Compiling on macOS 14.6.1 fails with:

hexwriter.cpp:50:26: error: calling 'GetHexLine' with incomplete return type 'QString'
outStream << GetHexLine(temp,2,0,SEGMENT_RECORD) << ENDL;
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./hexwriter.h:12:13: note: 'GetHexLine' declared here
QString GetHexLine(uchar data, uchar size, ushort address ,uchar recordtype);
^
/opt/homebrew/lib/QtCore.framework/Headers/qcontainerfwd.h:36:7: note: forward declaration of 'QString'
class QString;
^
hexwriter.cpp:52:22: error: calling 'GetHexLine' with incomplete return type 'QString'
outStream << GetHexLine(reinterpret_cast<uchar>(&data.data()[(segment-1)*0x10000+address]),16,address,DATA_RECORD) << ENDL;
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./hexwriter.h:12:13: note: 'GetHexLine' declared here
QString GetHexLine(uchar data, uchar size, ushort address ,uchar recordtype);
^
/opt/homebrew/lib/QtCore.framework/Headers/qcontainerfwd.h:36:7: note: forward declaration of 'QString'
class QString;
^
hexwriter.cpp:56:17: error: calling 'GetHexLine' with incomplete return type 'QString'
outStream << GetHexLine(reinterpret_cast<uchar>(&data.data()[(segment-1)*0x10000+address]), static_cast(size/2),address,DATA_RECORD) << ENDL;
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./hexwriter.h:12:13: note: 'GetHexLine' declared here
QString GetHexLine(uchar data, uchar size, ushort address ,uchar recordtype);
^
/opt/homebrew/lib/QtCore.framework/Headers/qcontainerfwd.h:36:7: note: forward declaration of 'QString'
class QString;
^
hexwriter.cpp:59:17: error: calling 'GetHexLine' with incomplete return type 'QString'
outStream << GetHexLine(reinterpret_cast<uchar>(&data.data()[(segment-1)*0x10000+address]),static_cast(size),address,DATA_RECORD) << ENDL;
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./hexwriter.h:12:13: note: 'GetHexLine' declared here
QString GetHexLine(uchar *data, uchar size, ushort address ,uchar recordtype);
^
/opt/homebrew/lib/QtCore.framework/Headers/qcontainerfwd.h:36:7: note: forward declaration of 'QString'
class QString;
^
hexwriter.cpp:60:17: error: calling 'GetHexLine' with incomplete return type 'QString'
outStream << GetHexLine(nullptr,0,0,EOF_RECORD) << ENDL;
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./hexwriter.h:12:13: note: 'GetHexLine' declared here
QString GetHexLine(uchar *data, uchar size, ushort address ,uchar recordtype);
^
/opt/homebrew/lib/QtCore.framework/Headers/qcontainerfwd.h:36:7: note: forward declaration of 'QString'
class QString;
^
hexwriter.cpp:64:20: error: incomplete result type 'QString' in function definition
QString HexWriter::GetHexLine(uchar *data, uchar size, ushort address, uchar recordtype)
^
/opt/homebrew/lib/QtCore.framework/Headers/qcontainerfwd.h:36:7: note: forward declaration of 'QString'
class QString;
^
hexwriter.cpp:66:16: error: 'QString' is an incomplete type
QString s=(QString(":%1%2%3").arg(size & 0xff, 2, 16, QChar('0')).arg(address, 4, 16, QChar('0')).arg(recordtype, 2, 16, QChar('0')).toUpper()).toLocal8Bit();
^
/opt/homebrew/lib/QtCore.framework/Headers/qcontainerfwd.h:36:7: note: forward declaration of 'QString'
class QString;
^
hexwriter.cpp:66:34: error: member access into incomplete type 'QString'
QString s=(QString(":%1%2%3").arg(size & 0xff, 2, 16, QChar('0')).arg(address, 4, 16, QChar('0')).arg(recordtype, 2, 16, QChar('0')).toUpper()).toLocal8Bit();
^
/opt/homebrew/lib/QtCore.framework/Headers/qcontainerfwd.h:36:7: note: forward declaration of 'QString'
class QString;
^
hexwriter.cpp:66:13: error: variable has incomplete type 'QString'
QString s=(QString(":%1%2%3").arg(size & 0xff, 2, 16, QChar('0')).arg(address, 4, 16, QChar('0')).arg(recordtype, 2, 16, QChar('0')).toUpper()).toLocal8Bit();
^
/opt/homebrew/lib/QtCore.framework/Headers/qcontainerfwd.h:36:7: note: forward declaration of 'QString'
class QString;
^
hexwriter.cpp:75:22: error: 'QString' is an incomplete type
s.append(QString("%1").arg(data[i], 2, 16, QChar('0')).toUpper());
^
/opt/homebrew/lib/QtCore.framework/Headers/qcontainerfwd.h:36:7: note: forward declaration of 'QString'
class QString;
^
hexwriter.cpp:75:35: error: member access into incomplete type 'QString'
s.append(QString("%1").arg(data[i], 2, 16, QChar('0')).toUpper());
^
/opt/homebrew/lib/QtCore.framework/Headers/qcontainerfwd.h:36:7: note: forward declaration of 'QString'
class QString;
^
hexwriter.cpp:80:14: error: 'QString' is an incomplete type
s.append(QString("%1").arg(cs, 2, 16, QChar('0')).toUpper());
^
/opt/homebrew/lib/QtCore.framework/Headers/qcontainerfwd.h:36:7: note: forward declaration of 'QString'
class QString;
^
hexwriter.cpp:80:27: error: member access into incomplete type 'QString'
s.append(QString("%1").arg(cs, 2, 16, QChar('0')).toUpper());
^
/opt/homebrew/lib/QtCore.framework/Headers/qcontainerfwd.h:36:7: note: forward declaration of 'QString'
class QString;
^
13 errors generated.
make: *** [hexwriter.o] Error 1