Requires mman.h? about compiler-rt.rs HOT 8 CLOSED

LLVM's compiler-rt doesn't really support the ARM Cortex-M architecture. This crate compiles all the intrinsics that don't fail to compile to that architecture regardless of whether the intrinsic is actually "used" (i.e. LLVM lowers some Rust code to that intrinsic). I'd be okay with removing this intrinsic (enable_execute_stack) if it doesn't compile on Debian but I'll add it back if we later find out that LLVM lowers some Rust code to that intrinsic.

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Well I wasn't sure if I even needed compiler-rt.rs, but your xargo example for building copper for an STM32 seemed to include it so I figured I'd add it.

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Well I wasn't sure if I even needed compiler-rt.rs

Nah, you can actually get quite far without it (unless you need to do floating point operations on a device without FPU like Cortex-M0 or Cortex-M0).

your xargo example for building copper for an STM32 seemed to include it so I figured I'd add it.

Did it? Which one? I'm sure the copper book examples don't use compiler-rt.rs -- all the example use target spec files with no-compilert-rt set to true.

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On the xargo README.

https://camo.githubusercontent.com/b9f45b5ed49d6970b512e9a985297873970e8e42/687474703a2f2f692e696d6775722e636f6d2f705549666e77752e6a7067

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Oh, that copper; I thought you mean the book. cu needs very little of compiler-rt.rs; I might rewrite the needed intrinsics in Rust so cu can drop its dependency on compiler-rt -- that would make building cu simpler.

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Well I wasn't sure if I even needed compiler-rt.rs

Having said that, I was working through porting Phil Oppermann's bump and heap allocators to my bare metal ARM project this evening and I found I needed __aeabi_memclr4 and __aeabi_memmove. I've diverted them to the rlibc equivalents for now but I think fixing this would be useful.

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This came about because RUST_TARGET_PATH wasn't set, so the build script couldn't actually see my target file, and so it didn't realise this was an os=none build.

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I found I needed __aeabi_memclr4 and __aeabi_memmove

I'm porting compiler-rt to Rust as part of rust-lang/rust#35437. My work so far is in this repo. I just started but the crate already provides these two symbols. If you want to switch to it, check japaric-archived/cu#37

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