I think this issue below is https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70413. On Tue, Jul 23, 2019 at 6:21 PM Jeffrey Walton <noloader@xxxxxxxxx> wrote: > > We caught a bug report from the openSUSE folks. They are building with > LTO and -flto=6, and the new build flags generate ODR violations in > our library. > > For example, this class: > > template <class BASE, class SCHEME_OPTIONS, class KEY_CLASS> > class TF_ObjectImpl : public TF_ObjectImplBase<BASE, SCHEME_OPTIONS, KEY_CLASS> > { > public: > typedef KEY_CLASS KeyClass; > virtual ~TF_ObjectImpl() {} > const KeyClass & GetKey() const {return m_trapdoorFunction;} > KeyClass & AccessKey() {return m_trapdoorFunction;} > private: > KeyClass m_trapdoorFunction; > }; > > Produces ODR findings when using LTO like: > > pubkey.h:640:26: warning: type ‘struct TF_ObjectImpl’ violates the C++ > One Definition Rule [-Wodr] > class TF_ObjectImpl : public TF_ObjectImplBase<BASE, SCHEME_OPTIONS, KEY_CLASS> > ... > pubkey.h:640:26: note: a different type is defined in another translation unit > class TF_ObjectImpl : public TF_ObjectImplBase<BASE, SCHEME_OPTIONS, KEY_CLASS> > ... > pubkey.h:651:11: note: the first difference of corresponding > definitions is field ‘m_trapdoorFunction’ > KeyClass m_trapdoorFunction; > > When I remove the typedef and use KEY_CLASS directly: > > template <class BASE, class SCHEME_OPTIONS, class KEY_CLASS> > class TF_ObjectImpl : public TF_ObjectImplBase<BASE, SCHEME_OPTIONS, KEY_CLASS> > { > public: > // typedef KEY_CLASS KeyClass; > virtual ~TF_ObjectImpl() {} > const KeyClass & GetKey() const {return m_trapdoorFunction;} > KeyClass & AccessKey() {return m_trapdoorFunction;} > private: > KEY_CLASS m_trapdoorFunction; > }; > > Then the finding goes away. > > As far as I know, this is boilerplate templated C++ code. There is no > cpu specific or platform specific code involved. > > My first question is, should a class-scope typedef like used above effect ODR? > > The problem above on occurs on ARM. i686, x86_64 and Aarch64 are OK > and do not generate findings. Someone on Stack Overflow claimed the > ARM compiler was correct, and the other platforms missed the finding. > > My second question is, should I expect different behaviors for the > compiler on different platforms? > > My final question is, which platform is correct? Is ARM correct and > the others incorrect; or is ARM incorrect and the others correct? > > Thanks in advance.
