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From: "dangelog at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/102399] New: Cannot mix GCC and C++11 / C23 attribute syntax
Date: Sat, 18 Sep 2021 11:24:48 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102399

            Bug ID: 102399
           Summary: Cannot mix GCC and C++11 / C23 attribute syntax
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dangelog at gmail dot com
  Target Milestone: ---

Hello,

If one tries to mix GCC's attribute syntax (__attribute__) and with C++11 /=
 C23
([[attribute]]), GCC rejects the code (no matter what the order of the
attributes is):


  #define EXPORT __attribute__((visibility("default")))

  struct [[nodiscard]] EXPORT Foo { Foo(); };


https://gcc.godbolt.org/z/W868xjeMq


While a workaround exists (by sticking to the same "kind" of attribute synt=
ax),
it's not always possible or easy to achieve in big codebases, where for
compatibility/legacy reasons the attributes are expanded via macros and can
expand to a random combination of GCC or C++ attributes.

For comparison, Clang and MSVC allow mixed syntaxes.=