Thomas,
Martin,
there is no need to revert the patch. I have adopted the test case for s390 and it
now stops at main, which is identical to x86.
The --symfs option was not used, however the debug file selected for dwarf examination
was different. With you patch it changed from /usr/lib64/libc.so (old) to
/usr/lib/debug/lib64/libc-2.26.so.debug (new)
and I think that this file has not all the info (at least on s390).