[trafficserver] 32/33: TS-4425: Hide Ptr internals.

[jp...@apache.org]

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commit 523feded25bc46486f70e11203fe3b6c3a391103
Author: James Peach <jp...@apache.org>
AuthorDate: Sat May 7 14:13:22 2016 -0700

    TS-4425: Hide Ptr internals.
    
    Make the raw pointer member in Ptr<T> private and remove the implicit
    raw pointer conversion. This improves type safety and forces callers
    to declare when they circumvent the refcounting.
---
 lib/ts/Ptr.h       | 12 +++++++++++-
 lib/ts/test_Ptr.cc | 13 +++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/lib/ts/Ptr.h b/lib/ts/Ptr.h
index 3391608..8645fbf 100644
--- a/lib/ts/Ptr.h
+++ b/lib/ts/Ptr.h
@@ -100,6 +100,13 @@ private:
 ////////////////////////////////////////////////////////////////////////
 template <class T> class Ptr
 {
+  // https://en.wikibooks.org/wiki/More_C%2B%2B_Idioms/Safe_bool.
+  typedef void (Ptr::*bool_type)() const;
+  void
+  this_type_does_not_support_comparisons() const
+  {
+  }
+
 public:
   explicit Ptr(T *p = 0);
   Ptr(const Ptr<T> &);
@@ -109,9 +116,9 @@ public:
   Ptr<T> &operator=(const Ptr<T> &);
   Ptr<T> &operator=(T *);
 
-  operator T *() const { return (m_ptr); }
   T *operator->() const { return (m_ptr); }
   T &operator*() const { return (*m_ptr); }
+  operator bool_type() const { return m_ptr ? &Ptr::this_type_does_not_support_comparisons : 0; }
   int
   operator==(const T *p)
   {
@@ -170,7 +177,10 @@ public:
     m_ptr = ptr;
   }
 
+private:
   T *m_ptr;
+
+  friend class CoreUtils;
 };
 
 template <typename T>
diff --git a/lib/ts/test_Ptr.cc b/lib/ts/test_Ptr.cc
index 3f7f826..9029416 100644
--- a/lib/ts/test_Ptr.cc
+++ b/lib/ts/test_Ptr.cc
@@ -85,6 +85,19 @@ REGRESSION_TEST(Ptr_refcount)(RegressionTest *t, int /* atype ATS_UNUSED */, int
   box.check(alive == 0, "refcounts dropped");
 }
 
+REGRESSION_TEST(Ptr_bool)(RegressionTest *t, int /* atype ATS_UNUSED */, int *pstatus)
+{
+  TestBox box(t, pstatus);
+  box = REGRESSION_TEST_PASSED;
+  unsigned alive = 0;
+
+  Ptr<PtrObject> none;
+  Ptr<PtrObject> some = make_ptr(new PtrObject(&alive));
+
+  box.check(!none, "Empty Ptr<T> is false");
+  box.check(some, "Non-empty Ptr<T> is true");
+}
+
 int
 main(int /* argc ATS_UNUSED */, char ** /* argv ATS_UNUSED */)
 {

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