Embedding an nREPL server in lwjgl example results in crash on connection attempt

[jdhollis]

I’m attempting to spin up an nREPL server from within my app (which I’m basing off the lwjgl example). The app starts up fine, but it crashes as soon as I try to connect to the server (using Cursive’s nREPL connection type):

# Problematic frame:
# C  [libskija.dylib+0x4502d]  SkCanvas::internalDrawPaint(SkPaint const&)+0xcd

My goal is to enable interactive development for me while running the app on the main thread and to eventually include the REPL as a feature of the app. (This was an attempt to follow @tonsky's advice in #56.)

The only change I’ve made to the example so far is a call to start the REPL server just before the main loop:

(repl-server/start!)
(loop []
  (when (not (GLFW/glfwWindowShouldClose window))
    (draw canvas)
    (.flush context)
    (GLFW/glfwSwapBuffers window)
    (GLFW/glfwPollEvents)
    (recur)))

My start! function is fairly simple. I also tried wrapping everything in a fresh thread to no avail:

(defn start!
  []
  (if (nil? @thread)
    (do
      (reset! thread (Thread. ^Runnable
                              (fn [] (if (nil? @server)
                                       (reset! server (start-server :port 12345))))))
      (.start @thread))))

I’m currently at a loss as to what else to try.

I've attached the crash log. Any suggestions?

hs_err_pid99984.log

[jdhollis]

I tried the same approach using the clojure.core.server/start-server instead of nREPL, and when I tried to connect, it crapped out with a similar message:

# Problematic frame:
# C  [libskija.dylib+0x4502d]  SkCanvas::internalDrawPaint(SkPaint const&)+0xcd

[tonsky]

Very strange. I can reproduce it, and it seems to be related to Skija specifically, if I remove it and leave LWJGL only, it doesn’t crash. I’ll look into it too, thanks for reporting!

[tonsky]

I think the problem is that connecting via nREPL triggers GC which collects BackendRenderTarget and Surface. Adding (println context target surface) after the infinite loop solves the problem. I’ll fix Skija tomorrow so that Canvas holds a reference to the Surface so that it won’t be collected before Canvas is.

[tonsky]

Should work fine in 0.6.14. Let me know if it doesn’t

[jdhollis]

Finally getting back into this. 0.6.18 works fine for me. Thanks!