| .. SPDX-License-Identifier: CC-BY-SA-2.0-UK |
| |
| Optionally Using an External Toolchain |
| ************************************** |
| |
| You might want to use an external toolchain as part of your development. |
| If this is the case, the fundamental steps you need to accomplish are as |
| follows: |
| |
| - Understand where the installed toolchain resides. For cases where you |
| need to build the external toolchain, you would need to take separate |
| steps to build and install the toolchain. |
| |
| - Make sure you add the layer that contains the toolchain to your |
| ``bblayers.conf`` file through the |
| :term:`BBLAYERS` variable. |
| |
| - Set the :term:`EXTERNAL_TOOLCHAIN` variable in your ``local.conf`` file |
| to the location in which you installed the toolchain. |
| |
| The toolchain configuration is very flexible and customizable. It |
| is primarily controlled with the :term:`TCMODE` variable. This variable |
| controls which ``tcmode-*.inc`` file to include from the |
| ``meta/conf/distro/include`` directory within the :term:`Source Directory`. |
| |
| The default value of :term:`TCMODE` is "default", which tells the |
| OpenEmbedded build system to use its internally built toolchain (i.e. |
| ``tcmode-default.inc``). However, other patterns are accepted. In |
| particular, "external-\*" refers to external toolchains. One example is |
| the Mentor Graphics Sourcery G++ Toolchain. Support for this toolchain resides |
| in the separate ``meta-sourcery`` layer at |
| https://github.com/MentorEmbedded/meta-sourcery/. |
| See its ``README`` file for details about how to use this layer. |
| |
| Another example of external toolchain layer is |
| :yocto_git:`meta-arm-toolchain </meta-arm/tree/meta-arm-toolchain/>` |
| supporting GNU toolchains released by ARM. |
| |
| You can find further information by reading about the :term:`TCMODE` variable |
| in the Yocto Project Reference Manual's variable glossary. |