docs/overview.txt
author "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>
Fri Oct 02 22:10:38 2009 +0200 (2009-10-02)
changeset 1551 8c40b842e798
parent 1513 0a405ac9d9ce
child 1554 3b8df55987ae
permissions -rw-r--r--
libc/glibc: fix building for seemingly native toolchains

Build glibc with -O2 as a fix/workaround to building
seemingly-native toolchains.

See:
- docs/overview.txt
- docs/known-issues.txt
- http://sourceware.org/ml/crossgcc/2009-09/msg00055.html
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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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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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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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Toolchain types
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  Seemingly-native toolchains
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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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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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checked the code out from SVN, 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 checked-out the code, you can send me your interesting changes
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by running:
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  svn diff
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and mailing me the result! :-P
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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 patches in the contrib/ sub-directory. These patches are
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to be applied to the source of crosstool-NG, prior to installing.
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An easy way to use contributed code is to pass the --with-contrib= option to
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./configure. The possible values depend upon which contributions are packaged
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with your version, but you can get with it with passing one of those two
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special values:
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  --with-contrib=list
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    will list all available contributions
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  --with-contrib=all
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    will select all avalaible contributions
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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}-config
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This will dump the configuration to stdout, so to rebuild a toolchain with this
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configuration, the following is all you need to do:
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  ${CT_TARGET}-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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________________________
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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.
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In any case, you can get some terse help. Just type:
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  ct-ng help
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or:
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  man 1 ct-ng
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Stopping and restarting a build |
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--------------------------------+
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If you want to stop the build after a step you are debugging, you can pass the
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variable STOP to make:
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  ct-ng STOP=some_step
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Conversely, if you want to restart a build at a specific step you are
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debugging, you can pass the RESTART variable to make:
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  ct-ng RESTART=some_step
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Alternatively, you can call make with the name of a step to just do that step:
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  ct-ng libc_headers
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is equivalent to:
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  ct-ng RESTART=libc_headers STOP=libc_headers
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The shortcuts +step_name and step_name+ allow to respectively stop or restart
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at that step. Thus:
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  ct-ng +libc_headers        and:    ct-ng libc_headers+
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are equivalent to:
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  ct-ng STOP=libc_headers    and:    ct-ng RESTART=libc_headers
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To obtain the list of acceptable steps, please call:
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  ct-ng list-steps
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Note that in order to restart a build, you'll have to say 'Y' to the config
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option CT_DEBUG_CT_SAVE_STEPS, and that the previous build effectively went
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that far.
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Building all toolchains at once |
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--------------------------------+
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You can build all samples; simply call:
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  ct-ng build-all
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Overriding the number of // jobs |
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---------------------------------+
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If you want to override the number of jobs to run in // (the -j option to
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make), you can either re-enter the menuconfig, or simply add it on the command
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line, as such:
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  ct-ng build.4
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which tells crosstool-NG to override the number of // jobs to 4.
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You can see the actions that support overriding the number of // jobs in
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the help menu. Those are the ones with [.#] after them (eg. build[.#] or
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build-all[.#], and so on...).
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Note on // jobs |
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----------------+
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The crosstool-NG script 'ct-ng' is a Makefile-script. It does *not* execute
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in parallel (there is not much to gain). When speaking of // jobs, we are
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refering to the number of // jobs when making the *components*. That is, we
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speak of the number of // jobs used to build gcc, glibc, and so on...
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Tools wrapper |
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--------------+
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Starting with gcc-4.3 come two new dependencies: GMP and MPFR. With gcc-4.4,
yann@1493
   391
come three new ones: GMP, PPL and CLooG/ppl. These are libraries that enable
yann@1493
   392
advanced features to gcc. Additionally, some of the libraries can be used by
yann@1493
   393
binutils and gdb. Unfortunately, not all systems on which crosstool-NG runs
yann@1493
   394
have all of those libraries. And for those that do, the versions of those
yann@1493
   395
libraries may be older than the version required by gcc.
yann@1493
   396
yann@1493
   397
This is why crosstool-NG builds its own set of libraries as part of the
yann@1493
   398
toolchain.
yann@1493
   399
yann@1493
   400
The libraries are built as shared libraries, because building them as static
yann@1493
   401
libraries has some short-comings. This poses no problem at build time, as
yann@1513
   402
crosstool-NG correctly points gcc (and binutils and gdb) to the correct
yann@1493
   403
place where our own version of the libraries are installed. But it poses
yann@1493
   404
a problem when gcc et al. are run: the place where the libraries are is most
yann@1493
   405
probably not known to the host dynamic linker. Still worse, if the host system
yann@1493
   406
has its own versions, then ld.so would load the wrong library!
yann@1493
   407
yann@1493
   408
So we have to force the dynamic linker to load the correct version. We do this
yann@1493
   409
by using the LD_LIBRARY_PATH variable, that informs the dynamic linker where
yann@1493
   410
to look for shared libraries prior to searching its standard places. But we
yann@1493
   411
can't impose that burden on all the system (because it'd be a nightmare to
yann@1513
   412
configure, and because two toolchains on the same system may use different
yann@1493
   413
versions of the libraries); so we have to do it on a per-toolchain basis.
yann@1493
   414
yann@1493
   415
So we rename all binaries of the toolchain (by adding a dot '.' as their first
yann@1493
   416
character), and add a small program, the so-called "tools wrapper", that
yann@1493
   417
correctly sets LD_LIBRARY_PATH prior to running the real tool.
yann@1493
   418
yann@1493
   419
First, the wrapper was written as a POSIX-compliant shell script. That shell
yann@1493
   420
script is very simple, if not trivial, and works great. The only drawback is
yann@1493
   421
that it does not work on host systems that lack a shell, for example the
yann@1493
   422
MingW32 environment. To solve the issue, the wrapper has been re-written in C,
yann@1493
   423
and compiled at build time. This C wrapper is much more complex than the shell
yann@1493
   424
script, and although it sems to be working, it's been only lightly tested.
yann@1493
   425
Some of the expected short-comings with this C wrapper are;
yann@1493
   426
 - multi-byte file names may not be handled correctly
yann@1493
   427
 - it's really big for what it does
yann@1493
   428
yann@1493
   429
So, the default wrapper installed with your toolchain is the shell script.
yann@1493
   430
If you know that your system is missing a shell, then you shall use the C
yann@1493
   431
wrapper (and report back whether it works, or does not work, for you).
yann@1493
   432
yann@335
   433
yann@227
   434
_______________________
yann@227
   435
                      /
yann@227
   436
Using the toolchain  /
yann@227
   437
____________________/
yann@227
   438
yann@227
   439
Using the toolchain is as simple as adding the toolchain's bin directory in
yann@227
   440
your PATH, such as:
yann@227
   441
  export PATH="${PATH}:/your/toolchain/path/bin"
yann@227
   442
yann@335
   443
and then using the target tuple to tell the build systems to use your
yann@227
   444
toolchain:
yann@335
   445
  ./configure --target=your-target-tuple
yann@294
   446
or
yann@335
   447
  make CC=your-target-tuple-gcc
yann@294
   448
or
yann@335
   449
  make CROSS_COMPILE=your-target-tuple-
yann@294
   450
and so on...
yann@227
   451
yann@476
   452
It is strongly advised not to use the toolchain sys-root directory as an
yann@620
   453
install directory for your programs/packages. If you do so, you will not be
yann@476
   454
able to use your toolchain for another project. It is even strongly advised
yann@476
   455
that your toolchain is chmod-ed to read-only once successfully build, so that
yann@620
   456
you don't go polluting your toolchain with your programs/packages' files.
yann@476
   457
yann@476
   458
Thus, when you build a program/package, install it in a separate directory,
yann@476
   459
eg. /your/root. This directory is the /image/ of what would be in the root file
yann@620
   460
system of your target, and will contain all that your programs/packages have
yann@476
   461
installed.
yann@476
   462
Yann@1405
   463
The 'populate' script |
Yann@1405
   464
----------------------+
Yann@1405
   465
yann@227
   466
When your root directory is ready, it is still missing some important bits: the
yann@227
   467
toolchain's libraries. To populate your root directory with those libs, just
yann@227
   468
run:
yann@335
   469
  your-target-tuple-populate -s /your/root -d /your/root-populated
yann@227
   470
yann@227
   471
This will copy /your/root into /your/root-populated, and put the needed and only
yann@227
   472
the needed libraries there. Thus you don't polute /your/root with any cruft that
yann@227
   473
would no longer be needed should you have to remove stuff. /your/root always
yann@227
   474
contains only those things you install in it.
yann@227
   475
yann@227
   476
You can then use /your/root-populated to build up your file system image, a
yann@227
   477
tarball, or to NFS-mount it from your target, or whatever you need.
yann@227
   478
Yann@1405
   479
The populate script accepts the following options:
yann@294
   480
Yann@1405
   481
 -s src_dir
Yann@1405
   482
    Use 'src_dir' as the un-populated root directory.
yann@294
   483
Yann@1405
   484
 -d dst_dir
Yann@1405
   485
    Put the populated root directory in 'dst_dir'.
Yann@1405
   486
Yann@1405
   487
 -l lib1 [...]
Yann@1405
   488
    Always add specified libraries.
Yann@1405
   489
Yann@1405
   490
 -L file
Yann@1405
   491
    Always add libraries listed in 'file'.
yann@294
   492
yann@294
   493
 -f
Yann@1405
   494
    Remove 'dst_dir' if it previously existed; continue even if any library
Yann@1405
   495
    specified with -l or -L is missing.
yann@294
   496
yann@294
   497
 -v
yann@294
   498
    Be verbose, and tell what's going on (you can see exactly where libs are
yann@294
   499
    coming from).
yann@294
   500
yann@294
   501
 -h
Yann@1405
   502
    Print the help.
Yann@1405
   503
Yann@1405
   504
See 'your-target-tuple-populate -h' for more information on the options.
yann@294
   505
Yann@1406
   506
Here is how populate works:
Yann@1406
   507
Yann@1406
   508
  1) performs some sanity checks:
Yann@1406
   509
     - src_dir and dst_dir are specified
Yann@1406
   510
     - src_dir exists
Yann@1406
   511
     - unless forced, dst_dir does not exist
Yann@1406
   512
     - src_dir != dst_dir
Yann@1406
   513
Yann@1406
   514
  2) copy src_dir to dst_dir
Yann@1406
   515
Yann@1406
   516
  3) add forced libraries to dst_dir
Yann@1406
   517
     - build the list from -l and -L options
Yann@1406
   518
     - get forced libraries from the sysroot (see below for heuristics)
Yann@1406
   519
       - abort on the first missing library, unless -f is specified
Yann@1406
   520
Yann@1406
   521
  4) add all missing libraries to dst_dir
Yann@1406
   522
     - scan dst_dir for every ELF files that are 'executable' or
Yann@1406
   523
       'shared object'
Yann@1406
   524
     - list the "NEEDED Shared library" fields
Yann@1406
   525
       - check if the library is already in dst_dir/lib or dst_dir/usr/lib
Yann@1406
   526
       - if not, get the library from the sysroot
Yann@1406
   527
         - if it's in sysroot/lib, copy it to dst_dir/lib
Yann@1406
   528
         - if it's in sysroot/usr/lib, copy it to dst_dir/usr/lib
Yann@1406
   529
         - in both cases, use the SONAME of the library to create the file
Yann@1406
   530
           in dst_dir
Yann@1406
   531
         - if it was not found in the sysroot, this is an error.
Yann@1406
   532
yann@40
   533
___________________
yann@40
   534
                  /
yann@40
   535
Toolchain types  /
yann@40
   536
________________/
yann@40
   537
yann@40
   538
There are four kinds of toolchains you could encounter.
yann@40
   539
yann@40
   540
First off, you must understand the following: when it comes to compilers there
yann@40
   541
are up to four machines involved:
yann@40
   542
  1) the machine configuring the toolchain components: the config machine
yann@40
   543
  2) the machine building the toolchain components:    the build machine
yann@40
   544
  3) the machine running the toolchain:                the host machine
yann@203
   545
  4) the machine the toolchain is generating code for: the target machine
yann@40
   546
yann@40
   547
We can most of the time assume that the config machine and the build machine
yann@40
   548
are the same. Most of the time, this will be true. The only time it isn't
yann@40
   549
is if you're using distributed compilation (such as distcc). Let's forget
yann@40
   550
this for the sake of simplicity.
yann@40
   551
yann@40
   552
So we're left with three machines:
yann@40
   553
 - build
yann@40
   554
 - host
yann@40
   555
 - target
yann@40
   556
yann@40
   557
Any toolchain will involve those three machines. You can be as pretty sure of
yann@40
   558
this as "2 and 2 are 4". Here is how they come into play:
yann@40
   559
yann@40
   560
1) build == host == target
yann@40
   561
    This is a plain native toolchain, targetting the exact same machine as the
yann@40
   562
    one it is built on, and running again on this exact same machine. You have
yann@40
   563
    to build such a toolchain when you want to use an updated component, such
yann@40
   564
    as a newer gcc for example.
yann@197
   565
    crosstool-NG calls it "native".
yann@40
   566
yann@40
   567
2) build == host != target
yann@40
   568
    This is a classic cross-toolchain, which is expected to be run on the same
yann@40
   569
    machine it is compiled on, and generate code to run on a second machine,
yann@40
   570
    the target.
yann@197
   571
    crosstool-NG calls it "cross".
yann@40
   572
yann@40
   573
3) build != host == target
yann@40
   574
    Such a toolchain is also a native toolchain, as it targets the same machine
yann@40
   575
    as it runs on. But it is build on another machine. You want such a
yann@40
   576
    toolchain when porting to a new architecture, or if the build machine is
yann@40
   577
    much faster than the host machine.
yann@197
   578
    crosstool-NG calls it "cross-native".
yann@40
   579
yann@40
   580
4) build != host != target
yann@92
   581
    This one is called a canadian-toolchain (*), and is tricky. The three
yann@40
   582
    machines in play are different. You might want such a toolchain if you
yann@40
   583
    have a fast build machine, but the users will use it on another machine,
yann@40
   584
    and will produce code to run on a third machine.
yann@197
   585
    crosstool-NG calls it "canadian".
yann@40
   586
yann@197
   587
crosstool-NG can build all these kinds of toolchains (or is aiming at it,
yann@197
   588
anyway!)
yann@40
   589
yann@40
   590
(*) The term Canadian Cross came about because at the time that these issues
yann@40
   591
    were all being hashed out, Canada had three national political parties.
yann@40
   592
    http://en.wikipedia.org/wiki/Cross_compiler
yann@40
   593
yann@1551
   594
Seemingly-native toolchains |
yann@1551
   595
----------------------------+
yann@1551
   596
yann@1551
   597
Seemingly-native toolchains are toolchains that target the same architecture
yann@1551
   598
as the one it is built on, and on which it will run, but the machine tuple
yann@1551
   599
may be different (eg i686 vs. i386, or x86_64-unknown-linux-gnu vs.
yann@1551
   600
x86_64-pc-linux-gnu). This also applies if the target architecture is of the
yann@1551
   601
same kind (eg. x86 vs. x86_64, or ppc vs. ppc64).
yann@1551
   602
yann@1551
   603
Such toolchain is tricky to build, as the configure scripts may incorrectly
yann@1551
   604
assume that files (headers and libs) from the build (or host) machine can be
yann@1551
   605
used by the cross-compiler it is going to build. The problem seems to arise
yann@1551
   606
only with glibc (and eglibc?) starting with version 2.7.
yann@1551
   607
yann@1551
   608
yann@1
   609
_____________
yann@1
   610
            /
yann@1
   611
Internals  /
yann@1
   612
__________/
yann@1
   613
yann@92
   614
Internally, crosstool-NG is script-based. To ease usage, the frontend is
yann@92
   615
Makefile-based.
yann@92
   616
yann@92
   617
Makefile front-end |
yann@476
   618
-------------------+
yann@92
   619
yann@203
   620
The entry point to crosstool-NG is the Makefile script "ct-ng". Calling this
yann@203
   621
script with an action will act exactly as if the Makefile was in the current
yann@203
   622
working directory and make was called with the action as rule. Thus:
yann@203
   623
  ct-ng menuconfig
yann@294
   624
yann@203
   625
is equivalent to having the Makefile in CWD, and calling:
yann@203
   626
  make menuconfig
yann@203
   627
yann@203
   628
Having ct-ng as it is avoids copying the Makefile everywhere, and acts as a
yann@203
   629
traditional command.
yann@203
   630
yann@203
   631
ct-ng loads sub- Makefiles from the library directory $(CT_LIB_DIR), as set up
yann@203
   632
at configuration time with ./configure.
yann@203
   633
yann@437
   634
ct-ng also searches for config files, sub-tools, samples, scripts and patches in
yann@203
   635
that library directory.
yann@92
   636
yann@294
   637
Because of a stupid make behavior/bug I was unable to track down, implicit make
yann@294
   638
rules are disabled: installing with --local would triger those rules, and mconf
yann@294
   639
was unbuildable.
yann@294
   640
yann@182
   641
Kconfig parser |
yann@476
   642
---------------+
yann@92
   643
yann@965
   644
The kconfig language is a hacked version, vampirised from the Linux kernel
yann@965
   645
(http://www.kernel.org/), and (heavily) adapted to my needs.
yann@92
   646
yann@1040
   647
The list of the most notable changes (at least the ones I remember) follows:
yann@1040
   648
- the CONFIG_ prefix has been replaced with CT_
yann@1040
   649
- a leading | in prompts is skipped, and subsequent leading spaces are not
yann@1040
   650
  trimmed
yann@1040
   651
- otherwise leading spaces are silently trimmed
yann@1040
   652
yann@203
   653
The kconfig parsers (conf and mconf) are not installed pre-built, but as
yann@203
   654
source files. Thus you can have the directory where crosstool-NG is installed,
yann@203
   655
exported (via NFS or whatever) and have clients with different architectures
yann@203
   656
use the same crosstool-NG installation, and most notably, the same set of
yann@203
   657
patches.
yann@203
   658
yann@381
   659
Architecture-specific |
yann@476
   660
----------------------+
yann@381
   661
yann@628
   662
Note: this chapter is not really well written, and might thus be a little bit
yann@628
   663
complex to understand. To get a better grasp of what an architecture is, the
yann@628
   664
reader is kindly encouraged to look at the "arch/" sub-directory, and to the
yann@628
   665
existing architectures to see how things are laid out.
yann@628
   666
yann@381
   667
An architecture is defined by:
yann@381
   668
yann@381
   669
 - a human-readable name, in lower case letters, with numbers as appropriate.
yann@628
   670
   The underscore is allowed; space and special characters are not.
yann@628
   671
     Eg.: arm, x86_64
yann@903
   672
 - a file in "config/arch/", named after the architecture's name, and suffixed
yann@903
   673
   with ".in".
yann@903
   674
     Eg.: config/arch/arm.in
yann@903
   675
 - a file in "scripts/build/arch/", named after the architecture's name, and
yann@903
   676
   suffixed with ".sh".
yann@903
   677
     Eg.: scripts/build/arch/arm.sh
yann@628
   678
yann@903
   679
The architecture's ".in" file API:
yann@628
   680
 > the config option "ARCH_%arch%" (where %arch% is to be replaced with the
yann@628
   681
   actual architecture name).
yann@628
   682
   That config option must have *neither* a type, *nor* a prompt! Also, it can
yann@628
   683
   *not* depend on any other config option (EXPERIMENTAL is managed as above).
yann@628
   684
     Eg.:
yann@628
   685
       config ARCH_arm
yann@630
   686
   + mandatory:
yann@702
   687
       defines a (terse) help entry for this architecture:
yann@630
   688
       Eg.:
yann@630
   689
         config ARCH_arm
yann@630
   690
           help
yann@630
   691
             The ARM architecture.
yann@628
   692
   + optional:
yann@628
   693
       selects adequate associated config options.
yann@1038
   694
       Note: 64-bit architectures *shall* select ARCH_64
yann@628
   695
       Eg.:
yann@628
   696
         config ARCH_arm
yann@628
   697
           select ARCH_SUPPORTS_BOTH_ENDIAN
yann@628
   698
           select ARCH_DEFAULT_LE
yann@630
   699
           help
yann@630
   700
             The ARM architecture.
yann@1038
   701
       Eg.:
yann@1038
   702
         config ARCH_x86_64
yann@1038
   703
            select ARCH_64
yann@1038
   704
            help
yann@1038
   705
              The x86_64 architecture.
yann@628
   706
yann@628
   707
 > other target-specific options, at your discretion. Note however that to
yann@628
   708
   avoid name-clashing, such options shall be prefixed with "ARCH_%arch%",
yann@628
   709
   where %arch% is again replaced by the actual architecture name.
yann@628
   710
   (Note: due to historical reasons, and lack of time to clean up the code,
yann@628
   711
    I may have left some config options that do not completely conform to
yann@628
   712
    this, as the architecture name was written all upper case. However, the
yann@628
   713
    prefix is unique among architectures, and does not cause harm).
yann@381
   714
yann@903
   715
The architecture's ".sh" file API:
yann@965
   716
 > the function "CT_DoArchTupleValues"
yann@381
   717
   + parameters: none
yann@381
   718
   + environment:
yann@901
   719
     - all variables from the ".config" file,
yann@901
   720
     - the two variables "target_endian_eb" and "target_endian_el" which are
yann@901
   721
       the endianness suffixes
yann@381
   722
   + return value: 0 upon success, !0 upon failure
yann@381
   723
   + provides:
yann@391
   724
     - mandatory
yann@383
   725
     - the environment variable CT_TARGET_ARCH
yann@389
   726
     - contains:
yann@389
   727
       the architecture part of the target tuple.
yann@389
   728
       Eg.: "armeb" for big endian ARM
yann@389
   729
            "i386" for an i386
yann@389
   730
   + provides:
yann@391
   731
     - optional
yann@389
   732
     - the environment variable CT_TARGET_SYS
yann@456
   733
     - contains:
yann@383
   734
       the sytem part of the target tuple.
yann@383
   735
       Eg.: "gnu" for glibc on most architectures
yann@383
   736
            "gnueabi" for glibc on an ARM EABI
yann@383
   737
     - defaults to:
yann@383
   738
       - for glibc-based toolchain: "gnu"
yann@383
   739
       - for uClibc-based toolchain: "uclibc"
yann@383
   740
   + provides:
yann@383
   741
     - optional
yann@391
   742
     - the environment variable CT_KERNEL_ARCH
yann@383
   743
     - contains:
yann@391
   744
       the architecture name as understandable by the Linux kernel build
yann@391
   745
       system.
yann@391
   746
       Eg.: "arm" for an ARM
yann@391
   747
            "powerpc" for a PowerPC
yann@391
   748
            "i386" for an x86
yann@383
   749
     - defaults to:
yann@391
   750
       ${CT_ARCH}
yann@391
   751
   + provides:
yann@391
   752
     - optional
yann@767
   753
     - the environment variables to configure the cross-gcc (defaults)
yann@767
   754
       - CT_ARCH_WITH_ARCH    : the gcc ./configure switch to select architecture level         ( "--with-arch=${CT_ARCH_ARCH}"   )
yann@767
   755
       - CT_ARCH_WITH_ABI     : the gcc ./configure switch to select ABI level                  ( "--with-abi=${CT_ARCH_ABI}"     )
yann@767
   756
       - CT_ARCH_WITH_CPU     : the gcc ./configure switch to select CPU instruction set        ( "--with-cpu=${CT_ARCH_CPU}"     )
yann@767
   757
       - CT_ARCH_WITH_TUNE    : the gcc ./configure switch to select scheduling                 ( "--with-tune=${CT_ARCH_TUNE}"   )
yann@767
   758
       - CT_ARCH_WITH_FPU     : the gcc ./configure switch to select FPU type                   ( "--with-fpu=${CT_ARCH_FPU}"     )
yann@767
   759
       - CT_ARCH_WITH_FLOAT   : the gcc ./configure switch to select floating point arithmetics ( "--with-float=soft" or /empty/  )
yann@391
   760
   + provides:
yann@391
   761
     - optional
yann@767
   762
     - the environment variables to pass to the cross-gcc to build target binaries (defaults)
yann@391
   763
       - CT_ARCH_ARCH_CFLAG   : the gcc switch to select architecture level                     ( "-march=${CT_ARCH_ARCH}"            )
yann@456
   764
       - CT_ARCH_ABI_CFLAG    : the gcc switch to select ABI level                              ( "-mabi=${CT_ARCH_ABI}"              )
yann@391
   765
       - CT_ARCH_CPU_CFLAG    : the gcc switch to select CPU instruction set                    ( "-mcpu=${CT_ARCH_CPU}"              )
yann@391
   766
       - CT_ARCH_TUNE_CFLAG   : the gcc switch to select scheduling                             ( "-mtune=${CT_ARCH_TUNE}"            )
yann@391
   767
       - CT_ARCH_FPU_CFLAG    : the gcc switch to select FPU type                               ( "-mfpu=${CT_ARCH_FPU}"              )
yann@391
   768
       - CT_ARCH_FLOAT_CFLAG  : the gcc switch to choose floating point arithmetics             ( "-msoft-float" or /empty/           )
yann@391
   769
       - CT_ARCH_ENDIAN_CFLAG : the gcc switch to choose big or little endian                   ( "-mbig-endian" or "-mlittle-endian" )
yann@391
   770
     - default to:
yann@391
   771
       see above.
yann@767
   772
   + provides:
yann@767
   773
     - optional
yann@767
   774
     - the environement variables to configure the core and final compiler, specific to this architecture:
yann@767
   775
       - CT_ARCH_CC_CORE_EXTRA_CONFIG   : additional, architecture specific core gcc ./configure flags
yann@767
   776
       - CT_ARCH_CC_EXTRA_CONFIG        : additional, architecture specific final gcc ./configure flags
yann@767
   777
     - default to:
yann@767
   778
       - all empty
yann@767
   779
   + provides:
yann@767
   780
     - optional
yann@767
   781
     - the architecture-specific CFLAGS and LDFLAGS:
yann@767
   782
       - CT_ARCH_TARGET_CLFAGS
yann@767
   783
       - CT_ARCH_TARGET_LDFLAGS
yann@767
   784
     - default to:
yann@767
   785
       - all empty
yann@628
   786
yann@903
   787
You can have a look at "config/arch/arm.in" and "scripts/build/arch/arm.sh" for
yann@903
   788
a quite complete example of what an actual architecture description looks like.
yann@901
   789
yann@890
   790
Kernel specific |
yann@890
   791
----------------+
yann@890
   792
yann@890
   793
A kernel is defined by:
yann@890
   794
yann@890
   795
 - a human-readable name, in lower case letters, with numbers as appropriate.
yann@890
   796
   The underscore is allowed; space and special characters are not (although
yann@890
   797
   they are internally replaced with underscores.
yann@890
   798
     Eg.: linux, bare-metal
yann@890
   799
 - a file in "config/kernel/", named after the kernel name, and suffixed with
yann@890
   800
   ".in".
yann@890
   801
     Eg.: config/kernel/linux.in, config/kernel/bare-metal.in
yann@901
   802
 - a file in "scripts/build/kernel/", named after the kernel name, and suffixed
yann@901
   803
   with ".sh".
yann@901
   804
     Eg.: scripts/build/kernel/linux.sh, scripts/build/kernel/bare-metal.sh
yann@890
   805
yann@890
   806
The kernel's ".in" file must contain:
yann@890
   807
 > an optional lines containing exactly "# EXPERIMENTAL", starting on the
yann@890
   808
   first column, and without any following space or other character.
yann@890
   809
   If this line is present, then this kernel is considered EXPERIMENTAL,
yann@890
   810
   and correct dependency on EXPERIMENTAL will be set.
yann@901
   811
yann@890
   812
 > the config option "KERNEL_%kernel_name%" (where %kernel_name% is to be
yann@890
   813
   replaced with the actual kernel name, with all special characters and
yann@890
   814
   spaces replaced by underscores).
yann@890
   815
   That config option must have *neither* a type, *nor* a prompt! Also, it can
yann@890
   816
   *not* depends on EXPERIMENTAL.
yann@890
   817
     Eg.: KERNEL_linux, KERNEL_bare_metal
yann@890
   818
   + mandatory:
yann@890
   819
       defines a (terse) help entry for this kernel.
yann@890
   820
       Eg.:
yann@890
   821
         config KERNEL_bare_metal
yann@890
   822
           help
yann@890
   823
             Build a compiler for use without any kernel.
yann@890
   824
   + optional:
yann@890
   825
       selects adequate associated config options.
yann@890
   826
       Eg.:
yann@890
   827
         config KERNEL_bare_metal
yann@890
   828
           select BARE_METAL
yann@890
   829
           help
yann@890
   830
             Build a compiler for use without any kernel.
yann@890
   831
yann@890
   832
 > other kernel specific options, at your discretion. Note however that, to
yann@890
   833
   avoid name-clashing, such options should be prefixed with
yann@890
   834
   "KERNEL_%kernel_name%", where %kernel_name% is again tp be replaced with
yann@890
   835
   the actual kernel name.
yann@890
   836
   (Note: due to historical reasons, and lack of time to clean up the code,
yann@890
   837
    I may have left some config options that do not completely conform to
yann@890
   838
    this, as the kernel name was written all upper case. However, the prefix
yann@890
   839
    is unique among kernels, and does not cause harm).
yann@890
   840
yann@901
   841
The kernel's ".sh" file API:
yann@901
   842
 > is a bash script fragment
yann@901
   843
yann@965
   844
 > defines the function CT_DoKernelTupleValues
yann@965
   845
   + see the architecture's CT_DoArchTupleValues, except for:
yann@965
   846
   + set the environment variable CT_TARGET_KERNEL, the kernel part of the
yann@965
   847
     target tuple
yann@965
   848
   + return value: ignored
yann@965
   849
yann@901
   850
 > defines the function "do_kernel_get":
yann@901
   851
   + parameters: none
yann@901
   852
   + environment:
yann@901
   853
      - all variables from the ".config" file.
yann@901
   854
   + return value: 0 for success, !0 for failure.
yann@901
   855
   + behavior: download the kernel's sources, and store the tarball into
yann@901
   856
     "${CT_TARBALLS_DIR}". To this end, a functions is available, that
yann@901
   857
     abstracts downloading tarballs:
yann@901
   858
     - CT_DoGet <tarball_base_name> <URL1 [URL...]>
yann@901
   859
       Eg.: CT_DoGet linux-2.6.26.5 ftp://ftp.kernel.org/pub/linux/kernel/v2.6
yann@901
   860
     Note: retrieving sources from svn, cvs, git and the likes is not supported
yann@901
   861
     by CT_DoGet. You'll have to do this by hand, as it is done for eglibc in
yann@901
   862
     "scripts/build/libc/eglibc.sh"
yann@901
   863
yann@901
   864
 > defines the function "do_kernel_extract":
yann@901
   865
   + parameters: none
yann@901
   866
   + environment:
yann@901
   867
      - all variables from the ".config" file,
yann@901
   868
   + return value: 0 for success, !0 for failure.
yann@901
   869
   + behavior: extract the kernel's tarball into "${CT_SRC_DIR}", and apply
yann@901
   870
     required patches. To this end, a function is available, that abstracts
yann@901
   871
     extracting tarballs:
yann@901
   872
     - CT_ExtractAndPatch <tarball_base_name>
yann@901
   873
       Eg.: CT_ExtractAndPatch linux-2.6.26.5
yann@901
   874
yann@901
   875
 > defines the function "do_kernel_headers":
yann@901
   876
   + parameters: none
yann@901
   877
   + environment:
yann@901
   878
      - all variables from the ".config" file,
yann@901
   879
   + return value: 0 for success, !0 for failure.
yann@901
   880
   + behavior: install the kernel headers (if any) in "${CT_SYSROOT_DIR}/usr/include"
yann@901
   881
yann@901
   882
 > defines any kernel-specific helper functions
yann@901
   883
   These functions, if any, must be prefixed with "do_kernel_%CT_KERNEL%_",
yann@901
   884
   where '%CT_KERNEL%' is to be replaced with the actual kernel name, to avoid
yann@901
   885
   any name-clashing.
yann@901
   886
yann@901
   887
You can have a look at "config/kernel/linux.in" and "scripts/build/kernel/linux.sh"
yann@903
   888
as an example of what a complex kernel description looks like.
yann@901
   889
yann@620
   890
Adding a new version of a component |
yann@476
   891
------------------------------------+
yann@476
   892
yann@476
   893
When a new component, such as the Linux kernel, gcc or any other is released,
yann@476
   894
adding the new version to crosstool-NG is quite easy. There is a script that
yann@476
   895
will do all that for you:
yann@1095
   896
  scripts/addToolVersion.sh
yann@476
   897
yann@476
   898
Run it with no option to get some help.
yann@381
   899
yann@203
   900
Build scripts |
yann@476
   901
--------------+
yann@203
   902
yann@203
   903
To Be Written later...