That one is weird, because it's only triggered with -std=c99 (or -std=gnu99):
$ cat foo.c void foo () { typedef _Complex float __attribute__((mode(TC))) c128; c128 x, y; x *= y; } $ gcc -c foo.c $ gcc -c -std=c99 foo.c foo.c: In function foo: foo.c:6: internal compiler error: Segmentation fault -- Summary: ICE with complex __float128 Product: gcc Version: 4.3.0 Status: UNCONFIRMED Keywords: ice-on-valid-code Severity: normal Priority: P3 Component: target AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: fxcoudert at gcc dot gnu dot org GCC build triplet: x86_64-unknown-linux-gnu GCC host triplet: x86_64-unknown-linux-gnu GCC target triplet: x86_64-unknown-linux-gnu http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32191