[Bug c++/105320] New: Use of shared_ptr within a type exported from a module results in spurious compiler error

[Bug c++/105320] New: Use of shared_ptr within a type exported from a module results in spurious compiler error

[john at johnmaddock dot co.uk]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105320

            Bug ID: 105320
           Summary: Use of shared_ptr within a type exported from a module
                    results in spurious compiler error
           Product: gcc
           Version: 11.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: john at johnmaddock dot co.uk
  Target Milestone: ---

Reduced test case:

module.cpp:
module;

#include <memory>

export module test_support;

export template <class T> struct pimpl
{
private:
   std::shared_ptr<T> data;
public:
   pimpl(const T& x) : data(new T(x)) {}
   pimpl() = default;
};


test_module.cpp:
import test_support;

int main()
{
   pimpl<int> p1, p2(3);
}

Compile with:
g++ -std=gnu++20 -fmodules-ts module.cpp test_module.cpp

Results in:
D:/compilers/msys64/mingw64/include/c++/11.2.0/bits/shared_ptr_base.h:1369:
confused by earlier errors, bailing out

Note that there were no earlier errors ! ;)

[Bug c++/105320] Use of shared_ptr within a type exported from a module results in spurious compiler error

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105320

Patrick Palka <ppalka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2024-03-06
     Ever confirmed|0                           |1
           Keywords|                            |rejects-valid
                 CC|                            |ppalka at gcc dot gnu.org
             Status|UNCONFIRMED                 |NEW

--- Comment #1 from Patrick Palka <ppalka at gcc dot gnu.org> ---
GCC doesn't ICE, but it rejects with:

error: conflicting declaration of template ‘template<class _Tp1,
__gnu_cxx::_Lock_policy@test_support _Lp1> class std::__shared_ptr’
note: previous declaration ‘template<class _Tp,
__gnu_cxx::_Lock_policy@test_support _Lp> class std::__shared_ptr@test_support’
error: conflicting declaration of template ‘template<class _Tp1,
__gnu_cxx::_Lock_policy@test_support _Lp1> class std::__weak_ptr’
note: previous declaration ‘template<class _Tp,
__gnu_cxx::_Lock_policy@test_support _Lp> class std::__weak_ptr@test_support’

Reduced:

$ cat 105320_a.C
module;
template<class> struct _Sp_atomic;
template<class> struct shared_ptr {
  template<class> friend struct _Sp_atomic;
  using atomic_type = _Sp_atomic<int>;
};
export module test_support;
export
template<class T> struct A {
   shared_ptr<T> data;
};

$ cat 105320_b.C
import test_support;
A<int> a;

$ g++ -fmodules-ts 105320_{a,b}.C
105320_a.C:2:1: warning: global module fragment contents must be from
preprocessor inclusion [-Wglobal-module]
    2 | template<class> struct _Sp_atomic;
      | ^~~~~~~~
In module test_support, imported at 105320_b.C:1:
105320_a.C: In instantiation of ‘struct shared_ptr@test_support<int>’:
105320_a.C:11:18:   required from ‘struct A@test_support<int>’
   11 |    shared_ptr<T> data;
      |                  ^~~~
105320_b.C:3:8:   required from here
    3 | A<int> a;
      |        ^
105320_a.C:4:33: error: conflicting declaration of template ‘template<class>
struct _Sp_atomic’
    4 |   template<class> friend struct _Sp_atomic;
      |                                 ^~~~~~~~~~
105320_a.C:2:24: note: previous declaration ‘template<class> struct
_Sp_atomic@test_support’
    2 | template<class> struct _Sp_atomic;
      |                        ^~~~~~~~~~

[Bug c++/105320] Use of shared_ptr within a type exported from a module results in spurious compiler error

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105320

--- Comment #2 from Patrick Palka <ppalka at gcc dot gnu.org> ---
(In reply to Patrick Palka from comment #1)
> GCC doesn't ICE, but it rejects with:

GCC _trunk_ doesn't ICE rather..

[Bug c++/105320] Use of shared_ptr within a type exported from a module results in spurious compiler error

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105320

Patrick Palka <ppalka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tim152 at tgf dot pw

--- Comment #3 from Patrick Palka <ppalka at gcc dot gnu.org> ---
*** Bug 103844 has been marked as a duplicate of this bug. ***

[Bug c++/105320] Use of shared_ptr within a type exported from a module results in spurious compiler error

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105320

--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Nathaniel Shead <nshead@gcc.gnu.org>:

https://gcc.gnu.org/g:b5f6a56940e70838a07e885de03a92e2bd64674a

commit r15-59-gb5f6a56940e70838a07e885de03a92e2bd64674a
Author: Nathaniel Shead <nathanieloshead@gmail.com>
Date:   Mon Apr 29 17:00:13 2024 +1000

    c++: Fix instantiation of imported temploid friends [PR114275]

    This patch fixes a number of issues with the handling of temploid friend
    declarations.

    The primary issue is that instantiations of friend declarations should
    attach the declaration to the same module as the befriending class, by
    [module.unit] p7.1 and [temp.friend] p2; this could be a different
    module from the current TU, and so needs special handling.

    The other main issue here is that we can't assume that just because name
    lookup didn't find a definition for a hidden class template, that it
    doesn't exist at all: it could be a non-exported entity that we've
    nevertheless streamed in from an imported module.  We need to ensure
    that when instantiating template friend classes that we return the same
    TEMPLATE_DECL that we got from our imports, otherwise we will get later
    issues with 'duplicate_decls' (rightfully) complaining that they're
    different when trying to merge.

    This doesn't appear necessary for function templates due to the existing
    name lookup handling already finding these hidden declarations.

            PR c++/105320
            PR c++/114275

    gcc/cp/ChangeLog:

            * cp-tree.h (propagate_defining_module): Declare.
            (lookup_imported_hidden_friend): Declare.
            * decl.cc (duplicate_decls): Also check if hidden decls can be
            redeclared in this module.
            * module.cc (imported_temploid_friends): New.
            (init_modules): Initialize it.
            (trees_out::decl_value): Write it; don't consider imported
            temploid friends as attached to a module.
            (trees_in::decl_value): Read it.
            (get_originating_module_decl): Follow the owning decl for an
            imported temploid friend.
            (propagate_defining_module): New.
            * name-lookup.cc (get_mergeable_namespace_binding): New.
            (lookup_imported_hidden_friend): New.
            * pt.cc (tsubst_friend_function): Propagate defining module for
            new friend functions.
            (tsubst_friend_class): Lookup imported hidden friends.  Check
            for valid module attachment of existing names.  Propagate
            defining module for new classes.

    gcc/testsuite/ChangeLog:

            * g++.dg/modules/tpl-friend-10_a.C: New test.
            * g++.dg/modules/tpl-friend-10_b.C: New test.
            * g++.dg/modules/tpl-friend-10_c.C: New test.
            * g++.dg/modules/tpl-friend-10_d.C: New test.
            * g++.dg/modules/tpl-friend-11_a.C: New test.
            * g++.dg/modules/tpl-friend-11_b.C: New test.
            * g++.dg/modules/tpl-friend-12_a.C: New test.
            * g++.dg/modules/tpl-friend-12_b.C: New test.
            * g++.dg/modules/tpl-friend-12_c.C: New test.
            * g++.dg/modules/tpl-friend-12_d.C: New test.
            * g++.dg/modules/tpl-friend-12_e.C: New test.
            * g++.dg/modules/tpl-friend-12_f.C: New test.
            * g++.dg/modules/tpl-friend-13_a.C: New test.
            * g++.dg/modules/tpl-friend-13_b.C: New test.
            * g++.dg/modules/tpl-friend-13_c.C: New test.
            * g++.dg/modules/tpl-friend-13_d.C: New test.
            * g++.dg/modules/tpl-friend-13_e.C: New test.
            * g++.dg/modules/tpl-friend-13_f.C: New test.
            * g++.dg/modules/tpl-friend-13_g.C: New test.
            * g++.dg/modules/tpl-friend-14_a.C: New test.
            * g++.dg/modules/tpl-friend-14_b.C: New test.
            * g++.dg/modules/tpl-friend-14_c.C: New test.
            * g++.dg/modules/tpl-friend-14_d.C: New test.
            * g++.dg/modules/tpl-friend-9.C: New test.

    Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
    Reviewed-by: Jason Merrill <jason@redhat.com>

[Bug c++/105320] Use of shared_ptr within a type exported from a module results in spurious compiler error

[nshead at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105320

Nathaniel Shead <nshead at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |14.2
                 CC|                            |nshead at gcc dot gnu.org
           Assignee|unassigned at gcc dot gnu.org      |nshead at gcc dot gnu.org

--- Comment #5 from Nathaniel Shead <nshead at gcc dot gnu.org> ---
Fixed for GCC 15 for now.

Will backport later to GCC 14.2 with adjustments requested by Jason here:
https://gcc.gnu.org/pipermail/gcc-patches/2024-April/650204.html