[PATCH] D136762: [LLD][COFF] Survive empty PCH signature

[Alexandre Ganea via Phabricator via llvm-commits]

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While trying to use LLD with the Unreal Engine - which happens to heavily use PCH files - it was failing with "error: xxx.obj claims to be a PCH object, but does not have a valid signature". It seems recent versions of MSVC (or at least the one we use) do not generate the PCH signature in the S_OBJNAME record anymore. Instead we need to parse the entire .PCH.OBJ file until we reach the LF_ENDPRECOMP record, which contains a valid PCH signature. The code already was able to survive without that, by falling back to name lookup, but it's more reliable to use the `precompSourceMappings` map for matching the corresponding PCH file.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D136762

Files:
  lld/COFF/DebugTypes.cpp
  lld/test/COFF/precomp-link.test

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