1 files changed, 82 insertions, 1 deletions
diff --git a/lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.cpp b/lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.cpp
index 8b3d775..75a8189 100644
--- a/lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.cpp
+++ b/lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.cpp
@@ -501,7 +501,11 @@ lldb::FunctionSP SymbolFileNativePDB::CreateFunction(PdbCompilandSymId func_id,
     return nullptr;
 
   PdbTypeSymId sig_id(proc.FunctionType, false);
-  Mangled mangled(proc.Name);
+
+  std::optional<llvm::StringRef> mangled_opt = FindMangledSymbol(
+      SegmentOffset(proc.Segment, proc.CodeOffset), proc.FunctionType);
+  Mangled mangled(mangled_opt.value_or(proc.Name));
+
   FunctionSP func_sp = std::make_shared<Function>(
       &comp_unit, toOpaqueUid(func_id), toOpaqueUid(sig_id), mangled,
       func_type.get(), func_addr,
@@ -2662,6 +2666,83 @@ SymbolFileNativePDB::GetContextForType(TypeIndex ti) {
   return ctx;
 }
 
+std::optional<llvm::StringRef>
+SymbolFileNativePDB::FindMangledFunctionName(PdbCompilandSymId func_id) {
+  const CompilandIndexItem *cci =
+      m_index->compilands().GetCompiland(func_id.modi);
+  if (!cci)
+    return std::nullopt;
+
+  CVSymbol sym_record = cci->m_debug_stream.readSymbolAtOffset(func_id.offset);
+  if (sym_record.kind() != S_LPROC32 && sym_record.kind() != S_GPROC32)
+    return std::nullopt;
+
+  ProcSym proc(static_cast<SymbolRecordKind>(sym_record.kind()));
+  cantFail(SymbolDeserializer::deserializeAs<ProcSym>(sym_record, proc));
+
+  return FindMangledSymbol(SegmentOffset(proc.Segment, proc.CodeOffset),
+                           proc.FunctionType);
+}
+
+std::optional<llvm::StringRef>
+SymbolFileNativePDB::FindMangledSymbol(SegmentOffset so,
+                                       TypeIndex function_type) {
+  auto symbol = m_index->publics().findByAddress(m_index->symrecords(),
+                                                 so.segment, so.offset);
+  if (!symbol)
+    return std::nullopt;
+
+  llvm::StringRef name = symbol->first.Name;
+  // For functions, we might need to strip the mangled name. See
+  // StripMangledFunctionName for more info.
+  if (!function_type.isNoneType() &&
+      (symbol->first.Flags & PublicSymFlags::Function) != PublicSymFlags::None)
+    name = StripMangledFunctionName(name, function_type);
+
+  return name;
+}
+
+llvm::StringRef
+SymbolFileNativePDB::StripMangledFunctionName(const llvm::StringRef mangled,
+                                              PdbTypeSymId func_ty) {
+  // "In non-64 bit environments" (on x86 in pactice), __cdecl functions get
+  // prefixed with an underscore. For compilers using LLVM, this happens in LLVM
+  // (as opposed to the compiler frontend). Because of this, DWARF doesn't
+  // contain the "full" mangled name in DW_AT_linkage_name for these functions.
+  // We strip the mangling here for compatibility with DWARF. See
+  // llvm.org/pr161676 and
+  // https://learn.microsoft.com/en-us/cpp/build/reference/decorated-names#FormatC
+
+  if (!mangled.starts_with('_') ||
+      m_index->dbi().getMachineType() != PDB_Machine::x86)
+    return mangled;
+
+  CVType cvt = m_index->tpi().getType(func_ty.index);
+  PDB_CallingConv cc = PDB_CallingConv::NearC;
+  if (cvt.kind() == LF_PROCEDURE) {
+    ProcedureRecord proc;
+    if (llvm::Error error =
+            TypeDeserializer::deserializeAs<ProcedureRecord>(cvt, proc))
+      llvm::consumeError(std::move(error));
+    cc = proc.CallConv;
+  } else if (cvt.kind() == LF_MFUNCTION) {
+    MemberFunctionRecord mfunc;
+    if (llvm::Error error =
+            TypeDeserializer::deserializeAs<MemberFunctionRecord>(cvt, mfunc))
+      llvm::consumeError(std::move(error));
+    cc = mfunc.CallConv;
+  } else {
+    LLDB_LOG(GetLog(LLDBLog::Symbols), "Unexpected function type, got {0}",
+             cvt.kind());
+    return mangled;
+  }
+
+  if (cc == PDB_CallingConv::NearC || cc == PDB_CallingConv::FarC)
+    return mangled.drop_front();
+
+  return mangled;
+}
+
 void SymbolFileNativePDB::CacheUdtDeclarations() {
   for (CVType cvt : m_index->ipi().typeArray()) {
     switch (cvt.kind()) {