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Capture macOS native runtime crashes for diagnosis - #7659
A macOS arm64 unit-test process exited 139 before reporting tests, leaving only an unsymbolicated native stack. Enable heap crash dumps for the macOS modular pipeline when a recipient certificate is configured, encrypt them before upload even when the pipeline fails, and retain encrypted artifacts for seven days. Document equivalent local capture commands.
Refs #7434. This prepares diagnosis of a recurrence; it does not establish or fix the runtime fault, so the issue remains open.
Validation: current main unit suite on SDK 10.0.403 / runtime 10.0.14: 935 total, 932 succeeded, 3 skipped. A standalone FailFast probe using the configured dump variables exited 134 and successfully wrote a 370,430,104-byte heap dump on macOS arm64. git diff --check passed. Hosted artifact upload will be validated by CI; actionlint is unavailable locally.
Investigation: the archived 2026-11-03 crash confirms SIGSEGV at 0x20 in MethodTable::CheckRunClassInitThrowing, called by GetThreadStaticsByIndex. dotnet/runtime#132691 has a similar stack but was reportedly fixed by 10.0.12, before the runtime in this report; it is not sufficient evidence to attribute this failure to that bug.
Security hardening: capture is disabled unless repository variable CRASH_DUMP_ENCRYPTION_CERT contains a PEM X.509 RSA recipient certificate. Administrators must configure its public certificate and retain the private key outside CI. Only CMS-encrypted dumps are uploaded; raw dumps are deleted even on encryption failure.
Additional validation: executed the workflow encryption shell with a generated RSA certificate and verified exact decryption; invalid-certificate and no-dump paths passed, including raw-dump cleanup and absence of uploadable artifacts on encryption failure. git diff --check passed. No C# changes; hosted macOS execution remains for CI.
Summary by CodeRabbit
Documentation
Added guidance for capturing, decrypting, and preserving macOS crash diagnostics, including privacy precautions and evidence to retain.
Chores
macOS CI can capture crash dumps when an encryption certificate is configured. Dumps are encrypted before upload, and only encrypted files are retained for seven days; raw dumps are not uploaded. If encryption fails, the step fails and raw dumps are not uploaded.
No actionable comments were generated in the recent review.
Walkthrough
The macOS modularpipeline job conditionally captures .NET mini-dumps when CRASH_DUMP_ENCRYPTION_CERT is configured. It encrypts and uploads the dumps as CMS files. Workflow documentation describes capture, decryption, and handling.
When CRASH_DUMP_ENCRYPTION_CERT is configured, the macOS job enables .NET mini-dumps and writes them under $RUNNER_TEMP.
Encrypt, upload, and document dumps .github/workflows/dotnet.yml, .claude/docs/workflows.md
The workflow encrypts dumps as CMS files, removes temporary certificate and raw dump files, and uploads encrypted files with seven-day retention. The documentation describes capture conditions, failure handling, local decryption, and diagnostic handling.
sequenceDiagram
participant modularpipeline
participant DotNetRuntime
participant EncryptionStep
participant ArtifactUpload
modularpipeline->>DotNetRuntime: enable mini-dumps when certificate is configured
DotNetRuntime->>EncryptionStep: write dump files under RUNNER_TEMP
EncryptionStep->>ArtifactUpload: provide encrypted CMS files
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Possibly related issues
Issue 7434: The change adds macOS crash-dump capture for diagnosing the reported intermittent crash. It does not fix the runtime fault.
Merge Risk: Minimal · up to 02e8d
Crash dumps are configured for encrypted capture. No actionable merge-blocking risk remains identified; hosted macOS validation is still needed.
Pre-merge checks: 5
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The title "Capture macOS native runtime crashes for diagnosis" matches the main change. The PR enables .NET native minidumps in the macOS modular pipeline, encrypts them with OpenSSL CMS, and uploads …
Docstring Coverage
No eligible functions found in the changed files. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentat…
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Full details: Title check
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The title "Capture macOS native runtime crashes for diagnosis" matches the main change. The PR enables .NET native minidumps in the macOS modular pipeline, encrypts them with OpenSSL CMS, and uploads only the encrypted .cms files. The title is short, specific, and states the primary purpose.
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A rabbit heard the crash-dump call, And watched encrypted files take flight. The raw dumps left the runner’s care, CMS files rested safe overnight. Seven days of clues await, While carrots crunch beside the gate.
Recent review info
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Reviewing files that changed from the base of the PR and between 267e591 and 02e8d6a.
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.github/workflows/dotnet.yml
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The change is small and does what it says: it sets the DOTNET_DbgEnableMiniDump, DOTNET_DbgMiniDumpType and DOTNET_DbgMiniDumpName variables for macOS only, writes to an absolute path under $RUNNER_TEMP, and uploads with if: always(). The upload-artifact version matches the other steps in the file, and if-no-files-found: ignore keeps green runs quiet. The PR doesn't claim to fix #7434, and the docs don't overclaim the root cause.
Minor, non-blocking points:
Size: Type 2 dumps are large (your probe wrote about 370 MB). A repeated crash could upload several of them. Consider a DOTNET_DbgMiniDumpType=3 fallback if artifact quota becomes a problem. Compression is already on by default.
Scope: the env vars apply to every dotnet child process in the pipeline, including build tools. That's fine because dumps are only written on fatal faults, but a note in the workflow comment would help the next reader.
Docs: the local snippet only works from a shell with the vars set inline. That's correct as written. Adding ulimit -c isn't needed on macOS, since .NET writes the dump itself.
Adds certificate-gated macOS crash capture and encrypted artifacts retained for seven days.
macOS CI saves encrypted crash dumps when a certificate is set.
Diagram
%%{init: {'theme': 'neutral'}}%%
flowchart TD
A[Recipient certificate configured] --> B[Enable macOS crash dumps]
B --> C[Run pipeline]
C --> D[Encrypt available dumps]
D --> E[Delete raw dumps on step exit]
D --> F[Upload completed encrypted files]
F --> G[Retain for seven days]
The PR head now includes the encryption fix 50279ee and the clarification that all dotnet child processes inherit capture settings. Verified that GitHub's PR head matches the pushed branch. git diff --check passed for the comment change; the existing encryption round-trip and failure-path validation remains documented in the PR body. Keeping draft pending fresh reviews of this head.
The design holds up. Capture is opt-in behind a repository variable. Raw dumps are deleted by an EXIT trap, including when encryption fails. Only *.cms files are uploaded, and the half-written .tmp files are excluded by the glob. The docs match the workflow.
Non-blocking points:
openssl on macOS runners.openssl resolves to whichever binary is first on PATH. That is LibreSSL under /usr/bin unless Homebrew's OpenSSL is first. LibreSSL's cms support and -aes-256-cbc handling differ from OpenSSL 3. The PR says the encryption shell was tested locally, but hosted macOS is still unverified. I'd add a fail-fast check, for example openssl cms -help or openssl version echoed into the log. A missing cms command then fails clearly instead of silently producing no artifact.
Silent no-op when nothing is encrypted. If the cert is malformed and no dump exists, the loop never runs, so the cert is never validated. A misconfigured variable only shows up after a crash, which is the worst moment. Validating up front would help, for example openssl x509 -noout -in "$cert" in the enable step. That step would then fail early and disable capture.
Disk usage. Each dump was about 370 MB in the probe. Every crashing child process, including build tools, writes one. Encryption roughly doubles the footprint on the runner before cleanup. Consider a size check or an upload cap. The artifact retention is fine.
Authenticated encryption. CMS with -aes-256-cbc is not authenticated. That is acceptable for confidentiality of an artifact only you will decrypt. Mentioning that in the docs would be cheap.
I couldn't verify hosted macOS behaviour here. Otherwise this looks good to merge once CI shows the artifact upload working.
The outstanding Codex credential-exposure thread is fixed by 50279ee. Verified the workflow and replied with that commit; the thread is now resolved, matching the earlier Greptile disposition.
Claude's scope suggestion is implemented in 267e591: the workflow comment explicitly includes build tools and other dotnet children.
Claude's nonblocking OpenSSL diagnostics suggestion: retain the existing failure behavior. The encryption step uses set -euo pipefail, so an unavailable CMS command or unsupported cipher emits the command error and fails the step; it does not silently succeed when a dump needs encryption. Hosted macOS support remains unverified, as the PR body states.
Early certificate validation: retain lazy validation. An invalid certificate fails encryption and deletes raw dumps, and no raw dump is uploaded. With no dump there is no artifact to encrypt; eager configuration checking is optional hardening rather than a correctness requirement for this change.
Disk usage / a smaller dump fallback: retain heap dumps needed for this investigation. An arbitrary cap could discard the only useful crash evidence; no observed quota failure currently justifies losing that evidence. Seven-day retention remains in place.
CBC authentication: retain the documented confidentiality-only workflow. These artifacts are diagnostic input, not authenticated records; the encryption command explicitly selects CBC and decryption does not establish provenance.
No new code or push was necessary for this review cycle. Claude's current-head review passed (run 42063041325). Codex's current-head review request is still running; do not promote the draft using its older-head verdict. CodeQL run 42063036728 is also still running. All review surfaces were read, and the draft remains pending the current-head Codex verdict.
Update: Codex completed with no findings for 267e591, and Claude had already approved that head. Marked ready and verified the head is unchanged. Promotion started fresh Claude run 42063480175 and CI (.NET run 42063479268). Auto-merge remains unarmed until the promotion-triggered Claude review passes and its feedback is read. All existing review findings have dispositions and both inline threads are resolved. No source changes or local test reruns were needed.
Overall this is a careful, well-scoped diagnostic change. Capture is opt-in via a repo variable, raw dumps are never uploaded, the encryption step runs under always(), and the trap deletes raw dumps and the cert even when encryption fails. The PR description is also honest that it doesn't fix #7434.
Points to consider (none blocking):
Partial output on failure. If openssl fails midway, set -e aborts and leaves a *.cms.tmp file. The upload glob is *.cms, so it's never uploaded. That's correct, but it relies on the glob. Adding rm -rf "$RUNNER_TEMP/tunit-crash-dumps-encrypted" to the trap on failure would make this explicit.
Plaintext secrets in memory. Dumps are encrypted, but the doc correctly warns that they contain credentials. Anyone holding the private key can read them. It's worth stating who holds the key in the docs, or in the issue.
Tool availability.openssl cms on macOS runners depends on which openssl is first on PATH (LibreSSL vs Homebrew). You've tested locally, but if the hosted run fails, pinning /usr/bin/openssl or checking openssl version in the step would help diagnose it.
Env scope. Setting the DOTNET_Dbg* variables through GITHUB_ENV applies them to every later step, including build tools. That's documented in the comment. If dump volume becomes a problem, scope them to the pipeline step's env: instead. This isn't possible with a composite action unless it forwards the env, so the current approach is reasonable.
Artifact size. Heap dumps are ~370 MB each, and several can occur per run. This is a modest storage cost with 7-day retention, but you could cap the number of dumps encrypted.
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Actionable comments posted: 2
Fix comments: Fix CodeRabbit comments on this PR
Prompt to fix all issues
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only still-valid issues, skip the rest with a brief reason, keep changes
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Inline comments:
Review comments at @.github/workflows/dotnet.yml:
- Line 239: Install the cleanup trap before the certificate-writing step in the
workflow, so cleanup is registered even if the printf that writes
CRASH_DUMP_ENCRYPTION_CERT to the certificate file fails.
- Line 245: Update the OpenSSL CMS encryption command in the heap-dump workflow
to use streaming so large dumps are not buffered entirely in memory, and verify
that the workflow’s documented decryption command accepts the resulting streamed
output.
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Reviewing files that changed from the base of the PR and between 08f2aca and 267e591.
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.claude/docs/workflows.md
.github/workflows/dotnet.yml
Included review availability: This review used your included allowance. Your plan provides up to 8 included reviews per hour; 1 remain after this review.
Run 42063480175 completed successfully; the earlier wait no longer blocks this PR. Read its Claude review and all review surfaces. Fixed both new CodeRabbit findings in 02e8d6a and resolved their threads: install cleanup before the certificate write, and stream CMS encryption.
Validation: executed the extracted workflow shell; an 8 MiB binary round-trip using the documented decryption command matched exactly. Invalid certificate, certificate-write failure via /dev/full, and no-dump cases passed, including raw-dump cleanup. git diff --check passed. Local OpenSSL 4.1.0; hosted macOS remains for CI.
Disposition of the promotion-triggered Claude review's nonblocking suggestions: retain *.cms-only upload, which excludes partial *.cms.tmp output; these partial files contain encrypted data and runner teardown removes them. The docs already require keeping the private key outside CI and decrypted dumps private; key custody remains with the administrator configuring the certificate. OpenSSL command failures fail the step visibly; hosted compatibility remains to be validated. Keep the documented all-child-process scope and heap dumps needed for diagnosis rather than adding an arbitrary dump cap without observed quota pressure.
The PR remains ready with auto-merge unarmed pending fresh reviews of the new head. No change to #7434 is needed: this PR provides diagnostic capture and does not claim to fix its runtime fault.
The change is sound. Capture is opt-in through the CRASH_DUMP_ENCRYPTION_CERT variable, and raw dumps are never uploaded. The trap deletes them even when encryption fails. The .cms.tmp then mv pattern means the *.cms upload glob can't pick up a half-written file. if-no-files-found: ignore keeps runs without a crash quiet. I found no blocking issues.
Minor, non-blocking suggestions:
Dumps that appear after the encrypt step. The upload step's if only checks runner.os == 'macOS'. The encrypt step also requires the variable. That is harmless today because the glob is empty without the variable, but using the same condition on both steps would show the dependency.
Disk and artifact size. Type 2 dumps were about 370 MB in your probe. Several crashing child processes (build tools inherit the variables) could produce many large artifacts. If that becomes noisy, narrow the capture to the test host processes, or cap the number of dumps encrypted.
Encryption stops at the first failure.set -e aborts the loop at the first dump that fails to encrypt, so later dumps are lost. You may prefer to attempt every dump and fail at the end. The trap cleanup would still apply.
Docs. Say in workflows.md that the variable is a public certificate and not a secret. The docs already say the private key stays out of CI. One sentence on rotating the certificate would also help.
Approving from a design standpoint. The hosted macOS upload path can only be checked by CI, as the description says.
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A macOS arm64 unit-test process exited 139 before reporting tests, leaving only an unsymbolicated native stack. Enable heap crash dumps for the macOS modular pipeline when a recipient certificate is configured, encrypt them before upload even when the pipeline fails, and retain encrypted artifacts for seven days. Document equivalent local capture commands.
Refs #7434. This prepares diagnosis of a recurrence; it does not establish or fix the runtime fault, so the issue remains open.
Validation: current main unit suite on SDK 10.0.403 / runtime 10.0.14: 935 total, 932 succeeded, 3 skipped. A standalone FailFast probe using the configured dump variables exited 134 and successfully wrote a 370,430,104-byte heap dump on macOS arm64.
git diff --checkpassed. Hosted artifact upload will be validated by CI; actionlint is unavailable locally.Investigation: the archived 2026-11-03 crash confirms SIGSEGV at 0x20 in MethodTable::CheckRunClassInitThrowing, called by GetThreadStaticsByIndex. dotnet/runtime#132691 has a similar stack but was reportedly fixed by 10.0.12, before the runtime in this report; it is not sufficient evidence to attribute this failure to that bug.
Security hardening: capture is disabled unless repository variable
CRASH_DUMP_ENCRYPTION_CERTcontains a PEM X.509 RSA recipient certificate. Administrators must configure its public certificate and retain the private key outside CI. Only CMS-encrypted dumps are uploaded; raw dumps are deleted even on encryption failure.Additional validation: executed the workflow encryption shell with a generated RSA certificate and verified exact decryption; invalid-certificate and no-dump paths passed, including raw-dump cleanup and absence of uploadable artifacts on encryption failure.
git diff --checkpassed. No C# changes; hosted macOS execution remains for CI.Summary by CodeRabbit