Hm, thank you again for your views.
Yes, it is mainly the customization of a package that makes rebuilding packages necessary. But in my situation, it is just the fact that the official lapack
package has a bug (missing soft links to liblapack.so ...) and other sw depending on it fails to build... It's why I have the lapack from slapt-src. I wrote about this problem earlier in the BUG section of the forum http://www.salixos.org/forum/viewtopic.php?f=15&t=2677
, but the broken package is still there without a mark of official remedy.
As for the ability of Slackware package management to deal with such situations - I absolutely don't see a relevance. This could simply be a job for the slapt-get program. Just to keep a note (in some logfile or so) which packages it installed and possibly upgrade only those and no else. But I can imagine that by simply setting the package in the EXCLUDE list may do the job well.
I could not find that smart hook in slapt-src. If someone knows, please share your knowledge
Happy New Year!