= Compiling HelenOS From Source =

This section explains how to compile HelenOS from latest source code.

== Attention Newbies ==

This method is not recommended for beginners. If you are running HelenOS for the first time, please [UsersGuide/QuickStart run a pre-built, supported HelenOS image] (see instructions in that article).

Compiling an operating system is not quite simple as the {{{configure && make && make install}}} you use to compile your favorite application. If you still want to do it, please follow these instructions carefully. If you don't follow the instructions to the letter, it won't compile (or it will not run) and then don't bother us on the mailing list, please. We are somewhat tired of telling the people again and again to install the fine compiler toolchain.

== 1. Get the sources ==

Checkout the latest sources from our central Bazaar repository

{{{
bzr checkout bzr://bzr.helenos.org/mainline HelenOS
}}}

''Note:'' To get versions older than 0.4.1 you have to access the original Subversion repository

{{{
svn checkout svn://svn.helenos.org/HelenOS/trunk HelenOS
}}}

== 2. Build a supported cross-compiler ==

Use our script to install a supported cross-compiler toolchain

{{{
cd HelenOS/tools
./toolchain.sh ia32
}}}

'''Note:''' In older revisions of the source tree the ''toolchain.sh'' script was present in the ''contrib'' directory (not the ''tools'' directory where it is now).

== 3. Did you install the compiler toolchain? Good. ==

If you did not, it won't work! Don't even try to pester us about that. It won't work. Because it won't. It can't.

Why can't it work?
 * Tool versions: We only test HelenOS on the one single version of GCC, binutils, etc. We don't have the resources to test other versions. Other versions have bugs (or lack required features). It won't compile.
 * Different ABIs: Each OS has a different ABI and different set of compiler settings. If you build binaries with your native compiler, they will run fine in your OS, but certainly not in HelenOS!
 * {{{-Werror}}}: Developer builds use -Werror and each compiler version produces different warnings. Thus, you will get warnings and these get turned into erros.

== 4. Configure and build ==

Go back to the source root and start the build process

{{{
cd ../..
make PROFILE=ia32
}}}

Now HelenOS should automatically start building.

== 5. Run it ==

When you get the command line back, there should be an `image.iso` file in the source root directory. If you have Qemu, you should be able to start HelenOS by running

{{{
qemu -cdrom image.iso
}}}

there are also some start scripts and configuration files for other emulators in `contrib/conf`.

== Advanced: Manual configuration ==

'''Please Note:''' Normally '''you don't need to do this'''. Manual configuration was mostly used in the past where HelenOS had no command line. Nowadays manual configuration (and configuration options in general) are used much less and only when absolutely necessary (e.g. if you '''really''' need to build a smaller system). If you configure HelenOS manually and it does not build (or does not work), it is most probably your fault.

With manual configuration you can change screen resolution, disable building of some components, etc.

'''Warning:''' Do not select a different compiler unless you really know what you are doing! If you use ''gcc_native'' instead of ''gcc_cross'', it won't work, so please don't ask in the mailing list! Building HelenOS with a native compiler is '''not supported'''!

To configure:

{{{
make distclean && make config
}}}

alternatively

{{{
make distclean && make
}}}

this will cause HelenOS build to automatically start once you are done with the configuration.