Return ExitCode from rustc_driver::main instead of calling process::exit

[ChrisDenton]

This makes rustc simply return an exit code from main rather than calling std::process::exit with an exit code. This means that drops run normally and the process exits cleanly. This is similar to what happens when an ICE occurs (due to being a panic that's caught by std's lang_start).

Also instead of hard coding success and failure codes this uses ExitCode::SUCCESS and ExitCode::FAILURE, which in turn effectively uses libc::EXIT_SUCCESS and libc::EXIT_FAILURE (via std). These are 0 and 1 respectively for all currently supported host platforms so it doesn't actually change the exit code.

[rustbot]

r? @SparrowLii

rustbot has assigned @SparrowLii.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[rustbot]

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

[rustbot]

The Miri subtree was changed

cc @rust-lang/miri

[Kobzol]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: ffd099f (ffd099ff891368a934635eba38de913f96f6ab17, parent: 1bf12c32a08384862297674921d1137ad94892dc)

[rust-timer]

Finished benchmarking commit (ffd099f): comparison URL.

Overall result: ❌✅ regressions and improvements - no action needed

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

@bors rollup=never
@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	0.2%	[0.2%, 0.2%]	1
Regressions ❌ (secondary)	0.2%	[0.2%, 0.2%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.0%	[-0.1%, -0.0%]	3
All ❌✅ (primary)	0.2%	[0.2%, 0.2%]	1

Max RSS (memory usage)

Results (secondary -1.4%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.2%	[1.6%, 2.4%]	4
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-4.2%	[-5.1%, -3.7%]	5
All ❌✅ (primary)	-	-	0

Cycles

Results (secondary 2.8%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	4.3%	[2.5%, 6.6%]	7
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.4%	[-2.6%, -2.2%]	2
All ❌✅ (primary)	-	-	0

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 482.343s -> 483.621s (0.26%)
Artifact size: 392.46 MiB -> 390.44 MiB (-0.51%)

[ChrisDenton]

Annoyingly ExitCode does not have a method to convert it to the i32 that process::exit requires. I think this is a libs issue that should be addressed.

[RalfJung]

Yeah that is unfortunate.

Either way, 👍 for the Miri changes.

[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[ChrisDenton]

I've changed this so that people can optionally return an ExitCode when using catch_with_exit_code rather than having to use process::exit.

Note that the Termination trait is implemented for () so this shouldn't make a difference to existing code unless they opt-in to returning ExitCode (or anything else that implements the trait).