__builtin_dynamic_object_size

[Jonathan Wakely]

There's a patch to add __builtin_dynamic_object_size to clang:
https://reviews.llvm.org/D56760

It was suggested that this could be done via a new flag bit for
__builtin_object_size, but only if GCC would support that too
(otherwise it would be done as a separate builtin).

Is there any interest in adding that as an option to __builtin_object_size?

I know Jakub is concerned about arbitrarily complex expressions, when
__builtin_object_size is supposed to always be efficient and always
evaluate at compile time (which would imply the dynamic behaviour
should be a separate builtin, if it exists at all).