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diff --git a/docs/manual/external-toolchain.txt b/docs/manual/external-toolchain.txt new file mode 100644 index 000000000..20eebdb20 --- /dev/null +++ b/docs/manual/external-toolchain.txt @@ -0,0 +1,84 @@ +Using an external toolchain +=========================== + +Using an already existing toolchain is useful for different +reasons: + +* you already have a toolchain that is known to work for your specific + CPU + +* you want to speed up the Buildroot build process by skipping the + long toolchain build part + +* the toolchain generation feature of Buildroot is not sufficiently + flexible for you (for example if you need to generate a system with + 'glibc' instead of 'uClibc') + +Buildroot supports using existing toolchains through a mechanism +called 'external toolchain'. The external toolchain mechanism is +enabled in the +Toolchain+ menu, by selecting +External toolchain+ in ++Toolchain type+. + +Then, you have three solutions to use an external toolchain: + +* Use a predefined external toolchain profile, and let Buildroot + download, extract and install the toolchain. Buildroot already knows + about a few CodeSourcery toolchains for ARM, PowerPC, MIPS and + SuperH. Just select the toolchain profile in +Toolchain+ through the + available ones. This is definitely the easiest solution. + +* Use a predefined external toolchain profile, but instead of having + Buildroot download and extract the toolchain, you can tell Buildroot + where your toolchain is already installed on your system. Just + select the toolchain profile in +Toolchain+ through the available + ones, unselect +Download toolchain automatically+, and fill the + +Toolchain path+ text entry with the path to your cross-compiling + toolchain. + +* Use a completely custom external toolchain. This is particularly + useful for toolchains generated using crosstool-NG. To do this, + select the +Custom toolchain+ solution in the +Toolchain+ list. You + need to fill the +Toolchain path+, +Toolchain prefix+ and +External + toolchain C library+ options. Then, you have to tell Buildroot what + your external toolchain supports. If your external toolchain uses + the 'glibc' library, you only have to tell whether your toolchain + supports C++ or not. If your external toolchain uses the 'uclibc' + library, then you have to tell Buildroot if it supports largefile, + IPv6, RPC, wide-char, locale, program invocation, threads and + C++. At the beginning of the execution, Buildroot will tell you if + the selected options do not match the toolchain configuration. + + +Our external toolchain support has been tested with toolchains from +CodeSourcery, toolchains generated by +http://crosstool-ng.org[crosstool-NG], and toolchains generated by +Buildroot itself. In general, all toolchains that support the +'sysroot' feature should work. If not, do not hesitate to contact the +developers. + +We do not support toolchains from the +http://www.denx.de/wiki/DULG/ELDK[ELDK] of Denx, for two reasons: + +* The ELDK does not contain a pure toolchain (i.e just the compiler, + binutils, the C and C++ libraries), but a toolchain that comes with + a very large set of pre-compiled libraries and programs. Therefore, + Buildroot cannot import the 'sysroot' of the toolchain, as it would + contain hundreds of megabytes of pre-compiled libraries that are + normally built by Buildroot. + +* The ELDK toolchains have a completely non-standard custom mechanism + to handle multiple library variants. Instead of using the standard + GCC 'multilib' mechanism, the ARM ELDK uses different symbolic links + to the compiler to differentiate between library variants (for ARM + soft-float and ARM VFP), and the PowerPC ELDK compiler uses a + +CROSS_COMPILE+ environment variable. This non-standard behaviour + makes it difficult to support ELDK in Buildroot. + +We also do not support using the distribution toolchain (i.e the +gcc/binutils/C library installed by your distribution) as the +toolchain to build software for the target. This is because your +distribution toolchain is not a "pure" toolchain (i.e only with the +C/C++ library), so we cannot import it properly into the Buildroot +build environment. So even if you are building a system for a x86 or +x86_64 target, you have to generate a cross-compilation toolchain with +Buildroot or crosstool-NG. |