add more warnings (#104)

* add more warnings

* move warning to module load.

Author: aviks

src/JavaCall.jl

@@ -29,6 +29,15 @@ include("convert.jl")
 include("reflect.jl")
 
 function __init__()
+    if VERSION ≥ v"1.1-" && VERSION < v"1.3-"
+        @warn("JavaCall does not work correctly on Julia v$VERSION. \n " *
+                "Either use Julia v1.0.x, or v1.3.0 or higher.\n"*
+                "For 1.3 onwards, please also set the environment variable `JULIA_COPY_STACKS` to be `1` or `yes`")
+    end
+    if VERSION ≥ v"1.3-" && get(ENV, "JULIA_COPY_STACKS", "") ∉ ("1", "yes")
+        @warn("JavaCall needs the environment variable `JULIA_COPY_STACKS` to be `1` or `yes`. "*
+              "Calling the JVM may result in undefined behavior.")
+    end
 	findjvm()
 	global create = Libdl.dlsym(libjvm, :JNI_CreateJavaVM)
 end

src/jvm.jl

@@ -152,10 +152,6 @@ end
 addOpts(s::String) = isloaded() ? @warn("JVM already initialised. This call has no effect") : push!(opts, s)
 
 function init()
-    if VERSION ≥ v"1.3" && get(ENV, "JULIA_COPY_STACKS", "") ∉ ("1", "yes")
-        @warn("JavaCall needs the environment variable `JULIA_COPY_STACKS` to be `1` or `yes`. "*
-              "Calling the JVM may result in undefined behavior.")
-    end
     if isempty(cp)
         init(opts)
     else