🚀 Add ARM Cortex-M cross-compilation support and consolidate to LLVM 20 #19
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The answer I've been looking for is `--default-script` for lld. Without this, test_packages cannot build because a linker script isn't provided. We are in a hard place like we were with the ARM GNU Toolchain where we needed to supply a `.specs` for the libc to allow test_packages to link. We found that `--specs=nosys.specs` does the trick because it provides weak defaults which allow linking but can overridden by the addition of any other specification such as picolibc. I removed LLMV 19 because I got the following linker errors (repeated): ``` ld.lld: error: .conan2/p/b/llvm-08844596518f5/p/bin/../lib/clang-runtimes/arm-none-eabi/armv7m_soft_nofp_exn_rtti/lib/picolibcpp.ld:278: symbol not found: __end ld.lld: error: .conan2/p/b/llvm-08844596518f5/p/bin/../lib/clang-runtimes/arm-none-eabi/armv7m_soft_nofp_exn_rtti/lib/picolibcpp.ld:279: symbol not found: __stack ld.lld: error: .conan2/p/b/llvm-08844596518f5/p/bin/../lib/clang-runtimes/arm-none-eabi/armv7m_soft_nofp_exn_rtti/lib/picolibcpp.ld:278: symbol not found: __end ld.lld: error: .conan2/p/b/llvm-08844596518f5/p/bin/../lib/clang-runtimes/arm-none-eabi/armv7m_soft_nofp_exn_rtti/lib/picolibcpp.ld:279: symbol not found: __stack ld.lld: error: .conan2/p/b/llvm-08844596518f5/p/bin/../lib/clang-runtimes/arm-none-eabi/armv7m_soft_nofp_exn_rtti/lib/picolibcpp.ld:278: symbol not found: __end ld.lld: error: .conan2/p/b/llvm-08844596518f5/p/bin/../lib/clang-runtimes/arm-none-eabi/armv7m_soft_nofp_exn_rtti/lib/picolibcpp.ld:279: symbol not found: __stack ld.lld: error: .conan2/p/b/llvm-08844596518f5/p/bin/../lib/clang-runtimes/arm-none-eabi/armv7m_soft_nofp_exn_rtti/lib/picolibcpp.ld:278: symbol not found: __end ld.lld: error: .conan2/p/b/llvm-08844596518f5/p/bin/../lib/clang-runtimes/arm-none-eabi/armv7m_soft_nofp_exn_rtti/lib/picolibcpp.ld:279: symbol not found: __stack ``` I see no reason to support LLVM 19 if we need to work around these sorts of issues. No issues came from compiling 20.1.0 so we will start our toolchain versions from there and go upwards.
Rather than doing this, we will let the demo application automatically execute on build if not cross compiling.
I don't know why I didn't do this before. Conan only supports whole number variants of LLVM. So there is no need to keep the exact version for anything within 20. If they release a newer version then we can upgrade it. Users wanting the older revision can use the older revision number. This greatly reduces the number of versions we need to maintain into the future and makes developing with llvm a very easy task. Rather than complex versioning, we just have llvm-20 or llvm-X where X is the major version number.
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Resolves #22
This commit adds comprehensive support for ARM Cortex-M microcontrollers by
integrating the ARM LLVM Embedded Toolchain alongside the upstream LLVM
releases. The package now intelligently selects the appropriate toolchain
variant based on the target architecture.
Major changes:
m7f, m7d, m23, m33, m33f, m35p, m35pf, m55, m85)
targets and upstream LLVM for all other targets
arm-embedded)
Breaking changes:
Note: The upstream LLVM version (20.1.8) and ARM Embedded Toolchain version
(20.1.0) do not match exactly. Both are packaged under version "20" as they
are the most recent official releases from their respective sources at the
time of packaging.