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final classes can't be empty-base-optimized

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For that we need [[no_unique_address]].

Actually wait, I think maybe we have [[no_unique_address]]! Maybe we can
get rid of compressed_pair entirely...
This commit is contained in:
Steven Dee (Jōshin) 2024-06-15 18:53:56 -07:00
parent 5b242f6900
commit 393f024a4d
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2 changed files with 25 additions and 2 deletions
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5
ctl/compressed_pair.h
View file

@ -3,6 +3,7 @@
#ifndef COSMOPOLITAN_CTL_COMPRESSED_PAIR_H_ #ifndef COSMOPOLITAN_CTL_COMPRESSED_PAIR_H_
#define COSMOPOLITAN_CTL_COMPRESSED_PAIR_H_ #define COSMOPOLITAN_CTL_COMPRESSED_PAIR_H_
#include <__type_traits/is_empty.h> #include <__type_traits/is_empty.h>
#include <__type_traits/is_final.h>
#include <__utility/forward.h> #include <__utility/forward.h>
#include <__utility/move.h> #include <__utility/move.h>
#include <__utility/swap.h> #include <__utility/swap.h>
@ -12,7 +13,7 @@ namespace ctl {
namespace __ { namespace __ {
template<typename T> template<typename T>
concept Empty = std::is_empty_v<T>; concept EmptyBase = std::is_empty_v<T> && !std::is_final_v<T>;
template<typename T, int I> template<typename T, int I>
struct pair_elem struct pair_elem
@ -37,7 +38,7 @@ struct pair_elem
T t; T t;
}; };
template<Empty T, int I> template<EmptyBase T, int I>
struct pair_elem<T, I> : private T struct pair_elem<T, I> : private T
{ {
using value_type = T; using value_type = T;

22
test/ctl/unique_ptr_test.cc
View file

@ -54,6 +54,21 @@ struct SetsGDeleter
} }
}; };
struct FinalDeleter final
{
void operator()(auto*) const noexcept
{
}
};
struct StatefulDeleter
{
char state;
void operator()(auto*) const noexcept
{
}
};
static_assert(sizeof(Ptr<int, SetsGDeleter>) == sizeof(int*)); static_assert(sizeof(Ptr<int, SetsGDeleter>) == sizeof(int*));
struct SetsGCtor struct SetsGCtor
@ -185,6 +200,13 @@ main()
} }
#endif #endif
{
int a;
// Should compile.
Ptr<int, FinalDeleter> x(&a);
Ptr<int, StatefulDeleter> y(&a);
}
// next is 18 // next is 18
return 0; return 0;