry about cons / map / newline / write" ? ; File: "m2.scm" (c-declare "extern int power_of_2 ();") (define pow2 (c-lambda (int) int "power_of_2")) (define (twice x) (cons x x)) ; File: "m3.scm" (write (map twice (map pow2 '(1 2 3 4)))) (newline) aside: I realize these are just small warnings. However, I'm doing alot of C-FFi library wrapping, and it's getting to be more than one screenful of warnings. This is bad as (1) I like things to be clean and (2) it makes it hard to view actual errors since there are so many silly warnings. Thanks!

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how does make-default-entry-hook work?
by lowly coder 24 Fév '09

24 Fév '09

In lib/_repl.scm: (define-prim (##make-default-entry-hook) (let ((settings (##vector #f #f))) (lambda (proc args execute) (if (##vector-ref settings 0) (##step-on)) ;; turn on single-stepping (if (##vector-ref settings 1) (##trace-generate (##make-call-form proc (##argument-list-remove-absent! args '()) ##max-fixnum) execute #f) (execute))))) how does this code work at all? isn't settings #f #f, which would mean the first if does nothing, and the first part of the second if also does nothing? is there some funky dynamic-wind / dynamic scope going on here?

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way interpreted code is stored / unraveling trace
by lowly coder 23 Fév '09

23 Fév '09

Join me for episode 201 of "gambit detective stories", today, we're going to try to solve the case of "how the f*ck does trace insert hooks" So looking at lib/_repl.scm , we see in ##trace that we have: (##interp-procedure-entry-hook-set! proc new-hook) which looks something like: (define-prim (##interp-procedure-entry-hook-set! proc hook) (let (($code (##interp-procedure-code proc))) (macro-code-set! $code (##fixnum.- (macro-code-length $code) 2) hook))) this "2" here looks like a magic constant, let's ignore it for now; looking for macro-code-set! in lib/_eval#.scm , we see: (##define-macro (macro-code-set! c n x) `(##vector-set! ,c (##fixnum.+ ,n 5) ,x)) now, this 5 here is anothe rmagical constant -- but this looks interesting; for the interpreter, does gambit basically store the procedure in a vector ... and for inserting traces, we just _DYNAMICALLY REWRITE THE CODE_ to insert stuff before & after? If so, this is really really cool. Any insights / clarifications / tips / deatils appreciated. Thanks!

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limiting trace
by lowly coder 22 Fév '09

22 Fév '09

Code: ~/code/irc$ cat trace.scm (define (foo x) x) (define (bar) (foo 0)) (define (test) (foo 1) (bar)) (trace foo) (test) ~/code/irc$ gsi trace.scm | > (foo 1) | 1 | > (foo 0) | 0 Problem: Can I control trace where I can say "trace foo, but not when it's called by bar". I.e. rather than just saying "trace this function", I would like to be able to say: (trace foo predicate) where predicate is a function that takes as input the "stack" frame, and as output creates a #t / #f, which decides whether this particular trace should be printed On a side note -- all the cool debugging functions in Gambit -- is this part of the 100K LOC scheme or 50K LOC hand written C? (hoping it's the former)

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Gambit Git on Windows
by Guillaume Cartier 20 Fév '09

20 Fév '09

I just installed and built the latest Gambit from sources on Windows and when I do git status I get the following entries ._relpath bin/gambc-doc.bat bin/gambc-doc.bat.unix bin/gambc-doc.bat.windows relpath These probably need to be added to the .gitignore? Guillaume Cartier

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Speed improvement of lib/digest.scm
by Marc Feeley 20 Fév '09

20 Fév '09

The file lib/digest.scm, which computes digests (CRC32, MD5, SHA-1, etc), has been optimized. The new version is on the repository. Essentially it now does all computations with fixnums (the old version did many operations on bignums and the fixnum operations were not inlined). Digest computation of a 1MB file is over 100 times faster than the previous version! Marc

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user-defined ports / input-port-byte-position on u8vector ports
by Darren Baker 19 Fév '09

19 Fév '09

Hi all, I've been implementing a virtual file system in Gambit; the idea is that I can open a file for input and it could be transparently sourced from a .zip file, or the local filesystem, http connection, etc., and a suitable newly-created port would be returned that the caller can do the usual character and byte I/O with. So for example if a request resolves to a local file, then open-input-port is used, if it's a compressed file, then a different port would be used that handles the decompression. Two issues: 1) In the case of reading from a .zip, Gambit obviously doesn't have a port for this, so it seemed to me that creating a new custom port type would be ideal. Is there an official / easy way to do this? (A simplified low-level user port type would be great, in the style used by many C libraries, ie user provides read-bytes, write-bytes, seek and tell functions.) 2) For now I've implemented .zip functionality by extracting the required file to a u8vector, then creating a u8vector-input-port on that, and returning it. Good idea... except that I find out the hard way that input-port-byte-position doesn't work on u8vector ports. This seems to indicate that I can't do random access binary I/O on them using the port functions...? I realise it's not a "device port" but it seems a logical thing to want to do in general. Btw, reading the list archives from 2006 there was a discussion on the behaviour of input-port-byte-position returning the *buffered* position not the read-u8 cursor position. FWIW, my vote is for the read-u8 position, the current behaviour totally caught me out and isn't particularly usable. :) Thanks, Darren

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fast binary serialization
by lowly coder 19 Fév '09

19 Fév '09

hey, I have some non-recursive scheme data structures that I want to store/load between runs; I'm currently storing them with "pp" and loading them with "(read-all (open-input-file ...))" on my particular data source, with my macbook pro, i'm getting 7MB / seconds for parsing the s-exps back in; I'm wondering if there is a generic gambit way to store/load in binary, non-human readable format for something faster (btw, i'm NOT IO bound since for timing, I do the reading multiple times, so the file is probably already in RAM / some file cache) thanks!

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