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From: Jonathan Wakely <redi@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r12-7003] libstdc++: Fix link failure in _OutputIteratorConcept Date: Wed, 2 Feb 2022 17:37:14 +0000 (GMT) [thread overview] Message-ID: <20220202173714.67F323858C2C@sourceware.org> (raw) https://gcc.gnu.org/g:b229c5186093fa6603030ae83d5fe640ef7051a4 commit r12-7003-gb229c5186093fa6603030ae83d5fe640ef7051a4 Author: Jonathan Wakely <jwakely@redhat.com> Date: Tue Jan 25 21:29:31 2022 +0000 libstdc++: Fix link failure in _OutputIteratorConcept The C++98-style concept check for output iterators causes a link failure on mingw-w64, because the __val() member function isn't defined. Change it to use a function pointer instead. That pointer is never set to anything meaningful, but it doesn't matter as the __constraints() function only has to be instantiated, it's never called. We could refactor all of these to use unevaluated contexts (e.g. sizeof of __decltype) so that we only check the expressions are well-formed, without any codegen at all. Any improvements to these are very low priority though. libstdc++-v3/ChangeLog: * include/bits/boost_concept_check.h (_OutputIteratorConcept): Change member function to data member of function pointer type. Diff: --- libstdc++-v3/include/bits/boost_concept_check.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/libstdc++-v3/include/bits/boost_concept_check.h b/libstdc++-v3/include/bits/boost_concept_check.h index 23dba067693..3d884eb440f 100644 --- a/libstdc++-v3/include/bits/boost_concept_check.h +++ b/libstdc++-v3/include/bits/boost_concept_check.h @@ -483,7 +483,9 @@ struct _Aux_require_same<_Tp,_Tp> { typedef _Tp _Type; }; *__i++ = __val(); // require postincrement and assignment } _Tp __i; - _ValueT __val() const; + // Use a function pointer here so no definition of the function needed. + // Just need something that returns a _ValueT (which might be a reference). + _ValueT (*__val)(); }; template<typename _Tp>
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