Create proper Objective-C @encoding for C++ classes; fixes rdar://9357400.

Go through and expand the members of bases into the encoding string (and encode the VTable as well).
Unlike gcc which expands virtual bases as many times as they appear in the
hierarchy, clang will only expand them once at the end, to reflect the actual layout.

Note that there doesn't seem to be a way to indicate in the encoding that
packing/alignment of members is different that normal, in which case
the encoding will be out-of-sync with the real layout.
If the runtime switches to just consider the size of types without
taking into account alignment, we could easily make padding explicit in the
encoding (e.g. using arrays of chars). The encoding strings would be
longer then though.

Also encode a flexible array member as array of 0 size, like gcc, not as a pointer.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@131365 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 152 insertions, 20 deletions

diff --git a/lib/AST/ASTContext.cpp b/lib/AST/ASTContext.cpp
index 379c13a934..2272bdae13 100644
--- a/lib/AST/ASTContext.cpp
+++ b/lib/AST/ASTContext.cpp
@@ -31,6 +31,7 @@
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/raw_ostream.h"
 #include "CXXABI.h"
+#include <map>
 
 using namespace clang;
 
@@ -4152,7 +4153,8 @@ void ASTContext::getObjCEncodingForTypeImpl(QualType T, std::string& S,
                                             bool ExpandStructures,
                                             const FieldDecl *FD,
                                             bool OutermostType,
-                                            bool EncodingProperty) const {
+                                            bool EncodingProperty,
+                                            bool StructField) const {
   if (T->getAs<BuiltinType>()) {
     if (FD && FD->isBitField())
       return EncodeBitField(this, S, T, FD);
@@ -4237,7 +4239,7 @@ void ASTContext::getObjCEncodingForTypeImpl(QualType T, std::string& S,
   if (const ArrayType *AT =
       // Ignore type qualifiers etc.
         dyn_cast<ArrayType>(T->getCanonicalTypeInternal())) {
-    if (isa<IncompleteArrayType>(AT)) {
+    if (isa<IncompleteArrayType>(AT) && !StructField) {
       // Incomplete arrays are encoded as a pointer to the array element.
       S += '^';
 
@@ -4250,7 +4252,8 @@ void ASTContext::getObjCEncodingForTypeImpl(QualType T, std::string& S,
         S += llvm::utostr(CAT->getSize().getZExtValue());
       else {
         //Variable length arrays are encoded as a regular array with 0 elements.
-        assert(isa<VariableArrayType>(AT) && "Unknown array type!");
+        assert((isa<VariableArrayType>(AT) || isa<IncompleteArrayType>(AT)) &&
+               "Unknown array type!");
         S += '0';
       }
 
@@ -4288,24 +4291,30 @@ void ASTContext::getObjCEncodingForTypeImpl(QualType T, std::string& S,
     }
     if (ExpandStructures) {
       S += '=';
-      for (RecordDecl::field_iterator Field = RDecl->field_begin(),
-                                   FieldEnd = RDecl->field_end();
-           Field != FieldEnd; ++Field) {
-        if (FD) {
-          S += '"';
-          S += Field->getNameAsString();
-          S += '"';
-        }
+      if (!RDecl->isUnion()) {
+        getObjCEncodingForStructureImpl(RDecl, S, FD);
+      } else {
+        for (RecordDecl::field_iterator Field = RDecl->field_begin(),
+                                     FieldEnd = RDecl->field_end();
+             Field != FieldEnd; ++Field) {
+          if (FD) {
+            S += '"';
+            S += Field->getNameAsString();
+            S += '"';
+          }
 
-        // Special case bit-fields.
-        if (Field->isBitField()) {
-          getObjCEncodingForTypeImpl(Field->getType(), S, false, true,
-                                     (*Field));
-        } else {
-          QualType qt = Field->getType();
-          getLegacyIntegralTypeEncoding(qt);
-          getObjCEncodingForTypeImpl(qt, S, false, true,
-                                     FD);
+          // Special case bit-fields.
+          if (Field->isBitField()) {
+            getObjCEncodingForTypeImpl(Field->getType(), S, false, true,
+                                       (*Field));
+          } else {
+            QualType qt = Field->getType();
+            getLegacyIntegralTypeEncoding(qt);
+            getObjCEncodingForTypeImpl(qt, S, false, true,
+                                       FD, /*OutermostType*/false,
+                                       /*EncodingProperty*/false,
+                                       /*StructField*/true);
+          }
         }
       }
     }
@@ -4426,6 +4435,129 @@ void ASTContext::getObjCEncodingForTypeImpl(QualType T, std::string& S,
   assert(0 && "@encode for type not implemented!");
 }
 
+void ASTContext::getObjCEncodingForStructureImpl(RecordDecl *RDecl,
+                                                 std::string &S,
+                                                 const FieldDecl *FD,
+                                                 bool includeVBases) const {
+  assert(RDecl && "Expected non-null RecordDecl");
+  assert(!RDecl->isUnion() && "Should not be called for unions");
+  if (!RDecl->getDefinition())
+    return;
+
+  CXXRecordDecl *CXXRec = dyn_cast<CXXRecordDecl>(RDecl);
+  std::map<uint64_t, NamedDecl *> FieldOrBaseOffsets;
+  const ASTRecordLayout &layout = getASTRecordLayout(RDecl);
+  
+  unsigned i = 0;
+  for (RecordDecl::field_iterator Field = RDecl->field_begin(),
+                               FieldEnd = RDecl->field_end();
+       Field != FieldEnd; ++Field, ++i) {
+    assert(!FieldOrBaseOffsets[layout.getFieldOffset(i)]);
+    FieldOrBaseOffsets[layout.getFieldOffset(i)] = *Field;
+  }
+  
+  if (CXXRec) {
+    for (CXXRecordDecl::base_class_iterator
+           BI = CXXRec->bases_begin(),
+           BE = CXXRec->bases_end(); BI != BE; ++BI) {
+      if (!BI->isVirtual()) {
+        CXXRecordDecl *base = BI->getType()->getAsCXXRecordDecl();
+        assert(!FieldOrBaseOffsets[layout.getBaseClassOffsetInBits(base)]);
+        FieldOrBaseOffsets[layout.getBaseClassOffsetInBits(base)] = base;
+      }
+    }
+    if (includeVBases) {
+      for (CXXRecordDecl::base_class_iterator
+             BI = CXXRec->vbases_begin(),
+             BE = CXXRec->vbases_end(); BI != BE; ++BI) {
+        CXXRecordDecl *base = BI->getType()->getAsCXXRecordDecl();
+        assert(!FieldOrBaseOffsets[layout.getVBaseClassOffsetInBits(base)]);
+        FieldOrBaseOffsets[layout.getVBaseClassOffsetInBits(base)] = base;
+      }
+    }
+  }
+
+  CharUnits size;
+  if (CXXRec) {
+    size = includeVBases ? layout.getSize() : layout.getNonVirtualSize();
+  } else {
+    size = layout.getSize();
+  }
+
+  uint64_t CurOffs = 0;
+  std::map<uint64_t, NamedDecl *>::iterator
+    CurLayObj = FieldOrBaseOffsets.begin();
+
+  if (CurLayObj != FieldOrBaseOffsets.end() && CurLayObj->first != 0) {
+    assert(CXXRec && CXXRec->isDynamicClass() &&
+           "Offset 0 was empty but no VTable ?");
+    if (FD) {
+      S += "\"_vptr$";
+      std::string recname = CXXRec->getNameAsString();
+      if (recname.empty()) recname = "?";
+      S += recname;
+      S += '"';
+    }
+    S += "^^?";
+    CurOffs += getTypeSize(VoidPtrTy);
+  }
+
+  if (!RDecl->hasFlexibleArrayMember()) {
+    // Mark the end of the structure.
+    assert(!FieldOrBaseOffsets[toBits(size)]);
+    FieldOrBaseOffsets[toBits(size)] = 0;
+  }
+
+  for (; CurLayObj != FieldOrBaseOffsets.end(); ++CurLayObj) {
+    assert(CurOffs <= CurLayObj->first);
+
+    if (CurOffs < CurLayObj->first) {
+      uint64_t padding = CurLayObj->first - CurOffs; 
+      // FIXME: There doesn't seem to be a way to indicate in the encoding that
+      // packing/alignment of members is different that normal, in which case
+      // the encoding will be out-of-sync with the real layout.
+      // If the runtime switches to just consider the size of types without
+      // taking into account alignment, we could make padding explicit in the
+      // encoding (e.g. using arrays of chars). The encoding strings would be
+      // longer then though.
+      CurOffs += padding;
+    }
+
+    NamedDecl *dcl = CurLayObj->second;
+    if (dcl == 0)
+      break; // reached end of structure.
+
+    if (CXXRecordDecl *base = dyn_cast<CXXRecordDecl>(dcl)) {
+      // We expand the bases without their virtual bases since those are going
+      // in the initial structure. Note that this differs from gcc which
+      // expands virtual bases each time one is encountered in the hierarchy,
+      // making the encoding type bigger than it really is.
+      getObjCEncodingForStructureImpl(base, S, FD, /*includeVBases*/false);
+      CurOffs += toBits(getASTRecordLayout(base).getNonVirtualSize());
+    } else {
+      FieldDecl *field = cast<FieldDecl>(dcl);
+      if (FD) {
+        S += '"';
+        S += field->getNameAsString();
+        S += '"';
+      }
+
+      if (field->isBitField()) {
+        EncodeBitField(this, S, field->getType(), field);
+        CurOffs += field->getBitWidth()->EvaluateAsInt(*this).getZExtValue();
+      } else {
+        QualType qt = field->getType();
+        getLegacyIntegralTypeEncoding(qt);
+        getObjCEncodingForTypeImpl(qt, S, false, true, FD,
+                                   /*OutermostType*/false,
+                                   /*EncodingProperty*/false,
+                                   /*StructField*/true);
+        CurOffs += getTypeSize(field->getType());
+      }
+    }
+  }
+}
+
 void ASTContext::getObjCEncodingForTypeQualifier(Decl::ObjCDeclQualifier QT,
                                                  std::string& S) const {
   if (QT & Decl::OBJC_TQ_In)