https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66848
--- Comment #9 from Jack Howarth <howarth.at.gcc at gmail dot com> --- Note that the earliest upstream boehm-gc release which builds and passes make check on 10.11 is gc-7.2.tar.gz from http://www.hboehm.info/gc/gc_source/. Diffing the current boehm-gc sources in gcc trunk suggests that the current FSF boehm-gc is based on 7.1 (for at least mach_dep.c, etc).