It looks like D_GLIBCXX_ASSERTIONS=ON activated on some Linux versions creates too zealous tests at run time.
This patch just calculate the same pointer value using a slightly different formula.
Fix also a hard-to-understand comment
Fixes: lp:1770414
https://bugs.launchpad.net/kicad/+bug/1770414
Make refilling zones during DRC optional to prevent the board from being
changed by changes in the polygon filling. Default to off to prevent
changes by default.
Fixes lp:1721547
https://bugs.launchpad.net/kicad/+bug/1721547