Create more accurate debuginfo for vtables. #89597

michaelwoerister · 2021-10-06T14:28:18Z

Before this PR all vtables would have the same name ("vtable") in debuginfo. Now they get an unambiguous name that identifies the implementing type and the trait that is being implemented.

This is only one of several possible improvements:

This PR describes vtables as arrays of *const u8 pointers. It would nice to describe them as structs where function pointer is represented by a field with a name indicative of the method it maps to. However, this requires coming up with a naming scheme that avoids clashes between methods with the same name (which is possible if the vtable contains multiple traits).
The PR does not update the debuginfo we generate for the vtable-pointer field in a fat dyn pointer. Right now there does not seem to be an easy way of getting ahold of a vtable-layout without also knowing the concrete self-type of a trait object.

r? @wesleywiser

rust-highfive · 2021-10-06T14:28:26Z

Some changes occured to rustc_codegen_gcc

cc @antoyo

antoyo

The GCC part looks good to me.

michaelwoerister · 2021-10-07T10:21:47Z

Thanks for taking a look, @antoyo!

wesleywiser · 2021-10-08T02:01:57Z

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

+    // FIXME: We describe the vtable as an array of *const u8 pointers. The length of the array is
+    //        correct - but we could create a more accurate description, e.g. by describing it
+    //        as a struct where each field has a name that corresponds to the name of the method
+    //        it points to.
+    //        However, this is not entirely straightforward because there might be multiple
+    //        methods with the same name if the vtable is for multiple traits. So for now we keep
+    //        things simple instead of adding some ad-hoc disambiguation scheme.


Should these perhaps be void/() pointers instead of u8 pointers? That would probably be less misleading in the debugger than showing whatever the first byte of the function happens to be.

Done. However, I noticed that we print () as tuple$<> on MSVC, which looks a bit weird. Should we change that to void? I'm not sure how special void is as a type in C/C++ and therefore could cause trouble.

Hmm that is weird. I'll put a bug in for that and maybe fix that next week.

Before this commit all vtables would have the same name "vtable" in debuginfo. Now they get a name that identifies the implementing type and the trait that is being implemented.

wesleywiser · 2021-10-09T15:36:34Z

@bors r+

bors · 2021-10-09T15:36:35Z

📌 Commit 61c5a6d has been approved by wesleywiser

bors · 2021-10-11T04:31:50Z

⌛ Testing commit 61c5a6d with merge 9a75781...

bors · 2021-10-11T07:27:38Z

☀️ Test successful - checks-actions
Approved by: wesleywiser
Pushing 9a75781 to master...

rust-timer · 2021-10-11T09:00:32Z

Finished benchmarking commit (9a75781): comparison url.

Summary: This benchmark run did not return any relevant changes.

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression

Pkgsrc changes: * Adapt a couple of patches Upstream changes: Version 1.57.0 (2021-12-02) ========================== Language -------- - [Macro attributes may follow `#[derive]` and will see the original (pre-`cfg`) input.][87220] - [Accept curly-brace macros in expressions, like `m!{ .. }.method()` and `m!{ .. }?`.][88690] - [Allow panicking in constant evaluation.][89508] Compiler -------- - [Create more accurate debuginfo for vtables.][89597] - [Add `armv6k-nintendo-3ds` at Tier 3\*.][88529] - [Add `armv7-unknown-linux-uclibceabihf` at Tier 3\*.][88952] - [Add `m68k-unknown-linux-gnu` at Tier 3\*.][88321] - [Add SOLID targets at Tier 3\*:][86191] `aarch64-kmc-solid_asp3`, `armv7a-kmc-solid_asp3-eabi`, `armv7a-kmc-solid_asp3-eabihf` \* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. Libraries --------- - [Avoid allocations and copying in `Vec::leak`][89337] - [Add `#[repr(i8)]` to `Ordering`][89507] - [Optimize `File::read_to_end` and `read_to_string`][89582] - [Update to Unicode 14.0][89614] - [Many more functions are marked `#[must_use]`][89692], producing a warning when ignoring their return value. This helps catch mistakes such as expecting a function to mutate a value in place rather than return a new value. Stabilised APIs --------------- - [`[T; N]::as_mut_slice`][`array::as_mut_slice`] - [`[T; N]::as_slice`][`array::as_slice`] - [`collections::TryReserveError`] - [`HashMap::try_reserve`] - [`HashSet::try_reserve`] - [`String::try_reserve`] - [`String::try_reserve_exact`] - [`Vec::try_reserve`] - [`Vec::try_reserve_exact`] - [`VecDeque::try_reserve`] - [`VecDeque::try_reserve_exact`] - [`Iterator::map_while`] - [`iter::MapWhile`] - [`proc_macro::is_available`] - [`Command::get_program`] - [`Command::get_args`] - [`Command::get_envs`] - [`Command::get_current_dir`] - [`CommandArgs`] - [`CommandEnvs`] These APIs are now usable in const contexts: - [`hint::unreachable_unchecked`] Cargo ----- - [Stabilize custom profiles][cargo/9943] Compatibility notes ------------------- Internal changes ---------------- These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools. - [Added an experimental backend for codegen with `libgccjit`.][87260] [86191]: rust-lang/rust#86191 [87220]: rust-lang/rust#87220 [87260]: rust-lang/rust#87260 [88243]: rust-lang/rust#88243 [88321]: rust-lang/rust#88321 [88529]: rust-lang/rust#88529 [88690]: rust-lang/rust#88690 [88952]: rust-lang/rust#88952 [89337]: rust-lang/rust#89337 [89507]: rust-lang/rust#89507 [89508]: rust-lang/rust#89508 [89582]: rust-lang/rust#89582 [89597]: rust-lang/rust#89597 [89614]: rust-lang/rust#89614 [89692]: rust-lang/rust#89692 [cargo/9943]: rust-lang/cargo#9943 [`array::as_mut_slice`]: https://doc.rust-lang.org/std/primitive.array.html#method.as_mut_slice [`array::as_slice`]: https://doc.rust-lang.org/std/primitive.array.html#method.as_slice [`collections::TryReserveError`]: https://doc.rust-lang.org/std/collections/struct.TryReserveError.html [`HashMap::try_reserve`]: https://doc.rust-lang.org/std/collections/hash_map/struct.HashMap.html#method.try_reserve [`HashSet::try_reserve`]: https://doc.rust-lang.org/std/collections/hash_set/struct.HashSet.html#method.try_reserve [`String::try_reserve`]: https://doc.rust-lang.org/alloc/string/struct.String.html#method.try_reserve [`String::try_reserve_exact`]: https://doc.rust-lang.org/alloc/string/struct.String.html#method.try_reserve_exact [`Vec::try_reserve`]: https://doc.rust-lang.org/std/vec/struct.Vec.html#method.try_reserve [`Vec::try_reserve_exact`]: https://doc.rust-lang.org/std/vec/struct.Vec.html#method.try_reserve_exact [`VecDeque::try_reserve`]: https://doc.rust-lang.org/std/collections/struct.VecDeque.html#method.try_reserve [`VecDeque::try_reserve_exact`]: https://doc.rust-lang.org/std/collections/struct.VecDeque.html#method.try_reserve_exact [`Iterator::map_while`]: https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.map_while [`iter::MapWhile`]: https://doc.rust-lang.org/std/iter/struct.MapWhile.html [`proc_macro::is_available`]: https://doc.rust-lang.org/proc_macro/fn.is_available.html [`Command::get_program`]: https://doc.rust-lang.org/std/process/struct.Command.html#method.get_program [`Command::get_args`]: https://doc.rust-lang.org/std/process/struct.Command.html#method.get_args [`Command::get_envs`]: https://doc.rust-lang.org/std/process/struct.Command.html#method.get_envs [`Command::get_current_dir`]: https://doc.rust-lang.org/std/process/struct.Command.html#method.get_current_dir [`CommandArgs`]: https://doc.rust-lang.org/std/process/struct.CommandArgs.html [`CommandEnvs`]: https://doc.rust-lang.org/std/process/struct.CommandEnvs.html

…info, r=wesleywiser Create more accurate debuginfo for vtables. Before this PR all vtables would have the same name (`"vtable"`) in debuginfo. Now they get an unambiguous name that identifies the implementing type and the trait that is being implemented. This is only one of several possible improvements: - This PR describes vtables as arrays of `*const u8` pointers. It would nice to describe them as structs where function pointer is represented by a field with a name indicative of the method it maps to. However, this requires coming up with a naming scheme that avoids clashes between methods with the same name (which is possible if the vtable contains multiple traits). - The PR does not update the debuginfo we generate for the vtable-pointer field in a fat `dyn` pointer. Right now there does not seem to be an easy way of getting ahold of a vtable-layout without also knowing the concrete self-type of a trait object. r? `@wesleywiser`

Pkgsrc changes: * Adjust line numbers in a number of patches * remove the --disable-dist-src option, so that we produce the rust-src rust component, which we upload to LOCALSRC to allow the rust-src package to build, which is needed for rust-analyzer. * Cargo checksum for vendor/cc no longer needs patching; checksum for vendor/libc updated Upstream changes: Version 1.57.0 (2021-12-02) ========================== Language -------- - [Macro attributes may follow `#[derive]` and will see the original (pre-`cfg`) input.][87220] - [Accept curly-brace macros in expressions, like `m!{ .. }.method()` and `m!{ .. }?`.][88690] - [Allow panicking in constant evaluation.][89508] Compiler -------- - [Create more accurate debuginfo for vtables.][89597] - [Add `armv6k-nintendo-3ds` at Tier 3\*.][88529] - [Add `armv7-unknown-linux-uclibceabihf` at Tier 3\*.][88952] - [Add `m68k-unknown-linux-gnu` at Tier 3\*.][88321] - [Add SOLID targets at Tier 3\*:][86191] `aarch64-kmc-solid_asp3`, `armv7a-kmc-solid_asp3-eabi`, `armv7a-kmc-solid_asp3-eabihf` \* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. Libraries --------- - [Avoid allocations and copying in `Vec::leak`][89337] - [Add `#[repr(i8)]` to `Ordering`][89507] - [Optimize `File::read_to_end` and `read_to_string`][89582] - [Update to Unicode 14.0][89614] - [Many more functions are marked `#[must_use]`][89692], producing a warning when ignoring their return value. This helps catch mistakes such as expecting a function to mutate a value in place rather than return a new value. Stabilised APIs --------------- - [`[T; N]::as_mut_slice`][`array::as_mut_slice`] - [`[T; N]::as_slice`][`array::as_slice`] - [`collections::TryReserveError`] - [`HashMap::try_reserve`] - [`HashSet::try_reserve`] - [`String::try_reserve`] - [`String::try_reserve_exact`] - [`Vec::try_reserve`] - [`Vec::try_reserve_exact`] - [`VecDeque::try_reserve`] - [`VecDeque::try_reserve_exact`] - [`Iterator::map_while`] - [`iter::MapWhile`] - [`proc_macro::is_available`] - [`Command::get_program`] - [`Command::get_args`] - [`Command::get_envs`] - [`Command::get_current_dir`] - [`CommandArgs`] - [`CommandEnvs`] These APIs are now usable in const contexts: - [`hint::unreachable_unchecked`] Cargo ----- - [Stabilize custom profiles][cargo/9943] Compatibility notes ------------------- Internal changes ---------------- These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools. - [Added an experimental backend for codegen with `libgccjit`.][87260] [86191]: rust-lang/rust#86191 [87220]: rust-lang/rust#87220 [87260]: rust-lang/rust#87260 [88243]: rust-lang/rust#88243 [88321]: rust-lang/rust#88321 [88529]: rust-lang/rust#88529 [88690]: rust-lang/rust#88690 [88952]: rust-lang/rust#88952 [89337]: rust-lang/rust#89337 [89507]: rust-lang/rust#89507 [89508]: rust-lang/rust#89508 [89582]: rust-lang/rust#89582 [89597]: rust-lang/rust#89597 [89614]: rust-lang/rust#89614 [89692]: rust-lang/rust#89692 [cargo/9943]: rust-lang/cargo#9943 [`array::as_mut_slice`]: https://doc.rust-lang.org/std/primitive.array.html#method.as_mut_slice [`array::as_slice`]: https://doc.rust-lang.org/std/primitive.array.html#method.as_slice [`collections::TryReserveError`]: https://doc.rust-lang.org/std/collections/struct.TryReserveError.html [`HashMap::try_reserve`]: https://doc.rust-lang.org/std/collections/hash_map/struct.HashMap.html#method.try_reserve [`HashSet::try_reserve`]: https://doc.rust-lang.org/std/collections/hash_set/struct.HashSet.html#method.try_reserve [`String::try_reserve`]: https://doc.rust-lang.org/alloc/string/struct.String.html#method.try_reserve [`String::try_reserve_exact`]: https://doc.rust-lang.org/alloc/string/struct.String.html#method.try_reserve_exact [`Vec::try_reserve`]: https://doc.rust-lang.org/std/vec/struct.Vec.html#method.try_reserve [`Vec::try_reserve_exact`]: https://doc.rust-lang.org/std/vec/struct.Vec.html#method.try_reserve_exact [`VecDeque::try_reserve`]: https://doc.rust-lang.org/std/collections/struct.VecDeque.html#method.try_reserve [`VecDeque::try_reserve_exact`]: https://doc.rust-lang.org/std/collections/struct.VecDeque.html#method.try_reserve_exact [`Iterator::map_while`]: https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.map_while [`iter::MapWhile`]: https://doc.rust-lang.org/std/iter/struct.MapWhile.html [`proc_macro::is_available`]: https://doc.rust-lang.org/proc_macro/fn.is_available.html [`Command::get_program`]: https://doc.rust-lang.org/std/process/struct.Command.html#method.get_program [`Command::get_args`]: https://doc.rust-lang.org/std/process/struct.Command.html#method.get_args [`Command::get_envs`]: https://doc.rust-lang.org/std/process/struct.Command.html#method.get_envs [`Command::get_current_dir`]: https://doc.rust-lang.org/std/process/struct.Command.html#method.get_current_dir [`CommandArgs`]: https://doc.rust-lang.org/std/process/struct.CommandArgs.html [`CommandEnvs`]: https://doc.rust-lang.org/std/process/struct.CommandEnvs.html

…accidentally been removed in rust-lang#89597. Also describe vtables as structs with a field for each entry.

…debuginfo-regression, r=wesleywiser debuginfo: Fix DW_AT_containing_type vtable debuginfo regression This PR brings back the `DW_AT_containing_type` attribute for vtables after it has accidentally been removed in rust-lang#89597. It also implements a more accurate description of vtables. Instead of describing them as an array of void pointers, the compiler will now emit a struct type description with a field for each entry of the vtable. r? `@wesleywiser` This PR should fix issue rust-lang#93164. ~~The PR is blocked on rust-lang#93154 because both of them modify the `codegen/debug-vtable.rs` test case.~~

…debuginfo-regression, r=wesleywiser debuginfo: Fix DW_AT_containing_type vtable debuginfo regression This PR brings back the `DW_AT_containing_type` attribute for vtables after it has accidentally been removed in rust-lang#89597. It also implements a more accurate description of vtables. Instead of describing them as an array of void pointers, the compiler will now emit a struct type description with a field for each entry of the vtable. r? ``@wesleywiser`` This PR should fix issue rust-lang#93164. ~~The PR is blocked on rust-lang#93154 because both of them modify the `codegen/debug-vtable.rs` test case.~~

rust-highfive assigned wesleywiser Oct 6, 2021

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michaelwoerister force-pushed the improve-vtable-debuginfo branch from d58cc76 to 6ffce8b Compare October 6, 2021 14:46

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michaelwoerister force-pushed the improve-vtable-debuginfo branch from 6ffce8b to f20737f Compare October 7, 2021 10:21

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Create more accurate debuginfo for vtables.

61c5a6d

Before this commit all vtables would have the same name "vtable" in debuginfo. Now they get a name that identifies the implementing type and the trait that is being implemented.

michaelwoerister force-pushed the improve-vtable-debuginfo branch from f20737f to 61c5a6d Compare October 8, 2021 08:34

wesleywiser approved these changes Oct 9, 2021

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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 Oct 9, 2021

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Debuginfo for windows-msvc treats () as tuple$<> #89704

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camelid added A-debuginfo Area: Debugging information in compiled programs (DWARF, PDB, etc.) T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Oct 11, 2021

bors added the merged-by-bors This PR was explicitly merged by bors. label Oct 11, 2021

bors merged commit 9a75781 into rust-lang:master Oct 11, 2021

rustbot added this to the 1.57.0 milestone Oct 11, 2021

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cargo fails to build on Windows with nightly #90019

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rust 1.57.0 regressed DWARF for trait objects #93164

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debuginfo: Fix DW_AT_containing_type vtable debuginfo regression #93503

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Create more accurate debuginfo for vtables. #89597

Create more accurate debuginfo for vtables. #89597

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Create more accurate debuginfo for vtables. #89597

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