Re: [PATCH] libstdc++: Remove overzealous static_asserts from std::span

[Jonathan Wakely via Gcc-patches]

On 21/09/20 15:07 -0400, Patrick Palka via Libstdc++ wrote:

On Mon, 21 Sep 2020, Patrick Palka wrote:

For a span with empty static extent, we currently model the
preconditions of front(), back(), and operator[] as if they were
mandates, by using a static_assert to verify that extent != 0.  This
causes us to incorrectly reject valid programs that instantiate these
member functions but never call them.

libstdc++-v3/ChangeLog:

        * include/std/span (span::front): Remove static_assert.
        (span::back): Likewise.
        (span::operator[]): Likewise.
        * testsuite/23_containers/span/back_neg.cc: Remove.
        * testsuite/23_containers/span/front_neg.cc: Remove.
        * testsuite/23_containers/span/index_op_neg.cc: Remove.

Here's a version that rewrites rather than removes the testcases:

OK fortrunk, thanks.

We might want to backport this too.