Fix R2RDump ArgumentOutOfRangeException for composite LVB images

[Copilot]

In Large Version Bubble (LVB) composite R2R images, ManifestReferenceAssemblies contains more entries than ReadyToRunAssemblyHeaders — the manifest includes extra version-bubble assembly references beyond the actual component assemblies. TextDumper.DumpHeader iterated over the manifest list while indexing into the shorter headers list, throwing ArgumentOutOfRangeException.

Changes

• src/coreclr/tools/r2rdump/TextDumper.cs: Add a bounds check in the composite assembly loop to break when assemblyIndex >= ReadyToRunAssemblyHeaders.Count, preventing the out-of-range access when manifest references outnumber assembly headers.

foreach (string assemblyName in _r2r.ManifestReferenceAssemblies.OrderBy(kvp => kvp.Value).Select(kvp => kvp.Key))
{
+   if (assemblyIndex >= _r2r.ReadyToRunAssemblyHeaders.Count)
+       break;
    Guid mvid = _r2r.GetAssemblyMvid(assemblyIndex);
    ...
}

Original prompt

Create a pull request against dotnet/runtime by cherry-picking commit a6713ccb28fa831629168ef0a949ada7966921b5 onto upstream/main.

Context:

• The commit originates from an existing PR in jtschuster/runtime and contains the fix for R2RDump crashing with ArgumentOutOfRangeException for composite LVB images.
• The resulting PR should target the main branch of dotnet/runtime.

Requested work:

1. Check out a branch based on the latest upstream/main.
2. Cherry-pick commit a6713ccb28fa831629168ef0a949ada7966921b5 onto that branch.
3. Resolve any conflicts if needed while preserving the intent of the fix.
4. Push the branch to a fork suitable for opening a PR to dotnet/runtime.
5. Open a pull request against dotnet/runtime:main.

PR content guidance:

• Use a concise, descriptive title reflecting the R2RDump fix.
• Include a short description of the root cause and the bounds-check fix.
• Mention that the change prevents ArgumentOutOfRangeException when dumping composite Large Version Bubble images.

Please complete the PR creation end-to-end if permissions and repository setup allow.

The following is the prior conversation context from the user's chat exploration (may be truncated):

User: how do I change the target of this PR to be on dotnet/runtime

Assistant: You can’t directly retarget that existing PR from jtschuster/runtime to dotnet/runtime.

A GitHub PR is tied to the base repository it was opened against. Your current PR #27 is from:

• head: jtschuster:copilot/fix-r2rdump-argumentoutofrangeexception
• base: jtschuster/runtime:main

GitHub lets you change the base branch within the same repository, but not move a PR from one repository to a different repository. So you need to create a new PR against dotnet/runtime instead.

What to do

1. Make sure your branch is available in a fork of dotnet/runtime that you control.
   • Usually this means your fork is jtschuster/runtime, which you already have.
2. Open a new PR from:
   • head: jtschuster:copilot/fix-r2rdump-argumentoutofrangeexception
   • base: dotnet/runtime:main
3. Then close the old PR in jtschuster/runtime if you no longer need it.

Fastest way in the GitHub UI

If your branch exists on your fork, go to the PR creation page for dotnet/runtime and choose:

• base repository: dotnet/runtime
• base branch: main
• head repository: jtschuster/runtime
• compare branch: copilot/fix-r2rdump-argumentoutofrangeexception

GitHub docs for changing PR targets and base branches are here: Changing the base branch of a pull request and Creating a pull request from a fork.

If GitHub won’t show the branch

Push the branch to your fork explicitly, then open the new PR:

git checkout copilot/fix-r2rdump-argumentoutofrangeexception
git push -u origin copilot/fix-r2rdump-argumentoutofrangeexception

Then create the PR against dotnet/runtime.

Important caveat

If jtschuster/runtime is not actually a fork of dotnet/runtime, GitHub may not allow the cross-repo PR automatically in the UI. In that case:

1. Fork dotnet/runtime to your account.
2. Push this branch/cherry-pick these commits into that fork.
3. Open the PR from your fork to dotnet/runtime:main.

If you want, I can help you with the exact git commands to move this branch onto a proper fork and open the replacement PR.

User: Can you cherry-pick a6713cc on top of upstream/main and make a PR for it on dotnet/runtime?

Assistant: I'm waiting for your response to the pull-request tool prompt so I can continue.

This pull request was created from Copilot chat.

[jtschuster]

/azp run runtime-coreclr crossgen2-composite

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[Copilot]

Pull request overview

Fixes a crash in R2RDump when dumping composite Large Version Bubble (LVB) ReadyToRun images where manifest AssemblyRef entries outnumber actual component assembly headers.

Changes:

• Add a bounds check in the composite component-assembly dump loop to stop iterating once assemblyIndex reaches _r2r.ReadyToRunAssemblyHeaders.Count, preventing ArgumentOutOfRangeException.