Win32 Linked-In Drivers and A Project Idea

I’ve been living in linked-in driver land for the past few weeks. I guess that’s what I get for publishing basic_erl_driver. It’s been interesting work so I certainly haven’t minded doing it.

Well, I didn’t mind it until I had to build one of my drivers on Windows. It’s been a long time since I’ve done much Win32 development but I used to know my way around Visual C++ pretty well. “I used to do this shit for a living. How hard could this be?”, I thought to myself.

Three words: famous last words.

Three more words: C++, linker, XML.

Two final words: sheer frustration.

After wrestling with Visual Studio Express C++ Edition 9.0 (or whatever crazy name MS uses) for a day and a half I finally have a working driver. Here’s the nuggets o’ knowledge I learned along the way. These notes assume you’re porting a working driver from OS X/Linux/BSD to Windows although most of them are applicable if you’re starting from scratch on Windows, too. They also assume you’re building code from inside of Visual Studio because, frankly, I don’t care enough about Windows to figure out nmake, too.

• Start with a blank Win32 DLL project. Don’t let Visual Studio create stdafx and friends. Down that path lies madness. You’re much better off to create a blank project and import your code.
• Add the erts-<version_number>/include directory to your project’s include path. You’ll need this so the compiler can resolve erl_driver.h.
• Don’t forget to include string.h before erl_driver.h. erl_driver.h uses memcpy() without including string.h. Including string.h first will fix a compiler warning and a possible runtime crash.
• Very Important: Right-click your project and navigate to the Linker -> Manifest File option.  Enter this magical text into the Additional Manifest Dependencies field:

  type='win32' name='Microsoft.VC90.CRT' version='9.0.21022.8' processArchitecture='x86' publicKeyToken='1fc8b3b9a1e183b'
  

  I believe this tells the compiler to link the DLL with the Visual C++ 9.0 runtime. This is the equivalent of the C stdlib on other platforms, I think. Erlang will be unable to load your driver if you skip this step.

---

Observation: Who in their right fucking mind thought it was a good idea to add XML descriptors to the link step of building a C library?! I take back every bad thing I’ve ever said about Java’s use of XML. SOAP, with all of its angle brackety warts, almost looks sane in comparison.

---

• With the previous step accomplished you’ll need to distribute the VC++ runtime with your driver. Luckily, MS provides the code in a redistributable form here inside the Microsoft Visual Studio 9.0VCredistx86 directory structure. Grab all of the files in there and plop them into the same directory as your driver’s DLL file.

There are probably better ways to accomplish the same goal given my dated platform knowledge. If you know of a better way to do this, please drop a comment and set me straight!

One of the drivers I’ve been working on is to allow SpiderMonkey to interface with Erlang. I’ve asked and am waiting for permission from my client to open source the code since I think it’d be generally useful. If that doesn’t pan out I’m strongly considering doing another driver — open source from the beginning — to interface with V8 or possibly WebKit’s engine. I’ve got some ideas on how JSON could smooth the interop between the two languages. Anyone up for either working on or sponsoring work on this?

Comments

Why bother with the horrible MS tools. I did a win32 driver using mingw (from linux)
Easy.

Posted by klacke on 21 Jun 2009 at 19:40

Didn’t know the forum rules allowed such brlilaint posts.

Posted by Cherry on 05 May 2011 at 19:57

2iUROk ppynjfxkttdi

Posted by mehswyc on 09 May 2011 at 16:13

accutane 3410 levitra and grapefruit juice %-DDD tramadol :mad:((

Posted by HaydenDaBomb on 23 May 2011 at 01:52

Add comment