Cargo env vars aren't set #1515

alecmocatta · 2020-08-16T19:07:49Z

Cargo's docs specify various env vars that are passed to binaries run with cargo run/test/bench. cargo miri does not currently pass them, so this fails under miri:

fn main() {
    println!("{}", std::env::var("CARGO_PKG_NAME").unwrap());
}

(Playground)

The text was updated successfully, but these errors were encountered:

bjorn3 · 2020-08-16T19:11:55Z

You need to pass -Zmiri-disable-isolation to miri. For example cargo miri run -- -Zmiri-disable-isolation. Otherwise things like env var access and filesystem access are disabled.

alecmocatta · 2020-08-16T19:17:24Z

Sorry, I thought I'd repro'd this with -Zmiri-disable-isolation but I was mistaken. Closing!

RalfJung · 2020-09-09T06:46:56Z

@alecmocatta Also you should be able to use env! I think, which is evaluated at build-time rather than at run-time. That's advisable anyway as it will mean that this works even if you distribute the binary and run it outside cargo. (For tests that seems unlikely, for the main binaries more likely.)

alecmocatta · 2020-09-09T09:53:00Z

Thanks @RalfJung! I bumped into this when I changed env::current_dir() to PathBuf::from(env::var_os("CARGO_MANIFEST_DIR").unwrap()) to workaround #1514. env! could plausibly be outdated whereas env::var_os is in theory guaranteed to be correct. Regardless, looking forward to removing once #1540 lands!

RalfJung · 2020-09-09T10:01:45Z

Not sure what you mean by "outdated"? With env! the file should be rebuilt if the env var changes (that used to not happen but was fixed recently I think).

alecmocatta · 2020-09-09T10:04:58Z

e.g. on moving the manifest directory, but now I think about it you're probably right that would trigger a rebuild on the next cargo test invocation.

alecmocatta · 2020-09-09T10:13:30Z

Actually I've just confirmed that moving the manifest directory does not trigger a rebuild, thus env! and env::var can disagree. This seems dubious behaviour to me, I'll file an issue rust-lang/rust.

alecmocatta · 2020-09-09T10:24:35Z

https://github.com/rust-lang/rust/issues/76511

Redo cargo-miri logic This rewrite the cargo-miri logic for running the requested crate(s) following what we outlined in #739: `cargo miri run/test $FLAGS` (almost) literally invokes `cargo run/test $FLAGS` but with some environment variables set so that we can control what happens: * `RUSTC_WRAPPER` is set so that we get invoked instead of `rustc`. We use that power to mess with the flags being used for the build (things to be interpreted by Miri use a different sysroot), and when we are detecting a binary crate meant to be run by Miri, we grab the info we care about and put it into a JSON file for later use. * `CARGO_TARGET_$TARGET_RUNNER` is set so what we get invoked when cargo wants to run a binary. At that point we take that JSON info from before and use it to invoke Miri. Overall this works great! We get all sorts of cargo magic for free, and do not even need `cargo-metadata` any more. There's one annoying point though, which I have not managed to entirely work around yet: this means we are doing a full build, not just a check-build. Given that our sysroot is MIR-only, I was surprised that this even worked, but still -- this means we are doing more work than we should. So I also added some patching of arguments to make sure `--emit` does not contain `link`, and then more patching was required of the `--extern` flags for the binary because those referenced the `.rlib` files but now only `.rmeta` exists, and that is still not fully working because cargo seems to expect those `.rmeta` files and now triggers a rebuild each time as those files are still missing. My current plan is to make our wrapper create some empty dummy files with the right names, but the amount of hacks we are stacking on top of each other here is getting worrysome.^^ `@ehuss` your input would be welcome on this issue. Due to re-using cargo more literally, this also changes flag parsing to match `cargo`. So `-Zmiri` flags now have to be passed via an environment variable (Cc #1416). This PR is not ready yet, but the parts that are there I think can be reviewed already. TODO: * [x] [Fix Windows](#1540 (comment)). * [x] Figure out how we can do check-only builds without the rebuild problem above. I am also worried about cases where `build.rs` script might detect check-only builds and then do less work; I think some crates in rustc are doing that and if this is a thing in the wider ecosystem we need to find a way to support this as well. * [x] Currently cargo runs doctests as well, and they are not run in Miri. We should at least figure out a way to not run them at all (resolving #584 is left for a future PR). * [x] For some time, detect the old way of passing `-Zmiri` flags and warn that this will need updating. For some simple situations we can probably make it still support the old way, but I plan to remove those hacks after a bit. This is just to give people and me time to go around and send PRs to all projects that use Miri on CI, and update their use of the flags. * [x] Add a test for stdin handling (#1505). This should work now but we should be sure. * [x] Add a test for cargo env vars (#1515). * [x] Check if #1516 is resolved. * [x] Check if #1001 and #1514 are resolved. * [x] Check if #1312 is resolved (not sure if it is wort adding a test). * [x] Check if #1512 is resolved (not sure if it is wort adding a test). Fixes #700. Fixes #739. Fixes #1001. Fixes #1312 (without a test, as we run without cargo's stdin/stdout wrapping now, as the test for stdin confirms). Fixes #1416. Fixes #1505. Fixes #1512 (without a test, as cargo now does all that handling anyway, which various other tests confirm). Fixes #1514. Fixes #1516. Cc `@alecmocatta` who reported many of the bugs above; would be great if you could help with the tests e.g. by providing some small examples I could try. r? `@oli-obk`

Redo cargo-miri logic This rewrite the cargo-miri logic for running the requested crate(s) following what we outlined in #739: `cargo miri run/test $FLAGS` (almost) literally invokes `cargo run/test $FLAGS` but with some environment variables set so that we can control what happens: * `RUSTC_WRAPPER` is set so that we get invoked instead of `rustc`. We use that power to mess with the flags being used for the build (things to be interpreted by Miri use a different sysroot), and when we are detecting a binary crate meant to be run by Miri, we grab the info we care about and put it into a JSON file for later use. * `CARGO_TARGET_$TARGET_RUNNER` is set so what we get invoked when cargo wants to run a binary. At that point we take that JSON info from before and use it to invoke Miri. Overall this works great! We get all sorts of cargo magic for free, and do not even need `cargo-metadata` any more. There's one annoying point though, which I have not managed to entirely work around yet: this means we are doing a full build, not just a check-build. Given that our sysroot is MIR-only, I was surprised that this even worked, but still -- this means we are doing more work than we should. So I also added some patching of arguments to make sure `--emit` does not contain `link`, and then more patching was required of the `--extern` flags for the binary because those referenced the `.rlib` files but now only `.rmeta` exists, and that is still not fully working because cargo seems to expect those `.rmeta` files and now triggers a rebuild each time as those files are still missing. My current plan is to make our wrapper create some empty dummy files with the right names, but the amount of hacks we are stacking on top of each other here is getting worrysome.^^ `@ehuss` your input would be welcome on this issue. Due to re-using cargo more literally, this also changes flag parsing to match `cargo`. So `-Zmiri` flags now have to be passed via an environment variable (Cc #1416). This PR is not ready yet, but the parts that are there I think can be reviewed already. TODO: * [x] [Fix Windows](#1540 (comment)). * [x] Figure out how we can do check-only builds without the rebuild problem above. ~~I am also worried about cases where `build.rs` script might detect check-only builds and then do less work; I think some crates in rustc are doing that and if this is a thing in the wider ecosystem we need to find a way to support this as well.~~ (postponed that until we have a concrete example) * [x] Currently cargo runs doctests as well, and they are not run in Miri. We should at least figure out a way to not run them at all (resolving #584 is left for a future PR). * [x] For some time, detect the old way of passing `-Zmiri` flags and warn that this will need updating. For some simple situations we can probably make it still support the old way, but I plan to remove those hacks after a bit. This is just to give people and me time to go around and send PRs to all projects that use Miri on CI, and update their use of the flags. * [x] Add a test for stdin handling (#1505). This should work now but we should be sure. * [x] Add a test for cargo env vars (#1515). * [x] Check if #1516 is resolved. * [x] Check if #1001 and #1514 are resolved. * [x] Check if #1312 is resolved (not sure if it is wort adding a test). * [x] Check if #1512 is resolved (not sure if it is wort adding a test). Fixes #700. Fixes #739. Fixes #1001. Fixes #1312 (without a test, as we run without cargo's stdin/stdout wrapping now, as the test for stdin confirms). Fixes #1416. Fixes #1505. Fixes #1512 (without a test, as cargo now does all that handling anyway, which various other tests confirm). Fixes #1514. Fixes #1516. Cc `@alecmocatta` who reported many of the bugs above; would be great if you could help with the tests e.g. by providing some small examples I could try. r? `@oli-obk`

alecmocatta closed this as completed Aug 16, 2020

RalfJung mentioned this issue Sep 8, 2020

Redo cargo-miri logic #1540

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Cargo env vars aren't set #1515

Cargo env vars aren't set #1515

alecmocatta commented Aug 16, 2020 •

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bjorn3 commented Aug 16, 2020 •

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alecmocatta commented Aug 16, 2020

RalfJung commented Sep 9, 2020

alecmocatta commented Sep 9, 2020

RalfJung commented Sep 9, 2020 •

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alecmocatta commented Sep 9, 2020

alecmocatta commented Sep 9, 2020

alecmocatta commented Sep 9, 2020

Cargo env vars aren't set #1515

Cargo env vars aren't set #1515

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alecmocatta commented Aug 16, 2020 • edited Loading

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alecmocatta commented Aug 16, 2020

RalfJung commented Sep 9, 2020

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alecmocatta commented Aug 16, 2020 •

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bjorn3 commented Aug 16, 2020 •

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