Created attachment 150105 [details]
Add typedef qsizetype for older Qt

SUMMARY

digiKam 7.7.0 FTBFS with Qt 5.9 due introducing use of code requiring a newer Qt version.

STEPS TO REPRODUCE
1. Download digiKam 7.7.0 source and extract.
2. Attempt building source using pbuilder in a clean chroot with all appropriate build dependencies.
3. Build fails with errors as described below.

OBSERVED RESULT

The build fails with errors related to use of qsizetype (requires Qt >= 5.10) in this new file:
core/libs/threadimageio/engine/dmemoryinfo.cpp

EXPECTED RESULT

That the build succeeds with Qt 5.9 which is still listed as a sufficient minimum Qt build dependency (Mainpage.dox) for digiKam 7.x versions (qt5-maintenance branch).

SOFTWARE/OS VERSIONS
Windows: n/a
macOS: n/a
Linux/KDE Plasma: Ubuntu 18.04 / KDE 5.44
(available in About System)
KDE Plasma Version: 5.44
KDE Frameworks Version: 5.44
Qt Version: 5.9.5

ADDITIONAL INFORMATION

Adding the following typedef (see attached patch) -- per Qt 5.10 source in src/corelib/global/qglobal.h -- to core/libs/threadimageio/engine/dmemoryinfo.h fixes the build with Qt 5.9.x (ie. such as Qt 5.9.5 in Ubuntu 18.04 Bionic LTS):

using qsizetype = QIntegerForSizeof<std::size_t>::Signed;

Here is the relevant Qt documentation:

https://doc.qt.io/archives/qt-5.11/qtglobal.html#qsizetype-typedef

Note that although qsizetype was introduced in Qt 5.10 it was not included in the Qt 5.10 documentation page, hence linking to Qt 5.11 documentation here.