[LLVMbugs] [Bug 15783] New: Improve diagnostic when a destructor is implicitly deleted due to private operator delete

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=15783

            Bug ID: 15783
           Summary: Improve diagnostic when a destructor is implicitly
                    deleted due to private operator delete
           Product: clang
           Version: unspecified
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++11
          Assignee: unassignedclangbugs at nondot.org
          Reporter: nicolasweber at gmx.de
                CC: dgregor at apple.com, llvmbugs at cs.uiuc.edu
    Classification: Unclassified

template <typename Type> class IsInstrumented {
  class yes { char m; };
  class no { yes m[2]; };
  struct BaseMixin {
    void reportMemoryUsage() const {}
  };
  struct Base : public Type, public BaseMixin {
  };
  template <typename T, T t> class Helper {
  };
  template <typename U>
  static no
  deduce(U *, Helper<void(BaseMixin::*)() const, &U::reportMemoryUsage> * = 0);
  static yes deduce(...);
public:
  static const bool result = sizeof(yes) == sizeof(deduce((Base *)(0)));
};

template <typename T> bool hasReportMemoryUsage(const T *object) {
  return IsInstrumented<T>::result;
}

class Timer {
  void operator delete(void *p) {}
public:
  virtual ~Timer();
};
bool f() {
  Timer m_cacheTimer;
  return hasReportMemoryUsage(&m_cacheTimer);
}


The error message from r178563 looks like this:

$ third_party/llvm-build/Release+Asserts/bin/clang -c repro.ii -std=gnu++11
repro.ii:7:10: error: deleted function '~Base' cannot override a non-deleted
function
  struct Base : public Type, public BaseMixin {
         ^
repro.ii:13:51: note: in instantiation of member class
'IsInstrumented<Timer>::Base' requested here
  deduce(U *, Helper<void(BaseMixin::*)() const, &U::reportMemoryUsage> * = 0);
                                                  ^
repro.ii:13:3: note: while substituting deduced template arguments into
function template 'deduce' [with U = IsInstrumented<Timer>::Base]
  deduce(U *, Helper<void(BaseMixin::*)() const, &U::reportMemoryUsage> * = 0);
  ^
repro.ii:20:10: note: in instantiation of template class
'IsInstrumented<Timer>' requested here
  return IsInstrumented<T>::result;
         ^
repro.ii:30:10: note: in instantiation of function template specialization
'hasReportMemoryUsage<Timer>' requested here
  return hasReportMemoryUsage(&m_cacheTimer);
         ^
repro.ii:26:11: note: overridden virtual function is here
  virtual ~Timer();
          ^
1 error generated.


Says Richard: """Yes, the diagnostic seems to be correct, if unhelpful. Feel
free to file a bug on the diagnostic (if not, I'll try to remember to fix this
but can't promise!). We should be pointing out that the function is implicitly
deleted because it would otherwise try to call an inaccessible class-specific
'operator delete'."""

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