DbgEngTTDAdapter::Start() never queries IDebugDataSpaces2, leaving it null for the whole TTD session
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Description
DbgEngTTDAdapter::Start() creates its own IDebugClient7 and queries the interfaces it needs, but it omits IDebugDataSpaces2. The base class only ever queries that interface in DbgEngAdapter::ConnectToDebugServerInternal() (core/adapters/dbgengadapter.cpp:333), and the TTD adapter never goes through that path — it opens the trace with OpenDumpFile() instead.
Result: m_debugDataSpaces2 stays nullptr for the entire TTD session, and any code that depends on it silently does nothing rather than failing visibly.
The reachable consequence today is DbgEngAdapter::GetMemoryMap(), which begins with:
if (!this->m_debugDataSpaces2)
return {};
so under TTD it returns an empty map without ever calling into dbgeng. That surfaces as the empty memory map widget in #1132 — though note that issue is not fixed by this: IDebugDataSpaces2::QueryVirtual is also unimplemented for TTD replay targets, so the walk fails even with a valid interface pointer (see the analysis in https://github.com/Vector35/debugger/issues/1132#issuecomment-5072450325). This is the separate, latent half of that investigation, worth fixing on its own so the interface is available when something needs it and so the null-pointer path stops masking real behavior.
Fix
Query IDebugDataSpaces2 in DbgEngTTDAdapter::Start() (and release it in Reset()). Also adds IDebugDataSpaces4, which unlike QueryVirtual does work on TTD traces — GetValidRegionVirtual, GetNextDifferentlyValidOffsetVirtual and GetOffsetInformation all function there and are useful for validating an address range — wired on both the live-debug and TTD paths.
Verification
No behavior change is expected for live DbgEng debugging (that path already queried IDebugDataSpaces2; IDebugDataSpaces4 is additive). Under TTD, m_debugDataSpaces2/4 become non-null.
Both QueryInterface(__uuidof(IDebugDataSpaces2), ...) and IDebugDataSpaces4 were confirmed to return S_OK against a TTD trace using the pinned WinDbg's dbgeng.dll (TTD 1.01.11, release 1.11.592.0) in a standalone harness. Note QUERY_DEBUG_INTERFACE throws on failure, so this matters: both interfaces have existed since the earliest dbgeng versions we support, and both were observed available.
Not yet built in-tree.
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First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start in core/adapters/dbgengadapter.cpp at ConnectToDebugServerInternal() and GetMemoryMap(), then locate DbgEngTTDAdapter::Start() and Reset(). Add the interface queries and cleanup described in the issue, preserve the existing live-debug behavior, and verify that both interfaces are available for TTD; the payload notes that an in-tree build has not yet been done.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- cpp
- Domain
- devtools, reverse-engineering
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Quiet
- Clarity
- Mostly clear
- Newbie friendliness
- 68/100