Subzero: Manage each Cfg as a std::unique_ptr<Cfg>.

src/IceCfg.h

 //===- subzero/src/IceCfg.h - Control flow graph ----------------*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file declares the Cfg class, which represents the control flow
@@ skipping 12 matching lines @@
 
 namespace Ice {
 
 class Cfg {
   Cfg(const Cfg &) = delete;
   Cfg &operator=(const Cfg &) = delete;
 
 public:
   ~Cfg();
 
-  // TODO(stichnot): Change this to return unique_ptr<Cfg>, and plumb
-  // it through the callers, to make ownership and lifetime and
-  // destruction requirements more explicit.
-  static Cfg *create(GlobalContext *Ctx) {
+  static std::unique_ptr<Cfg> create(GlobalContext *Ctx) {
     Cfg *Func = new Cfg(Ctx);

[JF, 2015/02/02 20:59:19]

It's slightly better to make this a unique_ptr too. In this case it doesn't
change much, but idiomatic C++ likes exception-safe code and what if
TLS_SET_FIELD throws oh my.

[Jim Stichnoth, 2015/02/03 00:48:51]

Done.

     ICE_TLS_SET_FIELD(CurrentCfg, Func);
-    return Func;
+    return std::unique_ptr<Cfg>(Func);
   }
   // Gets a pointer to the current thread's Cfg.
   static const Cfg *getCurrentCfg() { return ICE_TLS_GET_FIELD(CurrentCfg); }
-  void updateTLS() const { ICE_TLS_SET_FIELD(CurrentCfg, this); }
+  static void updateTLS(const Cfg *Func) {
+    ICE_TLS_SET_FIELD(CurrentCfg, Func);
+  }
   // Gets a pointer to the current thread's Cfg's allocator.
   static ArenaAllocator<> *getCurrentCfgAllocator() {
     assert(ICE_TLS_GET_FIELD(CurrentCfg));
     return ICE_TLS_GET_FIELD(CurrentCfg)->Allocator.get();
   }
 
   GlobalContext *getContext() const { return Ctx; }
 
   // Returns true if any of the specified options in the verbose mask
   // are set.  If the argument is omitted, it checks if any verbose
@@ skipping 165 matching lines @@
   // other uses are possible.
   ICE_TLS_DECLARE_FIELD(const Cfg *, CurrentCfg);
 
 public:
   static void TlsInit() { ICE_TLS_INIT_FIELD(CurrentCfg); }
 };
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICECFG_H