Convert IDacDbiInterface to COM interface

[max-charlamb]

Summary

Converts IDacDbiInterface from a plain C++ abstract class into a proper COM interface, enabling future implementation in managed C# via the cDAC.

Changes

• IUnknown inheritance: IDacDbiInterface now inherits from IUnknown via MIDL_INTERFACE with GUID DB505C1B-A327-4A46-8C32-AF55A56F8E09
• Destroy → Release: Removed Destroy() method, replaced with standard COM Release() lifecycle in all callers
• QueryInterface/AddRef/Release: Added implementations to DacDbiInterfaceImpl
• Reference → Pointer params: Converted 5 methods with C++ reference parameters to pointer parameters for COM compatibility
• bool → BOOL: Converted 8 methods using C++ bool to COM-compatible BOOL (4-byte int)
• IDL definition: Added dacdbi.idl defining the full COM interface contract including inner callback interfaces (IStringHolder, IAllocator, IMetaDataLookup). Validated with MIDL compiler.

Motivation

This is Phase 1 of enabling the cDAC (contract-based Data Access Component) to implement IDacDbiInterface in managed C#, following the same pattern as ISOSDacInterface → SOSDacImpl. The prior PR #124836 converted all methods to return HRESULT; this PR completes the COM conversion.

Testing

Local build verified (daccess.lib, mscordbi.dll, mscordaccore.dll). IDL validated with MIDL compiler. Running CI for full validation.

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[Copilot]

Pull request overview

This PR converts IDacDbiInterface (DAC↔DBI contract) from a plain C++ abstract class to a COM-style interface (IUnknown + GUID), with the goal of enabling a future managed (C#) cDAC implementation and standard COM lifetime management.

Changes:

• Make IDacDbiInterface a COM interface (MIDL_INTERFACE, IUnknown base) and remove the custom Destroy() lifecycle method in favor of Release().
• Implement QueryInterface/AddRef/Release on DacDbiInterfaceImpl and update DBI call sites for the new pointer-based out params.
• Add dacdbi.idl describing the intended COM contract (including callback interfaces).

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/coreclr/debug/inc/dacdbiinterface.h	Converts IDacDbiInterface to MIDL_INTERFACE + IUnknown, removes Destroy(), adjusts several signatures for COM compatibility.
src/coreclr/debug/inc/dacdbi.idl	Adds an IDL definition for the full COM contract and callback interfaces.
src/coreclr/debug/di/rstype.cpp	Updates GetExactTypeHandle call to pass an out pointer.
src/coreclr/debug/di/rspriv.h	Updates forward-declaration to struct to match MIDL_INTERFACE expansion.
src/coreclr/debug/di/process.cpp	Updates metadata query call sites to use pointer out-params; switches DAC teardown from Destroy() to Release().
src/coreclr/debug/di/module.cpp	Updates metadata query call sites to use pointer out-params.
src/coreclr/debug/di/divalue.cpp	Updates exception stack frame query to pass DacDbiArrayList by pointer.
src/coreclr/debug/daccess/dacdbiimpl.h	Declares IUnknown methods and updates signatures to pointer out-params.
src/coreclr/debug/daccess/dacdbiimpl.cpp	Implements IUnknown methods; updates implementations for pointer out-params.

Comments suppressed due to low confidence (2)

src/coreclr/debug/daccess/dacdbiimpl.cpp:1201

• GetMetaDataFileInfoFromPEFile now takes pTimeStamp/pImageSize as pointers, but the implementation unconditionally dereferences them on the success path and also leaves them uninitialized when vmPEAssembly resolves to NULL. For COM-style APIs (and consistent with other methods in this file that return E_POINTER), please validate pTimeStamp/pImageSize (and other required out params like pResult) up-front, return E_POINTER when null, and ensure out values are always initialized on all return paths.

HRESULT DacDbiInterfaceImpl::GetMetaDataFileInfoFromPEFile(VMPTR_PEAssembly vmPEAssembly, DWORD * pTimeStamp, DWORD * pImageSize, IStringHolder* pStrFilename, OUT bool * pResult)
{
    DD_ENTER_MAY_THROW;

    HRESULT hr = S_OK;
    EX_TRY
    {

        DWORD dwDataSize;
        DWORD dwRvaHint;
        PEAssembly * pPEAssembly = vmPEAssembly.GetDacPtr();
        _ASSERTE(pPEAssembly != NULL);
        if (pPEAssembly == NULL)
        {
            *pResult = false;
        }

src/coreclr/debug/daccess/dacdbiimpl.cpp:3756

• GetStackFramesFromException now takes the DacDbiArrayList as a pointer, but the method doesn’t validate pDacStackFrames before dereferencing it (Alloc / operator[]). Please add an E_POINTER check at the top of the method (and consider initializing it to an empty list on success paths where there are 0 frames).

HRESULT DacDbiInterfaceImpl::GetStackFramesFromException(VMPTR_Object vmObject, DacDbiArrayList<DacExceptionCallStackData>* pDacStackFrames)
{
    DD_ENTER_MAY_THROW;

    HRESULT hr = S_OK;
    EX_TRY
    {

        PTR_Object objPtr = vmObject.GetDacPtr();

    #ifdef _DEBUG

[Copilot]

After removing Destroy() in favor of COM Release(), there’s still a stale reference to Destroy() in the FlushCache() notes earlier in this file ("besides Destroy"). Please update that comment to refer to Release() (or remove the parenthetical) so the interface contract stays accurate.

[Copilot]

GetExactTypeHandle switched from an out reference to an out pointer (pVmTypeHandle) but the implementation immediately dereferences it without validating. To match the rest of DacDbiInterfaceImpl’s COM-style behavior, please add a null check for pVmTypeHandle and return E_POINTER before writing through it.

[Copilot]

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 3 comments.

Comments suppressed due to low confidence (1)

src/coreclr/debug/daccess/dacdbiimpl.cpp:1190

• GetMetaDataFileInfoFromPEFile now takes multiple pointer parameters (pTimeStamp, pImageSize, pStrFilename, pResult) but does not validate them before dereferencing later in the method. This was previously safe with reference parameters; now a null argument will crash. Add E_POINTER checks (and consider setting outputs to safe defaults on failure paths).

HRESULT DacDbiInterfaceImpl::GetMetaDataFileInfoFromPEFile(VMPTR_PEAssembly vmPEAssembly, DWORD * pTimeStamp, DWORD * pImageSize, IStringHolder* pStrFilename, OUT BOOL * pResult)
{
    DD_ENTER_MAY_THROW;

    HRESULT hr = S_OK;

[Copilot]

GetStackFramesFromException changed its DacDbiArrayList parameter from a reference to a pointer, but the implementation dereferences pDacStackFrames unconditionally (Alloc / operator[]). This introduces a null-deref crash path; validate pDacStackFrames (and any other required pointer params) and return E_POINTER when null.

Suggested change

	{
	{
	if (pDacStackFrames == NULL)
	{
	ThrowHR(E_POINTER);
	}

[Copilot]

IsWinRTModule changed from an out reference to an out pointer (pIsWinRT) but still writes to it unconditionally. Add a null check and return E_POINTER when pIsWinRT is null (consistent with other APIs in this layer that validate out pointers).

[Copilot]

This IDL uses the Win32 HANDLE type in the method signature here, but the file only imports unknwn.idl and does not define/import HANDLE anywhere. This is likely to fail MIDL parsing/compilation; import an IDL that defines HANDLE (commonly wtypes.idl / objidl.idl) or add a local typedef for HANDLE in the dummy-type section.

[Copilot]

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

Comments suppressed due to low confidence (1)

src/coreclr/debug/daccess/dacdbiimpl.cpp:1219

• GetMetaDataFileInfoFromPEFile returns S_OK even when vmPEAssembly.GetDacPtr() is null, but in that path it only sets *pResult = FALSE and leaves *pTimeStamp, *pImageSize, and pStrFilename unchanged. Because these are out parameters, callers could observe stale values if they reuse variables/holders. Recommend explicitly zeroing timestamp/size and clearing the filename holder on the failure path.

HRESULT DacDbiInterfaceImpl::GetMetaDataFileInfoFromPEFile(VMPTR_PEAssembly vmPEAssembly, DWORD * pTimeStamp, DWORD * pImageSize, IStringHolder* pStrFilename, OUT BOOL * pResult)
{
    if (pTimeStamp == NULL || pImageSize == NULL || pStrFilename == NULL || pResult == NULL)
        return E_POINTER;

    DD_ENTER_MAY_THROW;

    HRESULT hr = S_OK;
    EX_TRY
    {

        DWORD dwDataSize;
        DWORD dwRvaHint;
        PEAssembly * pPEAssembly = vmPEAssembly.GetDacPtr();
        _ASSERTE(pPEAssembly != NULL);
        if (pPEAssembly == NULL)
        {
            *pResult = FALSE;
        }
        else
        {
        WCHAR wszFilePath[MAX_LONGPATH] = {0};
        DWORD cchFilePath = MAX_LONGPATH;
        bool ret = ClrDataAccess::GetMetaDataFileInfoFromPEFile(pPEAssembly,
                                                                *pTimeStamp,
                                                                *pImageSize,
                                                                dwDataSize,
                                                                dwRvaHint,
                                                                wszFilePath,
                                                                cchFilePath);

        pStrFilename->AssignCopy(wszFilePath);
        *pResult = ret;
        }

[Copilot]

DacDbiInterfaceImpl::QueryInterface dereferences iface without a null check. If a caller passes a null out-pointer (or uses it incorrectly), this will AV before you can return an HRESULT. Consider matching COM expectations here by returning E_POINTER when iface is null and (optionally) setting *iface = nullptr before any IID checks.

[Copilot]

IDacDbiInterface is now declared as a COM interface (inherits IUnknown via MIDL_INTERFACE), but the method declarations in this header still use plain virtual HRESULT Method(...) (no STDMETHODCALLTYPE / STDMETHOD macros), and several parameters still use nested callback types (e.g., IStringHolder, IAllocator, IMetaDataLookup) that do not inherit from IUnknown. This makes the C++ header's ABI and callback vtable layouts diverge from the COM contract in dacdbi.idl (and from what managed COM/C# would implement). To make the COM conversion complete/consistent, align the header with the IDL: use STDMETHODCALLTYPE/STDMETHOD-style declarations for all methods and switch callback parameters to IUnknown-derived COM interfaces (or provide typedef/adapters that preserve the same vtable layout as the IDL).

[Copilot]

dacdbi.idl defines callback interfaces (IDacDbiStringHolder/Allocator/MetaDataLookup) as IUnknown-derived COM interfaces and emits a COM ABI (STDMETHODCALLTYPE) for IDacDbiInterface. The native-facing header (dacdbiinterface.h) still uses non-IUnknown nested callback types and non-STDMETHODCALLTYPE method declarations, so the IDL contract and the actual native contract are not ABI-compatible. Either update the native header to match the IDL contract, or scope/label this IDL as "future" (not authoritative) to avoid consumers generating/using interop code against an interface that won’t work with the shipped header.