On 1/6/2021 3:51 PM, Stefan Ring via Gcc-help wrote:
On Mon, Jan 4, 2021 at 9:49 PM Edward Diener
<eldlistmailingz@xxxxxxxxxxxxxx> wrote:
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
error.
Is this s bug in gcc ? If so, is there a known workaround ?
Hmm, I'm not a language lawyer, and the error message does not seem to
make sense, but what happens when you remove the offending line in
your real program?
A workaround which works with gcc-10.2 as pointed out to me is:
static atmp<T,&ast<T>::avar> acst;
instead of:
static atmp<T,&avar> acst;
However the workaround should not be needed and indeed is not needed by
clang or VC++. I have reported this bug to gcc at
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98523.
