docs/overview.txt
author "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>
Fri Mar 05 09:19:56 2010 +0100 (2010-03-05)
changeset 1842 2535545dd450
parent 1803 2c0ed9ec9a8c
child 1843 266166448ffd
permissions -rw-r--r--
config: prepare for build-system backend

When acting as a backend for a build-system, we should not build
any application that runs on the target, that is:
- no native gdb
- no companion libraries
- no binutils libraries
- no debug tools (save for gdbserver)
- ...

Here, we simply prepare the (hidden) config option that will detect
that we are acting as a back-end.

Update doc accordingly.
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File.........: overview.txt
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Content......: Overview of how crosstool-NG works.
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Copyrigth....: (C) 2007 Yann E. MORIN <yann.morin.1998@anciens.enib.fr>
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License......: Creative Commons Attribution Share Alike (CC-by-sa), v2.5
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____________________
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                   /
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Table Of Content  /
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_________________/
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Introduction
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History
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Referring to crosstool-NG
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Installing crosstool-NG
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  Install method
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  The hacker's way
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  Preparing for packaging
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  Shell completion
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  Contributed code
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Configuring crosstool-NG
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  Interesting config options
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  Re-building an existing toolchain
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  Using as a backend for a build-system
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Running crosstool-NG
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  Stopping and restarting a build
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  Testing all toolchains at once
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  Overriding the number of // jobs
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  Note on // jobs
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  Tools wrapper
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Using the toolchain
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  The 'populate' script
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Toolchain types
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  Seemingly-native toolchains
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Contributing
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  Sending a bug report
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  Sending patches
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Internals
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  Makefile front-end
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  Kconfig parser
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  Architecture-specific
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  Adding a new version of a component
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  Build scripts
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________________
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               /
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Introduction  /
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_____________/
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crosstool-NG aims at building toolchains. Toolchains are an essential component
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in a software development project. It will compile, assemble and link the code
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that is being developed. Some pieces of the toolchain will eventually end up
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in the resulting binary/ies: static libraries are but an example.
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So, a toolchain is a very sensitive piece of software, as any bug in one of the
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components, or a poorly configured component, can lead to execution problems,
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ranging from poor performance, to applications ending unexpectedly, to
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mis-behaving software (which more than often is hard to detect), to hardware
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damage, or even to human risks (which is more than regrettable).
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Toolchains are made of different piece of software, each being quite complex
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and requiring specially crafted options to build and work seamlessly. This
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is usually not that easy, even in the not-so-trivial case of native toolchains.
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The work reaches a higher degree of complexity when it comes to cross-
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compilation, where it can become quite a nightmare...
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Some cross-toolchains exist on the internet, and can be used for general
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development, but they have a number of limitations:
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  - they can be general purpose, in that they are configured for the majority:
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    no optimisation for your specific target,
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  - they can be prepared for a specific target and thus are not easy to use,
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    nor optimised for, or even supporting your target,
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  - they often are using aging components (compiler, C library, etc...) not
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    supporting special features of your shiny new processor;
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On the other side, these toolchain offer some advantages:
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  - they are ready to use and quite easy to install and setup,
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  - they are proven if used by a wide community.
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But once you want to get all the juice out of your specific hardware, you will
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want to build your own toolchain. This is where crosstool-NG comes into play.
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There are also a number of tools that build toolchains for specific needs,
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which are not really scalable. Examples are:
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  - buildroot (buildroot.uclibc.org) whose main purpose is to build root file
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    systems, hence the name. But once you have your toolchain with buildroot,
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    part of it is installed in the root-to-be, so if you want to build a whole
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    new root, you either have to save the existing one as a template and
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    restore it later, or restart again from scratch. This is not convenient,
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  - ptxdist (www.pengutronix.de/software/ptxdist), whose purpose is very
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    similar to buildroot,
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  - other projects (openembedded.org for example), which are again used to
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    build root file systems.
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crosstool-NG is really targeted at building toolchains, and only toolchains.
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It is then up to you to use it the way you want.
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___________
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          /
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History  /
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________/
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crosstool was first 'conceived' by Dan Kegel, who offered it to the community
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as a set of scripts, a repository of patches, and some pre-configured, general
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purpose setup files to be used to configure crosstool. This is available at
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http://www.kegel.com/crosstool, and the subversion repository is hosted on
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google at http://code.google.com/p/crosstool/.
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I once managed to add support for uClibc-based toolchains, but it did not make
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into mainline, mostly because I didn't have time to port the patch forward to
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the new versions, due in part to the big effort it was taking.
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So I decided to clean up crosstool in the state it was, re-order the things
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in place, add appropriate support for what I needed, that is uClibc support
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and a menu-driven configuration, named the new implementation crosstool-NG,
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(standing for crosstool Next Generation, as many other comunity projects do,
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and as a wink at the TV series "Star Trek: The Next Generation" ;-) ) and
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made it available to the community, in case it was of interest to any one.
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_____________________________
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                            /
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Referring to crosstool-NG  /
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__________________________/
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The long name of the project is crosstool-NG:
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  * no leading uppercase (except as first word in a sentence)
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  * crosstool and NG separated with a hyphen (dash)
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  * NG in uppercase
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Crosstool-NG can also be referred to by its short name CT-NG:
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  * all in uppercase
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  * CT and NG separated with a hyphen (dash)
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The long name is preferred over the short name, except in mail subjects, where
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the short name is a better fit.
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When referring to a specific version of crosstool-NG, append the version number
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either as:
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  * crosstool-NG X.Y.Z
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    - the long name, a space, and the version string
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  * crosstool-ng-X.Y.Z
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    - the long name in lowercase, a hyphen (dash), and the version string
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    - this is used to name the release tarballs
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  * crosstool-ng-X.Y.Z+hg_id
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    - the long name in lowercase, a hyphen, the version string, and the Hg id
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      (as returned by: ct-ng version)
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    - this is used to differentiate between releases and snapshots
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The frontend to crosstool-NG is the command ct-ng:
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  * all in lowercase
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  * ct and ng separated by a hyphen (dash)
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___________________________
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                          /
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Installing crosstool-NG  /
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________________________/
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There are two ways you can use crosstool-NG:
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 - build and install it, then get rid of the sources like you'd do for most
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   programs,
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 - or only build it and run from the source directory.
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The former should be used if you got crosstool-NG from a packaged tarball, see
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"Install method", below, while the latter is most useful for developpers that
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use a clone of the repository, and want to submit patches, see "The Hacker's
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way", below.
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Install method |
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---------------+
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If you go for the install, then you just follow the classical, but yet easy
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./configure way:
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  ./configure --prefix=/some/place
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  make
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  make install
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  export PATH="${PATH}:/some/place/bin"
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You can then get rid of crosstool-NG source. Next create a directory to serve
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as a working place, cd in there and run:
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  ct-ng help
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See below for complete usage.
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The Hacker's way |
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-----------------+
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If you go the hacker's way, then the usage is a bit different, although very
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simple:
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  ./configure --local
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  make
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Now, *do not* remove crosstool-NG sources. They are needed to run crosstool-NG!
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Stay in the directory holding the sources, and run:
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  ./ct-ng help
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See below for complete usage.
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Now, provided you used a clone of the repository, you can send me your changes.
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See the section titled CONTRIBUTING, below, for how to submit changees.
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Preparing for packaging |
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------------------------+
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If you plan on packaging crosstool-NG, you surely don't want to install it
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in your root file system. The install procedure of crosstool-NG honors the
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DESTDIR variable:
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  ./configure --prefix=/usr
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  make
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  make DESTDIR=/packaging/place install
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Shell completion |
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-----------------+
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crosstool-NG comes with a shell script fragment that defines bash-compatible
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completion. That shell fragment is currently not installed automatically, but
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this is planned.
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To install the shell script fragment, you have two options:
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 - install system-wide, most probably by copying ct-ng.comp into
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   /etc/bash_completion.d/
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 - install for a single user, by copying ct-ng.comp into ${HOME}/ and
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   sourcing this file from your ${HOME}/.bashrc
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Contributed code |
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-----------------+
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Some people contibuted code that couldn't get merged for various reasons. This
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code is available as lzma-compressed patches, in the contrib/ sub-directory.
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These patches are to be applied to the source of crosstool-NG, prior to
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installing, using something like the following:
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  lzcat contrib/foobar.patch.lzma |patch -p1
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There is no guarantee that a particuliar contribution applies to the current
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version of crosstool-ng, or that it will work at all. Use contributions at
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your own risk.
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____________________________
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                           /
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Configuring crosstool-NG  /
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_________________________/
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crosstool-NG is configured with a configurator presenting a menu-stuctured set
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of options. These options let you specify the way you want your toolchain
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built, where you want it installed, what architecture and specific processor it
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will support, the version of the components you want to use, etc... The
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value for those options are then stored in a configuration file.
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The configurator works the same way you configure your Linux kernel. It is
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assumed you now how to handle this.
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To enter the menu, type:
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  ct-ng menuconfig
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Almost every config item has a help entry. Read them carefully.
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String and number options can refer to environment variables. In such a case,
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you must use the shell syntax: ${VAR}. You shall neither single- nor double-
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quote the string/number options.
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There are three environment variables that are computed by crosstool-NG, and
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that you can use:
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CT_TARGET:
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  It represents the target tuple you are building for. You can use it for
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  example in the installation/prefix directory, such as:
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    /opt/x-tools/${CT_TARGET}
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CT_TOP_DIR:
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  The top directory where crosstool-NG is running. You shouldn't need it in
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  most cases. There is one case where you may need it: if you have local
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  patches and you store them in your running directory, you can refer to them
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  by using CT_TOP_DIR, such as:
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    ${CT_TOP_DIR}/patches.myproject
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CT_VERSION:
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  The version of crosstool-NG you are using. Not much use for you, but it's
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  there if you need it.
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Interesting config options |
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---------------------------+
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CT_LOCAL_TARBALLS_DIR:
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  If you already have some tarballs in a direcotry, enter it here. That will
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  speed up the retrieving phase, where crosstool-NG would otherwise download
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  those tarballs.
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CT_PREFIX_DIR:
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  This is where the toolchain will be installed in (and for now, where it
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  will run from). Common use is to add the target tuple in the directory
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  path, such as (see above):
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    /opt/x-tools/${CT_TARGET}
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CT_TARGET_VENDOR:
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  An identifier for your toolchain, will take place in the vendor part of the
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  target tuple. It shall *not* contain spaces or dashes. Usually, keep it
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  to a one-word string, or use underscores to separate words if you need.
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  Avoid dots, commas, and special characters.
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CT_TARGET_ALIAS:
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  An alias for the toolchian. It will be used as a prefix to the toolchain
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  tools. For example, you will have ${CT_TARGET_ALIAS}-gcc
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Also, if you think you don't see enough versions, you can try to enable one of
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those:
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CT_OBSOLETE:
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  Show obsolete versions or tools. Most of the time, you don't want to base
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  your toolchain on too old a version (of gcc, for example). But at times, it
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  can come handy to use such an old version for regression tests. Those old
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  versions are hidden behind CT_OBSOLETE. Those versions (or features) are so
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  marked because maintaining support for those in crosstool-NG would be too
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  costly, time-wise, and time is dear.
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CT_EXPERIMENTAL:
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  Show experimental versions or tools. Again, you might not want to base your
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  toolchain on too recent tools (eg. gcc) for production. But if you need a
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  feature present only in a recent version, or a new tool, you can find them
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  hidden behind CT_EXPERIMENTAL. Those versions (or features) did not (yet)
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  receive thorough testing in crosstool-NG, and/or are not mature enough to
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  be blindly trusted.
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Re-building an existing toolchain |
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----------------------------------+
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If you have an existing toolchain, you can re-use the options used to build it
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to create a new toolchain. That needs a very little bit of effort on your side
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but is quite easy. The options to build a toolchain are saved with the
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toolchain, and you can retrieve this configuration by running:
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  ${CT_TARGET}-ct-ng.config
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An alternate method is to extract the configuration from a build.log file.
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This will be necessary if your toolchain was build with crosstool-NG prior
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to 1.4.0, but can be used with build.log files from any version:
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  ct-ng extractconfig <build.log >.config
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Or, if your build.log file is compressed (most probably!):
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  bzcat build.log.bz2 |ct-ng extractconfig >.config
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The above commands will dump the configuration to stdout, so to rebuild a
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toolchain with this configuration, just redirect the output to the
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.config file:
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  ${CT_TARGET}-ct-ng.config >.config
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  ct-ng oldconfig
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Then, you can review and change the configuration by running:
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  ct-ng menuconfig
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Using as a backend for a build-system |
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--------------------------------------+
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Crosstool-NG can be used as a backend for an automated build-system. In this
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case, some components that are expected to run on the target (eg. the native
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gdb, ltrace, DUMA...) are not available in the menuconfig, and they are not
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build either, as it is considered the responsibility of the build-system to
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build its own versions of those tools.
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If you want to use crosstool-NG as a backend to generate your toolchains for
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your build-system, you have to set and export this environment variable:
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  CT_IS_A_BACKEND=y
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(case is not sensitive, you can say Y).
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________________________
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                       /
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Running crosstool-NG  /
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_____________________/
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To build the toolchain, simply type:
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  ct-ng build
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This will use the above configuration to retrieve, extract and patch the
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components, build, install and eventually test your newly built toolchain.
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You are then free to add the toolchain /bin directory in your PATH to use
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it at will.
yann@1
   383
yann@135
   384
In any case, you can get some terse help. Just type:
yann@192
   385
  ct-ng help
yann@203
   386
or:
yann@203
   387
  man 1 ct-ng
yann@135
   388
rpjday@436
   389
Stopping and restarting a build |
yann@476
   390
--------------------------------+
yann@135
   391
yann@135
   392
If you want to stop the build after a step you are debugging, you can pass the
yann@135
   393
variable STOP to make:
fr@1643
   394
  ct-ng build STOP=some_step
yann@135
   395
yann@135
   396
Conversely, if you want to restart a build at a specific step you are
yann@135
   397
debugging, you can pass the RESTART variable to make:
fr@1643
   398
  ct-ng build RESTART=some_step
yann@135
   399
yann@136
   400
Alternatively, you can call make with the name of a step to just do that step:
yann@192
   401
  ct-ng libc_headers
yann@136
   402
is equivalent to:
fr@1643
   403
  ct-ng build RESTART=libc_headers STOP=libc_headers
yann@136
   404
yann@304
   405
The shortcuts +step_name and step_name+ allow to respectively stop or restart
yann@136
   406
at that step. Thus:
fr@1643
   407
  ct-ng +libc_headers              and:    ct-ng libc_headers+
yann@136
   408
are equivalent to:
fr@1643
   409
  ct-ng build STOP=libc_headers    and:    ct-ng build RESTART=libc_headers
yann@136
   410
yann@181
   411
To obtain the list of acceptable steps, please call:
yann@544
   412
  ct-ng list-steps
yann@181
   413
yann@168
   414
Note that in order to restart a build, you'll have to say 'Y' to the config
yann@168
   415
option CT_DEBUG_CT_SAVE_STEPS, and that the previous build effectively went
yann@168
   416
that far.
yann@92
   417
yann@1025
   418
Building all toolchains at once |
yann@1025
   419
--------------------------------+
yann@92
   420
yann@1025
   421
You can build all samples; simply call:
yann@1025
   422
  ct-ng build-all
yann@40
   423
yann@335
   424
Overriding the number of // jobs |
yann@476
   425
---------------------------------+
yann@335
   426
yann@335
   427
If you want to override the number of jobs to run in // (the -j option to
yann@335
   428
make), you can either re-enter the menuconfig, or simply add it on the command
yann@335
   429
line, as such:
yann@335
   430
  ct-ng build.4
yann@335
   431
yann@335
   432
which tells crosstool-NG to override the number of // jobs to 4.
yann@335
   433
yann@335
   434
You can see the actions that support overriding the number of // jobs in
yann@335
   435
the help menu. Those are the ones with [.#] after them (eg. build[.#] or
yann@1025
   436
build-all[.#], and so on...).
yann@1025
   437
yann@1025
   438
Note on // jobs |
yann@1025
   439
----------------+
yann@1025
   440
yann@1025
   441
The crosstool-NG script 'ct-ng' is a Makefile-script. It does *not* execute
yann@1025
   442
in parallel (there is not much to gain). When speaking of // jobs, we are
yann@1025
   443
refering to the number of // jobs when making the *components*. That is, we
yann@1025
   444
speak of the number of // jobs used to build gcc, glibc, and so on...
yann@1025
   445
yann@1493
   446
Tools wrapper |
yann@1493
   447
--------------+
yann@1493
   448
yann@1493
   449
Starting with gcc-4.3 come two new dependencies: GMP and MPFR. With gcc-4.4,
yann@1493
   450
come three new ones: GMP, PPL and CLooG/ppl. These are libraries that enable
yann@1493
   451
advanced features to gcc. Additionally, some of the libraries can be used by
yann@1493
   452
binutils and gdb. Unfortunately, not all systems on which crosstool-NG runs
yann@1493
   453
have all of those libraries. And for those that do, the versions of those
yann@1493
   454
libraries may be older than the version required by gcc.
yann@1493
   455
yann@1493
   456
This is why crosstool-NG builds its own set of libraries as part of the
yann@1493
   457
toolchain.
yann@1493
   458
yann@1493
   459
The libraries are built as shared libraries, because building them as static
yann@1493
   460
libraries has some short-comings. This poses no problem at build time, as
yann@1513
   461
crosstool-NG correctly points gcc (and binutils and gdb) to the correct
yann@1493
   462
place where our own version of the libraries are installed. But it poses
yann@1493
   463
a problem when gcc et al. are run: the place where the libraries are is most
yann@1493
   464
probably not known to the host dynamic linker. Still worse, if the host system
yann@1493
   465
has its own versions, then ld.so would load the wrong library!
yann@1493
   466
yann@1493
   467
So we have to force the dynamic linker to load the correct version. We do this
yann@1493
   468
by using the LD_LIBRARY_PATH variable, that informs the dynamic linker where
yann@1493
   469
to look for shared libraries prior to searching its standard places. But we
yann@1493
   470
can't impose that burden on all the system (because it'd be a nightmare to
yann@1513
   471
configure, and because two toolchains on the same system may use different
yann@1493
   472
versions of the libraries); so we have to do it on a per-toolchain basis.
yann@1493
   473
yann@1493
   474
So we rename all binaries of the toolchain (by adding a dot '.' as their first
yann@1493
   475
character), and add a small program, the so-called "tools wrapper", that
yann@1493
   476
correctly sets LD_LIBRARY_PATH prior to running the real tool.
yann@1493
   477
yann@1493
   478
First, the wrapper was written as a POSIX-compliant shell script. That shell
yann@1493
   479
script is very simple, if not trivial, and works great. The only drawback is
yann@1493
   480
that it does not work on host systems that lack a shell, for example the
yann@1493
   481
MingW32 environment. To solve the issue, the wrapper has been re-written in C,
yann@1493
   482
and compiled at build time. This C wrapper is much more complex than the shell
yann@1493
   483
script, and although it sems to be working, it's been only lightly tested.
yann@1493
   484
Some of the expected short-comings with this C wrapper are;
yann@1493
   485
 - multi-byte file names may not be handled correctly
yann@1493
   486
 - it's really big for what it does
yann@1493
   487
yann@1493
   488
So, the default wrapper installed with your toolchain is the shell script.
yann@1493
   489
If you know that your system is missing a shell, then you shall use the C
yann@1493
   490
wrapper (and report back whether it works, or does not work, for you).
yann@1493
   491
yann@335
   492
yann@227
   493
_______________________
yann@227
   494
                      /
yann@227
   495
Using the toolchain  /
yann@227
   496
____________________/
yann@227
   497
yann@227
   498
Using the toolchain is as simple as adding the toolchain's bin directory in
yann@227
   499
your PATH, such as:
yann@227
   500
  export PATH="${PATH}:/your/toolchain/path/bin"
yann@227
   501
yann@335
   502
and then using the target tuple to tell the build systems to use your
yann@227
   503
toolchain:
yann@335
   504
  ./configure --target=your-target-tuple
yann@294
   505
or
yann@335
   506
  make CC=your-target-tuple-gcc
yann@294
   507
or
yann@335
   508
  make CROSS_COMPILE=your-target-tuple-
yann@294
   509
and so on...
yann@227
   510
yann@476
   511
It is strongly advised not to use the toolchain sys-root directory as an
yann@620
   512
install directory for your programs/packages. If you do so, you will not be
yann@476
   513
able to use your toolchain for another project. It is even strongly advised
yann@476
   514
that your toolchain is chmod-ed to read-only once successfully build, so that
yann@620
   515
you don't go polluting your toolchain with your programs/packages' files.
yann@476
   516
yann@476
   517
Thus, when you build a program/package, install it in a separate directory,
yann@476
   518
eg. /your/root. This directory is the /image/ of what would be in the root file
yann@620
   519
system of your target, and will contain all that your programs/packages have
yann@476
   520
installed.
yann@476
   521
Yann@1405
   522
The 'populate' script |
Yann@1405
   523
----------------------+
Yann@1405
   524
yann@227
   525
When your root directory is ready, it is still missing some important bits: the
yann@227
   526
toolchain's libraries. To populate your root directory with those libs, just
yann@227
   527
run:
yann@335
   528
  your-target-tuple-populate -s /your/root -d /your/root-populated
yann@227
   529
yann@227
   530
This will copy /your/root into /your/root-populated, and put the needed and only
yann@227
   531
the needed libraries there. Thus you don't polute /your/root with any cruft that
yann@227
   532
would no longer be needed should you have to remove stuff. /your/root always
yann@227
   533
contains only those things you install in it.
yann@227
   534
yann@227
   535
You can then use /your/root-populated to build up your file system image, a
yann@227
   536
tarball, or to NFS-mount it from your target, or whatever you need.
yann@227
   537
Yann@1405
   538
The populate script accepts the following options:
yann@294
   539
Yann@1405
   540
 -s src_dir
Yann@1405
   541
    Use 'src_dir' as the un-populated root directory.
yann@294
   542
Yann@1405
   543
 -d dst_dir
Yann@1405
   544
    Put the populated root directory in 'dst_dir'.
Yann@1405
   545
Yann@1405
   546
 -l lib1 [...]
Yann@1405
   547
    Always add specified libraries.
Yann@1405
   548
Yann@1405
   549
 -L file
Yann@1405
   550
    Always add libraries listed in 'file'.
yann@294
   551
yann@294
   552
 -f
Yann@1405
   553
    Remove 'dst_dir' if it previously existed; continue even if any library
Yann@1405
   554
    specified with -l or -L is missing.
yann@294
   555
yann@294
   556
 -v
yann@294
   557
    Be verbose, and tell what's going on (you can see exactly where libs are
yann@294
   558
    coming from).
yann@294
   559
yann@294
   560
 -h
Yann@1405
   561
    Print the help.
Yann@1405
   562
Yann@1405
   563
See 'your-target-tuple-populate -h' for more information on the options.
yann@294
   564
Yann@1406
   565
Here is how populate works:
Yann@1406
   566
Yann@1406
   567
  1) performs some sanity checks:
Yann@1406
   568
     - src_dir and dst_dir are specified
Yann@1406
   569
     - src_dir exists
Yann@1406
   570
     - unless forced, dst_dir does not exist
Yann@1406
   571
     - src_dir != dst_dir
Yann@1406
   572
Yann@1406
   573
  2) copy src_dir to dst_dir
Yann@1406
   574
Yann@1406
   575
  3) add forced libraries to dst_dir
Yann@1406
   576
     - build the list from -l and -L options
Yann@1406
   577
     - get forced libraries from the sysroot (see below for heuristics)
Yann@1406
   578
       - abort on the first missing library, unless -f is specified
Yann@1406
   579
Yann@1406
   580
  4) add all missing libraries to dst_dir
Yann@1406
   581
     - scan dst_dir for every ELF files that are 'executable' or
Yann@1406
   582
       'shared object'
Yann@1406
   583
     - list the "NEEDED Shared library" fields
Yann@1406
   584
       - check if the library is already in dst_dir/lib or dst_dir/usr/lib
Yann@1406
   585
       - if not, get the library from the sysroot
Yann@1406
   586
         - if it's in sysroot/lib, copy it to dst_dir/lib
Yann@1406
   587
         - if it's in sysroot/usr/lib, copy it to dst_dir/usr/lib
Yann@1406
   588
         - in both cases, use the SONAME of the library to create the file
Yann@1406
   589
           in dst_dir
Yann@1406
   590
         - if it was not found in the sysroot, this is an error.
Yann@1406
   591
yann@1580
   592
yann@40
   593
___________________
yann@40
   594
                  /
yann@40
   595
Toolchain types  /
yann@40
   596
________________/
yann@40
   597
yann@40
   598
There are four kinds of toolchains you could encounter.
yann@40
   599
yann@40
   600
First off, you must understand the following: when it comes to compilers there
yann@40
   601
are up to four machines involved:
yann@40
   602
  1) the machine configuring the toolchain components: the config machine
yann@40
   603
  2) the machine building the toolchain components:    the build machine
yann@40
   604
  3) the machine running the toolchain:                the host machine
yann@203
   605
  4) the machine the toolchain is generating code for: the target machine
yann@40
   606
yann@40
   607
We can most of the time assume that the config machine and the build machine
yann@40
   608
are the same. Most of the time, this will be true. The only time it isn't
yann@40
   609
is if you're using distributed compilation (such as distcc). Let's forget
yann@40
   610
this for the sake of simplicity.
yann@40
   611
yann@40
   612
So we're left with three machines:
yann@40
   613
 - build
yann@40
   614
 - host
yann@40
   615
 - target
yann@40
   616
yann@40
   617
Any toolchain will involve those three machines. You can be as pretty sure of
yann@40
   618
this as "2 and 2 are 4". Here is how they come into play:
yann@40
   619
yann@40
   620
1) build == host == target
yann@40
   621
    This is a plain native toolchain, targetting the exact same machine as the
yann@40
   622
    one it is built on, and running again on this exact same machine. You have
yann@40
   623
    to build such a toolchain when you want to use an updated component, such
yann@40
   624
    as a newer gcc for example.
yann@197
   625
    crosstool-NG calls it "native".
yann@40
   626
yann@40
   627
2) build == host != target
yann@40
   628
    This is a classic cross-toolchain, which is expected to be run on the same
yann@40
   629
    machine it is compiled on, and generate code to run on a second machine,
yann@40
   630
    the target.
yann@197
   631
    crosstool-NG calls it "cross".
yann@40
   632
yann@40
   633
3) build != host == target
yann@40
   634
    Such a toolchain is also a native toolchain, as it targets the same machine
yann@40
   635
    as it runs on. But it is build on another machine. You want such a
yann@40
   636
    toolchain when porting to a new architecture, or if the build machine is
yann@40
   637
    much faster than the host machine.
yann@197
   638
    crosstool-NG calls it "cross-native".
yann@40
   639
yann@40
   640
4) build != host != target
yann@92
   641
    This one is called a canadian-toolchain (*), and is tricky. The three
yann@40
   642
    machines in play are different. You might want such a toolchain if you
yann@40
   643
    have a fast build machine, but the users will use it on another machine,
yann@40
   644
    and will produce code to run on a third machine.
yann@197
   645
    crosstool-NG calls it "canadian".
yann@40
   646
yann@197
   647
crosstool-NG can build all these kinds of toolchains (or is aiming at it,
yann@197
   648
anyway!)
yann@40
   649
yann@40
   650
(*) The term Canadian Cross came about because at the time that these issues
yann@40
   651
    were all being hashed out, Canada had three national political parties.
yann@40
   652
    http://en.wikipedia.org/wiki/Cross_compiler
yann@40
   653
yann@1551
   654
yann@1575
   655
________________
yann@1575
   656
               /
yann@1575
   657
Contributing  /
yann@1575
   658
_____________/
yann@1575
   659
yann@1575
   660
Sending a bug report |
yann@1575
   661
---------------------+
yann@1575
   662
yann@1575
   663
If you need to send a bug report, please send a mail with subject
yann@1575
   664
prefixed with "[CT_NG]" with to following destinations:
yann@1575
   665
    TO: yann.morin.1998 (at) anciens.enib.fr
yann@1575
   666
    CC: crossgcc (at) sourceware.org
yann@1575
   667
yann@1575
   668
Sending patches |
yann@1575
   669
----------------+
yann@1575
   670
yann@1575
   671
If you want to enhance crosstool-NG, there's a to-do list in the TODO file.
yann@1575
   672
yann@1575
   673
Patches should come with the appropriate SoB line. A SoB line is typically
yann@1575
   674
something like:
yann@1575
   675
   Signed-off-by: John DOE <john.doe@somewhere.net>
yann@1575
   676
yann@1575
   677
The SoB line is clearly described in Documentation/SubmittingPatches , section
yann@1575
   678
12, of your favourite Linux kernel source tree.
yann@1575
   679
yann@1575
   680
Then you'll need to correctly configure Mercurial. There are two extensions
yann@1575
   681
that you may find usefull:
yann@1575
   682
  - mq        : http://mercurial.selenic.com/wiki/MqExtension
yann@1575
   683
  - patchbomb : http://mercurial.selenic.com/wiki/PatchbombExtension
yann@1575
   684
yann@1575
   685
Commit messages should look like (without leading pipes):
yann@1575
   686
 |component: short, one-line description
yann@1575
   687
 |
yann@1575
   688
 |optional longer description
yann@1575
   689
 |on multiple lines if needed
yann@1575
   690
yann@1575
   691
Here is an example commit message (see revision a53a5e1d61db):
yann@1575
   692
 |comp-libs/cloog: fix building
yann@1575
   693
 |
yann@1575
   694
 |For CLooG/PPL 0.15.3, the directory name was simply cloog-ppl.
yann@1575
   695
 |For any later versions, the directory name does have the version, such as
yann@1575
   696
 |cloog-ppl-0.15.4.
yann@1575
   697
yann@1575
   698
Here's a typical hacking session:
yann@1575
   699
  hg clone http://ymorin.is-a-geek.org/hg/crosstool-ng crosstool-ng
yann@1575
   700
  cd crosstool-ng
yann@1575
   701
  hg qinit
yann@1575
   702
  hg qnew -D -U -e my_first_patch
yann@1575
   703
  *edit patch description*
yann@1575
   704
  *hack* *hack* *check* *fails* *hack* *hack* *check* *works*
yann@1575
   705
  hg qref -D -e
yann@1575
   706
  *edit patch description, serving as commit message*
yann@1575
   707
  hg qnew -D -U -e my_second_patch
yann@1575
   708
  *edit patch description*
yann@1575
   709
  *hack* *hack* *check* *fails* *hack* *hack* *check* *works*
yann@1575
   710
  hg qref -D -e
yann@1575
   711
  *edit patch description, serving as commit message*
yann@1575
   712
  hg email --outgoing --intro   \
yann@1575
   713
           --from '"Your Full NAME" <your.email (at) your.domain>'   \
yann@1575
   714
           --to '"Yann E. MORIN" <yann.morin.1998 (at) anciens.enib.fr>'    \
yann@1575
   715
           --cc 'crossgcc (at) sourceware.org'
yann@1575
   716
  *edit introductory message*
yann@1575
   717
  *wait for feedback*
yann@1575
   718
  *re-send if no answer for a few days*
yann@1575
   719
yann@1575
   720
Note: replace '(at)' above with a plain '@'.
yann@1575
   721
yann@1575
   722
yann@1
   723
_____________
yann@1
   724
            /
yann@1
   725
Internals  /
yann@1
   726
__________/
yann@1
   727
yann@92
   728
Internally, crosstool-NG is script-based. To ease usage, the frontend is
yann@92
   729
Makefile-based.
yann@92
   730
yann@92
   731
Makefile front-end |
yann@476
   732
-------------------+
yann@92
   733
yann@203
   734
The entry point to crosstool-NG is the Makefile script "ct-ng". Calling this
yann@203
   735
script with an action will act exactly as if the Makefile was in the current
yann@203
   736
working directory and make was called with the action as rule. Thus:
yann@203
   737
  ct-ng menuconfig
yann@294
   738
yann@203
   739
is equivalent to having the Makefile in CWD, and calling:
yann@203
   740
  make menuconfig
yann@203
   741
yann@203
   742
Having ct-ng as it is avoids copying the Makefile everywhere, and acts as a
yann@203
   743
traditional command.
yann@203
   744
yann@203
   745
ct-ng loads sub- Makefiles from the library directory $(CT_LIB_DIR), as set up
yann@203
   746
at configuration time with ./configure.
yann@203
   747
yann@437
   748
ct-ng also searches for config files, sub-tools, samples, scripts and patches in
yann@203
   749
that library directory.
yann@92
   750
yann@294
   751
Because of a stupid make behavior/bug I was unable to track down, implicit make
yann@294
   752
rules are disabled: installing with --local would triger those rules, and mconf
yann@294
   753
was unbuildable.
yann@294
   754
yann@182
   755
Kconfig parser |
yann@476
   756
---------------+
yann@92
   757
yann@965
   758
The kconfig language is a hacked version, vampirised from the Linux kernel
yann@965
   759
(http://www.kernel.org/), and (heavily) adapted to my needs.
yann@92
   760
yann@1040
   761
The list of the most notable changes (at least the ones I remember) follows:
yann@1040
   762
- the CONFIG_ prefix has been replaced with CT_
yann@1040
   763
- a leading | in prompts is skipped, and subsequent leading spaces are not
yann@1040
   764
  trimmed
yann@1040
   765
- otherwise leading spaces are silently trimmed
yann@1040
   766
yann@203
   767
The kconfig parsers (conf and mconf) are not installed pre-built, but as
yann@203
   768
source files. Thus you can have the directory where crosstool-NG is installed,
yann@203
   769
exported (via NFS or whatever) and have clients with different architectures
yann@203
   770
use the same crosstool-NG installation, and most notably, the same set of
yann@203
   771
patches.
yann@203
   772
yann@381
   773
Architecture-specific |
yann@476
   774
----------------------+
yann@381
   775
yann@628
   776
Note: this chapter is not really well written, and might thus be a little bit
yann@628
   777
complex to understand. To get a better grasp of what an architecture is, the
yann@628
   778
reader is kindly encouraged to look at the "arch/" sub-directory, and to the
yann@628
   779
existing architectures to see how things are laid out.
yann@628
   780
yann@381
   781
An architecture is defined by:
yann@381
   782
yann@381
   783
 - a human-readable name, in lower case letters, with numbers as appropriate.
yann@628
   784
   The underscore is allowed; space and special characters are not.
yann@628
   785
     Eg.: arm, x86_64
yann@903
   786
 - a file in "config/arch/", named after the architecture's name, and suffixed
yann@903
   787
   with ".in".
yann@903
   788
     Eg.: config/arch/arm.in
yann@903
   789
 - a file in "scripts/build/arch/", named after the architecture's name, and
yann@903
   790
   suffixed with ".sh".
yann@903
   791
     Eg.: scripts/build/arch/arm.sh
yann@628
   792
yann@903
   793
The architecture's ".in" file API:
yann@628
   794
 > the config option "ARCH_%arch%" (where %arch% is to be replaced with the
yann@628
   795
   actual architecture name).
yann@628
   796
   That config option must have *neither* a type, *nor* a prompt! Also, it can
yann@628
   797
   *not* depend on any other config option (EXPERIMENTAL is managed as above).
yann@628
   798
     Eg.:
yann@628
   799
       config ARCH_arm
yann@630
   800
   + mandatory:
yann@702
   801
       defines a (terse) help entry for this architecture:
yann@630
   802
       Eg.:
yann@630
   803
         config ARCH_arm
yann@630
   804
           help
yann@630
   805
             The ARM architecture.
yann@628
   806
   + optional:
yann@628
   807
       selects adequate associated config options.
yann@1038
   808
       Note: 64-bit architectures *shall* select ARCH_64
yann@628
   809
       Eg.:
yann@628
   810
         config ARCH_arm
yann@628
   811
           select ARCH_SUPPORTS_BOTH_ENDIAN
yann@628
   812
           select ARCH_DEFAULT_LE
yann@630
   813
           help
yann@630
   814
             The ARM architecture.
yann@1038
   815
       Eg.:
yann@1038
   816
         config ARCH_x86_64
yann@1038
   817
            select ARCH_64
yann@1038
   818
            help
yann@1038
   819
              The x86_64 architecture.
yann@628
   820
yann@628
   821
 > other target-specific options, at your discretion. Note however that to
yann@628
   822
   avoid name-clashing, such options shall be prefixed with "ARCH_%arch%",
yann@628
   823
   where %arch% is again replaced by the actual architecture name.
yann@628
   824
   (Note: due to historical reasons, and lack of time to clean up the code,
yann@628
   825
    I may have left some config options that do not completely conform to
yann@628
   826
    this, as the architecture name was written all upper case. However, the
yann@628
   827
    prefix is unique among architectures, and does not cause harm).
yann@381
   828
yann@903
   829
The architecture's ".sh" file API:
yann@965
   830
 > the function "CT_DoArchTupleValues"
yann@381
   831
   + parameters: none
yann@381
   832
   + environment:
yann@901
   833
     - all variables from the ".config" file,
yann@901
   834
     - the two variables "target_endian_eb" and "target_endian_el" which are
yann@901
   835
       the endianness suffixes
yann@381
   836
   + return value: 0 upon success, !0 upon failure
yann@381
   837
   + provides:
yann@391
   838
     - mandatory
yann@383
   839
     - the environment variable CT_TARGET_ARCH
yann@389
   840
     - contains:
yann@389
   841
       the architecture part of the target tuple.
yann@389
   842
       Eg.: "armeb" for big endian ARM
yann@389
   843
            "i386" for an i386
yann@389
   844
   + provides:
yann@391
   845
     - optional
yann@389
   846
     - the environment variable CT_TARGET_SYS
yann@456
   847
     - contains:
yann@383
   848
       the sytem part of the target tuple.
yann@383
   849
       Eg.: "gnu" for glibc on most architectures
yann@383
   850
            "gnueabi" for glibc on an ARM EABI
yann@383
   851
     - defaults to:
yann@383
   852
       - for glibc-based toolchain: "gnu"
yann@383
   853
       - for uClibc-based toolchain: "uclibc"
yann@383
   854
   + provides:
yann@383
   855
     - optional
yann@767
   856
     - the environment variables to configure the cross-gcc (defaults)
yann@767
   857
       - CT_ARCH_WITH_ARCH    : the gcc ./configure switch to select architecture level         ( "--with-arch=${CT_ARCH_ARCH}"   )
yann@767
   858
       - CT_ARCH_WITH_ABI     : the gcc ./configure switch to select ABI level                  ( "--with-abi=${CT_ARCH_ABI}"     )
yann@767
   859
       - CT_ARCH_WITH_CPU     : the gcc ./configure switch to select CPU instruction set        ( "--with-cpu=${CT_ARCH_CPU}"     )
yann@767
   860
       - CT_ARCH_WITH_TUNE    : the gcc ./configure switch to select scheduling                 ( "--with-tune=${CT_ARCH_TUNE}"   )
yann@767
   861
       - CT_ARCH_WITH_FPU     : the gcc ./configure switch to select FPU type                   ( "--with-fpu=${CT_ARCH_FPU}"     )
yann@767
   862
       - CT_ARCH_WITH_FLOAT   : the gcc ./configure switch to select floating point arithmetics ( "--with-float=soft" or /empty/  )
yann@391
   863
   + provides:
yann@391
   864
     - optional
yann@767
   865
     - the environment variables to pass to the cross-gcc to build target binaries (defaults)
yann@391
   866
       - CT_ARCH_ARCH_CFLAG   : the gcc switch to select architecture level                     ( "-march=${CT_ARCH_ARCH}"            )
yann@456
   867
       - CT_ARCH_ABI_CFLAG    : the gcc switch to select ABI level                              ( "-mabi=${CT_ARCH_ABI}"              )
yann@391
   868
       - CT_ARCH_CPU_CFLAG    : the gcc switch to select CPU instruction set                    ( "-mcpu=${CT_ARCH_CPU}"              )
yann@391
   869
       - CT_ARCH_TUNE_CFLAG   : the gcc switch to select scheduling                             ( "-mtune=${CT_ARCH_TUNE}"            )
yann@391
   870
       - CT_ARCH_FPU_CFLAG    : the gcc switch to select FPU type                               ( "-mfpu=${CT_ARCH_FPU}"              )
yann@391
   871
       - CT_ARCH_FLOAT_CFLAG  : the gcc switch to choose floating point arithmetics             ( "-msoft-float" or /empty/           )
yann@391
   872
       - CT_ARCH_ENDIAN_CFLAG : the gcc switch to choose big or little endian                   ( "-mbig-endian" or "-mlittle-endian" )
yann@391
   873
     - default to:
yann@391
   874
       see above.
yann@767
   875
   + provides:
yann@767
   876
     - optional
yann@767
   877
     - the environement variables to configure the core and final compiler, specific to this architecture:
yann@767
   878
       - CT_ARCH_CC_CORE_EXTRA_CONFIG   : additional, architecture specific core gcc ./configure flags
yann@767
   879
       - CT_ARCH_CC_EXTRA_CONFIG        : additional, architecture specific final gcc ./configure flags
yann@767
   880
     - default to:
yann@767
   881
       - all empty
yann@767
   882
   + provides:
yann@767
   883
     - optional
yann@767
   884
     - the architecture-specific CFLAGS and LDFLAGS:
yann@767
   885
       - CT_ARCH_TARGET_CLFAGS
yann@767
   886
       - CT_ARCH_TARGET_LDFLAGS
yann@767
   887
     - default to:
yann@767
   888
       - all empty
yann@628
   889
yann@903
   890
You can have a look at "config/arch/arm.in" and "scripts/build/arch/arm.sh" for
yann@903
   891
a quite complete example of what an actual architecture description looks like.
yann@901
   892
yann@890
   893
Kernel specific |
yann@890
   894
----------------+
yann@890
   895
yann@890
   896
A kernel is defined by:
yann@890
   897
yann@890
   898
 - a human-readable name, in lower case letters, with numbers as appropriate.
yann@890
   899
   The underscore is allowed; space and special characters are not (although
yann@890
   900
   they are internally replaced with underscores.
yann@890
   901
     Eg.: linux, bare-metal
yann@890
   902
 - a file in "config/kernel/", named after the kernel name, and suffixed with
yann@890
   903
   ".in".
yann@890
   904
     Eg.: config/kernel/linux.in, config/kernel/bare-metal.in
yann@901
   905
 - a file in "scripts/build/kernel/", named after the kernel name, and suffixed
yann@901
   906
   with ".sh".
yann@901
   907
     Eg.: scripts/build/kernel/linux.sh, scripts/build/kernel/bare-metal.sh
yann@890
   908
yann@890
   909
The kernel's ".in" file must contain:
yann@890
   910
 > an optional lines containing exactly "# EXPERIMENTAL", starting on the
yann@890
   911
   first column, and without any following space or other character.
yann@890
   912
   If this line is present, then this kernel is considered EXPERIMENTAL,
yann@890
   913
   and correct dependency on EXPERIMENTAL will be set.
yann@901
   914
yann@890
   915
 > the config option "KERNEL_%kernel_name%" (where %kernel_name% is to be
yann@890
   916
   replaced with the actual kernel name, with all special characters and
yann@890
   917
   spaces replaced by underscores).
yann@890
   918
   That config option must have *neither* a type, *nor* a prompt! Also, it can
yann@890
   919
   *not* depends on EXPERIMENTAL.
yann@890
   920
     Eg.: KERNEL_linux, KERNEL_bare_metal
yann@890
   921
   + mandatory:
yann@890
   922
       defines a (terse) help entry for this kernel.
yann@890
   923
       Eg.:
yann@890
   924
         config KERNEL_bare_metal
yann@890
   925
           help
yann@890
   926
             Build a compiler for use without any kernel.
yann@890
   927
   + optional:
yann@890
   928
       selects adequate associated config options.
yann@890
   929
       Eg.:
yann@890
   930
         config KERNEL_bare_metal
yann@890
   931
           select BARE_METAL
yann@890
   932
           help
yann@890
   933
             Build a compiler for use without any kernel.
yann@890
   934
yann@890
   935
 > other kernel specific options, at your discretion. Note however that, to
yann@890
   936
   avoid name-clashing, such options should be prefixed with
yann@890
   937
   "KERNEL_%kernel_name%", where %kernel_name% is again tp be replaced with
yann@890
   938
   the actual kernel name.
yann@890
   939
   (Note: due to historical reasons, and lack of time to clean up the code,
yann@890
   940
    I may have left some config options that do not completely conform to
yann@890
   941
    this, as the kernel name was written all upper case. However, the prefix
yann@890
   942
    is unique among kernels, and does not cause harm).
yann@890
   943
yann@901
   944
The kernel's ".sh" file API:
yann@901
   945
 > is a bash script fragment
yann@901
   946
yann@965
   947
 > defines the function CT_DoKernelTupleValues
yann@965
   948
   + see the architecture's CT_DoArchTupleValues, except for:
yann@965
   949
   + set the environment variable CT_TARGET_KERNEL, the kernel part of the
yann@965
   950
     target tuple
yann@965
   951
   + return value: ignored
yann@965
   952
yann@901
   953
 > defines the function "do_kernel_get":
yann@901
   954
   + parameters: none
yann@901
   955
   + environment:
yann@901
   956
      - all variables from the ".config" file.
yann@901
   957
   + return value: 0 for success, !0 for failure.
yann@901
   958
   + behavior: download the kernel's sources, and store the tarball into
yann@901
   959
     "${CT_TARBALLS_DIR}". To this end, a functions is available, that
yann@901
   960
     abstracts downloading tarballs:
yann@901
   961
     - CT_DoGet <tarball_base_name> <URL1 [URL...]>
yann@901
   962
       Eg.: CT_DoGet linux-2.6.26.5 ftp://ftp.kernel.org/pub/linux/kernel/v2.6
yann@901
   963
     Note: retrieving sources from svn, cvs, git and the likes is not supported
yann@901
   964
     by CT_DoGet. You'll have to do this by hand, as it is done for eglibc in
yann@901
   965
     "scripts/build/libc/eglibc.sh"
yann@901
   966
yann@901
   967
 > defines the function "do_kernel_extract":
yann@901
   968
   + parameters: none
yann@901
   969
   + environment:
yann@901
   970
      - all variables from the ".config" file,
yann@901
   971
   + return value: 0 for success, !0 for failure.
yann@901
   972
   + behavior: extract the kernel's tarball into "${CT_SRC_DIR}", and apply
yann@901
   973
     required patches. To this end, a function is available, that abstracts
yann@901
   974
     extracting tarballs:
yann@901
   975
     - CT_ExtractAndPatch <tarball_base_name>
yann@901
   976
       Eg.: CT_ExtractAndPatch linux-2.6.26.5
yann@901
   977
yann@901
   978
 > defines the function "do_kernel_headers":
yann@901
   979
   + parameters: none
yann@901
   980
   + environment:
yann@901
   981
      - all variables from the ".config" file,
yann@901
   982
   + return value: 0 for success, !0 for failure.
yann@901
   983
   + behavior: install the kernel headers (if any) in "${CT_SYSROOT_DIR}/usr/include"
yann@901
   984
yann@901
   985
 > defines any kernel-specific helper functions
yann@901
   986
   These functions, if any, must be prefixed with "do_kernel_%CT_KERNEL%_",
yann@901
   987
   where '%CT_KERNEL%' is to be replaced with the actual kernel name, to avoid
yann@901
   988
   any name-clashing.
yann@901
   989
yann@901
   990
You can have a look at "config/kernel/linux.in" and "scripts/build/kernel/linux.sh"
yann@903
   991
as an example of what a complex kernel description looks like.
yann@901
   992
yann@620
   993
Adding a new version of a component |
yann@476
   994
------------------------------------+
yann@476
   995
yann@476
   996
When a new component, such as the Linux kernel, gcc or any other is released,
yann@476
   997
adding the new version to crosstool-NG is quite easy. There is a script that
yann@476
   998
will do all that for you:
yann@1095
   999
  scripts/addToolVersion.sh
yann@476
  1000
yann@476
  1001
Run it with no option to get some help.
yann@381
  1002
yann@203
  1003
Build scripts |
yann@476
  1004
--------------+
yann@203
  1005
yann@203
  1006
To Be Written later...