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author | Giuseppe D'Angelo <giuseppe.dangelo@kdab.com> | 2017-07-19 15:22:15 +0200 |
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committer | Giuseppe D'Angelo <giuseppe.dangelo@kdab.com> | 2017-07-20 20:53:34 +0000 |
commit | 548c2fbb3aa1ae6b7d3614b6381ea051977e2834 (patch) | |
tree | c0b6f4ea9dd1ed99da2150ab8a5bd4723da144c2 /src/corelib/tools/qhash.h | |
parent | 82f701ed00546a01602413e90390388a1ec6dfbe (diff) |
QHash: make MSVC happy about the iterators passed to is_permutation
MSVC warns about iterators being passed to certain Standard Library
algorithms. dbd55cdaf367bdc9d6774bcb9927cbe19f18065f introduced
a usa of std::is_permutation in a public header, which is causing
such a warning to be emitted.
To suppress the warning, Microsoft suggests to either use the 4-arg
std::is_permutation overload (which however is not available
in MSVC 2013) or to use a Standard Library extension, which we are
already using elsewhere in Qt to deal with the same problem. However,
that extension requires the iterator to be moved by size_t quantities,
which isn't the case for QHash::iterator, and therefore generates
more warnings about loss of precision (size_t -> int).
Therefore, go with the 4-arg std::is_permutation, only on MSVC >= 2015.
Change-Id: Idfcff28d14e0f1fde5d77f1deb9eec27c87ff5cd
Task-number: QTBUG-61902
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Diffstat (limited to 'src/corelib/tools/qhash.h')
-rw-r--r-- | src/corelib/tools/qhash.h | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/src/corelib/tools/qhash.h b/src/corelib/tools/qhash.h index 035ec57957..703066857d 100644 --- a/src/corelib/tools/qhash.h +++ b/src/corelib/tools/qhash.h @@ -950,8 +950,22 @@ Q_OUTOFLINE_TEMPLATE bool QHash<Key, T>::operator==(const QHash &other) const return false; // Keys in the ranges are equal by construction; this checks only the values. - if (!std::is_permutation(it, thisEqualRangeEnd, otherEqualRange.first)) + // + // When using the 3-arg std::is_permutation, MSVC will emit warning C4996, + // passing an unchecked iterator to a Standard Library algorithm. We don't + // want to suppress the warning, and we can't use stdext::make_checked_array_iterator + // because QHash::(const_)iterator does not work with size_t and thus will + // emit more warnings. Use the 4-arg std::is_permutation instead (which + // is supported since MSVC 2015). + // + // ### Qt 6: if C++14 library support is a mandated minimum, remove the ifdef for MSVC. + if (!std::is_permutation(it, thisEqualRangeEnd, otherEqualRange.first +#if defined(Q_CC_MSVC) && _MSC_VER >= 1900 + , otherEqualRange.second +#endif + )) { return false; + } it = thisEqualRangeEnd; } |