[AST] Use llvm::TrailingObjects in CXXTryStmt

1. Use llvm::TrailingObjects in CXXTryStmt instead of manually doing the reinterpret_casts + pointer arithmetic. This is more consistent with other classes using this idiom and this make it clearer that this class has trailing objects.
2. Make the class CXXTryStmt final since it has trailing objects.
3. Move the friend declarations together.

No functional changes.

Patch by Bruno Ricci!

Differential Revision: https://reviews.llvm.org/D48873

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@337688 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/AST/StmtCXX.h

@@ -62,21 +62,22 @@ public:
 
 /// CXXTryStmt - A C++ try block, including all handlers.
 ///
-class CXXTryStmt : public Stmt {
+class CXXTryStmt final : public Stmt,
+                         private llvm::TrailingObjects<CXXTryStmt, Stmt *> {
+
+  friend TrailingObjects;
+  friend class ASTStmtReader;
+
   SourceLocation TryLoc;
   unsigned NumHandlers;
+  size_t numTrailingObjects(OverloadToken<Stmt *>) const { return NumHandlers; }
 
   CXXTryStmt(SourceLocation tryLoc, Stmt *tryBlock, ArrayRef<Stmt*> handlers);
-
   CXXTryStmt(EmptyShell Empty, unsigned numHandlers)
     : Stmt(CXXTryStmtClass), NumHandlers(numHandlers) { }
 
-  Stmt const * const *getStmts() const {
-    return reinterpret_cast<Stmt const * const*>(this + 1);
-  }
-  Stmt **getStmts() {
-    return reinterpret_cast<Stmt **>(this + 1);
-  }
+  Stmt *const *getStmts() const { return getTrailingObjects<Stmt *>(); }
+  Stmt **getStmts() { return getTrailingObjects<Stmt *>(); }
 
 public:
   static CXXTryStmt *Create(const ASTContext &C, SourceLocation tryLoc,
@@ -115,8 +116,6 @@ public:
   child_range children() {
     return child_range(getStmts(), getStmts() + getNumHandlers() + 1);
   }
-
-  friend class ASTStmtReader;
 };
 
 /// CXXForRangeStmt - This represents C++0x [stmt.ranged]'s ranged for

lib/AST/StmtCXX.cpp

@@ -25,18 +25,14 @@ QualType CXXCatchStmt::getCaughtType() const {
 
 CXXTryStmt *CXXTryStmt::Create(const ASTContext &C, SourceLocation tryLoc,
                                Stmt *tryBlock, ArrayRef<Stmt *> handlers) {
-  std::size_t Size = sizeof(CXXTryStmt);
-  Size += ((handlers.size() + 1) * sizeof(Stmt *));
-
+  const size_t Size = totalSizeToAlloc<Stmt *>(handlers.size() + 1);
   void *Mem = C.Allocate(Size, alignof(CXXTryStmt));
   return new (Mem) CXXTryStmt(tryLoc, tryBlock, handlers);
 }
 
 CXXTryStmt *CXXTryStmt::Create(const ASTContext &C, EmptyShell Empty,
                                unsigned numHandlers) {
-  std::size_t Size = sizeof(CXXTryStmt);
-  Size += ((numHandlers + 1) * sizeof(Stmt *));
-
+  const size_t Size = totalSizeToAlloc<Stmt *>(numHandlers + 1);
   void *Mem = C.Allocate(Size, alignof(CXXTryStmt));
   return new (Mem) CXXTryStmt(Empty, numHandlers);
 }
@@ -44,7 +40,7 @@ CXXTryStmt *CXXTryStmt::Create(const ASTContext &C, EmptyShell Empty,
 CXXTryStmt::CXXTryStmt(SourceLocation tryLoc, Stmt *tryBlock,
                        ArrayRef<Stmt *> handlers)
     : Stmt(CXXTryStmtClass), TryLoc(tryLoc), NumHandlers(handlers.size()) {
-  Stmt **Stmts = reinterpret_cast<Stmt **>(this + 1);
+  Stmt **Stmts = getStmts();
   Stmts[0] = tryBlock;
   std::copy(handlers.begin(), handlers.end(), Stmts + 1);
 }