Guard against reloading native v8 library

[radhikalism]

The v8wrapper native object only needs to be loaded once; in fact, it must not be reloaded (see magnars/optimus#47).

In Java-land, I understand the loading sequence is usually protected by referencing the library instance as a static property. In Clojure, something effectively similar can be accomplished by conditionally loading the library (only when LIBRARY is unbound), so namespace reloading is safe.

Thoughts?

[pbiggar]

I wonder would a defonce be better here?

[radhikalism]

Hm, defonce wouldn't hurt, but the getInstance method is safe to re-run as it returns a singleton reference once the library has been loaded. The code path to guard is the one with System/loadLibrary or load-library-from-class-path calls.

How about something like this?

(defn get-v8-library []
  (try
    (com.sun.jna.NativeLibrary/getInstance "v8wrapper")
    (catch UnsatisfiedLinkError e
      (try
        (System/loadLibrary "v8wrapper")
        (catch UnsatisfiedLinkError e
          (load-library-from-class-path "libv8" ".clj-v8")
          (load-library-from-class-path "libv8wrapper" "")
          (System/setProperty "jna.library.path" (System/getProperty "java.io.tmpdir"))))
      (com.sun.jna.NativeLibrary/getInstance "v8wrapper"))))

(def LIBRARY (get-v8-library))

No need for a forward declaration or bound? check there.

[karneaud]

+bump was this ever solved? i'm using boot with optimus and get the subject error