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[ntuple] Fixes for alignment #22312

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[ntuple] Fixes for alignment #22312

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17c0782
[io] move (R)AlignedStorage to bit utils
jblomer May 11, 2026
524aab6
[ntuple] use TClass alignment info where possible
jblomer May 11, 2026
ba94832
[ntuple] fix memory allocation for over-aligned fields
jblomer May 15, 2026
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13 changes: 13 additions & 0 deletions core/foundation/inc/ROOT/BitUtils.hxx
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Expand Up @@ -15,6 +15,7 @@
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <type_traits>

#ifdef _MSC_VER
Expand All @@ -41,6 +42,13 @@ inline constexpr T AlignUp(T value, T align) noexcept
return (value + align - 1) & ~(align - 1);
}

/// Storage type whose alignment matches \a Align bytes.
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@silverweed silverweed May 18, 2026

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Suggested change
/// Storage type whose alignment matches \a Align bytes.
/// Storage type whose alignment matches \a AlignT bytes.

/// Used to instantiate std::vector specializations with guaranteed buffer alignment.
template <std::size_t AlignT>
struct alignas(AlignT) RAlignedStorage {
char data[AlignT] = {};
};

/// Given an integer `x`, returns the number of leading 0-bits starting at the most significant bit position.
/// If `x` is 0, it returns the size of `x` in bits.
///
Expand Down Expand Up @@ -148,6 +156,11 @@ inline std::size_t TrailingZeroes(T x)
#endif // _MSC_VER
}

inline bool IsPowerOfTwo(std::uint64_t v)
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@pcanal pcanal May 18, 2026

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You may (or may not) want to use this in IsValidAlignment (which is only different as it reject 0)

{
return (v & (v - 1)) == 0;
}

} // namespace Internal
} // namespace ROOT

Expand Down
35 changes: 15 additions & 20 deletions io/io/inc/TEmulatedCollectionProxy.h
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Expand Up @@ -23,27 +23,22 @@ class TEmulatedCollectionProxy : public TGenCollectionProxy {
friend class TCollectionProxy;

public:
/// Storage type whose alignment matches \a Align bytes.
/// Used to instantiate std::vector specializations with guaranteed buffer alignment.
template <std::size_t Align>
struct alignas(Align) AlignedStorage {
char data[Align] = {};
};

// Convenience vector aliases for each supported alignment.
using Cont1_t = std::vector<AlignedStorage< 1>>;
using Cont2_t = std::vector<AlignedStorage< 2>>;
using Cont4_t = std::vector<AlignedStorage< 4>>;
using Cont8_t = std::vector<AlignedStorage< 8>>;
using Cont16_t = std::vector<AlignedStorage< 16>>;
using Cont32_t = std::vector<AlignedStorage< 32>>;
using Cont64_t = std::vector<AlignedStorage< 64>>;
using Cont128_t = std::vector<AlignedStorage< 128>>;
using Cont256_t = std::vector<AlignedStorage< 256>>;
using Cont512_t = std::vector<AlignedStorage< 512>>;
using Cont1024_t = std::vector<AlignedStorage<1024>>;
using Cont2048_t = std::vector<AlignedStorage<2048>>;
using Cont4096_t = std::vector<AlignedStorage<4096>>;
// clang-format off
using Cont1_t = std::vector<ROOT::Internal::RAlignedStorage< 1>>;
using Cont2_t = std::vector<ROOT::Internal::RAlignedStorage< 2>>;
using Cont4_t = std::vector<ROOT::Internal::RAlignedStorage< 4>>;
using Cont8_t = std::vector<ROOT::Internal::RAlignedStorage< 8>>;
using Cont16_t = std::vector<ROOT::Internal::RAlignedStorage< 16>>;
using Cont32_t = std::vector<ROOT::Internal::RAlignedStorage< 32>>;
using Cont64_t = std::vector<ROOT::Internal::RAlignedStorage< 64>>;
using Cont128_t = std::vector<ROOT::Internal::RAlignedStorage< 128>>;
using Cont256_t = std::vector<ROOT::Internal::RAlignedStorage< 256>>;
using Cont512_t = std::vector<ROOT::Internal::RAlignedStorage< 512>>;
using Cont1024_t = std::vector<ROOT::Internal::RAlignedStorage<1024>>;
using Cont2048_t = std::vector<ROOT::Internal::RAlignedStorage<2048>>;
using Cont4096_t = std::vector<ROOT::Internal::RAlignedStorage<4096>>;
// clang-format on

// Canonical container type (used for sizeof/typeid; actual alignment is
// selected at runtime via the alignment switch in each method).
Expand Down
9 changes: 4 additions & 5 deletions tree/ntuple/inc/ROOT/RField.hxx
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Expand Up @@ -158,14 +158,13 @@ private:
TClass *fClass;

public:
explicit RClassDeleter(TClass *cl) : fClass(cl) {}
explicit RClassDeleter(TClass *cl);
void operator()(void *objPtr, bool dtorOnly) final;
};

TClass *fClass;
/// Additional information kept for each entry in `fSubfields`
std::vector<RSubfieldInfo> fSubfieldsInfo;
std::size_t fMaxAlignment = 1;

/// The staging area stores inputs to I/O rules according to the offsets given by the streamer info of
/// "TypeName@@Version". The area is allocated depending on I/O rules resp. the source members of the I/O rules.
Expand Down Expand Up @@ -220,8 +219,8 @@ public:
~RClassField() override;

std::vector<RValue> SplitValue(const RValue &value) const final;
size_t GetValueSize() const final;
size_t GetAlignment() const final { return fMaxAlignment; }
std::size_t GetValueSize() const final;
std::size_t GetAlignment() const final;
std::uint32_t GetTypeVersion() const final;
std::uint32_t GetTypeChecksum() const final;
/// For polymorphic classes (that declare or inherit at least one virtual method), return the expected dynamic type
Expand All @@ -240,7 +239,7 @@ private:
TClass *fClass;

public:
explicit RStreamerFieldDeleter(TClass *cl) : fClass(cl) {}
explicit RStreamerFieldDeleter(TClass *cl);
void operator()(void *objPtr, bool dtorOnly) final;
};

Expand Down
12 changes: 4 additions & 8 deletions tree/ntuple/inc/ROOT/RField/RFieldProxiedCollection.hxx
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Expand Up @@ -128,13 +128,9 @@ protected:
RCollectionIterableOnce::RIteratorFuncs fIFuncsWrite;

public:
explicit RProxiedCollectionDeleter(std::shared_ptr<TVirtualCollectionProxy> proxy) : fProxy(proxy) {}
explicit RProxiedCollectionDeleter(std::shared_ptr<TVirtualCollectionProxy> proxy);
RProxiedCollectionDeleter(std::shared_ptr<TVirtualCollectionProxy> proxy, std::unique_ptr<RDeleter> itemDeleter,
size_t itemSize)
: fProxy(proxy), fItemDeleter(std::move(itemDeleter)), fItemSize(itemSize)
{
fIFuncsWrite = RCollectionIterableOnce::GetIteratorFuncs(fProxy.get(), false /* readFromDisk */);
}
size_t itemSize);
void operator()(void *objPtr, bool dtorOnly) final;
};

Expand Down Expand Up @@ -176,8 +172,8 @@ public:
~RProxiedCollectionField() override = default;

std::vector<RValue> SplitValue(const RValue &value) const final;
size_t GetValueSize() const final { return fProxy->Sizeof(); }
size_t GetAlignment() const final { return alignof(std::max_align_t); }
std::size_t GetValueSize() const final;
std::size_t GetAlignment() const final;
void AcceptVisitor(ROOT::Detail::RFieldVisitor &visitor) const final;
};

Expand Down
5 changes: 3 additions & 2 deletions tree/ntuple/inc/ROOT/RField/RFieldRecord.hxx
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Expand Up @@ -59,8 +59,9 @@ class RRecordField : public RFieldBase {
std::vector<std::size_t> fOffsets;

public:
RRecordDeleter(std::vector<std::unique_ptr<RDeleter>> itemDeleters, const std::vector<std::size_t> &offsets)
: fItemDeleters(std::move(itemDeleters)), fOffsets(offsets)
RRecordDeleter(std::vector<std::unique_ptr<RDeleter>> itemDeleters, const std::vector<std::size_t> &offsets,
std::size_t alignment)
: RDeleter(alignment), fItemDeleters(std::move(itemDeleters)), fOffsets(offsets)
{
}
void operator()(void *objPtr, bool dtorOnly) final;
Expand Down
34 changes: 21 additions & 13 deletions tree/ntuple/inc/ROOT/RField/RFieldSTLMisc.hxx
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Expand Up @@ -233,8 +233,10 @@ class ROptionalField : public RNullableField {
std::size_t fEngagementPtrOffset = 0;

public:
ROptionalDeleter(std::unique_ptr<RDeleter> itemDeleter, std::size_t engagementPtrOffset)
: fItemDeleter(std::move(itemDeleter)), fEngagementPtrOffset(engagementPtrOffset) {}
ROptionalDeleter(std::unique_ptr<RDeleter> itemDeleter, std::size_t engagementPtrOffset, std::size_t alignment)
: RDeleter(alignment), fItemDeleter(std::move(itemDeleter)), fEngagementPtrOffset(engagementPtrOffset)
{
}
void operator()(void *objPtr, bool dtorOnly) final;
};

Expand Down Expand Up @@ -264,8 +266,8 @@ public:
~ROptionalField() override = default;

std::vector<RValue> SplitValue(const RValue &value) const final;
size_t GetValueSize() const final;
size_t GetAlignment() const final;
std::size_t GetValueSize() const final;
std::size_t GetAlignment() const final;
};

template <typename ItemT>
Expand All @@ -284,7 +286,10 @@ class RUniquePtrField : public RNullableField {
std::unique_ptr<RDeleter> fItemDeleter;

public:
explicit RUniquePtrDeleter(std::unique_ptr<RDeleter> itemDeleter) : fItemDeleter(std::move(itemDeleter)) {}
explicit RUniquePtrDeleter(std::unique_ptr<RDeleter> itemDeleter)
: RDeleter(alignof(std::unique_ptr<char>)), fItemDeleter(std::move(itemDeleter))
{
}
void operator()(void *objPtr, bool dtorOnly) final;
};

Expand Down Expand Up @@ -313,8 +318,8 @@ public:
~RUniquePtrField() override = default;

std::vector<RValue> SplitValue(const RValue &value) const final;
size_t GetValueSize() const final { return sizeof(std::unique_ptr<char>); }
size_t GetAlignment() const final { return alignof(std::unique_ptr<char>); }
std::size_t GetValueSize() const final { return sizeof(std::unique_ptr<char>); }
std::size_t GetAlignment() const final { return alignof(std::unique_ptr<char>); }
};

template <typename ItemT>
Expand Down Expand Up @@ -363,8 +368,8 @@ public:
RField &operator=(RField &&other) = default;
~RField() final = default;

size_t GetValueSize() const final { return sizeof(std::string); }
size_t GetAlignment() const final { return std::alignment_of<std::string>(); }
std::size_t GetValueSize() const final { return sizeof(std::string); }
std::size_t GetAlignment() const final { return alignof(std::string); }
void AcceptVisitor(ROOT::Detail::RFieldVisitor &visitor) const final;
};

Expand All @@ -388,9 +393,12 @@ private:
std::vector<std::unique_ptr<RDeleter>> fItemDeleters;

public:
RVariantDeleter(std::size_t tagOffset, std::size_t variantOffset,
RVariantDeleter(std::size_t tagOffset, std::size_t variantOffset, std::size_t alignment,
std::vector<std::unique_ptr<RDeleter>> itemDeleters)
: fTagOffset(tagOffset), fVariantOffset(variantOffset), fItemDeleters(std::move(itemDeleters))
: RDeleter(alignment),
fTagOffset(tagOffset),
fVariantOffset(variantOffset),
fItemDeleters(std::move(itemDeleters))
{
}
void operator()(void *objPtr, bool dtorOnly) final;
Expand Down Expand Up @@ -436,8 +444,8 @@ public:
RVariantField &operator=(RVariantField &&other) = default;
~RVariantField() override = default;

size_t GetValueSize() const final;
size_t GetAlignment() const final;
std::size_t GetValueSize() const final;
std::size_t GetAlignment() const final;
};

template <typename... ItemTs>
Expand Down
34 changes: 19 additions & 15 deletions tree/ntuple/inc/ROOT/RField/RFieldSequenceContainer.hxx
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Expand Up @@ -51,8 +51,9 @@ private:
std::unique_ptr<RDeleter> fItemDeleter;

public:
RArrayDeleter(std::size_t itemSize, std::size_t arrayLength, std::unique_ptr<RDeleter> itemDeleter)
: fItemSize(itemSize), fArrayLength(arrayLength), fItemDeleter(std::move(itemDeleter))
RArrayDeleter(std::size_t itemSize, std::size_t arrayLength, std::size_t alignment,
std::unique_ptr<RDeleter> itemDeleter)
: RDeleter(alignment), fItemSize(itemSize), fArrayLength(arrayLength), fItemDeleter(std::move(itemDeleter))
{
}
void operator()(void *objPtr, bool dtorOnly) final;
Expand Down Expand Up @@ -126,9 +127,15 @@ class RRVecField : public RFieldBase {
std::unique_ptr<RDeleter> fItemDeleter;

public:
explicit RRVecDeleter(std::size_t itemAlignment) : fItemAlignment(itemAlignment) {}
explicit RRVecDeleter(std::size_t itemAlignment)
: RDeleter(ROOT::Internal::EvalRVecAlignment(itemAlignment)), fItemAlignment(itemAlignment)
{
}
RRVecDeleter(std::size_t itemAlignment, std::size_t itemSize, std::unique_ptr<RDeleter> itemDeleter)
: fItemAlignment(itemAlignment), fItemSize(itemSize), fItemDeleter(std::move(itemDeleter))
: RDeleter(ROOT::Internal::EvalRVecAlignment(itemAlignment)),
fItemAlignment(itemAlignment),
fItemSize(itemSize),
fItemDeleter(std::move(itemDeleter))
{
}
void operator()(void *objPtr, bool dtorOnly) final;
Expand Down Expand Up @@ -211,11 +218,8 @@ class RVectorField : public RFieldBase {
std::unique_ptr<RDeleter> fItemDeleter;

public:
RVectorDeleter() = default;
RVectorDeleter(std::size_t itemSize, std::unique_ptr<RDeleter> itemDeleter)
: fItemSize(itemSize), fItemDeleter(std::move(itemDeleter))
{
}
RVectorDeleter();
RVectorDeleter(std::size_t itemSize, std::unique_ptr<RDeleter> itemDeleter);
void operator()(void *objPtr, bool dtorOnly) final;
};

Expand Down Expand Up @@ -261,8 +265,8 @@ public:
CreateUntyped(std::string_view fieldName, std::unique_ptr<RFieldBase> itemField);

std::vector<RValue> SplitValue(const RValue &value) const final;
size_t GetValueSize() const final { return sizeof(std::vector<char>); }
size_t GetAlignment() const final { return std::alignment_of<std::vector<char>>(); }
std::size_t GetValueSize() const final;
std::size_t GetAlignment() const final;
void AcceptVisitor(ROOT::Detail::RFieldVisitor &visitor) const final;
};

Expand Down Expand Up @@ -315,8 +319,8 @@ public:

std::vector<RValue> SplitValue(const RValue &value) const final;

size_t GetValueSize() const final { return sizeof(std::vector<bool>); }
size_t GetAlignment() const final { return std::alignment_of<std::vector<bool>>(); }
std::size_t GetValueSize() const final { return sizeof(std::vector<bool>); }
std::size_t GetAlignment() const final { return alignof(std::vector<bool>); }
void AcceptVisitor(ROOT::Detail::RFieldVisitor &visitor) const final;
};

Expand Down Expand Up @@ -410,8 +414,8 @@ public:
RArrayAsVectorField &operator=(RArrayAsVectorField &&other) = default;
~RArrayAsVectorField() final = default;

size_t GetValueSize() const final { return sizeof(std::vector<char>); }
size_t GetAlignment() const final { return std::alignment_of<std::vector<char>>(); }
std::size_t GetValueSize() const final;
std::size_t GetAlignment() const final;

std::vector<RFieldBase::RValue> SplitValue(const RFieldBase::RValue &value) const final;
void AcceptVisitor(ROOT::Detail::RFieldVisitor &visitor) const final;
Expand Down
5 changes: 2 additions & 3 deletions tree/ntuple/inc/ROOT/RField/RFieldSoA.hxx
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Expand Up @@ -58,7 +58,7 @@ class RSoAField : public RFieldBase {
TClass *fSoAClass;

public:
explicit RSoADeleter(TClass *cl) : fSoAClass(cl) {}
explicit RSoADeleter(TClass *cl);
void operator()(void *objPtr, bool dtorOnly) final;
};

Expand All @@ -67,7 +67,6 @@ class RSoAField : public RFieldBase {
/// The offset of the RVec members in the SoA type in the order of subfields of the underlying record type.
/// In particular, the order is not necessarily the same then the order of RVec members in the SoA class.
std::vector<std::size_t> fSoAMemberOffsets;
std::size_t fMaxAlignment = 1;
ROOT::Internal::RColumnIndex fNWritten;

RSoAField(std::string_view fieldName, const RSoAField &source); ///< Used by CloneImpl
Expand Down Expand Up @@ -98,7 +97,7 @@ public:

std::vector<RValue> SplitValue(const RValue &value) const final;
size_t GetValueSize() const final;
size_t GetAlignment() const final { return fMaxAlignment; }
size_t GetAlignment() const final;
std::uint32_t GetTypeVersion() const final;
std::uint32_t GetTypeChecksum() const final;
/// For polymorphic classes (that declare or inherit at least one virtual method), return the expected dynamic type
Expand Down
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