If one has a variable template with the type deduced from the initializer by means of auto keyword, for example:
template <typename T>
auto * p = (T*)nullptr;
How to make an instantiation of the variable for a particular type (e.g. to export it from a shared library)?
GCC and Clang way is to replace auto with the specific type:
template int * p<int>;
But it is rejected by MSVC with the error:
error C3410: 'p<int>': the type of the explicit instantiation 'int *' does not match the type of the variable template 'auto *'
Demo: https://gcc.godbolt.org/z/66xModTjK
MSVC demands to make the instantiation as:
template auto * p<int>;
which is in turn rejected by GCC and Clang with some weird messages:
error: 'auto' variable template instantiation is not allowed
error: declaration of 'auto* p<int>' has no initializer
Demo: https://gcc.godbolt.org/z/7j3nh7Whx
Which compilers are right here according to the standard?