A very good friend of mine, Chris Lynch, will be at Ace Comics in London on March 20th to sign copies of “The Dark”, which is an exciting new comic book series written by Chris with amazing artwork provided by Rick Lundeen. Festivities start at 12pm. This is your chance to get a signed copy of a great series in the making – a chance not to be missed, so c’mon! :)
Tuesday, January 26, 2010
Monday, January 25, 2010
One of the most powerful command available in the SOS.dll is !gcroot. It can help you figure out why an object is stuck in memory and what object(s) is referencing it and keeping it alive. The one problem with !gcroot is that it’s output can be very difficult to navigate through. I remember when I first used this command to try and debug an issue for an application at work, at first I was excited at getting the chance to use this command on a “real world” issue. However, that excitement turned to bewilderment when I saw the output of !gcroot and I just sat there for a few moments whilst I tried to work out what exactly the output was trying to tell me.
Well that was then, and since those days I’ve learned a little bit more about how to read !gcroot’s output. Studying blogs such as this one has helped a lot. Today I was reading John Robbins' blog and I saw a link to this tool, which is an object graph visualizer which runs in VS 2010. The author has created a video to demonstrate this tool and I must say, it looks very interesting! I suggest you check it out.
Sunday, January 10, 2010
When I started out to teach myself how to program I was always a bit bewildered by assembly language. I often looked at example code from online forums and starred at strange syntax such as this:
mov EAX, [EBP+8]
lea EDS, EAX
I thought '”How can you possibly write software using this stuff?”. Obviously I was being naive since compiling a Visual Basic, or C++ Builder application (my two favorite development tools at the time – others included PowerBASIC) ultimately was generating exactly this “stuff” which the CPU could make use of. As I became more proficient as a programmer, I noticed that I was looking more and more at assembly language code during my debugging sessions. Very often in the C++ Builder IDE I would be watching the values of the EAX and ECX registers, so that I could see the return value of a function or the current loop index value. Little did I know that I was starting to appreciate more the power of this language and what could be achieved.
Back in the early 2000’s I downloaded MASM32 which is a Microsoft assembler and RadASM, a great IDE for writing assembler code. With those tools I was able to write very simple assembler stuff, mainly DLL files that I could use with my Visual Basic 6 applications. It was so cool to see my VB6 code call an assembler routine, passing it a string that was displayed in a message box – a message box created in pure assembly code!! (I guess you had to be there :) What I was learning by doing this was how different calling conventions worked, how to build a DLL file using the assembly source and static library references. By passing a parameter from my VB code, I had to learn how to navigate a stack frame by using the ESP and EBP registers to get to the parameter’s address and grab its content in order for MessageBox to use it. I learned that:
mov EAX, [EBP+8]
actually meant “move the contents of memory address EBP+8 into the register EAX – in other words dereferencing a memory address. Having done a fair amount of C/C++ programming and using pointers, I was getting under the hood experience of how pointers worked at the assembler level. This actually helped me understand pointers better.
OK, so what am I getting at here?
In this day and age of managed runtimes and virtual machines, .NET languages, PHP, Perl, PowerShell, etc, some developers might be asking themselves “what’s the point of learning assembler? It’s not like I’m ever going to use it!”. That might very well be the case, but bear in mind this thought – without good assembly language developers, there would be no operating systems. Let me explain. Taking into account Windows and Linux for example, the vast majority of the codebase for these OS’s are written in C/C++. I would place a very large bet that a small percentage of the code is written in assembler. Assembler code must exist somewhere in the OS since talking directly to hardware would not be possible. Without those hardcore assembler developers, who’s going to look after this code? If there’s no new talent on the horizon, that would be a deficit to the OS developers who rely on assembler programmers who can churn out this low-level communications code which is vital for the OS’s existence.
Take computer games, there’s bound to be a lot of assembler code in the source for computer games – for example, code to optimize the graphics algorithms so that the frame rate can be really high. A lot of games are written in C/C++ but nothing beats assembler for pure speed. Also you sometimes can’t as easily take advantage of CPU specific instructions from a higher level language, only coding in assembler can give you access to those instructions.
One of the most important areas where assembly language experience counts a lot is crash dump analysis. In my early years I would often see a BSOD and wonder “how can you tell what’s broken just by looking at this crap?!… What’s a bugcheck and how what’s this stack frame rubbish?” Now things are different. I’ve been reading blogs such as Crash Dump Analysis and the NT Debugging blog to help me understand how to analyze and interpret the information in dump files. I’ve also taught myself how to use WinDbg which is a free debugger for Windows. I’ve spent a lot of time recently working with SharePoint 2007, and believe or not, having WinDbg and assembly language experience has come in very handy! How? Well, SharePoint 2007 isn’t the most, how shall we say, “consistent” platform to use. You might get an exception one day that has the following message:
“Something's happened, it’s broken the site, so… there you go”.
(OK, not what you actually get, but in some cases the exception message is totally useless).
When I see an exception message which is useless, I attach WinDbg to the w3wp.exe process running the “broken” SharePoint and I can see the real exception that caused a problem, and sometimes I might have to step into the running code at assembler level to see what’s going on. I don’t have to this often, but the fact that I have this in my arsenal has saved me a couple of times from punching the wall the frustration as to why I’m getting an error.
I strongly believe that learning assembler makes you a better developer, but that’s just me. Check out the following Stack Overflow questions on the matter, see what you think:
Is learning Assembly Language worth the effort?
Why do we teach assembly language programming?
Why do you program in assembly?
Should I learn Assembly programming?
Is there a need to use assembly these days?
What are the practical advantages of learning Assembly?
One thing that stood out most about PCW was the diverse topics which were included in the back pages, such as a monthly column on mathematics. Now, I don’t recall off the top of my head what exactly was discussed in that column, but I can’t think of another magazine at the time (or since) that offered such as section. I thought it was pretty cool, regardless of the fact that I understood very little of it!
Over time I bought the magazine less and less, to a point when I stopped buying it entirely. This wasn’t a decision I made point blank, it just kind of happened organically. A couple of years ago I was browsing through PCW in my local Tesco; I noticed how the magazine had suffered the decline like many other computer magazines – not as much content (I think it barely reached 100 pages). It still had many reviews and such, but it just didn’t feel quite as “heavy” as it did in the 90’s. It felt there was something missing. Even so, it came as a bit of a surprise that in the summer of 2009 I noticed that my local Tesco didn’t seem to be stocking PCW anymore. A recent search on Google lead me to this page. Here Gordon Laing give his postmortem on PCW and why it died off.
This is a real shame. Yes, I wasn't buying the magazine each month, but still, I felt like an old friend had vanished forever (over the top I know, but you know what I mean :) Other mags such as PC Pro don’t feel like they give the same value as PCW did. PCW does still exist on the web, but it’s publishing days are well and truly over :(.
Saturday, January 09, 2010
One thing that’s been tricky at our company has been requirements management. There’s no problem gathering requirements and creating a document that describes them, the trouble comes when we need to create TFS (Team Foundation Server) work items based on those requirements. There’s always a chance of a requirement being lost (especially true for very large documents) and not getting a TFS work item created for it – a big problem indeed. Certainly there have been cases when a missed requirement was not discovered until near the end of the a project, a rather large ‘ouch’ moment!
In the past, a colleague of mine did tinker with a prototype Word addin that allows a user to highlight sections of a Word 2007 document and mark it as a requirement. He never finished it, mainly due to time, plus the scale of what we needed as a requirements management solution needed something more then just a simple addin. However, I’ve just found this very interesting product – ‘TeamSpec for TFS Requirements Management’. I’m keen to have a look at this since it could be just the ticket for us. Basically this application allows you to integrate Word 2007 documents with TFS, giving you the ability to create work items and link them into the document. The advantage is that you are linking directly between the document and the work items, which means, for example, when viewing the document you get a live update of that work item’s state (if the ‘State’ field has been included in the document).
Not only that, but it also saves time since currently we must write the requirements document, then someone has to go through the document again, picking out each requirement, and creating work items for them. Very tedious; this was crying out for a better solution! There’s a nice explorer window that appears in Word which shows you the work items linked into the document:
On the right is the explorer window which is showing 4 work items. Each work item is described in the document in the bullet points. You can pick and choose which work item fields to display in the document, each field in binded to the work item in TFS which means that any updates to a work item in TFS is synchronized in the document. There’s a lot of cool features in this product, check out the site and see for yourself.