Use Rust Symbol Mangling by default

[tmiasko]

r? @michaelwoerister

[tmiasko]

@bors try

[bors]

⌛ Trying commit 493a43f55df7482188e83d68b8ca1bfc26bfd11a with merge ce59db7a1b1b012fb2793c4641c1bdecad7a128b...

[bors]

☀️ Try build successful - checks-actions
Build commit: ce59db7a1b1b012fb2793c4641c1bdecad7a128b (ce59db7a1b1b012fb2793c4641c1bdecad7a128b)

[tmiasko]

@craterbot run mode=build-and-test

[craterbot]

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[michaelwoerister]

@craterbot run mode=build-and-test

[craterbot]

👌 Experiment pr-85530 created and queued.
🤖 Automatically detected try build ce59db7a1b1b012fb2793c4641c1bdecad7a128b
🔍 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

[michaelwoerister]

Thanks for the PR, @tmiasko!

cc #60705

[bjorn3]

Should this get a perf run?

[klensy]

Should this get a perf run?

As i understand, this pr does double work: it mangle and demangle at the same time

ifletErr(_) = rustc_demangle::try_demangle(&mangled){bug!("demangle error: {:?}\n{}", instance, mangled);}

So perf run will show some non related info.

[michaelwoerister]

Yeah, I was debating whether it makes sense to do a perf run here but as @klensy points out, we also do the demangling check.

I would be interested to see how expensive that demangling check is. But we'll need a compiler with the new mangling scheme enabled by default as baseline. We could do that in another PR. It would be great if we could do the demangling check unconditionally -- although doing it as a debug assertion would also be a big improvement.

[Mark-Simulacrum]

@michaelwoerister@tmiasko Can you share why this needs to be a build-and-test Crater run? I think just building should suffice; that builds tests too: https://github.com/rust-lang/crater/blob/aa40b144e61f7f1c6ba6a3bfc5e85b52b9e4a177/src/runner/test.rs#L233

If mangling changes introduce different runtime behavior that would seem very surprising to me and likely hard to catch reliably with crater (e.g., collisions seem likely to be pretty hard to identify unless they cause obvious linker errors).

[tmiasko]

@Mark-Simulacrum potential interaction with mechanisms for collecting & formatting backtraces was one of motivations for opting for some runtime coverage. Generally, reducing the scope of a crater run to build only, seems fine to me.

[craterbot]

🚧 Experiment pr-85530 is now running

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

[craterbot]

🎉 Experiment pr-85530 is completed!
📊 78 regressed and 58 fixed (163710 total)
📰 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

[bjorn3]

ICE for encoding_rs-0.8.28:

Details

[INFO] [stderr] thread 'rustc' panicked at 'Box<Any>', /rustc/ce59db7a1b1b012fb2793c4641c1bdecad7a128b/library/std/src/panic.rs:59:5
[INFO] [stdout] error: internal compiler error: compiler/rustc_symbol_mangling/src/v0.rs:568:17: symbol_names: unsupported constant of type `[u32; 16]` (Const { ty: [u32; 16], val: Value(ByRef { alloc: Allocation { bytes: [8, 0, 0, 0, 24, 0, 0, 0, 9, 0, 0, 0, 25, 0, 0, 0, 10, 0, 0, 0, 26, 0, 0, 0, 11, 0, 0, 0, 27, 0, 0, 0, 12, 0, 0, 0, 28, 0, 0, 0, 13, 0, 0, 0, 29, 0, 0, 0, 14, 0, 0, 0, 30, 0, 0, 0, 15, 0, 0, 0, 31, 0, 0, 0], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [18446744073709551615, 0], len: Size { raw: 64 } }, align: Align { pow2: 2 }, mutability: Not, extra: () }, offset: Size { raw: 0 } }) })
[INFO] [stdout] [INFO] [stdout] [INFO] [stderr] stack backtrace:
[INFO] [stderr] 0: 0x7f328cbf74c0 - std[77c0456e0eb29f0c]::backtrace_rs::backtrace::libunwind::trace
[INFO] [stderr] at /rustc/ce59db7a1b1b012fb2793c4641c1bdecad7a128b/library/std/src/../../backtrace/src/backtrace/libunwind.rs:90:5
[INFO] [stderr] 1: 0x7f328cbf74c0 - std[77c0456e0eb29f0c]::backtrace_rs::backtrace::trace_unsynchronized::<std[77c0456e0eb29f0c]::sys_common::backtrace::_print_fmt::{closure#1}>
[INFO] [stderr] at /rustc/ce59db7a1b1b012fb2793c4641c1bdecad7a128b/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
[INFO] [stderr] 2: 0x7f328cbf74c0 - std[77c0456e0eb29f0c]::sys_common::backtrace::_print_fmt
[INFO] [stderr] at /rustc/ce59db7a1b1b012fb2793c4641c1bdecad7a128b/library/std/src/sys_common/backtrace.rs:67:5
[INFO] [stderr] 3: 0x7f328cbf74c0 - <std[77c0456e0eb29f0c]::sys_common::backtrace::_print::DisplayBacktrace as core[ee1ca6415511a9c4]::fmt::Display>::fmt
[INFO] [stderr] at /rustc/ce59db7a1b1b012fb2793c4641c1bdecad7a128b/library/std/src/sys_common/backtrace.rs:46:22
[INFO] [stderr] 4: 0x7f328cc64e9c - core[ee1ca6415511a9c4]::fmt::write
[INFO] [stderr] at /rustc/ce59db7a1b1b012fb2793c4641c1bdecad7a128b/library/core/src/fmt/mod.rs:1110:17
[INFO] [stderr] 5: 0x7f328cbe8e15 - <std[77c0456e0eb29f0c]::sys::unix::stdio::Stderr as std[77c0456e0eb29f0c]::io::Write>::write_fmt
[INFO] [stderr] at /rustc/ce59db7a1b1b012fb2793c4641c1bdecad7a128b/library/std/src/io/mod.rs:1584:15
[INFO] [stderr] 6: 0x7f328cbfb20b - std[77c0456e0eb29f0c]::sys_common::backtrace::_print
[INFO] [stderr] at /rustc/ce59db7a1b1b012fb2793c4641c1bdecad7a128b/library/std/src/sys_common/backtrace.rs:49:5
[INFO] [stderr] 7: 0x7f328cbfb20b - std[77c0456e0eb29f0c]::sys_common::backtrace::print
[INFO] [stderr] at /rustc/ce59db7a1b1b012fb2793c4641c1bdecad7a128b/library/std/src/sys_common/backtrace.rs:36:9
[INFO] [stderr] 8: 0x7f328cbfb20b - std[77c0456e0eb29f0c]::panicking::default_hook::{closure#1}
[INFO] [stderr] at /rustc/ce59db7a1b1b012fb2793c4641c1bdecad7a128b/library/std/src/panicking.rs:208:50
[INFO] [stderr] 9: 0x7f328cbface1 - std[77c0456e0eb29f0c]::panicking::default_hook
[INFO] [stderr] at /rustc/ce59db7a1b1b012fb2793c4641c1bdecad7a128b/library/std/src/panicking.rs:225:9
[INFO] [stderr] 10: 0x7f328d3b0afd - rustc_driver[483abbcf9e72e7cf]::report_ice
[INFO] [stderr] 11: 0x7f328cbfba16 - std[77c0456e0eb29f0c]::panicking::rust_panic_with_hook
[INFO] [stderr] at /rustc/ce59db7a1b1b012fb2793c4641c1bdecad7a128b/library/std/src/panicking.rs:626:17
[INFO] [stderr] 12: 0x7f328e37234b - std[77c0456e0eb29f0c]::panicking::begin_panic::<rustc_errors[a6601eba5631ab8e]::ExplicitBug>::{closure#0}
[INFO] [stderr] 13: 0x7f328e372296 - std[77c0456e0eb29f0c]::sys_common::backtrace::__rust_end_short_backtrace::<std[77c0456e0eb29f0c]::panicking::begin_panic<rustc_errors[a6601eba5631ab8e]::ExplicitBug>::{closure#0}, !>
[INFO] [stderr] 14: 0x7f328e37361f - std[77c0456e0eb29f0c]::panicking::begin_panic::<rustc_errors[a6601eba5631ab8e]::ExplicitBug>
[INFO] [stderr] 15: 0x7f328e38b73d - std[77c0456e0eb29f0c]::panic::panic_any::<rustc_errors[a6601eba5631ab8e]::ExplicitBug>
[INFO] [stderr] 16: 0x7f328e38e5da - <rustc_errors[a6601eba5631ab8e]::HandlerInner>::bug
[INFO] [stderr] 17: 0x7f328e38e080 - <rustc_errors[a6601eba5631ab8e]::Handler>::bug
[INFO] [stderr] 18: 0x7f328e2c8450 - rustc_middle[4cd8eb4e66530e50]::ty::context::tls::with_opt::<rustc_middle[4cd8eb4e66530e50]::util::bug::opt_span_bug_fmt<rustc_span[41f5d8395d191526]::span_encoding::Span>::{closure#0}, ()>
[INFO] [stderr] 19: 0x7f328e2cd500 - rustc_middle[4cd8eb4e66530e50]::util::bug::opt_span_bug_fmt::<rustc_span[41f5d8395d191526]::span_encoding::Span>
[INFO] [stderr] 20: 0x7f328e2cd476 - rustc_middle[4cd8eb4e66530e50]::util::bug::bug_fmt
[INFO] [stderr] 21: 0x7f328f4f7957 - <rustc_symbol_mangling[e3ac7cad7aae7613]::v0::SymbolMangler as rustc_middle[4cd8eb4e66530e50]::ty::print::Printer>::print_const
[INFO] [stderr] 22: 0x7f328ead1f79 - <rustc_symbol_mangling[e3ac7cad7aae7613]::v0::SymbolMangler as rustc_middle[4cd8eb4e66530e50]::ty::print::Printer>::print_def_path
[INFO] [stderr] 23: 0x7f328eace1ac - rustc_symbol_mangling[e3ac7cad7aae7613]::v0::mangle
[INFO] [stderr] 24: 0x7f328eadafba - rustc_symbol_mangling[e3ac7cad7aae7613]::symbol_name_provider
[INFO] [stderr] 25: 0x7f328e7a7183 - <rustc_query_impl[73652419363b7eb3]::queries::symbol_name as rustc_query_system[195a98efe178d20a]::query::config::QueryAccessors<rustc_query_impl[73652419363b7eb3]::plumbing::QueryCtxt>>::compute
[INFO] [stderr] 26: 0x7f328e7ee766 - <rustc_query_system[195a98efe178d20a]::dep_graph::graph::DepGraph<rustc_middle[4cd8eb4e66530e50]::dep_graph::dep_node::DepKind>>::with_task_impl::<rustc_query_impl[73652419363b7eb3]::plumbing::QueryCtxt, rustc_middle[4cd8eb4e66530e50]::ty::instance::Instance, rustc_middle[4cd8eb4e66530e50]::ty::SymbolName, for<'a, 'b> fn(&'a mut rustc_middle[4cd8eb4e66530e50]::ich::hcx::StableHashingContext, &'b rustc_middle[4cd8eb4e66530e50]::ty::SymbolName) -> core[ee1ca6415511a9c4]::option::Option<rustc_data_structures[52e6d6087bd5b52c]::fingerprint::Fingerprint>>
[INFO] [stderr] 27: 0x7f328e7fa9af - rustc_data_structures[52e6d6087bd5b52c]::stack::ensure_sufficient_stack::<(rustc_middle[4cd8eb4e66530e50]::ty::SymbolName, rustc_query_system[195a98efe178d20a]::dep_graph::graph::DepNodeIndex), rustc_query_system[195a98efe178d20a]::query::plumbing::force_query_with_job<rustc_query_system[195a98efe178d20a]::query::caches::DefaultCache<rustc_middle[4cd8eb4e66530e50]::ty::instance::Instance, rustc_middle[4cd8eb4e66530e50]::ty::SymbolName>, rustc_query_impl[73652419363b7eb3]::plumbing::QueryCtxt>::{closure#0}::{closure#0}>
[...]

[tmiasko]

Errors related to the use of unstable const generics feature with types that are currently unsupported in v0 mangling:

• ametisf/snapshot_repeat <impl at src/lib.rs:30:1: 40:2>::to_norm (unsupported constant of type f32)
• bounded 0.1.2 temp::temp::<std::collections::Bound::<usize>::Included(0_usize), std::collections::Bound::<usize>::Included(9_usize)>
• danielbank/rust-const-generics <impl at examples/state.rs:17:1: 25:2>::freeze (unsupported constant of type &str)
• encoding-rs 0.8.28 packed_simd::__shuffle_vector16::<[8_u32, 24_u32, 9_u32, 25_u32, 10_u32, 26_u32, 11_u32, 27_u32, 12_u32, 28_u32, 13_u32, 29_u32, 14_u32, 30_u32, 15_u32, 31_u32], packed_simd::codegen::v128::u8x16, packed_simd::codegen::v128::u8x16>
• fast_rsync 0.1.3 packed_simd_2::__shuffle_vector8::<[2_u32, 10_u32, 3_u32, 11_u32, 6_u32, 14_u32, 7_u32, 15_u32], packed_simd_2::codegen::v256::u32x8, packed_simd_2::codegen::v256::u32x8>
• nommy 0.4.1 parse::<[text::tag::Tag<".">; 3], std::str::Chars>
• ritobanrc/firework <typetag::erased_serde::de::erase::Visitor<objects::rect::_::<impl at src/objects/rect.rs:13:28: 13:46>::deserialize::__FieldVisitor> as typetag::erased_serde::de::Visitor>::erased_visit_i64 (unsupported constant of type Axis)
• tiny-uom 0.1.0 <tiny_uom::Quantity<tiny_uom::Unit { m: 1_i8, kg: 0_i8, s: -1_i8, A: 0_i8, K: 0_i8, mol: 0_i8, cd: 0_i8 }> as std::fmt::Debug>::fmt
• umbra-lang 0.15.0 ops::<impl at src/ops.rs:637:1: 654:2>::op (unsupported constant of type ops::Op)

In logs there are two dozens of backtraces with mangled symbols (in cases where crate internally uses rustc-demangle crate without support for v0 mangling scheme).

The backtraces generated for RUST_BACKTRACE=full now include a crate hash for every mangled path, so there might be multiple hashes per symbol. Together with generic arguments this is even more verbose than before.

Summary of results:

Result	legacy	v0
broken:cargo-toml	1912	1912
broken:missing-deps	2730	2730
broken:missing-git-repository	12747	12747
broken:yanked	377	377
build-fail:compiler-error	9201	9172
build-fail:depends-on	13584	13551
build-fail:ice	3	10
build-fail:oom	7201	7460
build-fail:timeout	78	72
build-fail:unknown	10728	10728
error	328	328
test-fail:oom	599	625
test-fail:timeout	277	272
test-fail:unknown	8730	8698
test-pass	95149	94962
test-skipped	59	59

The most immediate question raised by those results is related to const generics. Enabling new mangling scheme will make it harder to experiment with unstable parts of const generics. Should we wait with switching the default until new mangling reaches parity with legacy scheme?

[tmiasko]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

[eddyb]

@craterbot run mode=build-and-test crates=list:https://crater-reports.s3.amazonaws.com/pr-85530/retry-regressed-list.txt

[craterbot]

🚨 Error: missing desired crates: {"https://crater-reports.s3.amazonaws.com/pr-85530/retry-regressed-list.txt"}

🆘 If you have any trouble with Crater please ping @rust-lang/infra!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

[eddyb]

@craterbot run mode=build-and-test crates=https://crater-reports.s3.amazonaws.com/pr-85530/retry-regressed-list.txt p=1

@Mark-Simulacrum if this one works (see my previous failed attempt above), the crater docs need updating AFAICT.

[craterbot]

👌 Experiment pr-85530-1 created and queued.
🤖 Automatically detected try build 2b00690a2a9987274f9d399383a581d5df1bf5df
🔍 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-85530-1 is now running

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

[craterbot]

🎉 Experiment pr-85530-1 is completed!
📊 15 regressed and 11 fixed (78 total)
📰 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

[eddyb]

I'm not sure I'm not missing anything (I didn't open every single log), but AFAICT this is the only regression now:

error: internal compiler error: compiler/rustc_symbol_mangling/src/v0.rs:693:17:
symbol_names: unsupported constant of type `f32` (Const{ty: f32,val:Value(Scalar(0x3f800000))})

I explicitly said I don't want to support f32, it's a bug that it's not disallowed much earlier in the compilation, so this is fine.

[tmiasko]

It looks like #87194 will contain all necessary changes, and this PR already served its role for crater run, so I am going to close it now.

Remaining test changes, that are not already part of #87194, landed in #87789.