qt 6.11.1 - warning: defining ‘QChar’, which previously failed to be complete in a SFINAE context

[x0r00z]

gen_qvariant.cpp:36:10: fatal error: QVariantConstPointer: not found

[5k3105]

Is it just me or does qt6.11 break everything?

# github.com/mappu/miqt/qt6
In file included from /usr/include/qt6/QtCore/qstring.h:15,
                 from /usr/include/qt6/QtCore/qobject.h:12,
                 from /usr/include/qt6/QtCore/qabstracteventdispatcher.h:8,
                 from /usr/include/qt6/QtCore/qbasictimer.h:9,
                 from /usr/include/qt6/QtCore/qcoreevent.h:8,
                 from /usr/include/qt6/QtCore/QChildEvent:1,
                 from gen_qfile.cpp:2:
/usr/include/qt6/QtCore/qchar.h:48:31: warning: defining ‘QChar’, which previously failed to be complete in a SFINAE context [-Wsfinae-incomplete=]
   48 | class QT6_ONLY(Q_CORE_EXPORT) QChar {
      |                               ^~~~~
In file included from /usr/include/c++/16.1.1/unordered_map:44,
                 from /usr/include/c++/16.1.1/functional:80,
                 from /usr/include/qt6/QtCore/qcomparehelpers.h:29,
                 from /usr/include/qt6/QtCore/qcompare.h:661,
                 from /usr/include/qt6/QtCore/qnamespace.h:14,
                 from /usr/include/qt6/QtCore/qbytearray.h:10,
                 from /usr/include/qt6/QtCore/QByteArray:1,
                 from gen_qfile.cpp:1:
/usr/include/c++/16.1.1/bits/range_access.h:325:24: note: here.  Use ‘-Wsfinae-incomplete=2’ for a diagnostic at that point
  325 |     -> decltype(__cont.data())
      |                 ~~~~~~~^~~~

[mappu]

Are you using the latest @master version of Miqt? The initial Qt 6.11 support was done in #322 but I haven't tagged a new point release yet.

Also a duplicate of #325 .

[mappu]

I made a docker container specifically for Qt 6.11.1 point release and saw no further problems on master.

[mappu]

I've pushed a new v0.14.0 release. Please update miqt, and let me know if you still have any problems,

[5k3105]

Yes, same problem but just when its first installed. After that a project will build without complaints.
Here are some of the errors:

# github.com/mappu/miqt/qt6
In file included from /usr/include/qt6/QtCore/qstring.h:15,
                 from /usr/include/qt6/QtCore/qhashfunctions.h:10,
                 from /usr/include/qt6/QtCore/qfloat16.h:11,
                 from /usr/include/qt6/QtCore/qendian.h:13,
                 from /usr/include/qt6/QtGui/qfont.h:8,
                 from /usr/include/qt6/QtGui/QFont:1,
                 from gen_qfontdatabase.cpp:2:
/usr/include/qt6/QtCore/qchar.h:48:31: warning: defining ‘QChar’, which previously failed to be complete in a SFINAE context [-Wsfinae-incomplete=]
   48 | class QT6_ONLY(Q_CORE_EXPORT) QChar {
      |                               ^~~~~
In file included from /usr/include/c++/16.1.1/unordered_map:44,
                 from /usr/include/c++/16.1.1/functional:80,
                 from /usr/include/qt6/QtCore/qcomparehelpers.h:29,
                 from /usr/include/qt6/QtCore/qcompare.h:661,
                 from /usr/include/qt6/QtCore/qnamespace.h:14,
                 from /usr/include/qt6/QtCore/qbytearray.h:10,
                 from /usr/include/qt6/QtCore/QByteArray:1,
                 from gen_qfontdatabase.cpp:1:
/usr/include/c++/16.1.1/bits/range_access.h:325:24: note: here.  Use ‘-Wsfinae-incomplete=2’ for a diagnostic at that point
  325 |     -> decltype(__cont.data())
      |                 ~~~~~~~^~~~
# github.com/mappu/miqt/qt6
In file included from /usr/include/qt6/QtCore/qdatastream.h:9,
                 from /usr/include/qt6/QtCore/qmetatype.h:14,
                 from /usr/include/qt6/QtCore/qdeadlinetimer.h:8,
                 from /usr/include/qt6/QtCore/qmutex.h:10,
                 from /usr/include/qt6/QtCore/qfutureinterface.h:8,
                 from /usr/include/qt6/QtCore/QFutureInterfaceBase:1,
                 from gen_qfutureinterface.cpp:1:
/usr/include/qt6/QtCore/qchar.h:48:31: warning: defining ‘QChar’, which previously failed to be complete in a SFINAE context [-Wsfinae-incomplete=]
   48 | class QT6_ONLY(Q_CORE_EXPORT) QChar {
      |                               ^~~~~
In file included from /usr/include/c++/16.1.1/unordered_map:44,
                 from /usr/include/c++/16.1.1/functional:80,
                 from /usr/include/qt6/QtCore/qcomparehelpers.h:29,
                 from /usr/include/qt6/QtCore/qcompare.h:661,
                 from /usr/include/qt6/QtCore/qnamespace.h:14,
                 from /usr/include/qt6/QtCore/qbytearray.h:10,
                 from /usr/include/qt6/QtCore/qmetatype.h:12:
/usr/include/c++/16.1.1/bits/range_access.h:325:24: note: here.  Use ‘-Wsfinae-incomplete=2’ for a diagnostic at that point
  325 |     -> decltype(__cont.data())
      |                 ~~~~~~~^~~~
# github.com/mappu/miqt/qt6
In file included from /usr/include/qt6/QtCore/qstring.h:15,
                 from /usr/include/qt6/QtCore/qobject.h:12,
                 from /usr/include/qt6/QtCore/qabstracteventdispatcher.h:8,
                 from /usr/include/qt6/QtCore/qbasictimer.h:9,
                 from /usr/include/qt6/QtCore/qcoreevent.h:8,
                 from /usr/include/qt6/QtCore/QChildEvent:1,
                 from gen_qimageiohandler.cpp:2:
/usr/include/qt6/QtCore/qchar.h:48:31: warning: defining ‘QChar’, which previously failed to be complete in a SFINAE context [-Wsfinae-incomplete=]
   48 | class QT6_ONLY(Q_CORE_EXPORT) QChar {
      |                               ^~~~~
In file included from /usr/include/c++/16.1.1/unordered_map:44,
                 from /usr/include/c++/16.1.1/functional:80,
                 from /usr/include/qt6/QtCore/qcomparehelpers.h:29,
                 from /usr/include/qt6/QtCore/qcompare.h:661,
                 from /usr/include/qt6/QtCore/qnamespace.h:14,
                 from /usr/include/qt6/QtCore/qbytearray.h:10,
                 from /usr/include/qt6/QtCore/QByteArray:1,
                 from gen_qimageiohandler.cpp:1:
/usr/include/c++/16.1.1/bits/range_access.h:325:24: note: here.  Use ‘-Wsfinae-incomplete=2’ for a diagnostic at that point
  325 |     -> decltype(__cont.data())
      |                 ~~~~~~~^~~~
# github.com/mappu/miqt/qt6
In file included from /usr/include/qt6/QtCore/qstring.h:15,
                 from /usr/include/qt6/QtCore/qobject.h:12,
                 from /usr/include/qt6/QtCore/qiodevice.h:11,
                 from /usr/include/qt6/QtCore/QIODevice:1,
                 from gen_qimagewriter.cpp:2:
/usr/include/qt6/QtCore/qchar.h:48:31: warning: defining ‘QChar’, which previously failed to be complete in a SFINAE context [-Wsfinae-incomplete=]
   48 | class QT6_ONLY(Q_CORE_EXPORT) QChar {
      |                               ^~~~~
In file included from /usr/include/c++/16.1.1/unordered_map:44,
                 from /usr/include/c++/16.1.1/functional:80,
                 from /usr/include/qt6/QtCore/qcomparehelpers.h:29,
                 from /usr/include/qt6/QtCore/qcompare.h:661,
                 from /usr/include/qt6/QtCore/qnamespace.h:14,
                 from /usr/include/qt6/QtCore/qbytearray.h:10,
                 from /usr/include/qt6/QtCore/QByteArray:1,
                 from gen_qimagewriter.cpp:1:
/usr/include/c++/16.1.1/bits/range_access.h:325:24: note: here.  Use ‘-Wsfinae-incomplete=2’ for a diagnostic at that point
  325 |     -> decltype(__cont.data())
      |                 ~~~~~~~^~~~
# github.com/mappu/miqt/qt6
In file included from /usr/include/qt6/QtCore/qstring.h:15,
                 from /usr/include/qt6/QtCore/qhashfunctions.h:10,
                 from /usr/include/qt6/QtCore/qlist.h:12,
                 from /usr/include/qt6/QtCore/qstringlist.h:6,
                 from /usr/include/qt6/QtGui/qcolor.h:10,
                 from /usr/include/qt6/QtGui/QColor:1,
                 from gen_qimagereader.cpp:2:
/usr/include/qt6/QtCore/qchar.h:48:31: warning: defining ‘QChar’, which previously failed to be complete in a SFINAE context [-Wsfinae-incomplete=]
   48 | class QT6_ONLY(Q_CORE_EXPORT) QChar {
      |                               ^~~~~
In file included from /usr/include/c++/16.1.1/unordered_map:44,
                 from /usr/include/c++/16.1.1/functional:80,
                 from /usr/include/qt6/QtCore/qcomparehelpers.h:29,
                 from /usr/include/qt6/QtCore/qcompare.h:661,
                 from /usr/include/qt6/QtCore/qnamespace.h:14,
                 from /usr/include/qt6/QtCore/qbytearray.h:10,
                 from /usr/include/qt6/QtCore/QByteArray:1,
                 from gen_qimagereader.cpp:1:
/usr/include/c++/16.1.1/bits/range_access.h:325:24: note: here.  Use ‘-Wsfinae-incomplete=2’ for a diagnostic at that point
  325 |     -> decltype(__cont.data())
      |                 ~~~~~~~^~~~

[mappu]

@5k3105 What OS/distro version is this?

Appearing only once makes sense: this is only a warning, the compilation succeeded, and after that GCC is not so involved in the individual translation units since they're cached in GOCACHE.

GCC 16.1.1 is quite new, maybe this is a GCC issue where some warnings became stricter.

I think the fix for SFINAE would be to have Miqt load the full <QChar> header earlier in the TU. It should be an easy fix if the issue can be reproduced.