https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65988
--- Comment #1 from Marc Glisse <glisse at gcc dot gnu.org> --- Yes, there is (was?) a bug in ISL where they are missing extern "C" in isl/val_gmp.h, which was hacked around in a buggy way in graphite-isl-ast-to-gimple.c by including that file inside extern "C". I think it should include system.h (or at least gmp.h) before doing that hack, to minimize the number of headers recursively affected.
