[MS ABI] Implement more of the Itanium mangling rules

[majnemer]

Summary

We didn't implement one of the corner cases: a lambda which belongs to
an initializer for a field. In this case, we need to mangle the field
name into the lambda.

This fixes PR31197.

[rnk]

test/CodeGenCXX/mangle-ms-cxx11.cpp

337

This machinery is also supposed to kick in for lambdas in default arguments, right? Can you add that test case?

[majnemer]

• Address review comments

[rnk]

lib/AST/MicrosoftMangle.cpp

838

Isn't this no good if I have two lambdas in one default arg?

inline int f(int x = [] { return 1; }() + [] { return 2; }()) { return x; }
int main() { return f(); }

We probably need <lambda_${argno}_${id}>. =/

[majnemer]

• Address review comments

[majnemer]

• Simplify the mangling a little bit

[rnk]

lgtm Thanks, apologies for the scope creep.

lib/AST/MicrosoftMangle.cpp

~msvc_hashing_ostream() override {
     llvm::MD5::stringifyResult(Hash, HexString);
 
     if (StartsWithEscape)
       OS << '\01';
     OS << "??@" << HexString << '@';
   }
 };
 
+static const DeclContext *
+getLambdaDefaultArgumentDeclContext(const Decl *D) {
+  if (const auto *RD = dyn_cast<CXXRecordDecl>(D))
+    if (RD->isLambda())
+      if (const auto *Parm =
+              dyn_cast_or_null<ParmVarDecl>(RD->getLambdaContextDecl()))
+        return Parm->getDeclContext();
+  return nullptr;
+}
+
 /// \brief Retrieve the declaration context that should be used when mangling
 /// the given declaration.
 static const DeclContext *getEffectiveDeclContext(const Decl *D) {
   // The ABI assumes that lambda closure types that occur within
   // default arguments live in the context of the function. However, due to
   // the way in which Clang parses and creates function declarations, this is
   // not the case: the lambda closure type ends up living in the context
   // where the function itself resides, because the function declaration itself
   // had not yet been created. Fix the context here.
-  if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D)) {
-    if (RD->isLambda())
-      if (ParmVarDecl *ContextParam =
-              dyn_cast_or_null<ParmVarDecl>(RD->getLambdaContextDecl()))
-        return ContextParam->getDeclContext();
-  }
+  if (const auto *LDADC = getLambdaDefaultArgumentDeclContext(D))
+    return LDADC;
 
   // Perform the same check for block literals.
   if (const BlockDecl *BD = dyn_cast<BlockDecl>(D)) {
     if (ParmVarDecl *ContextParam =
             dyn_cast_or_null<ParmVarDecl>(BD->getBlockManglingContextDecl()))
       return ContextParam->getDeclContext();
   }
 
static const FunctionDecl *getStructor(const NamedDecl *ND) {
 
   const auto *FD = cast<FunctionDecl>(ND);
   if (const auto *FTD = FD->getPrimaryTemplate())
     return FTD->getTemplatedDecl();
 
   return FD;
 }
 
-static bool isLambda(const NamedDecl *ND) {
-  const CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(ND);
-  if (!Record)
-    return false;
-
-  return Record->isLambda();
-}
-
 /// MicrosoftMangleContextImpl - Overrides the default MangleContext for the
 /// Microsoft Visual C++ ABI.
 class MicrosoftMangleContextImpl : public MicrosoftMangleContext {
   typedef std::pair<const DeclContext *, IdentifierInfo *> DiscriminatorKeyTy;
   llvm::DenseMap<DiscriminatorKeyTy, unsigned> Discriminator;
   llvm::DenseMap<const NamedDecl *, unsigned> Uniquifier;
   llvm::DenseMap<const CXXRecordDecl *, unsigned> LambdaIds;
   llvm::DenseMap<const NamedDecl *, unsigned> SEHFilterIds;
public:
   void mangleStringLiteral(const StringLiteral *SL, raw_ostream &Out) override;
   bool getNextDiscriminator(const NamedDecl *ND, unsigned &disc) {
     const DeclContext *DC = getEffectiveDeclContext(ND);
     if (!DC->isFunctionOrMethod())
       return false;
 
     // Lambda closure types are already numbered, give out a phony number so
     // that they demangle nicely.
-    if (isLambda(ND)) {
-      disc = 1;
+    // Use scope zero for lambdas in default arguments, one for all other lambdas.
+    if (const auto *RD = dyn_cast<CXXRecordDecl>(ND)) {
+      if (RD->isLambda()) {
+        disc = getLambdaDefaultArgumentDeclContext(RD) ? 0 : 1;
         return true;
       }
+    }
 
     // Use the canonical number for externally visible decls.
     if (ND->isExternallyVisible()) {
       disc = getASTContext().getManglingNumber(ND);
       return true;
     }
 
     // Anonymous tags are already numbered.
case DeclarationName::Identifier: {
                "Typedef was not named!");
         mangleSourceName(D->getDeclName().getAsIdentifierInfo()->getName());
         break;
       }
 
       if (const CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(TD)) {
         if (Record->isLambda()) {
           llvm::SmallString<10> Name("<lambda_");
+
+          Decl *LambdaContextDecl = Record->getLambdaContextDecl();
+          unsigned LambdaManglingNumber = Record->getLambdaManglingNumber();
           unsigned LambdaId;
-          if (Record->getLambdaManglingNumber())
-            LambdaId = Record->getLambdaManglingNumber();
+          const ParmVarDecl *Parm =
+              dyn_cast_or_null<ParmVarDecl>(LambdaContextDecl);
+          const FunctionDecl *Func =
+              Parm ? dyn_cast<FunctionDecl>(Parm->getDeclContext()) : nullptr;
+
+          if (Func)
+            LambdaId = Func->getNumParams() - Parm->getFunctionScopeIndex();
+          else if (LambdaManglingNumber)
+            LambdaId = LambdaManglingNumber;
           else
             LambdaId = Context.getLambdaId(Record);
 
           Name += llvm::utostr(LambdaId);
           Name += ">";
 
           mangleSourceName(Name);
+
+          // If the context of a closure type is an initializer for a class
+          // member (static or nonstatic), it is encoded in a qualified name.
+          if (LambdaManglingNumber && LambdaContextDecl) {
+            if ((isa<VarDecl>(LambdaContextDecl) ||
+                 isa<FieldDecl>(LambdaContextDecl)) &&
+                LambdaContextDecl->getDeclContext()->isRecord()) {
+              mangleUnqualifiedName(cast<NamedDecl>(LambdaContextDecl));
+            }
+          }
           break;
         }
       }
 
       llvm::SmallString<64> Name("<unnamed-type-");
       if (DeclaratorDecl *DD =
               Context.getASTContext().getDeclaratorForUnnamedTagDecl(TD)) {
         // Anonymous types without a name for linkage purposes have their
if (const BlockDecl *BD = dyn_cast<BlockDecl>(DC)) {
           Diags.getCustomDiagID(DiagnosticsEngine::Error,
                                 "cannot mangle a local inside this block yet");
       Diags.Report(BD->getLocation(), DiagID);
 
       // FIXME: This is completely, utterly, wrong; see ItaniumMangle
       // for how this should be done.
       Out << "__block_invoke" << Context.getBlockId(BD, false);
       Out << '@';
-      continue;
     } else if (const ObjCMethodDecl *Method = dyn_cast<ObjCMethodDecl>(DC)) {
       mangleObjCMethodName(Method);
     } else if (isa<NamedDecl>(DC)) {
       ND = cast<NamedDecl>(DC);
       if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(ND)) {
         mangle(FD, "?");
         break;
-      } else
+      } else {
         mangleUnqualifiedName(ND);
+        // Lambdas in default arguments conceptually belong to the function the
+        // parameter corresponds to.
+        if (const auto *LDADC = getLambdaDefaultArgumentDeclContext(ND)) {
+          DC = LDADC;
+          continue;
+        }
+      }
     }
     DC = DC->getParent();
   }
 }
 
 void MicrosoftCXXNameMangler::mangleCXXDtorType(CXXDtorType T) {
   // Microsoft uses the names on the case labels for these dtor variants.  Clang
   // uses the Itanium terminology internally.  Everything in this ABI delegates

test/CodeGenCXX/mangle-ms-cxx11.cpp

 // __unaligned qualifier for function types
 struct unaligned_foo8_S {
     void unaligned_foo8() volatile __unaligned;
 };
 void unaligned_foo8_S::unaligned_foo8() volatile __unaligned {}
 
 // CHECK-DAG: @"\01?unaligned_foo8@unaligned_foo8_S@@QFCEXXZ"
 
+namespace PR31197 {
+struct A {
+  // CHECK-DAG: define linkonce_odr x86_thiscallcc i32* @"\01??R<lambda_1>@x@A@PR31197@@QBE@XZ"(
+  int *x = []() {
+    static int white;
+    // CHECK-DAG: @"\01?white@?1???R<lambda_1>@x@A@PR31197@@QBE@XZ@4HA"
+    return &white;
+  }();
+  // CHECK-DAG: define linkonce_odr x86_thiscallcc i32* @"\01??R<lambda_1>@y@A@PR31197@@QBE@XZ"(
+  int *y = []() {
+    static int black;
+    // CHECK-DAG: @"\01?black@?1???R<lambda_1>@y@A@PR31197@@QBE@XZ@4HA"
+    return &black;
+  }();
+  using FPtrTy = void(void);
+  static void default_args(FPtrTy x = [] {}, FPtrTy y = [] {}) {}
+  // CHECK-DAG: @"\01??R<lambda_1>@?A@??default_args@A@PR31197@@SAXP6AXXZ0@Z@QBE@XZ"(
+  // CHECK-DAG: @"\01??R<lambda_2>@?A@??default_args@A@PR31197@@SAXP6AXXZ0@Z@QBE@XZ"(
+};
+A a;
+
+int call_it = (A::default_args(), 1);
+}