Fix unused variables in qtbase

clang compiler recently got smarter and detects "pseudo used variable"
patterns where we declare a variable and only use it in self-increments,
self-decrements and other similar expressions

Errors:

qtbase/src/corelib/text/qlocale.cpp:3898:9: error: variable 'group_cnt' set but not used [-Werror,-Wunused-but-set-variable]
    int group_cnt = 0; // counts number of group chars
        ^

qtbase/src/corelib/text/qunicodetools.cpp:1372:21: error: variable 'uc' set but not used [-Werror,-Wunused-but-set-variable]
    const char16_t *uc = text + from;
                    ^
and more of the kind

Remove the ones that have no usage, mark others with [[maybe_unused]]

Pick-to: 6.3 6.2
Change-Id: Ib2d0722110e3da8c39e29ec78c0ec290d064c970
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/text/qlocale.cpp

@@ -3904,7 +3904,6 @@ bool QLocaleData::numberToCLocale(QStringView s, QLocale::NumberOptions number_o
     decltype(length) idx = 0;
 
     int digitsInGroup = 0;
-    int group_cnt = 0; // counts number of group chars
     int decpt_idx = -1;
     int last_separator_idx = -1;
     int start_of_digits_idx = -1;
@@ -3974,7 +3973,6 @@ bool QLocaleData::numberToCLocale(QStringView s, QLocale::NumberOptions number_o
                 }
 
                 last_separator_idx = idx;
-                ++group_cnt;
                 digitsInGroup = 0;
 
                 // don't add the group separator

src/corelib/text/qunicodetools.cpp

@@ -1369,7 +1369,6 @@ static qsizetype indic_nextSyllableBoundary(QChar::Script script, const char16_t
 static void indicAttributes(QChar::Script script, const char16_t *text, qsizetype from, qsizetype len, QCharAttributes *attributes)
 {
     qsizetype end = from + len;
-    const char16_t *uc = text + from;
     attributes += from;
     qsizetype i = 0;
     while (i < len) {
@@ -1381,7 +1380,6 @@ static void indicAttributes(QChar::Script script, const char16_t *text, qsizetyp
         i++;
         while (i < boundary) {
             attributes[i].graphemeBoundary = false;
-            ++uc;
             ++i;
         }
         assert(i == boundary);
@@ -1632,7 +1630,6 @@ finish:
 static void tibetanAttributes(QChar::Script script, const char16_t *text, qsizetype from, qsizetype len, QCharAttributes *attributes)
 {
     qsizetype end = from + len;
-    const char16_t *uc = text + from;
     qsizetype i = 0;
     Q_UNUSED(script);
     attributes += from;
@@ -1646,7 +1643,6 @@ static void tibetanAttributes(QChar::Script script, const char16_t *text, qsizet
         i++;
         while (i < boundary) {
             attributes[i].graphemeBoundary = false;
-            ++uc;
             ++i;
         }
         assert(i == boundary);
@@ -1847,7 +1843,6 @@ static qsizetype myanmar_nextSyllableBoundary(const char16_t *s, qsizetype start
 static void myanmarAttributes(QChar::Script script, const char16_t *text, qsizetype from, qsizetype len, QCharAttributes *attributes)
 {
     qsizetype end = from + len;
-    const char16_t *uc = text + from;
     qsizetype i = 0;
     Q_UNUSED(script);
     attributes += from;
@@ -1863,7 +1858,6 @@ static void myanmarAttributes(QChar::Script script, const char16_t *text, qsizet
     i++;
     while (i < boundary) {
         attributes[i].graphemeBoundary = false;
-        ++uc;
         ++i;
     }
     assert(i == boundary);
@@ -2183,7 +2177,6 @@ static qsizetype khmer_nextSyllableBoundary(const char16_t *s, qsizetype start,
 static void khmerAttributes(QChar::Script script, const char16_t *text, qsizetype from, qsizetype len, QCharAttributes *attributes)
 {
     qsizetype end = from + len;
-    const char16_t *uc = text + from;
     qsizetype i = 0;
     Q_UNUSED(script);
     attributes += from;
@@ -2197,7 +2190,6 @@ static void khmerAttributes(QChar::Script script, const char16_t *text, qsizetyp
     i++;
     while ( i < boundary ) {
         attributes[i].graphemeBoundary = false;
-        ++uc;
         ++i;
     }
     assert( i == boundary );

src/gui/kernel/qplatformcursor.cpp

@@ -619,7 +619,7 @@ void QPlatformCursorImage::set(const uchar *data, const uchar *mask,
     int p = 0;
     int d, m;
 
-    int x = -1, w = 0;
+    int x = -1;
 
     uchar *cursor_data = cursorImage.bits();
     qsizetype bpl = cursorImage.bytesPerLine();
@@ -641,15 +641,11 @@ void QPlatformCursorImage::set(const uchar *data, const uchar *mask,
                     x = j*8+b;
                 else if (x >= 0 && !m) {
                     x = -1;
-                    w = 0;
                 }
-                if (m)
-                    w++;
             }
         }
         if (x >= 0) {
             x = -1;
-            w = 0;
         }
         cursor_data += bpl;
     }

src/network/access/qnetworkdiskcache.cpp

@@ -536,7 +536,7 @@ qint64 QNetworkDiskCache::expire()
         }
     }
 
-    int removedFiles = 0;
+    [[maybe_unused]] int removedFiles = 0; // used under QNETWORKDISKCACHE_DEBUG
     qint64 goal = (maximumCacheSize() * 9) / 10;
     QMultiMap<QDateTime, QString>::const_iterator i = cacheItems.constBegin();
     while (i != cacheItems.constEnd()) {

src/platformsupport/input/evdevmouse/qevdevmousehandler.cpp

@@ -219,7 +219,6 @@ void QEvdevMouseHandler::readMouseData()
     int n = 0;
     bool posChanged = false, btnChanged = false;
     bool pendingMouseEvent = false;
-    int eventCompressCount = 0;
     forever {
         int result = QT_READ(m_fd, reinterpret_cast<char *>(buffer) + n, sizeof(buffer) - n);
 
@@ -326,7 +325,6 @@ void QEvdevMouseHandler::readMouseData()
                 posChanged = false;
                 if (m_compression) {
                     pendingMouseEvent = true;
-                    eventCompressCount++;
                 } else {
                     sendMouseEvent();
                 }