Category: C

A comprehensive small C compiler

A comprehensive small C compiler

Posted on by David
Programming image
Image by Gerd Altmann from Pixabay

Once you’ve learnt a fair bit of C, one way to increase your understanding of it is to see how a C compiler works. Unlike most other programming languages, C compilers are generally understandable. There have been a few tiny or small C compilers around and here is another one though as its C111 compatible, it might be more useful than older ones.

The author is well qualified to write this, he’s the author of the llvm lld linker and also an earlier C compiler 8CC. He notes “chibicc can compile several real-world programs, including Git, SQLite and libpng, without making modifications to the compiled programs. Generated executables of these programs pass their corresponding test suites.”

Rui is writing a book on the C compiler and this is the subject of the book. It’s not out yet but will be in my must buy list.

Tutorial 3 on Enum variables published

Tutorial 3 on Enum variables published

Posted on by David
Magic Numbers
Image by John Hain from Pixabay

This is the third in a series of C Tutorials that I originally published on about.com between 2006 and 2013.  I’m republishing them on here. This time it’s about enum variables. While these aren’t anywhere as important as say in C++ or other languages (because C’s type checking is not great!) they make the program more readable.

I see them as banishing magic numbers. A magic number is a number in a program that is just there. Like when you declare an array and use the number 20. That is a magic number and it would be better if there was a #define NUMBERMONSTERS 20.  This avoids the problem of your program being full of 20s until one day you change it to 30 but manage to miss a couple of them and you introduce bugs. By using NUMBERMONSTERS everywhere you can change it in just one place (at the #define) and avoid the problem of missing.

Enum variables are similar. Behind the scenes they are just ints. In other programming languages like C++, Pascal, C#, the compiler enforces the enum values. In those languages you can’t declare an enum variable then assign any int value to it, but in C you can.  But they can at least make your program more readable.

The picture? Magic numbers!

To brace or not to brace

To brace or not to brace

Posted on by David
Abstract programming picture
Image by Gerd Altmann from Pixabay

This isn’t exactly confined to C, in fact it applies to many programming languages where braces or curly brackets {like this} are optional after an if. It even applies to Pascal with Begin ends which are optional after an if.

You can have the first or the second as shown below.

if (expressions) 
  DoSomething;

if (expression {
  DoSomething;
}

I saw a recent example where the DoSomething was a logging expression which the compiler optimised away so the if, which lacked braces applied to the next statement. As the if was only true on rare occasions. It meant that that statement which should have been run every time was only run on those rare occasions.

So the prevailing wisdom and one that I entirely agree with is that you should always use braces. If you don’t you risk accidentally introducing bugs like this.

Note. that link is to a discussion on the C programming Subreddit (on Reddit.com).

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A lovely MiniGolf game in C

A lovely MiniGolf game in C

Posted on by David

MiniGolfA developer called Michael Gerdes just published a MiniGolf game on GitHub. This uses OpenGL for the graphiocs and according to GitHub is made up of

  • C 76.5%
  • C++21.4%
  • GLSL 0.8%
  • Scheme 0.7%
  • Objective-C 0.6%
  • HTML 0.0%

Every project on GitHub has these on the RHS of the home page. They include links with filters to see the particular set of files. Particularly telling is GLSL which are shaders. If you do 3D graphics, that’s something you need to learn. Its why I stick to 2D. The other stuff probably comes as part of various linked libraries.

It’s nicely done and the GitHub page has four animated gifs showing how it works. It also uses the open source Dear Imgui GUI library.

A portable Windows Devkit

A portable Windows Devkit

Posted on by David
Tool icons
Image by mohamed Hassan from Pixabay

I spotted this the other day. A C and C++ development distribution for Windows called w64devkit. It’s less than 80 MB and you don’t need to install it so you could easily fit it onto a USB memory stick or download it.

As the author (Chris Wellons) says “Despite its simple nature and small packaging, w64devkit is almost everything you need to develop any professional desktop application, from a command line utility to a AAA game”. Note it doesn’t include source control, nor does it access the internet, though no doubt you could. So you could backup stuff say to GitHub or wherever.

I am fan of software like this that you can take with you on a laptop or a memory stick. You don’t always have to have a full dev system with multiple monitors, Visual Studio etc.

If you’re interested, do read the entire blog post.

 

First C Tutorial published

First C Tutorial published

Posted on by David

TutorialAs I add these (one or two each week), I’ll add them to the tutorials page. The first is introducing C Programming and has the almost mandatory Hello World.  To speed up trying the code out, I’ve included links to two online C compilers where you can run the program.

The two online compilers Ideone.com and Codepad.org were both around when I wrote the original tutorial and the original C program (Ideone) link still exists on Ideone. (After you compile a program successfully they provide a shortcut back to it).

I’ve taken the original C tutorials and have stripped all the cruft (CSS, much Html, and JavaScript) and edited slightly).  It helps that I wrote them originally back around 2006-2007. There’s approximately 30 in total. I will be beefing them up as well.

Follow the Tutorials link on the top menu.

My earlier work in C, C++ and C#

My earlier work in C, C++ and C#

Posted on by David

Cplus.About.com screenshotThe tutorials I wrote on C++ and C# on cplus.about.com between 2006 and 2013 are all a bit dated now. Both languages have been updated several times since 2013 when I stopped writing for About.com. But thanks to the Wayback machine you can view all of my work from the early stages in Mid 2006 to the finish in July 2013.  I owe the copyright to this material so I can reuse it as I wish.

On this page, there’s an index to 43 C tutorials, most written by me.  So as a little side task, I’m downloading these, cleaning them up, fixing the odd error and adding them to this website via the Tutorials page. Some but not all are also available on the ThoughtCo website which is the reinvention of About.com.

Ironically I got better at writing for them towards the end. About.com had been very successful back in the late 90s when the web was still fairly new but could never sustain that and declined more or less from the year 2000. I think the highest daily viewing figure I ever got was 12,000 pages but some of the others (particularly Southern Cooking) got in the millions.

I recommend you visit archive.org earlier in the day as it slows up a bit once the USA wakes up typically around 1.00 PM (GMT). Given the volume of stuff it stores, it is a totally amazing place.

Quake II – still a favourite

Quake II – still a favourite

Posted on by David

Quake II screenshotOh I do play much newer games such as Far Cry 5 which I’ve completed recently but Quake II was a favourite of mine back in 1997 when I bought it. I’m more of a Quake than a Doom person. Unfortunately for me, my then PC couldn’t run it. It was only two years old as well.  But I got a new PC in 1998 and that played it just fine. I’m not saying I’m a saddo but I can play it through on the hardest level without losing a life.

The reason I mention it because of an article I came across that described the different ID Tech Game engines and the games made with each engine. All have been open sourced (Up to ID Tech 4). Quake II was written using the ID Tech 2 engine itself written in C and assembler.

For some reason the link to Quake II source code is wrong in that article but you can find it on GitHub. In one of 18 of ID Tech’s 18 repositories there.

If you are interested in downloading and trying to understand the Quake II source code, I strongly recommend you read Fabien Sangard’s walkthough of the code.

C11 and C17 support in MSVC

C11 and C17 support in MSVC

Posted on by David

 

The letter C
Image by Peggy und Marco Lachmann-Anke from Pixabay

Microsoft have announced that they will be supporting both C11 and C17 in Visual Studio 2019 version 16.8 Preview 3. All the required features but not optional features and not VLAs (Variable Length Arrays) which is considered unsafe.

One of the complaints has been that Microsoft always prioritised C++ over C for many years. C was supported inasmuch as it was needed for C++. Until fairly recently C++ was a superset of C and you could compile C program as C++. Just change the extension to .cpp.

That said, I will probably continue to write C code as C99 for now and take a look at the C11/C17 features such as restrict, stdnoreturn and so on.  Note C17 is considered a bit of a bug fix for C11.