Easiest way to build a cross-platform application

Question

I have read a few articles in the cross-platform tag. However, as I'm starting a fresh application (mostly a terminal/console app), I'm wondering about the easiest way to make it cross-platform (i.e. working for Linux, Mac OS X, and Windows). I have thought about the following:

• adding various macro/tags in my code to build different binary executables for each operating system
• use Qt platform to develop a cross-functional app (although the GUI and platform component would add more development time as I'm not familiar with Qt)

Your thoughts? Thanks in advance for your contribution!

Edit: Sounds like there are a lot of popular responses on Java and Qt. What are the tradeoffs between these two while we're at it?

Answer 1

Do not go the first way. You'll encounter a lot of problems that are already solved for you by numerous tools.

Qt is an excellent choice if you definitely want C++. In fact, it will speed up development even if you aren't familiar with it, as it has excellent documentation and is easy to use. The good part about it is that it isn't just a GUI framework, but also networking, XML, I/O and lots of other stuff you'll probably need.

If not necessary C++, I'd go with Java. C++ is far too low level language for most applications. Debugging memory management and corrupt stacks can be a nightmare.

To your edited question:

• The obvious one: Java has garbage collection, C++ doesn't. It means no memory leaks in Java (unless you count possible bugs in JVM), no need to worry about dangling pointers and such.
• Another obvious one: it is extremely easy to use platform-dependent code in C++ using #ifdefs. In Java it is a real pain. There is JNI but it isn't easy to use at all.
• Java has very extensive support of exceptions. While C++ has exceptions too, Qt doesn't use them, and some things that generate exceptions in Java will leave you with corrupt memory and crashes in C++ (think buffer overflows).
• "Write once, run everywhere." Recompiling C++ program for many platforms can be daunting. Java programs don't need to be recompiled.
• It is open to debate, but I think Java has more extensive and well-defined library. The abstraction level is generally higher, the interfaces are cleaner. And it supports more useful things, like XML schemas and such. I can't think of a feature that is present in Qt, but absent in Java. Maybe multimedia or something, I'm not sure.
• Both languages are very fast nowadays, so performance is usually not an issue, but Java can be a real memory hog. Not extremely important on modern hardware too, but still.
• The least obvious one: C++ can be more portable than Java. One example is FreeBSD OS which had very poor support for Java some time ago (don't know if it is still the case). C++/Qt works perfectly there. If you plan on supporting a wide range of Unix systems, C++ may be a better choice.