QStringConverter: fix -Wc++20-compat

GCC 13 warns:

  qstringconverter_p.h:29:6: warning: identifier ‘char8_t’ is a keyword in C++20 [-Wc++20-compat]
     29 | enum char8_t : uchar {};

Fix by calling the replacement qchar8_t (and making it a typedef to
char8_t when the latter is available).

Pick-to: 6.4 6.3 6.2
Change-Id: If59a9d55667bf1f5245e3a34189687995b000daa
Reviewed-by: Ville Voutilainen <ville.voutilainen@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

2 files changed, 11 insertions, 9 deletions

diff --git a/src/corelib/text/qstringconverter.cpp b/src/corelib/text/qstringconverter.cpp
index 0217dc1fe8..c5d17e399e 100644
--- a/src/corelib/text/qstringconverter.cpp
+++ b/src/corelib/text/qstringconverter.cpp
@@ -250,7 +250,7 @@ static inline const uchar *simdFindNonAscii(const uchar *src, const uchar *end,
 
 // Compare only the US-ASCII beginning of [src8, end8) and [src16, end16)
 // and advance src8 and src16 to the first character that could not be compared
-static void simdCompareAscii(const char8_t *&src8, const char8_t *end8, const char16_t *&src16, const char16_t *end16)
+static void simdCompareAscii(const qchar8_t *&src8, const qchar8_t *end8, const char16_t *&src16, const char16_t *end16)
 {
     int bitSpacing = 1;
     qptrdiff len = qMin(end8 - src8, end16 - src16);
@@ -436,7 +436,7 @@ static inline const uchar *simdFindNonAscii(const uchar *src, const uchar *end,
     return src;
 }
 
-static void simdCompareAscii(const char8_t *&, const char8_t *, const char16_t *&, const char16_t *)
+static void simdCompareAscii(const qchar8_t *&, const qchar8_t *, const char16_t *&, const char16_t *)
 {
 }
 #else
@@ -456,7 +456,7 @@ static inline const uchar *simdFindNonAscii(const uchar *src, const uchar *end,
     return src;
 }
 
-static void simdCompareAscii(const char8_t *&, const char8_t *, const char16_t *&, const char16_t *)
+static void simdCompareAscii(const qchar8_t *&, const qchar8_t *, const char16_t *&, const char16_t *)
 {
 }
 #endif
@@ -807,7 +807,7 @@ QUtf8::ValidUtf8Result QUtf8::isValidUtf8(QByteArrayView in)
 
 int QUtf8::compareUtf8(QByteArrayView utf8, QStringView utf16) noexcept
 {
-    auto src1 = reinterpret_cast<const char8_t *>(utf8.data());
+    auto src1 = reinterpret_cast<const qchar8_t *>(utf8.data());
     auto end1 = src1 + utf8.size();
     auto src2 = reinterpret_cast<const char16_t *>(utf16.data());
     auto end2 = src2 + utf16.size();
diff --git a/src/corelib/text/qstringconverter_p.h b/src/corelib/text/qstringconverter_p.h
index 7533e094a9..5929fe0800 100644
--- a/src/corelib/text/qstringconverter_p.h
+++ b/src/corelib/text/qstringconverter_p.h
@@ -24,7 +24,9 @@
 QT_BEGIN_NAMESPACE
 
 #ifndef __cpp_char8_t
-enum char8_t : uchar {};
+enum qchar8_t : uchar {};
+#else
+using qchar8_t = char8_t;
 #endif
 
 struct QUtf8BaseTraits
@@ -38,25 +40,25 @@ struct QUtf8BaseTraits
     static void appendByte(uchar *&ptr, uchar b)
     { *ptr++ = b; }
 
-    static void appendByte(char8_t *&ptr, char8_t b)
+    static void appendByte(qchar8_t *&ptr, qchar8_t b)
     { *ptr++ = b; }
 
     static uchar peekByte(const uchar *ptr, qsizetype n = 0)
     { return ptr[n]; }
 
-    static uchar peekByte(const char8_t *ptr, qsizetype n = 0)
+    static uchar peekByte(const qchar8_t *ptr, qsizetype n = 0)
     { return ptr[n]; }
 
     static qptrdiff availableBytes(const uchar *ptr, const uchar *end)
     { return end - ptr; }
 
-    static qptrdiff availableBytes(const char8_t *ptr, const char8_t *end)
+    static qptrdiff availableBytes(const qchar8_t *ptr, const qchar8_t *end)
     { return end - ptr; }
 
     static void advanceByte(const uchar *&ptr, qsizetype n = 1)
     { ptr += n; }
 
-    static void advanceByte(const char8_t *&ptr, qsizetype n = 1)
+    static void advanceByte(const qchar8_t *&ptr, qsizetype n = 1)
     { ptr += n; }
 
     static void appendUtf16(char16_t *&ptr, char16_t uc)