jruby · Jan 4, 2016 · Jan 4, 2016 · Jan 4, 2016 · Jan 4, 2016 · Jan 4, 2016
diff --git a/spec/truffle/tags/language/predefined_tags.txt b/spec/truffle/tags/language/predefined_tags.txt
@@ -3,6 +3,6 @@ slow:The predefined global constant STDIN retains the encoding set by #set_encod
 slow:The predefined global constant STDIN has the encodings set by #set_encoding
 slow:The predefined global constant STDOUT has the encodings set by #set_encoding
 slow:The predefined global constant ARGV contains Strings encoded in locale Encoding
+linux:Global variable $0 actually sets the program name
 fails:Predefined global $_ is set to the last line read by e.g. StringIO#gets
 fails:Predefined global $_ is set at the method-scoped level rather than block-scoped
-fails:Global variable $0 actually sets the program name
diff --git a/spec/truffle/truffle.mspec b/spec/truffle/truffle.mspec
@@ -1,9 +1,15 @@
+require 'rbconfig'
+
 class MSpecScript
 
   def self.windows?
     ENV.key?('WINDIR') || ENV.key?('windir')
   end
 
+  def self.linux?
+    RbConfig::CONFIG['host_os'] == 'linux'
+  end
+
   set :target, File.expand_path("../../../bin/jruby#{windows? ? '.bat' : ''}", __FILE__)
 
   if ARGV[-2..-1] != %w[-t ruby] # No flags for MRI
@@ -61,6 +67,11 @@ class MSpecScript
     set :xtags, (get(:xtags) || []) + ['windows']
   end
 
+  if linux?
+    # exclude specs tagged with 'linux'
+    set :xtags, (get(:xtags) || []) + ['linux']
+  end
+
   # Enable features
   MSpec.enable_feature :fiber
   MSpec.enable_feature :fiber_library

diff --git a/truffle/src/main/java/org/jruby/truffle/nodes/globals/WriteProgramNameNode.java b/truffle/src/main/java/org/jruby/truffle/nodes/globals/WriteProgramNameNode.java
@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2016 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
+ * GNU General Public License version 2
+ * GNU Lesser General Public License version 2.1
+ */
+package org.jruby.truffle.nodes.globals;
+
+import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
+import com.oracle.truffle.api.dsl.NodeChild;
+import com.oracle.truffle.api.dsl.Specialization;
+import com.oracle.truffle.api.object.DynamicObject;
+import com.oracle.truffle.api.source.SourceSection;
+import jnr.ffi.Pointer;
+import org.jruby.truffle.nodes.RubyNode;
+import org.jruby.truffle.runtime.RubyContext;
+
+import java.nio.charset.StandardCharsets;
+
+@NodeChild(value = "value", type = RubyNode.class)
+public abstract class WriteProgramNameNode extends RubyNode {
+
+    /*
+     * When we call _NSGetArgv we seem to always get a string that looks like what we'd expect from running ps, but
+     * with a null character inserted early. I don't know where this comes from, but it means I don't know how to get
+     * the length of space available for writing in the new program name. We therefore about 40 characters, which is
+     * a number without any foundation, but it at leaast allows the specs to pass, the functionality to be useful,
+     * and probably avoid crashing anyone's programs. I can't pretend this is great engineering.
+     */
+    private static final int MAX_PROGRAM_NAME_LENGTH = 40;
+
+    public WriteProgramNameNode(RubyContext context, SourceSection sourceSection) {
+        super(context, sourceSection);
+    }
+
+    @TruffleBoundary
+    @Specialization(guards = "isRubyString(value)")
+    protected Object writeProgramName(DynamicObject value) {
+        if (getContext().getCrtExterns() != null) {
+            final String valueString = value.toString();
+            final Pointer programNameAddress = getContext().getCrtExterns()._NSGetArgv().getPointer(0).getPointer(0);
+            programNameAddress.putString(0, valueString, MAX_PROGRAM_NAME_LENGTH, StandardCharsets.UTF_8);
+        }
+
+        return value;
+    }
+
+}
diff --git a/truffle/src/main/java/org/jruby/truffle/runtime/RubyContext.java b/truffle/src/main/java/org/jruby/truffle/runtime/RubyContext.java
@@ -53,6 +53,7 @@
 import org.jruby.truffle.runtime.loader.SourceLoader;
 import org.jruby.truffle.runtime.methods.InternalMethod;
 import org.jruby.truffle.runtime.object.ObjectIDOperations;
+import org.jruby.truffle.runtime.platform.CrtExterns;
 import org.jruby.truffle.runtime.rubinius.RubiniusConfiguration;
 import org.jruby.truffle.runtime.sockets.NativeSockets;
 import org.jruby.truffle.runtime.subsystems.*;
@@ -62,6 +63,7 @@
 import org.jruby.util.IdUtil;
 
 import java.io.File;
+import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.PrintStream;
 import java.math.BigInteger;
@@ -86,6 +88,7 @@ public class RubyContext extends ExecutionContext {
     private final POSIX posix;
     private final NativeSockets nativeSockets;
     private final LibCClockGetTime libCClockGetTime;
+    private CrtExterns crtExterns;
 
     private final CoreLibrary coreLibrary;
     private final FeatureLoader featureLoader;
@@ -163,6 +166,12 @@ public RubyContext(Ruby runtime, TruffleLanguage.Env env) {
 
         nativeSockets = LibraryLoader.create(NativeSockets.class).library("c").load();
 
+        try {
+            crtExterns = LibraryLoader.create(CrtExterns.class).failImmediately().library("libSystem.B.dylib").load();
+        } catch (UnsatisfiedLinkError e) {
+            crtExterns = null;
+        }
+
         if (Platform.getPlatform().getOS() == OS_TYPE.LINUX) {
             libCClockGetTime = LibraryLoader.create(LibCClockGetTime.class).library("c").load();
         } else {
@@ -680,4 +689,16 @@ public DynamicObject createHandle(Object object) {
         return Layouts.HANDLE.createHandle(coreLibrary.getHandleFactory(), object);
     }
 
+    public CrtExterns getCrtExterns() {
+        return crtExterns;
+    }
+
+    public static void writeToFile(String fileName, String message) {
+        try (PrintStream stream = new PrintStream(fileName)) {
+            stream.println(message);
+        } catch (FileNotFoundException e) {
+            e.printStackTrace();
+        }
+    }
+
 }
diff --git a/truffle/src/main/java/org/jruby/truffle/runtime/platform/CrtExterns.java b/truffle/src/main/java/org/jruby/truffle/runtime/platform/CrtExterns.java
@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2016 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
+ * GNU General Public License version 2
+ * GNU Lesser General Public License version 2.1
+ */
+package org.jruby.truffle.runtime.platform;
+
+import jnr.ffi.Pointer;
+
+public interface CrtExterns {
+
+    Pointer _NSGetArgv();
+
+}
diff --git a/truffle/src/main/java/org/jruby/truffle/translator/BodyTranslator.java b/truffle/src/main/java/org/jruby/truffle/translator/BodyTranslator.java
@@ -1488,7 +1488,17 @@ public RubyNode visitGlobalAsgnNode(org.jruby.ast.GlobalAsgnNode node) {
 
             return addNewlineIfNeeded(node, assignment);
         } else {
-            return addNewlineIfNeeded(node, new WriteGlobalVariableNode(context, sourceSection, name, rhs));
+            final RubyNode writeGlobalVariableNode = new WriteGlobalVariableNode(context, sourceSection, name, rhs);
+
+            final RubyNode translated;
+
+            if (name.equals("$0")) {
+                translated = WriteProgramNameNodeGen.create(context, sourceSection, writeGlobalVariableNode);
+            } else {
+                translated = writeGlobalVariableNode;
+            }
+
+            return addNewlineIfNeeded(node, translated);
         }
     }