1 files changed, 38 insertions, 3 deletions
diff --git a/clang/lib/AST/MicrosoftMangle.cpp b/clang/lib/AST/MicrosoftMangle.cpp
index 8067c42dff5..d5332ba7db5 100644
--- a/clang/lib/AST/MicrosoftMangle.cpp
+++ b/clang/lib/AST/MicrosoftMangle.cpp
@@ -29,6 +29,7 @@
 #include "clang/Basic/TargetInfo.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Support/JamCRC.h"
+#include "llvm/Support/xxhash.h"
 #include "llvm/Support/MD5.h"
 #include "llvm/Support/MathExtras.h"
 
@@ -127,10 +128,10 @@ class MicrosoftMangleContextImpl : public MicrosoftMangleContext {
   llvm::DenseMap<const CXXRecordDecl *, unsigned> LambdaIds;
   llvm::DenseMap<const NamedDecl *, unsigned> SEHFilterIds;
   llvm::DenseMap<const NamedDecl *, unsigned> SEHFinallyIds;
+  SmallString<16> AnonymousNamespaceHash;
 
 public:
-  MicrosoftMangleContextImpl(ASTContext &Context, DiagnosticsEngine &Diags)
-      : MicrosoftMangleContext(Context, Diags) {}
+  MicrosoftMangleContextImpl(ASTContext &Context, DiagnosticsEngine &Diags);
   bool shouldMangleCXXName(const NamedDecl *D) override;
   bool shouldMangleStringLiteral(const StringLiteral *SL) override;
   void mangleCXXName(const NamedDecl *D, raw_ostream &Out) override;
@@ -238,6 +239,12 @@ public:
     return Result.first->second;
   }
 
+  /// Return a character sequence that is (somewhat) unique to the TU suitable
+  /// for mangling anonymous namespaces.
+  StringRef getAnonymousNamespaceHash() const {
+    return AnonymousNamespaceHash;
+  }
+
 private:
   void mangleInitFiniStub(const VarDecl *D, char CharCode, raw_ostream &Out);
 };
@@ -371,6 +378,34 @@ private:
 };
 }
 
+MicrosoftMangleContextImpl::MicrosoftMangleContextImpl(ASTContext &Context,
+                                                       DiagnosticsEngine &Diags)
+    : MicrosoftMangleContext(Context, Diags) {
+  // To mangle anonymous namespaces, hash the path to the main source file. The
+  // path should be whatever (probably relative) path was passed on the command
+  // line. The goal is for the compiler to produce the same output regardless of
+  // working directory, so use the uncanonicalized relative path.
+  //
+  // It's important to make the mangled names unique because, when CodeView
+  // debug info is in use, the debugger uses mangled type names to distinguish
+  // between otherwise identically named types in anonymous namespaces.
+  //
+  // These symbols are always internal, so there is no need for the hash to
+  // match what MSVC produces. For the same reason, clang is free to change the
+  // hash at any time without breaking compatibility with old versions of clang.
+  // The generated names are intended to look similar to what MSVC generates,
+  // which are something like "?A0x01234567@".
+  SourceManager &SM = Context.getSourceManager();
+  if (const FileEntry *FE = SM.getFileEntryForID(SM.getMainFileID())) {
+    // Truncate the hash so we get 8 characters of hexadecimal.
+    uint32_t TruncatedHash = uint32_t(xxHash64(FE->getName()));
+    AnonymousNamespaceHash = llvm::utohexstr(TruncatedHash);
+  } else {
+    // If we don't have a path to the main file, we'll just use 0.
+    AnonymousNamespaceHash = "0";
+  }
+}
+
 bool MicrosoftMangleContextImpl::shouldMangleCXXName(const NamedDecl *D) {
   if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
     LanguageLinkage L = FD->getLanguageLinkage();
@@ -785,7 +820,7 @@ void MicrosoftCXXNameMangler::mangleUnqualifiedName(const NamedDecl *ND,
 
       if (const NamespaceDecl *NS = dyn_cast<NamespaceDecl>(ND)) {
         if (NS->isAnonymousNamespace()) {
-          Out << "?A@";
+          Out << "?A0x" << Context.getAnonymousNamespaceHash() << '@';
           break;
         }
       }