Trying to create a binding to racket, but callback of events crashes DrRacket #630
Description
Hi,
I'm trying to create an FFI to webui from racket. I've done some FFI's with callbacks (e.g. libFLAC), which do work without crashing.
But this FFI crashes, when I register a callback.
This is my racket code so far:
(module web-ui-ffi racket/base
(require ffi/unsafe
ffi/unsafe/define
setup/dirs
"../utils/utils.rkt"
)
(provide
)
(define-ffi-definer define-webview2
(ffi-lib "WebView2Loader" '(#f)
#:get-lib-dirs (lambda ()
(cons (build-path ".") (get-lib-search-dirs)))
#:fail (lambda ()
(ffi-lib (get-lib-path "WebView2Loader.dll")))
))
(define-ffi-definer define-web-ui
(ffi-lib "webui" '("2" #f)
#:get-lib-dirs (lambda ()
(cons (build-path ".") (get-lib-search-dirs)))
#:fail (lambda ()
(ffi-lib (get-lib-path "webui-2.dll")))
))
(define _win_id _uint)
(define-cstruct _webui_event_t
[
(window _win_id)
(event_type _uint)
(element _string/utf-8)
(event_number _uint)
(bind_id _uint)
(client_id _uint)
(connection_id _uint)
(cookies _string/utf-8)
])
(define webui_events
(_enum
'(disconnected = 0
connected
mouse-click
navigation
callback
)))
(define webui_browser
(_enum
'(NoBrowser = 0
AnyBrowser = 1
Chrome
Firefox
Edge
Safari
Chromium
Opera
Brave
Vivaldi
Epic
Yandex
ChromiumBased
WebView
)
))
(define webui_config
(_enum
'(show_wait_connection = 0
ui_event_blocking
folder_monitor
multi_client
use_cookies
asynchronous_response
)))
(define _webui_event_callback
;(_cprocedure (list _pointer) _void #:abi 'default #:in-original-place? #t #:atomic? #t))
(_fun _webui_event_t-pointer -> _void))
; void webui_set_config(webui_config option, bool status);
(define-web-ui webui_set_config
(_fun webui_config _bool -> _void))
(define-web-ui webui_new_window
(_fun -> _win_id))
(define-web-ui webui_bind
(_fun _win_id _string/utf-8 _webui_event_callback -> _uint))
(define-web-ui webui_show
(_fun _win_id _string/utf-8 -> _bool))
(define-web-ui webui_show_browser
(_fun _win_id _string/utf-8 webui_browser -> _bool))
(define-web-ui webui_show_wv
(_fun _win_id _string/utf-8 -> _bool))
(define-web-ui webui_wait
(_fun -> _void))
); end of moduleWhen I test it, I'm doing this:
Welcome to DrRacket, version 8.17 [cs].
Language: Determine language from source [custom].
> (webui_set_config 'ui_event_blocking #t)
> (define c 0)
> (define (cb evt)
(inc c))
> (define w (webui_new_window))
> (webui_bind w "" cb)
1
> w
1
> (webui_show w "<html><body><script src=\"webui.js\"></script><h1>Hello World</h1><p><a href=\"#test\">wikipedia</a></p><a name=\"test\">Yes</a></body></html>")This crashes DrRacket with no message at all. Must be something like memory corruption.
As I'm doing very little in cb, there should not be going on much.
The equivalent in C, does work, however, does the callback occur from different threads?
#include "webui/include/webui.h"
#include <processthreadsapi.h>
void cb(webui_event_t *evt)
{
static int c = 0;
c += 1;
printf("Current thread: %p", GetCurrentThread());
printf("%llu\n", evt->event_type);fflush(stdout);
printf("%d\n", c);fflush(stdout);
}
int main(int argc, char *argv[])
{
webui_set_config( ui_event_blocking, true);
size_t win = webui_new_window();
printf("Current thread: %p", GetCurrentThread());
webui_bind(win, "", cb);
printf("%llu\n", win);fflush(stdout);
bool ok = webui_show(win, "<html><body><script src=\"webui.js\"></script><h1>Hello World</h1><p><a href=\"#test\">wikipedia</a></p><a name=\"test\">Yes</a></body></html>");
printf("window shows %d\n", ok);fflush(stdout);
webui_wait();
return 0;
}Output:
03:06:08: Starting C:\devel\build-webui-test-Desktop_Qt_6_5_3_MSVC2019_64bit-Release\webui-test.exe...
Current thread: FFFFFFFFFFFFFFFE1
Current thread: FFFFFFFFFFFFFFFE1
1
window shows 1
Current thread: FFFFFFFFFFFFFFFE0
2
03:06:19: C:\devel\build-webui-test-Desktop_Qt_6_5_3_MSVC2019_64bit-Release\webui-test.exe exited with code 0
In my experience, the racket FFI produces very stable interfacing that works in general like a charm.
My recent integrations with liboa, libFLAC and taglib_c all work without hassle and follow the same approach as the code I posted here.
Any Ideas?