Possible bug in gcc-10.2 with non-type template parameter

Edward Diener eldlistmailingz@tropicsoft.com
Mon Jan 4 20:48:18 GMT 2021

The code, called test_predicate.cpp, simplified from a much more 
elaborate implementation:

template < typename T, T *d >  class atmp { atmp() {} };

template < typename T > struct ast
     static T avar;
     static atmp<T,&avar> acst;

template < typename T > T ast<T>::avar;
template < typename T > atmp<T,&ast<T>::avar> ast<T>::acst;

int main()
    return 0;

The command line compile flags for gcc-10.2:

-fvisibility-inlines-hidden -Wno-unused-local-typedefs 
-ftrack-macro-expansion=0 -Wno-unused-variable 
-D_GLIBCXX_USE_CXX11_ABI=1 -Wa,-mbig-obj -m64 -mthreads -O0 -fno-inline 
-Wall -g -fvisibility=hidden -std=c++11 -c

The result:

test_predicate.cpp:10:47: error: conflicting declaration 'atmp<T, (& 
ast<T>::avar)> ast<T>::acst'
    10 | template < typename T > atmp<T,&ast<T>::avar> ast<T>::acst;
       |                                               ^~~~~~
test_predicate.cpp:6:26: note: previous declaration as 'atmp<T, (& 
ast<T>::avar)> ast<T>::acst'
     6 |     static atmp<T,&avar> acst;
       |                          ^~~~

The same source compiled with clang-11.0 and VC++14.2 succeeds with no 

Is this s bug in gcc ? If so, is there a known workaround ?

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