[Chicken-users] Question about gc-roots
I am assigning non-immediate objects to foreign void pointers. To prevent them from moving during garbage collection I turn the pointer into a gc-root. This works like I expect it would work, with one exception: It seems that the finalizers of the objects assigned to the objects inside the gc-root get fired prematurely. I think I'm a little difficult to follow, I'll give an example: # void* ptr; # (define init-root (foreign-lambda* void ((scheme-object obj)) ptr = CHICKEN_new_gc_root(); CHICKEN_gc_root_set(ptr, obj);)) (define root-ref (foreign-lambda* scheme-object () C_return(CHICKEN_gc_root_ref(ptr));)) (define (make-some-string) (set-finalizer! hello (lambda (s) (print s , just got freed. (define-record metadata data) (init-root (make-metadata (make-some-string))) ; prints hello (print (metadata-data (root-ref))) ; will fire finalizer printing hello, just got freed. ; I didn't expect this because there is still a refrence to the object inside the root. (gc #t) ; prints hello, object seems to still be around. (print (metadata-data (root-ref))) --- Maybe I don't understand gc-roots and use them wrongly or for the wrong purpose. If so, would somebody kindly explain. Thanks in advance, Pluijzer ___ Chicken-users mailing list Chicken-users@nongnu.org https://lists.nongnu.org/mailman/listinfo/chicken-users
[Chicken-users] mutate-procedure documentation
Hello everybody, I was reading the documentation for mutate-procedure in the lolevel unit ( http://wiki.call-cc.org/man/3/Unit%20lolevel#mutate-procedure) but got confused by the example given. Should 'new' not be called 'old', or do I misunderstand? Thx, Pluijzer ___ Chicken-users mailing list Chicken-users@nongnu.org https://lists.nongnu.org/mailman/listinfo/chicken-users
[Chicken-users] pass by value and callbacks
Hello chickeners,
I am trying to wrap a function that accepts a function pointer with an
argument to a struct passed by value.
I don't know how to do this (and fear it is not possible) but maybe
somebody else has a solution.
A little example of what I mean:
#
typedef struct { int x, y; } Point;
typedef void (*SomeCallbackFuncType)(Point point);
void someFunc(SomeCallbackFuncType callback)
{
Point p = {1, 1};
callback(p);
}
#
(define-external (callbackFunction (??? point))
void
(print Hello from callback!))
((foreign-lambda void someFunc c-pointer) #$callbackFunction)
I don't actually need the the value of the object in my callback.
Maybe that helps.
Thank you in advance,
Pluijzer
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Re: [Chicken-users] #invalid forwarded object using FFI callback
Hello Alyn,
Thank you for the extra info.
For my sitituation, which is a little different to yours I think, a work
aroundt he issue at the moment by wrapping the scheme-object around a
structure that contains a root node.
I do not know how appropriate or convinient this is to your situation.
...:
typedef struct
{
void* node;
} Object;
(define make-object
(foreign-lambda* (c-pointer Object) ((scheme-object value))
Object* object = malloc(sizeof(Object));
object-node = CHICKEN_new_gc_root();
CHICKEN_gc_root_set(object-node, value);
C_return( object );))
(define read-object
(foreign-lambda* scheme-object (((c-pointer Object) object))
C_return( CHICKEN_gc_root_ref(object-node) );))
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Re: [Chicken-users] #invalid forwarded object using FFI callback
Hello Alyn,
Did you find a solution to this problem? I seem to suffer a similar problem.
thanks,
Pluijzer
2013/12/8 .alyn.post. alyn.p...@lodockikumazvati.org
Greetings,
I'm encountering the following error message inside a callback using
Chicken's FFI interface:
Error: (cdr) bad argument type: #invalid forwarded object
Call history:
pwent.scm:100: loop
pwent.scm:56: ##sys#gc
pwent.scm:56: g42
pwent.scm:24: make-string
pwent.scm:24: make-string
pwent.scm:24: make-string
pwent.scm:24: make-string
pwent.scm:50: clist-append!
pwent.scm:100: loop
pwent.scm:56: ##sys#gc
pwent.scm:56: g42
pwent.scm:24: make-string
pwent.scm:24: make-string
pwent.scm:24: make-string
pwent.scm:24: make-string
pwent.scm:50: clist-append! --
What seems to be happening is that I'm running out of (stack?) memory
while inside/around a C thunk. I cannot seem to avoid this message by
modifying the nursery, either from csc -nursery or from -:s.
I have only a topical grasp of Chicken's FFI, so I suspect I'm simply
doing something ill-advised, though I would appreciate advice on how
to approach my problem:
I'm trying to read /etc/passwd using getpwent(3) and store each
record returned in a scheme list. (My particular /etc/passwd file
contains 100 elements, the above error happens near the end of the
call.) I'm marshalling records using two callbacks: one to create the
memory for string data, and one to append each record to the list.
May I have feedback on the pattern I'm using here to marshall data?
And a suggestion on how to avoid invalid forward objects while
reading large but disjoint data from C? I'm at a loss as to why
exactly I'm getting the above message, and it well could be incorrect
code on my part. Do my multiple calls to _make_string from C,
below, cause the GC to loose track of my string pointers? Something
else?
++ csc -o pwent pwent.scm ./pwent
(use extras)
; a circular list (where we track the
; head and tail) with a dummy head.
;
(define (make-clist)
(let ((head (list #f)))
(cons head head)))
; O(1) list append.
;
(define (clist-append! d v)
(let ((l (list v)))
(set-cdr! (cdr d) l)
(set-cdr! d l)))
; return proper list
;
(define (clist-list d)
(cdr (car d)))
; allocate a scheme string available in C.
;
(define-external
(_make_string (size_t n)) scheme-object
(make-string n))
(declare (foreign-declare #EOF
#include sys/types.h
#include string.h
#include pwd.h
EOF
))
(define (getpwent)
; append! each pwent record to our record list.
;
(define-external
(_getpwent_cb (scheme-object clist)
(scheme-object user)
(scheme-object passwd)
(scheme-object uid)
(scheme-object gid)
(scheme-object home)
(scheme-object shell)) void
(let ((pwent `((user . ,user)
(passwd . ,passwd)
(uid. ,uid)
(gid. ,gid)
(home . ,home)
(shell . ,shell
(clist-append! clist pwent)))
; retrieve the next pwent record and marshall it
; in to scheme.
;
(define _getpwent
(foreign-safe-lambda* bool ((scheme-object clist)) #EOF
struct passwd *pw;
C_word shell, dir, passwd, name;
size_t n;
pw = getpwent();
if(!pw) {
endpwent();
C_return(0);
}
n = strlen(pw-pw_name);
name = _make_string(n);
C_memcpy(C_c_string(name), pw-pw_name, n);
n = strlen(pw-pw_passwd);
passwd = _make_string(n);
C_memcpy(C_c_string(passwd), pw-pw_passwd, n);
n = strlen(pw-pw_dir);
dir = _make_string(n);
C_memcpy(C_c_string(dir), pw-pw_dir, n);
n = strlen(pw-pw_shell);
shell = _make_string(n);
C_memcpy(C_c_string(shell), pw-pw_shell, n);
_getpwent_cb(clist,
name,
passwd,
C_fix(pw-pw_uid),
C_fix(pw-pw_gid),
dir,
shell);
C_return(1);
EOF
))
; loop ever every entry in pwent and append
; it to our list.
;
(let loop ((clist (make-clist)))
(if (_getpwent clist)
(loop clist)
(clist-list clist
(pretty-print (getpwent))
--
Thank you,
-a
$ csc -version
(c) 2008-2013, The Chicken Team
(c) 2000-2007, Felix L. Winkelmann
Version 4.8.0.5 (stability/4.8.0) (rev 5bd53ac)
openbsd-unix-gnu-x86 [ manyargs dload ptables ]
compiled 2013-10-03 on aeryn.xorinia.dim (Darwin)
--
my personal website: http://c0redump.org/
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[Chicken-users] assigning scheme object to foreign pointer
Hello everybody. I am using a C-library that lets you assign user data to objects via a void pointer. I would like to assign a scheme object to this pointer, but as I understand I cannot use 'object-pointer' for this, as the garbage collector might move the object. Is there another way to accomplish this, maybe by telling the gc not to move the object? thank you very much in advance, Pluijzer ___ Chicken-users mailing list Chicken-users@nongnu.org https://lists.nongnu.org/mailman/listinfo/chicken-users
Re: [Chicken-users] assigning scheme object to foreign pointer
Hello Evan and Thomas, Thank you for your suggestions, I decided to go for `CHICKEN_new_gc_root` and it works like I hoped. I was the lookup-table before but found it to be too unwieldy in my project. Thanks again, Pluijzer On Mon, 16 Dec 2013 13:28:27 +1300 Evan Hanson ev...@foldling.org wrote: Hi Pluijzer, On 16/12/13 12:59, pluijzer wrote: I am using a C-library that lets you assign user data to objects via a void pointer. I would like to assign a scheme object to this pointer, but as I understand I cannot use 'object-pointer' for this, as the garbage collector might move the object. There are a couple of ways to do this. One is to manually move the object into static memory, via `object-evict` (http://api.call-cc.org/doc/lolevel#def:object-evict). This is nice and easy, but might not work as expected for all data types. Another is to create a new GC root for the object, via `CHICKEN_new_gc_root` and its associated procedures (http://api.call-cc.org/doc/foreign/embedding#sec:CHICKEN_new_gc_root). You might also sidestep the issue entirely by keeping your objects in a Scheme-side lookup table and only storing immediate values in the pointer that you can then use to retrieve the objects as needed. Other folks may chime in with more ideas, but I hope these help some. Cheers, Evan ___ Chicken-users mailing list Chicken-users@nongnu.org https://lists.nongnu.org/mailman/listinfo/chicken-users -- pluijzer pluij...@gmail.com ___ Chicken-users mailing list Chicken-users@nongnu.org https://lists.nongnu.org/mailman/listinfo/chicken-users
[Chicken-users] Problem with creating extensions
Hello everybody, I fail to get extensions that I have created and installed via 'chicken-install' to load. For example (using the example from the documentation): */tmp/hello $ cat hello.scm* (define (hello name) (print Hello, name !)) */tmp/hello $ cat hello.setup* (compile -s hello.scm) (install-extension 'hello hello.so) */tmp/hello $ cat hello.meta* ((author Me) (synopsis A cool hello-world library) (license GPLv3) (files hello.scm hello.setup)) */tmp/hello $ chicken-install * retrieving ... checking platform for `hello' ... checking dependencies for `hello' ... install order: (hello) installing hello: ... changing current directory to . /usr/bin/csi -bnq -setup-mode -e (require-library setup-api) -e (import setup-api) -e (setup-error-handling) -e (extension-name-and-version '(\hello\ \\)) hello.setup /usr/bin/csc -feature compiling-extension -setup-mode-s hello.scm cp -r hello.so /var/lib/chicken/6/hello.so chmod a+r /var/lib/chicken/6/hello.so chmod a+r /var/lib/chicken/6/hello.setup-info */tmp/hello $ csi -p '(use hello)'* Error: (import) during expansion of (import ...) - cannot import from undefined module: hello Call history: syntax (use hello) syntax (##core#require-extension (hello) #t) syntax (##core#begin (##core#begin (##core#begin (##sys#require (quote hello))) (import hello)) (##core#und.. syntax (##core#begin (##core#begin (##sys#require (quote hello))) (import hello)) syntax (##core#begin (##sys#require (quote hello))) syntax (##sys#require (quote hello)) syntax (quote hello) syntax (##core#quote hello) syntax (import hello)-- Some extra information: */tmp/hello $ csi -p '(repository-path)'* /var/lib//chicken/6 */tmp/hello $ ls /var/lib/chicken/6/hello.** /var/lib/chicken/6/hello.setup-info /var/lib/chicken/6/hello.so */tmp/hello $ csi -version* CHICKEN (c)2008-2011 The Chicken Team (c)2000-2007 Felix L. Winkelmann Version 4.7.0 linux-unix-gnu-x86 [ manyargs dload ptables ] compiled 2011-09-06 on murphy (Linux) --- I am using Debain Wheezy Am I making a silly mistake, have I forgotten something? Thank you in advance, Pluijzer ___ Chicken-users mailing list Chicken-users@nongnu.org https://lists.nongnu.org/mailman/listinfo/chicken-users
[Chicken-users] Chicken C interface
Hello everybody,
I was planning to use Chicken Scheme in a fashion more similar to Guile and
Lua. i.e. passing Scheme Data Objects from Chicken to C and back using the
C interface.
I am a little confused though as how to have a C function return a Scheme
List that is seen by the garbage collector.
For example, is the code below correct, will the list be seen by the
garbage collector? And if not, is there correct way to do this.
#
C_word give_12()
{
C_word *mem = C_alloc(C_SIZEOF_LIST(2));
C_word list = C_list(mem, 2, C_fix(1), C_fix(2));
return list;
}
#
(print ((foreign-lambda scheme-object give_12)))
Also there doesn't seem to be a C_listp predicate. Is this a concious
omission?
thank you in advance,
Richard
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[Chicken-users] Passing floats to and from foreign functions
Hello everybody,
I'm having trouble passing floating point numbers to and from foreign
functions.
This is what I'm doing:
-- test.scm --
(require-extension easyffi)
(print ((foreign-lambda float testGet)))
((foreign-lambda void testSet float) 4.0)
(print ((foreign-lambda float testGet)))
-- wrapper.c --
float a = 5.0;
void testSet(float value) { a = value; }
float testGet(void) { return a; }
What I get is this:
csc -X easyffi wrapper.c test.scm
./test
-1080529876.0
-1080533140.0
But I expected the output to be:
4.0
5.0
I'm I doing something wrong/forgetting something?
When I use integers instead of floats I do get the desired result.
Thank you in advance,
Righard
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