On Tue, 19 May 2026 at 15:04, Patrick Palka <[email protected]> wrote:
>
> Tested on x86_64-pc-linux-gnu, does this look OK for trunk/16/15?
OK for all three, thanks.
>
> -- >8 --
>
> PR libstdc++/125374
>
> libstdc++-v3/ChangeLog:
>
> * include/std/flat_map (_Flat_map_impl::_M_try_emplace): Forward
> instead of moving __k when inserting it.
> * testsuite/23_containers/flat_map/1.cc (test10): New test.
> ---
> libstdc++-v3/include/std/flat_map | 2 +-
> .../testsuite/23_containers/flat_map/1.cc | 18 ++++++++++++++++++
> 2 files changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/libstdc++-v3/include/std/flat_map
> b/libstdc++-v3/include/std/flat_map
> index e270735a87ba..18f06e6bdaf8 100644
> --- a/libstdc++-v3/include/std/flat_map
> +++ b/libstdc++-v3/include/std/flat_map
> @@ -534,7 +534,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> return {iterator{this, __key_it}, false};
>
> auto __guard = _M_make_clear_guard();
> - __key_it = _M_cont.keys.insert(__key_it, std::move(__k));
> + __key_it = _M_cont.keys.insert(__key_it, std::forward<_Key2>(__k));
> __value_it = _M_cont.values.begin() + (__key_it -
> _M_cont.keys.begin());
> _M_cont.values.emplace(__value_it, std::forward<_Args>(__args)...);
> __guard._M_disable();
> diff --git a/libstdc++-v3/testsuite/23_containers/flat_map/1.cc
> b/libstdc++-v3/testsuite/23_containers/flat_map/1.cc
> index 04c2101aab13..096b9eeac3e4 100644
> --- a/libstdc++-v3/testsuite/23_containers/flat_map/1.cc
> +++ b/libstdc++-v3/testsuite/23_containers/flat_map/1.cc
> @@ -13,6 +13,7 @@
> #include <testsuite_allocator.h>
> #include <testsuite_hooks.h>
> #include <testsuite_iterators.h>
> +#include <string>
> #include <tuple>
>
> struct Gt {
> @@ -283,6 +284,21 @@ test09()
> using value_type = std::pair<int, int>;
> }
>
> +constexpr
> +void
> +test10()
> +{
> + // PR libstdc++/125374 - flat_map unconditionally moves from lvalue keys in
> + // _M_try_emplace
> + std::flat_map<std::string, int, std::less<>> m;
> + std::string k = "hello";
> + m[k] = 1;
> + VERIFY (k == "hello");
> + k = "world";
> + m.try_emplace(k, 2);
> + VERIFY (k == "world");
> +}
> +
> void
> test()
> {
> @@ -298,6 +314,7 @@ test()
> test07();
> test08();
> test09();
> + test10();
> }
>
> constexpr
> @@ -313,6 +330,7 @@ test_constexpr()
> test07();
> test08();
> test09();
> + test10();
> return true;
> }
>
> --
> 2.54.0.rc1.54.g60f07c4f5c
>
