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Passing IncompleteType(&)[] to ranges::begin produces an error outside the immediate context, which is fine for ranges::begin, but it means that we fail to enforce the SFINAE-able constraints for ranges::size and ranges::size. They should not be callable for any array of unknown bound, whether the type is complete or not. Because we don't enforce that in their constraints, we get a hard error when they try to use ranges::begin. This simply adds explicit checks for arrays of unknown bound to the constraints for ranges::size and ranges::empty. We only need to check it for the __sentinel_size and __eq_iter_empty concepts, because those are the ones that are relevant to arrays, and which try to use ranges::begin. libstdc++-v3/ChangeLog: * include/bits/ranges_base.h (ranges::size, ranges::empty): Add explicit check for unbounded arrays before using ranges::begin. * testsuite/std/ranges/access/empty.cc: Check handling of unbounded arrays. * testsuite/std/ranges/access/size.cc: Likewise.
file: libstdc++-v3/README New users may wish to point their web browsers to the file index.html in the 'doc/html' subdirectory. It contains brief building instructions and notes on how to configure the library in interesting ways.