Friday, June 25, 2010

Chromium Embedded continued

Previously I got the Chromium Embedded (CEF) sample application to compile (and run). That was only a tiny step towards what I needed to do.

Suneido has a DLL interface, but it can only handle straightforward interfaces. Although CEF has a DLL with a C interface, it's fairly complicated. So I decided I needed to write a small DLL that Suneido could call that would talk to CEF.

But I wasn't sure what the minimum functionality I'd need. The sample application is actually quite large and complex because it is demonstrating a bunch of features like extensions and plugins. So I started by whittling down the sample to the bare minimum. That process helped me identify the core functions I'd need.

It took me a certain amount of struggling to recall / figure out how to build a Windows DLL. (It's not something I do very often.) Eventually I got to the point where Suneido could see the DLL functions. But calling them didn't work (it gave some weird stack errors). Now what?

Then I remembered the issues with building single-threaded versus multi-threaded. The main version of Suneido we use is built single-threaded (/ML), but CEF is built multi-threaded (/MT). I tried it with a multi-threaded build of Suneido and it worked! (Suneido is still single-threaded, it's just linked with the multi-thread runtime libraries.) Here is Chromium Embedded running in a Suneido window:

Coincidentally, the single/multi-thread version issue has also come up in another area. I'm looking at upgrading my work computer to Windows 7. But before I take the plunge I want to make sure the software I need is going to run under Windows 7. One of the "oldest" packages I use is Visual C++ 2003 (VC7). I would have moved to a more recent version long ago, but VC7 still generates the smallest, fastest executable. I think the main reason for this, is that VC7 was the last version that supported building with the single-threaded libraries. (/ML) I'd prefer to use GCC but it doesn't handle the interface with the Internet Explorer browser component. (It's also a bit slower, but not too bad.) So using CEF instead of IE might also allow switching to GCC.

Thursday, June 24, 2010

Updating ASM

jSuneido uses ASM to generate Java byte code. I was using 3.1 and the current version is 3.3

I wasn't sure if this would be easy or hard. It turned out to be somewhere in between.

First I tried to update my Eclipse plugin. That was a little confusing because I had three update sites showing ASM -,, and I'm guessing the one is something internal to Eclipse. I thought would be the correct location, but it didn't have the latest version.

Next I downloaded asm-3.3.jar but that didn't work, I needed to download and extract asm-all-3.3.jar  This wasn't entirely a surprise because previously I was using multiple asm jar files. I'm not quite sure why the asm-3.3.jar is available as a separate download, but not the asm-all-3.3.jar

Of course, tests failed. The first message was:

java.lang.IndexOutOfBoundsException: Trying to access an inexistant local variable 0
at org.objectweb.asm.tree.analysis.Frame.setLocal(Unknown Source)
at org.objectweb.asm.tree.analysis.Analyzer.analyze(Unknown Source)
at org.objectweb.asm.util.CheckMethodAdapter$1.visitEnd(Unknown Source)
at org.objectweb.asm.util.CheckMethodAdapter.visitEnd(Unknown Source)
at org.objectweb.asm.tree.MethodNode.accept(Unknown Source)
at org.objectweb.asm.commons.TryCatchBlockSorter.visitEnd(Unknown Source)
at org.objectweb.asm.MethodAdapter.visitEnd(Unknown Source)

[I thought "inexistant" was a typo, but it appears to be the French version of nonexistent.]

I searched for other people having this problem and found:
ClassWriter.COMPUTE_FRAMES causes java.lang.ArrayIndexOutOfBoundsException

I didn't resolve this. As a workaround I use CheckClass(visitor, false) to turn off the data flow checks. I am probably doing something wrong, but the byte code passes Java's verification and it runs ok, so presumably it's nothing too serious? 

The next problem was that you now have to call visitTryCatchBlock before defining any of it's labels. At first I thought that was easy to fix, just move the calls from the end of the try-catch block to the beginning. But one test failed - with nested try-catch blocks. The problem is that the JVM searches the exception table in order. So inner blocks must come before outer ones. By emitting at the end of the blocks I got the right order. But now that I was forced to emit at the beginning of the blocks, the order was wrong. 

This stumped me for a while. The problem is that jSuneido (and cSuneido) compiles in a single pass, generating code as it parses. This avoids building a syntax tree. But it doesn't give much flexibility in the order of generating code. I was having scary thoughts of having to make two passes, or switching over to building an intermediate tree. Of course, I could just go back to ASM 3.1, but in the long run I'd probably need to upgrade (e.g. for invoke dynamic support).

Again I searched for other people having this problem and didn't find anything. I was going to post on the ASM Tracker, but before I did I figured I'd better make sure there wasn't an existing post. As it turned out there was: Provide exception table sorting functionality (I'm not sure why my Google searches didn't find it.) Not only had someone else had the same problem, but they'd come up with a solution, and it was now included in ASM. All I had to do was add TryCatchBlockSorter. It's actually quite simple, once you know that the table is accumulated in a way that allows it to be sorted.

Still, I'm not sure why they added this requirement. It seemed to work fine without it in the previous version.

After that, I just had to fix a few tests to take into account the slight differences in the generated try-catch code and I was back in business.

Friday, June 18, 2010

Chromium Embedded

Our Suneido applications use the Internet Explorer browser component included in Windows.

This works pretty well, but we are running into a few problems:
- people have a wide variety of IE versions
- some people have Javascript turned off
- security settings are getting more and more restrictive

And in the long run I'd like to run on Mac and Linux which don't have IE built in for some reason :-)

So I've been thinking about using another browser component that we can have better control over. Initially I was looking at Gecko (the Mozilla Firefox engine). There's even a Mozilla ActiveX control with the same interface as IE, but it requires registry changes which isn't always feasible for our clients. I tried to find a workaround for the registry issue but couldn't get it working (and no one on Stack Overflow had an answer).

The recent trend seems to be to use WebKit - like in Safari, Chrome, Google Earth, etc. I found the Chromium Embedded project that seems like it would do the trick.

As a first step, I thought I should try to build the example application.Four hours later I think I have achieved this. Since it wasn't easy, I thought I'd recount the saga in case it might help someone else.

First, the standard build environment seems to be Visual Studio C++ 2005. I had various other version installed but not that one. Unfortunately, it's been replaced by VS 2008 which I tried building with, but it gave a lot of errors. (Although maybe the fixes below would have worked?)

A Stack Overflow post led me to someone's page with links to old versions. When I installed, I got compatibility warnings which suggested some updates. I downloaded the updates but when I tried to install it failed, saying the software wasn't installed. (Even though I could run it.) Instead, I was able to get the updates by running Windows Update.

When I tried to build it couldn't find atlbase.h  That's because Visual Studio Express (the free version) doesn't come with the Windows SDK. I already had a Windows Server 2003 SDK installed so I updated Tools - Options to point to it.

But I still got errors about shlwapi.lib missing. It turns out this is part of "Microsoft Web Workshop (IE) SDK", an optional part of the SDK. So I tracked down the right SDK installer and installed it.

Next, I had to patch atlbase.h and atlwin.h as explained in a Code Project post. This cleaned up a bunch more errors. But I was still getting errors about _Module which I fixed based on yet another post.

Then I got errors that I was missing opengl32.lib which stumped me for a while till I found someone else with a similar problem, and ended up at instructions for adding the SDK libraries to Visual Studio. Since you don't actually need opengl32.lib, I'm not sure why the project specifies it.

Initially the Debug version built. It ran, but it had a bad tendency to crash. The Release version seems to be fine.

Another issue is that it's big, about 20mb for the required dll's. I guess that's not that big these days, but it's still a fair size to deploy over the internet.

This all seems way harder than it should be. I realize it's Windows and Visual Studio and C++ and open source, but still! Maybe I've been spoiled by working with Java lately. Java does have benefits.

Wednesday, June 16, 2010

Azul's Better GC

InfoQ: Azul Systems To Open Source Significant Technology in Managed Runtime Initiative

Interesting. The more cores you have, the more garbage collection (GC) you need - a result of the shared memory model. So even if you avoid killing your multi-threaded performance with locking overhead, you still have scaling issues with GC.

This may also put pressure on Java to do more to avoid heap allocation (e.g. escape analysis and fixnums).

Tuesday, June 15, 2010

Responsive Web Design

A List Apart: Articles: Responsive Web Design

Nice techniques for handling todays huge variation in screen size - from mobile phones to 30 inch monitors.

Wednesday, June 02, 2010

Phone Companies Antics

I had a phone call from Rogers yesterday trying to sell me a "Rocket Stick". I asked if I could use my existing data plan. "Oh, do you have a data plan?" they replied.

I wish these companies would get their act together and use the information they have. They say they're calling me because I'm a "valued customer" but they don't even have my account information. Of course, it's probably a different department or outsourced or one of a dozen other excuses. But it makes them look stupid. One of the first rules of selling is to know your customer.

So they asked me what my plan was ($30 per month for 6gb) and told me "Yes, you can switch to a shared plan". I was pleasantly surprised because I assumed the answer would be "no".

The new plan would be $45 per month for 1gb. Wait a minute, you want me to pay 50% more for 1/6 the service? "Yes, but it would be shared."  No thanks, doesn't sound like a good deal to me. (I don't use 6gb and 1gb would probably be fine, but I still don't want to pay more for less! And with 6gb I don't have to worry about my usage, which is a big plus.)

Actually, what I'm really interested in is the Mobile MiFi Hotspot. Then I could use it with my laptop and Shelley would use it with her iPod Touch or laptop at the same time. (Plus any future wifi devices.)  I'd looked this up before, but it just said "Out of Stock". I asked about it and they told me they used to have them, but there was some problem with the batteries. That sounded a little lame to me - they're still selling them in the US.

Note: In theory I can share my data plan by tethering my MacBook to my iPhone but it hasn't worked too well when I tried and I haven't spent the time to figure it out. And I don't think that would help with other devices.

see also: AT&T’s cynical act

Tuesday, June 01, 2010

Impossible Things

"Why, sometimes I've believed as many as six impossible things before breakfast." Alice in Wonderland

I was testing jSuneido on a Windows system and I got:
        at java.nio.MappedByteBuffer.force0(Native Method)
        at java.nio.MappedByteBuffer.force(

So I went to add a try-catch to log this error. But Eclipse told me MappedByteBuffer.force doesn't throw IOException

I check the documentation but it didn't mention IOException either.

This is a "checked" exception, meaning you can't throw it without declaring that you throw it, and you can't call something that may throw it without catching it.

But I guess all that goes out the window when you get down to native methods.

I just caught the more general base Exception instead.

PS. I wasn't able to recreate the error, I just hope it won't come back to haunt me.