From 215ca735341b9487826023a7983382851ce8bf26 Mon Sep 17 00:00:00 2001 From: Lars Knoll Date: Thu, 14 Nov 2019 16:31:07 +0100 Subject: Allow allocating more than 2G items in a vector Also adjust qCalculateBlockSize() to be able to handle large allocations. QVector::length() is currently still limited to 2G items, that will get changed in a later commit. Change-Id: I3a92fbfd7f281d30844c5fafa3b9a474bc347c19 Reviewed-by: Thiago Macieira --- src/corelib/tools/qarraydata.cpp | 92 ++++++++++++++++++---------------------- 1 file changed, 42 insertions(+), 50 deletions(-) (limited to 'src/corelib/tools/qarraydata.cpp') diff --git a/src/corelib/tools/qarraydata.cpp b/src/corelib/tools/qarraydata.cpp index 1a369a879a..f46204106d 100644 --- a/src/corelib/tools/qarraydata.cpp +++ b/src/corelib/tools/qarraydata.cpp @@ -52,7 +52,7 @@ QT_BEGIN_NAMESPACE * containers to allocate memory and grow the memory block during append * operations. * - * They take size_t parameters and return size_t so they will change sizes + * They take qsizetype parameters and return qsizetype so they will change sizes * according to the pointer width. However, knowing Qt containers store the * container size and element indexes in ints, these functions never return a * size larger than INT_MAX. This is done by casting the element count and @@ -79,29 +79,21 @@ QT_BEGIN_NAMESPACE Both \a elementCount and \a headerSize can be zero, but \a elementSize cannot. - This function returns SIZE_MAX (~0) on overflow or if the memory block size - would not fit an int. + This function returns -1 on overflow or if the memory block size + would not fit a qsizetype. */ -size_t qCalculateBlockSize(size_t elementCount, size_t elementSize, size_t headerSize) noexcept +qsizetype qCalculateBlockSize(qsizetype elementCount, qsizetype elementSize, qsizetype headerSize) noexcept { - unsigned count = unsigned(elementCount); - unsigned size = unsigned(elementSize); - unsigned header = unsigned(headerSize); Q_ASSERT(elementSize); - Q_ASSERT(size == elementSize); - Q_ASSERT(header == headerSize); - if (Q_UNLIKELY(count != elementCount)) - return std::numeric_limits::max(); + size_t bytes; + if (Q_UNLIKELY(mul_overflow(size_t(elementSize), size_t(elementCount), &bytes)) || + Q_UNLIKELY(add_overflow(bytes, size_t(headerSize), &bytes))) + return -1; + if (Q_UNLIKELY(qsizetype(bytes) < 0)) + return -1; - unsigned bytes; - if (Q_UNLIKELY(mul_overflow(size, count, &bytes)) || - Q_UNLIKELY(add_overflow(bytes, header, &bytes))) - return std::numeric_limits::max(); - if (Q_UNLIKELY(int(bytes) < 0)) // catches bytes >= 2GB - return std::numeric_limits::max(); - - return bytes; + return qsizetype(bytes); } /*! @@ -116,38 +108,39 @@ size_t qCalculateBlockSize(size_t elementCount, size_t elementSize, size_t heade Both \a elementCount and \a headerSize can be zero, but \a elementSize cannot. - This function returns SIZE_MAX (~0) on overflow or if the memory block size - would not fit an int. + This function returns -1 on overflow or if the memory block size + would not fit a qsizetype. \note The memory block may contain up to \a elementSize - 1 bytes more than needed. */ CalculateGrowingBlockSizeResult -qCalculateGrowingBlockSize(size_t elementCount, size_t elementSize, size_t headerSize) noexcept +qCalculateGrowingBlockSize(qsizetype elementCount, qsizetype elementSize, qsizetype headerSize) noexcept { CalculateGrowingBlockSizeResult result = { - std::numeric_limits::max(),std::numeric_limits::max() + qsizetype(-1), qsizetype(-1) }; - unsigned bytes = unsigned(qCalculateBlockSize(elementCount, elementSize, headerSize)); - if (int(bytes) < 0) // catches std::numeric_limits::max() + qsizetype bytes = qCalculateBlockSize(elementCount, elementSize, headerSize); + if (bytes < 0) return result; - unsigned morebytes = qNextPowerOfTwo(bytes); - if (Q_UNLIKELY(int(morebytes) < 0)) { - // catches morebytes == 2GB + size_t morebytes = static_cast(qNextPowerOfTwo(quint64(bytes))); + if (Q_UNLIKELY(qsizetype(morebytes) < 0)) { // grow by half the difference between bytes and morebytes + // this slows the growth and avoids trying to allocate exactly + // 2G of memory (on 32bit), something that many OSes can't deliver bytes += (morebytes - bytes) / 2; } else { - bytes = morebytes; + bytes = qsizetype(morebytes); } - result.elementCount = (bytes - unsigned(headerSize)) / unsigned(elementSize); + result.elementCount = (bytes - headerSize) / elementSize; result.size = result.elementCount * elementSize + headerSize; return result; } -static inline size_t calculateBlockSize(size_t &capacity, size_t objectSize, size_t headerSize, uint options) +static inline qsizetype calculateBlockSize(qsizetype &capacity, qsizetype objectSize, qsizetype headerSize, uint options) { // Calculate the byte size // allocSize = objectSize * capacity + headerSize, but checked for overflow @@ -161,9 +154,9 @@ static inline size_t calculateBlockSize(size_t &capacity, size_t objectSize, siz } } -static QArrayData *allocateData(size_t allocSize, uint options) +static QArrayData *allocateData(qsizetype allocSize, uint options) { - QArrayData *header = static_cast(::malloc(allocSize)); + QArrayData *header = static_cast(::malloc(size_t(allocSize))); if (header) { header->ref_.storeRelaxed(1); header->flags = options; @@ -172,12 +165,12 @@ static QArrayData *allocateData(size_t allocSize, uint options) return header; } -void *QArrayData::allocate(QArrayData **dptr, size_t objectSize, size_t alignment, - size_t capacity, ArrayOptions options) noexcept +void *QArrayData::allocate(QArrayData **dptr, qsizetype objectSize, qsizetype alignment, + qsizetype capacity, ArrayOptions options) noexcept { Q_ASSERT(dptr); // Alignment is a power of two - Q_ASSERT(alignment >= alignof(QArrayData) + Q_ASSERT(alignment >= qsizetype(alignof(QArrayData)) && !(alignment & (alignment - 1))); if (capacity == 0) { @@ -185,26 +178,25 @@ void *QArrayData::allocate(QArrayData **dptr, size_t objectSize, size_t alignmen return nullptr; } - size_t headerSize = sizeof(QArrayData); + qsizetype headerSize = sizeof(QArrayData); + const qsizetype headerAlignment = alignof(QArrayData); - if (alignment > alignof(QArrayData)) { + if (alignment > headerAlignment) { // Allocate extra (alignment - Q_ALIGNOF(QArrayData)) padding bytes so we // can properly align the data array. This assumes malloc is able to // provide appropriate alignment for the header -- as it should! - headerSize += alignment - alignof(QArrayData); + headerSize += alignment - headerAlignment; } + Q_ASSERT(headerSize > 0); - if (headerSize > size_t(MaxAllocSize)) - return nullptr; - - size_t allocSize = calculateBlockSize(capacity, objectSize, headerSize, options); + qsizetype allocSize = calculateBlockSize(capacity, objectSize, headerSize, options); QArrayData *header = allocateData(allocSize, options); quintptr data = 0; if (header) { // find where offset should point to so that data() is aligned to alignment bytes data = (quintptr(header) + sizeof(QArrayData) + alignment - 1) & ~(alignment - 1); - header->alloc = uint(capacity); + header->alloc = qsizetype(capacity); } *dptr = header; @@ -213,12 +205,12 @@ void *QArrayData::allocate(QArrayData **dptr, size_t objectSize, size_t alignmen QPair QArrayData::reallocateUnaligned(QArrayData *data, void *dataPointer, - size_t objectSize, size_t capacity, ArrayOptions options) noexcept + qsizetype objectSize, qsizetype capacity, ArrayOptions options) noexcept { Q_ASSERT(!data || !data->isShared()); - size_t headerSize = sizeof(QArrayData); - size_t allocSize = calculateBlockSize(capacity, objectSize, headerSize, options); + qsizetype headerSize = sizeof(QArrayData); + qsizetype allocSize = calculateBlockSize(capacity, objectSize, headerSize, options); qptrdiff offset = dataPointer ? reinterpret_cast(dataPointer) - reinterpret_cast(data) : headerSize; QArrayData *header = static_cast(::realloc(data, size_t(allocSize))); if (header) { @@ -229,11 +221,11 @@ QArrayData::reallocateUnaligned(QArrayData *data, void *dataPointer, return qMakePair(static_cast(header), dataPointer); } -void QArrayData::deallocate(QArrayData *data, size_t objectSize, - size_t alignment) noexcept +void QArrayData::deallocate(QArrayData *data, qsizetype objectSize, + qsizetype alignment) noexcept { // Alignment is a power of two - Q_ASSERT(alignment >= alignof(QArrayData) + Q_ASSERT(alignment >= qsizetype(alignof(QArrayData)) && !(alignment & (alignment - 1))); Q_UNUSED(objectSize); Q_UNUSED(alignment); -- cgit v1.2.3