Use .drectve for MSVC DLL exports by AsakuraMizu · Pull Request #158294 · rust-lang/rust

AsakuraMizu · 2026-06-23T09:04:46Z

This is a continuation of #142568.

This fixes the i686 MSVC issue mentioned there: .def files accept undecorated names, but .drectve /EXPORT needs decorated symbol names. The public export name is preserved with EXPORTAS.

It's worth noting that EII with defaults now also works on MSVC.

rustbot · 2026-06-23T09:04:52Z

r? @oli-obk

rustbot has assigned @oli-obk.
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

Why was this reviewer chosen?

The reviewer was selected based on:

Owners of files modified in this PR: codegen, compiler
codegen, compiler expanded to 73 candidates
Random selection from 21 candidates

AsakuraMizu · 2026-06-24T05:23:20Z

Updated :)

@rustbot ready

oli-obk

@bors r+ rollup

View changes since this review

rust-bors · 2026-06-24T15:22:04Z

📌 Commit 4051560 has been approved by oli-obk

It is now in the queue for this repository.

bjorn3 · 2026-06-24T16:11:27Z

Maybe rollup=iffy? Linkage related things tend to be tricky.

oli-obk · 2026-06-24T17:51:53Z

@bors rollup=iffy reason=windows linker shenanigans

…, r=oli-obk Use .drectve for MSVC DLL exports This is a continuation of rust-lang#142568. This fixes the i686 MSVC issue mentioned there: `.def` files accept undecorated names, but `.drectve` `/EXPORT` needs decorated symbol names. The public export name is preserved with `EXPORTAS`. It's worth noting that EII with defaults now also works on MSVC.

…uwer Rollup of 17 pull requests Successful merges: - #153697 (Add arg splat experiment initial tuple impl) - #158294 (Use .drectve for MSVC DLL exports) - #158253 (codegen_ssa: multiply scalable vec size by `vscale`) - #158308 (Fix bug when rustdoc "go to only result" setting is not working as expected") - #158345 (Use `transmute_neo` in `assume_init`) - #158369 (std: abort when `resume_unwind` is called inside the panic hook) - #158374 (disallow tail calling extern "rust-call" functions) - #158380 (Revert "rebuild LLVM when `bootstrap.toml` config changes") - #154398 (Add test for async Send with PhantomData<*mut ()> + unsafe impl Send + dyn Trait) - #157181 (autodiff: stop always needing an alloca) - #158278 (autodiff - typtree cleanups) - #158311 (doc(unstable-book): fix typo "earier" -> "earlier" in default-visibility flag) - #158318 (Make normalization in a test case resilient to dist compilation) - #158338 (Reorganize `tests/ui/issues` [14/N]) - #158343 (Include `Item::const_stability` info in rustdoc JSON.) - #158355 (Fixup the refactoring errors in #156246) - #158390 (Fix: auto trait, const trait bound) Failed merges: - #155535 (export symbols: support macos/windows(32/64))

JonathanBrouwer · 2026-06-25T10:18:41Z

💔 I suspect this PR failed tests as part of a rollup
@bors r-

After fixing the problem, consider running a try job for the failed job before re-approving.

Link to failure: #158391 (comment)

rust-bors · 2026-06-25T10:18:48Z

This pull request was unapproved.

This PR was contained in a rollup (#158391), which was unapproved.

View changes since this unapproval

oli-obk · 2026-06-29T11:35:46Z

@bors try jobs=x86_64-msvc-1

Use .drectve for MSVC DLL exports try-job: x86_64-msvc-1

rust-bors · 2026-06-29T13:44:58Z

☀️ Try build successful (CI)
Build commit: fbb1950 (fbb195002ee8f5118ac156c1b0e56dd4b38aa343)
Base parent: 63f05e3 (63f05e3635171e7ac3f9ca78bad6c71052cda5a3)

oli-obk · 2026-06-29T13:46:22Z

@bors r+

rust-bors · 2026-06-29T13:46:25Z

📌 Commit c84bcbe has been approved by oli-obk

It is now in the queue for this repository.

Use .drectve for MSVC DLL exports This is a continuation of #142568. This fixes the i686 MSVC issue mentioned there: `.def` files accept undecorated names, but `.drectve` `/EXPORT` needs decorated symbol names. The public export name is preserved with `EXPORTAS`. It's worth noting that EII with defaults now also works on MSVC.

rust-bors · 2026-06-29T17:18:01Z

💔 Test for 2523831 failed: CI. Failed job:

auto - x86_64-msvc-ext1 (web logs, enhanced plaintext logs)

oli-obk · 2026-06-30T05:17:13Z

@bors try jobs=x86_64-msvc-ext1

Use .drectve for MSVC DLL exports try-job: x86_64-msvc-ext1

rust-bors · 2026-06-30T07:32:18Z

☀️ Try build successful (CI)
Build commit: a558f27 (a558f2706edcfaa8ced9843b1d3addc791a7c012)
Base parent: 0966944 (096694416a41840709140eb0fd0ca193d1a3e6ba)

AsakuraMizu · 2026-06-30T07:42:37Z

It seems that if we don't pass a /DEF:lib.def, link.exe won't generate a .lib file for an empty cdylib. lld, on the other hand, doesn't have this problem.

@rustbot ready

bjorn3 · 2026-06-30T09:19:39Z

This is missing a check that the symbols were actually exported. And maybe run it on all Windows targets?

View changes since the review

bjorn3 · 2026-06-30T09:25:55Z

                // .def file similar to MSVC one but without LIBRARY section
                // because LD doesn't like when it's empty
                writeln!(f, "EXPORTS")?;
-                for (symbol, kind) in symbols {
-                    let kind_marker = if *kind == SymbolExportKind::Data { " DATA" } else { "" };
-                    debug!("  _{symbol}");
+                for symbol in symbols {
+                    let kind_marker =
+                        if symbol.kind == SymbolExportKind::Data { " DATA" } else { "" };
+                    debug!("  _{}", symbol.name);
                    // Quote the name in case it's reserved by linker in some way
                    // (this accounts for names with dots in particular).
-                    writeln!(f, "  \"{symbol}\"{kind_marker}")?;
+                    writeln!(f, "  \"{}\"{kind_marker}", symbol.name)?;
                }
            };


Is this still necessary? I would assume the MinGW linker also respects /EXPORT in .drectve.

View changes since the review

rustbot · 2026-06-30T09:27:28Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

rustbot assigned oli-obk Jun 23, 2026

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jun 23, 2026

This comment has been minimized.

Sign in to view

bjorn3 reviewed Jun 23, 2026

View reviewed changes

Comment thread compiler/rustc_codegen_ssa/src/back/link.rs Outdated

bjorn3 reviewed Jun 23, 2026

View reviewed changes

Comment thread compiler/rustc_codegen_ssa/src/back/linker.rs

oli-obk added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 23, 2026

AsakuraMizu force-pushed the windows-drectve-export branch from b0075d5 to 4051560 Compare June 24, 2026 05:22

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jun 24, 2026

oli-obk approved these changes Jun 24, 2026

View reviewed changes

rust-bors Bot 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 24, 2026

JonathanBrouwer mentioned this pull request Jun 25, 2026

Rollup of 18 pull requests #158386

Closed

JonathanBrouwer mentioned this pull request Jun 25, 2026

Rollup of 17 pull requests #158389

Closed

JonathanBrouwer mentioned this pull request Jun 25, 2026

Rollup of 17 pull requests #158391

Closed

rust-bors Bot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jun 25, 2026

This comment has been minimized.

Sign in to view

rust-bors Bot pushed a commit that referenced this pull request Jun 29, 2026

Auto merge of #158294 - AsakuraMizu:windows-drectve-export, r=<try>

fbb1950

Use .drectve for MSVC DLL exports try-job: x86_64-msvc-1

rust-bors Bot 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 29, 2026

This comment has been minimized.

Sign in to view

rust-bors Bot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jun 29, 2026

rust-bors Bot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 30, 2026

This comment has been minimized.

Sign in to view

Preserve MSVC import libs for empty cdylibs

2f749bd

AsakuraMizu force-pushed the windows-drectve-export branch from c359042 to 2f749bd Compare June 30, 2026 05:10

This comment has been minimized.

Sign in to view

rust-bors Bot pushed a commit that referenced this pull request Jun 30, 2026

Auto merge of #158294 - AsakuraMizu:windows-drectve-export, r=<try>

a558f27

Use .drectve for MSVC DLL exports try-job: x86_64-msvc-ext1

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jun 30, 2026

bjorn3 requested changes Jun 30, 2026

View reviewed changes

rustbot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 30, 2026

rustbot added the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Jun 30, 2026

Uh oh!

Uh oh!

Conversation

AsakuraMizu commented Jun 23, 2026 • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

rustbot commented Jun 23, 2026

Uh oh!

This comment has been minimized.

Uh oh!

Uh oh!

AsakuraMizu commented Jun 24, 2026

Uh oh!

oli-obk left a comment • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

rust-bors Bot commented Jun 24, 2026

Uh oh!

bjorn3 commented Jun 24, 2026

Uh oh!

oli-obk commented Jun 24, 2026

Uh oh!

JonathanBrouwer commented Jun 25, 2026

Uh oh!

rust-bors Bot commented Jun 25, 2026

Uh oh!

oli-obk commented Jun 29, 2026

Uh oh!

This comment has been minimized.

rust-bors Bot commented Jun 29, 2026

Uh oh!

oli-obk commented Jun 29, 2026

Uh oh!

rust-bors Bot commented Jun 29, 2026

Uh oh!

This comment has been minimized.

This comment has been minimized.

rust-bors Bot commented Jun 29, 2026

Uh oh!

This comment has been minimized.

oli-obk commented Jun 30, 2026

Uh oh!

This comment has been minimized.

rust-bors Bot commented Jun 30, 2026

Uh oh!

AsakuraMizu commented Jun 30, 2026

Uh oh!

bjorn3 Jun 30, 2026 • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

bjorn3 Jun 30, 2026 • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

rustbot commented Jun 30, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

6 participants

AsakuraMizu commented Jun 23, 2026 •

edited by rustbot

Loading

oli-obk left a comment •

edited by rustbot

Loading

bjorn3 Jun 30, 2026 •

edited by rustbot

Loading

bjorn3 Jun 30, 2026 •

edited by rustbot

Loading