Implement GetIlCodeAndSig DacDbi API in cDAC

[Copilot]

Port the GetILCodeAndSig DacDbi entry point from the native DAC to the managed cDAC, returning the target-address/size of a method's IL and its local-variable signature token.

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[Copilot]

Pull request overview

Implements the managed cDAC path for GetILCodeAndSig, replacing an E_NOTIMPL fallback with metadata/loader-based IL lookup and signature-token extraction.

Changes:

• Adds IL header size/code-size helpers.
• Implements DacDbiImpl.GetILCodeAndSig.
• Adds metadata token and HRESULT constants needed by the implementation.

Show a summary per file

File	Description
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/HeaderReaderHelpers.cs	Adds helpers for IL header size and code size decoding.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/Dbi/DacDbiImpl.cs	Implements cDAC GetILCodeAndSig behavior.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/EcmaMetadataUtils.cs	Adds mdtSignature token type.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/CorDbHResults.cs	Adds CORDBG_E_FUNCTION_NOT_IL.

Copilot's findings

• Files reviewed: 4/4 changed files
• Comments generated: 3

[Copilot]

Copilot's findings

Comments suppressed due to low confidence (3)

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/Dbi/DacDbiImpl.cs:1361

• pLocalSigToken is pre-initialized to TokenType.mdtSignature (0x11000000). Native DAC initializes this out param to mdSignatureNil (0) and only sets a non-zero token when a LocalVarSigTok exists. Initializing to the token type mask yields an invalid token on success for methods without locals (and will mismatch the legacy DAC behavior).

            if (dwExactGenericArgsTokenIndex == 0)
            {
                // In a rare case of VS4Mac debugging VS4Mac ARM64 optimized code we get a null

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/Dbi/DacDbiImpl.cs:1371

• GetILCodeAndSig doesn’t validate that functionToken is actually a MethodDef token before using it with MetadataReader and the MethodDefToDesc lookup. Other methods in this type explicitly validate token type (e.g., GetActiveRejitILCodeVersionNode throws ArgumentException when the token type isn’t mdtMethodDef). Adding the same check here should help keep HRESULT behavior aligned with the native DAC (E_INVALIDARG for invalid tokens) and avoid BadImageFormat/other accidental failures.

                {
                    *pRetVal = rawToken;
                }
                else
                {
                    // The real generics type token is the MethodTable of the "this" object.

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/Dbi/DacDbiImpl.cs:1365

• GetILCodeAndSig now has a non-trivial managed implementation (metadata validation, MethodDesc mapping, IL header parsing) but there are no unit/integration tests exercising the new behavior (success path, non-IL methods -> CORDBG_E_FUNCTION_NOT_IL, methods without locals -> mdSignatureNil, etc.). This file already has targeted tests for other DacDbiImpl entry points, so adding coverage here would help prevent regressions and ensure behavior matches the native DAC.

        try
        {
            if (dwExactGenericArgsTokenIndex == 0)
            {
                // In a rare case of VS4Mac debugging VS4Mac ARM64 optimized code we get a null
                // generics argument token. We aren't sure why the token is null, it may be a bug
                // or it may be by design in the runtime. In the interest of time we are working
                // around the issue rather than investigating the root cause.
                if (rawToken == 0)

• Files reviewed: 4/4 changed files
• Comments generated: 3