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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/99985] [10/11 Regression] bits/hashtable.h:483:9: error: body of ‘constexpr’ function ... not a return-statement since g:1cbba49e3417d9b0661e70301d6fb7a7f52fd360
Date: Fri, 09 Apr 2021 10:29:32 +0000	[thread overview]
Message-ID: <bug-99985-4-8cSYmWQx3L@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-99985-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99985

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
We can still make it short circuit (and so not instantiate class templates
unnecessarily) like this:

#if __cplusplus <= 201402L
          return __and_<__bool_constant<_No_realloc>,
                 is_nothrow_copy_constructible<_Hash>,
                 is_nothrow_copy_constructible<_Equal>>::value;
#else
          if constexpr (_No_realloc)
            if constexpr (is_nothrow_copy_constructible<_Hash>())
              return is_nothrow_copy_constructible<_Equal>();
          return false;
#endif

I didn't use __and_<> because that has to be instantiated too (although it's
cheaper than the is_xxx_constructible ones), and for C++17 the if-constexpr
version avoids that. But if we need a #if to work for C++11 anyway, we might as
well use __and_ for C++11 and C++14, and if-constexpr for everything later.

  parent reply	other threads:[~2021-04-09 10:29 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-09  8:34 [Bug c++/99985] New: [11 " marxin at gcc dot gnu.org
2021-04-09  8:35 ` [Bug c++/99985] " marxin at gcc dot gnu.org
2021-04-09 10:06 ` jakub at gcc dot gnu.org
2021-04-09 10:21 ` [Bug c++/99985] [10/11 " redi at gcc dot gnu.org
2021-04-09 10:24 ` redi at gcc dot gnu.org
2021-04-09 10:27 ` jakub at gcc dot gnu.org
2021-04-09 10:29 ` redi at gcc dot gnu.org [this message]
2021-04-09 12:09 ` [Bug libstdc++/99985] [9/10/11 " cvs-commit at gcc dot gnu.org
2021-04-09 15:15 ` cvs-commit at gcc dot gnu.org
2021-04-09 16:42 ` cvs-commit at gcc dot gnu.org
2021-04-09 16:42 ` redi at gcc dot gnu.org

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