Implement support for DWARF version 5. #98350

pcwalton · 2022-06-21T19:13:59Z

DWARF version 5 brings a number of improvements over version 4. Quoting from
the announcement 1:

Version 5 incorporates improvements in many areas: better data compression,
separation of debugging data from executable files, improved description of
macros and source files, faster searching for symbols, improved debugging
optimized code, as well as numerous improvements in functionality and
performance.

On platforms where DWARF version 5 is supported (Linux, primarily), this commit
adds support for it behind a new -Z dwarf-version=5 flag.

r? @michaelwoerister

rust-highfive · 2022-06-21T19:14:02Z

⚠️ Warning ⚠️

These commits modify compiler targets. (See the Target Tier Policy.)

nikic · 2022-06-21T19:30:49Z

This should probably be an unstable -Z dwarf-version flag, unless you intend this to be insta-stable.

Is the max dwarf version logic really needed? It seems odd that there is no way to force a newer version if a target has this option set. It's reasonable that some platforms default to an older version, but I don't really see a reason to hard forbid using a newer one (for example, if I bring my own toolchain).

pcwalton · 2022-06-21T22:31:33Z

OK, I've switched the -C flag to a -Z flag, removed the max_dwarf_version field from the target info, and moved the documentation over to the unstable book.

nnethercote · 2022-06-21T23:42:01Z

Is this worth a perf run?

nikic

Looks reasonable to me.

src/test/assembly/dwarf5.rs

michaelwoerister · 2022-06-22T15:14:48Z

Thanks, @pcwalton! Looks good to me.

@bors r+

Is this worth a perf run?

As it currently is, the PR does not actually change the DWARF version being used for anything. It just adds the -Z flag for explicitly setting it. So, we shouldn't see a perf difference. But once this is merged it would be interesting to see how switching to v5 affects performance.

bors · 2022-06-22T15:14:50Z

📌 Commit 6c73840877fb5db8fd84c431d7078abe23cd8f87 has been approved by michaelwoerister

bors · 2022-06-22T15:14:51Z

🌲 The tree is currently closed for pull requests below priority 1000. This pull request will be tested once the tree is reopened.

pcwalton · 2022-06-22T18:41:25Z

Addressed comment. I think I need another review for bors to pick it up, r? @michaelwoerister

nikic · 2022-06-22T18:45:12Z

@bors r=michaelwoerister

bors · 2022-06-22T18:45:13Z

📌 Commit 42eeb58 has been approved by michaelwoerister

bors · 2022-06-22T18:45:14Z

🌲 The tree is currently closed for pull requests below priority 1000. This pull request will be tested once the tree is reopened.

pcwalton · 2022-06-23T22:12:57Z

Doesn't look related to this PR.

nnethercote · 2022-06-23T23:36:01Z

That failure is the one that caused the tree closure. Should be resolved now.

@bors retry

michaelwoerister · 2022-06-27T08:45:59Z

@bors retry

michaelwoerister · 2022-06-27T09:38:18Z

@bors r+

ehuss · 2022-07-08T23:28:53Z

@bors r=michaelwoerister

retry does not work when it has been unaccepted.

bors · 2022-07-08T23:28:55Z

📌 Commit 1e0ad0c has been approved by michaelwoerister

It is now in the queue for this repository.

Implement support for DWARF version 5. DWARF version 5 brings a number of improvements over version 4. Quoting from the announcement [1]: > Version 5 incorporates improvements in many areas: better data compression, > separation of debugging data from executable files, improved description of > macros and source files, faster searching for symbols, improved debugging > optimized code, as well as numerous improvements in functionality and > performance. On platforms where DWARF version 5 is supported (Linux, primarily), this commit adds support for it behind a new `-Z dwarf-version=5` flag. [1]: https://dwarfstd.org/Public_Review.php r? `@michaelwoerister`

Rollup of 7 pull requests Successful merges: - rust-lang#98350 (Implement support for DWARF version 5.) - rust-lang#98915 (Clarify deriving code) - rust-lang#98980 (fix ICE in ConstProp) - rust-lang#99008 (Adding suggestion for E0530) - rust-lang#99043 (Collapse some weirdly-wrapping derives) - rust-lang#99048 (Remove a string comparison about types) - rust-lang#99070 (Update integer_atomics tracking issue) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup

Rustc defaults to DWARF-2 on some targets, and DWARF-4 on others. However using -g with the C compiler yields whatever default version the C compiler prefers. One side effect is that the DWARF debug info shipped in some libraries with rustc itself (e.g. libcompiler_builtins and others) have recently switched to DWARF-5 as a side effect of upgrading the clang version used on rustc CI. (rust-lang/rust#98746) Ideally, the preferred DWARF version would be given by the rust compiler and/or cargo, but that's not the case at the moment, so the next best thing is something that aligns with the current defaults, although work in under way to add a rustc flag that would allow to pick the preferred DWARF version (rust-lang/rust#98350)

eddyb · 2022-07-12T10:30:59Z

compiler/rustc_codegen_llvm/src/debuginfo/mod.rs

-            if let Some(version) = sess.target.dwarf_version {
-                llvm::LLVMRustAddModuleFlag(
-                    self.llmod,
-                    llvm::LLVMModFlagBehavior::Warning,
-                    "Dwarf Version\0".as_ptr().cast(),
-                    version,
-                )
-            }
+            let dwarf_version =
+                sess.opts.debugging_opts.dwarf_version.unwrap_or(sess.target.default_dwarf_version);
+            llvm::LLVMRustAddModuleFlag(
+                self.llmod,
+                llvm::LLVMModFlagBehavior::Warning,
+                "Dwarf Version\0".as_ptr().cast(),
+                dwarf_version,
+            );


Could this have caused #99143? Looks like before this PR, we only ever set Dwarf Version on targets with Some in their dwarf_version, which based on the diff in this PR, wasn't the case for e.g. Windows (at least, there's probably more targets not covered by the ${OS}_base.rs files).

Alright that was confusing but I'm pretty sure (#99143 (comment)) that what's going on is even with debuginfo disabled for a binary, the standard library is getting statically linked in and we ship it w/ debuginfo.

I'm not sure what the best approach here would be, maybe just relying on the is_like_msvc check to effectively switch between CodeView and Dwarf Version (and never set both)?

fix dwarf debuginfo being used in addition to CodeView on windows Tackles the debuginfo size increase regression on windows to [unblock clippy](rust-lang#99143 (comment)) -- introduced by the DWARF5 support in rust-lang#98350 cc `@pcwalton.` r? `@eddyb` Fixes rust-lang#99143

Wyvern · 2022-07-15T19:39:41Z

Does macOS support DWARF5 at the moment?

Rustc defaults to DWARF-2 on some targets, and DWARF-4 on others. However using -g with the C compiler yields whatever default version the C compiler prefers. One side effect is that the DWARF debug info shipped in some libraries with rustc itself (e.g. libcompiler_builtins and others) have recently switched to DWARF-5 as a side effect of upgrading the clang version used on rustc CI. (rust-lang/rust#98746) Ideally, the preferred DWARF version would be given by the rust compiler and/or cargo, but that's not the case at the moment, so the next best thing is something that aligns with the current defaults, although work in under way to add a rustc flag that would allow to pick the preferred DWARF version (rust-lang/rust#98350)

Rust 1.64.0 introduced (unstable) support for the `-Zdwarf-version` flag, which allows to select DWARFv5, thus use it. Link: rust-lang/rust#103057 Link: rust-lang/rust#98350 Signed-off-by: Miguel Ojeda <[email protected]> Link: https://lore.kernel.org/r/[email protected]

Rust 1.64.0 introduced (unstable) support for the `-Zdwarf-version` flag, which allows to select DWARFv5, thus use it. Link: rust-lang/rust#103057 Link: rust-lang/rust#98350 Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Miguel Ojeda <[email protected]>

Rust 1.64.0 introduced (unstable) support for the `-Zdwarf-version` flag, which allows to select DWARFv5, thus use it. Link: rust-lang/rust#103057 Link: rust-lang/rust#98350 Reviewed-by: Alice Ryhl <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Miguel Ojeda <[email protected]>

rust-highfive assigned michaelwoerister Jun 21, 2022

rustbot added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Jun 21, 2022

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 21, 2022

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pcwalton force-pushed the dwarf5 branch from 28c2598 to eb94c30 Compare June 21, 2022 19:30

pcwalton force-pushed the dwarf5 branch 2 times, most recently from 3e54d38 to 6c73840 Compare June 21, 2022 22:30

nikic reviewed Jun 22, 2022

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src/test/assembly/dwarf5.rs Outdated Show resolved Hide resolved

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 Jun 22, 2022

pcwalton force-pushed the dwarf5 branch from 6c73840 to 42eeb58 Compare June 22, 2022 18:40

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kakkoyun mentioned this pull request Jun 23, 2022

symbolizer: Add support for DWARF5 symbolization parca-dev/parca#1186

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michaelwoerister closed this Jun 27, 2022

michaelwoerister reopened this Jun 27, 2022

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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 8, 2022

This was referenced Jul 9, 2022

Rollup of 7 pull requests #99077

Closed

Rollup of 7 pull requests #99078

Merged

bors merged commit fd4f11d into rust-lang:master Jul 9, 2022

rustbot added this to the 1.64.0 milestone Jul 9, 2022

ehuss mentioned this pull request Jul 11, 2022

Big file size regression on Windows #99143

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eddyb reviewed Jul 12, 2022

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lqd mentioned this pull request Jul 14, 2022

fix dwarf debuginfo being used in addition to CodeView on windows #99252

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This was referenced Oct 14, 2022

Tracking Issue for defaulting to DWARF 5 format #75890

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provide way to users to opt into DWARF5 on stable Rust #103057

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ojeda mentioned this pull request Feb 11, 2024

Rust unstable features needed for the kernel Rust-for-Linux/linux#2

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Implement support for DWARF version 5. #98350

Implement support for DWARF version 5. #98350

pcwalton commented Jun 21, 2022 •

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Implement support for DWARF version 5. #98350

Implement support for DWARF version 5. #98350

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