[DO NOT MERGE] make before_exec an unsafe fn

[RalfJung]

This is an experiment for #39575.

[rust-highfive]

r? @Mark-Simulacrum

(rust_highfive has picked a reviewer for you, use r? to override)

[RalfJung]

@bors try

[RalfJung]

@bors try

[RalfJung]

@bors try

[bors]

⌛ Trying commit 39c3fd7 with merge aaadaed...

[bors]

☀️ Test successful - status-travis
State: approved= try=True

[RalfJung]

@rust-lang/infra could we get a check-only crater run?

[alexcrichton]

@craterbot run start=master#289ad6e9922683807d455ca0020dc2a8f7bd1a7b end=try#aaadaed28c4f579449b007d5228f7e512be9af5f mode=check-only

[craterbot]

👌 Experiment pr-56129 created and queued.
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

[craterbot]

🚧 Experiment pr-56129 is now running on agent aws-2.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

[craterbot]

🎉 Experiment pr-56129 is completed!
📰 Open the full report.

⚠️ If you notice any spurious failure please add them to the blacklist!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

[pietroalbini]

102 regressions, including Cargo (and thus a ton of Cargo plugins).

[pietroalbini]

Ran crater-tree on the results. As usual, the graph is far from perfect and it misses some things, but it can be useful anyway.

Results

cargo-disassemble
cargo-geiger
cargo-debstatus
cargo-tally
cargo-scriptify
mdbook-epub
stund
lateral
cargo-tree
cargo
| cargo-apk
| cargo-faircode
| cargo-bom
| cargo-sphinx
| cargo-outdated
| cargo-ebuild
| cargo-dinghy
| dinghy-lib
| cargo-clone
| cargo-authors
| dinghy
| cuo
| cargo-bitbake
| cargo-vendor
| cargo-travis
| cargo-raze
| cargo-pack
| | cargo-pack-docker
| oysterpack_built
| | oysterpack
| | oysterpack_log
| nannou-new
riffol
cargo-watch
watchexec
exclave
varlink-cli
sccache
rtq
initrs
tracetree
sinit
jobserver
tokio-pty-process
axon
cntr
process_viewer
tmux-hints
rtss
varlink_stdinterfaces
varlink
commandspec
tty
eloggr
runny
spawn-ptrace
pseudoterm

[kennytm]

The cargo failure was caused by jobserver, which the tree above doesn't show 🤔

Nov 23 04:18:59.734 INFO [stderr] error[E0133]: call to unsafe function is unsafe and requires unsafe function or block
Nov 23 04:18:59.734 INFO [stderr]    --> /cargo-home/registry/src/github.com-1ecc6299db9ec823/jobserver-0.1.11/src/lib.rs:566:13
Nov 23 04:18:59.734 INFO [stderr]     |
Nov 23 04:18:59.734 INFO [stderr] 566 | /             cmd.before_exec(move || {
Nov 23 04:18:59.734 INFO [stderr] 567 | |                 set_cloexec(read, false)?;
Nov 23 04:18:59.734 INFO [stderr] 568 | |                 set_cloexec(write, false)?;
Nov 23 04:18:59.734 INFO [stderr] 569 | |                 Ok(())
Nov 23 04:18:59.734 INFO [stderr] 570 | |             });
Nov 23 04:18:59.734 INFO [stderr]     | |______________^ call to unsafe function
Nov 23 04:18:59.734 INFO [stderr]     |
Nov 23 04:18:59.734 INFO [stderr]     = note: consult the function's documentation for information on how to avoid undefined behavior

[pietroalbini]

Ok, did a simpler grep, and there are 32 crates actually failing (without counting dependencies):

List

axon
bind_spawn
cntr
commandspec
containers
fisher
initrs
jobserver
kickoff
lateral
mathsbot
minit
playlist_mgr
process_viewer
pseudoterm
ps-util
pty
repo-manager
riffol
rtq
rtss
runny
rush
sinit
spawn-ptrace
symare
tmux-hints
tokio-pty-process
tty
tydra
varlink
watchexec

[RalfJung]

Thanks for the analysis @pietroalbini! Let's discuss at #39575.