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From: "lh_mouse at 126 dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/109464] gcc does not instantiate constructor for explicitly
 instantiated template
Date: Tue, 11 Apr 2023 06:16:12 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109464

--- Comment #5 from LIU Hao <lh_mouse at 126 dot com> ---
Additional information:

I tried splitting the two class templates into two separate .cpp files, so =
the
explicit instantiation of `basic_shallow_string<char>` should not be subjec=
t to
the instantiation of `basic_cow_string<char>`. This made GCC emit the
constructor correctly (checked by examining assembly), but still failed to =
the
very same undefined reference.

At the moment, a temporary workaround is to mark the constructor of
`basic_shallow_string` as `always_inline`. This works for GCC 10, 11 and 12.
Haven't checked GCC 9 as it's no longer available from APT sources of my
current machine.=