https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108290
Bug ID: 108290
Summary: QoI: bind_front captureless lambda is too big
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: lichray at gmail dot com
Target Milestone: ---
libstdc++ does not give the following guarantee, while libc++ and MS STL can:
auto captureless = [](FILE *, void *, size_t) { return 0; };
static_assert(sizeof(std::bind_front(captureless, stdin)) ==
sizeof(stdin));
See https://godbolt.org/z/TrWP6KohG
The expectation is that some form of EBO is implemented to treat the empty
callable as the base. libc++ did this by laying down all state entities in a
std::tuple. MS STL did this by storing compressed_pair<target,
std::tuple<bound_args>> (so they have this optimization even when their
std::tuple doesn't do EBO).
