Fix variable shadowing bug in DacFreeRegionEnumerator::AddServerRegions by Copilot · Pull Request #125068 · dotnet/runtime

Copilot · 2026-03-02T18:52:50Z

Description

Variable shadowing bug in DacFreeRegionEnumerator::AddServerRegions — the inner loop over count_free_region_kinds reused i as its loop variable, shadowing the outer heap index i. After the inner loop, the AddSegmentList calls for freeable_soh_segment and freeable_uoh_segment passed count_free_region_kinds instead of the heap index.

Before:

for (int i = 0; i < GCHeapCount(); i++)
{
    // ...
    for (int i = 0; i < count_free_region_kinds; i++)  // shadows outer i
        AddSegmentList(heap.free_regions[i].head_free_region, FreeRegionKind::FreeRegion, i);

    AddSegmentList(heap.freeable_soh_segment, FreeRegionKind::FreeSohSegment, i);  // i == count_free_region_kinds, not heap index
    AddSegmentList(heap.freeable_uoh_segment, FreeRegionKind::FreeUohSegment, i);
}

After:

for (int i = 0; i < GCHeapCount(); i++)
{
    // ...
    for (int kind = 0; kind < count_free_region_kinds; kind++)
        AddSegmentList(heap.free_regions[kind].head_free_region, FreeRegionKind::FreeRegion, i);

    AddSegmentList(heap.freeable_soh_segment, FreeRegionKind::FreeSohSegment, i);
    AddSegmentList(heap.freeable_uoh_segment, FreeRegionKind::FreeUohSegment, i);
}

Renamed the inner loop variable to kind. All three AddSegmentList calls now correctly pass the heap index i.

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The inner for loop reused variable name 'i', shadowing the outer heap index loop variable. This caused AddSegmentList calls to receive count_free_region_kinds instead of the heap index for freeable_soh/uoh segments, and the region kind index instead of the heap index for free regions. Rename the inner loop variable to 'kind' and ensure all AddSegmentList calls pass 'i' (the heap index) as the last argument. Co-authored-by: max-charlamb <44248479+max-charlamb@users.noreply.github.com>

dotnet-policy-service · 2026-03-02T19:18:24Z

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Copilot

Pull request overview

This PR fixes a variable shadowing bug in DacFreeRegionEnumerator::AddServerRegions in the DAC (Data Access Component) layer used for GC heap inspection. The inner loop variable i shadowed the outer heap-index loop variable i, causing AddSegmentList calls for freeable_soh_segment and freeable_uoh_segment to pass count_free_region_kinds as the heap index instead of the actual heap index. This would corrupt the mem.Heap field in reported SOSMemoryRegion entries, misattributing SOH/UOH freeable segments to the wrong GC heap.

Changes:

Renamed the inner loop variable in AddServerRegions from i to kind, eliminating the shadowing and ensuring all three AddSegmentList calls correctly pass the outer heap index i.

max-charlamb · 2026-03-03T15:12:05Z

@copilot, can you analyze the CI failures?

rcj1 · 2026-03-03T15:16:43Z

@copilot, can you analyze the CI failures?

These seem completely unrelated to DAC things, perhaps copilot will just be able to fix them :)

Copilot · 2026-03-03T15:17:07Z

@copilot, can you analyze the CI failures?

CI has 2 failed jobs out of 80 total (78 passed) on build 1316693. None are related to this PR's change (src/coreclr/debug/daccess/request_svr.cpp):

Libraries Test Run checked coreclr linux x64 Release — System.Text.Json.Tests failed. Known flaky test tracked by System.Text.Json.Tests fails with GC hole assert #117186, OOM on System.Text.Json.Tests.Utf8JsonWriterTests.WriteRawLargeJsonToStreamWithoutFlushing #88272.
android-x64 Release AllSubsets_CoreCLR_Smoke — System.Net.Http.Functional.Tests and System.Net.WebSockets.Client.Tests failed. Known Android test issues tracked by [android][clr] No peer certificates when executing System.Net.Http.Functional.Tests on Android emulator #124526 (android HTTP cert failures) and System.Net.WebSockets.Client.Tests android fails #119520 / Android WebSocket failure #121518 (android WebSocket failures).

These failures are in completely unrelated areas (JSON serialization, HTTP networking, WebSockets) and have open "Known Build Error" tracking issues. The Build Analysis check is red because not all failures are automatically matched, but manual inspection confirms they're pre-existing. Safe to retry with /azp run runtime.

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helixr1107v0xdcypoyl9e7f.blob.core.windows.net
- Triggering command: /usr/bin/pwsh pwsh .github/skills/ci-analysis/scripts/Get-CIStatus.ps1 -BuildId 1316693 -ShowLogs (dns block)
https://api.github.com/graphql
- Triggering command: /usr/bin/gh gh pr view --json number,title,headRefName,url (http block)
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If you need me to access, download, or install something from one of these locations, you can either:

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max-charlamb · 2026-03-03T15:19:03Z

/ba-g test failures unrelated to change

Initial plan

25509ef

Copilot AI assigned Copilot and max-charlamb Mar 2, 2026

Copilot started work on behalf of max-charlamb March 2, 2026 18:52 View session

github-actions bot added the area-Infrastructure label Mar 2, 2026

github-project-automation bot added this to Runtime Infra Mar 2, 2026

Copilot AI changed the title ~~[WIP] Fix variable shadowing bug in DacFreeRegionEnumerator~~ Fix variable shadowing bug in DacFreeRegionEnumerator::AddServerRegions Mar 2, 2026

Copilot finished work on behalf of max-charlamb March 2, 2026 19:17

max-charlamb requested a review from leculver March 2, 2026 19:17

max-charlamb added area-Diagnostics-coreclr and removed area-Infrastructure labels Mar 2, 2026

max-charlamb requested a review from noahfalk March 2, 2026 19:17

max-charlamb marked this pull request as ready for review March 2, 2026 20:00

Copilot AI review requested due to automatic review settings March 2, 2026 20:00

Copilot started reviewing on behalf of max-charlamb March 2, 2026 20:01 View session

Copilot AI reviewed Mar 2, 2026

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noahfalk approved these changes Mar 3, 2026

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This was referenced Mar 3, 2026

Android WebSocket failure #121518

Open

[android][clr] No peer certificates when executing System.Net.Http.Functional.Tests on Android emulator #124526

Open

leculver approved these changes Mar 3, 2026

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Copilot started work on behalf of max-charlamb March 3, 2026 15:12 View session

Copilot finished work on behalf of max-charlamb March 3, 2026 15:17

Copilot started work on behalf of rcj1 March 3, 2026 15:17 View session

max-charlamb merged commit a8a0309 into main Mar 3, 2026
112 of 116 checks passed

max-charlamb deleted the copilot/fix-variable-shadowing-bug branch March 3, 2026 15:19

github-project-automation bot moved this to Done in Runtime Infra Mar 3, 2026

Copilot stopped work on behalf of rcj1 due to an error March 3, 2026 15:19
The session was cancelled by the user.

dotnet-maestro bot mentioned this pull request Mar 4, 2026

[main] Source code updates from dotnet/runtime dotnet/dotnet#5186

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Fix variable shadowing bug in DacFreeRegionEnumerator::AddServerRegions#125068

Fix variable shadowing bug in DacFreeRegionEnumerator::AddServerRegions#125068
max-charlamb merged 2 commits intomainfrom
copilot/fix-variable-shadowing-bug

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Pull request overview

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Copilot AI commented Mar 2, 2026 •

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