Linker failure in std::make_shared: ~__shared_ptr_emplace / ~_Sp_counted_ptr_inplace

[ecatmur]

#include <memory>
#include <type_traits>
struct G { auto operator()(auto f) { return f(0); } };
int main() {
    auto f = [](auto) -> void { std::make_shared<int>(); };
    static_assert(std::is_invocable_v<G, decltype(f)>);
    f(0);
}

fails linking with undefined reference to (libc++):

(.rodata._ZTVNSt3__120__shared_ptr_emplaceIiNS_9allocatorIiEEEE[_ZTVNSt3__120__shared_ptr_emplaceIiNS_9allocatorIiEEEE]+0x10): undefined reference to `std::__1::__shared_ptr_emplace<int, std::__1::allocator<int> >::~__shared_ptr_emplace()'
(.rodata._ZTVNSt3__120__shared_ptr_emplaceIiNS_9allocatorIiEEEE[_ZTVNSt3__120__shared_ptr_emplaceIiNS_9allocatorIiEEEE]+0x18): undefined reference to `std::__1::__shared_ptr_emplace<int, std::__1::allocator<int> >::~__shared_ptr_emplace()'
(.rodata._ZTVNSt3__120__shared_ptr_emplaceIiNS_9allocatorIiEEEE[_ZTVNSt3__120__shared_ptr_emplaceIiNS_9allocatorIiEEEE]+0x20): undefined reference to `std::__1::__shared_ptr_emplace<int, std::__1::allocator<int> >::__on_zero_shared()'
(.rodata._ZTVNSt3__120__shared_ptr_emplaceIiNS_9allocatorIiEEEE[_ZTVNSt3__120__shared_ptr_emplaceIiNS_9allocatorIiEEEE]+0x30): undefined reference to `std::__1::__shared_ptr_emplace<int, std::__1::allocator<int> >::__on_zero_shared_weak()'

or (libstdc++):

(.rodata._ZTVSt23_Sp_counted_ptr_inplaceIiSaIiELN9__gnu_cxx12_Lock_policyE2EE[_ZTVSt23_Sp_counted_ptr_inplaceIiSaIiELN9__gnu_cxx12_Lock_policyE2EE]+0x10): undefined reference to `std::_Sp_counted_ptr_inplace<int, std::allocator<int>, (__gnu_cxx::_Lock_policy)2>::~_Sp_counted_ptr_inplace()'
(.rodata._ZTVSt23_Sp_counted_ptr_inplaceIiSaIiELN9__gnu_cxx12_Lock_policyE2EE[_ZTVSt23_Sp_counted_ptr_inplaceIiSaIiELN9__gnu_cxx12_Lock_policyE2EE]+0x18): undefined reference to `std::_Sp_counted_ptr_inplace<int, std::allocator<int>, (__gnu_cxx::_Lock_policy)2>::~_Sp_counted_ptr_inplace()'
(.rodata._ZTVSt23_Sp_counted_ptr_inplaceIiSaIiELN9__gnu_cxx12_Lock_policyE2EE[_ZTVSt23_Sp_counted_ptr_inplaceIiSaIiELN9__gnu_cxx12_Lock_policyE2EE]+0x20): undefined reference to `std::_Sp_counted_ptr_inplace<int, std::allocator<int>, (__gnu_cxx::_Lock_policy)2>::_M_dispose()'
(.rodata._ZTVSt23_Sp_counted_ptr_inplaceIiSaIiELN9__gnu_cxx12_Lock_policyE2EE[_ZTVSt23_Sp_counted_ptr_inplaceIiSaIiELN9__gnu_cxx12_Lock_policyE2EE]+0x28): undefined reference to `std::_Sp_counted_ptr_inplace<int, std::allocator<int>, (__gnu_cxx::_Lock_policy)2>::_M_destroy()'
(.rodata._ZTVSt23_Sp_counted_ptr_inplaceIiSaIiELN9__gnu_cxx12_Lock_policyE2EE[_ZTVSt23_Sp_counted_ptr_inplaceIiSaIiELN9__gnu_cxx12_Lock_policyE2EE]+0x30): undefined reference to `std::_Sp_counted_ptr_inplace<int, std::allocator<int>, (__gnu_cxx::_Lock_policy)2>::_M_get_deleter(std::type_info const&)'

I guess all the unevaluated-context stuff inside __invokable_r (or libstdc++ equivalent) is persuading Sema that the class template instantiation vtable member emission stuff has already been done.

[ecatmur]

could be related to #44214

[llvmbot]

@llvm/issue-subscribers-clang-frontend

[pblxptr]

Any workaround for this to work with clang 14?

[shafik]

Confirmed behavior: https://godbolt.org/z/j4MKrrTv7

I am not sure what is going on here though. CC @erichkeane @Fznamznon

It looks like this behavior has existed for a while

[erichkeane]

Confirmed behavior: https://godbolt.org/z/j4MKrrTv7

I am not sure what is going on here though. CC @erichkeane @Fznamznon

It looks like this behavior has existed for a while

I don't really have a good idea, but a min-repro (without #include) would be pretty helpful as well.

[Endilll]

Reduced by me and C-Reduce: https://godbolt.org/z/bnedsfdEr

template <class _Tp>
class allocator {};

struct __shared_weak_count {
  virtual void __on_zero_shared_weak() noexcept = 0;
  virtual ~__shared_weak_count();
  virtual void __on_zero_shared() noexcept = 0;
};

template <class _Tp>
struct __shared_ptr_emplace : __shared_weak_count {
  template <class... _Args>
  explicit __shared_ptr_emplace(_Args &&...__args)
      : __storage_(allocator<int>{}) {}

  void __on_zero_shared() noexcept override;
  void __on_zero_shared_weak() noexcept override;
  struct _Storage {
    explicit _Storage(allocator<int> &&__a);
  };
  _Storage __storage_;
};

template <class, class... _Args>
void make_shared() {
  new __shared_ptr_emplace<int>(_Args()...);
}

int main() {
  auto f = [](auto) -> void { make_shared<int>; };
  f(0);
}

Output:

/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/14.0.1/../../../../x86_64-linux-gnu/bin/ld: /tmp/example-4de311.o: in function `__shared_ptr_emplace<int>::__shared_ptr_emplace<>()':
<source>:14: undefined reference to `__shared_ptr_emplace<int>::_Storage::_Storage(allocator<int>&&)'
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/14.0.1/../../../../x86_64-linux-gnu/bin/ld: <source>:14: undefined reference to `__shared_weak_count::~__shared_weak_count()'
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/14.0.1/../../../../x86_64-linux-gnu/bin/ld: /tmp/example-4de311.o: in function `__shared_weak_count::__shared_weak_count()':
<source>:4: undefined reference to `vtable for __shared_weak_count'
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/14.0.1/../../../../x86_64-linux-gnu/bin/ld: /tmp/example-4de311.o: in function `__shared_ptr_emplace<int>::~__shared_ptr_emplace()':
<source>:11: undefined reference to `__shared_weak_count::~__shared_weak_count()'
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/14.0.1/../../../../x86_64-linux-gnu/bin/ld: /tmp/example-4de311.o:(.data.rel.ro._ZTV20__shared_ptr_emplaceIiE[_ZTV20__shared_ptr_emplaceIiE]+0x10): undefined reference to `__shared_ptr_emplace<int>::__on_zero_shared_weak()'
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/14.0.1/../../../../x86_64-linux-gnu/bin/ld: /tmp/example-4de311.o:(.data.rel.ro._ZTV20__shared_ptr_emplaceIiE[_ZTV20__shared_ptr_emplaceIiE]+0x28): undefined reference to `__shared_ptr_emplace<int>::__on_zero_shared()'
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/14.0.1/../../../../x86_64-linux-gnu/bin/ld: /tmp/example-4de311.o:(.data.rel.ro._ZTI20__shared_ptr_emplaceIiE[_ZTI20__shared_ptr_emplaceIiE]+0x10): undefined reference to `typeinfo for __shared_weak_count'
clang++: error: linker command failed with exit code 1 (use -v to see invocation)

[shafik]

Note in the reduced example: https://godbolt.org/z/d3n111fqh

if we change make_shared<int>; to make_shared<int>(); implementations agree.

So this looks like a difference between used and called.

[shafik]

Reduced to single undefined symbol: https://godbolt.org/z/7981T5nK7

template <class _Tp>
class allocator {};

struct __shared_weak_count {
  virtual ~__shared_weak_count();
};

template <class _Tp>
struct __shared_ptr_emplace : __shared_weak_count 
{
  template <class... _Args>
  explicit __shared_ptr_emplace(_Args &&...__args)
      ;};

template <class, class... _Args>
void make_shared() {
  new __shared_ptr_emplace<int>(_Args()...);
}

int main() {
  auto f = [](auto) -> void { 
    make_shared<int>; 
  };
  f(0);
}