File.........: 3 - Configuring a toolchain.txt Copyright....: (C) 2010 Yann E. MORIN License......: Creative Commons Attribution Share Alike (CC-by-sa), v2.5 Configuring crosstool-NG / _________________________/ crosstool-NG is configured with a configurator presenting a menu-structured set of options. These options let you specify the way you want your toolchain built, where you want it installed, what architecture and specific processor it will support, the version of the components you want to use, etc... The value for those options are then stored in a configuration file. The configurator works the same way you configure your Linux kernel. It is assumed you know how to handle this. To enter the menu, type: ct-ng menuconfig Almost every config item has a help entry. Read them carefully. String and number options can refer to environment variables. In such a case, you must use the shell syntax: ${VAR}. You shall neither single- nor double- quote the string/number options. There are three environment variables that are computed by crosstool-NG, and that you can use: CT_TARGET: It represents the target tuple you are building for. You can use it for example in the installation/prefix directory, such as: /opt/x-tools/${CT_TARGET} CT_TOP_DIR: The top directory where crosstool-NG is running. You shouldn't need it in most cases. There is one case where you may need it: if you have local patches and you store them in your running directory, you can refer to them by using CT_TOP_DIR, such as: ${CT_TOP_DIR}/patches.myproject CT_VERSION: The version of crosstool-NG you are using. Not much use for you, but it's there if you need it. Interesting config options | ---------------------------+ CT_LOCAL_TARBALLS_DIR: If you already have some tarballs in a directory, enter it here. That will speed up the retrieving phase, where crosstool-NG would otherwise download those tarballs. CT_PREFIX_DIR: This is where the toolchain will be installed in (and for now, where it will run from). Common use is to add the target tuple in the directory path, such as (see above): /opt/x-tools/${CT_TARGET} CT_TARGET_VENDOR: An identifier for your toolchain, will take place in the vendor part of the target tuple. It shall *not* contain spaces or dashes. Usually, keep it to a one-word string, or use underscores to separate words if you need. Avoid dots, commas, and special characters. CT_TARGET_ALIAS: An alias for the toolchain. It will be used as a prefix to the toolchain tools. For example, you will have ${CT_TARGET_ALIAS}-gcc Also, if you think you don't see enough versions, you can try to enable one of those: CT_OBSOLETE: Show obsolete versions or tools. Most of the time, you don't want to base your toolchain on too old a version (of gcc, for example). But at times, it can come handy to use such an old version for regression tests. Those old versions are hidden behind CT_OBSOLETE. Those versions (or features) are so marked because maintaining support for those in crosstool-NG would be too costly, time-wise, and time is dear. CT_EXPERIMENTAL: Show experimental versions or tools. Again, you might not want to base your toolchain on too recent tools (eg. gcc) for production. But if you need a feature present only in a recent version, or a new tool, you can find them hidden behind CT_EXPERIMENTAL. Those versions (or features) did not (yet) receive thorough testing in crosstool-NG, and/or are not mature enough to be blindly trusted. Re-building an existing toolchain | ----------------------------------+ If you have an existing toolchain, you can re-use the options used to build it to create a new toolchain. That needs a very little bit of effort on your side but is quite easy. The options to build a toolchain are saved with the toolchain, and you can retrieve this configuration by running: ${CT_TARGET}-ct-ng.config An alternate method is to extract the configuration from a build.log file. This will be necessary if your toolchain was build with crosstool-NG prior to 1.4.0, but can be used with build.log files from any version: ct-ng extractconfig .config Or, if your build.log file is compressed (most probably!): bzcat build.log.bz2 |ct-ng extractconfig >.config The above commands will dump the configuration to stdout, so to rebuild a toolchain with this configuration, just redirect the output to the .config file: ${CT_TARGET}-ct-ng.config >.config ct-ng oldconfig Then, you can review and change the configuration by running: ct-ng menuconfig Using as a backend for a build-system | --------------------------------------+ Crosstool-NG can be used as a backend for an automated build-system. In this case, some components that are expected to run on the target (eg. the native gdb, ltrace, DUMA...) are not available in the menuconfig, and they are not build either, as it is considered the responsibility of the build-system to build its own versions of those tools. If you want to use crosstool-NG as a backend to generate your toolchains for your build-system, you have to set and export this environment variable: CT_IS_A_BACKEND=y (case is not sensitive, you can say Y).