https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63543
Manuel López-Ibáñez <manu at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |diagnostic --- Comment #3 from Manuel López-Ibáñez <manu at gcc dot gnu.org> --- The C++ FE prints: test.c:6:12: error: invalid use of incomplete type ‘struct undefined’ int x = f->a; ^ test.c:2:8: note: forward declaration of ‘struct undefined’ struct undefined; ^ but it also prints it three times.