Steven Yong's Weblog

Okay now after beating Newcastle United for 5-1, Liverpool's gained 45 points after 20 matches. The closest to challenge Liverpool would be Manchester United assuming it would be winning all 3 upcoming matches, while Chelsea is sinking and Arsenal is still striving for a seat to next season Champions League.
There is nothing more exciting than seeing Liverpool chasing for its first title since Premier League was formed in 1992, and it is also the only team that can score 5 goals without a striker lined up. How amazing?! Keep going Liverpool, you have the best start ever.

Very often I will get email reply like this:

Please see my reply in red.

I'm not color-blind, but I view my email in plain text format. Please follow the correct convention of replying email, something like this:

> I will be in town this week.
> Do you have time to meet?
Yes.

>> I will be in town this week.
>> Do you have time to meet?
>Yes.
What about next week then?

So lastime I wrote about how to modify constant data using reflection in Java, now I'm going to try to modify constant data in C, using pointer.

Consider code below:

int i = 0;
const int ci = 0;
printf("ci initial value %d\n", ci); /* print 0 */

int* pi = &i; /* a pointer to int */
const int* pci = &ci; /* a pointer to const int */

//ci = 1; /* try to assign new value to const, compile error */
//*pci = 1; /* try to assign new value to const, compile error */

pi = (int*)pci; /* cast pointer to const to pointer, success */
*pi = 1; /* no compile error, weird */

printf("ci value %d\n", ci); /* result? */

What result? Answer is undefined and compiler-dependant. On GCC C compiler, constant data gets modified, but on Visual C++ compiler, constant value remains and no runtime error, that means the line *pi = 1 has no effect at all.

There are at least 3 basic ways to assign value to array element in C.

Say we have an integer array defined like this:

int an_array[3] = {1,2,3};

We can change the value of each element using following three ways (there might me more ways).

1) Most common one, using array index.

an_array[0] = 10;
an_array[1] = 20;
an_array[2] = 30;

2) Using pointer, since array is implemented by pointer anyway.

*an_array = 10;
*(an_array+1) = 20;
*(an_array+2) = 30;

3) Using address casting, assuming integer type use 4 bytes on your machine. This method cast the pointer integer value to integer pointer and goes from there.

int addr = an_array;
*(int*)addr = 10;
*(int*)(addr+4) = 20; (change to addr+8 if your int is 8 bytes long)
*(int*)(addr+8) = 30; (change to addr+16 if your int is 8 bytes long)

Lastime I talked about the command for checking out source code with CVS and Subversion. Now I'd like write about the command of Mercurial and Git.

Mercurial is a source code management system currently used by many famous open source projects like NetBeans and Firefox web browser. To check out source codes from respository, follow this:

hg clone <repo url> <destination>

e.g.:

hg clone http://hg.mozilla.org/mozilla-central/ src

While concept like check out and check in is famous for CVS, Subversion and SourceSafe, Mercurial and Git use different terms for similar concept, which are pull and push. Pull is retrieving bits from repository and push is putting back updates to the repository.

To pull latest copy from server:

hg pull -u

Git, not as famous, but the software codes that managed by it can be considered as one of the leaders of open source, which is, Linux kernel (Ruby on Rails also one of them). This thing is first created by Linus Torvalds written purely in C, and it stands for Fast Version Control System.

To check out code using git, do this:

git clone <repo url>

e.g.:

git clone git://git.videolan.org/vlc.git (getting VLC Player source code)

And to get latest copy:

git pull --rebase

We might not able to use Windows XP setup CD to install Windows XP on some desktops/laptops that come with Windows Vista, due to the missing of hard disk controller drivers. Those drivers is for certain newer hard disks with some "enhanced" feature built-in. In order to be able to install Windows XP, you can go into BIOS and enable the native SATA control but this requires a little hard disk knowledge and it is a BIOS-dependant trick. Or you can follow this article to modify your Windows XP installtion CD by inserting some drivers and reburn another one.

This article really clears my confusion on the .NET stuff. Now that I know even we are running a .NET application written with .NET Framework 3.5 (the latest as of today), underlying there is still the CLR in .NET Framework 2.0 which is actually running the app.

In short, for .NET Framework version higher than 2.0, there are just some additional libraries being added, the runtime engine (CLR) is still the original version 2.0.

Philip Zembrod tells us that how could we improve coding productivity by writing test first. Writing unit test does make sense for things like class interface (though I've never tried this apporach), but what about the testing for UI code and component integration?

For functionality and integration test, I think running test first can also bring high value.

Although we are not going to write test code for that, we still run tests based on our functional specification. Few months back when the software I'm doing wasn't even half completed, we've started testing the software. When we see a total missing feature, we file a bug, then the programmer in-charge would have to implement it. When we able to access a feature which we are not supposed to, we file a bug, then the programmer would have to add the security checking. If we still able to login to the system even we'd just suspended ourselves, we file a bug, then there will be another check added.

Actually all these are stated very clear in the spec, but as you know, nobody read spec. But surprisingly, they do care about their number of bugs, thanks to the weekly meeting, which discusses about defects.

Everything works fine, except that now the responsibilty of reading spec has been transferred to the poor testers.