Files that include <sys/reent.h> on i686-pc-cygwin can cause GCC 4 (10-26-04) to bomb out due to a segfault in the compiler itself. I don't have a backtrace (I don't know how to get one if the ICE occurs during the bootstrap process itself, which it does).
-- Summary: <sys/reent.h> causes segfault ICE in GCC 4 Product: gcc Version: 4.0.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: bsdfan3 at users dot sourceforge dot net CC: gcc-bugs at gcc dot gnu dot org GCC build triplet: i686-pc-cygwin GCC host triplet: i686-pc-cygwin GCC target triplet: i686-pc-cygwin http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19171