cargo build fails on Raspberry Pi3B. "Unsupported target architecture" for sha2-asm.

[dantrevino]

Mainly for visibility. Not a bug in blockstack-core.

We ran into this while trying to build on Raspberry Pi.

error: failed to run custom build command for `sha2-asm v0.5.3`

Caused by:
  process didn't exit successfully: `/home/pi/blockstack-core/target/debug/build/sha2-asm-a58e6c6d2b010656/build-script-build` (exit code: 101)
--- stderr
thread 'main' panicked at 'Unsupported target architecture', /home/pi/.cargo/registry/src/github.com-1ecc6299db9ec823/sha2-asm-0.5.3/build.rs:13:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace.

warning: build failed, waiting for other jobs to finish...
error: build failed

[jcnelson]

Thanks @dantrevino. I think the fix here is going to be making it so Cargo uses sha2-asm when the architecture is supported, and plain-old sha2 otherwise. Not a Cargo wiz, so I need to figure out how to do this.

[dantrevino]

My understanding is that there is no way, currently, to dynamically include/exclude architecture-dependent features. It looks like rust-lang is tracking a fix for this in their nightly branch but implementation timeline seems indeterminate. #7914.

In the meantime, I've been able to consistently get working binaries for ARMv7 by removing the 'asm' feature and cross-compiling via cross. I've documented the steps here: https://gitlab.com/riot.ai/stacks-blockchain-rpi/-/blob/master/README-Cross.md

Simply removing the 'asm' feature and trying to build directly on Pi has not worked for me yet. I'm still working on testing different hardware variations.

[dantrevino]

Just following up ... building directly on a Pi3B fails consistently with either unable to allocate memory, or over-heating. Confirmed by myself and @fluidvoice that build normally hits 2GB-ish of memory usage. Typical failure looks like:

memory allocation of 75497472 bytes failed
error: could not compile `blockstack-core`.

[dantrevino]

Confirm stacks blockchain builds and runs fine on a Pi 4B with >= 2GB of RAM, with removal of "asm" from sha2 features.

[fluidvoice]

Confirm stacks blockchain builds and runs fine on a Pi 4B with >= 2GB of RAM, with removal of "asm" from sha2 features.

So how do I get around this compile problem? I have Ubuntu 19.10.1 running fine on my Pi4 now.

[dantrevino]

Sorry it's not spelled out clearly. As @jcnelson mentions above you have to remove the 'asm' feature from Cargo.toml and use plain old sha2. Until a better workaround can be submitted as a PR here, I'm maintaining an up-to-date mirror with the change in my gitlab repo mentioned above.

[fluidvoice]

Sorry it's not spelled out clearly. As @jcnelson mentions above you have to remove the 'asm' feature from Cargo.toml and use plain old sha2. Until a better workaround can be submitted as a PR here, I'm maintaining an up-to-date mirror with the change in my gitlab repo mentioned above.

ah ok. I've never used Rust before so needed to find what explicitly to do, namely commenting out this line. The build completed OK now on my Pi 4B 4GB RAM on Ubuntu 19.10.1 Mate DE.

[dependencies.sha2]
version = "0.8.0"
# features = ["asm"]