Add spec for Truffle::POSIX when returning unsigned values

Author: eregon

.gitignore

@@ -44,6 +44,9 @@ src/main/c/truffleposix/truffleposix.o
 src/main/c/truffleposix/libtruffleposix.so
 src/main/c/truffleposix/libtruffleposix.dylib
 
+spec/truffle/fixtures/libtestnfi.so
+spec/truffle/fixtures/libtestnfi.dylib
+
 test/truffle/cexts/**/Makefile
 test/truffle/cexts/**/*.bc
 test/truffle/cexts/**/*.su

spec/truffle.mspec

@@ -188,6 +188,9 @@ if i = ARGV.index('slow') and ARGV[i-1] == '--excl-tag' and MSpecScript.child_pr
   ]
 
   module Kernel
+    alias_method :mspec_old_system, :system
+    private :mspec_old_system
+
     alias_method :"mspec_old_`", :`
     private :"mspec_old_`"
   end

spec/truffle/fixtures/libtestnfi.c

@@ -0,0 +1,9 @@
+#include <limits.h>
+
+unsigned short max_ushort(void) {
+  return USHRT_MAX;
+}
+
+unsigned int max_uint(void) {
+  return UINT_MAX;
+}

spec/truffle/posix_spec.rb

@@ -0,0 +1,36 @@
+# Copyright (c) 2019 Oracle and/or its affiliates. All rights reserved. This
+# code is released under a tri EPL/GPL/LGPL license. You can use it,
+# redistribute it and/or modify it under the terms of the:
+#
+# Eclipse Public License version 1.0, or
+# GNU General Public License version 2, or
+# GNU Lesser General Public License version 2.1.
+
+require_relative '../ruby/spec_helper'
+
+describe "Trffle::POSIX returns the correct value for an identity function returning" do
+  before :all do
+    src = fixture __FILE__, "libtestnfi.c"
+    lib = src[0...-1] + RbConfig::CONFIG['NATIVE_DLEXT']
+    unless system "cc", "-shared", "-o", lib, src
+      abort "Could not compile libtestnfi"
+    end
+
+    lazy_library = Truffle::POSIX::LazyLibrary.new do
+      Polyglot.eval('nfi', "load '#{lib}'")
+    end
+
+    @libtestnfi = Module.new do
+      Truffle::POSIX.attach_function :max_ushort, [], :ushort, lazy_library, false, :max_ushort, self
+      Truffle::POSIX.attach_function :max_uint, [], :uint, lazy_library, false, :max_uint, self
+    end
+  end
+
+  it "the maximum unsigned short" do
+    @libtestnfi.max_ushort.should == 65535
+  end
+
+  it "the maximum unsigned int" do
+    @libtestnfi.max_uint.should == 4294967295
+  end
+end