[llvm-bugs] [Bug 38823] New: 'Undefined reference's with explicit instantiation of template class with virtual members

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=38823

            Bug ID: 38823
           Summary: 'Undefined reference's with explicit instantiation of
                    template class with virtual members
           Product: OpenMP
           Version: unspecified
          Hardware: All
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Clang Compiler Support
          Assignee: unassignedclangbugs at nondot.org
          Reporter: hahnjo at hahnjo.de
                CC: llvm-bugs at lists.llvm.org

Created attachment 20836
  --> https://bugs.llvm.org/attachment.cgi?id=20836&action=edit
source code detailing the problem

Consider something like the following:
$ cat virtual.cpp
template <typename T>
struct Base {
  virtual ~Base() {}
  virtual void test() const {}
  void offload() {
    #pragma omp target
    {}
  }
};

#ifndef IMPLICIT
template class Base<int>;
#endif

int main(int argc, char *argv[]) {
#ifdef IMPLICIT
  Base<int> b;
#endif

  return 0;
}

$ clang++ -fopenmp -fopenmp-targets=nvptx64-nvidia-cuda virtual.cpp
[...]
Undefined reference to '_ZdlPv'
Undefined reference to '_ZTVN10__cxxabiv117__class_type_infoE'
[...]
$ c++filt _ZdlPv
operator delete(void*)
$ c++filt _ZTVN10__cxxabiv117__class_type_infoE
vtable for __cxxabiv1::__class_type_info


Additional notes:
1) When instantiating the template implicitly (-DIMPLICIT), the error goes
away.
2) The vtable for __class_type_info goes away when compiling with -fno-rtti.
3) Commenting out the virtual destructor removes the reference to "operator
delete". I think the destructor is emitted because it is listed in the classes
vtable?

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