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From: "fw at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/110000] GCC should implement
 exclude_from_explicit_instantiation
Date: Sat, 27 May 2023 10:39:42 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110000

Florian Weimer <fw at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fw at gcc dot gnu.org

--- Comment #5 from Florian Weimer <fw at gcc dot gnu.org> ---
How hard is this to use in practice? With current Clang, this:

=E2=80=9C
template <class T>
class S {
  __attribute__ ((visibility ("hidden"), exclude_from_explicit_instantiatio=
n))
  int f1 ();
  int f2 ();
};

template <class T> int
S<T>::f1 ()
{
  return 1;
}

template <class T> int
S<T>::f2 ()
{
  return f1 ();
}

template class S<int>;
=E2=80=9D

still inlines S<int>::f1 into S<int>::f2. This may not threaten future
evolution of the implementation in this particular case, but it would certa=
inly
be helpful to have some guides similar to
<https://community.kde.org/Policies/Binary_Compatibility_Issues_With_C%2B%2=
B>.
Clang's attribute documentation describes what happens, but it doesn't comm=
ent
on the actual implications for ABI compatibility.=