[llvm] r290717 - [ADT] Delete RefCountedBaseVPTR.

[Justin Lebar via llvm-commits]

Author: jlebar
Date: Thu Dec 29 13:59:26 2016
New Revision: 290717

URL: http://llvm.org/viewvc/llvm-project?rev=290717&view=rev
Log:
[ADT] Delete RefCountedBaseVPTR.

Summary:
This class is unnecessary.

Its comment indicated that it was a compile error to allocate an
instance of a class that inherits from RefCountedBaseVPTR on the stack.
This may have been true at one point, but it's not today.

Moreover you really do not want to allocate *any* refcounted object on
the stack, vptrs or not, so if we did have a way to prevent these
objects from being stack-allocated, we'd want to apply it to regular
RefCountedBase too, obviating the need for a separate RefCountedBaseVPTR
class.

It seems that the main way RefCountedBaseVPTR provides safety is by
making its subclass's destructor virtual.  This may have been helpful at
one point, but these days clang will emit an error if you define a class
with virtual functions that inherits from RefCountedBase but doesn't
have a virtual destructor.

Reviewers: compnerd, dblaikie

Subscribers: cfe-commits, klimek, llvm-commits, mgorny

Differential Revision: https://reviews.llvm.org/D28162

Removed:
    llvm/trunk/lib/Support/IntrusiveRefCntPtr.cpp
Modified:
    llvm/trunk/include/llvm/ADT/IntrusiveRefCntPtr.h
    llvm/trunk/lib/Support/CMakeLists.txt
    llvm/trunk/unittests/ADT/IntrusiveRefCntPtrTest.cpp

Modified: llvm/trunk/include/llvm/ADT/IntrusiveRefCntPtr.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/IntrusiveRefCntPtr.h?rev=290717&r1=290716&r2=290717&view=diff
==============================================================================
--- llvm/trunk/include/llvm/ADT/IntrusiveRefCntPtr.h (original)
+++ llvm/trunk/include/llvm/ADT/IntrusiveRefCntPtr.h Thu Dec 29 13:59:26 2016
@@ -9,9 +9,9 @@
 //
 // This file defines IntrusiveRefCntPtr, a template class that
 // implements a "smart" pointer for objects that maintain their own
-// internal reference count, and RefCountedBase/RefCountedBaseVPTR, two
-// generic base classes for objects that wish to have their lifetimes
-// managed using reference counting.
+// internal reference count, and RefCountedBase, a generic base class
+// for objects that wish to have their lifetimes managed using reference
+// counting.
 //
 // IntrusiveRefCntPtr is similar to Boost's intrusive_ptr with added
 // LLVM-style casting.
@@ -52,36 +52,6 @@ namespace llvm {
     }
   };
 
-//===----------------------------------------------------------------------===//
-/// RefCountedBaseVPTR - A class that has the same function as
-///  RefCountedBase, but with a virtual destructor. Should be used
-///  instead of RefCountedBase for classes that already have virtual
-///  methods to enforce dynamic allocation via 'new'. Classes that
-///  inherit from RefCountedBaseVPTR can't be allocated on stack -
-///  attempting to do this will produce a compile error.
-//===----------------------------------------------------------------------===//
-  class RefCountedBaseVPTR {
-    mutable unsigned ref_cnt = 0;
-
-    virtual void anchor();
-
-  protected:
-    RefCountedBaseVPTR() = default;
-    RefCountedBaseVPTR(const RefCountedBaseVPTR &) : ref_cnt(0) {}
-
-    virtual ~RefCountedBaseVPTR() = default;
-
-    void Retain() const { ++ref_cnt; }
-    void Release() const {
-      assert (ref_cnt > 0 && "Reference count is already zero.");
-      if (--ref_cnt == 0) delete this;
-    }
-
-    template <typename T>
-    friend struct IntrusiveRefCntPtrInfo;
-  };
-
-
   template <typename T> struct IntrusiveRefCntPtrInfo {
     static void retain(T *obj) { obj->Retain(); }
     static void release(T *obj) { obj->Release(); }
@@ -124,10 +94,9 @@ public:
 ///  wrapping NULL pointers.
 ///
 /// Reference counting is implemented via calls to
-///  Obj->Retain()/Obj->Release(). Release() is required to destroy
-///  the object when the reference count reaches zero. Inheriting from
-///  RefCountedBase/RefCountedBaseVPTR takes care of this
-///  automatically.
+///  Obj->Retain()/Obj->Release(). Release() is required to destroy the
+///  object when the reference count reaches zero. Inheriting from
+///  RefCountedBase takes care of this automatically.
 //===----------------------------------------------------------------------===//
   template <typename T>
   class IntrusiveRefCntPtr {

Modified: llvm/trunk/lib/Support/CMakeLists.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/CMakeLists.txt?rev=290717&r1=290716&r2=290717&view=diff
==============================================================================
--- llvm/trunk/lib/Support/CMakeLists.txt (original)
+++ llvm/trunk/lib/Support/CMakeLists.txt Thu Dec 29 13:59:26 2016
@@ -61,7 +61,6 @@ add_llvm_library(LLVMSupport
   Hashing.cpp
   IntEqClasses.cpp
   IntervalMap.cpp
-  IntrusiveRefCntPtr.cpp
   JamCRC.cpp
   LEB128.cpp
   LineIterator.cpp

Removed: llvm/trunk/lib/Support/IntrusiveRefCntPtr.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/IntrusiveRefCntPtr.cpp?rev=290716&view=auto
==============================================================================
--- llvm/trunk/lib/Support/IntrusiveRefCntPtr.cpp (original)
+++ llvm/trunk/lib/Support/IntrusiveRefCntPtr.cpp (removed)
@@ -1,14 +0,0 @@
-//== IntrusiveRefCntPtr.cpp - Smart Refcounting Pointer ----------*- C++ -*-==//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/ADT/IntrusiveRefCntPtr.h"
-
-using namespace llvm;
-
-void RefCountedBaseVPTR::anchor() { }

Modified: llvm/trunk/unittests/ADT/IntrusiveRefCntPtrTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/ADT/IntrusiveRefCntPtrTest.cpp?rev=290717&r1=290716&r2=290717&view=diff
==============================================================================
--- llvm/trunk/unittests/ADT/IntrusiveRefCntPtrTest.cpp (original)
+++ llvm/trunk/unittests/ADT/IntrusiveRefCntPtrTest.cpp Thu Dec 29 13:59:26 2016
@@ -10,30 +10,29 @@
 #include "llvm/ADT/IntrusiveRefCntPtr.h"
 #include "gtest/gtest.h"
 
-namespace {
-struct VirtualRefCounted : public llvm::RefCountedBaseVPTR {
-  virtual void f() {}
-};
-}
-
 namespace llvm {
 
-// Run this test with valgrind to detect memory leaks.
-TEST(IntrusiveRefCntPtr, RefCountedBaseVPTRCopyDoesNotLeak) {
-  VirtualRefCounted *V1 = new VirtualRefCounted;
-  IntrusiveRefCntPtr<VirtualRefCounted> R1 = V1;
-  VirtualRefCounted *V2 = new VirtualRefCounted(*V1);
-  IntrusiveRefCntPtr<VirtualRefCounted> R2 = V2;
-}
+namespace {
+struct SimpleRefCounted : public RefCountedBase<SimpleRefCounted> {
+  SimpleRefCounted() { ++NumInstances; }
+  SimpleRefCounted(const SimpleRefCounted &) { ++NumInstances; }
+  ~SimpleRefCounted() { --NumInstances; }
 
-struct SimpleRefCounted : public RefCountedBase<SimpleRefCounted> {};
+  static int NumInstances;
+};
+int SimpleRefCounted::NumInstances = 0;
+} // anonymous namespace
 
-// Run this test with valgrind to detect memory leaks.
 TEST(IntrusiveRefCntPtr, RefCountedBaseCopyDoesNotLeak) {
-  SimpleRefCounted *S1 = new SimpleRefCounted;
-  IntrusiveRefCntPtr<SimpleRefCounted> R1 = S1;
-  SimpleRefCounted *S2 = new SimpleRefCounted(*S1);
-  IntrusiveRefCntPtr<SimpleRefCounted> R2 = S2;
+  EXPECT_EQ(0, SimpleRefCounted::NumInstances);
+  {
+    SimpleRefCounted *S1 = new SimpleRefCounted;
+    IntrusiveRefCntPtr<SimpleRefCounted> R1 = S1;
+    SimpleRefCounted *S2 = new SimpleRefCounted(*S1);
+    IntrusiveRefCntPtr<SimpleRefCounted> R2 = S2;
+    EXPECT_EQ(2, SimpleRefCounted::NumInstances);
+  }
+  EXPECT_EQ(0, SimpleRefCounted::NumInstances);
 }
 
 struct InterceptRefCounted : public RefCountedBase<InterceptRefCounted> {