JULIA_COPY_STACKS should not be recommended or asserted on Windows

Author: Mark Kittisopikul

src/JavaCall.jl

@@ -36,7 +36,7 @@ function __init__()
                 "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-" && ! JULIA_COPY_STACKS
+    if VERSION ≥ v"1.3-" && ! Sys.iswindows() && ! JULIA_COPY_STACKS
         @warn("JavaCall needs the environment variable `JULIA_COPY_STACKS` to be `1` or `yes`.\n"*
               "Calling the JVM may result in undefined behavior.")
     end

src/jvm.jl

@@ -168,7 +168,11 @@ const ROOT_TASK_ERROR = JavaCallError(
 
 # JavaCall must run on the root Task or JULIA_COPY_STACKS is enabled
 isroottask() = JULIA_COPY_STACKS || Base.roottask === Base.current_task()
-assertroottask() = isroottask() ? nothing : throw(ROOT_TASK_ERROR)
+@static if Sys.iswindows()
+    assertroottask() = nothing
+else
+    assertroottask() = isroottask() ? nothing : throw(ROOT_TASK_ERROR)
+end
 
 isloaded() = isdefined(JavaCall, :jnifunc) && isdefined(JavaCall, :penv) && penv != C_NULL