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QByteArray/QList/QString: mark size() constexpr and always in-range

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Using the C++20 [[assume]] attribute, which GCC and Clang support in
C++17 mode too. This may help the compiler generate slightly better
code, avoiding the need to check if the size is negative or overflows.

I've also marked count() and length() as constexpr.

Change-Id: Ida6c9a7ba67574a952f3fffd44dea52a0e0e61c2
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
This commit is contained in:
Thiago Macieira 2025-01-27 16:54:58 -08:00
parent 68cac07d50
commit 84467d70a8
3 changed files with 30 additions and 9 deletions
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13
src/corelib/text/qbytearray.h
View File

@ -495,12 +495,19 @@ public:
// -1 to deal with the NUL terminator
return Data::maxSize() - 1;
}
inline qsizetype size() const noexcept { return d.size; }
constexpr qsizetype size() const noexcept
{
#if __has_cpp_attribute(assume)
constexpr size_t MaxSize = maxSize();
[[assume(size_t(d.size) <= MaxSize)]];
#endif
return d.size;
}
#if QT_DEPRECATED_SINCE(6, 4)
QT_DEPRECATED_VERSION_X_6_4("Use size() or length() instead.")
inline qsizetype count() const noexcept { return size(); }
constexpr qsizetype count() const noexcept { return size(); }
#endif
inline qsizetype length() const noexcept { return size(); }
constexpr qsizetype length() const noexcept { return size(); }
QT_CORE_INLINE_SINCE(6, 4)
bool isNull() const noexcept;

13
src/corelib/text/qstring.h
View File

@ -232,12 +232,19 @@ public:
// -1 to deal with the NUL terminator
return Data::maxSize() - 1;
}
inline qsizetype size() const noexcept { return d.size; }
constexpr qsizetype size() const noexcept
{
#if __has_cpp_attribute(assume)
constexpr size_t MaxSize = maxSize();
[[assume(size_t(d.size) <= MaxSize)]];
#endif
return d.size;
}
#if QT_DEPRECATED_SINCE(6, 4)
QT_DEPRECATED_VERSION_X_6_4("Use size() or length() instead.")
inline qsizetype count() const { return d.size; }
constexpr qsizetype count() const { return size(); }
#endif
inline qsizetype length() const noexcept { return d.size; }
constexpr qsizetype length() const noexcept { return size(); }
inline bool isEmpty() const noexcept { return d.size == 0; }
void resize(qsizetype size);
void resize(qsizetype size, QChar fillChar);

13
src/corelib/tools/qlist.h
View File

@ -438,9 +438,16 @@ public:
#endif // Q_QDOC
static constexpr qsizetype maxSize() { return Data::maxSize(); }
qsizetype size() const noexcept { return d->size; }
qsizetype count() const noexcept { return size(); }
qsizetype length() const noexcept { return size(); }
constexpr qsizetype size() const noexcept
{
#if __has_cpp_attribute(assume)
constexpr size_t MaxSize = maxSize();
[[assume(size_t(d.size) <= MaxSize)]];
#endif
return d.size;
}
constexpr qsizetype count() const noexcept { return size(); }
constexpr qsizetype length() const noexcept { return size(); }
inline bool isEmpty() const noexcept { return d->size == 0; }