derefInvalidIterator
ftp://ftp.de.debian.org/debian/pool/main/r/r-cran-s2/r-cran-s2_1.1.7.orig.tar.gz
head s2/src/s2/s2loop_measures.cc:157:52: error: Dereference of an invalid iterator: vertices.end() [derefInvalidIterator]
head s2/src/s2/s2loop_measures.cc:175:41: error: Dereference of an invalid iterator: vertices.end() [derefInvalidIterator]