On 17/08/20 19:13 +0200, François Dumont via Libstdc++ wrote:
Hi
   Here is the new proposal.
   As we can't remove template parameters I simply restore those that
I tried to pass differently _H2 and _ExtractKey, so eventually I only
remove usage of _Hash which I renamed in _Unused. Maybe I can keep the
doc about it in hashtable.h and just add a remark saying that it is
now unused.
   For _RangeHash, formerly _H2, and _ExtractKey I just stop
maintaining any storage. When we need those I always use a value
initialized instance. I kind of prefer the value initialization syntax
because you can't confuse it with a function call but let me know if
it is wrong and I should use _ExtractKey() or _RangeHash(). I also add
some static assertions about those types regarding their noexcept
qualifications.
   I also included in this patch the few changes left from [Hashtable
0/6] which are mostly _M_insert_unique_node and _M_insert_multi_node
signature cleanup as the key part can be extracted from the inserted
node.
   Tested under Linux x86_64, ok to commit ?
François
On 06/08/20 11:27 am, Jonathan Wakely wrote:
On 06/08/20 08:35 +0200, François Dumont wrote:
On 17/07/20 1:35 pm, Jonathan Wakely wrote:
I really like the general idea of getting rid of some of the
complexity and not supporting infinite customization. But we can do
that without changing mangled names of the _Hashtable specialiations.
I didn't thought we need to keep abi compatibility for extensions.
These aren't extensions though, they're part of std::unordered_map
etc.
Just because something like _Vector_base is an internal type rather
than something defined in the standard doesn't mean we can just change
its ABI, because that would change the ABI of std::vector. It the same
here.
Changing _Hashtable affects all users of std::unordered_map etc.
diff --git a/libstdc++-v3/include/bits/hashtable.h
b/libstdc++-v3/include/bits/hashtable.h
index 7b772a475e3..1ba32a3c7e2 100644
--- a/libstdc++-v3/include/bits/hashtable.h
+++ b/libstdc++-v3/include/bits/hashtable.h
@@ -311,35 +303,37 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
"Cache the hash code or qualify your functors involved"
" in hash code and bucket index computation with noexcept");
- // When hash codes are cached local iterator inherits from H2 functor
- // which must then be default constructible.
- static_assert(__if_hash_cached<is_default_constructible<_H2>>::value,
+ // To get bucket index we need _RangeHash not to throw.
+ static_assert(is_nothrow_default_constructible<_RangeHash>::value,
"Functor used to map hash code to bucket index"
- " must be default constructible");
+ " is nothrow default constructible");
Please phrase this as "must be nothrow default constructible".
+ static_assert(noexcept(
+ std::declval<const _RangeHash&>()((std::size_t)0, (std::size_t)0)),
+ "Functor used to map hash code to bucket index is noexcept");
Same here, "must be noexcept".
Otherwise this looks great, thanks. Please push.
