Using Miri first builds some crates

[RalfJung]

It looks like somehow Miri doesn't come with fully pre-built crates any more on the playground: when I open this code and run it in Miri, it starts doing this in the output:

   Compiling hyper v0.14.4
   Compiling hyper-tls v0.5.0
   Compiling reqwest v0.11.0

Most of the time, it then timeouts, probably because building the dependencies takes too long.

We have done some changes to cargo-miri in the recent past that fixed in particular the interaction with hyper (rust-lang/miri#1705), so maybe the cache needs to be cleared and re-built somehow? But I thought that was supposed to happen automatically.

[shepmaster]

Is this still the right setup to do before running the user code?

rustup component add rust-src miri
cargo miri setup
cargo miri run

[shepmaster]

CI appears to be precompiling those crates (click on "build and push container"):

#8 146.2    Compiling hyper v0.14.4
551
#8 146.7    Compiling cookie_store v0.12.0
552
#8 147.2    Compiling select v0.5.0
553
#8 147.5    Compiling postgres v0.19.0
554
#8 149.7    Compiling hyper-tls v0.5.0
555
#8 149.9    Compiling reqwest v0.11.0
556
#8 151.1    Compiling playground v0.0.1 (/playground)
557
#8 151.1     Finished dev [unoptimized + debuginfo] target(s) in 2m 30s
558
#8 151.1      Running `/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/cargo-miri target/x86_64-unknown-linux-gnu/debug/playground`
559
#8 151.2 Hello, world!

[RalfJung]

Is this still the right setup to do before running the user code?

Yeah, I would think so. However, it's possible that old files sticking around could confuse cargo-miri... does this process start with an empty target directory each time, or does it reuse the one from the previous day?

[shepmaster]

The intention (and everything I've seen previously) is that it's a completely clean build.

[RalfJung]

Yeah this is a Miri bug: rust-lang/miri#1722

[RalfJung]

Closing this then, bors is testing the fix for Miri now and eventually it should make its way through to the playground.

[shepmaster]

Thank you!