5 files changed, 49 insertions, 8 deletions

diff --git a/lld/COFF/Config.h b/lld/COFF/Config.h
index 67f6034b0fa4..c8554e1435aa 100644
--- a/lld/COFF/Config.h
+++ b/lld/COFF/Config.h
@@ -22,13 +22,13 @@ namespace coff {
 
 using llvm::COFF::WindowsSubsystem;
 using llvm::StringRef;
-class Defined;
+struct Symbol;
 
 // Represents an /export option.
 struct Export {
   StringRef Name;
   StringRef ExtName;
-  Defined *Sym = nullptr;
+  Symbol *Sym = nullptr;
   uint16_t Ordinal = 0;
   bool Noname = false;
   bool Data = false;
diff --git a/lld/COFF/DLL.cpp b/lld/COFF/DLL.cpp
index d44dd4b4a0b6..5dda97288dc7 100644
--- a/lld/COFF/DLL.cpp
+++ b/lld/COFF/DLL.cpp
@@ -419,8 +419,10 @@ public:
   size_t getSize() const override { return Size * 4; }
 
   void writeTo(uint8_t *Buf) override {
-    for (Export &E : Config->Exports)
-      write32le(Buf + FileOff + E.Ordinal * 4, E.Sym->getRVA());
+    for (Export &E : Config->Exports) {
+      auto *D = cast<Defined>(E.Sym->Body);
+      write32le(Buf + FileOff + E.Ordinal * 4, D->getRVA());
+    }
   }
 
 private:
diff --git a/lld/COFF/Driver.cpp b/lld/COFF/Driver.cpp
index 649ddfb39460..12cff8a4f9af 100644
--- a/lld/COFF/Driver.cpp
+++ b/lld/COFF/Driver.cpp
@@ -566,6 +566,20 @@ bool LinkerDriver::link(llvm::ArrayRef<const char *> ArgsArr) {
       break;
   }
 
+  // Windows specific -- resolve dllexported symbols.
+  for (Export &E : Config->Exports) {
+    StringRef Name;
+    Symbol *Sym;
+    std::tie(Name, Sym) = Symtab.findMangled(E.Name);
+    if (!Sym) {
+      llvm::errs() << "exported symbol is not defined: " << E.Name << "\n";
+      return false;
+    }
+    if (E.Name != Name)
+      Symtab.rename(E.Name, Name);
+    E.Sym = Sym;
+  }
+
   // Make sure we have resolved all symbols.
   if (Symtab.reportRemainingUndefines())
     return false;
@@ -593,12 +607,9 @@ bool LinkerDriver::link(llvm::ArrayRef<const char *> ArgsArr) {
     writeImportLibrary();
 
   // Windows specific -- fix up dllexported symbols.
-  if (!Config->Exports.empty()) {
-    for (Export &E : Config->Exports)
-      E.Sym = Symtab.find(E.Name);
+  if (!Config->Exports.empty())
     if (fixupExports())
       return false;
-  }
 
   // Windows specific -- Create a side-by-side manifest file.
   if (Config->Manifest == Configuration::SideBySide)
diff --git a/lld/COFF/SymbolTable.cpp b/lld/COFF/SymbolTable.cpp
index b823ce9eacb5..831ab7d8a7ee 100644
--- a/lld/COFF/SymbolTable.cpp
+++ b/lld/COFF/SymbolTable.cpp
@@ -15,6 +15,7 @@
 #include "llvm/LTO/LTOCodeGenerator.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
+#include <utility>
 
 using namespace llvm;
 
@@ -173,6 +174,28 @@ Defined *SymbolTable::find(StringRef Name) {
   return nullptr;
 }
 
+// Find a given symbol or its mangled symbol.
+std::pair<StringRef, Symbol *> SymbolTable::findMangled(StringRef S) {
+  auto It = Symtab.find(S);
+  if (It != Symtab.end()) {
+    Symbol *Sym = It->second;
+    if (isa<Defined>(Sym->Body))
+      return std::make_pair(S, Sym);
+  }
+
+  // In Microsoft ABI, a non-member function name is mangled this way.
+  std::string Prefix = ("?" + S + "@@Y").str();
+  for (auto I : Symtab) {
+    StringRef Name = I.first;
+    Symbol *Sym = I.second;
+    if (!Name.startswith(Prefix))
+      continue;
+    if (isa<Defined>(Sym->Body))
+      return std::make_pair(Name, Sym);
+  }
+  return std::make_pair(S, nullptr);
+}
+
 std::error_code SymbolTable::resolveLazy(StringRef Name) {
   auto It = Symtab.find(Name);
   if (It == Symtab.end())
diff --git a/lld/COFF/SymbolTable.h b/lld/COFF/SymbolTable.h
index a1cf3408271f..62f14b09f525 100644
--- a/lld/COFF/SymbolTable.h
+++ b/lld/COFF/SymbolTable.h
@@ -52,6 +52,11 @@ public:
   // different symbol). Returns a nullptr if not found.
   Defined *find(StringRef Name);
 
+  // Find a symbol assuming that Name is a function name.
+  // Not only a given string but its mangled names (in MSVC C++ manner)
+  // will be searched.
+  std::pair<StringRef, Symbol *> findMangled(StringRef Name);
+
   // Windows specific -- `main` is not the only main function in Windows.
   // You can choose one from these four -- {w,}{WinMain,main}.
   // There are four different entry point functions for them,