Values of std::vector not showing up in debug window

Hi,

I am sitting on a small C++ project using the standard library 
"vector"-container and can't see the entries in a "std::vector<long>" in 
the "Variables" window while debugging.
Even after I had installed the "DEBUG-INFO" packages (see below), they 
were missing.
I don't know, if I've done sth wrong or if this is a known issue.
As an alternative, it would be possible to use the "print" command in 
GDB, but it's a little too cumbersome.


Distro: openSuSE Leap 15.0
KDE: KDE Frameworks 5.45.0,
Qt 5.9.4 (built against 5.9.4)
KDevelop: 5.1.2

"DEBUG-INFO" packages:
gcc7-debugsource
libstdc++6-debuginfo
libstdc++6-32bit-debuginfo

I checked the release notes of later versions, but didn't find sth there 
either.

Thanks,
zb4bg