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-rw-r--r--src/corelib/text/qchar.cpp53
-rw-r--r--src/corelib/text/qchar.h19
-rw-r--r--src/corelib/text/qstring.cpp4
3 files changed, 69 insertions, 7 deletions
diff --git a/src/corelib/text/qchar.cpp b/src/corelib/text/qchar.cpp
index 14c82c7ee4..dcc36d18ce 100644
--- a/src/corelib/text/qchar.cpp
+++ b/src/corelib/text/qchar.cpp
@@ -158,6 +158,12 @@ QT_BEGIN_NAMESPACE
to construct a QChar from an 8-bit \c char, and you will need to
call toLatin1() to get the 8-bit value back.
+ Starting with Qt 6.0, most QChar constructors are \c explicit. This
+ is done to avoid dangerous mistakes when accidentally mixing
+ integral types and strings. You can opt-out (and make these
+ constructors implicit) by defining the macro \c
+ QT_IMPLICIT_QCHAR_CONSTRUCTION.
+
For more information see
\l{http://www.unicode.org/ucd/}{"About the Unicode Character Database"}.
@@ -2118,4 +2124,51 @@ static bool normalizationQuickCheckHelper(QString *str, QString::NormalizationFo
return true;
}
+/*!
+ \macro QT_IMPLICIT_QCHAR_CONSTRUCTION
+ \since 6.0
+ \relates QChar
+
+ Defining this macro makes certain QChar constructors implicit
+ rather than explicit. This is done to enforce safe conversions:
+
+ \badcode
+
+ QString str = getString();
+ if (str == 123) {
+ // Oops, meant str == "123". By default does not compile,
+ // *unless* this macro is defined, in which case, it's interpreted
+ // as `if (str == QChar(123))`, that is, `if (str == '{')`.
+ // Likely, not what we meant.
+ }
+
+ \endcode
+
+ This macro is provided to keep existing code working; it is
+ recommended to instead use explicit conversions and/or QLatin1Char.
+ For instance:
+
+ \code
+
+ QChar c1 = 'x'; // OK, unless QT_NO_CAST_FROM_ASCII is defined
+ QChar c2 = u'x'; // always OK, recommended
+ QChar c3 = QLatin1Char('x'); // always OK, recommended
+
+ // from int to 1 UTF-16 code unit: must guarantee that the input is <= 0xFFFF
+ QChar c4 = 120; // compile error, unless QT_IMPLICIT_QCHAR_CONSTRUCTION is defined
+ QChar c5(120); // OK (direct initialization)
+ auto c6 = QChar(120); // ditto
+
+ // from int/char32_t to 1/2 UTF-16 code units:
+ // 𝄞 'MUSICAL SYMBOL G CLEF' (U+1D11E)
+ auto c7 = QChar(0x1D11E); // compiles, but undefined behavior at runtime
+ auto c8 = QChar::fromUcs4(0x1D11E); // always OK
+ auto c9 = QChar::fromUcs4(U'\U0001D11E'); // always OK
+ // => use c8/c9 as QStringView objects
+
+ \endcode
+
+ \sa QLatin1Char, QChar::fromUcs4, QT_NO_CAST_FROM_ASCII
+*/
+
QT_END_NAMESPACE
diff --git a/src/corelib/text/qchar.h b/src/corelib/text/qchar.h
index 982abe9346..f66671e27c 100644
--- a/src/corelib/text/qchar.h
+++ b/src/corelib/text/qchar.h
@@ -101,12 +101,18 @@ public:
LastValidCodePoint = 0x10ffff
};
+#ifdef QT_IMPLICIT_QCHAR_CONSTRUCTION
+#define QCHAR_MAYBE_IMPLICIT Q_IMPLICIT
+#else
+#define QCHAR_MAYBE_IMPLICIT explicit
+#endif
+
constexpr Q_IMPLICIT QChar() noexcept : ucs(0) {}
constexpr Q_IMPLICIT QChar(ushort rc) noexcept : ucs(rc) {}
- constexpr Q_IMPLICIT QChar(uchar c, uchar r) noexcept : ucs(char16_t((r << 8) | c)) {}
+ constexpr QCHAR_MAYBE_IMPLICIT QChar(uchar c, uchar r) noexcept : ucs(char16_t((r << 8) | c)) {}
constexpr Q_IMPLICIT QChar(short rc) noexcept : ucs(char16_t(rc)) {}
- constexpr Q_IMPLICIT QChar(uint rc) noexcept : ucs(char16_t(rc & 0xffff)) {}
- constexpr Q_IMPLICIT QChar(int rc) noexcept : ucs(char16_t(rc & 0xffff)) {}
+ constexpr QCHAR_MAYBE_IMPLICIT QChar(uint rc) noexcept : ucs(char16_t(rc & 0xffff)) {}
+ constexpr QCHAR_MAYBE_IMPLICIT QChar(int rc) noexcept : ucs(char16_t(rc & 0xffff)) {}
constexpr Q_IMPLICIT QChar(SpecialCharacter s) noexcept : ucs(char16_t(s)) {} // implicit
constexpr Q_IMPLICIT QChar(QLatin1Char ch) noexcept : ucs(ch.unicode()) {} // implicit
constexpr Q_IMPLICIT QChar(char16_t ch) noexcept : ucs(ch) {} // implicit
@@ -114,18 +120,19 @@ public:
static_assert(sizeof(wchar_t) == sizeof(char16_t));
#endif
#if defined(Q_OS_WIN) || defined(Q_CLANG_QDOC)
-# if !defined(_WCHAR_T_DEFINED) || defined(_NATIVE_WCHAR_T_DEFINED)
constexpr Q_IMPLICIT QChar(wchar_t ch) noexcept : ucs(char16_t(ch)) {} // implicit
-# endif
#endif
#ifndef QT_NO_CAST_FROM_ASCII
+ // Always implicit -- allow for 'x' => QChar conversions
QT_ASCII_CAST_WARN constexpr Q_IMPLICIT QChar(char c) noexcept : ucs(uchar(c)) { }
#ifndef QT_RESTRICTED_CAST_FROM_ASCII
- QT_ASCII_CAST_WARN constexpr Q_IMPLICIT QChar(uchar c) noexcept : ucs(c) { }
+ QT_ASCII_CAST_WARN constexpr QCHAR_MAYBE_IMPLICIT QChar(uchar c) noexcept : ucs(c) { }
#endif
#endif
+#undef QCHAR_MAYBE_IMPLICIT
+
static constexpr QChar fromUcs2(char16_t c) noexcept { return QChar{c}; }
static constexpr inline auto fromUcs4(char32_t c) noexcept;
diff --git a/src/corelib/text/qstring.cpp b/src/corelib/text/qstring.cpp
index 1447b5b21c..c955cb8736 100644
--- a/src/corelib/text/qstring.cpp
+++ b/src/corelib/text/qstring.cpp
@@ -1509,8 +1509,10 @@ inline char qToLower(char ch)
/*!
\macro QT_NO_CAST_FROM_ASCII
\relates QString
+ \relates QChar
- Disables automatic conversions from 8-bit strings (char *) to unicode QStrings
+ Disables automatic conversions from 8-bit strings (char *) to unicode QStrings,
+ as well as from 8-bit char types (char and unsigned char) to QChar.
\sa QT_NO_CAST_TO_ASCII, QT_RESTRICTED_CAST_FROM_ASCII, QT_NO_CAST_FROM_BYTEARRAY
*/