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QList::iterator: use templates for advancing operators 

Because of the addition of the operator T*(), the expression "it + N"
where N was not exactly qsizetype but any other integer type was a
compilation failure because of ambiguous overload resolution.

With GCC it's apparently a warning:

 warning: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second:
 note: candidate 1: ‘QList<T>::iterator QList<T>::iterator::operator+(qsizetype) const [with T = char; qsizetype = long long int]’
 note: candidate 2: ‘operator+(char*, ptrdiff_t {aka long int})’ (built-in)

With Clang, it's an error:

 error: use of overloaded operator '+' is ambiguous (with operand types 'QList<int>::const_iterator' and 'ptrdiff_t' (aka 'long'))
 note: candidate function
        inline const_iterator operator+(qsizetype j) const { return const_iterator(i+j); }
 note: built-in candidate operator+(const int *, long)

Pick-to: 6.2
Fixes: QTBUG-96128
Change-Id: Ie72b0dd0fbe84d2caae0fffd16a06f23dd56b060
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
bb10
Thiago Macieira 2021-08-31 08:54:24 -07:00
parent 2675c288e8
commit 878b2047b5
2 changed files with 156 additions and 10 deletions
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32
src/corelib/tools/qlist.h
View File

@ -162,13 +162,19 @@ public:
inline iterator operator++(int) { T *n = i; ++i; return n; }
inline iterator &operator--() { i--; return *this; }
inline iterator operator--(int) { T *n = i; i--; return n; }
inline iterator &operator+=(qsizetype j) { i+=j; return *this; }
inline iterator &operator-=(qsizetype j) { i-=j; return *this; }
inline iterator operator+(qsizetype j) const { return iterator(i+j); }
inline iterator operator-(qsizetype j) const { return iterator(i-j); }
friend inline iterator operator+(qsizetype j, iterator k) { return k + j; }
inline qsizetype operator-(iterator j) const { return i - j.i; }
inline operator T*() const { return i; }
template <typename Int> std::enable_if_t<std::is_integral_v<Int>, iterator>
&operator+=(Int j) { i+=j; return *this; }
template <typename Int> std::enable_if_t<std::is_integral_v<Int>, iterator>
&operator-=(Int j) { i-=j; return *this; }
template <typename Int> std::enable_if_t<std::is_integral_v<Int>, iterator>
operator+(Int j) const { return iterator(i+j); }
template <typename Int> std::enable_if_t<std::is_integral_v<Int>, iterator>
operator-(Int j) const { return iterator(i-j); }
template <typename Int> friend std::enable_if_t<std::is_integral_v<Int>, iterator>
operator+(Int j, iterator k) { return k + j; }
};
class const_iterator {
@ -206,13 +212,19 @@ public:
inline const_iterator operator++(int) { const T *n = i; ++i; return n; }
inline const_iterator &operator--() { i--; return *this; }
inline const_iterator operator--(int) { const T *n = i; i--; return n; }
inline const_iterator &operator+=(qsizetype j) { i+=j; return *this; }
inline const_iterator &operator-=(qsizetype j) { i-=j; return *this; }
inline const_iterator operator+(qsizetype j) const { return const_iterator(i+j); }
inline const_iterator operator-(qsizetype j) const { return const_iterator(i-j); }
friend inline const_iterator operator+(qsizetype j, const_iterator k) { return k + j; }
inline qsizetype operator-(const_iterator j) const { return i - j.i; }
inline operator const T*() const { return i; }
template <typename Int> std::enable_if_t<std::is_integral_v<Int>, const_iterator>
&operator+=(Int j) { i+=j; return *this; }
template <typename Int> std::enable_if_t<std::is_integral_v<Int>, const_iterator>
&operator-=(Int j) { i-=j; return *this; }
template <typename Int> std::enable_if_t<std::is_integral_v<Int>, const_iterator>
operator+(Int j) const { return const_iterator(i+j); }
template <typename Int> std::enable_if_t<std::is_integral_v<Int>, const_iterator>
operator-(Int j) const { return const_iterator(i-j); }
template <typename Int> friend std::enable_if_t<std::is_integral_v<Int>, const_iterator>
operator+(Int j, const_iterator k) { return k + j; }
};
using Iterator = iterator;
using ConstIterator = const_iterator;

134
tests/auto/corelib/tools/qlist/tst_qlist.cpp
View File

@ -2404,30 +2404,97 @@ void tst_QList::iterators() const
idx = 0;
auto it = v.begin();
QCOMPARE(*it, idx);
// idx == 0
std::advance(it, 7);
idx += 7;
QCOMPARE(*it, idx);
// idx == 7
it++;
idx++;
QCOMPARE(*it, idx);
// idx == 8
++it;
++idx;
QCOMPARE(*it, idx);
// idx == 9
std::advance(it, -3);
idx -= 3;
QCOMPARE(*it, idx);
// idx == 6
it--;
idx--;
QCOMPARE(*it, idx);
// idx == 5
--it;
--idx;
QCOMPARE(*it, idx);
// idx == 4
it = it + 1;
idx = idx + 1;
QCOMPARE(*it, idx);
// idx == 5
it = it + ptrdiff_t(1);
idx = idx + 1;
QCOMPARE(*it, idx);
// idx == 6
it = it + qsizetype(1);
idx = idx + 1;
QCOMPARE(*it, idx);
// idx == 7
it = it - qsizetype(1);
idx = idx - 1;
QCOMPARE(*it, idx);
// idx == 6
it = it - ptrdiff_t(1);
idx = idx - 1;
QCOMPARE(*it, idx);
// idx == 5
it = it - 1;
idx = idx - 1;
QCOMPARE(*it, idx);
// idx == 4
it -= 1;
idx -= 1;
QCOMPARE(*it, idx);
// idx == 3
it -= qsizetype(1);
idx -= 1;
QCOMPARE(*it, idx);
// idx == 2
it -= ptrdiff_t(1);
idx -= 1;
QCOMPARE(*it, idx);
// idx == 1
it += ptrdiff_t(1);
idx += 1;
QCOMPARE(*it, idx);
// idx == 2
it += qsizetype(1);
idx += 1;
QCOMPARE(*it, idx);
// idx == 3
it += 1;
idx += 1;
QCOMPARE(*it, idx);
// idx == 4
*it = idx + 1;
QCOMPARE(*it, idx + 1);
@ -2484,30 +2551,97 @@ void tst_QList::constIterators() const
qsizetype idx = 0;
auto it = v.cbegin();
QCOMPARE(*it, idx);
// idx == 0
std::advance(it, 7);
idx += 7;
QCOMPARE(*it, idx);
// idx == 7
it++;
idx++;
QCOMPARE(*it, idx);
// idx == 8
++it;
++idx;
QCOMPARE(*it, idx);
// idx == 9
std::advance(it, -3);
idx -= 3;
QCOMPARE(*it, idx);
// idx == 6
it--;
idx--;
QCOMPARE(*it, idx);
// idx == 5
--it;
--idx;
QCOMPARE(*it, idx);
// idx == 4
it = it + 1;
idx = idx + 1;
QCOMPARE(*it, idx);
// idx == 5
it = it + ptrdiff_t(1);
idx = idx + 1;
QCOMPARE(*it, idx);
// idx == 6
it = it + qsizetype(1);
idx = idx + 1;
QCOMPARE(*it, idx);
// idx == 7
it = it - qsizetype(1);
idx = idx - 1;
QCOMPARE(*it, idx);
// idx == 6
it = it - ptrdiff_t(1);
idx = idx - 1;
QCOMPARE(*it, idx);
// idx == 5
it = it - 1;
idx = idx - 1;
QCOMPARE(*it, idx);
// idx == 4
it -= 1;
idx -= 1;
QCOMPARE(*it, idx);
// idx == 3
it -= qsizetype(1);
idx -= 1;
QCOMPARE(*it, idx);
// idx == 2
it -= ptrdiff_t(1);
idx -= 1;
QCOMPARE(*it, idx);
// idx == 1
it += ptrdiff_t(1);
idx += 1;
QCOMPARE(*it, idx);
// idx == 2
it += qsizetype(1);
idx += 1;
QCOMPARE(*it, idx);
// idx == 3
it += 1;
idx += 1;
QCOMPARE(*it, idx);
// idx == 4
// stl-style reverse iterators
idx = v.size() - 1;