[PDB] Make our PDBs look more like MS PDBs.
When investigating bugs in PDB generation, the first step is
often to do the same link with link.exe and then compare PDBs.
But comparing PDBs is hard because two completely different byte
sequences can both be correct, so it hampers the investigation when
you also have to spend time figuring out not just which bytes are
different, but also if the difference is meaningful.
This patch fixes a couple of cases related to string table emission,
hash table emission, and the order in which we emit strings that
makes more of our bytes the same as the bytes generated by MS PDBs.
Differential Revision: https://reviews.llvm.org/D44810
llvm-svn: 328348
diff --git a/lld/COFF/PDB.cpp b/lld/COFF/PDB.cpp
index a13b900..2287dda 100644
--- a/lld/COFF/PDB.cpp
+++ b/lld/COFF/PDB.cpp
@@ -85,7 +85,12 @@
public:
PDBLinker(SymbolTable *Symtab)
: Alloc(), Symtab(Symtab), Builder(Alloc), TypeTable(Alloc),
- IDTable(Alloc), GlobalTypeTable(Alloc), GlobalIDTable(Alloc) {}
+ IDTable(Alloc), GlobalTypeTable(Alloc), GlobalIDTable(Alloc) {
+ // This isn't strictly necessary, but link.exe usually puts an empty string
+ // as the first "valid" string in the string table, so we do the same in
+ // order to maintain as much byte-for-byte compatibility as possible.
+ PDBStrTab.insert("");
+ }
/// Emit the basic PDB structure: initial streams, headers, etc.
void initialize(const llvm::codeview::DebugInfo &BuildId);
@@ -1066,7 +1071,6 @@
pdb::DbiStreamBuilder &DbiBuilder = Builder.getDbiBuilder();
DbiBuilder.setAge(BuildId.PDB70.Age);
DbiBuilder.setVersionHeader(pdb::PdbDbiV70);
- ExitOnErr(DbiBuilder.addDbgStream(pdb::DbgHeaderType::NewFPO, {}));
}
void PDBLinker::addSectionContrib(pdb::DbiModuleDescriptorBuilder &LinkerModule,