https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90295
--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>: https://gcc.gnu.org/g:710508c7b1a2c8e1d75d4c4f1ac79473dbf2b2bb commit r11-4749-g710508c7b1a2c8e1d75d4c4f1ac79473dbf2b2bb Author: Jonathan Wakely <jwak...@redhat.com> Date: Thu Nov 5 16:19:15 2020 +0000 libstdc++: Fix multiple definitions of std::exception_ptr functions [PR 97729] This fixes some multiple definition errors caused by the changes for PR libstdc++/90295. The previous solution for inlining the members of std::exception_ptr but still exporting them from the library was to suppress the 'inline' keyword on those functions when compiling libsupc++/eh_ptr.cc, so they get defined in that file. That produces ODR violations though, because there are now both inline and non-inline definitions in the library, due to the use of std::exception_ptr in other files sucg as src/c++11/future.cc. The new solution is to define all the relevant members as 'inline' unconditionally, but use __attribute__((used)) to cause definitions to be emitted in libsupc++/eh_ptr.cc as before. This doesn't quite work however, because PR c++/67453 means the attribute is ignored on constructors and destructors. As a workaround, the old solution (conditionally inline) is still used for those members, but they are given the always_inline attribute so that they aren't emitted in src/c++11/future.o as inline definitions. libstdc++-v3/ChangeLog: PR libstdc++/97729 * include/std/future (__basic_future::_M_get_result): Use nullptr for null pointer constant. * libsupc++/eh_ptr.cc (operator==, operator!=): Remove definitions. * libsupc++/exception_ptr.h (_GLIBCXX_EH_PTR_USED): Define macro to conditionally add __attribute__((__used__)). (operator==, operator!=, exception_ptr::exception_ptr()) (exception_ptr::exception_ptr(const exception_ptr&)) (exception_ptr::~exception_ptr()) (exception_ptr::operator=(const exception_ptr&)) (exception_ptr::swap(exception_ptr&)): Always define as inline. Add macro to be conditionally "used".
