Cannot list environment variables

[shepmaster]

Cargo.toml

[package]
name = "repro"
version = "0.1.0"
authors = ["An Devloper <an.devloper@example.com>"]
edition = "2018"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]

src/main.rs

fn main() {
    std::env::vars_os();
}

Execution

$ cargo +nightly-2019-05-27 run
   Compiling repro v0.1.0 (/private/tmp/repro)
    Finished dev [unoptimized + debuginfo] target(s) in 0.25s
     Running `target/debug/repro`

$ cargo +nightly-2019-05-27 miri
   Compiling repro v0.1.0 (/private/tmp/repro)
error[E0080]: Miri evaluation error: can't call foreign function: _NSGetEnviron
   --> /Users/shep/.rustup/toolchains/nightly-2019-05-27-x86_64-apple-darwin/lib/rustlib/src/rust/src/libstd/sys/unix/os.rs:405:5
    |
405 |     _NSGetEnviron()
    |     ^^^^^^^^^^^^^^^ Miri evaluation error: can't call foreign function: _NSGetEnviron
    |
    = note: inside call to `std::sys::unix::os::environ` at /Users/shep/.rustup/toolchains/nightly-2019-05-27-x86_64-apple-darwin/lib/rustlib/src/rust/src/libstd/sys/unix/os.rs:426:28
    = note: inside call to `std::sys::unix::os::env` at /Users/shep/.rustup/toolchains/nightly-2019-05-27-x86_64-apple-darwin/lib/rustlib/src/rust/src/libstd/env.rs:143:21
note: inside call to `std::env::vars_os` at src/main.rs:2:5
   --> src/main.rs:2:5
    |
2   |     std::env::vars_os();
    |     ^^^^^^^^^^^^^^^^^^^
    = note: inside call to `main` at /Users/shep/.rustup/toolchains/nightly-2019-05-27-x86_64-apple-darwin/lib/rustlib/src/rust/src/libstd/rt.rs:64:34
    = note: inside call to closure at /Users/shep/.rustup/toolchains/nightly-2019-05-27-x86_64-apple-darwin/lib/rustlib/src/rust/src/libstd/rt.rs:52:53
    = note: inside call to closure at /Users/shep/.rustup/toolchains/nightly-2019-05-27-x86_64-apple-darwin/lib/rustlib/src/rust/src/libstd/panicking.rs:293:40
    = note: inside call to `std::panicking::try::do_call::<[closure@DefId(1:5938 ~ std[29d7]::rt[0]::lang_start_internal[0]::{{closure}}[0]) 0:&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe], i32>` at /Users/shep/.rustup/toolchains/nightly-2019-05-27-x86_64-apple-darwin/lib/rustlib/src/rust/src/libstd/panicking.rs:289:5
    = note: inside call to `std::panicking::try::<i32, [closure@DefId(1:5938 ~ std[29d7]::rt[0]::lang_start_internal[0]::{{closure}}[0]) 0:&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe]>` at /Users/shep/.rustup/toolchains/nightly-2019-05-27-x86_64-apple-darwin/lib/rustlib/src/rust/src/libstd/panic.rs:388:9
    = note: inside call to `std::panic::catch_unwind::<[closure@DefId(1:5938 ~ std[29d7]::rt[0]::lang_start_internal[0]::{{closure}}[0]) 0:&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe], i32>` at /Users/shep/.rustup/toolchains/nightly-2019-05-27-x86_64-apple-darwin/lib/rustlib/src/rust/src/libstd/rt.rs:52:25
    = note: inside call to `std::rt::lang_start_internal` at /Users/shep/.rustup/toolchains/nightly-2019-05-27-x86_64-apple-darwin/lib/rustlib/src/rust/src/libstd/rt.rs:64:5
    = note: inside call to `std::rt::lang_start::<()>`

[RalfJung]

This actually fails on Linux as well.

error[E0080]: Miri evaluation error: can't access foreign static: environ
   --> /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src/libstd/sys/unix/os.rs:411:5
    |
411 |     &mut environ
    |     ^^^^^^^^^^^^ Miri evaluation error: can't access foreign static: environ
    |
    = note: inside call to `std::sys::unix::os::environ` at /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src/libstd/sys/unix/os.rs:426:28
    = note: inside call to `std::sys::unix::os::env` at /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src/libstd/env.rs:143:21
note: inside call to `std::env::vars_os` at src/main.rs:2:5
   --> src/main.rs:2:5
    |
2   |     std::env::vars_os();
    |     ^^^^^^^^^^^^^^^^^^^
    = note: inside call to `main` at /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src/libstd/rt.rs:64:34
    = note: inside call to closure at /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src/libstd/rt.rs:52:53
    = note: inside call to closure at /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src/libstd/panicking.rs:293:40
    = note: inside call to `std::panicking::try::do_call::<[closure@DefId(1:5870 ~ std[82ff]::rt[0]::lang_start_internal[0]::{{closure}}[0]) 0:&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe], i32>` at /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src/libstd/panicking.rs:289:5
    = note: inside call to `std::panicking::try::<i32, [closure@DefId(1:5870 ~ std[82ff]::rt[0]::lang_start_internal[0]::{{closure}}[0]) 0:&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe]>` at /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src/libstd/panic.rs:388:9
    = note: inside call to `std::panic::catch_unwind::<[closure@DefId(1:5870 ~ std[82ff]::rt[0]::lang_start_internal[0]::{{closure}}[0]) 0:&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe], i32>` at /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src/libstd/rt.rs:52:25
    = note: inside call to `std::rt::lang_start_internal` at /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src/libstd/rt.rs:64:5
    = note: inside call to `std::rt::lang_start::<()>`

[oli-obk]

I remember not implementing these. We essentially need to manually create an allocation for our env vars instead of having the current datastructure. This means we have to start emulating all of these platforms' env datastructure

[pvdrz]

Based on the work already done in #894 I could implement this for linux at least and also make it work with communication enabled.

[RalfJung]

This is much harder though if I recall. With this, the interpreted code iterates over some data structure we provide to it, so we have to provide them in the right (platform-specific) format.

I haven't looked into what this takes, but it will very likely be different for macOS, Windows and Linux. If you want to give it a shot, feel free to! Having it for Linux only would be better than not having it at all, I guess, though platform differences are also annoying.

[pvdrz]

I'm going to start working based on the linux's man entry for environ.

Edit: in a fresh new branch with a different PR :D

[pvdrz]

Apparently rust just calls _NSGetEnviron in OSX and environ in other unix platforms but both are handled in the same way. I actually have a mac to test it so I'm going to try to produce the correct *mut *const *const c_char so everything works accordingly.

[RalfJung]

Please really keep it a separate PR this time though. :)

Review complexity scales superlinearly.

[pvdrz]

Hahaha yeah, lesson learned :)