llvm-gcc-4.0/gcc/testsuite/gcc.dg/typedef-redecl.h

/* Redeclaration of typedef (invalid but accepted in system headers)
   causes ICE; PR 13656.  Test case by Richard Sandiford <rsandifo@redhat.com>,
   reduced from glibc.  */

#pragma GCC system_header
typedef int x;
typedef int x;