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Update FOA implementation to exhibit strong guarantee for Hash, KeyEqual in copy assignment

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This commit is contained in:
Christian Mazakas
2022-12-01 14:32:07 -08:00
parent 4ac3dcc90c
commit 260b573d8d
1 changed files with 18 additions and 3 deletions
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21
include/boost/unordered/detail/foa.hpp
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@ -1266,13 +1266,28 @@ public:
table& operator=(const table& x)
{
BOOST_UNORDERED_STATIC_ASSERT_HASH_PRED(Hash, Pred)
static constexpr auto pocca=
alloc_traits::propagate_on_container_copy_assignment::value;
if(this!=std::addressof(x)){
clear();
h()=x.h();
pred()=x.pred();
// if copy construction here winds up throwing, the container is still
// left intact so we perform these operations first
hasher tmp_h=x.h();
key_equal tmp_p=x.pred();
// already noexcept, clear() before we swap the Hash, Pred just in case
// the clear() impl relies on them at some point in the future
clear();
// because we've asserted at compile-time that Hash and Pred are nothrow
// swappable, we can safely mutate our source container and maintain
// consistency between the Hash, Pred compatibility
using std::swap;
swap(h(),tmp_h);
swap(pred(),tmp_p);
if_constexpr<pocca>([&,this]{
if(al()!=x.al())reserve(0);
copy_assign_if<pocca>(al(),x.al());