In D84049#2182370, @jfb wrote:

We can ping @jwakely for libstdc++ 😃

I don't think this impacts anything I do with lit (which isn't very much anyway).

In D78154#1981905, @ldionne wrote:

@jwakely , how does libstdc++ ship experimental features? Does it ship them in its shared library?

P.S. you could use _GLIBCXX_ASSERTIONS instead for affected versions of libstdc++. That is a subset of _GLIBCXX_DEBUG that has far fewer checks, but is still much better than not checking anything at all.

I think this affects the versions of std::min(std::initializer_list) and std::max(std::initializer_list), and std::{min,max,minmax}_element. It's already fixed for GCC 10.

Note that MS-STL already has this behavior, while libstdc++ does not.

FWIW I think this particular bug was https://gcc.gnu.org/PR65942

In D66259#1631586, @thakis wrote:

It looks like this breaks building with gcc5.1:

In D51262#1213514, @mclow.lists wrote:

I should also mention that as a conforming extension, I have implemented the non-numeric bit operations for std::byte

I added a patch to https://bugs.llvm.org/show_bug.cgi?id=41578 that fixes it differently.

In D55840#1395019, @ldionne wrote:

TBH, I don't think that's a question the committee even thought about when introducing feature-test macros?

See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89345#c3 for what I've done in libstdc++

As it looks like libc++ isn't going to define the type for earlier dialects, libstdc++ doesn't either (which seems right anyway because the names aren't reserved prior to C++20).

In D56997#1367316, @andrewluo wrote:

You are right, it is not guaranteed per the standard, although it has worked before (at least on MSVC).

I'd be happy to restrict this to > C++17 only (which is automatically the case when using G++ because there's no -fdestroying-delete to enable it, you only get it with -std=c++2a, -std=gnu++2a etc.)

The simplest solution would be to change libstdc++'s <new> to:

@chandlerc thanks for catching this.

The __throw_xxx functions are not part of the public libstdc++ API and whatever Firefox is trying to do with them is not supported by libstdc++ and is undefined behaviour. Make it stop.