[Trimming] Fix startup crash when TypeMapAssemblyTarget attribute survives but target assembly is fully trimmed by Copilot · Pull Request #130589 · dotnet/runtime

Copilot · 2026-07-12T21:51:19Z

In trimmed CoreCLR apps, a TypeMapAssemblyTarget attribute could survive trimming even when its named assembly was fully trimmed (all its TypeMap entries were conditional on trim targets that were never marked). At runtime, TypeMapLazyDictionary unconditionally calls Assembly.Load for every surviving attribute, crashing with FileNotFoundException.

Changes

Fix — ILLink TypeMapHandler.cs

TypeMapAssemblyTarget attributes are now only marked when their target assembly is also marked (has surviving entries or is otherwise kept).
Added _pendingAssemblyTargetsByAssembly: when a group is seen but the target assembly is not yet marked, the attribute is deferred here rather than immediately marked.
TriggerPendingAssemblyTargets() is internal and called only from MarkStep.MarkAssembly whenever an assembly is first marked — ensuring deferred attributes are flushed regardless of assembly visitation order.
A comment notes that this is a slight over-approximation: ideally the attribute would only be kept when the target assembly has a surviving TypeMapAttribute, but the added complexity is not justified for a narrow case.
If the target assembly can't be resolved in the linker input at all, the attribute is silently dropped (Assembly.Load would fail anyway).

Fix — MarkStep.cs

MarkAssembly calls _typeMapHandler.TriggerPendingAssemblyTargets(assembly) to flush any pending TypeMapAssemblyTarget attributes for the assembly being marked, regardless of the order in which TypeMap entries are visited.

Test

New test TypeMapAssemblyTargetRemovedWhenAllEntriesTrimmed with two dependency assemblies: a shared group-type assembly, and a conditional.dll with only conditional TypeMap entries (trim target never marked). Verifies via [RemovedAttributeInAssembly] and [RemovedAssembly] that the TypeMapAssemblyTarget attribute and the conditional assembly are both removed from the linked output.

…no surviving entries Co-authored-by: AaronRobinsonMSFT <30635565+AaronRobinsonMSFT@users.noreply.github.com>

….cs and assemblynative.cpp Co-authored-by: AaronRobinsonMSFT <30635565+AaronRobinsonMSFT@users.noreply.github.com>

AaronRobinsonMSFT · 2026-07-12T23:11:26Z

@copilot No changes should be done to CoreCLR itself. This is entirely a trimming issue. When the trimmer decides to remove a type based on the typemap reference algorithm, it should also remove the typemap attributes that reference it.

Co-authored-by: AaronRobinsonMSFT <30635565+AaronRobinsonMSFT@users.noreply.github.com>

Copilot · 2026-07-12T23:15:16Z

@copilot No changes should be done to CoreCLR itself. This is entirely a trimming issue. When the trimmer decides to remove a type based on the typemap reference algorithm, it should also remove the t...

Reverted all changes to assemblynative.cpp in commit $(git rev-parse --short HEAD). The fix is now purely in the ILLink trimmer (TypeMapHandler.cs): TypeMapAssemblyTarget attributes are only marked when their target assembly has at least one surviving TypeMap/TypeMapAssociation entry, so dangling attributes are removed at trim time rather than relying on any CoreCLR defense.

@copilot No changes should be done to CoreCLR itself. This is entirely a trimming issue. When the trimmer decides to remove a type based on the typemap reference algorithm, it should also remove the t...

Reverted all changes to assemblynative.cpp in commit 516910c2. The fix is now purely in the ILLink trimmer (TypeMapHandler.cs): TypeMapAssemblyTarget attributes are only marked when their target assembly has at least one surviving TypeMap/TypeMapAssociation entry, so dangling attributes are removed at trim time rather than relying on any CoreCLR defense.

github-actions · 2026-07-19T10:13:57Z

Workflow state for the Holistic Review Orchestrator.

{
  "version": 5,
  "last_dispatched_commit": "0d63a4015f5a83231ef59e93277ff29fa2c82e1e",
  "last_dispatched_base_ref": "main",
  "last_dispatched_base_sha": "0e7b627c152a3c1885d1db498d81d01de55a3391",
  "last_reviewed_commit": "0d63a4015f5a83231ef59e93277ff29fa2c82e1e",
  "last_reviewed_base_ref": "main",
  "last_reviewed_base_sha": "0e7b627c152a3c1885d1db498d81d01de55a3391",
  "last_recorded_worker_run_id": "29682980805",
  "review_attempt_commit": "",
  "review_attempt_base_ref": "",
  "review_attempt_count": 0,
  "max_review_attempts": 5,
  "review_history_format": "holistic-review-disclosure-v1",
  "review_history": [
    {
      "commit": "0d63a4015f5a83231ef59e93277ff29fa2c82e1e",
      "review_id": 4730589612
    }
  ]
}

github-actions

Holistic Review

Motivation: In trimmed CoreCLR apps a TypeMapAssemblyTarget attribute could survive trimming even when its named target assembly was fully trimmed away (all its TypeMap entries were conditional on trim targets that were never marked). At runtime TypeMapLazyDictionary unconditionally calls Assembly.Load for every surviving attribute, so the residual attribute caused a FileNotFoundException startup crash. This is a real, clearly motivated correctness fix.

Approach: TypeMapHandler no longer marks a TypeMapAssemblyTarget attribute unconditionally when its group is seen. Instead it resolves the target assembly during TypeMapResolver.Resolve, stores it alongside the pending entry, and defers the decision to MarkAssemblyTargetIfReady: the attribute is marked only if the target assembly is (or becomes) marked, dropped if the target assembly cannot be resolved, and deferred in _pendingAssemblyTargetsByAssembly otherwise. MarkStep.MarkAssembly flushes deferred entries via TriggerPendingAssemblyTargets when any assembly is first marked, which removes the visitation-order dependency the reviewer flagged. The over-approximation (keeping the attribute whenever the target assembly is marked for any reason, not strictly when it retains a surviving TypeMapAttribute) is a reasonable, well-commented tradeoff for a narrow case.

Summary: The change is correct, self-consistent, and low-risk. The new test TypeMapAssemblyTargetRemovedWhenAllEntriesTrimmed reproduces the scenario with a separate group-type assembly plus a conditional.dll referenced only by name string, and now asserts both [RemovedAssembly("conditional.dll")] and [RemovedAttributeInAssembly("test", typeof(TypeMapAssemblyTargetAttribute<AllConditionalGroupType>))], giving explicit verification of the intended behavior. Prior reviewer feedback from jtschuster (call TriggerPendingAssemblyTargets from MarkStep, remove the now-redundant belt-and-suspenders call, add the over-approximation comment) has all been incorporated. The pre-existing unvalidated ConstructorArguments[0] read in TypeMapResolver.Resolve was explicitly deferred by the maintainer to a separate change and is out of scope here. No actionable findings; the fix looks good.

Note

This review was generated by this repository's Holistic Review agentic workflow to complement the built-in Copilot review.

Generated by Holistic Review · 126.5 AIC · ⌖ 10.6 AIC · ⊞ 10K

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 8d5de1a2-a6e8-46fb-84d2-6a971d76419c

Copilot

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated no new comments.

sbomer

@copilot please add Reflection.TypeMapAssemblyTargetRemovedWhenAllEntriesTrimmed to ILTrimExpectedFailures.txt.

jtschuster · 2026-07-21T16:22:54Z

@copilot please add Reflection.TypeMapAssemblyTargetRemovedWhenAllEntriesTrimmed to ILTrimExpectedFailures.txt.

Co-authored-by: jtschuster <36744439+jtschuster@users.noreply.github.com>

Copilot

Copilot was unable to review this pull request because there is no eligible user to bill. To allow Copilot reviews on bot-authored pull requests, enable direct organization billing in your organization's Copilot settings.

Copilot · 2026-07-21T16:52:14Z

@copilot please add Reflection.TypeMapAssemblyTargetRemovedWhenAllEntriesTrimmed to ILTrimExpectedFailures.txt.

Added Reflection.TypeMapAssemblyTargetRemovedWhenAllEntriesTrimmed to ILTrimExpectedFailures.txt in commit a5eaec7c. The ILTrim ReflectionTests suite passes with the case recognized as an expected failure.

@copilot please add Reflection.TypeMapAssemblyTargetRemovedWhenAllEntriesTrimmed to ILTrimExpectedFailures.txt.

Added Reflection.TypeMapAssemblyTargetRemovedWhenAllEntriesTrimmed to ILTrimExpectedFailures.txt in commit a5eaec7c. The ILTrim ReflectionTests suite passes with the case recognized as an expected failure.

Initial plan

c30fd11

Copilot AI assigned Copilot and AaronRobinsonMSFT Jul 12, 2026

Copilot AI requested review from Copilot and removed request for Copilot July 12, 2026 21:51

github-project-automation Bot added this to AppModel Jul 12, 2026

Copilot AI linked an issue Jul 12, 2026 that may be closed by this pull request

[Trimming] Startup crash when TypeMapAssemblyTarget attribute kept but target assembly trimmed #130587

Closed

Copilot started work on behalf of AaronRobinsonMSFT July 12, 2026 21:51 View session

github-actions Bot added the area-AssemblyLoader-coreclr only use for closed issues label Jul 12, 2026

Fix TypeMapAssemblyTarget attribute removal when target assembly has …

dcf1d89

…no surviving entries Co-authored-by: AaronRobinsonMSFT <30635565+AaronRobinsonMSFT@users.noreply.github.com>

Copilot AI requested review from Copilot and removed request for Copilot July 12, 2026 22:23

dotnet-policy-service Bot added the linkable-framework Issues associated with delivering a linker friendly framework label Jul 12, 2026

Address code review: rename param, improve comments in TypeMapHandler…

2c9bb9f

….cs and assemblynative.cpp Co-authored-by: AaronRobinsonMSFT <30635565+AaronRobinsonMSFT@users.noreply.github.com>

Copilot AI requested review from Copilot and removed request for Copilot July 12, 2026 22:27

Copilot AI changed the title ~~[WIP] Fix startup crash caused by TypeMapAssemblyTarget attribute~~ [Trimming] Fix startup crash when TypeMapAssemblyTarget attribute survives but target assembly is fully trimmed Jul 12, 2026

Copilot AI requested a review from AaronRobinsonMSFT July 12, 2026 22:28

Copilot finished work on behalf of AaronRobinsonMSFT July 12, 2026 22:28

Copilot AI temporarily deployed to copilot-pat-pool July 12, 2026 23:09 Inactive

Copilot started work on behalf of AaronRobinsonMSFT July 12, 2026 23:12 View session

Revert CoreCLR assemblynative.cpp changes - fix is trimmer-only

516910c

Co-authored-by: AaronRobinsonMSFT <30635565+AaronRobinsonMSFT@users.noreply.github.com>

Copilot AI requested review from Copilot and removed request for Copilot July 12, 2026 23:15

Copilot finished work on behalf of AaronRobinsonMSFT July 12, 2026 23:15

AaronRobinsonMSFT requested review from MichalStrehovsky and jtschuster July 12, 2026 23:20

github-actions Bot reviewed Jul 19, 2026

View reviewed changes

Preserve TypeMap assembly target fast path

e25f2fb

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 8d5de1a2-a6e8-46fb-84d2-6a971d76419c

Copilot AI review requested due to automatic review settings July 20, 2026 21:02

Copilot started reviewing on behalf of jtschuster July 20, 2026 21:03 View session

Copilot AI reviewed Jul 20, 2026

View reviewed changes

jtschuster approved these changes Jul 20, 2026

View reviewed changes

jtschuster requested a review from jkoritzinsky July 20, 2026 21:08

sbomer approved these changes Jul 21, 2026

View reviewed changes

Copilot started work on behalf of jtschuster July 21, 2026 16:23 View session

Add TypeMap test to ILTrim expected failures

a5eaec7

Co-authored-by: jtschuster <36744439+jtschuster@users.noreply.github.com>

Copilot AI review requested due to automatic review settings July 21, 2026 16:50

Copilot AI reviewed Jul 21, 2026

Copilot finished work on behalf of jtschuster July 21, 2026 16:53

Copilot AI requested a review from jtschuster July 21, 2026 16:53

jtschuster approved these changes Jul 21, 2026

View reviewed changes

jtschuster requested a review from sbomer July 21, 2026 17:21

sbomer approved these changes Jul 21, 2026

View reviewed changes

jtschuster enabled auto-merge (squash) July 21, 2026 19:44

jtschuster merged commit 25b1e7a into main Jul 21, 2026
127 of 129 checks passed

jtschuster deleted the copilot/fix-startup-crash-trimming branch July 21, 2026 20:13

github-project-automation Bot moved this to Done in AppModel Jul 21, 2026

build-analysis Bot mentioned this pull request Jul 21, 2026

[ci-scan] Test failure: System.Security.Cryptography.X509Certificates.Tests.RevocationTests.AiaTests.AiaCompletionHasLimits #130947

Closed

This was referenced Jul 22, 2026

[main] Source code updates from dotnet/runtime dotnet/dotnet#7872

Merged

[release/11.0.1xx-preview7] Source code updates from dotnet/runtime dotnet/dotnet#7923

Merged

dotnet-milestone-bot Bot modified the milestones: 11.0-rc1, 11.0-preview7 Jul 24, 2026

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

[Trimming] Fix startup crash when TypeMapAssemblyTarget attribute survives but target assembly is fully trimmed - #130589

[Trimming] Fix startup crash when TypeMapAssemblyTarget attribute survives but target assembly is fully trimmed#130589
jtschuster merged 9 commits into
mainfrom
copilot/fix-startup-crash-trimming

Copilot AI commented Jul 12, 2026 •

edited

Loading

Uh oh!

AaronRobinsonMSFT commented Jul 12, 2026

Uh oh!

Copilot AI commented Jul 12, 2026 •

edited

Loading

Uh oh!

github-actions Bot commented Jul 19, 2026 •

edited

Loading

Uh oh!

github-actions Bot left a comment

Uh oh!

Copilot AI left a comment

Uh oh!

sbomer left a comment

Uh oh!

jtschuster commented Jul 21, 2026

Uh oh!

Copilot AI left a comment

Uh oh!

Copilot AI commented Jul 21, 2026 •

edited

Loading

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

6 participants

Uh oh!

Conversation

Copilot AI commented Jul 12, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Changes

Uh oh!

AaronRobinsonMSFT commented Jul 12, 2026

Uh oh!

Copilot AI commented Jul 12, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

github-actions Bot commented Jul 19, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

github-actions Bot left a comment

Choose a reason for hiding this comment

Holistic Review

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Uh oh!

sbomer left a comment

Choose a reason for hiding this comment

Uh oh!

jtschuster commented Jul 21, 2026

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Uh oh!

Copilot AI commented Jul 21, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

6 participants

Copilot AI commented Jul 12, 2026 •

edited

Loading

Copilot AI commented Jul 12, 2026 •

edited

Loading

github-actions Bot commented Jul 19, 2026 •

edited

Loading

Copilot AI commented Jul 21, 2026 •

edited

Loading