[PATCH] D41718: [lld] Correctly link S_FILESTATIC records

[Zachary Turner via Phabricator via llvm-commits]

zturner created this revision.
zturner added reviewers: aganea, rnk, ruiu.

`S_FILESTATIC` records are relatively rare, but cl does generate them.  In particular, it seems to only generate them with optimizations turned on and a file static is en-registered into a local variable.  The key piece of information in an `S_FILESTATIC` record that is not present in, for example, an `S_LOCAL` register, is the file (i.e. module) name that the file static comes from.

The prevailing theory is that this is so that if a function in module `a` which uses a file static defined in module `a` is then inlined into some other module `b`, there is a path back to the original `S_LDATA32` record.

In any case, although clang does not generate `S_FILESTATIC` records, it needs to be able to link them.  This was broken before, because `S_FILESTATIC` records contain a field which refers to the string table.  However, unlike other records which refer to the string table (but do so indirectly through the File Checksums table), `S_FILESTATIC` records point directly into the string table.

To handle this, during linking we need to merge in all strings from `S_FILESTATIC` records into the master PDB string table, and fixup their offsets in the linked `S_FILESTATIC` record.

This patch implements this.

This issue was originally discovered by Alexander Ganea as it was causing Visual Studio to crash.


https://reviews.llvm.org/D41718

Files:
  lld/COFF/PDB.cpp
  lld/test/COFF/Inputs/pdb-file-statics-a.yaml
  lld/test/COFF/Inputs/pdb-file-statics-b.yaml
  lld/test/COFF/pdb-file-static.test
  lld/test/COFF/pdb-file-static.yaml
  llvm/tools/llvm-pdbutil/DumpOutputStyle.cpp
  llvm/tools/llvm-pdbutil/DumpOutputStyle.h
  llvm/tools/llvm-pdbutil/MinimalSymbolDumper.cpp
  llvm/tools/llvm-pdbutil/MinimalSymbolDumper.h

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