Testing the rebase of LLVM 20 (RHEL-80988, RHEL-81006) we found out that the compat libs for LLVM19 are causing segfaults on abidiff. I did some comparisons on the compat libs in llvm-20.1.2-1.el10 and the non-compat libs on llvm-19.1.7-2.el10 and there are some differences, being aarch64 where these are most notable.

Some of my findings:

• abidiff segfaults with liblldb libclang and libclang-cpp in all archs, but with aarch libs in particular, they cause OOM and the kernel kills up to the bash process running rpminspect/abidiff.
• The *.debug filesizes are HUGE in comparison with the non-compat llvm 19 libs. We're talking about 200-300MB in the non-compat vs 1.4-1.8GB in the compat debuginfo. The following shows the difference on liblldb, although libclang and libclang-cpp are also affected.

  # find . -name liblldb.so*.debug -exec du -h {} \;
  266M    ./before/aarch64/usr/lib/debug/usr/lib64/liblldb.so.19.1.7-19.1.7-2.el10.aarch64.debug
  268M    ./before/ppc64le/usr/lib/debug/usr/lib64/liblldb.so.19.1.7-19.1.7-2.el10.ppc64le.debug
  267M    ./before/x86_64/usr/lib/debug/usr/lib64/liblldb.so.19.1.7-19.1.7-2.el10.x86_64.debug
  312M    ./before/s390x/usr/lib/debug/usr/lib64/liblldb.so.19.1.7-19.1.7-2.el10.s390x.debug
  273M    ./after/aarch64/usr/lib/debug/usr/lib64/llvm20/lib/liblldb.so.20.1.2-20.1.2-1.el10.aarch64.debug
  1.4G    ./after/aarch64/usr/lib/debug/usr/lib64/liblldb.so.19.1.7-20.1.2-1.el10.aarch64.debug
  275M    ./after/ppc64le/usr/lib/debug/usr/lib64/llvm20/lib/liblldb.so.20.1.2-20.1.2-1.el10.ppc64le.debug
  1.4G    ./after/ppc64le/usr/lib/debug/usr/lib64/liblldb.so.19.1.7-20.1.2-1.el10.ppc64le.debug
  274M    ./after/x86_64/usr/lib/debug/usr/lib64/llvm20/lib/liblldb.so.20.1.2-20.1.2-1.el10.x86_64.debug
  1.4G    ./after/x86_64/usr/lib/debug/usr/lib64/liblldb.so.19.1.7-20.1.2-1.el10.x86_64.debug
  320M    ./after/s390x/usr/lib/debug/usr/lib64/llvm20/lib/liblldb.so.20.1.2-20.1.2-1.el10.s390x.debug
  1.8G    ./after/s390x/usr/lib/debug/usr/lib64/liblldb.so.19.1.7-20.1.2-1.el10.s390x.debug
  

• The debug-dump info difference is also massive. I ran readelf --debug-dump=info on aarch64 liblldb.so.19.1.7-19.1.7-2.el10.aarch64.debug for the non compat and liblldb.so.19.1.7-20.1.2-1.el10.aarch64.debug for the compat and dumped it to a file. The size of the non-compat dump is  2.7G, while the dump of the compat is 17G.

• Difference in symbols exported. I ran nm on each debuginfo and diffed them (e.g liblldb.so.19.1.7-19.1.7-2.el10.aarch64.debug vs liblldb.so.19.1.7-20.1.2-1.el10.aarch64.debug) and the difference is massive as well:

  # nm after/aarch64/usr/lib/debug/usr/lib64/liblldb.so.19.1.7-20.1.2-1.el10.aarch64.debug | wc -l
  516403
  # nm before/aarch64/usr/lib/debug/usr/lib64/liblldb.so.19.1.7-19.1.7-2.el10.aarch64.debug  | wc -l
  115218