Toolchains...

I’m just wondering how difficult it would be to build RISC OS using an open source toolchain (ie., gcc, etc).

Obviously it would be necessary to write a preprocessor to convert assembler files from Acorn ASM syntax to GNU as syntax, and while not impossible, this would not be a trivial task. Presumably build scripts, makefiles, etc would need some work. But what other major difficulties could be expected?

Obviously it would be necessary to write a preprocessor to convert assembler files from Acorn ASM syntax to GNU as syntax, and while not impossible, this would not be a trivial task.

It’s not obvious to me, I’m afraid. I suggest that you investigate GCCSDK’s asasm, which comprehends (most) objasm syntax and is capable of interworking with both GCC 3 and 4. Certainly, with a (relatively small) amount of buildsystem hackery, it’s possible to cross-compile quite a few components. I see little reason why it can’t be used to build components natively on RISC OS, either (which would be simpler, given that far fewer buildsystem changes should be required).

Ah, I should have guessed someone had already thought of writing something to process Acorn-style ASM files. I’ll have a look. Thanks!

Edited to add: there is now a much more detailed thread on the same topic: https://www.riscosopen.org/forum/forums/5/topics/193