Add spec and fix exception for Fiddle::Handle.new with a missing library

* Fixes #2714

Author: eregon

CHANGELOG.md

@@ -33,6 +33,7 @@ Compatibility:
 * Implement `rb_eval_cmd_kw` to support the `tk` gem (#2556, @aardvark179).
 * Fix `rb_class2name` to call `inspect` on anonymous classes like in CRuby (#2701, @aardvark179).
 * Implement `rb_ivar_foreach` to iterate over instance and class variables like in CRuby (#2701, @aardvark179).
+* Fix exception for `Fiddle::Handle.new` with a missing library (#2714, @eregon).
 
 Performance:
 

lib/truffle/truffle/fiddle_backend.rb

@@ -253,15 +253,16 @@ def self.[](*args)
     RTLD_GLOBAL  = Truffle::Config['platform.dlopen.RTLD_GLOBAL']
 
     def initialize(library = nil, flags = RTLD_LAZY | RTLD_GLOBAL)
-      raise DLError, 'unsupported dlopen flags' if flags != RTLD_LAZY | RTLD_GLOBAL
+      raise DLError, 'unsupported dlopen flags' if flags != (RTLD_LAZY | RTLD_GLOBAL)
+
       if library == Truffle::FiddleBackend::RTLD_NEXT
         @handle = :rtld_next
       else
         library = nil if library == Truffle::FiddleBackend::RTLD_DEFAULT
         begin
           @handle = Primitive.interop_eval_nfi(library ? "load '#{library}'" : 'default')
-        rescue RuntimeError
-          raise DLError, "#{library}: cannot open shared object file: No such file or directory"
+        rescue Polyglot::ForeignException => e
+          raise DLError, "#{e.message}"
         end
       end
     end

spec/ruby/library/fiddle/handle/initialize_spec.rb

@@ -0,0 +1,10 @@
+require_relative '../../../spec_helper'
+require 'fiddle'
+
+describe "Fiddle::Handle#initialize" do
+  it "raises Fiddle::DLError if the library cannot be found" do
+    -> {
+      Fiddle::Handle.new("doesnotexist.doesnotexist")
+    }.should raise_error(Fiddle::DLError)
+  end
+end