Comment # 2 on bug 1124140 from Richard Biener

Yes, the last update unfortunately introduced the bug to Tumbleweed.  I've
updated GCC 8 in devel:gcc and will push it to Factory once builds completed.

Can you eventually check gcc8 from deve:gcc (once rebuilds finished) to see
whether it was indeed this issue?  You need to rebuild the GCC 8 generated
libraries.