Compiling with -Wconversion gives lots and lots of warning messages in the Qt headers

[Sjors Gielen]

I noticed (and I think this is the case with many, many more versions of Qt) that when compiling with -Wconversion, the headers give lots and lots of warnings. For example, when compiling a program containing only "#include <QChar>" using <g++ -I/usr/include/qt4/QtCore -I/usr/include/qt4 -c test.cpp> no warnings appear, but when adding -Wconversion, this is the output:

In file included from /usr/include/qt4/QtCore/qchar.h:45,
                 from /usr/include/qt4/QtCore/QChar:1,
                 from test.cpp:1:
/usr/include/qt4/QtCore/qglobal.h: In function ‘qint64 qRound64(qreal)’:
/usr/include/qt4/QtCore/qglobal.h:1027: warning: conversion to ‘qreal’ from ‘qint64’ may alter its value
In file included from /usr/include/qt4/QtCore/QChar:1,
                 from test.cpp:1:
/usr/include/qt4/QtCore/qchar.h: In static member function ‘static ushort QChar::highSurrogate(uint)’:
/usr/include/qt4/QtCore/qchar.h:295: warning: conversion to ‘ushort’ from ‘unsigned int’ mayalter its value
/usr/include/qt4/QtCore/qchar.h: In static member function ‘static ushort QChar::lowSurrogate(uint)’:
/usr/include/qt4/QtCore/qchar.h:298: warning: conversion to ‘ushort’ from ‘unsigned int’ mayalter its value
/usr/include/qt4/QtCore/qchar.h: In constructor ‘QChar::QChar(uchar, uchar)’:
/usr/include/qt4/QtCore/qchar.h:369: warning: conversion to ‘ushort’ from ‘int’ may alter its value
/usr/include/qt4/QtCore/qchar.h: In member function ‘void QChar::setCell(uchar)’:
/usr/include/qt4/QtCore/qchar.h:377: warning: conversion to ‘ushort’ from ‘int’ may alter its value
/usr/include/qt4/QtCore/qchar.h: In member function ‘void QChar::setRow(uchar)’:
/usr/include/qt4/QtCore/qchar.h:379: warning: conversion to ‘ushort’ from ‘int’ may alter its value

These are unmodified headers. Should I just not compile with -Wconversion, i.e. is this a wontfix bug? I understand that *really* fixing it makes the headers a lot more ugly and complicated, yet it's an ugly bug.

[Sjors Gielen (sgielen)]

Seems like for example SuSE doesn't have this bug because it does not apply things like -Wconversion to files in /usr/include, or something like that. Would that be possible for Ubuntu? To which package do I file a bug?

[Jonathan Thomas (echidnaman)]

Yeah, this is something that we're not going to fix.
I'd suggest taking it up with Qt Software.