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QHash: suppress annoying GCC warning about allocation size too big

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GCC is right, the maximum memory allocation is half the VM size,
not the full VM size or multiple times that. QHashPrivate::Span
is big.

 qhash.h:552:17: warning: argument 1 value ‘18446744073709551615’ exceeds maximum object size 9223372036854775807 [-Walloc-size-larger-than=]

Change-Id: Ie72b0dd0fbe84d2caae0fffd16a071ffb5d0c70f
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
This commit is contained in:
Thiago Macieira 2021-08-31 09:46:48 -07:00
parent 0e100a4d89
commit b07345504c
1 changed files with 31 additions and 20 deletions
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51
src/corelib/tools/qhash.h
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@ -102,26 +102,6 @@ size_t calculateHash(const T &t, size_t seed = 0)
}
}
// QHash uses a power of two growth policy.
namespace GrowthPolicy {
inline constexpr size_t maxNumBuckets() noexcept
{
return size_t(1) << (8 * sizeof(size_t) - 1);
}
inline constexpr size_t bucketsForCapacity(size_t requestedCapacity) noexcept
{
if (requestedCapacity <= 8)
return 16;
if (requestedCapacity >= maxNumBuckets())
return maxNumBuckets();
return qNextPowerOfTwo(QIntegerForSize<sizeof(size_t)>::Unsigned(2 * requestedCapacity - 1));
}
inline constexpr size_t bucketForHash(size_t nBuckets, size_t hash) noexcept
{
return hash & (nBuckets - 1);
}
}
template <typename Key, typename T>
struct Node
{
@ -453,6 +433,37 @@ struct Span {
}
};
// QHash uses a power of two growth policy.
namespace GrowthPolicy {
inline constexpr size_t maxNumBuckets() noexcept
{
// ensure the size of a Span does not depend on the template parameters
using Node1 = Node<int, int>;
using Node2 = Node<char, void *>;
using Node3 = Node<qsizetype, QHashDummyValue>;
static_assert(sizeof(Span<Node1>) == sizeof(Span<Node2>));
static_assert(sizeof(Span<Node1>) == sizeof(Span<Node3>));
static_assert(int(Span<Node1>::NEntries) == int(Span<Node2>::NEntries));
static_assert(int(Span<Node1>::NEntries) == int(Span<Node3>::NEntries));
// Maximum is 2^31-1 or 2^63-1 bytes (limited by qsizetype and ptrdiff_t)
size_t max = (std::numeric_limits<ptrdiff_t>::max)();
return max / sizeof(Span<Node1>) * Span<Node1>::NEntries;
}
inline constexpr size_t bucketsForCapacity(size_t requestedCapacity) noexcept
{
if (requestedCapacity <= 8)
return 16;
if (requestedCapacity >= maxNumBuckets())
return maxNumBuckets();
return qNextPowerOfTwo(QIntegerForSize<sizeof(size_t)>::Unsigned(2 * requestedCapacity - 1));
}
inline constexpr size_t bucketForHash(size_t nBuckets, size_t hash) noexcept
{
return hash & (nBuckets - 1);
}
} // namespace GrowthPolicy
template <typename Node>
struct iterator;