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QHash: fix qHash(std::pair)

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There were two problems here: first, qHash(std::pair) must be declared
before qHashMulti that might call back to qHash(std::pair) (i.e., a pair
with one element that is also a pair). But moving the declaration above
causes the second problem: the noexcept expression can't refer to qHash
functions that aren't declared yet. So we forward-declare a constexpr
function for that result, but implement it far below.

Fixes: QTBUG-92910
Change-Id: Ia8e48103a54446509e3bfffd16767ed2e29b026c
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This commit is contained in:
Thiago Macieira 2021-04-16 17:49:20 -07:00
parent a5ff71578d
commit 64bfc927b0
2 changed files with 55 additions and 2 deletions
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17
src/corelib/tools/qhashfunctions.h
View File

@ -114,10 +114,15 @@ constexpr inline bool HasQHashSingleArgOverload<T, std::enable_if_t<
std::is_convertible_v<decltype(qHash(std::declval<const T &>())), size_t>
>> = true;
template <typename T1, typename T2> static constexpr bool noexceptPairHash();
}
Q_CORE_EXPORT Q_DECL_PURE_FUNCTION size_t qHashBits(const void *p, size_t size, size_t seed = 0) noexcept;
// implementation below qHashMulti
template <typename T1, typename T2> inline size_t qHash(const std::pair<T1, T2> &key, size_t seed = 0)
noexcept(QHashPrivate::noexceptPairHash<T1, T2>());
// C++ builtin types
Q_DECL_CONST_FUNCTION constexpr inline size_t qHash(char key, size_t seed = 0) noexcept
{ return QHashPrivate::hash(size_t(key), seed); }
@ -290,8 +295,16 @@ inline size_t qHashRangeCommutative(InputIterator first, InputIterator last, siz
return std::accumulate(first, last, seed, QtPrivate::QHashCombineCommutative());
}
template <typename T1, typename T2> inline size_t qHash(const std::pair<T1, T2> &key, size_t seed = 0)
noexcept(noexcept(qHash(key.first, seed)) && noexcept(qHash(key.second, seed)))
namespace QHashPrivate {
template <typename T1, typename T2> static constexpr bool noexceptPairHash()
{
size_t seed = 0;
return noexcept(qHash(std::declval<T1>(), seed)) && noexcept(qHash(std::declval<T2>(), seed));
}
} // QHashPrivate
template <typename T1, typename T2> inline size_t qHash(const std::pair<T1, T2> &key, size_t seed)
noexcept(QHashPrivate::noexceptPairHash<T1, T2>())
{
return qHashMulti(seed, key.first, key.second);
}

40
tests/auto/corelib/tools/qhashfunctions/tst_qhashfunctions.cpp
View File

@ -46,6 +46,8 @@ public:
};
uint seed;
template <typename T1, typename T2> void stdPair_template(const T1 &t1, const T2 &t2);
public slots:
void initTestCase();
void init();
@ -63,6 +65,18 @@ private Q_SLOTS:
void stdHash();
void stdPair_int_int() { stdPair_template(1, 2); }
void stdPair_ulong_llong() { stdPair_template(1UL, -2LL); }
void stdPair_ullong_long() { stdPair_template(1ULL, -2L); }
void stdPair_string_int() { stdPair_template(QString("Hello"), 2); }
void stdPair_int_string() { stdPair_template(1, QString("Hello")); }
void stdPair_bytearray_string() { stdPair_template(QByteArray("Hello"), QString("World")); }
void stdPair_string_bytearray() { stdPair_template(QString("Hello"), QByteArray("World")); }
void stdPair_int_pairIntInt() { stdPair_template(1, std::make_pair(2, 3)); }
void stdPair_2x_pairIntInt() { stdPair_template(std::make_pair(1, 2), std::make_pair(2, 3)); }
void stdPair_string_pairIntInt() { stdPair_template(QString("Hello"), std::make_pair(42, -47)); } // QTBUG-92910
void stdPair_int_pairIntPairIntInt() { stdPair_template(1, std::make_pair(2, std::make_pair(3, 4))); }
void setGlobalQHashSeed();
};
@ -310,6 +324,32 @@ void tst_QHashFunctions::stdHash()
}
template <typename T1, typename T2>
void tst_QHashFunctions::stdPair_template(const T1 &t1, const T2 &t2)
{
std::pair<T1, T2> dpair{};
std::pair<T1, T2> vpair{t1, t2};
size_t seed = QHashSeed::globalSeed();
// confirm proper working of the pair and of the underlying types
QVERIFY(t1 == t1);
QVERIFY(t2 == t2);
QCOMPARE(qHash(t1), qHash(t1));
QCOMPARE(qHash(t2), qHash(t2));
QCOMPARE(qHash(t1, seed), qHash(t1, seed));
QCOMPARE(qHash(t2, seed), qHash(t2, seed));
QVERIFY(dpair == dpair);
QVERIFY(vpair == vpair);
// therefore their hashes should be equal
QCOMPARE(qHash(dpair), qHash(dpair));
QCOMPARE(qHash(dpair, seed), qHash(dpair, seed));
QCOMPARE(qHash(vpair), qHash(vpair));
QCOMPARE(qHash(vpair, seed), qHash(vpair, seed));
}
void tst_QHashFunctions::setGlobalQHashSeed()
{
// Setter works as advertised