Improve debuginfo for closures and async functions on Windows MSVC#83941

wesleywiser · 2021-04-06T17:59:46Z

The issue was that the resulting debuginfo was too complex for LLVM to
translate into CodeView records correctly. As a result, it simply
ignored the debuginfo which meant Windows debuggers could not display
any closed over variables when stepping inside a closure or async fn.

This fixes that by creating additional allocas on the stack so that
the resulting debuginfo is simple (just *my_variable.dbg.spill) and
LLVM can generate the correct CV records.

I also updated some of our existing tests to run in CDB to cover this case.

Before (closure):

After (closure):

Before (async):

After (async):

Fixes #83709

wesleywiser · 2021-04-07T13:28:04Z

Highfive failed to assign someone.

r? @nagisa but feel free to reassign 🙂

nagisa

r=me LGTM, up to you if you want to act on the comments inline.

compiler/rustc_codegen_ssa/src/mir/debuginfo.rs

nagisa · 2021-04-07T22:24:14Z

compiler/rustc_codegen_ssa/src/mir/debuginfo.rs

It is unfortunate that this is necessary, but I guess gotta do what we gotta do. Did you check if clang has a similar problem/needs to implement a similar workaround when targeting msvc?

Yeah clang has the same issue when targeting msvc.

The issue was that the resulting debuginfo was too complex for LLVM to translate into CodeView records correctly. As a result, it simply ignored the debuginfo which meant Windows debuggers could not display any closed over variables when stepping inside a closure. This fixes that by spilling additional variables to the stack so that the resulting debuginfo is simple (just `*my_variable.dbg.spill`) and LLVM can generate the correct CV records.

wesleywiser · 2021-04-08T18:53:39Z

Thanks @nagisa!

@bors r=nagisa

bors · 2021-04-08T18:53:40Z

📌 Commit 533002d has been approved by nagisa

bors · 2021-04-08T23:09:09Z

⌛ Testing commit 533002d with merge 619d19c...

bors · 2021-04-09T01:49:55Z

☀️ Test successful - checks-actions
Approved by: nagisa
Pushing 619d19c to master...

Pkgsrc changes: * Bump bootstrap requirements to 1.52.1 * Adjust patches, adapt to upstream changes, adjust cargo checksums * If using an external llvm, require >= 10.0 Upsteream changes: Version 1.53.0 (2021-06-17) ============================ Language ----------------------- - [You can now use unicode for identifiers.][83799] This allows multilingual identifiers but still doesn't allow glyphs that are not considered characters such as `#` (diamond) or `<U+1F980>` (crab). More specifically you can now use any identifier that matches the UAX #31 "Unicode Identifier and Pattern Syntax" standard. This is the same standard as languages like Python, however Rust uses NFC normalization which may be different from other languages. - [You can now specify "or patterns" inside pattern matches.][79278] Previously you could only use `|` (OR) on complete patterns. E.g. ```rust let x = Some(2u8); // Before matches!(x, Some(1) | Some(2)); // Now matches!(x, Some(1 | 2)); ``` - [Added the `:pat_param` `macro_rules!` matcher.][83386] This matcher has the same semantics as the `:pat` matcher. This is to allow `:pat` to change semantics to being a pattern fragment in a future edition. Compiler ----------------------- - [Updated the minimum external LLVM version to LLVM 10.][83387] - [Added Tier 3\* support for the `wasm64-unknown-unknown` target.][80525] - [Improved debuginfo for closures and async functions on Windows MSVC.][83941] \* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. Libraries ----------------------- - [Abort messages will now forward to `android_set_abort_message` on Android platforms when available.][81469] - [`slice::IterMut<'_, T>` now implements `AsRef<[T]>`][82771] - [Arrays of any length now implement `IntoIterator`.][84147] Currently calling `.into_iter()` as a method on an array will return `impl Iterator<Item=&T>`, but this may change in a future edition to change `Item` to `T`. Calling `IntoIterator::into_iter` directly on arrays will provide `impl Iterator<Item=T>` as expected. - [`leading_zeros`, and `trailing_zeros` are now available on all `NonZero` integer types.][84082] - [`{f32, f64}::from_str` now parse and print special values (`NaN`, `-0`) according to IEEE RFC 754.][78618] - [You can now index into slices using `(Bound<usize>, Bound<usize>)`.][77704] - [Add the `BITS` associated constant to all numeric types.][82565] Stabilised APIs --------------- - [`AtomicBool::fetch_update`] - [`AtomicPtr::fetch_update`] - [`BTreeMap::retain`] - [`BTreeSet::retain`] - [`BufReader::seek_relative`] - [`DebugStruct::non_exhaustive`] - [`Duration::MAX`] - [`Duration::ZERO`] - [`Duration::is_zero`] - [`Duration::saturating_add`] - [`Duration::saturating_mul`] - [`Duration::saturating_sub`] - [`ErrorKind::Unsupported`] - [`Option::insert`] - [`Ordering::is_eq`] - [`Ordering::is_ge`] - [`Ordering::is_gt`] - [`Ordering::is_le`] - [`Ordering::is_lt`] - [`Ordering::is_ne`] - [`OsStr::is_ascii`] - [`OsStr::make_ascii_lowercase`] - [`OsStr::make_ascii_uppercase`] - [`OsStr::to_ascii_lowercase`] - [`OsStr::to_ascii_uppercase`] - [`Peekable::peek_mut`] - [`Rc::decrement_strong_count`] - [`Rc::increment_strong_count`] - [`Vec::extend_from_within`] - [`array::from_mut`] - [`array::from_ref`] - [`char::MAX`] - [`char::REPLACEMENT_CHARACTER`] - [`char::UNICODE_VERSION`] - [`char::decode_utf16`] - [`char::from_digit`] - [`char::from_u32_unchecked`] - [`char::from_u32`] - [`cmp::max_by_key`] - [`cmp::max_by`] - [`cmp::min_by_key`] - [`cmp::min_by`] - [`f32::is_subnormal`] - [`f64::is_subnormal`] Cargo ----------------------- - [Cargo now supports git repositories where the default `HEAD` branch is not "master".][cargo/9392] This also includes a switch to the version 3 `Cargo.lock` format which can handle default branches correctly. - [macOS targets now default to `unpacked` split-debuginfo.][cargo/9298] - [The `authors` field is no longer included in `Cargo.toml` for new projects.][cargo/9282] Rustdoc ----------------------- - [Added the `rustdoc::bare_urls` lint that warns when you have URLs without hyperlinks.][81764] Compatibility Notes ------------------- - [Implement token-based handling of attributes during expansion][82608] - [`Ipv4::from_str` will now reject octal format IP addresses in addition to rejecting hexadecimal IP addresses.][83652] The octal format can lead to confusion and potential security vulnerabilities and [is no longer recommended][ietf6943]. Internal Only ------------- These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools. - [Rework the `std::sys::windows::alloc` implementation.][83065] - [rustdoc: Don't enter an infer_ctxt in get_blanket_impls for impls that aren't blanket impls.][82864] - [rustdoc: Only look at blanket impls in `get_blanket_impls`][83681] - [Rework rustdoc const type][82873] [83386]: rust-lang/rust#83386 [82771]: rust-lang/rust#82771 [84147]: rust-lang/rust#84147 [84082]: rust-lang/rust#84082 [83799]: rust-lang/rust#83799 [83681]: rust-lang/rust#83681 [83652]: rust-lang/rust#83652 [83387]: rust-lang/rust#83387 [82873]: rust-lang/rust#82873 [82864]: rust-lang/rust#82864 [82608]: rust-lang/rust#82608 [82565]: rust-lang/rust#82565 [80525]: rust-lang/rust#80525 [79278]: rust-lang/rust#79278 [78618]: rust-lang/rust#78618 [77704]: rust-lang/rust#77704 [83941]: rust-lang/rust#83941 [83065]: rust-lang/rust#83065 [81764]: rust-lang/rust#81764 [81469]: rust-lang/rust#81469 [cargo/9298]: rust-lang/cargo#9298 [cargo/9282]: rust-lang/cargo#9282 [cargo/9392]: rust-lang/cargo#9392 [`char::MAX`]: https://doc.rust-lang.org/std/primitive.char.html#associatedconstant.MAX [`char::REPLACEMENT_CHARACTER`]: https://doc.rust-lang.org/std/primitive.char.html#associatedconstant.REPLACEMENT_CHARACTER [`char::UNICODE_VERSION`]: https://doc.rust-lang.org/std/primitive.char.html#associatedconstant.UNICODE_VERSION [`char::decode_utf16`]: https://doc.rust-lang.org/std/primitive.char.html#method.decode_utf16 [`char::from_u32`]: https://doc.rust-lang.org/std/primitive.char.html#method.from_u32 [`char::from_u32_unchecked`]: https://doc.rust-lang.org/std/primitive.char.html#method.from_u32_unchecked [`char::from_digit`]: https://doc.rust-lang.org/std/primitive.char.html#method.from_digit [`AtomicBool::fetch_update`]: https://doc.rust-lang.org/std/sync/atomic/struct.AtomicBool.html#method.fetch_update [`AtomicPtr::fetch_update`]: https://doc.rust-lang.org/std/sync/atomic/struct.AtomicPtr.html#method.fetch_update [`BTreeMap::retain`]: https://doc.rust-lang.org/std/collections/struct.BTreeMap.html#method.retain [`BTreeSet::retain`]: https://doc.rust-lang.org/std/collections/struct.BTreeSet.html#method.retain [`BufReader::seek_relative`]: https://doc.rust-lang.org/std/io/struct.BufReader.html#method.seek_relative [`DebugStruct::non_exhaustive`]: https://doc.rust-lang.org/std/fmt/struct.DebugStruct.html#method.finish_non_exhaustive [`Duration::MAX`]: https://doc.rust-lang.org/std/time/struct.Duration.html#associatedconstant.MAX [`Duration::ZERO`]: https://doc.rust-lang.org/std/time/struct.Duration.html#associatedconstant.ZERO [`Duration::is_zero`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.is_zero [`Duration::saturating_add`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.saturating_add [`Duration::saturating_mul`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.saturating_mul [`Duration::saturating_sub`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.saturating_sub [`ErrorKind::Unsupported`]: https://doc.rust-lang.org/std/io/enum.ErrorKind.html#variant.Unsupported [`Option::insert`]: https://doc.rust-lang.org/std/option/enum.Option.html#method.insert [`Ordering::is_eq`]: https://doc.rust-lang.org/std/cmp/enum.Ordering.html#method.is_eq [`Ordering::is_ge`]: https://doc.rust-lang.org/std/cmp/enum.Ordering.html#method.is_ge [`Ordering::is_gt`]: https://doc.rust-lang.org/std/cmp/enum.Ordering.html#method.is_gt [`Ordering::is_le`]: https://doc.rust-lang.org/std/cmp/enum.Ordering.html#method.is_le [`Ordering::is_lt`]: https://doc.rust-lang.org/std/cmp/enum.Ordering.html#method.is_lt [`Ordering::is_ne`]: https://doc.rust-lang.org/std/cmp/enum.Ordering.html#method.is_ne [`OsStr::eq_ignore_ascii_case`]: https://doc.rust-lang.org/std/ffi/struct.OsStr.html#method.eq_ignore_ascii_case [`OsStr::is_ascii`]: https://doc.rust-lang.org/std/ffi/struct.OsStr.html#method.is_ascii [`OsStr::make_ascii_lowercase`]: https://doc.rust-lang.org/std/ffi/struct.OsStr.html#method.make_ascii_lowercase [`OsStr::make_ascii_uppercase`]: https://doc.rust-lang.org/std/ffi/struct.OsStr.html#method.make_ascii_uppercase [`OsStr::to_ascii_lowercase`]: https://doc.rust-lang.org/std/ffi/struct.OsStr.html#method.to_ascii_lowercase [`OsStr::to_ascii_uppercase`]: https://doc.rust-lang.org/std/ffi/struct.OsStr.html#method.to_ascii_uppercase [`Peekable::peek_mut`]: https://doc.rust-lang.org/std/iter/struct.Peekable.html#method.peek_mut [`Rc::decrement_strong_count`]: https://doc.rust-lang.org/std/rc/struct.Rc.html#method.increment_strong_count [`Rc::increment_strong_count`]: https://doc.rust-lang.org/std/rc/struct.Rc.html#method.increment_strong_count [`Vec::extend_from_within`]: https://doc.rust-lang.org/beta/std/vec/struct.Vec.html#method.extend_from_within [`array::from_mut`]: https://doc.rust-lang.org/beta/std/array/fn.from_mut.html [`array::from_ref`]: https://doc.rust-lang.org/beta/std/array/fn.from_ref.html [`cmp::max_by_key`]: https://doc.rust-lang.org/beta/std/cmp/fn.max_by_key.html [`cmp::max_by`]: https://doc.rust-lang.org/beta/std/cmp/fn.max_by.html [`cmp::min_by_key`]: https://doc.rust-lang.org/beta/std/cmp/fn.min_by_key.html [`cmp::min_by`]: https://doc.rust-lang.org/beta/std/cmp/fn.min_by.html [`f32::is_subnormal`]: https://doc.rust-lang.org/std/primitive.f64.html#method.is_subnormal [`f64::is_subnormal`]: https://doc.rust-lang.org/std/primitive.f64.html#method.is_subnormal [ietf6943]: https://datatracker.ietf.org/doc/html/rfc6943#section-3.1.1

wesleywiser added A-debuginfo Area: Debugging information in compiled programs (DWARF, PDB, etc.) O-windows-msvc Toolchain: MSVC, Operating system: Windows labels Apr 6, 2021

rust-highfive assigned nagisa Apr 7, 2021

wesleywiser added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Apr 7, 2021

wesleywiser force-pushed the win_dbginfo_closures branch from ead04ac to 77dd5c8 Compare April 7, 2021 21:31

nagisa approved these changes Apr 7, 2021

View reviewed changes

wesleywiser force-pushed the win_dbginfo_closures branch from 77dd5c8 to 533002d Compare April 8, 2021 18:09

wesleywiser changed the title ~~Fix closed over variables not available in debuginfo for Windows MSVC~~ Improve debuginfo for closures and async functions on Windows MSVC Apr 8, 2021

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Apr 8, 2021

bors added the merged-by-bors This PR was explicitly merged by bors. label Apr 9, 2021

bors merged commit 619d19c into rust-lang:master Apr 9, 2021

rustbot added this to the 1.53.0 milestone Apr 9, 2021

MichalStrehovsky mentioned this pull request Apr 10, 2021

Improve debuggability of IEnummerable<T> MoveNext methods dotnet/runtimelab#660

Open

nagisa mentioned this pull request Jul 9, 2021

Improve opaque pointers support #86873

Merged

tmiasko mentioned this pull request Dec 6, 2022

Variable debuginfo introduces undefined behaviour #105386

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Improve debuginfo for closures and async functions on Windows MSVC#83941