Re: [PATCH 1/4] libstdc++: Reduce the size of an unbounded iota_view

[Jonathan Wakely via Gcc-patches]

On 28/09/20 00:48 -0400, Patrick Palka via Libstdc++ wrote:

libstdc++-v3/ChangeLog:

        * include/std/ranges (iota_view::_M_bound): Give it
        [[no_unique_address]].
        * testsuite/std/ranges/iota/iota_view.cc: Check that an
        unbounded iota_view has minimal size.

OK.

libstdc++-v3/include/std/ranges                     | 2 +-
libstdc++-v3/testsuite/std/ranges/iota/iota_view.cc | 3 +++
2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index ed04fa0001d..964a2b616a6 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -511,7 +511,7 @@ namespace ranges
      };

      _Winc _M_value = _Winc();
-      _Bound _M_bound = _Bound();
+      [[no_unique_address]] _Bound _M_bound = _Bound();

    public:
      iota_view() = default;
diff --git a/libstdc++-v3/testsuite/std/ranges/iota/iota_view.cc 
b/libstdc++-v3/testsuite/std/ranges/iota/iota_view.cc
index 65d166fbd3b..8a33e10a093 100644
--- a/libstdc++-v3/testsuite/std/ranges/iota/iota_view.cc
+++ b/libstdc++-v3/testsuite/std/ranges/iota/iota_view.cc
@@ -77,6 +77,9 @@ test04()
  VERIFY( it == v.end() );
}

+// Verify we optimize away the 'bound' data member of an unbounded iota_view.
+static_assert(sizeof(std::ranges::iota_view<char>) == 1);
+
int
main()
{
--
2.28.0.618.g9bc233ae1c