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offsetof: proper detection when sizeof() != alignof
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769a57526c
commit
9068e2071c
1 changed files with 9 additions and 8 deletions
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@ -22,14 +22,15 @@ namespace ams::util {
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namespace impl {
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template<size_t Alignment>
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template<size_t MaxDepth>
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struct OffsetOfUnionHolder {
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template<typename ParentType, typename MemberType, size_t Offset>
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union UnionImpl {
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using PaddingMember = std::array<char, alignof(ParentType)>;
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static constexpr size_t GetOffset() { return Offset; }
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struct {
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char padding[Offset];
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PaddingMember padding[Offset];
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MemberType members[(sizeof(ParentType) / sizeof(MemberType)) + 1];
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} data;
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UnionImpl<ParentType, MemberType, Offset + 1> next_union;
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@ -46,12 +47,12 @@ namespace ams::util {
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};
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template<typename ParentType, typename MemberType>
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union UnionImpl<ParentType, MemberType, Alignment> { /* Empty */ };
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union UnionImpl<ParentType, MemberType, MaxDepth> { /* Empty */ };
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};
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template<typename ParentType, typename MemberType>
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struct OffsetOfCalculator {
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using UnionHolder = typename OffsetOfUnionHolder<alignof(MemberType)>::template UnionImpl<ParentType, MemberType, 0>;
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using UnionHolder = typename OffsetOfUnionHolder<sizeof(MemberType) / alignof(MemberType) + 1>::template UnionImpl<ParentType, MemberType, 0>;
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union Union {
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char c;
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UnionHolder first_union;
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@ -80,15 +81,15 @@ namespace ams::util {
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const auto start = std::addressof(cur_union.data.members[0]);
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const auto next = GetNextAddress(start, target);
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if (next < target) {
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if constexpr (Offset + 1 < alignof(MemberType)) {
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if (next != target) {
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if constexpr (Offset < sizeof(MemberType) / alignof(MemberType)) {
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return OffsetOfImpl(member, cur_union.next_union);
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} else {
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static_assert(Offset + 1 <= alignof(MemberType));
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std::abort();
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}
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}
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return (next - start) * sizeof(MemberType) + Offset;
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return (next - start) * sizeof(MemberType) + Offset * alignof(MemberType);
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}
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