Add cdac-dump-inspect script for ad-hoc dump analysis#127031
Merged
max-charlamb merged 5 commits intodotnet:mainfrom Apr 24, 2026
Merged
Add cdac-dump-inspect script for ad-hoc dump analysis#127031max-charlamb merged 5 commits intodotnet:mainfrom
max-charlamb merged 5 commits intodotnet:mainfrom
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Pull request overview
Adds an ad-hoc developer tool under src/native/managed/cdac/scripts to inspect .NET crash dumps using ClrMD + the cDAC reader, intended to quickly validate contract descriptor / thread / stack-walk behavior without WinDbg/SOS.
Changes:
- Introduces
cdac-dump-inspectconsole app (descriptor,threads,stackscommands) that loads a dump via ClrMD and queries cDAC contracts. - Adds a PowerShell wrapper to build and run the tool using the repo-local
.dotnet. - Adds scripts-area documentation describing prerequisites, usage, and examples.
Reviewed changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.
| File | Description |
|---|---|
| src/native/managed/cdac/scripts/cdac-dump-inspect.ps1 | Wrapper to build/run the inspector using the repo-local SDK. |
| src/native/managed/cdac/scripts/cdac-dump-inspect.csproj | New tool project referencing cDAC reader/contracts and ClrMD. |
| src/native/managed/cdac/scripts/cdac-dump-inspect.cs | Main implementation for descriptor/thread/stack inspection. |
| src/native/managed/cdac/scripts/README.md | Usage docs for the scripts folder and the new tool. |
steveisok
approved these changes
Apr 17, 2026
Add a developer tool for inspecting .NET crash dumps using ClrMD and the cDAC. Supports three commands: - descriptor: print the full contract descriptor (contracts, types, globals) - threads: list managed threads with OS ID and state - stacks: walk managed stacks showing instruction pointers and method descriptors Includes a PowerShell wrapper for easy invocation, README documentation, cycle detection for corrupt thread lists, and descriptor size validation. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
The GetTargetThreadContextDelegate follows HRESULT convention where 0 means success. Returning buffer.Length (912) caused TryGetThreadContext to treat every call as a failure, breaking stack walking. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
- Add Test-Path check for repo-local SDK in PowerShell wrapper - Fix relative link to contract descriptor doc (off by one level) - Validate DataReader.Read return values for short/failed reads - Add null check for descriptor pointer - Print full exception (ex.ToString()) instead of just ex.Message Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
- Use System.CommandLine for proper CLI argument parsing - Split into separate files: Program.cs, DescriptorCommand.cs, ThreadsCommand.cs, StacksCommand.cs, DumpHelpers.cs, ParsedDescriptor.cs - Add recursive sub-descriptor traversal and merge conflict detection - Resolve indirect globals through pointer data with dereferenced values - Fix read callback to return 0/-1 instead of byte count - Fix write callback to return -1 instead of throwing - Use explicit module allow-list with NativeAOT fallback - Fall back to dotnet on PATH when repo-local SDK is unavailable - Address all PR review feedback Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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- Check export before FileName to handle modules with null FileName - Validate magic bytes (DNCCDAC) in TryReadDescriptor - Cap pointerDataCount at 1024 and check null pointerDataAddr - Use ulong arithmetic for pointer data offset to prevent overflow - Validate full JSON read and catch parse exceptions gracefully - Remove misleading pointer dereference from indirect global display Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Note
This PR was authored with the help of Copilot.
Summary
Add a developer tool for inspecting .NET crash dumps using ClrMD and the cDAC (contract-based Data Access). This provides a quick way to verify cDAC functionality against real dumps without needing WinDbg or SOS.
Commands
descriptorthreadsstacksUsage
Or directly with dotnet run:
Architecture
The tool uses
System.CommandLinefor CLI parsing (matchingcdac-build-toolconventions) and is split into separate files for extensibility:Program.csRootCommandand subcommand registrationDescriptorCommand.csdescriptorcommand — recursive sub-descriptor traversal, merge conflict detectionThreadsCommand.csthreadscommandStacksCommand.csstackscommandDumpHelpers.csFindContractDescriptor,CreateCdacTargetParsedDescriptor.csParsedDescriptorrecord typecdac-dump-inspect.ps1dotneton PATHREADME.mdKey features
-> *0x...)DotNetRuntimeContractDescriptorexport when not in a known CoreCLR moduledotneton PATH, not just the repo-local SDK