[PATCH] D122372: [lld][COFF] Fix TypeServerSource lookup on GUID collisions

[Sylvain Audi via Phabricator via llvm-commits]

saudi added inline comments.


================
Comment at: lld/COFF/DebugTypes.cpp:67
+    // a path lookup fallback which works fine - but is slower.
+    if (Guid != InvalidGuid) {
+      auto it = ctx.typeServerSourceMappings.emplace(Guid, this);
----------------
aganea wrote:
> I'm starting to wonder if we really need this `if`. The fact that the bug is raised with a `FF FF...` guid is just an implementation artefact. The issue would still happen if two PDBs with different paths but same GUIDs (like in my example) are loaded during a link session.
With this approach, the idea is that we still trust the unicity of Guids with just one exception for the special case encountered in Microsoft's system PDBs;  I tend to think it's valid.  

Except for that bug in those PDBs, I think that it's still safe to assume that Guids are really unique, and that if we find two PDBs with different paths but same Guid, it would be safe to assume it was just a pdb that was copied, which can very well happen.  


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D122372/new/

https://reviews.llvm.org/D122372