learning cross-platform development

Hello,

I am want to be able to write applications that will run on windows and linux.

I know there are libraries that help you do this, apache-runtime, glib, etc.

However, before I get into those I want to be able to do it at the low level, using things like this, and I am just a beginner:

Code:

---

#ifdefine WIN32
/* Do windows stuff
#else
/* do linux stuff */
#endif

---

I would like to understand this a lot a the low lever, and wondering if there are any good tutorials or ebooks that would help me get started?

Many thanks for any advice,

There is no real tutorial for these things because there is no need for any.
The first rule is to stick to ISO C. ISO C is always portable.
Second rule is when you have to use something else than ISO C, use a portable library, if possible.
Third rule is if you can't use a library, then put the functionality you need into a function and surround it by ifdefs like above, to customize that function to work differently for each platform.

These 3 basic rules will carry you to portability.

Cross-platform development is just using things that work on multiple platforms. If it doesn't work on say, both Linux and Windows, then you write a wrapper function that calls the appropriate calls on the appropriate OS, usually using techniques like you showed. For example, if I wanted a sub-second 'sleep' function, I'd have to write a function that, in Linux, calls usleep or nanosleep, but in Windows would probably call Sleep(). However, if I'm just opening a file for a quick write, I wouldn't use open() / CreateFile(), because there's already a portable function: fopen().

It's all just a translation of "what do I want to do" to "what OS calls do I need to make, and what's the most portable way to do it?".

Your example is not the best implementation what would be defined as "cross platform".

Good cross platform code has as few of those techniques as possible.

I would suggest learning C first, from a command line standpoint, using a C reference that has as little slant to any platform as you can stand.

Actually there are two books that deal with multiplatform development:

1. Write Portable Code: An Introduction to Developing Software for Multiple Platforms
2. Cross-Platform Development in C++: Building Mac OS X, Linux, and Windows Applications

I have an application that works on Mac OS 9/OS X and Windows and writing it was very hard and it took a lot of time and energy, but now it's a real pleasure. I just spend my days on Mac adding features and then just drag common files to Windows, recompile and voila: pure magic. Once you have it that way, it's like eating the cake and having it too.

;)

If you want to go really cross-platform, when you do the linux stuff go for POSIX compliance. This basically means avoiding a few GNU specific functions, which you probably want to do anyway.

But POSIX stuff compiles on linux flavours, unix (eg Sun), FreeBSD, etc. When I did my thing for debian, they asked that I keep everything POSIX compliant. It is a close subset of the C standard:

The Open Group Base Specifications Issue 7