On Thu, 29 Apr 2021 at 17:46, Andrey Semashev via Std-Proposals <std-proposals@lists.isocpp.org> wrote:

On 4/29/21 7:32 PM, Edward Catmur wrote:
> It works in the most performance-sensitive case.

No, it doesn't. It only works in your toy example where you call
std::current_exception_stacktrace directly from the catch block and
nothing else. This breaks in practically any other case that is even
remotely close to anything real-world, where you do something useful in
the exception handler that involves a cross-TU call. No, that doesn't
sound like "works" to me, sorry.

I may have been unclear. The logic is that the compiler sets the flag on the handler to request stacktrace unless it can prove that the catch block does not call anything that might require it.